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Title: Astronomy for Amateurs
Author: Flammarion, Camille, 1842-1925
Language: English
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[Illustration: Paul Renaud.
CONTEMPLATION]
ASTRONOMY FOR
AMATEURS
BY
CAMILLE FLAMMARION
AUTHOR OF POPULAR ASTRONOMY
_AUTHORIZED TRANSLATION BY_
FRANCES A. WELBY
_ILLUSTRATED_
[Illustration]
NEW YORK AND LONDON
D. APPLETON AND COMPANY
1910
COPYRIGHT, 1904, BY
D. APPLETON AND COMPANY
_Published October, 1904_
TO
MADAME C.R. CAVARÉ
ORIGINAL MEMBER OF THE ASTRONOMICAL SOCIETY OF FRANCE
CHÂTEAU DE MAUPERTHUIS
MADAME: I have dedicated none of my works, save Stella--offered to the
liberal-minded, the free and generous friend of progress, and patron of
the sciences, James Gordon Bennett, editor of the New York Herald. In
this volume, Madame, I make another exception, and ask your permission
to offer it to the first woman who consented to be enrolled in the list
of members of the Astronomical Society of France, as foundress of this
splendid work, from the very beginning of our vast association (1887);
and who also desired to take part in the permanent organization of the
Observatory at Juvisy, a task of private enterprise, emancipated from
administrative routine. An Astronomy for Women[1] can not be better
placed than upon the table of a lady whose erudition is equal to her
virtues, and who has consecrated her long career to the pursuit and
service of the Beautiful, the Good, and the True.
CAMILLE FLAMMARION.
OBSERVATORY OF JUVISY, _November, 1903_.
CONTENTS
CHAPTER PAGE
INTRODUCTION 1
I. THE CONTEMPLATION OF THE HEAVENS 10
II. THE CONSTELLATIONS 28
III. THE STARS, SUNS OF THE INFINITE. A JOURNEY
THROUGH SPACE 56
IV. OUR STAR THE SUN 88
V. THE PLANETS. A. MERCURY, VENUS, THE
EARTH, MARS 113
VI. THE PLANETS. B. JUPITER, SATURN, URANUS,
NEPTUNE 146
VII. THE COMETS 172
VIII. THE EARTH 205
IX. THE MOON 232
X. THE ECLIPSES 259
XI. ON METHODS. HOW CELESTIAL DISTANCES
ARE DETERMINED, AND HOW THE SUN IS
WEIGHED 287
XII. LIFE, UNIVERSAL AND ETERNAL 317
INDEX 341
LIST OF ILLUSTRATIONS
Contemplation _Frontispiece_
From a painting by Paul Renaud
FIG. PAGE
1. The great Book of the Heavens is open to all eyes 15
2. The earth in space. June solstice, midday 20
3. The Great Bear (or Dipper) and the Pole Star 34
4. To find the Pole Star 35
5. To find Cassiopeia 37
6. To find Pegasus and Andromeda 37
7. Perseus, the Pleiades, Capella 38
8. To find Arcturus, the Herdsman, and the Northern Crown 40
9. The Swan, Vega, the Eagle 41
10. The Constellations of the Zodiac: summer and autumn;
Capricorn, Archer, Scorpion, Balance, Virgin, Lion 46
11. The Constellations of the Zodiac: winter and spring;
Crab, Twins, Bull, Ram, Fishes, Water-Carrier 47
12. Orion and his celestial companions 48
13. Winter Constellations 51
14. Spring Constellations 52
15. Summer Constellations 53
16. Autumn Constellations 54
17. The double star Mizar 69
18. Triple star [xi] in Cancer 72
19. Quadruple star [epsilon] of the Lyre 73
20. Sextuple star [theta] in the Nebula of Orion 74
21. The Star-Cluster in Hercules 79
22. The Star-Cluster in the Centaur 80
23. The Nebula in Andromeda 81
24. Nebula in the Greyhounds 82
25. The Pleiades 83
26. Occultation of the Pleiades by the Moon 85
27. Stellar dial of the double star [gamma] of the Virgin 86
28. Comparative sizes of the Sun and Earth 93
29. Direct photograph of the Sun 96
30. Telescopic aspect of a Sun-Spot 97
31. Rose-colored solar flames 228,000 kilometers (141,500
miles) in height, _i.e._, 18 times the diameter of the
Earth 103
32. Orbits of the four Planets nearest to the Sun 115
33. Orbits of the four Planets farthest from the Sun 116
34. Mercury near quadrature 117
35. The Earth viewed from Mercury 119
36. The Evening Star 123
37. Successive phases of Venus 124
38. Venus at greatest brilliancy 126
39. The Earth viewed from Venus 130
40. Diminution of the polar snows of Mars during the
summer 136
41. Telescopic aspect of the planet Mars (Feb., 1901) 137
42. Telescopic aspect of the planet Mars (Feb., 1901) 138
43. Chart of Mars 140
44. The Earth viewed from Mars 144
45. Telescopic aspect of Jupiter 150
46. Jupiter and his four principal satellites 155
47. Saturn 159
48. Varying perspective of Saturn's Rings, as seen from
the Earth 161
49. The Great Comet of 1858 174
50. What our Ancestors saw in a Comet 177
After Ambroise Paré (1858)
51. Prodigies seen in the Heavens by our Forefathers 178
52. The orbit of a Periodic Comet 182
53. The tails of Comets are opposed to the Sun 185
54. A Meteor 191
55. Shooting Stars of November 12, 1799 196
From a contemporary drawing
56. Fire-Ball seen from the Observatory at Juvisy, August
10, 1899 199
57. Explosion of a Fire-Ball above Madrid, February 10,
1896 200
58. Raphael's Fire-Ball (_The Madonna of Foligno_) 202
59. A Uranolith 203
60. Motion of the Earth round the Sun 222
61. Inclination of the Earth 224
62. The divisions of the globe. Longitudes and latitudes 226
63. To find the long and short months 230
64. The Full Moon slowly rises 234
65. The Moon viewed with the unaided eye 236
66. The Man's head in the Moon 237
67. Woman's head in the Moon 238
68. The kiss in the Moon 239
69. Photograph of the Moon 240
70. The Moon's Phases 241
71. Map of the Moon 247
72. The Lunar Apennines 251
73. Flammarion's Lunar Ring 253
74. Lunar landscape with the Earth in the sky 254
75. Battle between the Medes and Lydians arrested by an
Eclipse of the Sun 266
76. Eclipse of the Moon at Laos (February 27, 1877) 269
77. The path of the Eclipse of May 28, 1900 273
78. Total eclipse of the Sun, May 28, 1900, as observed
from Elche (Spain) 281
79. The Eclipse of May 28, 1900, as photographed by
King Alfonso XIII, at Madrid 285
80. Measurement of Angles 289
81. Division of the Circumference into 360 degrees 291
82. Measurement of the distance of the Moon 292
83. Measurement of the distance of the Sun 297
84. Small apparent ellipses described by the stars as a
result of the annual displacement of the Earth 306
INTRODUCTION
The Science of Astronomy is sublime and beautiful. Noble, elevating,
consoling, divine, it gives us wings, and bears us through Infinitude.
In these ethereal regions all is pure, luminous, and splendid. Dreams of
the Ideal, even of the Inaccessible, weave their subtle spells upon us.
The imagination soars aloft, and aspires to the sources of Eternal
Beauty.
What greater delight can be conceived, on a fine spring evening, at the
hour when the crescent moon is shining in the West amid the last glimmer
of twilight, than the contemplation of that grand and silent spectacle
of the stars stepping forth in sequence in the vast Heavens? All sounds
of life die out upon the earth, the last notes of the sleepy birds have
sunk away, the Angelus of the church hard by has rung the close of day.
But if life is arrested around us, we may seek it in the Heavens. These
incandescing orbs are so many points of interrogation suspended above
our heads in the inaccessible depths of space.... Gradually they
multiply. There is Venus, the white star of the shepherd. There Mars,
the little celestial world so near our own. There the giant Jupiter.
The seven stars of the Great Bear seem to point out the pole, while they
slowly revolve around it.... What is this nebulous light that blanches
the darkness of the heavens, and traverses the constellations like a
celestial path? It is the Galaxy, the Milky Way, composed of millions on
millions of suns!... The darkness is profound, the abyss immense....
See! Yonder a shooting star glides silently across the sky, and
disappears!...
Who can remain insensible to this magic spectacle of the starry Heavens?
Where is the mind that is not attracted to these enigmas? The
intelligence of the amateur, the feminine, no less than the more
material and prosaic masculine mind, is well adapted to the
consideration of astronomical problems. Women, indeed, are naturally
predisposed to these contemplative studies. And the part they are called
to play in the education of our children is so vast, and so important,
that the elements of Astronomy might well be taught by the young mother
herself to the budding minds that are curious about every issue--whose
first impressions are so keen and so enduring.
Throughout the ages women have occupied themselves successfully with
Astronomy, not merely in its contemplative and descriptive, but also in
its mathematical aspects. Of such, the most illustrious was the
beautiful and learned Hypatia of Alexandria, born in the year 375 of our
era, public lecturer on geometry, algebra, and astronomy, and author of
three works of great importance. Then, in that age of ignorance and
fanaticism, she fell a victim to human stupidity and malice, was dragged
from her chariot while crossing the Cathedral Square, in March, 415,
stripped of her garments, stoned to death, and burned as a dishonored
witch!
Among the women inspired with a passion for the Heavens may be cited St.
Catherine of Alexandria, admired for her learning, her beauty and her
virtue. She was martyred in the reign of Maximinus Daza, about the year
312, and has given her name to one of the lunar rings.
Another celebrated female mathematician was Madame Hortense Lepaute,
born in 1723, who collaborated with Clairaut in the immense calculations
by which he predicted the return of Halley's Comet. "Madame Lepaute,"
wrote Lalande, "gave us such immense assistance that, without her, we
should never have ventured to undertake this enormous labor, in which it
was necessary to calculate for every degree, and for a hundred and fifty
years, the distances and forces of the planets acting by their
attraction on the comet. During more than six months, we calculated from
morning to night, sometimes even at table, and as the result of this
forced labor I contracted an illness that has changed my constitution
for life; but it was important to publish the result before the arrival
of the comet."
This extract will suffice for the appreciation of the scientific ardor
of Madame Lepaute. We are indebted to her for some considerable works.
Her husband was clock-maker to the King. "To her intellectual talents,"
says one of her biographers, "were joined all the qualities of the
heart. She was charming to a degree, with an elegant figure, a dainty
foot, and such a beautiful hand that Voiriot, the King's painter, who
had made a portrait of her, asked permission to copy it, in order to
preserve a model of the best in Nature." And then we are told that
learned women can not be good-looking!...
The Marquise du Châtelet was no less renowned. She was predestined to
her career, if the following anecdote be credible. Gabrielle-Émilie de
Breteuil, born in 1706 (who, in 1725, was to marry the Marquis du
Châtelet, becoming, in 1733, the most celebrated friend of Voltaire),
was four or five years old when she was given an old compass, dressed up
as a doll, for a plaything. After examining this object for some time,
the child began angrily and impatiently to strip off the silly draperies
the toy was wrapped in, and after turning it over several times in her
little hands, she divined its uses, and traced a circle with it on a
sheet of paper. To her, among other things, we owe a precious, and
indeed the only French, translation of Newton's great work on universal
gravitation, the famous Principia, and she was, with Voltaire, an
eloquent propagator of the theory of attraction, rejected at that time
by the Académie des Sciences.
Numbers of other women astronomers might be cited, all showing how
accessible this highly abstract science is to the feminine intellect.
President des Brosses, in his charming Voyage en Italie, tells of the
visit he paid in Milan to the young Italian, Marie Agnesi, who delivered
harangues in Latin, and was acquainted with seven languages, and for
whom mathematics held no secrets. She was devoted to algebra and
geometry, which, she said, "are the only provinces of thought wherein
peace reigns." Madame de Charrière expressed herself in an aphorism of
the same order: "An hour or two of mathematics sets my mind at liberty,
and puts me in good spirits; I feel that I can eat and sleep better when
I have seen obvious and indisputable truths. This consoles me for the
obscurities of religion and metaphysics, or rather makes me forget them;
I am thankful there is something positive in this world." And did not
Madame de Blocqueville, last surviving daughter of Marshal Davout, who
died in 1892, exclaim in her turn: "Astronomy, science of sciences! by
which I am attracted, and terrified, and which I adore! By it my soul is
detached from the things of this world, for it draws me to those unknown
spheres that evoked from Newton the triumphant cry: '_Coeli enarrant
gloriam Dei!_'"
Nor must we omit Miss Caroline Herschel, sister of the greatest observer
of the Heavens, the grandest discoverer of the stars, that has ever
lived. Astronomy gave her a long career; she discovered no less than
seven comets herself, and her patient labors preserved her to the age of
ninety-eight.--And Mrs. Somerville, to whom we owe the English
translation of Laplace's Mécanique céleste, of whom Humboldt said, "In
pure mathematics, Mrs. Somerville is absolutely superior." Like Caroline
Herschel, she was almost a centenarian, appearing always much younger
than her years: she died at Naples, in 1872, at the age of
ninety-two.--So, too, the Russian Sophie Kovalevsky, descendant of
Mathias Corvinus, King of Hungary, who, an accomplished mathematician at
sixteen, married at eighteen, in order to follow the curriculum at the
University (then forbidden to unmarried women); arranging with her young
husband to live as brother and sister until their studies should be
completed. In 1888 the Prix Bordin of the Institut was conferred on
her.--And Maria Mitchell of the United States, for whom Le Verrier gave
a _fête_ at the Observatory of Paris, and who was exceptionally
authorized by Pope Pius IX to visit the Observatory of the Roman
College, at that time an ecclesiastical establishment, closed to
women.--And Madame Scarpellini, the Roman astronomer, renowned for her
works on shooting stars, whom the author had the honor of visiting, in
company with Father Secchi, Director of the Observatory mentioned above.
At the present time, Astronomy is proud to reckon among its most famous
workers Miss Agnes Clerke, the learned Irishwoman, to whom we owe,
_inter alia_, an excellent History of Astronomy in the Nineteenth
Century;--Mrs. Isaac Roberts, who, under the familiar name of Miss
Klumpke, sat on the Council of the Astronomical Society of France, and
is D. Sc. of the Faculty of Paris and head of the Bureau for measuring
star photographs at the Observatory of Paris (an American who became
English by her marriage with the astronomer Roberts, but is not
forgotten in France);--Mrs. Fleming, one of the astronomers of the
Observatory at Harvard College, U.S.A., to whom we owe the discovery of
a great number of variable stars by the examination of photographic
records, and by spectral photography;--Lady Huggins, who in England is
the learned collaborator of her illustrious husband;--and many others.
* * * * *
The following chapters, which aim at summing up the essentials of
Astronomy in twelve lessons for amateurs, will not make astronomers or
mathematicians of my readers--much less prigs or pedants. They are
designed to show the constitution of the Universe, in its grandeur and
its beauty, so that, inhabiting this world, we may know where we are
living, may realize our position in the Cosmos, appreciate Creation as
it is, and enjoy it to better advantage. This sun by which we live, this
succession of months and years, of days and nights, the apparent motions
of the heavens, these starry skies, the divine rays of the moon, the
whole totality of things, constitutes in some sort the tissue of our
existence, and it is indeed extraordinary that the inhabitants of our
planet should almost all have lived till now without knowing where they
are, without suspecting the marvels of the Universe.
* * * * *
For the rest, my little book is dedicated to a woman, muse and
goddess--the charming enchantress Urania, fit companion of Venus,
ranking even above her in the choir of celestial beauties, as purer and
more noble, dominating with her clear glance the immensities of the
universe. Urania, be it noted, is feminine, and never would the poetry
of the ancients have imagined a masculine symbol to personify the
pageant of the heavens. Not Uranus, nor Saturn, nor Jupiter can compare
with the ideal beauty of Urania.
Moreover, I have before me two delightful books, in breviary binding,
dated the one from the year 1686, the other from a century later, 1786.
The first was written by Fontenelle for a Marquise, and is entitled
Entretiens sur la Pluralité des Mondes. In this, banter is pleasantly
married with science, the author declaring that he only demands from his
fair readers the amount of application they would concede to a novel.
The second is written by Lalande, and is called Astronomie des Dames. In
addressing myself to both sexes, I am in honorable company with these
two sponsors and esteem myself the better for it.
CHAPTER I
THE CONTEMPLATION OF THE HEAVENS
The crimson disk of the Sun has plunged beneath the Ocean. The sea has
decked itself with the burning colors of the orb, reflected from the
Heavens in a mirror of turquoise and emerald. The rolling waves are gold
and silver, and break noisily on a shore already darkened by the
disappearance of the celestial luminary.
We gaze regretfully after the star of day, that poured its cheerful rays
anon so generously over many who were intoxicated with gaiety and
happiness. We dream, contemplating the magnificent spectacle, and in
dreaming forget the moments that are rapidly flying by. Yet the darkness
gradually increases, and twilight gives way to night.
The most indifferent spectator of the setting Sun as it descends beneath
the waves at the far horizon, could hardly be unmoved by the pageant of
Nature at such an impressive moment.
The light of the Crescent Moon, like some fairy boat suspended in the
sky, is bright enough to cast changing and dancing sparkles of silver
upon the ocean. The Evening Star declines slowly in its turn toward the
western horizon. Our gaze is held by a shining world that dominates the
whole of the occidental heavens. This is the "Shepherd's Star," Venus of
rays translucent.
Little by little, one by one, the more brilliant stars shine out. Here
are the white Vega of the Lyre, the burning Arcturus, the seven stars of
the Great Bear, a whole sidereal population catching fire, like
innumerable eyes that open on the Infinite. It is a new life that is
revealed to our imagination, inviting us to soar into these mysterious
regions.
O Night, diapered with fires innumerable! hast thou not written in
flaming letters on these Constellations the syllables of the great
enigma of Eternity? The contemplation of thee is a wonder and a charm.
How rapidly canst thou efface the regrets we suffered on the departure
of our beloved Sun! What wealth, what beauty hast thou not reserved for
our enraptured souls! Where is the man that can remain blind to such a
pageant and deaf to its language!
To whatever quarter of the Heavens we look, the splendors of the night
are revealed to our astonished gaze. These celestial eyes seem in their
turn to gaze at, and to question us. Thus indeed have they questioned
every thinking soul, so long as Humanity has existed on our Earth. Homer
saw and sung these self-same stars. They shone upon the slow succession
of civilizations that have disappeared, from Egypt of the period of the
Pyramids, Greece at the time of the Trojan War, Rome and Carthage,
Constantine and Charlemagne, down to the Twentieth Century. The
generations are buried with the dust of their ancient temples. The Stars
are still there, symbols of Eternity.
The silence of the vast and starry Heavens may terrify us; its immensity
may seem to overwhelm us. But our inquiring thought flies curiously on
the wings of dream, toward the remotest regions of the visible. It rests
on one star and another, like the butterfly on the flower. It seeks what
will best respond to its aspirations: and thus a kind of communication
is established, and, as it were, protected by all Nature in these silent
appeals. Our sense of solitude has disappeared. We feel that, if only as
infinitesimal atoms, we form part of that immense universe, and this
dumb language of the starry night is more eloquent than any speech. Each
star becomes a friend, a discreet confidant, often indeed a precious
counsellor, for all the thoughts it suggests to us are pure and holy.
Is any poem finer than the book written in letters of fire upon the
tablets of the firmament? Nothing could be more ideal. And yet, the
poetic sentiment that the beauty of Heaven awakens in our soul ought
not to veil its reality from us. That is no less marvelous than the
mystery by which we were enchanted.
And here we may ask ourselves how many there are, even among thinking
human beings, who ever raise their eyes to the starry heavens? How many
men and women are sincerely, and with unfeigned curiosity, interested in
these shining specks, and inaccessible luminaries, and really desirous
of a better acquaintance with them?
Seek, talk, ask in the intercourse of daily life. You, who read these
pages, who already love the Heavens, and comprehend them, who desire to
account for our existence in this world, who seek to know what the Earth
is, and what Heaven--you shall witness that the number of those
inquiring after truth is so limited that no one dares to speak of it, so
disgraceful is it to the so-called intelligence of our race. And yet!
the great Book of the Heavens is open to all eyes. What pleasures await
us in the study of the Universe! Nothing could speak more eloquently to
our heart and intellect!
Astronomy is the science _par excellence_. It is the most beautiful and
most ancient of all, inasmuch as it dates back to the indeterminate
times of highest antiquity. Its mission is not only to make us
acquainted with the innumerable orbs by which our nights are
illuminated, but it is, moreover, thanks to it that we know where and
what we are. Without it we should live as the blind, in eternal
ignorance of the very conditions of our terrestrial existence. Without
it we should still be penetrated with the naïve error that reduced the
entire Universe to our minute globule, making our Humanity the goal of
the Creation, and should have no exact notion of the immense reality.
To-day, thanks to the intellectual labor of so many centuries, thanks
also to the immortal genius of the men of science who have devoted their
lives to searching after Truth--men such as Copernicus, Galileo, Kepler,
Newton--the veil of ignorance has been rent, and glimpses of the marvels
of creation are perceptible in their splendid truth to the dazzled eye
of the thinker.
The study of Astronomy is not, as many suppose, the sacrifice of oneself
in a cerebral torture that obliterates all the beauty, the fascination,
and the grandeur of the pageant of Nature. Figures, and naught but
figures, would not be entertaining, even to those most desirous of
instruction. Let the reader take courage! We do not propose that he
shall decipher the hieroglyphics of algebra and geometry. Perish the
thought! For the rest, figures are but the scaffolding, the method, and
do not exist in Nature.
[Illustration: FIG. 1.--The great Book of the Heavens is open to all
eyes.]
We simply beg of you to open your eyes, to see where you are, so that
you may not stray from the path of truth, which is also the path of
happiness. Once you have entered upon it, no persuasion will be needed
to make you persevere. And you will have the profound satisfaction of
knowing that you are thinking correctly, and that it is infinitely
better to be educated than to be ignorant. The reality is far beyond all
dreams, beyond the most fantastic imagination. The most fairy-like
transformations of our theaters, the most resplendent pageants of our
military reviews, the most sumptuous marvels on which the human race can
pride itself--all that we admire, all that we envy on the Earth--is as
nothing compared with the unheard-of wonders scattered through
Infinitude. There are so many that one does not know how to see them.
The fascinated eye would fain grasp all at once.
If you will yield yourselves to the pleasure of gazing upon the
sparkling fires of Space, you will never regret the moments passed all
too rapidly in the contemplation of the Heavens.
Diamonds, turquoises, rubies, emeralds, all the precious stones with
which women love to deck themselves, are to be found in greater
perfection, more beautiful, and more splendid, set in the immensity of
Heaven! In the telescopic field, we may watch the progress of armies of
majestic and powerful suns, from whose attacks there is naught to fear.
And these vagabond comets and shooting stars and stellar nebulæ, do they
not make up a prodigious panorama? What are our romances in comparison
with the History of Nature? Soaring toward the Infinite, we purify our
souls from all the baseness of this world, we strive to become better
and more intelligent.
* * * * *
But in the first place, you ask, what are the Heavens? This vault
oppresses us. We can not venture to investigate it.
Heaven, we reply, is no vault, it is a limitless immensity,
inconceivable, unfathomable, that surrounds us on all sides, and in the
midst of which our globe is floating. THE HEAVENS ARE ALL THAT EXISTS,
all that we see, and all that we do not see: the Earth on which we are,
that bears us onward in her rapid flight; the Moon that accompanies us,
and sheds her soft beams upon our silent nights; the good Sun to which
we owe our existence; the Stars, suns of Infinitude; in a word--the
whole of Creation.
Yes, our Earth is an orb of the Heavens: the sky is her domain, and our
Sun, shining above our heads, and fertilizing our seasons, is as much a
star as the pretty sparkling points that scintillate up there, in the
far distance, and embellish the calm of our nights with their
brilliancy. All are in the Heavens, you as well as I, for the Earth, in
her course through Space, bears us with herself into the depths of
Infinitude.
In the Heavens there is neither "above" nor "below." These words do not
exist in celestial speech, because their significance is relative to the
surface of this planet only. In reality, for the inhabitants of the
Earth, "low" is the inside, the center of the globe, and "high" is what
is above our heads, all round the Earth. The Heavens are what surround
us on all sides, to Infinity.
The Earth is, like her fellows, Mercury, Venus, Mars, Jupiter, Saturn,
Uranus, Neptune, one of the planets of the great solar family.
The Sun, her father, protects her, and directs all her actions. She, as
the grateful daughter, obeys him blindly. All float in perfect harmony
over the celestial ocean.
But, you may say, on what does the Earth rest in her ethereal
navigation?
On nothing. The Earth turns round the colossal Sun, a little globe of
relatively light weight, isolated on all sides in Space, like a
soap-bubble blown by some careless child.
Above, below, on all sides, millions of similar globes are grouped into
families, and form other systems of worlds revolving round the numerous
and distant stars that people Infinitude; suns more or less analogous to
that by which we are illuminated, and generally speaking of larger bulk,
although our Sun is a million times larger than our planet.
Among the ancients, before the isolation of our globe in Space and the
motions that incessantly alter its position were recognized, the Earth
was supposed to be the immobile lower half of the Universe. The sky was
regarded as the upper half. The ancients supplied our world with
fantastic supports that penetrated to the Infernal Regions. They could
not admit the notion of the Earth's isolation, because they had a false
idea of its weight. To-day, however, we know positively that the Earth
is based on nothing. The innumerable journeys accomplished round it in
all directions give definite proof of this. It is attached to nothing.
As we said before, there is neither "above" nor "below" in the Universe.
What we call "below" is the center of the Earth. For the rest the Earth
turns upon its own axis in twenty-four hours. Night is only a partial
phenomenon, due to the rotary motion of the planet, a motion that could
not exist under conditions other than that of the absolute isolation of
our globe in space.
[Illustration: FIG. 2.--The earth in space. June solstice, midday.]
Since the Sun can only illuminate one side of our globe at one moment,
that is to say one hemisphere, it follows that Night is nothing but the
state of the part that is not illuminated. As the Earth revolves upon
itself, all the parts successively exposed to the Sun are in the day,
while the parts situated opposite to the Sun, in the cone of shadow
produced by the Earth itself, are in night. But whether it be noon or
midnight, the stars always occupy the same position in the Heavens,
even when, dazzled by the ardent light of the orb of day, we can no
longer see them; and when we are plunged into the darkness of the night,
the god Phoebus still continues to pour his beneficent rays upon the
countries turned toward him.
The sequence of day and night is a phenomenon belonging, properly
speaking, to the Earth, in which the rest of the Universe does not
participate. The same occurs for every world that is illuminated by a
sun, and endowed with a rotary movement. In absolute space, there is no
succession of nights and days.
Upheld in space by forces that will be explained at a later point, our
planet glides in the open heavens round our Sun.
Imagine a magnificent aerostat, lightly and rapidly cleaving space.
Surround it with eight little balloons of different sizes, the smallest
like those sold on the streets for children to play with, the larger,
such as are distributed for a bonus in large stores. Imagine this group
sailing through the air, and you have the system of our worlds in
miniature.
Still, this is only an image, a comparison. The balloons are held up by
the atmosphere, in which they float at equilibrium. The Earth is
sustained by nothing material. What maintains her in equilibrium is the
ethereal void; an immaterial force; gravitation. The Sun attracts her,
and if she did not revolve, she would drop into him; but rotating round
him, at a speed of 107,000 kilometers[2] (about 66,000 miles) per hour,
she produces a centrifugal force, like that of a stone in a sling, that
is precisely equivalent, and of contrary sign, to its gravitation toward
the central orb, and these two equilibrated forces keep her at the same
medium distance.
This solar and planetary group does not exist solitary in the immense
void that extends indefinitely around us. As we said above, each star
that we admire in the depths of the sky, and to which we lift up our
eyes and thoughts during the charmed hours of the night, is another sun
burning with its own light, the chief of a more or less numerous family,
such as are multiplied through all space to infinity. Notwithstanding
the immense distances between the sun-stars, Space is so vast, and the
number of these so great, that by an effect of perspective due solely to
the distance, appearances would lead us to believe that the stars were
touching. And under certain telescopic aspects, and in some of the
astral photographs, they really do appear to be contiguous.
The Universe is infinite. Space is limitless. If our love for the
Heavens should incite in us the impulse, and provide us with the means
of undertaking a journey directed to the ends of Heaven as its goal, we
should be astonished, on arriving at the confines of the Milky Way, to
see the grandiose and phenomenal spectacle of a new Universe unfold
before our dazzled eyes; and if in our mad career we crossed this new
archipelago of worlds to seek the barriers of Heaven beyond them, we
should still find universe eternally succeeding to universe before us.
Millions of suns roll on in the immensities of Space. Everywhere, on all
sides, Creation renews itself in an infinite variety.
According to all the probabilities, universal life is distributed there
as well as here, and has sown the germ of intelligence upon those
distant worlds that we divine in the vicinity of the innumerable suns
that plow the ether, for everything upon the Earth tends to show that
Life is the goal of Nature. Burning foci, inextinguishable sources of
warmth and light, these various, multi-colored suns shed their rays upon
the worlds that belong to them and which they fertilize.
Our globe is no exception in the Universe. As we have seen, it is one of
the celestial orbs, nourished, warmed, lighted, quickened by the Sun,
which in its turn again is but a star.
Innumerable Worlds! We dream of them. Who can say that their unknown
inhabitants do not think of us in their turn, and that Space may not be
traversed by waves of thought, as it is by the vibrations of light and
universal gravitation? May not an immense solidarity, hardly guessed at
by our imperfect senses, exist between the Celestial Humanities, our
Earth being only a modest planet.
Let us meditate on this Infinity! Let us lose no opportunity of
employing the best of our hours, those of the silence and peace of the
bewitching nights, in contemplating, admiring, spelling out the words of
the Great Book of the Heavens. Let our freed souls fly swift and rapt
toward those marvelous countries where indescribable joys are prepared
for us, and let us do homage to the first and most splendid of the
sciences, to Astronomy, which diffuses the light of Truth within us.
To poetical souls, the contemplation of the Heavens carries thought away
to higher regions than it attains in any other meditation. Who does not
remember the beautiful lines of Victor Hugo in the Orientales? Who has
not heard or read them? The poem is called "Ecstasy," and it is a
fitting title. The words are sometimes set to music, and the melody
seems to complete their pure beauty:
J'étais seul près des flots par une nuit d'étoiles.
Pas un nuage aux cieux, sur les mers pas de voiles;
Mes yeux plongeaient plus loin que le monde réel,
Et les bois et les monts et toute la nature
Semblaient interroger, dans un confus murmure,
Les flots des mers, les feux du ciel.
Et les étoiles d'or, légions infinies,
A voix haute, à voix basse, avec mille harmonies
Disaient, en inclinant leurs couronnes de feu;
Et les flots bleus, que rien ne gouverne et n'arrête,
Disaient en recourbant l'écume de leur crête:
... C'est le Seigneur, le Seigneur Dieu!
_Note: Free Translation_
I was alone on the waves, on a starry night,
Not a cloud in the sky, not a sail in sight,
My eyes pierced beyond the natural world...
And the woods, and the hills, and the voice of Nature
Seemed to question in a confused murmur,
The waves of the Sea, and Heaven's fires.
And the golden stars in infinite legion,
Sang loudly, and softly, in glad recognition,
Inclining their crowns of fire;...
And the waves that naught can check nor arrest
Sang, bowing the foam of their haughty crest...
Behold the Lord God--Jehovah!
The immortal poet of France was an astronomer. The author more than
once had the honor of conversing with him on the problems of the starry
sky--and reflected that astronomers might well be poets.
It is indeed difficult to resist a sense of profound emotion before the
abysses of infinite Space, when we behold the innumerable multitude of
worlds suspended above our heads. We feel in this solitary contemplation
of the Heavens that there is more in the Universe than tangible and
visible matter: that there are forces, laws, destinies. Our ants' brains
may know themselves microscopic, and yet recognize that there is
something greater than the Earth, the Heavens;--more absolute than the
Visible, the Invisible;--beyond the more or less vulgar affairs of life,
the sense of the True, the Good, the Beautiful. We feel that an immense
mystery broods over Nature,--over Being, over created things. And it is
here again that Astronomy surpasses all the other sciences, that it
becomes our sovereign teacher, that it is the _pharos_ of modern
philosophy.
O Night, mysterious, sublime, and infinite! withdrawing from our eyes
the veil spread above us by the light of day, giving back transparency
to the Heavens, showing us the prodigious reality, the shining casket of
the celestial diamonds, the innumerable stars that succeed each other
interminably in immeasurable space! Without Night we should know
nothing. Without it our eyes would never have divined the sidereal
population, our intellects would never have pierced the harmony of the
Heavens, and we should have remained the blind, deaf parasites of a
world isolated from the rest of the universe. O Sacred Night! If on the
one hand it rests upon the heights of Truth beyond the day's illusions,
on the other its invisible urns pour down a silent and tranquil peace, a
penetrating calm, upon our souls that weary of Life's fever. It makes us
forget the struggles, perfidies, intrigues, the miseries of the hours of
toil and noisy activity, all the conventionalities of civilization. Its
domain is that of rest and dreams. We love it for its peace and calm
tranquillity. We love it because it is true. We love it because it
places us in communication with the other worlds, because it gives us
the presage of Life, Universal and Eternal, because it brings us Hope,
because it proclaims us citizens of Heaven.
CHAPTER II
THE CONSTELLATIONS
In Chapter I we saw the Earth hanging in space, like a globe isolated on
all sides, and surrounded at vast distances by a multitude of stars.
These fiery orbs are suns like that which illuminates ourselves. They
shine by their own light. We know this for a fact, because they are so
far off that they could neither be illuminated by the Sun, nor, still
more, reflect his rays back upon us: and because, on the other hand, we
have been able to measure and analyze their light. Many of these distant
suns are simple and isolated; others are double, triple, or multiple;
others appear to be the centers of systems analogous to that which
gravitates round our own Sun, and of which we form part. But these
celestial tribes are situated at such remote distances from us that it
is impossible to distinguish all the individuals of each particular
family. The most delicate observations have only revealed a few of them.
We must content ourselves here with admiring the principals,--the
sun-stars,--prodigious globes, flaming torches, scattered profusely
through the firmament.
How, then, is one to distinguish them? How can they be readily found and
named? There are so many of them!
Do not fear; it is quite a simple matter. In studying the surface of the
Earth we make use of geographical maps on which the continents and seas
of which it consists are drawn with the utmost care. Each country of our
planet is subdivided into states, each of which has its proper name. We
shall pursue the same plan in regard to the Heavens, and it will be all
the easier since the Great Book of the Firmament is constantly open to
our gaze. Our globe, moreover, actually revolves upon itself so that we
read the whole in due sequence. Given a clear atmosphere, and a little
stimulus to the will from our love of truth and science, and the
geography of the Heavens, or "uranography," will soon be as familiar to
us as the geography of our terrestrial atom.
On a beautiful summer's night, when we look toward the starry sky, we
are at first aware only of a number of shining specks. The stars seem to
be scattered almost accidentally through Space; they are so numerous and
so close to one another that it would appear rash to attempt to name
them separately. Yet some of the brighter ones particularly attract and
excite our attention. After a little observation we notice a certain
regularity in the arrangement of these distant suns, and take pleasure
in drawing imaginary figures round the celestial groups.
That is what the ancients did from a practical point of view. In order
to guide themselves across the trackless ocean, the earliest Phenician
navigators noted certain fixed bearings in the sky, by which they mapped
out their routes. In this way they discovered the position of the
immovable Pole, and acquired empire over the sea. The Chaldean pastors,
too, the nomad people of the East, invoked the Heavens to assist in
their migrations. They grouped the more brilliant of the stars into
Constellations with simple outlines, and gave to each of these celestial
provinces a name derived from mythology, history, or from the natural
kingdoms. It is impossible to determine the exact epoch of this
primitive celestial geography. The Centaur Chiron, Jason's tutor, was
reputed the first to divide the Heavens upon the sphere of the
Argonauts. But this origin is a little mythical! In the Bible we have
the Prophet Job, who names Orion, the Pleiades, and the Hyades, 3,300
years ago. The Babylonian Tables, and the hieroglyphs of Egypt, witness
to an astronomy that had made considerable advance even in those remote
epochs. Our actual constellations, which are doubtless of Babylonian
origin, appear to have been arranged in their present form by the
learned philosopher Eudoxus of Cnidus, about the year 360 B.C. Aratus
sang of them in a didactic poem toward 270. Hipparchus of Rhodes was the
first to note the astronomical positions with any precision, one hundred
and thirty years before our era. He classified the stars in order of
magnitude, according to their apparent brightness; and his catalogue,
preserved in the Almagest of Ptolemy, contains 1,122 stars distributed
into forty-eight Constellations.
The figures of the constellations, taken almost entirely from fable, are
visible only to the eyes of the imagination, and where the ancients
placed such and such a person or animal, we may see, with a little
good-will, anything we choose to fancy. There is nothing real about
these figures. And yet it is indispensable to be able to recognize the
constellations in order to find our way among the innumerable army of
the stars, and we shall commence this study with the description of the
most popular and best known of them all, the one that circles every
night through our Northern Heavens. Needless to name it; it is familiar
to every one. You have already exclaimed--the Great Bear!
This vast and splendid association of suns, which is also known as the
Chariot of David, the Plow or Charles's Wain, and the Dipper, is one of
the finest constellations in the Heavens, and one of the oldest--seeing
that the Chinese hailed it as the divinity of the North, over three
thousand years ago.
If any of my readers should happen to forget its position in the sky,
the following is a very simple expedient for finding it. Turn to the
North--that is, opposite to the point where the sun is to be found at
midday. Whatever the season of the year, day of the month, or hour of
the night, you will always see, high up in the firmament, seven
magnificent stars, arranged in a quadrilateral, followed by a tail, or
handle, of three stars. This magnificent constellation never sinks below
our horizon. Night and day it watches above us, turning in twenty-four
hours round a very famous star that we shall shortly become acquainted
with. In the figure of the Great Bear, the four stars of the
quadrilateral are found in the body, and the three at the extremity make
the tail. As David's Chariot, the four stars represent the wheels, and
the three others the horses.
Sometimes our ancestors called them the Seven Oxen, the "oxen of the
celestial pastures," from which the word septentrion (_septem triones_,
seven oxen of labor) is derived. Some see a Plowshare; others more
familiarly call this figure the Dipper. As it rotates round the pole,
its outline varies with the different positions.
It is not easy to guess why this constellation should have been called
the Bear. Yet the name has had a certain influence. From the Greek word
_arctos_ (bear) has come arctic, and for its antithesis, antarctic. From
the Latin word _trio_ (ox of labor) has come septentrion, the seven
oxen. Etymology is not always logical. Is not the word "venerate"
derived from Venus?
In order to distinguish one star from another, the convention of
denoting them by the letters of the Greek Alphabet has been adopted, for
it would be impossible to give a name to each, so considerable is their
number.[3]
[alpha] and [beta] denote the front wheels of the Chariot generally
known as the "pointers;" [gamma] and [delta] the hind wheels; [epsilon],
[zeta], [eta] the three horses. All these stars are of the second order
of magnitude (the specific meaning of this expression will be explained
in the next chapter), except the last ([delta]) of the quadrilateral,
which is of the third order.
[Illustration: FIG. 3.--The Great Bear (or Dipper), and the Pole-Star.]
Figure 3 gives the outline of this primitive constellation. In revolving
in twenty-four hours round the Pole, which is situated at the
prolongation of a line drawn from [beta] to [alpha], it occupies every
conceivable position,--as if this page were turned in all directions.
But the relative arrangement of the seven stars remains unaltered. In
contemplating these seven stars it must never be forgotten that each is
a dazzling sun, a center of force and life. One of them is especially
remarkable: [zeta], known as Mizar to the Arabs. Those who have good
sight will distinguish near it a minute star, Alcor, or the Cavalier,
also called Saidak by the Arabs--that is, the Test, because it can be
used as a test of vision. But further, if you have a small telescope at
your disposal, direct it upon the fine star Mizar: you will be
astonished at discovering two of the finest diamonds you could wish to
see, with which no brilliant is comparable. There are several double
stars; these we shall become acquainted with later on.
Meantime, we must not forget our celestial geography. The Great Bear
will help us to find all the adjacent constellations.
[Illustration: FIG. 4.--To find the Pole-Star.]
If a straight line is drawn (Fig. 4) from [beta] through [alpha], which
forms the extremity of the square, and is prolonged by a quantity equal
to the distance of [alpha] from the tip of the handle, we come on a star
of second magnitude, which marks the extremity of a figure perfectly
comparable with the Great Bear, but smaller, less brilliant, and
pointing in the contrary direction. This is the Little Bear, composed,
like its big brother, of seven stars; the one situated at the end of the
line by which we have found it is the Pole-Star.
Immovable in the region of the North Pole, the Pole-Star has captivated
all eyes by its position in the firmament. It is the providence of
mariners who have gone astray on the ocean, for it points them to the
North, while it is the pivot of the immense rotation accomplished round
it by all the stars in twenty-four hours. Hence it is a very important
factor, and we must hasten to find it, and render it due homage. It
should be added that its special immobility, in the prolongation of the
Earth's axis, is merely an effect caused by the diurnal movements of our
planet. Our readers are of course aware that it is the earth that turns
and not the sky. But evidence of this will be given later on. In looking
at the Pole-Star, the South is behind one, the East to the right, and
the West to the left.
Between the Great and the Little Bear, we can distinguish a winding
procession of smaller stars. These constitute the Dragon.
We will continue our journey by way of Cassiopeia, a fine constellation
placed on the opposite side of the Pole-Star in relation to the Great
Bear, and shaped somewhat like the open limbs of the letter W. It is
also called the Chair. And, in fact, when the figure is represented with
the line [alpha] [beta] below, the line [chi] [gamma] forms the seat,
and [gamma] [delta] [epsilon] its back.
If a straight line is drawn from [delta] of the Great Bear, and
prolonged beyond the Pole-Star in a quantity equal to the distance which
separates these two stars, it is easy to find this constellation (Fig.
5). This group, like the preceding, never sets, and is always visible,
opposite to the Great Bear. It revolves in twenty-four hours round the
Pole-Star, and is to be seen, now above, now below, now to the right,
now to the left.
[Illustration: FIG. 5.--To find Cassiopeia.]
[Illustration: FIG. 6.--To Find Pegasus and Andromeda.]
If in the next place, starting from the stars [alpha] and [delta] in the
Great Bear, we draw two lines which join at Polaris and are prolonged
beyond Cassiopeia, we arrive at the Square of Pegasus (Fig. 6), a vast
constellation that terminates on one side in a prolongation formed of
three stars.
These three last stars belong to Andromeda, and themselves abut on
Perseus. The last star in the Square of Pegasus is also the first in
Andromeda.
[gamma] of Andromeda is a magnificent double orb, to which we shall
return in the next chapter, _i.e._, the telescope resolves it into two
marvelous suns, one of which is topaz-yellow, and the other
emerald-green. Three stars, indeed, are visible with more powerful
instruments.
[Illustration: FIG. 7.--Perseus, the Pleiades, Capella.]
Above [beta] and near a small star, is visible a faint, whitish,
luminous trail: this is the oblong nebula of Andromeda, the first
mentioned in the history of astronomy, and one of the most beautiful in
the Heavens, perceptible to the unaided eye on very clear nights.
The stars [alpha], [beta] and [gamma] of Perseus form a concave bow
which will serve in a new orientation. If it is prolonged in the
direction of [delta], we find a very brilliant star of the first
magnitude. This is Capella, the Goat, in the constellation of the
Charioteer (Fig. 7).
If coming back to [delta] in Perseus, a line is drawn toward the South,
we reach the Pleiades, a gorgeous cluster of stars, scintillating like
the finest dust of diamonds, on the shoulder of the Bull, to which we
shall come shortly, in studying the Constellations of the Zodiac.
Not far off is a very curious star, [beta] of Perseus, or Algol, which
forms a little triangle with two others smaller than itself. This star
is peculiar in that, instead of shining with a fixed light, it varies in
intensity, and is sometimes pale, sometimes brilliant. It belongs to the
category of variable stars which we shall study later on. All the
observations made on it for more than two hundred years go to prove that
a dark star revolves round this sun, almost in the plane of our line of
sight, producing as it passes in front of it a partial eclipse that
reduces it from the second to the fourth magnitude, every other two
days, twenty hours, and forty-nine minutes.
And now, let us return to the Great Bear, which aided us so beneficently
to start for these distant shores, and whence we shall set out afresh in
search of other constellations.
If we produce the curved line of the tail, or handle, we encounter a
magnificent golden-yellow star, a splendid sun of dazzling brilliancy:
let us make our bow to Arcturus, [alpha] of the Herdsman, which is at
the extremity of this pentagonal constellation. The principal stars of
this asterism are of the third magnitude, with the exception of [alpha],
which is of the first. Alongside of the Herdsman is a circle consisting
of five stars of the third and fourth magnitude, save the third,
[alpha], or the Pearl, which is of the second magnitude. This is the
Corona Borealis. It is very easily recognized (Fig. 8).
[Illustration: FIG. 8.--To find Arcturus, the Herdsman, and the Northern
Crown.]
A line drawn from the Pole-Star to Arcturus forms the base of an
equilateral triangle, the apex of which, situated opposite the Great
Bear, is occupied by Vega, or [alpha] of the Lyre, a splendid diamond of
ideal purity scintillating through the ether. This magnificent star, of
first magnitude, is, with Arcturus, the most luminous in our Heavens. It
burns with a white light, in the proximity of the Milky Way, not far
from a constellation that is very easily recognized by the arrangement
of its principal stars in the form of a cross. It is named Cygnus, the
Bird, or the Swan (Fig. 9), and is easy to find by the Square of
Pegasus, and the Milky Way. This figure, the brilliancy of whose
constituents (of the third and fourth magnitudes) contrasts strongly
with the pallor of the Milky Way, includes at its extremity at the foot
of the Cross, a superb double star, [beta] or Albirio: [alpha] of Cygnus
is also called Deneb. The first star of which the distance was
calculated is in this constellation. This little orb of fifth magnitude,
which hangs 69,000,000,000,000 kilometers (42,000,000,000,000 miles)
above our Earth, is the nearest of all the stars to the skies of Europe.
[Illustration: FIG. 9.--The Swan, Vega, the Eagle.]
Not far off is the fine Eagle, which spreads its wings in the Milky Way,
and in which the star Altaïr, [alpha], of first magnitude, is situated
between its two satellites, [beta] and [gamma].
The Constellation of Hercules, toward which the motions of the Sun are
impelling us, with all the planets of its system, is near the Lyre. Its
principal stars can be recognized inside the triangle formed by the
Pole-Star, Arcturus, and Vega.
All the Constellations described above belong to the Northern
Hemisphere. Those nearest the pole are called circumpolar. They revolve
round the pole in twenty-four hours.
Having now learned the Northern Heavens, we must come back to the Sun,
which we have left behind us. The Earth revolves round him in a year,
and in consequence he seems to revolve round us, sweeping through a vast
circle of the celestial sphere. In each year, at the same period, he
passes the same points of the Heavens, in front of the same
constellations, which are rendered invisible by his light. We know that
the stars are at a fixed position from the Earth, whatever their
distance, and that if we do not see them at noon as at midnight, it is
simply because they are extinguished by the dazzling light of the orb of
day. With the aid of a telescope it is always possible to see the more
brilliant of them.
The Zodiac is the zone of stars traversed by the Sun in the course of a
year. This word is derived from the Greek _Zodiakos_, which signifies
"animal," and this etymology arose because most of the figures traced
on this belt of stars represent animals. The belt is divided into twelve
parts that are called the twelve Signs of the Zodiac, also named by the
ancients the "Houses of the Sun," since the Sun visits one of them in
each month. These are the signs, with the primitive characters that
distinguish them: the Ram [Aries], the Bull [Taurus], the Twins
[Gemini], the Crab [Cancer], the Lion [Leo], the Virgin [Virgo], the
Balance [Libra], the Scorpion [Scorpio], the Archer [Sagittarius], the
Goat [Capricorn], the Water-Carrier [Aquarius], the Fishes [Pisces]. The
sign [Aries] represents the horns of the Ram, [Taurus] the head of the
Bull, and so on.
If you will now follow me into the Houses of the Sun you will readily
recognize them again, provided you have a clear picture of the principal
stars of the Northern Heavens. First, you see the Ram, the initial sign
of the Zodiac; because at the epoch at which the actual Zodiac was
fixed, the Sun entered this sign at the vernal equinox, and the equator
crossed the ecliptic at this point. This constellation, in which the
horns of the Ram (third magnitude) are the brightest, is situated
between Andromeda and the Pleiades. Two thousand years ago, the Ram was
regarded as the symbol of spring; but owing to the secular movement of
the precession of the equinoxes, the Sun is no longer there on March 21:
he is in the Fishes.
To the left, or east of the Ram, we find the Bull, the head of which
forms a triangle in which burns Aldebaran, of first magnitude, a
magnificent red star that marks the right eye; and the Hyades,
scintillating pale and trembling, on its forehead. The timid Pleiades,
as we have seen, veil themselves on the shoulder of the Bull--a
captivating cluster, of which six stars can be counted with the unaided
eye, while several hundred are discovered with the telescope.
Next the Twins. They are easily recognized by the two fine stars,
[alpha] and [beta], of first magnitude, which mark their heads, and
immortalize Castor and Pollux, the sons of Jupiter, celebrated for their
indissoluble friendship.
Cancer, the Crab, is the least important sign of the Zodiac. It is
distinguished only by five stars of fourth and fifth magnitudes,
situated below the line of Castor and Pollux, and by a pale cluster
called Præsepe, the Beehive.
The Lion next approaches, superb in his majesty. At his heart is a
gorgeous star of first magnitude, [alpha] or Regulus. This figure forms
a grand trapezium of four stars on the celestial sphere.
The Virgin exhibits a splendid star of first magnitude; this is Spica,
which with Regulus and Arcturus, form a triangle by which this
constellation can be recognized.
The Balance follows the Virgin. Its scales, marked by two stars of
second magnitude, are situated a little to the East of Spica.
We next come to the eighth constellation of the Zodiac, which is one of
the most beautiful of this belt of stars. Antares, a red star of first
magnitude, occupies the heart of the venomous and accursed Scorpion. It
is situated on the prolongation of a line joining Regulus to Spica, and
forms with Vega of the Lyre, and Arcturus of the Herdsman, a great
isosceles triangle, of which this latter star is the apex.
The Scorpion, held to be a sign of ill luck, has been prejudicial to the
Archer, which follows it, and traces an oblique trapezium in the sky, a
little to the east of Antares. These two southernmost constellations
never rise much above the horizon for France and England. In fable, the
Archer is Chiron, the preceptor of Jason, Achilles and Æsculapius.
Capricorn lies to the south of Altaïr, on the prolongation of a line
from the Lyre to the Eagle. It is hardly noticeable save for the stars
[alpha] and [beta] of third magnitude, which scintillate on its
forehead.
The Water-Carrier pours his streams toward the horizon. He is not rich
in stars, exhibiting only three of third magnitude that form a very
flattened triangle.
Lastly the Fishes, concluding sign of the Zodiac, are found to the
south of Andromeda and Pegasus. Save for [alpha], of third magnitude,
this constellation consists of small stars that are hardly visible.
These twelve zodiacal constellations will be recognized on examining the
chart (Figs. 10-11).
We must now visit the stars of the Southern Heavens, some of which are
equally deserving of admiration.
[Illustration: FIG. 10.--The Constellations of the Zodiac: summer and
autumn; Capricorn, Archer, Scorpion, Balance, Virgin, Lion.]
It should in the first place be noted that the signs of the Zodiac and
the Southern Constellations are not, like those which are circumpolar,
perpetually visible at all periods of the year. Their visibility depends
on the time of year and the hour of the night.[4]
In order to admire the fine constellations of the North, as described
above, we have only to open our windows on a clear summer's evening, or
walk round the garden in the mysterious light of these inaccessible
suns, while we look up at the immense fields in which each star is like
the head of a celestial spear.
But the summer is over, autumn is upon us, and then, too soon, comes
winter clothed in hoar-frost. The days are short and cold, dark and
dreary; but as a compensation the night is much longer, and adorns
herself with her most beautiful jewels, offering us the contemplation of
her inexhaustible treasures.
[Illustration: FIG. 11.--The Constellations of the Zodiac: winter and
spring; Crab, Twins, Bull, Ram, Fishes, Water-Carrier.]
First, let us do homage to the magnificent Orion, most splendid of all
the constellations: he advances like a colossal giant, and confronts the
Bull.
This constellation appears about midnight in November, in the
south-eastern Heavens; toward eleven o'clock in December and January,
due south; about ten in February, in the south-east; about nine in
March, and about eight in April, in the west; and then sets below our
horizon.
[Illustration: FIG. 12.--Orion and his celestial companions.]
It is indisputably the most striking figure in the sky, and with the
Great Bear, the most ancient in history, the first that was noticed:
both are referred to in the ancient texts of China, Chaldea, and Egypt.
Eight principal stars delineate its outline; two are of the first
magnitude, five of the second, and one of the third (Fig. 12). The most
brilliant are Betelgeuse ([alpha]) and Rigel ([beta]): the former
marking the right shoulder of the Colossus as it faces us; the second
the left foot. The star on the left shoulder is [gamma] or Bellatrix, of
second magnitude; that of the right foot, [chi], is almost of the third.
Three stars of second magnitude placed obliquely at equal distances from
each other, the first or highest of which marks the position of the
equatorial line, indicate the Belt or Girdle. These stars, known as the
Three Kings, and by country people as the Rake, assist greatly in the
recognition of this fine constellation.
A little below the second star of the Belt, a large white patch, like a
band of fog, the apparent dimensions of which are equal to that of the
lunar disk, is visible to the unaided eye: this is the Nebula of Orion,
one of the most magnificent in the entire Heavens. It was discovered in
1656 by Huyghens, who counted twelve stars in the pale cloud. Since that
date it has been constantly studied and photographed by its many
admirers, while the giant eye of the telescope discovers in it to-day an
innumerable multitude of little stars which reveal the existence of an
entire universe in this region.
Orion is not merely the most imposing of the celestial figures; it is
also the richest in sidereal wonders. Among these, it exhibits the most
complex of all the multiple systems known to us: that of the star
[theta] situated in the celebrated nebula just mentioned. This marvelous
star, viewed through a powerful telescope, breaks up into six suns,
forming a most remarkable stellar group.
This region is altogether one of the most brilliant in the entire
firmament. We must no longer postpone our homage to the brightest star
in the sky, the magnificent Sirius, which shines on the left below
Orion: it returns every year toward the end of November. This marvelous
star, of dazzling brilliancy, is the first, [alpha], in the
constellation of the Great Dog, which forms a quadrilateral, the base of
which is adjacent to a triangle erected from the horizon.
When astronomers first endeavored to determine the distance of the
stars, Sirius, which attracted all eyes to its burning fires, was the
particular object of attention. After long observation, they succeeded
in determining its distance as 92 trillion kilometers (57 trillion
miles). Light, that radiates through space at a velocity of 300,000
kilometers (186,000 miles) per second, takes no less than ten years to
reach us from this sun, which, nevertheless, is one of our neighbors.
The Little Dog, in which Procyon ([alpha], of first magnitude) shines
out, is above its big brother. With the exception of [alpha], it has no
bright stars.
[Illustration: FIG. 13.--Winter Constellations.]
Lastly, toward the southern horizon, we must notice the Hydra, Eridanus,
the Whale, the Southern Fish, the Ship, and the Centaur. This last
constellation, while invisible to our latitudes, contains the star that
is nearest to the Earth, [alpha], of first magnitude, the distance of
which is 40 trillion kilometers (25 trillion miles).
[Illustration: FIG. 14.--Spring Constellations.]
The feet of the Centaur touch the Southern Cross, which is always
invisible to us, and a little farther down the Southern Pole reigns
over the icy desert of the antarctic regions.
[Illustration: FIG. 15.--Summer Constellations.]
[Illustration: FIG. 16.--Autumn Constellations.]
In order to complete the preceding descriptions, we subjoin four charts
representing the aspect of the starry heavens during the evenings of
winter, spring, summer, and autumn. To make use of these, we must
suppose them to be placed above our heads, the center marking the
zenith, and the sky descending all round to the horizon. The horizon,
therefore, bounds these panoramas. Turning the chart in any direction,
and looking at it from north, south, east, or west, we find all the
principal stars. The first map (Fig. 13) represents the sky in winter
(January) at 8 P.M.; the second, in spring (April) at 9 P.M.; the third,
in summer (July) at the same hour; the fourth, the sky in autumn
(October) at the same time.
And so, at little cost, we have made one of the grandest and most
beautiful journeys conceivable. We now have a new country, or, better,
have learned to see and know our own country, for since the Earth is a
planet we must all be citizens of the Heavens before we can belong to
such or such a nation of our lilliputian world.
We must now study this sublime spectacle of the Heavens in detail.
CHAPTER III
THE STARS, SUNS OF THE INFINITE
A JOURNEY THROUGH SPACE
We have seen from the foregoing summary of the principal Constellations
that there is great diversity in the brightness of the stars, and that
while our eyes are dazzled with the brilliancy of certain orbs, others,
on the contrary, sparkle modestly in the azure depths of the night, and
are hardly perceptible to the eye that seeks to plumb the abysses of
Immensity.
We have appended the word "magnitude" to the names of certain stars, and
the reader might imagine this to bear some relation to the volume of the
orb. But this is not the case.
To facilitate the observation of stars of varying brilliancy, they have
been classified in order of magnitude, according to their apparent
brightness, and since the dimensions of these distant suns are almost
wholly unknown to us, the most luminous stars were naturally denoted as
of first magnitude, those which were a little less bright of the second,
and so on. But in reality this word "magnitude" is quite erroneous, for
it bears no relation to the mass of the stars, divided thus at an epoch
when it was supposed that the most brilliant must be the largest. It
simply indicates the apparent brightness of a star, the real brilliancy
depending on its dimensions, its intrinsic light, and its distance from
our planet.
And now to make some comparison between the different orders. Throughout
the entire firmament, only nineteen stars of first magnitude are
discoverable. And, strictly speaking, the last of this series might just
as well be noted of "second magnitude," while the first of the second
series might be added to the list of stars of the "first order." But in
order to form classes distinct from one another, some limit has to be
adopted, and it was determined that the first series should include only
the following stars, the most luminous in the Heavens, which are
subjoined in order of decreasing brilliancy.
STARS OF THE FIRST MAGNITUDE
1. Sirius, or [alpha] of the Great Dog.
2. Canopus, or [alpha] of the Ship.
3. Capella, or [alpha] of the Charioteer.
4. Arcturus, or [alpha] of the Herdsman.
5. Vega, or [alpha] of the Lyre.
6. Proxima, or [alpha] of the Centaur.
7. Rigel, or [beta] of Orion.
8. Achernar, or [alpha] of Eridanus.
9. Procyon, or [alpha] of the Little Dog.
10. [beta] of the Centaur.
11. Betelgeuse, or [alpha] of Orion.
12. Altaïr, or [alpha] of the Eagle.
13. [alpha] of the Southern Cross.
14. Aldebaran, or [alpha] of the Bull.
15. Spica, or [alpha] of the Virgin.
16. Antares, or [alpha] of the Scorpion.
17. Pollux, or [beta] of the Twins.
18. Regulus, or [alpha] of the Lion.
19. Fomalhaut, or [alpha] of the Southern Fish.
THE STARS OF THE SECOND MAGNITUDE
Then come the stars of the second magnitude, of which there are
fifty-nine. The stars of the Great Bear (with the exception of [delta],
which is of third magnitude), the Pole-Star, the chief stars in Orion
(after Rigel and Betelgeuse), of the Lion, of Pegasus, of Andromeda, of
Cassiopeia, are of this order. These, with the former, constitute the
principal outlines of the constellations visible to us.
Then follow the third and fourth magnitudes, and so on.
* * * * *
The following table gives a summary of the series, down to the sixth
magnitude, which is the limit of visibility for the unaided human eye:
19 stars of first magnitude.
59 of second magnitude.
182 of third magnitude.
530 of fourth magnitude.
1,600 of fifth magnitude.
4,800 of sixth magnitude.
This makes a total of some seven thousand stars visible to the unaided
eye. It will be seen that each series is, roughly speaking, three times
as populated as that preceding it; consequently, if we multiply the
number of any class by three, we obtain the approximate number of stars
that make up the class succeeding it.
Seven thousand stars! It is an imposing figure, when one reflects that
all these lucid points are suns, as enormous as they are potent, as
incandescent as our own (which exceeds the volume of the Earth by more
than a million times), distant centers of light and heat, exerting their
attraction on unknown systems. And yet it is generally imagined that
millions of stars are visible in the firmament. This is an illusion;
even the best vision is unable to distinguish stars below the sixth
magnitude, and ordinary sight is far from discovering all of these.
Again, seven thousand stars for the whole Heavens makes only three
thousand five hundred for half the sky. And we can only see one
celestial hemisphere at a time. Moreover, toward the horizon, the vapor
of the atmosphere veils the little stars of sixth magnitude. In reality,
we never see at a given moment more than three thousand stars. This
number is below that of the population of a small town.
* * * * *
But celestial space is unlimited, and we must not suppose that these
seven thousand stars that fascinate our eyes and enrich our Heavens,
without which our nights would be black, dark, and empty,[5] comprise
the whole of Creation. They only represent the vestibule of the temple.
Where our vision is arrested, a larger, more powerful eye, that is
developing from century to century, plunges its analyzing gaze into the
abysses, and reflects back to the insatiable curiosity of science the
light of the innumerable suns that it discovers. This eye is the lens of
the optical instruments. Even opera-glasses disclose stars of the
seventh magnitude. A small astronomical objective penetrates to the
eighth and ninth orders. More powerful instruments attain the tenth.
The Heavens are progressively transformed to the eye of the astronomer,
and soon he is able to reckon hundreds of thousands of orbs in the
night. The evolution continues, the power of the instrument is
developed; and the stars of the eleventh and twelfth magnitudes are
discovered successively, and together number four millions. Then follow
the thirteenth, fourteenth, and fifteenth magnitudes. This is the
sequence:
7th magnitude 13,000.
8th " 40,000.
9th " 120,000.
10th " 380,000.
11th " 1,000,000.
12th " 3,000,000.
13th " 9,000,000.
14th " 27,000,000.
15th " 80,000,000.
Accordingly, the most powerful telescopes of the day, reenforced by
celestial photography, can bring a stream of more than 120 millions of
stars into the scope of our vision.
The photographic map of the Heavens now being executed comprises the
first fourteen magnitudes, and will give the precise position of some
40,000,000 stars, distributed over 22,054 sheets, forming a sphere 3
meters 44 centimeters in diameter.
The boldest imagination is overwhelmed by these figures, and fails to
picture such millions of suns--formidable and burning globes that roll
through space, sweeping their systems along with them. What furnaces are
there! what unknown lives! what vast immensities!
And again, what enormous distances must separate the stars, to admit of
their free revolution in the ether! In what abysses, at what a distance
from our terrestrial atom, must these magnificent and dazzling Suns
pursue the paths traced for them by Destiny!
* * * * *
If all the stars radiated an equal light, their distances might be
calculated on the principle that an object appears smaller in proportion
to its distance. But this equality does not exist. The suns were not all
cast in the same mold.
Indeed, the stars differ widely in size and brightness, and the
distances that have been measured show that the most brilliant are not
the nearest. They are scattered through Space at all distances.
Among the nearer stars of which it has been found possible to calculate
the distance, some are found to be of the fourth, fifth, sixth, seventh,
eighth, and even ninth magnitudes, proving that the most brilliant are
not always the least distant.
For the rest, among the beautiful and shining stars with which we made
acquaintance in the last chapter may be cited Sirius, which at a
distance of 92 trillion kilometers (57 trillion miles) from here still
dazzles us with its burning fires; Procyon or [alpha] of the Little Dog,
as remote as 112 trillion kilometers (69-1/2 trillion miles); Altaïr of
the Eagle, at 160 trillion kilometers (99 trillion miles); the white
Vega, at 204 trillion kilometers (126-1/2 trillion miles); Capella, at
276 trillion kilometers (171 trillion miles); and the Pole-Star at 344
trillion kilometers (213-1/2 trillion miles). The light that flies
through Space at a velocity of 300,000 kilometers (186,000 miles) per
second, takes thirty-six years and a half to reach us from this distant
sun: _i.e._, the luminous ray we are now receiving from Polaris has been
traveling for more than the third of a century. When you, gentle reader,
were born, the ray that arrives to-day from the Pole-Star was already
speeding on its way. In the first second after it had started it
traveled 300,000 kilometers; in the second it added another 300,000
which at once makes 600,000 kilometers; add another 300,000 kilometers
for the third second, and so on during the thirty-six years and a half.
If we tried to arrange the number 300,000 (which represents the distance
accomplished in one second) in superposed rows, as if for an addition
sum, as many times as is necessary to obtain the distance that
separates the Pole-Star from our Earth, the necessary operation would
comprise 1,151,064,000 rows, and the sheet of paper required for the
setting out of such a sum would measure approximately 11,510 kilometers
(about 7,000 miles), _i.e._, almost the diameter of our terrestrial
globe, or about four times the distance from Paris to Moscow!
Is it not impossible to realize that our Sun, with its entire system, is
lost in the Heavens at such a distance from his peers in Space? At the
distance of the least remote of the stars he would appear as one of the
smallest.
* * * * *
The nearest star to us is [alpha] of the Centaur, of first magnitude, a
neighbor of the South Pole, invisible in our latitudes. Its distance is
275,000 radii of the terrestrial orbit, _i.e._, 275,000 times 149
million kilometers, which gives 41 trillions, or 41,000 milliards of
kilometers (= 25-1/2 trillion miles). [A milliard = 1,000 millions, the
French billion. A trillion = 1,000 milliards, or a million millions, the
English billion. The _French_ nomenclature has been retained by the
translator.] At a speed of 300,000 kilometers (186,000 miles) per second
the light takes four years to come from thence. It is a fine double
star.
The next nearest star after this is a little orb invisible to the
unaided eye. It has no name, and stands as No. 21,185 in the Catalogue
of Lalande. It almost attains the seventh magnitude (6.8). Its distance
is 64 trillion kilometers (39-1/2 trillion miles).
The third of which the distance has been measured is the small star in
Cygnus, already referred to in Chapter II, in describing the
Constellations. Its distance is 69 trillion kilometers (42-1/2 trillion
miles). This, too, is a double star. The light takes seven years to
reach us.
As we have seen, the fine stars Sirius, Procyon, Aldebaran, Altaïr,
Vega, and Capella are more remote.
Our solar system is thus very isolated in the vastness of Infinitude.
The latest known planet of our system, Neptune, performs its revolutions
in space at 4 milliards, 470 million kilometers (2,771,400,000 miles)
from our Sun. Even this is a respectable distance! But beyond this
world, an immense gulf, almost a void abyss, extends to the nearest
star, [alpha] of the Centaur. Between Neptune and Centauris there is no
star to cheer the black and cold solitude of the immense vacuum. One or
two unknown planets, some wandering comets, and swarms of meteors,
doubtless traverse those unknown spaces, but all invisible to us.
Later on we will discuss the methods that have been employed in
measuring these distances. Let us now continue our description.
* * * * *
Now that we have some notion of the distance of the stars we must
approach them with the telescope, and compare them one with another.
Let us, for example, get close to Sirius: in this star we admire a sun
that is several times heavier than our own, and of much greater mass,
accompanied by a second sun that revolves round it in fifty years. Its
light is exceedingly white, and it notably burns with hydrogen flames,
like Vega and Altaïr.
Now let us approach Arcturus, Capella, Aldebaran: these are yellow stars
with golden rays, like our Sun, and the vapor of iron, of sodium, and of
many other metals can be identified in their spectrum. These stars are
older than the first, and the ruddy ones, such as Antares, Betelgeuse,
[alpha] of Hercules, are still older; several of them are variable, and
are on their way to final extinction.
The Heavens afford us a perennial store of treasure, wherein the
thinker, poet or artist can find inexhaustible subjects of
contemplation.
You have heard of the celestial jewels, the diamonds, rubies, emeralds,
sapphires, topazes, and other precious stones of the sidereal casket.
These marvels are met with especially among the double stars.
Our Sun, white and solitary, gives no idea of the real aspect of some of
its brothers in Infinitude. There are as many different types as there
are suns!
Stars, you will think, are like individuals: each has its distinct
characteristics: no two are comparable. And indeed this reflection is
justified. While human vanity does homage to Phoebus, divine King of
the Heavens, other suns of still greater magnificence form groups of two
or three splendid orbs, which roll the prodigious combinations of their
double, triple, or multiple systems through space, pouring on to the
worlds that accompany them a flood of changing light, now blue, now red,
now violet, etc.
In the inexhaustible variety of Creation there exist Suns that are
united in pairs, bound by a common destiny, cradled in the same
attraction, and often colored in the most delicate and entrancing shades
conceivable. Here will be a dazzling ruby, its glowing color shedding
joy; there a deep blue sapphire of tender tone; beyond, the finest
emeralds, hue of hope. Diamonds of translucent purity and whiteness
sparkle from the abyss, and shed their penetrating light into the vast
space. What splendors are scattered broadcast over the sky! what
profusion!
To the naked eye, the groups appear like ordinary stars, mere luminous
points of greater or less brilliancy; but the telescope soon discovers
the beauty of these systems; the star is duplicated into two distinct
suns, in close proximity. These groups of two or several suns are not
merely due to an effect of perspective--_i.e._, the presence of two or
more stars in our line of sight; as a rule they constitute real physical
systems, and these suns, associated in a common lot, rotate round one
another in a more or less rapid period, that varies for each system.
One of the most splendid of these _double stars_, and at the same time
one of the easiest to perceive, is [zeta] in the Great Bear, or Mizar,
mentioned above in describing this constellation. It has no contrasting
colors, but exactly resembles twin diamonds of the finest water, which
fascinate the gaze, even through a small objective.
Its components are of the second and fourth magnitudes, their distance =
14"[6]. Some idea of their appearance in a small telescope may be
obtained from the subjoined figure (Fig. 17).
Another very brilliant pair is Castor. Magnitudes second and third.
Distance 5.6"". Very easy to observe. [gamma] in the Virgin resolves
into two splendid diamonds of third magnitude. Distance, 5.0". Another
double star is [gamma] of the Ram, of fourth magnitude. Distance, 8.9".
[Illustration: FIG. 17.--The double star Mizar.]
And here are two that are even more curious by reason of their coloring:
[gamma] in Andromeda, composed of a fine orange star, and one
emerald-green, which again is accompanied by a tiny comrade of the
deepest blue. This group in a good telescope is most attractive.
Magnitudes, second and fifth. Distance, 10".
[beta] of the Swan, or Albireo, referred to in the last chapter, has
been analyzed into two stars: one golden-yellow, the other sapphire.
Magnitudes, third and fifth. Distance, 34". [alpha] of the Greyhounds,
known also as the Heart of Charles II, is golden-yellow and lilac.
Magnitudes, third and fifth. Distance 20".[7]
[alpha] of Hercules revolves a splendid emerald and a ruby in the skies;
[zeta] of the Lyre exhibits a yellow and a green star; Rigel, an
electric sun, and a small sapphire; Antares is ruddy and emerald-green;
[eta] of Perseus resolves into a burning red star, and one smaller that
is deep blue, and so on.
* * * * *
These exquisite double stars revolve in gracious and splendid couples
around one another, as in some majestic valse, marrying their
multi-colored fires in the midst of the starry firmament.
Here, we constantly receive a pure and dazzling white light from our
burning luminary. Its ray, indeed, contains the potentiality of every
conceivable color, but picture the fantastic illumination of the worlds
that gravitate round these multiple and colored suns as they shed floods
of blue and roseate, red, or orange light around them! What a fairy
spectacle must life present upon these distant universes!
Let us suppose that we inhabit a planet illuminated by two suns, one
blue, the other red.
It is morning. The sapphire sun climbs slowly up the Heavens, coloring
the atmosphere with a somber and almost melancholy hue. The blue disk
attains the zenith, and is beginning its descent toward the West, when
the East lights up with the flames of a scarlet sun, which in its turn
ascends the heights of the firmament. The West is plunged in the
penumbra of the rays of the blue sun, while the East is illuminated with
the purple and burning rays of the ruby orb.
The first sun is setting when the second noon shines for the inhabitants
of this strange world. But the red sun, too, accomplishes the law of its
destiny. Hardly has it disappeared in the conflagration of its last
rays, with which the West is flushed, when the blue orb reappears on the
opposite side, shedding a pale azure light upon the world it
illuminates, which knows no night. And thus these two suns fraternize in
the Heavens over the common task of renewing a thousand effects of
extra-terrestrial light for the globes that are subject to their
variations.
Scarlet, indigo, green, and golden suns; pearly and multi-colored Moons;
are these not fairy visions, dazzling to our poor sight, condemned while
here below to see and know but one white Sun?
As we have learned, there are not only double, but triple, and also
multiple stars. One of the finest ternary systems is that of [gamma] in
Andromeda, above mentioned. Its large star is orange, its second green,
its third blue, but the two last are in close juxtaposition, and a
powerful telescope is needed to separate them. A triple star more easy
to observe is [zeta] of Cancer, composed of three orbs of fifth
magnitude, at a distance of 1" and 5"; the first two revolve round their
common center of gravity in fifty-nine years, the third takes over three
hundred years. The preceding figure shows this system in a fairly
powerful objective (Fig. 18).
[Illustration: FIG. 18.--Triple star [zeta] in Cancer.]
In the Lyre, a little above the dazzling Vega, [epsilon] is of fourth
magnitude, which seems a little elongated to the unaided eye, and can
even be analyzed into two contiguous stars by very sharp sight. But on
examining this attractive pair with a small glass, it is further obvious
that each of these stars is double; so that they form a splendid
quadruple system of two couples (Fig. 19): one of fifth and a half and
sixth magnitudes, at a distance of 2.4", the other of sixth and
seventh, 3.2" distant. The distance between the two pairs is 207".
[Illustration: FIG. 19.--Quadruple star [epsilon] of the Lyre.]
In speaking of Orion, we referred to the marvelous star [theta] situated
in the no less famous Nebula, below the Belt; this star forms a
dazzling sextuple system, in the very heart of the nebula (Fig. 20). How
different to our Sun, sailing through Space in modest isolation!
Be it noted that all these stars are animated by prodigious motions that
impel them in every direction.
[Illustration: FIG. 20.--Sextuple star [theta] in the Nebula of Orion.]
There are no fixed stars. On every side throughout Infinity, the burning
suns--enormous globes, blazing centers of light and heat--are flying at
giddy speed toward an unknown goal, traversing millions of miles each
day, crossing century by century such vast spaces as are inconceivable
to the human intellect.
If the stars appear motionless to us, it is because they are so remote,
their secular movements being only manifested on the celestial sphere by
imperceptible displacements. But in reality these suns are in perpetual
commotion in the abysses of the Heavens, which they quicken with an
extraordinary animation.
These perpetual and cumulative motions must eventually modify the aspect
of the Constellations: but these changes will only take effect very
slowly; and for thousands and thousands of years longer the heroes and
heroines of mythology will keep their respective places in the Heavens,
and reign undisturbed beneath the starry vault.
Examination of these star motions reveals the fact that our Sun is
plunging with all his system (the Earth included) toward the
Constellation of Hercules. We are changing our position every moment: in
an hour we shall be 70,000 kilometers (43,500 miles) farther than we are
at present. The Sun and the Earth will never again traverse the space
they have just left, and which they have deserted forever.
And here let us pause for an instant to consider the _variable stars_.
Our Sun, which is constant and uniform in its light, does not set the
type of all the stars. A great number of them are variable--either
periodically, in regular cycles--or irregularly.
We are already acquainted with the variations of Algol, in Perseus, due
to its partial eclipse by a dark globe gravitating in the line of our
vision. There are several others of the same type: these are not,
properly speaking, variable stars. But there are many others the
intrinsic light of which undergoes actual variations.
In order to realize this, let us imagine that our Earth belongs to such
a sun, for example, to a star in the southern constellation of the
Whale, indicated by the letter [omicron], which has been named the
"wonderful" (Mira Ceti). Our new sun is shining to-day with a dazzling
light, shedding the gladness of his joyous beams upon nature and in our
hearts. For two months we admire the superb orb, sparkling in the azure
illuminated with its radiance. Then of a sudden, its light fades, and
diminishes in intensity, though the sky remains clear. Imperceptibly,
our fine sun darkens; the atmosphere becomes sad and dull, there is an
anticipation of universal death. For five long months our world is
plunged in a kind of penumbra; all nature is saddened in the general
woe.
But while we are bewailing the cruelty of our lot, our cherished
luminary revives. The intensity of its light increases slowly. Its
brilliancy augments, and finally, at the end of three months, it has
recovered its former splendors, and showers its bright beams upon our
world, flooding it with joy. But--we must not rejoice too quickly! This
splendid blaze will not endure. The flaming star will pale once more;
fade back to its minimum; and then again revive. Such is the nature of
this capricious sun. It varies in three hundred and thirty-one days, and
from yellow at the maximum, turns red at the minimum. This star, Mira
Ceti, which is one of the most curious of its type, varies from the
second to the ninth magnitudes: we cite it as one example; hundreds of
others might be instanced.
Thus the sky is no black curtain dotted with brilliant points, no empty
desert, silent and monotonous. It is a prodigious theater on which the
most fantastic plays are continually being acted. Only--there are no
spectators.
Again, we must note the _temporary stars_, which shine for a certain
time, and then die out rapidly. Such was the star in Cassiopeia, in
1572, the light of which exceeded Sirius in its visibility in full
daylight, burning for five months with unparalleled splendor, dominating
all other stars of first magnitude; after which it died out gradually,
disappearing at the end of seventeen months, to the terror of the
peoples, who saw in it the harbinger of the world's end: that of 1604,
in the Constellation of the Serpent, which shone for a year; of 1866, of
second magnitude, in the Northern Crown, which appeared for a few weeks
only; of 1876, in the Swan; of 1885, in the Nebula of Andromeda; of
1891, in the Charioteer; and quite recently, of 1901, in Perseus.
These temporary stars, which appear spontaneously to the observers on
the Earth, and quickly vanish again, are doubtless due to collisions,
conflagrations, or celestial cataclysms. But we only see them long after
the epoch at which the phenomena occurred, years upon years, and
centuries ago. For instance, the conflagration photographed by the
author in 1901, in Perseus, must have occurred in the time of Queen
Elizabeth. It has taken all this time for the rays of light to reach us.
* * * * *
The Heavens are full of surprises, on which we can bestow but a fleeting
glance within these limits. They present a field of infinite variety.
Who has not noticed the Milky Way, the pale belt that traverses the
entire firmament and is so luminous on clear evenings in the
Constellations of the Swan and the Lyre? It is indeed a swarm of stars.
Each is individually too small to excite our retina, but as a whole,
curiously enough, they are perfectly visible. With opera-glasses we
divine the starry constitution: a small telescope shows us marvels.
Eighteen millions of stars were counted there with the gauges of William
Herschel.
Now this Milky Way is a symbol, not of the Universe, but of the
Universes that succeed each other through the vast spaces to Infinity.
Our Sun is a star of the Milky Way. It surrounds us like a great circle,
and if the Earth were transparent, we should see it pass beneath our
feet as well as over our heads. It consists of a very considerable mass
of star-clusters, varying greatly in extent and number, some projected
in front of others, while the whole forms an agglomeration.
[Illustration: FIG. 21.--The Star-Cluster in Hercules.]
Among this mass of star-groups, several thousands of which are already
known to us, we will select one of the most curious, the Cluster in
Hercules, which can be distinguished with the unaided eye, between the
stars [eta] and [zeta] of that constellation. Many photographs of it
have been taken in the author's observatory at Juvisy, showing some
thousands of stars; and one of these is reproduced in the accompanying
figure (Fig. 21). Is it not a veritable universe?
[Illustration: FIG. 22.--The Star-Cluster in the Centaur.]
Another of the most beautiful, on account of its regularity, is that of
the Centaur (Fig. 22).
These groups often assume the most extraordinary shapes in the
telescope, such as crowns, fishes, crabs, open mouths, birds with
outspread wings, etc.
We must also note the _gaseous nebulæ_, universes in the making,
_e.g._, the famous Nebula in Orion, of which we obtained some notion a
while ago in connection with its sextuple star: and also that in
Andromeda (Fig. 23).
[Illustration: FIG. 23.--The Nebula in Andromeda.]
[Illustration: FIG. 24.--Nebula in the Greyhounds.]
Perhaps the most marvelous of all is that of the Greyhounds, which
evolves in gigantic spirals round a dazzling focus, and then loses
itself far off in the recesses of space. Fig. 24 gives a picture of it.
[Illustration: FIG. 25.--The Pleiades.]
Without going thus far, and penetrating into telescopic depths, my
readers can get some notion of these star-clusters with the help of a
small telescope or opera-glasses, or even with the unaided eye, by
looking at the beautiful group of the Pleiades, already familiar to us
on another page, and using it as a test of vision. The little map
subjoined (Fig. 25) will be an assistance in recognizing them, and in
estimating their magnitudes, which are in the following order:
Alcyone 3.0.
Electra 4.5.
Atlas 4.6.
Maia 5.0.
Merope 5.5.
Taygeta 5.8.
Pleione 6.3.
Celæno 6.5.
Asterope 6.8.
Good eyes distinguish the first six, sharp sight detects the three
others.
In the times of the ancient Greeks, seven were accounted of equal
brilliancy, and the poets related that the seventh star had fled at the
time of the Trojan War. Ovid adds that she was mortified at not being
embraced by a god, as were her six sisters. It is probable that only the
best sight could then distinguish Pleione, as in our own day. The
angular distance from Atlas to Pleione is 5'.
The length of this republic, from Atlas and Pleione to Celæno, is 4'/23"
of time, or 1°6' of arc; the breadth, from Merope to Asterope, is
36'.[8]
In the quadrilateral, the length from Alcyone to Electra is 36', and the
breadth from Merope to Maia 25'. To us it appears as though, if the Full
Moon were placed in front of this group of nine stars, she would cover
it entirely, for to the naked eye she appears much larger than all the
Pleiades together. But this is not so. She only measures 31', less than
half the distance from Atlas to Celæno; she is hardly broader than the
distance from Alcyone to Atlas, and could pass between Merope and
Taygeta without touching either of these stars. This is a perennial and
very curious optical illusion. When the Moon passes in front of the
Pleiades, and occults them successively, it is hard to believe one's
eyes. The fact occurred, _e.g._, on July 23, 1897, during a fine
occultation observed at the author's laboratory of Juvisy (Fig. 26).
[Illustration: FIG. 26.--Occultation of the Pleiades by the Moon.]
Photography here discovers to us, not 6, 9, 12, 15, or 20 stars, but
hundreds and millions.
These are the most brilliant flowers of the celestial garden.
[Illustration: FIG. 27.--Stellar dial of the double star [gamma] of the
Virgin.]
We, alas, can but glance at them rapidly. In contemplating them we are
transported into immensities both of space and time, for the stellar
periods measured by these distant universes often overpower in their
magnitude the rapid years in which our terrestrial days are estimated.
For instance, one of the double stars we spoke of above, [gamma] of the
Virgin, sees its two components, translucent diamonds, revolve around
their common center of gravity, in one hundred and eighty years. How
many events took place in France, let us say, in a single year of this
star!--The Regency, Louis XV, Louis XVI, the Revolution, Napoleon, Louis
XVIII, Louis Philippe, the Second Republic, Napoleon III, the
Franco-German War, the Third Republic.... What revolutions here, during
a single year of this radiant pair! (Fig. 27.)
But the pageant of the Heavens is too vast, too overwhelming. We must
end our survey.
Our Milky Way, with its millions of stars, represents for us only a
portion of the Creation. The illimitable abysses of Infinitude are
peopled by other universes as vast, as imposing, as our own, which are
renewed in all directions through the depths of Space to endless
distance. Where is our little Earth? Where our Solar System? We are fain
to fold our wings, and return from the Immense and Infinite to our
floating island.
CHAPTER IV
OUR STAR THE SUN
In the incessant agitation of daily life in which we are involved by the
thousand superfluous wants of modern "civilization," one is prone to
assume that existence is complete only when it reckons to the good an
incalculable number of petty incidents, each more insignificant than the
last. Why lose time in thinking or dreaming? We must live at fever heat,
must agitate, and be infatuated for inanities, must create imaginary
desires and torments.
The thoughtful mind, prone to contemplation and admiration of the
beauties of Nature, is ill at ease in this perpetual vortex that
swallows everything--satisfaction, in a life that one has not time to
relish; love of the beautiful, that one views with indifference; it is a
whirlpool that perpetually hides Truth from us, forgotten forever at the
bottom of her well.
And why are our lives thus absorbed in merely material interests? To
satisfy our pride and vanity! To make ourselves slaves to chimeras! If
the Moon were inhabited, and if her denizens could see us plainly
enough to note and analyze the details of human existence on the surface
of our planet, it would be curious and perhaps a little humiliating for
us, to see their statistics. What! we should say, is this the sum of our
lives? Is it for this that we struggle, and suffer, and die? Truly it is
futile to give ourselves such trouble.
And yet the remedy is simple, within the power of every one; but one
does not think of it just because it is too easy, although it has the
immense advantage of lifting us out of the miseries of this weary world
toward the inexpressible happiness that must always awaken in us with
the knowledge of the Truth: we need only open our eyes to see, and to
look out. Only--one hardly ever thinks of it, and it is easier to let
one's self be blinded by the illusion and false glamor of appearances.
Think what it would be to consecrate an hour each day to voluntary
participation in the harmonious Choir of Nature, to raise one's eyes
toward the Heavens, to share the lessons taught by the Pageant of the
Universe! But, no: there is no time, no time for the intellectual life,
no time to become attached to real interests, no time to pursue them.
Among the objects marshaled for us in the immense spectacle of Nature,
nothing without exception has struck the admiration and attention of
man as much as the Sun, the God of Light, the fecundating orb, without
which our planet and its life would never have issued from nonentity,
_the visible image of the invisible god_, as said Cicero, and the poets
of antiquity. And yet how many beyond the circle of those likely to read
these pages know that this Sun is a star in the Milky Way, and that
every star is a sun? How many take any account of the reality and
grandeur of the Universe? Inquire, and you will find that the number of
people who have any notion, however rudimentary, of its construction, is
singularly restricted. Humanity is content to vegetate, much after the
fashion of a race of moles.
Henceforward, you will know that you are living in the rays of a star,
which, from its proximity, we term a sun. To the inhabitants of other
systems of worlds, our splendid Sun is only a more or less brilliant,
luminous point, according as the spot from which it is observed is
nearer or farther off. But to us its "terrestrial" importance renders it
particularly precious; we forget all the sister stars on its account,
and even the most ignorant hail it with enthusiasm without exactly
knowing what its rôle in the universe may be, simply because they feel
that they depend on it, and that without it life would become extinct on
this globe. Yes, it is the beneficent rays of the Sun that shed upon
our Earth the floods of light and heat to which Life owes its existence
and its perpetual propagation.
Hail, vast Sun! a little star in Infinitude, but for us a colossal and
portentous luminary. Hail, divine Benefactor! How should we not adore,
when we owe him the glow of the warm and cheery days of summer, the
gentle caresses by which his rays touch the undulating ears, and gild
them with the touch? The Sun sustains our globe in Space, and keeps it
within his rays by the mysteriously powerful and delicate cords of
attraction. It is the Sun that we inhale from the embalmed corollas of
the flowers that uplift their gracious heads toward his light, and
reflect his splendors back to us. It is the Sun that sparkles in the
foam of the merry wine; that charms our gaze in those first days of
spring, when the home of the human race is adorned with all the charms
of verdant and flowering youth. Everywhere we find the Sun; everywhere
we recognize his work, extending from the infinitely great to the
infinitely little. We bow to his might, and admire his power. When in
the sad winter day he disappears behind the snowy eaves, we think his
fiery globe will never rise to mitigate the short December days which
are alleviated with his languid beams.
April restores him to superb majesty, and our hearts are filled with
hope in the illumination of those beauteous, sunny hours.
* * * * *
Our celestial journey carried us far indeed from our own Solar System.
Guided by the penetrating eye of the telescope, we reached such distant
creations that we lost sight of our cherished luminary.
But we remember that he burns yonder, in the midst of the pale cosmic
cloud we term the Milky Way. Let us approach him, now that we have
visited the Isles of Light in the Celestial Ocean; let us traverse the
vast plains strewn with the burning gold of the Suns of the Infinite.
We embark upon a ray of light, and glide rapidly to the portals of our
Universe. Soon we perceive a tiny speck, scintillating feebly in the
depths of Space, and recognize it as our own celestial quarters. This
little star shines like the head of a gold pin, and increases in size as
we advance toward it. We traverse a few more trillion miles in our rapid
course, and it shines out like a fine star of the first magnitude. It
grows larger and larger. Soon we divine that it is our humble Earth that
is shining before us, and gladly alight upon her. In future we shall not
quit our own province of the Celestial Kingdom, but will enter into
relations with this solar family, which interests us the more in that it
affects us so closely.
[Illustration: FIG. 28.--Comparative sizes of the Sun and Earth.]
The Sun, which is manifested to us as a fine white disk at noon, while
it is fiery red in the evening, at its setting, is an immense globe,
whose colossal dimensions surpass those of our terrestrial atom beyond
all conceivable proportion.
In diameter, it is, in effect, 108-1/2 times as large as the Earth; that
is to say, if our planet be represented by a globe 1 meter in diameter,
the Sun would figure as a sphere 108-1/2 meters across. This is shown on
the accompanying figure (Fig. 28), which is in exact proportion.
If our world were set down upon the Sun, with all its magnificence, all
its wealth, its mountains, its seas, its monuments, and its inhabitants,
it would only be an imperceptible speck. It would occupy less space in
the central orb than one grain in a grenade. If the Earth were placed in
the center of the Sun, with the Moon still revolving round it at her
proper distance of 384,000 kilometers (238,500 miles), only half the
solar surface would be covered.
In volume the Sun is 1,280,000 times vaster than our abode, and 324,000
times heavier in mass. That the giant only appears to us as a small
though very brilliant disk, is solely on account of its distance. Its
apparent dimensions by no means reveal its majestic proportions to us.
When observed with astronomical instruments, or photographed, we
discover that its surface is not smooth, as might be supposed, but
granulated, presenting a number of luminous points dispersed over a
more somber background. These granulations are somewhat like the pores
of a fruit, _e.g._, a fine orange, the color of which recalls the hue of
the Sun when it sinks in the evening, and prepares to plunge us into
darkness. At times these pores open under the influence of disturbances
that arise upon the solar surface, and give birth to a Sun-Spot. For
centuries scientists and lay people alike refused to admit the existence
of these spots, regarding them as so many blemishes upon the King of the
Heavens. Was not the Sun the emblem of inviolable purity? To find any
defect in him were to do him grievous injury. Since the orb of day was
incorruptible, those who threw doubt on his immaculate splendor were
fools and idiots. And so when Scheiner, one of the first who studied the
solar spots with the telescope, published the result of his experiments
in 1610, no one would believe his statements.
Yet, from the observations of Galileo and other astronomers, it became
necessary to accept the evidence, and stranger still to recognize that
it is by these very spots that we are enabled to study the physical
constitution of the Sun.
They are generally rounded or oval in shape, and exhibit two distinct
parts; first, the central portion, which is black, and is called the
_nucleus_, or _umbra_; second, a clearer region, half shaded, which has
received the name of _penumbra_. These parts are sharply defined in
outline; the penumbra is gray, the nucleus looks black in relation to
the dazzling brilliancy of the solar surface; but as a matter of fact it
radiates a light 2,000 times superior in intensity to that of the full
moon.
[Illustration: FIG. 29.--Direct photograph of the Sun.]
Some idea of the aspect of these spots may be obtained from the
accompanying reproduction of a photograph of the Sun (taken September 8,
1898, at the author's observatory at Juvisy), and from the detailed
drawing of the large spot that broke out some days later (September 13),
crossed by a bridge, and furrowed with flames. As a rule, the spots
undergo rapid transformations.
[Illustration: FIG. 30.--Telescopic aspect of a Sun-Spot.]
These spots, which appear of insignificant dimensions to the observers
on the Earth, are in reality absolutely gigantic. Some that have been
measured are ten times as large as the Earth's diameter, _i.e._, 120,000
kilometers (74,500 miles).
Sometimes the spots are so large that they can be seen with the unaided
eye (protected with black or dark-blue glasses). They are not formed
instantaneously, but are heralded by a vast commotion on the solar
surface, exhibiting, as it were, luminous waves or _faculæ_. Out of this
agitation arises a little spot, that is usually round, and enlarges
progressively to reach a maximum, after which it diminishes, with
frequent segmentation and shrinkage. Some are visible only for a few
days; others last for months. Some appear, only to be instantly
swallowed in the boiling turmoil of the flaming orb. Sometimes, again,
white incandescent waves emerge, and seem to throw luminous bridges
across the central umbra. As a rule the spots are not very profound.
They are funnel-shaped depressions, inferior in depth to the diameter of
the Earth, which, as we have seen, is 108 times smaller than that of the
Sun.
* * * * *
The Sun-Spots are not devoid of motion, and from their movements we
learn that the radiant orb revolves upon itself in about twenty-five
days. This rotation was determined in 1611, by Galileo, who, while
observing the spots, saw that they traversed the solar disk from east
to west, following lines that are oblique to the plane of the ecliptic,
and that they disappear at the western border fourteen days after their
arrival at the eastern edge. Sometimes the same spot, after being
invisible for fourteen days, reappears upon the eastern edge, where it
was observed twenty-eight days previously. It progresses toward the
center of the Sun, which is reached in seven days, disappears anew in
the west, and continues its journey on the hemisphere opposed to us, to
reappear under observation two weeks later, if it has not meantime been
extinguished. This observation proves that the Sun revolves upon itself.
The reappearance of the spots occurs in about twenty-seven days, because
the Earth is not stationary, and in its movement round the burning
focus, a motion effected in the same direction as the solar rotation,
the spots are still visible two and a half days after they disappeared
from the point at which they had been twenty-five days previously. In
reality, the rotation of the Sun occupies twenty-five and a half days,
but strangely enough this globe _does not rotate in one uniform period_,
like the Earth; the rotation periods, or movements of the different
parts of the solar surface, diminish from the Sun's equator toward its
poles. The period is twenty-five days at the equator, twenty-six at the
twenty-fourth degree of latitude, north or south, twenty-seven at the
thirty-seventh degree, twenty-eight at the forty-eighth. The spots are
usually formed between the equator and this latitude, more especially
between the tenth and thirtieth degrees. They have never been seen round
the poles.
Toward the edges of the Sun, again, are very brilliant and highly
luminous regions, which generally surround the spots, and have been
termed _faculæ_ (_facula_, a little torch). These faculæ, which
frequently occupy a very extensive surface, seem to be the seat of
formidable commotions that incessantly revolutionize the face of our
monarch, often, as we said, preceding the spots. They can be detected
right up to the poles.
Our Sun, that appears so calm and majestic, is in reality the seat of
fierce conflagrations. Volcanic eruptions, the most appalling storms,
the worst cataclysms that sometimes disturb our little world, are gentle
zephyrs compared with the solar tempests that engender clouds of fire
capable at one burst of engulfing globes of the dimensions of our
planet.
To compare terrestrial volcanoes with solar eruptions is like comparing
the modest night-light that consumes a midge with the flames of the fire
that destroys a town.
The solar spots vary in a fairly regular period of eleven to twelve
years. In certain years, _e.g._, 1893, they are vast, numerous and
frequent; in other years, _e.g._, 1901, they are few and insignificant.
The statistics are very carefully preserved. Here, for instance, is the
surface showing sun-spots expressed in millionths of the extent of the
visible solar surface:
1889 78
1890 99
1891 569
1892 1,214
1893 1,464
1895 974
1896 543
1897 514
1898 375
1899 111
1900 75
1901 29
1902 62
The years 1889 and 1901 were _minima_; the year 1893 a _maximum_.
It is a curious fact that terrestrial magnetism and the boreal auroras
exhibit an oscillation parallel to that of the solar spots, and
apparently the same occurs with regard to temperature.
We must regard our sun as a globe of gas in a state of combustion,
burning at high temperature, and giving off a prodigious amount of heat
and light. The dazzling surface of this globe is called a _photosphere_
(light sphere). It is in perpetual motion, like the waves of an ocean of
fire, whose roseate and transparent flames measure some 15,000
kilometers (9,300 miles) in height. This stratum of rose-colored flames
has received the name of _chromosphere_ (color sphere). It is
transparent; it is not directly visible, but is seen only during the
total eclipses of the Sun, when the dazzling disk of that luminary is
entirely concealed by the Moon; or with the aid of the spectroscope. The
part of the Sun that we see is its luminous surface, or photosphere.
From this agitated surface there is a constant ejection of gigantic
eruptions, immense jets of flame, geysers of fire, projected at a
terrific speed to prodigious heights.
For years astronomers were greatly perplexed as to the nature of these
incandescent masses, known as prominences, which shot out like
fireworks, and were only visible during the total eclipses of the Sun.
But now, thanks to an ingenious invention of Janssen and Lockyer, these
eruptions can be observed every day in the spectroscope, and have been
registered since 1868, more particularly in Rome and in Catania, where
the Society of Spectroscopists was founded with this especial object,
and publishes monthly bulletins in statistics of the health of the Sun.
These prominences assume all imaginable forms, and often resemble our
own storm-clouds; they rise above the chromosphere with incredible
velocity, often exceeding 200 kilometers (124 miles) per second, and
are carried up to the amazing height of 300,000 kilometers (186,000
miles).
[Illustration: FIG. 31.--Rose-colored solar flames 228,000 kilometers
(141,500 miles) in height, _i.e._, 18 times the diameter of the Earth.]
The Sun is surrounded with these enormous flames on every side;
sometimes they shoot out into space like splendid curving roseate
plumes; at others they rear their luminous heads in the Heavens, like
the cleft and waving leaves of giant palm-trees. Having illustrated a
remarkable type of solar spot, it is interesting to submit to the reader
a precise observation of these curious solar flames. That reproduced
here was observed in Rome, January 30, 1885. It measured 228,000
kilometers (141,500 miles) in height, eighteen times the diameter of the
earth (represented alongside in its relative magnitude). (Fig. 31.)
Solar eruptions have been seen to reach, in a few minutes, a height of
more than 100,000 kilometers (62,000 miles), and then to fall back in a
flaming torrent into that burning and inextinguishable ocean.
Observation, in conjunction with spectral analysis, shows these
prominences to be due to formidable explosions produced within the
actual substance of the Sun, and projecting masses of incandescent
hydrogen into space with considerable force.
Nor is this all. During an eclipse one sees around the black disk of the
Moon as it passes in front of the Sun and intercepts its light, a
brilliant and rosy aureole with long, luminous, branching feathers
streaming out, like aigrettes, which extend a very considerable distance
from the solar surface. This aureole, the nature of which is still
unknown to us, has received the name of _corona_. It is a sort of
immense atmosphere, extremely rarefied. Our superb torch, accordingly,
is a brazier of unparalleled activity--a globe of gas, agitated by
phenomenal tempests whose flaming streamers extend afar. The smallest of
these flames is so potent that it would swallow up our world at a single
breath, like the bombs shot out by Vesuvius, that fall back within the
crater.
What now is the real heat of this incandescent focus? The most accurate
researches estimate the temperature of the surface of the Sun at
7,000°C. The internal temperature must be considerably higher. A
crucible of molten iron poured out upon the Sun would be as a stream of
ice and snow.
We can form some idea of this calorific force by making certain
comparisons. Thus, the heat given out appears to be equal to that which
would be emitted by a colossal globe of the same dimensions (that is, as
voluminous as twelve hundred and eighty thousand terrestrial globes),
entirely covered with a layer of incandescent coal 28 kilometers (18
miles) in depth, all burning at equal combustion. The heat emitted by
the Sun, at each second, is equal to that which would result from the
combustion of eleven quadrillions six hundred thousand milliards of tons
of coal, all burning together. This same heat would bring to the boil in
an hour, two trillions nine hundred milliards of cubic kilometers of
water at freezing-point.
Our little planet, gravitating at 149,000,000 kilometers (93,000,000
miles) from the Sun, arrests on the way, and utilizes, only the half of
a milliard part of this total radiation.
How is this heat maintained? One of the principal causes of the heat of
the Sun is its condensation. According to all probabilities, the solar
globe represents for us the nucleus of a vast nebula, that extended in
primitive times beyond the orbit of Neptune, and which in its
contraction has finally produced this central focus. In virtue of the
law of transformation of motion into heat, this condensation, which has
not yet reached its limit, suffices to raise this colossal globe to its
level of temperature, and to maintain it there for millions of years. In
addition, a substantial number of meteors is forever falling into it.
This furnace is a true pandemonium.
The Sun weighs three hundred and twenty-four thousand times more than
the Earth--that is to say, eighteen hundred and seventy octillions of
kilograms:
1,870,000,000,000,000,000,000,000,000,000
(1,842,364,532,019,704,433,497,536,945 tons).
In Chapter XI we shall explain the methods by which it has been found
possible to weigh the Sun and determine its exact distance.
* * * * *
I trust these figures will convey some notion of the importance and
nature of the Sun, the stupendous orb on whose rays our very existence
depends. Its apparent dimension (which is only half a degree, 32', and
would be hidden from sight, like that of the full moon, which is about
the same, by the tip of the little finger held out at arm's length),
represents, as we have seen, a real dimension that is colossal, _i.e._,
1,383,000 kilometers (more than 857,000 miles), and this is owing to the
enormous distance that separates us from it. This distance of
149,000,000 kilometers (93,000,000 miles) is sufficiently hard to
appreciate. Let us say that 11,640 terrestrial globes would be required
to throw a bridge from here to the Sun, while 30 would suffice from the
Earth to the Moon. The Moon is 388 times nearer to us than the Sun. We
may perhaps conceive of this distance by calculating that a train,
moving at constant speed of 1 kilometer (0.6214 mile) a minute, would
take 149,000,000 minutes, that is to say 103,472 days, or 283 years, to
cross the distance that separates us from this orb. Given the normal
duration of life, neither the travelers who set out for the Sun, nor
their children, nor their grandchildren, would arrive there: only the
seventh generation would reach the goal, and only the fourteenth could
bring us back news of it.
Children often cry for the Moon. If one of these inquisitive little
beings could stretch out its arms to touch the Sun, and burn its fingers
there, it would not feel the burn for one hundred and sixty-seven years
(when it would no longer be an infant), for the nervous impulse of
sensation can only be transmitted from the ends of the fingers to the
brain at a velocity of 28 meters per second.
'Tis long. A cannon-ball would reach the Sun in ten years. Light, that
rapid arrow that flies through space at a velocity of 300,000 kilometers
(186,000 miles per second), takes only eight minutes seventeen seconds
to traverse this distance.
* * * * *
This brilliant Sun is not only sovereign of the Earth; he is also the
head of a vast planetary system.
The orbs that circle round the Sun are opaque bodies, spherical in
shape, receiving their light and heat from the central star, on which
they absolutely depend. The name of planets given to them signifies
"wandering" stars. If you observe the Heavens on a fine starry night,
and are sufficiently acquainted with the principal stars of the Zodiac
as described in a preceding chapter, you may be surprised on certain
evenings to see the figure of some zodiacal constellation slightly
modified by the temporary presence of a brilliant orb perhaps surpassing
in its luminosity the finest stars of the first magnitude.
If you watch this apparition for some weeks, and examine its position
carefully in regard to the adjacent stars, you will observe that it
changes its position more or less slowly in the Heavens. These wandering
orbs, or _planets_, do not shine with intrinsic light; they are
illuminated by the Sun.
The planets, in effect, are bodies as opaque as the Earth, traveling
round the God of Day at a speed proportional to their distance. They
number eight principal orbs, and may be divided into two quite distinct
groups by which we may recognize them: the first comprises four planets,
of relatively small dimensions in comparison with those of the second
group, which are so voluminous that the least important of them is
larger than the other four put together.
In order of distance from the Sun, we first encounter:
MERCURY, VENUS, THE EARTH, AND MARS
These are the worlds that are nearest to the orb of day.
The four following, and much more remote, are, still in order of
distance:
JUPITER, SATURN, URANUS, AND NEPTUNE
This second group is separated from the first by a vast space occupied
by quite a little army of minute planets, tiny cosmic bodies, the
largest of which measures little more than 100 kilometers (62 miles) in
diameter, and the smallest some few miles only.
The planets which form these three groups represent the principal
members of the solar family. But the Sun is a patriarch, and each of his
daughters has her own children who, while obeying the paternal influence
of the fiery orb, are also obedient to the world that governs them.
These secondary asters, or _satellites_, follow the planets in their
course, and revolve round them in an ellipse, just as the others rotate
round the Sun. Every one knows the satellite of the Earth, the Moon. All
the other planets of our system have their own moons, some being even
more favored than ourselves in this respect, and having several. Mars
has two; Jupiter, five; Saturn, eight; Uranus, four; and Neptune, one
(at least as yet discovered).
In order to realize the relations between these worlds, we must
appreciate their distances by arranging them in a little table:
Distance in Distance in
Millions of Millions of
Kilometers. Miles.
Mercury 57 35
Venus 108 67
The Earth 149 93
Mars 226 140
Jupiter 775 481
Saturn 1,421 882
Uranus 2,831 1,755
Neptune 4,470 2,771
The Sun is at the center (or, more properly speaking, at the focus, for
the planets describe an ellipse) of this system, and controls them.
Neptune is thirty times farther from the Sun than the Earth. These
disparities of distance produce a vast difference in the periods of the
planetary revolutions; for while the Earth revolves round the Sun in a
year, Venus in 224 days, and Mercury in 88, Mars takes nearly 2 years to
accomplish his journey, Jupiter 12 years, Saturn 29, Uranus 84, and
Neptune 165.
Even the planets and their moons do not represent the Sun's complete
paternity. There are further, in the solar republic, certain vagabond
and irregular orbs that travel at a speed that is often most immoderate,
occasionally approaching the Sun, not to be consumed therein, but, as it
appears, to draw from its radiant source the provision of forces
necessary for their perigrinations through space. These are the
_Comets_, which pursue an extremely elongated orbit round the Sun, to
which at times they approximate very closely, at other times being
excessively distant.
And now to recapitulate our knowledge of the Solar Empire. In the first
place, we see a colossal globe of fire dominating and governing the
worlds that belong to him. Around him are grouped planets, in number
eight principal, formed of solid and obscure matter, gravitating round
the central orb. Other secondary orbs, the satellites, revolve round the
planets, which keep them within the sphere of their attraction. And
lastly, the comets, irregular celestial bodies, track the whole extent
of the great solar province. To these might be added the whirlwinds of
meteors, as it were disaggregated comets, which also circle round the
Sun, and give origin to shooting stars, when they come into collision
with the Earth.
Having now a general idea of our celestial family, and an appreciation
of the potent focus that controls it, let us make direct acquaintance
with the several members of which it is composed.
CHAPTER V
THE PLANETS
_A._--MERCURY, VENUS, THE EARTH, MARS
And now we are in the Solar System, at the center, or, better, at the
focus of which burns the immense and dazzling orb. We have appreciated
the grandeur and potency of the solar globe, whose rays spread out in
active waves that bear a fecundating illumination to the worlds that
gravitate round him; we have appreciated the distance that separates the
Sun from the Earth, the third of the planets retained within his domain,
or at least I trust that the comparisons of the times required by
certain moving objects to traverse this distance have enabled us to
conceive it.
We said that the four planets nearest to the Sun are Mercury, at a
distance of 57 million kilometers (35,000,000 miles); Venus, at 108
million (67,000,000 miles); the Earth, at 149 million (93,000,000
miles); and Mars at 226 million (140,000,000 miles). Let us begin our
planetary journey with these four stations.
MERCURY
A little above the Sun one sometimes sees, now in the West, in the
lingering shimmer of the twilight, now in the East, when the tender
roseate dawn announces the advent of a clear day, a small star of the
first magnitude which remains but a very short time above the horizon,
and then plunges back into the flaming sun. This is Mercury, the agile
and active messenger of Olympus, the god of eloquence, of medicine, of
commerce, and of thieves. One only sees him furtively, from time to
time, at the periods of his greatest elongations, either after the
setting or before the rising of the radiant orb, when he presents the
aspect of a somewhat reddish star.
This planet, like the others, shines only by the reflection of the Sun
whose illumination he receives, and as he is in close juxtaposition with
it, his light is bright enough, though his volume is inconsiderable. He
is smaller than the Earth. His revolution round the Sun being
accomplished in about three months, he passes rapidly, in a month and a
half, from one side to the other of the orb of day, and is alternately a
morning and an evening star. The ancients originally regarded it as two
separate planets; but with attentive observation, they soon perceived
its identity. In our somewhat foggy climates, it can only be discovered
once or twice a year, and then only by looking for it according to the
indications given in the astronomic almanacs.
[Illustration: FIG. 32.--Orbits of the four Planets nearest to the Sun.]
Mercury courses round the Sun at a distance of 57,000,000 kilometers
(35,000,000 miles), and accomplishes his revolution in 87 days, 23
hours, 15 minutes; _i.e._, 2 months, 27 days, 23 hours, or a little less
than three of our months. If the conditions of life are the same there
as here, the existence of the Mercurians must be four times as short as
our own. A youth of twenty, awaking to the promise of the life he is
just beginning in this world, is an octogenarian in Mercury. There the
fair sex would indeed be justified in bewailing the transitory nature of
life, and might regret the years that pass too quickly away. Perhaps,
however, they are more philosophic than with us.
[Illustration: FIG. 33.--Orbits of the four Planets farthest from the
Sun.]
The orbit of Mercury, which of course is within that of the Earth, is
not circular, but elliptical, and very eccentric, so elongated that at
certain times of the year this planet is extremely remote from the solar
focus, and receives only half as much heat and light as at the opposite
period; and, in consequence, his distance from the Earth varies
considerably.
[Illustration: FIG. 34.--Mercury near quadrature.]
This globe exhibits _phases_, discovered in the seventeenth century by
Galileo, which recall those of the Moon. They are due to the motions of
the planet round the Sun, and are invisible to the unaided eye, but with
even a small instrument, one can follow the gradations and study Mercury
under every aspect. Sometimes, again, he passes exactly in front of the
Sun, and his disk is projected like a black point upon the luminous
surface of the flaming orb. This occurred, notably, on May 10, 1891, and
November 10, 1894; and the phenomenon will recur on November 12, 1907,
and November 6, 1914.
Mercury is the least of all the worlds in our system (with the exception
of the cosmic fragments that circulate between the orbit of Mars and
that of Jupiter). His volume equals only 5/100 that of the Earth. His
diameter, in comparison with that of our planet, is in the ratio of 373
to 1,000 (a little more than 1/3) and measures 4,750 kilometers (2,946
miles). His density is the highest of all the worlds in the great solar
family, and exceeds that of our Earth by about 1/3; but weight there is
less by almost 1/2.
Mercury is enveloped in a very dense, thick atmosphere, which doubtless
sensibly tempers the solar heat, for the Sun exhibits to the Mercurians
a luminous disk about seven times more extensive than that with which we
are familiar on the Earth, and when Mercury is at perihelion (that is,
nearest to the Sun), his inhabitants receive ten times more light and
heat than we obtain at midsummer. In all probability, it would be
impossible for us to set foot on this planet without being shattered by
a sunstroke.
Yet we may well imagine that Nature's fecundity can have engendered
beings there of an organization different from our own, adapted to an
existence in the proximity of fire. What magnificent landscapes may
there be adorned with the luxuriant vegetation that develops rapidly
under an ardent and generous sun?
[Illustration: FIG. 35.--The Earth viewed from Mercury.]
Observations of Mercury are taken under great difficulties, just because
of the immediate proximity of the solar furnace; yet some have detected
patches that might be seas. In any case, these observations are
contradictory and uncertain.
Up to the present it has been impossible to determine the duration of
the rotation. Some astronomers even think that the Sun's close proximity
must have produced strong tides, that would, as it were, have
immobilized the globe of Mercury, just as the Earth has immobilized the
Moon, forcing it perpetually to present the same side to the Sun. From
the point of view of habitation, this situation would be somewhat
peculiar; perpetual day upon the illumined half, perpetual night upon
the other hemisphere, and a fairly large zone of twilight between the
two. Such a condition would indeed be different from the succession of
terrestrial days and nights.
As seen from Mercury, the Earth we inhabit would shine out in the starry
sky[9] as a magnificent orb of first magnitude, with the Moon
alongside, a faithful little companion. They should form a fine double
star, the Earth being a brilliant orb of first magnitude, and the Moon
of third, a charming couple, and admired doubtless as an enchanted and
privileged abode.
It is at midnight during the oppositions of the Earth with the Sun that
our planet is the most beautiful and brilliant, as is Jupiter for
ourselves. The constellations are the same, viewed from Mercury or from
the Earth.
But is this little solar planet inhabited? We do not yet know. We can
only reply: why not?
VENUS
When the sunset atmosphere is crimson with the glorious rays of the King
of Orbs, and all Nature assumes the brooding veil of twilight, the most
indifferent eyes are often attracted and captivated by the presence of a
star that is almost dazzling, and illuminates with its white and limpid
light the heavens darkened by the disappearance of the God of Day.
Hail, Venus, Queen of the Heavens! the "Shepherd's Star," gentle mother
of the loves, goddess of beauty, eternally adored and cherished, sung
and immortalized upon Earth, by poets and artists. Her splendid
brilliancy attracted notice from earliest antiquity, and we find her,
radiant and charming, in the works of the ancients, who erected altars
to her and adorned their poetry with her grace and beauty. Homer calls
her Callisto the Beautiful; Cicero names her Vesper, the evening star,
and Lucifer, the star of the morning--for it was with this divinity as
with Mercury. For a long while she was regarded as two separate planets,
and it was only when it came to be observed that the evening and the
morning star were always in periodic succession, that the identity of
the orb was recognized.
Her radiant splendor created her mythological personality, just as the
agility of Mercury created that of the messenger of the gods.
We do not see her aerial chariot in the Heavens drawn by a flight of
doves with white and fluttering wings, but we follow the lustrous orb
led on through space by solar attraction. And in the beautiful evenings
when she is at her greatest distance from our Sun, the whole world
admires this white and dazzling Venus reigning as sovereign over our
twilight[10] for hours after sunset, and in addition to the _savants_
who are practically occupied with astronomy, millions of eyes are raised
to this celestial splendor, and for a moment millions of human beings
feel some curiosity about the mysteries of the Infinite. The brutalities
of daily life would fain petrify our dreams, but thought is not yet
stifled to the point of checking all aspirations after eternal truth,
and when we gaze at the starry sky it is hard not to ask ourselves the
nature of those other worlds, and the place occupied by our own planet
in the vast concert of sidereal harmony.
[Illustration: FIG. 36.--The Evening Star.]
Even through a small telescope, Venus offers remarkable phases.
[Illustration: FIG. 37.--Successive phases of Venus.]
Fig. 37 gives some notion of the succession of these, and of the
planet's variations in magnitude during its journey round the Sun.
Imagine it to be rotating in a year of 224 days, 16 hours, 49 minutes, 8
seconds at a distance of 108 million kilometers (67,000,000 miles), the
Earth being at 149 million kilometers (93,000,000 miles). Like Mercury,
at certain periods it passes between the Sun and ourselves, and as its
illuminated hemisphere is of course turned toward the orb of day, we at
those times perceive only a sharp and very luminous crescent. At such
periods Venus is entirely, so to say, against the Sun, and presents to
us her greatest apparent dimension (Fig. 38). Sometimes, again, like
Mercury, she passes immediately in front of the Sun, forming a perfectly
round black spot; this happened on December 8, 1874, and December 6,
1882; and will recur on June 7, 2004, and June 5, 2012. These transits
have been utilized in celestial geometry in measuring the distance of
the Sun.
You will readily divine that the distance of Venus varies considerably
according to her position in relation to the Earth: when she is between
the Sun and ourselves she is nearest to our world; but it is just at
those times that we see least of her surface, because she exhibits to us
only a slender crescent. Terrestrial astronomers are accordingly very
badly placed for the study of her physical constitution. The best
observations can be made when she is situated to right or left of the
Sun, and shows us about half her illuminated disk--during the day for
choice, because at night there is too much irradiation from her dazzling
light.
These phases were discovered by Galileo, in 1610. His observations were
among the first that confirmed the veracity of the system of Copernicus,
affording an evident example of the movement of the planets round the
sun. They are often visible to the unaided eye with good sight, either
at dusk, or through light clouds.
[Illustration: FIG. 38.--Venus at greatest brilliancy.]
Venus, surrounded by a highly dense and rarefied atmosphere, which
increases the difficulties of observing her surface, might be called the
twin sister of the Earth, so similar are the dimensions of the two
worlds. But, strange as it may seem to the many admirers, who are ready
to hail in her an abode of joy and happiness, it is most probable that
this planet, attractive as she is at a distance, would be a less
desirable habitation than our floating island. In fact, the atmosphere
of Venus is perpetually covered with cloud, so that the weather there
must be always foggy. No definite geographical configuration can be
discovered on her, despite the hopes of the eighteenth-century
astronomers. We are not even sure that she rotates upon herself, so
contradictory are the observations, and so hard is it to distinguish
anything clearly upon her surface. A single night of observation
suffices to show the rotation of Mars or of Jupiter; but the beautiful
Evening Star remains obstinately veiled from our curiosity.
Several astronomers, and not the least considerable, think that the
tides produced by the Sun upon her seas, or globe in its state of
pristine fluidity, must have been strong enough to seize and fix her, as
the Earth did for the Moon, thus obliging her to present always the same
face to the Sun. Certain telescopic observations would even seem to
confirm this theoretical deduction from the calculations of celestial
mechanics.
The author ventures to disagree with this opinion, its apparent
probability notwithstanding, because he has invariably received a
contrary impression from all his telescopic observations. He has quite
recently (spring of 1903) repeated these observations. Choosing a
remarkably clear and perfectly calm atmosphere, he examined the splendid
planet several times with great attention in the field of the telescope.
The right or eastern border (reversed image) was dulled by the
atmosphere of Venus; this is the line of separation between day and
night. Beneath, at the extreme northern edge, he was attracted on each
occasion by a small white patch, a little whiter than the rest of the
surface of the planet, surrounded by a light-gray penumbra, giving the
exact effect of a polar snow, very analogous to that observed at the
poles of Mars. To the author this white spot on the boreal horn of
Venus does not appear to be due to an effect of contrast, as has
sometimes been supposed.
Now, if the globe of Venus has poles, it must turn upon itself.
Unfortunately it has proved impossible to distinguish any sign upon the
disk, indicative of the direction and speed of its rotary movement,
although these observations were made, with others, under excellent
conditions.--Three o'clock in the afternoon, brilliant sun, sky clear
blue, the planet but little removed from the meridian--at which time it
is less dazzling than in the evening.
There is merely the impression; but it is so definite as to prevent the
author from adopting the new hypothesis, in virtue of which the planet,
as it gravitates round the Sun, presents always the same hemisphere.
If this hypothesis were a reality, Venus would certainly be a very
peculiar world. Eternal day on the one side; eternal night on the other.
Maximum light and heat at the center of the hemisphere perpetually
turned to the Sun; maximum cold and center of night at the antipodes.
This icy hemisphere would possibly be uninhabitable, but the resources
of Nature are so prodigious, and the law of Life is so imperious, so
persistent, under the most disadvantageous and deplorable terrestrial
conditions, that it would be transcending our rights to declare an
impossibility of existence, even in this eternal night. The currents of
the atmosphere would no doubt suffice to set up perpetual changes of
temperature between the two hemispheres, in comparison with which our
trade-winds would be the lightest of breezes.
Yes, mystery still reigns upon this adjacent earth, and the most
powerful instruments of the observatories of the whole world have been
unable to solve it. All we know is that the diameter, surface, volume
and mass of this planet, and its weight at the surface, do not differ
sensibly from those that characterize our own globe: that this planet is
sister to our own, and of the same order, hence probably formed of the
same elements. We further know that, as seen from Venus (Fig. 39), the
Earth on which we live is a magnificent star, a double orb more
brilliant even than when viewed from Mercury. It is a dazzling orb of
first magnitude, accompanied by its moon, a star of the second and a
half magnitude.
And thus the worlds float on in space, distant symbols of hopes not
realized on any one of them, all at different stages of their degree of
evolution, representing an ever-growing progress in the sequence of the
ages.
[Illustration: FIG. 39.--The Earth viewed from Venus.]
When we contemplate this radiant Venus, it is difficult, even if we can
not form any definite idea as to her actual state as regards habitation,
to assume that she must be a dreary desert, and not, on the contrary,
to hail in her a celestial land, differing more or less from our own
dwelling-place, travailing with her sisters in the accomplishment of the
general plan of Nature.
Such are the characteristic features of our celestial neighbor. In
quitting her, we reach the Earth, which comes immediately next her in
order of distance, 149 million kilometers (93,000,000 miles) from the
Sun, but as we shall devote an entire chapter to our own planet, we will
not halt at this point, but cross in one step the distance that
separates Mars from Venus.
Let us only remark in passing, that our planet is the largest of the
four spheres adjacent to the Sun. Here are their comparative diameters:
The Earth = 1. In Kilometers. In Miles.
Mercury 0.373 4,750 2,946
Venus 0.999 12,730 7,894
Earth 1.000 12,742 7,926
Mars 0.528 6,728 4,172
It will be seen that Venus is almost identical with the Earth.
MARS
Two hundred and twenty-six millions of kilometers (140,000,000 miles)
from the Sun is the planet Mars, gravitating in an orbit exterior to
that which the Earth takes annually round the same center.
Unfortunate Mars! What evil fairy presided at his birth? From
antiquity, all curses seem to have fallen upon him. He is the god of war
and of carnage, the protector of armies, the inspirer of hatred among
the peoples, it is he who pours out the blood of Humanity in
international hecatombs. Here, again, as in the case of Mercury and
Venus, the appearance has originated the idea. Mars, in fact, burns like
a drop of blood in the depths of the firmament, and it is this ruddy
color that inspired its name and attributes, just as the dazzling
whiteness of Venus made her the goddess of love and beauty. Why, indeed,
should the origins of mythology be sought elsewhere than in astronomy?
While Humanity was attributing to the presumptive influence of Mars the
defects inherent in its own terrestrial nature, this world, unwitting of
our sorrows, pursued the celestial path marked out for it in space by
destiny.
This planet is, as we have said, the first encountered after the Earth.
Its orbit is very elongated, very eccentric. Mars accomplishes it in a
period of 1 year, 321 days, 22 hours, _i.e._, 1 year, 10 months, 21
days, or 687 days. The velocity of its transit is 23 kilometers (14.5
miles) per second; that of the Earth is 30 (19 miles). Our planet,
traveling through space at an average distance of 149 million kilometers
(93,000,000 miles) from the central focus, is separated from Mars by an
average distance of 76 million kilometers (47,000,000 miles); but as its
orbit is equally elliptic and elongated it follows that at certain
epochs the two planets approach one another by something less than 60
million kilometers (37,000,000 miles). These are the periods selected
for making the best observations upon our neighbor of the ruddy rays.
The oppositions of Mars arrive about every twenty-six months, but the
periods of its greatest proximity, when this planet approaches to within
56 million kilometers (34,700,000 miles) of the Earth, occur only every
fifteen years.
Mars is then passing perihelion, while our world is at aphelion (or
greatest distance from the Sun). At such epochs this globe presents to
us an apparent diameter 63 times smaller than that of the Moon, _i.e._,
a telescope that magnifies 63 times would show him to us of the same
magnitude as our satellite viewed with the unaided eye, and an
instrument that magnified 630 times would show him ten times larger in
diameter.
In dimensions he differs considerably from our world, being almost half
the size of the Earth. In diameter he measures only 6,728 kilometers
(4,172 miles), and his circumference is 21,125 kilometers (13,000
miles). His surface is only 29/100 of the terrestrial surface, and his
volume only 15/100 of our own.
This difference in volume causes Mars to be an earth in miniature. When
we study his aspects, his geography, his meteorology, we seem to see in
space a reduction of our own abode, with certain dissimilarities that
excite our curiosity, and make him even more interesting to us.
The Martian world weighs nine times and a half less than our own. If we
represent the weight of the Earth by 1,000, that of Mars would be
represented by 105. His density is much less than our own; it is only
7/10 that of the Earth. A man weighing 70 kilograms, transported to the
adjacent globe, would weigh only 26 kilograms.
The earliest telescopic observations revealed the existence of more or
less accentuated markings upon the surface of Mars. The progress of
optics, admitting of greater magnifications, exhibited the form of these
patches more clearly, while the study of their motions enabled the
astronomers to determine with remarkable precision the diurnal rotation
of this planet. It occurs in 24 hours, 37 minutes, 23.65 seconds. Day
and night are accordingly a little longer on Mars than on the Earth, but
the difference is obviously inconsiderable. The year of Mars consists of
668 Martian days. The inclination of the axis of rotation of this globe
upon the plane of its orbit is much the same as our own. In
consequence, its seasons are analogous to ours in intensity, while twice
the length, the Martian year being almost equal to two of our years. The
intensity of the seasons is indeed more accentuated than upon the Earth,
since the orbit of Mars is very elongated. But there, as here, are three
quite distinct zones: the torrid, the temperate, and the glacial.
By means of the telescope we can follow the variations of the Martian
seasons, especially in what concerns the polar snows, which regularly
aggregate during the winter, and melt no less regularly during the heat
of the summer. These snows are very easily observed, and stand out
clearly with dazzling whiteness. The reader can judge of them by the
accompanying figure, which sums up the author's observations during one
of the recent oppositions of Mars (1900-1901). The size of the polar cap
diminished from 4,680 kilometers to 840. The solstice of the Martian
summer was on April 11th. The snows were still melting on July 6th.
Sometimes they disappear almost entirely during the Martian month that
corresponds to our month of August, as never happens with our polar ice.
Hence, though this planet is farther away from the Sun than ourselves,
it does not appear to be colder, or, at any rate, it is certain that the
polar snows are much less thick.
On the other hand, there are hardly ever clouds on Mars; the Martian
atmosphere is almost always limpid, and one can say that fine weather is
the chronic state of the planet. At times, light fogs or a little vapor
will appear in certain regions, but they are soon dissipated, and the
sky clears up again.
[Illustration: FIG. 40.--Diminution of the polar snows of Mars during
the summer.]
Since the invention of the telescope, a considerable number of drawings
have been made, depicting Mars under every aspect, and the agreement
between these numerous observations gives us a sufficient acquaintance
with the planet to admit of our indicating the characteristic features
of its geography, and of drawing out _areographic_ maps (_Ares_, Mars).
Its appearance can be judged of from the two drawings here reproduced,
as made (February, 1901) at the Observatory of Juvisy, and from the
general chart drawn from the total sum of observations (Figs. 41, 42 and
43).
It will be seen at the first glance that the geography of Mars is very
different from that of our own globe: while three-quarters of the Earth
are covered with the liquid element, Mars seems to be more evenly
divided, and must indeed have rather more land than water. We find no
immense oceans surrounding the continents, and separating them like
islands; on the contrary, the seas are reduced to long gulfs compressed
between the shores, like the Mediterranean for example, nor is it even
certain that these gray spots do all represent true seas. It has been
agreed to term _sea_ the parts that are lightly tinged with green, and
to give the name of _continent_ to the spots colored yellow. That is the
hue of the Martian soil, due either to the soil itself, which would
resemble that of the Sahara, or, to take a less arid region, that seen
on the line between Marseilles and Nice, in the vicinity of the
Esterels; or perhaps to some peculiar vegetation. During ascents in a
balloon, the author has often remarked that the hue of the ripe corn,
with the Sun shining on it, is precisely that presented to us by the
continents of Mars in the best hours for observation.
[Illustration: FIG. 41.--Telescopic aspect of the planet Mars (Feb.,
1901).]
As to the "seas," it is pretty certain that there must be water, or
some kind of liquid, deriving above all from the melting of the polar
snows in spring and summer; but it may possibly be in conjunction with
some vegetation, aquatic plants, or perhaps vast meadows, which appear
to us from here to be the more considerable in proportion as the water
that nourishes them has been more abundant.
[Illustration: FIG. 42.--Telescopic aspect of the planet Mars (Feb.,
1901).]
Mars, like our globe, is surrounded with a protective atmosphere, which
retains the rays of the Sun, and must preserve a medium temperature
favorable to the conservation of life upon the surface of the planet.
But the circulation of the water, so important to terrestrial life,
whether animal or vegetable, which is effected upon our planet by the
evaporation of the seas, clouds, winds, rains, wells, rivers and
streams, comes about quite differently on Mars; for, as was remarked
above, it is rarely that any clouds are observed there. Instead of being
vertical, as here, this circulation is horizontal: the water coming from
the source of the polar snows finds its way into the canals and seas,
and returns to be condensed at the poles by a light drift of invisible
vapors directed from the equator to the poles. There is never any rain.
We have spoken of _canals_. One of the great puzzles of the Martian
world is incontestably the appearance of straight lines that furrow its
surface in all directions, and seem to connect the seas. M.
Schiaparelli, the distinguished Director of the Observatory of Milan,
who discovered them in 1877, called them canals, without, however,
postulating anything as to their real nature. Are they indeed canals?
These straight lines, measuring sometimes 600 kilometers (372 miles) in
length, and more than 100 kilometers (62 miles) in breadth, have much
the same hue as the seas on which they open. For a quarter of a century
they have been surveyed by the greater number of our observers. But it
must be confessed that, even with the best instruments, we only approach
Mars at a distance of 60,000 kilometers (37,200 miles), which is still a
little far off, and we may be sure that we do not distinguish the true
details of the surface.[11] These details at the limits of visibility
produce the appearance of canals to our eyes. They may possibly be lines
of lakes, or oases. The future will no doubt clear up this mystery for
us.
[Illustration: FIG. 43.--Chart of Mars.]
As to the inhabitants of Mars, this world is in a situation as
favorable as our Earth for habitation, and it would be difficult to
discover any reason for perpetual sterility there. It appears to us, on
the contrary, by its rapid and frequent variations of aspect, to be a
very living world. Its atmosphere, which is always clear, has not the
density of our own, and resembles that of the highest mountains. The
conditions of existence there vary from ours, and appear to be more
delicate, more ethereal.
There as here, day succeeds to night, spring softens the rigors of
winter; the seasons unfold, less disparate than our own, of which we
have such frequent reason to complain. The sky is perpetually clear.
There are never tempests, hurricanes, nor cyclones, the wind never gets
up any force there, on account of the rarity of the atmosphere, and the
low intensity of weight.
Differing from ours, this world may well be a more congenial
habitation. It is more ancient than the Earth, smaller, less massive. It
has run more quickly through the phases of its evolution. Its astral
life is more advanced, and its Humanity should be superior to our own,
just as our successors a million years hence, for example, will be less
coarse and barbarous than we are at present: the law of progress governs
all the worlds, and, moreover, the physical constitution of the planet
Mars is less dense than our own.
There is no need to despair of entering some day into communication with
these unknown beings. The luminous points that have been observed are no
signals, but high summits or light clouds illuminated by the rising or
setting sun. But the idea of communication with them in the future is no
more audacious and no less scientific than the invention of spectral
analysis, X-rays, or wireless telegraphy.
We may suppose that the study of astronomy is further advanced in Mars
than on the Earth, because humanity itself has advanced further, and
because the starry sky is far finer there, far easier to study, owing to
the limpidity of its pure, clear atmosphere.
Two small moons (hardly larger than the city of Paris) revolve rapidly
round Mars; they are called Phobos and Deimos. The former, at a distance
of 6,000 kilometers (3,730 miles) from the surface, accomplishes its
revolution rapidly, in seven hours, thirty-nine minutes, and thus makes
the entire circle of the Heavens three times a day. The second
gravitates at 20,000 kilometers (12,400 miles), and turns round its
center of attraction in thirty hours and eighteen minutes. These two
satellites were discovered by Mr. Hall, at the University of Washington,
in the month of August, 1877.
* * * * *
Among the finest and most interesting of the celestial phenomena admired
by the Martians, at certain epochs of the year,--now at night when the
Sun has plunged into his fiery bed, now in the morning, a little before
the aurora,--is a magnificent star of first magnitude, never far removed
from the orb of day, which presents to them the same aspects as does
Venus to ourselves. This splendid orb, which has doubtless received the
most flattering names from those who contemplate it, this radiant star
of a beautiful greenish blue, courses in space accompanied by a little
satellite, sparkling like some splendid diamond, after sunset, in the
clear sky of Mars. This superb orb is the Earth, and the little star
accompanying it is the Moon.
[Illustration: FIG. 44.--The Earth viewed from Mars.]
Yes, to the Martians our Earth is a star of the morning and evening;
doubtless they have determined her phases. Many a vow, and many a hope
must have been wafted toward her, more than one broken heart must have
permitted its unrealized dreams to wander forth to our planet as to an
abode of happiness where all who have suffered in their native world
might find a haven. But our planet, alas! is not as perfect as they
imagine.
We must not dally upon Mars, but hasten our celestial excursion toward
Jupiter.
CHAPTER VI
THE PLANETS
_B._--JUPITER, SATURN, URANUS, NEPTUNE.
Before we attack the giant world of our system, we must halt for a few
moments upon the minor planets which circulate between the orbit of Mars
and that of Jupiter. These minute asters, little worlds, the largest of
which measures scarcely more than 100 kilometers (62 miles) in diameter,
are fragments of cosmic matter that once belonged to a vast ring, formed
at the time when the solar system was only an immense nebula; and which,
instead of condensing into a single globe coursing between Mars and
Jupiter, split up into a considerable quantity of particles constituting
at the present time the curious and highly interesting Republic of the
Asteroids.
These lilliputian worlds at first received the names of the more
celebrated of the minor mythological divinities--Ceres, Pallas, Juno,
Vesta, etc., but as they rapidly increased in number, it was found
necessary to call them by modern, terrestrial names, and more than one
daughter of Eve, the Egeria of some astronomer, now has her name
inscribed in the Heavens. The first minor planet was discovered on the
first day of the nineteenth century, January 1, 1801, by Piazzi,
astronomer at Palermo. While he was observing the small stars in the
constellation of the Bull beneath the clear Sicilian skies, this famous
astronomer noticed one that he had never seen before.
The next night, directing his telescope to the same part of the Heavens,
he perceived that the fair unknown had moved her station, and the
observations of the following days left him no doubt as to the nature of
the visitor: she was a planet, a wandering star among the
constellations, revolving round the Sun. This newcomer was registered
under the name of Ceres.
Since that epoch several hundreds of them have been discovered,
occupying a zone that extends over a space of more than 400 million
kilometers (249,000,000 miles). These celestial globules are invisible
to the naked eye, but no year passes without new and numerous recruits
being added to the already important catalogue of these minute asters by
the patient observers of the Heavens. To-day, they are most frequently
discovered by the photographic method of following the displacement of
the tiny moving points upon an exposed sensitive plate.
JUPITER
And now let us bow respectfully before Jupiter, the giant of the worlds.
This glorious planet is indeed King of the Solar System.
While Mercury measures only 4,750 kilometers (2,946 miles) in diameter,
and Mars 6,728 kilometers (4,172), Jupiter is no less than 140,920
kilometers (87,400 miles) in breadth; that is to say, eleven times
larger than the Earth. He is 442,500 kilometers (274,357 miles) in
circumference.
In volume he is equivalent to 1,279 terrestrial globes; hence he is only
a million times smaller than the Sun. The previously described planets
of our system, Mercury, Venus, the Earth, and Mars combined, would form
only an insignificant mass in comparison with this colossus. A hundred
and twenty-six Earths joined into one group would present a surface
whose extent would still not be quite as vast as the superficies of this
titanic world. This immense globe weighs 310 times more than that which
we inhabit. Its density is only the quarter of our own; but weight is
twice and a half times as great there as here. The constituents of
things and beings are thus composed of materials lighter than those upon
the Earth; but, as the planet exerts a force of attraction twice and a
half times as powerful, they are in reality heavier and weigh more. A
graceful maiden weighing fifty kilograms would if transported to Jupiter
immediately be included in the imposing society of the "Hundred Kilos."
Jupiter rotates upon himself with prodigious rapidity. He accomplishes
his diurnal revolution in less than ten hours! There the day lasts half
as long as here, and while we reckoned fifteen days upon our calendar,
the Jovian would count thirty-six. As Jupiter's year equals nearly
twelve of ours, the almanac of that planet would contain 10,455 days!
Obviously, our pretty little pocket calendars would never serve to
enumerate all the dates in this vast world.
This splendid globe courses in space at a distance of 775,000,000
kilometers (480,500,000 miles) from the Sun. Hence it is five times
(5.2) as remote from the orb of day as our Earth, and its orbit is five
times vaster than our own. At that distance the Sun subtends a diameter
five times smaller than that which we see, and its surface is
twenty-seven times less extensive; accordingly this planetary abode
receives on an average twenty-seven times less light and heat than we
obtain.
In the telescope Jupiter presents an aspect analogous to that likely to
be exhibited by a world covered with clouds, and enveloped in dense
vapors (Fig. 45).
It is, in fact, the seat of formidable perturbations, of strange
revolutions by which it is perpetually convulsed, for although of more
ancient formation than the Earth, this celestial giant has not yet
arrived at the stable condition of our dwelling-place. Owing to its
considerable volume, this globe has probably preserved its original
heat, revolving in space as an obscure Sun, but perhaps still burning.
In it we see what our own planet must have been in its primordial epoch,
in the pristine times of terrestrial genesis.
[Illustration: FIG. 45.--Telescopic aspect of Jupiter.]
Since its orbital revolution occupies nearly twelve years, Jupiter
comes back into opposition with the Sun every 399 days, _i.e._, 1 year,
34 days, that is with one month and four days' delay each year. At these
periods it is located at the extremity of a straight line which, passing
by the Earth, is prolonged to the Sun. These are the epochs to be
selected for observation. It shines then, all night, like some dazzling
star of the first magnitude, of excessive whiteness: nor can it be
confounded either with Venus, more luminous still (for she is never
visible at midnight, in the full South, but is South-west in the
evening, or South-east in the morning), nor with Mars, whose fires are
ruddy.
In the telescope, the immense planet presents a superb disk that an
enlargement of forty times shows us to be the same size to all
appearance as that of the Moon seen with the unaided eye. Its shape is
not absolutely spherical, but spheroid--that is, flattened at the poles.
The flattening is 1/17.
We know that the Earth's axis dips a certain quantity on the plane of
her orbit, and that it is this inclination that produces the seasons.
Now it is not the same for Jupiter. His axis of rotation remains almost
vertical throughout the course of his year, and results in the complete
absence of climates and seasons. There is neither glacial zone, nor
tropic zone; the position of Jupiter is eternally that of the Earth at
the season of the equinox, and the vast world enjoys, as it were,
perpetual spring. It knows neither the hoar-frost nor the snows of
winter. The heat received from the Sun diminishes gradually from the
equator to the poles without abrupt transitions, and the duration of day
and night is equal there throughout the entire year, under every
latitude. A privileged world, indeed!
It is surrounded by a very dense, thick atmosphere, which undergoes more
extensive variations than could be produced by the Sun at such a
distance. Spectral analysis detects a large amount of water-vapor,
showing that this planet still possesses a very considerable quantity of
intrinsic heat.
Most conspicuous upon this globe are the larger or smaller bands or
markings (gray and white, sometimes tinted yellow, or of a maroon or
chocolate hue) by which its surface is streaked, particularly in the
vicinity of the equator. These different belts vary, and are constantly
modified, either in form or color. Sometimes, they are irregular, and
cut up; at others they are interspersed with more or less brilliant
patches. These patches are not affixed to the surface of the globe, like
the seas and continents of the Earth; nor do they circulate round the
planet like the satellites, in more or less elongated and regular
revolutions, but are relatively mobile, like our clouds in the
atmosphere, while observation of their motion does not give the exact
period of the rotation of Jupiter. Some only appear upon the agitated
disk to vanish very quickly; others subsist for a considerable period.
One has been observed for over a quarter of a century, and appears to be
almost immobile upon this colossal globe. This spot, which was red at
its first appearance, is now pale and ghostly. It is oval (_vide_ Fig.
45) and measures 42,000 kilometers (26,040 miles) in length by 15,000
kilometers (9,300 miles) in width. Hence it is about four times as long
as the diameter of our Earth; that is, relatively to the size of
Jupiter, as are the dimensions of Australia in proportion to our globe.
The discussion of a larger number of observations leads us to see in it
a sort of continent in the making, a scoria recently ejected from the
mobile and still liquid and heated surface of the giant Jupiter. The
patch, however, oscillates perceptibly, and appears to be a floating
island.
We must add that this vast world, like the Sun, _does not rotate all in
one period_. Eight different currents can be perceived upon its surface.
The most rapid is that of the equatorial zone, which accomplishes its
revolution in 9 hours, 50 minutes, 29 seconds. A point situated on the
equator is therefore carried forward at a speed of 12,500 meters (7
miles) per second, and it is this giddy velocity of Jupiter that has
produced the flattening of the poles. From the equator to the poles, the
swiftness of the currents diminishes irregularly, and the difference
amounts to about five minutes between the movement of the equatorial
stream, and that of the northern and southern currents. But what is more
curious still is that the velocity of one and the same stream is subject
to certain fluctuations; thus, in the last quarter of a century, the
speed of the equatorial current has progressively diminished. In 1879,
the velocity was 9 hours, 49 minutes, 59 seconds, and now it is, as we
have already seen, 9 hours, 50 minutes, 29 seconds, which represents a
substantial reduction. The rotation of the red patch, at 25 degrees of
the southern latitude, is effected in 9 hours, 55 minutes, 40 seconds.
We are confronted with a strange and mysterious world. It is the world
of the future.
This giant gravitates in space accompanied by a suite of five
satellites. These are:
Names. Distance from surface of Jupiter. Time of revolution.
Kilometers. Miles. Days. Hours.
5. 200,000 124,000 11
1. Io 430,000 266,000 1 18
2. Europa 682,000 422,840 3 13
3. Ganymede 1,088,000 674,560 7 4
4. Callisto 1,914,000 1,186,680 16 16
The four principal satellites of Jupiter were discovered at the same
time, on the same evenings (January 7 and 8, 1610), by the two
astronomers who were pointing their telescopes at Jupiter: Galileo in
Italy, and Simon Marius in Germany.
On September 9, 1892, Mr. Barnard, astronomer of the Lick Observatory,
California, discovered a new satellite, extremely minute, and very near
the enormous planet. It has so far received no name, and is known as the
fifth, although the four principal are numbered in the order of their
distances.
[Illustration: FIG. 46.--Jupiter and his four principal satellites.]
The four classical satellites are visible in the smallest instruments
(Fig. 46): the third is the most voluminous.
Such is the splendid system of the mighty Jupiter. Once, doubtless, this
fine planet illuminated the troop of worlds that derived their treasure
of vitality from him with his intrinsic light: to-day, however, these
moons in their turn shed upon the extinct central globe the pale soft
light which they receive from our solar focus, illuminating the brief
Jovian nights (which last less than five hours, on account of the
twilight) with their variable brilliancy.
At the distance of the first satellite, Jupiter exhibits a disk
_fourteen hundred times_ vaster than that of the Full Moon! What a
dazzling spectacle, what a fairy scene must the enormous star afford to
the inhabitants of that tiny world! And what a shabby figure must our
Earth and Moon present in the face of such a body, a real miniature of
the great solar system!
Our ancestors were well inspired when they attributed the sovereignty of
Olympus to this majestic planet. His brilliancy corresponds with his
real grandeur. His dominion in the midnight Heavens is unique. Here
again, as for Venus, Mars, and Mercury, astronomy has created the legend
of the fables of mythology.
Let us repeat in conclusion that our Earth becomes practically invisible
for the inhabitants of the other worlds beyond the distance of Jupiter.
SATURN
Turn back now for a moment to the plan of the Solar System.
We had to cross 775 million kilometers (480,000,000 miles) when we left
the Sun, in order to reach the immense orb of Jupiter, which courses in
space at 626 million kilometers (388,000,000 miles) from the terrestrial
orbit. From Jupiter we had to traverse a distance of 646 million
kilometers (400,000,000 miles) in order to reach the marvelous system of
Saturn, where our eyes and thoughts must next alight.
Son of Uranus and Vesta, Saturn was the God of Time and Fate. He is
generally represented as an aged man bearing a scythe. His mythological
character is only the expression of his celestial aspect, as we have
seen for the brilliant Jupiter, for the pale Venus, the ruddy Mars, and
the agile Mercury. The revolution of Saturn is the slowest of any among
the planets known to the ancients. It takes almost thirty years for its
accomplishment, and at that distance the Saturnian world, though it
still shines with the brilliancy of a star of the first magnitude,
exhibits to our eyes a pale and leaden hue. Here is, indeed, the god of
Time, with slow and almost funereal gait.
Poor Saturn won no favor with the poets and astrologers. He bore the
horrid reputation of being the inexhaustible source of misfortune and
evil fates,--whereof he is wholly innocent, troubling himself not at all
with our world nor its inhabitants.
This world travels in the vastness of the Heavens at a distance of 1,421
million kilometers (881,000,000 miles) from the Sun. Hence it is ten
times farther from the orb of day than the Earth, though still
illuminated and governed by the Sun-God. Its gigantic orbit is ten times
larger than our own.
Its revolution round the Sun is accomplished in 10,759 days, _i.e._, 29
years, 167 days, and as this strange planet rotates upon itself with
great rapidity in 10 hours, 15 minutes, its year comprises no less than
25,217 days. What a calendar! The Saturnians must needs have a
prodigious memory not to get hopelessly involved in this interminable
number of days. A curious world, where each year stands for almost
thirty of our own, and where the day is more than half as short again as
ours. But we shall presently find other and more extraordinary
differences on this planet.
In the first place it is nearly nine and a half times larger than our
world. It is a globe, not spherical, but spheroidal, and the flattening
of its poles, which is one-tenth, exceeds that of all the other planets,
even Jupiter. It follows that its equatorial diameter is 112,500
kilometers (69,750 miles), while its polar diameter measures only
110,000 kilometers (68,200).
In volume, Saturn is 719 times larger than the Earth, but its density is
only 128/1000 of our own; _i.e._, the materials of which it is composed
are much less heavy, so that it weighs only 92 times more than our
Earth. Its surface is 85 times vaster than that of the Earth, no
insignificant proportion.
[Illustration: FIG. 47.--Saturn.]
The dipping of Saturn's axis of rotation is much the same as our own.
Hence we conclude that the seasons of this planet are analogous to ours
in relative intensity. Only upon this far-off world each season lasts
for seven years. At the distance at which it gravitates in space, the
heat and light which it receives from the Sun are 90 times less active
than such as reach our selves; but it apparently possesses an atmosphere
of great density, which may be constituted so that the heat is
preserved, and the planet maintained in a calorific condition but little
inferior to our own.
In the telescope, the disk of Saturn exhibits large belts that recall
those of Jupiter, though they are broader and less accentuated (Fig.
47). There are doubtless zones of clouds or rapid currents circulating
in the atmosphere. Spots are also visible whose displacement assists in
calculating the diurnal motions of this globe.
The most extraordinary characteristic of this strange world is, however,
the existence of a vast _ring_, which is almost flat and very large, and
entirely envelops the body of the planet. It is suspended in the
Saturnian sky, like a gigantic triumphal arch, at a height of some
20,000 kilometers (12,400 miles) above the equator. This splendid arch
is circular, like an immense crown illuminated by the Sun. From here we
only see it obliquely, and it appears to us elliptical; a part of the
ring seems to pass in front of Saturn, and its shadow is visible on the
planet, while the opposite part passes behind.
This ring, which measures 284,000 kilometers (176,080 miles) in
diameter, and less than 100 kilometers (62 miles) in breadth, is divided
into three distinct zones: the exterior is less luminous than the
center, which is always brighter than the planet itself; the interior is
very dark, and spreads out like a dusky and faintly transparent veil,
through which Saturn can be distinguished.
What is the nature of these vast concentric circles that surround the
planet with a luminous halo? They are composed of an innumerable number
of particles, of a quantity of cosmic fragments, which are swept off in
a rapid revolution, and gravitate round the planet at variable speed and
distance. The nearer particles must accomplish their revolution in 5
hours, 50 minutes, and the most distant in about 12 hours, 5 minutes, to
prevent them from being merged in the surface of Saturn: their own
centrifugal force sustains them in space.
[Illustration: FIG. 48. Varying perspective of Saturn's Rings, as seen
from the Earth.]
With a good glass the effect of these rings is most striking, and one
can not refrain from emotion on contemplating this marvel, whereby one
of the brothers of our terrestrial country is crowned with a golden
diadem. Its aspects vary with its perspective relative to the Earth, as
may be seen from the subjoined figure (Fig. 48).
We must not quit the Saturnian province without mentioning the eight
satellites that form his splendid suite:
Names. Distance from the planet. Time of revolution.
Kilometers. Miles. Days. Hours. Minutes.
1. Mimas 207,000 128,340 22 37
2. Enceladus 257,600 159,712 1 8 53
3. Tethys 328,800 203,856 1 21 18
4. Dione 421,200 261,144 2 17 41
5. Rhea 588,400 364,808 4 12 25
6. Titan 1,364,000 845,680 15 22 41
7. Hyperion 1,650,000 1,023,000 21 6 39
8. Japhet 3,964,000 2,457,680 79 7 54
Here is a marvelous system, with, what is more, eight different kinds of
months for the inhabitants of Saturn; eight moons with constantly
varying phases juggling above the rings!
Now we shall cross at a bound the 1,400 million kilometers (868,000,000
miles) that separate us from the last station but one of the immense
solar system.
URANUS
On March 13, 1781, William Herschel, a Hanoverian astronomer who had
emigrated to England, having abandoned the study of music to devote
himself to the sublime science of the Heavens, was observing the vast
fields with their constellations of golden stars, when he perceived a
luminous point that appeared to him to exceed that of the other
celestial luminaries in diameter. He replaced the magnification of his
telescope by more powerful eye-pieces, and found that the apparent
diameter of the orb increased proportionately with the amplification of
the power, which does not happen in the case of stars at infinite
distance. His observations on the following evenings enabled him to note
the slow and imperceptible movement of this star upon the celestial
sphere, and left him in no further doubt: there was no star, but some
much nearer orb, in all probability a comet, for the great astronomer
dared not predict the discovery of a new planet. And it was thus, under
the name of cometary orb, that the seventh child of the Sun was
announced. The astronomers sought to determine the motions of the new
arrival, to discover for it an elliptical orbit such as most comets
have. But their efforts were vain, and after several months' study the
conclusion was reached that here was a new planet, throwing back the
limits of the solar system to a point far beyond that of the Saturnian
frontier, as admitted from antiquity.
This new world received the name of Uranus, father of Saturn, his
nearest neighbor in the solar empire. Uranus shines in the firmament as
a small star of sixth magnitude, invisible to the unaided eye for
normal sight, at a distance of 2,831,000,000 kilometers (1,755,000,000
miles) from the Sun. Smaller than Jupiter and Saturn, this planet is yet
larger than Mercury, Venus, Mars, and the Earth together, thus
presenting proportions that claim our respect and admiration.
His diameter may be taken at about 55,000 kilometers (34,200 miles),
that is, rather more than four times the breadth of the terrestrial
diameter. Sixty-nine times more voluminous than the Earth, and seventeen
times more extensive in surface, this new world is much less than our
own in density. The matter of which it is composed is nearly five times
lighter than that of our globe.
Spectral analysis shows that this distant planet is surrounded with an
atmosphere very different from that which we breathe, enclosing gases
that do not exist in ours.
The Uranian globe courses over the fields of infinity in a vast orbit
seventeen times larger than our own, and its revolution lasts 36,688
days, _i.e._, 84 years, 8 days. It travels slowly and sadly under the
pale and languishing rays of the Sun, which sends it nearly three
hundred times less of light and heat than we receive. At this distance
the solar disk would present a diameter seventeen times smaller than
that which we admire, and a surface three hundred times less vast. A
dull world indeed! And what an interminable year! The idle people who
are in the habit of being bored must find time even longer upon Uranus
than upon our little Earth, where the days pass so rapidly. And if
matters are arranged there as here, a babe of a year old, beginning to
babble in its nurse's arms, would already have lived as long as an old
man of eighty-four in this world.
But what most seriously complicates the Calendar of the Uranians is the
fact that the four moons which accompany the planet accomplish their
revolution in four different kinds of months, in two, four, eight, and
thirteen days, as is shown in the following table:
Distance from the planet. Time of revolution.
Kilometers. Miles. Days. Hours. Minutes.
1. Ariel 196,000 121,520 2 12 29
2. Umbriel 276,000 171,120 4 3 27
3. Titania 450,000 279,000 8 16 56
4. Oberon 600,000 372,000 13 11 7
The most curious fact is that these satellites do not rotate like those
of the other planets. While the moons of the Earth, Mars, Jupiter, and
Saturn accomplish their revolution from east to west, the satellites of
Uranus rotate in a plane almost perpendicular to the ecliptic, and it is
doubtless the same for the rotation of the planet.
If we had to quit the Earth, and fixate ourselves upon another world,
we should prefer Mars to Uranus, where everything must be so different
from terrestrial arrangements? But who knows? Perhaps, after all, this
planet might afford us some agreeable surprises. _Il ne faut jurer de
rien._
NEPTUNE
And here we reach the frontier of the Solar System, as actually known to
us. In landing on the world of Neptune, which circles through the
Heavens in eternal twilight at a distance of more than four milliard
kilometers (2,480,000,000 miles) from the common center of attraction of
the planetary orbs, we once again admire the prodigies of science.
Uranus was discovered with the telescope, Neptune by calculation. In
addition to the solar influence, the worlds exert a mutual attraction
upon each other that slightly deranges the harmony ordered by the Sun.
The stronger act upon the weaker, and the colossal Jupiter alone causes
many of the perturbations in our great solar family. Now during regular
observations of the position of Uranus in space, some inexplicable
irregularities were soon perceived. The astronomers having full faith in
the universality of the law of attraction, could not do otherwise than
attribute these irregularities to the influence of some unknown planet
situated even farther off. But at what distance?
A very simple proportion, known as Bode's law, has been observed, which
indicates approximately the relative distances of the planets from the
Sun. It is as follows: Starting from 0, write the number 3, and double
successively,
0 3 6 12 24 48 96 192 384.
Then, add the number 4 to each of the preceding figures, which gives the
following series:
4 7 10 16 28 52 100 196 388.
Now it is a very curious fact that if the distance between the Earth and
the Sun be represented by 10, the figure 4 represents the orbit of
Mercury, 7 that of Venus, 16 of Mars; the figure 28 stands for the
medium distance of the minor planets; the distances of Jupiter, Saturn,
and Uranus agree with 52, 100, and 196.
The immortal French mathematician Le Verrier, who pursued the solution
of the Uranian problem, supposed naturally that the disturbing planet
must be at the distance of 388, and made his calculations accordingly.
Its direction in the Heavens was indicated by the form of the
disturbances; the orbit of Uranus bulging, as it were, on the side of
the disturbing factor.
On August 31, 1846, Le Verrier announced the position of the
ultra-Uranian planet, and on September 23d following, a German
astronomer, Galle, at the Observatory of Berlin, who had just received
this intelligence, pointed his telescope toward the quarter of the
Heavens designated, and, in fact, attested the presence of the new orb.
Without quitting his study table, Le Verrier, by the sole use of
mathematics, had detected, and, as it were, touched at pen's point the
mysterious stranger.
Only, it is proved by observation and calculation that it is less remote
than was expected from the preceding law, for it gravitates at a
distance of 300, given that from the Earth to the Sun as 10.
This planet was called Neptune, god of the seas, son of Saturn, brother
of Jupiter. The name is well chosen, since the King of the Ocean lives
in darkness in the depths of the sea, and Le Verrier's orb is also
plunged in the semi-obscurity of the depths of the celestial element.
But it was primarily selected to do justice to an English astronomer,
Adams, who had simultaneously made the same calculations as Le Verrier,
and obtained the same results--without publishing them. His work
remained in the records of the Greenwich Observatory.
The English command the seas, and wherever they dip their finger into
the water and find it salt, they feel themselves "at home," and know
that "Neptune's trident is the scepter of the world," hence this
complimentary nomenclature.
Neptune is separated by a distance of four milliards, four hundred
million kilometers from the solar center.
At such a distance, thirty times greater than that which exists between
the Sun and our world, Neptune receives nine hundred times less light
and heat than ourselves; _i.e._, Spitzbergen and the polar regions of
our globe are furnaces compared with what must be the Neptunian
temperature. Absolutely invisible to the unaided eye, this world
presents in the telescope the aspect of a star of the eighth magnitude.
With powerful magnifications it is possible to measure its disk, which
appears to be slightly tinged with blue. Its diameter is four times
larger than our own, and measures about 48,000 kilometers (29,900
miles), its surface is sixteen times vaster than that of the Earth, and
to attain its volume we should have to put together fifty-five globes
similar to our own. Weight at its surface must be about the same as
here, but its medium density is only 1/3 that of the Earth.
It gravitates slowly, dragging itself along an orbit thirty times vaster
than that of our globe, and its revolution takes 164 years, 281 days,
_i.e._, 164 years, 9 months. A single year of Neptune thus covers
several generations of terrestrial life. Existence must, indeed, be
strange in that tortoise-footed world!
While in their rotation period, Mercury accomplishes 47 kilometers
(29-3/8 miles) per second, and the Earth 29-1/2 (18-1/8 miles), Neptune
rolls along his immense orbit at a rate of only 5-1/2 kilometers (about
3-1/4 miles) per second.
The vast distance that separates us prevents our distinguishing any
details of his surface, but spectral analysis reveals the presence of an
absorbent atmosphere in which are gases unknown to the air of our
planet, and of which the chemical composition resembles that of the
atmosphere of Uranus.
One satellite has been discovered for Neptune. It has a considerable
inclination, and rotates from east to west.
* * * * *
And here we have reached the goal of our interplanetary journey. After
visiting the vast provinces of the solar republic, we feel yet greater
admiration and gratitude toward the luminary that governs, warms, and
illuminates the worlds of his system.
In conclusion, let us again insist that the Earth,--a splendid orb as
viewed from Mercury, Venus, and Mars,--begins to disappear from Jupiter,
where she becomes no more than a tiny spark oscillating from side to
side of the Sun, and occasionally passing in front of him as a small
black dot. From Saturn the visibility of our planet is even more
reduced. As to Uranus and Neptune, we are invisible there, at least to
eyes constructed like our own. We do not possess in the Universe the
importance with which we would endow ourselves.
Neptune up to the present guards the portals of our celestial system; we
will leave him to watch over the distant frontier; but before returning
to the Earth, we must glance at certain eccentric orbs, at the mad,
capricious comets, which imprint their airy flight upon the realms of
space.
CHAPTER VII
THE COMETS
SHOOTING STARS, BOLIDES, URANOLITHS OR METEORIC STONES
What marvels have been reviewed by our dazzled eyes since the outset of
these discussions! We first surveyed the magnificent host of stars that
people the vast firmament of Heaven; next we admired and wondered at
suns very differently constituted from our own; then returning from the
depths of space, crossing at a bound the abyss that separates us from
these mysterious luminaries, the distant torches of our somber night,
terrible suns of infinity, we landed on our own beloved orb, the superb
and brilliant day-star. Thence we visited his celestial family, his
system, in which our Earth is a floating island. But the journey would
be incomplete if we omitted certain more or less vagabond orbs, that
occasionally approach the Sun and Earth, some of which may even collide
with us upon their celestial path. These are in the first place the
comets, then the shooting stars, the fire-balls, and meteorites.
Glittering, swift-footed heralds of Immensity, these comets with golden
wings glide lightly through Space, shedding a momentary illumination by
their presence. Whence come they? Whither are they bound?
What problems they propound to us, when, as in some beautiful display of
pyrotechnics, the arch of Heaven is illuminated with their fantastic
light!
But first of all--what is a Comet?
If instead of living in these days of the telescope, of spectrum
analysis, and of astral photography, we were anterior to Galileo, and to
the liberation of the human spirit by Astronomy, we should reply that
the comet is an object of terror, a dangerous menace that appears to
mortals in the purity of the immaculate Heavens, to announce the most
fatal misfortunes to the inhabitants of our planet. Is a comet visible
in the Heavens? The reigning prince may make his testament and prepare
to die. Another apparition in the firmament bodes war, famine, the
advent of grievous pestilence. The astrologers had an open field, and
their fertile imagination might hazard every possible conjecture, seeing
that misfortunes, great or small, are not altogether rare in this
sublunar world.
How many intellects, and those not the most vulgar, from antiquity to
the middle of the last century cursed the apparition of these hirsute
stars, which brought desolation to the heart of man, and poured their
fatal effluvia upon the head of poor Humanity. The history of the
superstitions and fears that they inspired of old would furnish matter
for the most thrilling of romances. But, on the other hand, the volume
would be little flattering to the common-sense of our ancestors. Despite
the respect we owe our forefathers, let us recall for a moment the
prejudices attaching to the most famous comets whose passage, as
observed from the Earth, has been preserved to us in history.
[Illustration: FIG. 49.--Great Comet of 1858.]
* * * * *
Without going back to the Deluge, we note that the Romans established a
relation between the Great Comet of 43 B.C. and the death of Cæsar, who
had been assassinated a few months previously. It was, they asserted,
the soul of their great Captain, transported to Heaven to reign in the
empyrean after ruling here below. Were not the Emperors Lords of both
Earth and Heaven?
We must in justice recognize that certain more independent spirits
emancipated themselves from these superstitions, and we may cite the
reply of Vespasian to his friends, who were alarmed at the evil presage
of a flaming comet: "Fear nothing," he said, "this bearded star concerns
me not; rather should it threaten my neighbor the King of the Parthians,
since he is hairy and I am bald."
In the year 837 one of these mysterious visitants appeared in the
Heavens. It was in the reign of Lewis the Debonair. Directly the King
perceived the comet, he sent for an astrologer, and asked what he was to
conclude from the apparition. As the answers were unsatisfactory he
tried to avert the augury by prayers to Heaven, by ordaining a general
fast to all his Court, and by building churches. Notwithstanding, he
died three years later, and the historians profited by this slender
coincidence to set up a correlation between the fatal star and the death
of the Sovereign. This comet, famous in history, is no other than that
of Halley, in one of its appearances.
This comet returned to explore the realms near the Sun in 1066, at the
moment when William of Normandy was undertaking the Conquest of England,
and was misguided enough to go across and reign in London, instead of
staying at home and annexing England, thus by his action founding the
everlasting rivalry between France and this island. A beneficial
influence was attributed to the comet in the Battle of Hastings.
A few centuries later it again came into sight from the Earth, in 1456,
three years after the capture of Constantinople by the Turks. Feeling
ran high in Europe, and this celestial omen was taken for a proof of the
anger of the Almighty. The moment was decisive; the Christians had to be
rescued from a struggle in which they were being worsted. At this
conjuncture, Pope Calixtus resuscitated a prayer that had fallen into
disuse, the _Angelus_; and ordered that the bells of the churches should
be rung each day at noon, that the Faithful might join at the same hour
in prayer against the Turks and the Comet. This custom has lasted down
to our own day.
Again, to the comet of 1500 was attributed the tempest that caused the
death of Bartholomew Diaz, a celebrated Portuguese navigator, who
discovered the Cape of Good Hope.
In 1528 a bearded star of terrific aspect alarmed the world, and the
more serious spirits were influenced by this menacing comet, which
burned in the Heavens like "a great and gory sword." In a chapter on
Celestial Monsters the celebrated surgeon Ambroise Paré describes this
awful phenomenon in terms anything but seductive, or reassuring, showing
us the menacing sword surrounded by the heads it had cut off (Fig. 50).
[Illustration: FIG. 50.--What our Ancestors saw in a Comet.
_After Ambroise Paré (1528)._]
[Illustration: FIG. 51.--Prodigies seen in the Heavens by our
Forefathers.]
Omens of battle, 1547.
Deer and warriors, July 19, 1550.
Cavalry, and a bloody branch crossing the sun, June 11, 1554.]
Our fathers saw many other prodigies in the skies; their descendants,
less credulous, can study the facsimile reproduced in Fig. 51, of the
drawings published in the year 1557 by Conrad Lycosthenes in his curious
Book of Prodigies.
So, too, it is asserted that Charles V renounced the jurisdiction of his
Estates, which were so vast that "the Sun never slept upon them,"
because he was terrified by the comet of 1556 which burned in the skies
with an alarming brilliancy, into passing the rest of his days in prayer
and devotion.
It is certain that comets often exhibit very strange characteristics,
but the imagination that sees in them such dramatic figures must indeed
be lively. In the Middle Ages and the Renaissance these were swords of
fire, bloody crosses, flaming daggers, etc., all horrible objects ready
to destroy our poor human race!
At the time of the Romans, Pliny made some curious distinctions between
them: "The Bearded Ones let loose their hair like a majestic beard; the
Javelin darts forth like an arrow; if the tail is shorter and ends in a
point, it is called the Sword; this is the palest of all the Comets; it
shines like a sword, without rays; the Plate or Disk is named in
conformity with its figure; its color is amber, the Barrel is actually
shaped like a barrel, as it might be in smoke, with light streaming
through it; the Horn imitates the figure of a horn erected in the sky,
and the Lamp that of a burning flame; the Equine represents a horse's
mane, shaken violently with a circular motion. There are bristled
comets; these resemble the skins of beasts with the fur on them, and are
surrounded by a nebulosity. Lastly, the tails of certain comets have
been seen to menace the sky in the form of a lance."
These hairy orbs that appear in all directions, and whose trajectories
are sometimes actually perpendicular to the plane of the ecliptic,
appear to obey no regular law. Even in the seventeenth century the
perspicacious Kepler had not divined their true character, seeing in
them, like most of his contemporaries, emanations from the earth, a sort
of vapor, losing itself in space. These erratic orbs could not be
assimilated with the other members of our grand solar family where,
generally speaking, everything goes on in regular order.
And even in our own times, have we not seen the people terrified at the
sight of a flaming comet? Has not the end of the world by the agency of
comets been often enough predicted? These predictions are so to speak
periodic; they crop up each time that the return of these cosmical
formations is announced by the astronomers, and always meet with a
certain number of timid souls who are troubled as to our destinies.
* * * * *
To-day we know that these wanderers are subject to the general laws
that govern the universe. The great Newton announced that, like the
planets, they were obedient to universal attraction; that they must
follow an extremely elongated curve, and return periodically to the
focus of the ellipse. From the basis of these data Halley calculated the
progress of the comet of 1682, and ascertained that its motions
presented such similarity with the apparitions of 1531 and 1607, that he
believed himself justified in identifying them and in announcing its
return about the year 1759. Faithful to the call made upon it,
irresistibly attracted by the Orb of Day, the comet, at first pale, then
ardent and incandescent, returned at the date assigned to it by
calculation, three years after the death of the illustrious astronomer.
Shining upon his grave it bore witness to the might of human thought,
able to snatch the profoundest secrets from the Heavens!
This fine comet returns every seventy-six years, to be visible from the
Earth, and has already been seen twenty-four times by the astonished
eyes of man. It appears, however, to be diminishing in magnitude. Its
last appearance was in 1835, and we shall see it again in 1910, a little
sooner than its average period, the attraction of Jupiter having this
time slightly accelerated its course, while in 1759 it retarded it.
The comets thus follow a very elongated orbit, either elliptic, turning
round the Sun, or parabolic, dashing out into space. In the first case,
they are periodic (Fig. 52), and their return can be calculated. In the
second they surprise us unannounced, and return to the abysses of
eternity to reappear no more.
[Illustration: FIG. 52.--The orbit of a Periodic Comet.]
Their speed is even greater than that of the planets, it is equivalent
to this, multiplied by the square root of 2, that is to say by 1.414.
Thus at the distance of the Earth from the Sun this velocity = 29,500
meters (18 miles) per second, multiplied by the above number, that is,
41,700 meters (over 25 miles). At the distance of Mercury it = 47 ×
1.414 or 66,400 meters (over 40 miles) per second.
Among the numerous comets observed, we do not as yet know more than some
twenty of which the orbit has been determined. Periodicity in these
bearded orbs is thus exceptional, if we think of the innumerable
multitude of comets that circle through the Heavens. Kepler did not
exaggerate when he said "there are as many comets in the skies as there
are fishes in the sea." These scouts of the sidereal world constitute a
regular army, and if we are only acquainted with the dazzling generals
clad in gold, it is because the more modest privates can only be
detected in the telescope. Long before the invention of the latter,
these wanderers in the firmament roamed through space as in our own day,
but they defied the human eye, too weak to detect them. Then they were
regarded as rare and terrible objects that no one dared to contemplate.
To-day they may be counted by hundreds. They have lost in prestige and
in originality; but science is the gainer, since she has thus endowed
the solar system with new members. No year passes without the
announcement of three or four new arrivals. But the fine apparitions
that attract general attention by their splendor are rare enough.
These eccentric visitors do not resemble the planets, for they have no
opaque body like the Earth, Venus, Mars, or any of the rest. They are
transparent nebulosities, of extreme lightness, without mass nor
density. We have just photographed the comet of the moment, July, 1903:
the smallest stars are visible through its tail, and even through the
nucleus.
They arrive in every direction from the depths of space, as though to
reanimate themselves in the burning, luminous, electric solar center.
Attracted by some potent charm toward this dazzling focus, they come
inquisitive and ardent, to warm themselves at its furnace. At first pale
and feeble, they are born again when the Sun caresses them with his
fervid heat. Their motions accelerate, they haste to plunge wholly into
the radiant light. At length they burst out luminous and superb, when
the day-star penetrates them with his burning splendor, illuminates them
with a marvelous radiance, and crowns them with glory. But the Sun is
generous. Having showered benefits upon these gorgeous celestial
butterflies that flutter round him as round some altar of the gods, he
grants them liberty to visit other heavens, to seek fresh universes....
The original parabola is converted into an ellipse, if the imprudent
adventurer in returning to the Sun passes near some great planet, such
as Jupiter, Saturn, Uranus, or Neptune, and suffers its attraction. It
is then imprisoned by our system, and can no longer escape from it.
After reenforcement at the solar focus, it must return to the identical
point at which it felt the first pangs of a new destiny. Henceforward,
it belongs to our celestial family, and circles in a closed curve.
Otherwise, it is free to continue its rapid course toward other suns and
other systems.
* * * * *
As a rule, the telescope shows three distinct parts in a comet. There is
first the more brilliant central point, or _nucleus_, surrounded by a
nebulosity called the _hair_, or _brush_, and prolonged in a luminous
appendix stretching out into the _tail_. The _head_ of the comet is the
brush and the nucleus combined.
[Illustration: FIG. 53.--The tails of Comets are opposed to the Sun.]
It is usually supposed that the tail of a comet follows it throughout
the course of its peregrinations. Nothing of the kind. The appendix may
even precede the nucleus; it is always opposite the Sun,--that is to
say, it is situated on the prolongation of a straight line, starting
from the Sun, and passing through the nucleus (Fig. 53). The tail does
not exist, so long as the comet is at a distance from the orb of day;
but in approaching the Sun, the nebulosity is heated and dilates, giving
birth to those mysterious tails and fantastic streamers whose
dimensions vary considerably for each comet. The dilations and
transformations undergone by the tail suggest that they may be due to a
repulsive force emanating from the Sun, an electric charge transmitted
doubtless through the ether. It is as though Phoebus blew upon them
with unprecedented force.
Telescopic comets are usually devoid of tail, even when they reach the
vicinity of the Sun. They appear as pale nebulosities, rounded or oval,
more condensed toward the center, without, however, showing any distinct
nucleus. These stars are only visible for a minute fraction of their
course, when they reach a point not far from the Sun and the terrestrial
orbit.
The finest comets of the last century were those of 1811, 1843, 1858,
1861, 1874, 1880, 1881, and 1882. The Great Comet of 1811, after
spreading terror over certain peoples, notably in Russia, became the
providence of the vine-growers. As the wine was particularly good and
abundant that year, the peasants attributed this happy result to the
influence of the celestial visitant.
In 1843 one of these strange messengers from the Infinite appeared in
our Heavens. It was so brilliant that it was visible in full daylight on
February 28th, alongside of the Sun. This splendid comet was
accompanied by a marvelous rectilinear tail measuring 300,000,000
kilometers (186,000,000 miles) in length, and its flight was so rapid
that it turned the solar hemisphere at perihelion in two hours,
representing a speed of 550 kilometers (342 miles) a second.
But the most curious fact is that this radiant apparition passed so near
the Sun that it must have traversed its flames, and yet emerged from
them safe and sound.
Noteworthy also was the comet of 1858 (Fig. 49), discovered at Florence
by Donati. Its tail extended to a length of 90,000,000 kilometers
(55,900,000 miles), and its nucleus had a diameter of at least 900
kilometers (559 miles). It is a curious coincidence that the wine was
remarkably excellent and abundant in that year also.
The comet of 1861 almost rivaled the preceding.
Coggia's Comet, in 1874, was also remarkable for its brilliancy, but was
very inferior to the last two. Finally, the latest worthy of mention
appeared in 1882. This magnificent comet also touched the Sun, traveling
at a speed of 480 kilometers (299 miles) per second. It crossed the
gaseous atmosphere of the orb of day, and then continued its course
through infinity. On the day of, and that following, its perihelion, it
could be detected with the unaided eye in full daylight, enthroned in
the Heavens beside the dazzling solar luminary. For the rest, it was
neither that of 1858 nor of 1861.
Since 1882 we have not been favored with a visit from any fine comet;
but we are prepared to give any such a reception worthy of their
magnificence: first, because now that we have fathomed them we are no
longer awestruck; second, because we would gladly study them more
closely.
* * * * *
In short, these hirsute stars, whose fantastic appearance impressed the
imagination of our ancestors so vividly, are no longer formidable. Their
mass is inconsiderable; they seem to consist mainly of the lightest of
gases. Analysis of their incandescence reveals a spectrum closely
resembling that of many nebulæ; the presence of carbon is more
particularly obvious. Even the nucleus is not solid, and is often
transparent.
It is fair to say that the action of a comet might be deleterious if one
of these orbs were to arrive directly upon us. The transformation of
motion into heat, and the combination of the cometary gases with the
oxygen of our atmosphere might produce a conflagration, or a general
poisoning of the atmosphere.
But the collision of a comet with a planet is almost an impossibility.
This phenomenon could only occur if the comet crossed the planetary
orbit at the exact moment at which the planet was passing. When we
think of the immensity of space, of the extraordinary length of way
traversed by a world in its annual journey round the Sun, and the speed
of its rotation, we see why this coincidence is hardly likely to occur.
Thus, among the hundreds of comets catalogued, a few only cut the
terrestrial orbit. One of them, that of 1832, traversed the path of our
globe in the nights of October 29 and 30 in that year; but the Earth
only passed the same point thirty days later, and at the critical period
was more than 80,000,000 kilometers (50,000,000 miles) away from the
comet.
On June 30, 1861, however, the Earth passed through the extremity of the
tail of the Great Comet of that year. No one even noticed it. The
effects were doubtless quite immaterial.
In 1872 we were to collide with Biela's Comet, lost since 1852; now, as
we shall presently see, we came with flying colors out of that
disagreeable situation, because the comet had disintegrated, and was
reduced to powder. So we may sleep in peace as regards future danger
likely to come to us from comets. There is little fear of the
destruction of humanity by these windy bags.
These ethereal beauties whose blond locks float carelessly upon the
azure night are not concerned with us; they seem to have no other
preoccupation than to race from sun to sun, visiting new Heavens,
indifferent to the astonishment they produce in us. They speed
restlessly and tirelessly through infinity; they are the Amazons of
space.
What suns, what worlds must they have visited since the moment of their
birth! If these splendid fugitives could relate the story of their
wanderings, how gladly should we listen to the enchanting descriptions
of the various abodes they have journeyed to! But alas! these mysterious
explorers are dumb; they tell none of their secrets, and we must needs
respect their enigmatic silence.
Yet, some of them have left us a modest token of remembrance, an almost
impalpable nothing, sufficient, however, to enable us to address our
thanks to the considerate messenger.
* * * * *
Can there be any one upon the Earth who has not been struck by the
phosphorescent lights that glide through the somber night, leaving a
brilliant silver or golden track--the luminous, ephemeral trail of a
meteor?
Sometimes, when Night has silently spread the immensity of her wings
above the weary Earth, a shining speck is seen to detach itself in the
shades of evening from the starry vault, shooting lightly through the
constellations to lose itself in the infinitude of space.
[Illustration: FIG. 54.--A Meteor.]
These bewitching sparks attract our eyes and chain our senses.
Fascinating celestial fireflies, their dainty flames dart in every
direction through space, sowing the fine dust of their gilded wings upon
the fields of Heaven. They are born to die; their life is only a breath;
yet the impression which they make upon the imagination of mortals is of
the profoundest.
The young girl dreaming in the delicious tranquillity of the transparent
night smiles at this charming sister in the Heavens (Fig. 54). What can
not this adorable star announce to the tender and loving heart? Is it
the shy messenger of the happiness so long desired? Its unpremeditated
appearance fills the soul with a ray of hope and makes it tremble. It is
a golden beam that glides into the heart, expanding it in the thrills of
a sudden and ephemeral pleasure.... The radiant meteor seems to quit the
velvet of the deep blue sky to respond to the appeal of the imploring
voice that seeks its succor.
What secrets has it not surprised! And who bears malice against it? It
is the friend of the betrothed who invoke its passage to confide their
wishes, and associate it with their dreams. Tradition holds that if a
wish be formulated during the visible passage of a meteor it will
certainly be fulfilled before the year is out. Between ourselves,
however, this is but a surviving figment of the ancestral imagination,
for this celestial jewel takes no such active part in the doings of
Humanity.... Besides, try to express a wish distinctly in a second!
It is a curious fact that while comets have so often spread terror on
the Earth, shooting stars should on the contrary have been regarded with
benevolent feelings at all times. And what is a shooting star? These
dainty excursionists from the celestial shores are not, as is supposed,
true stars. They are atoms, nothings, minute fragments deriving in
general from the disintegration of comets. They come to us from a vast
distance, from millions on millions of miles, and circle in swarms
around the Sun, following a very elongated ellipse which closely
resembles that of the cometary orbit. Their flight is extremely rapid,
reaching sometimes more than 40 kilometers (25 miles) per second, a
cometary speed that is, as we have seen, greatly above that of our
terrestrial vehicle, which amounts to 29 to 30 kilometers (about 19
miles).
These little corpuscles are not intrinsically luminous; but when the
orbit of a swarm of meteors crosses our planet, a violent shock arises,
the speed of which may be as great as 72 kilometers (45 miles) in the
first second if we meet the star shower directly; the average rate,
however, does not exceed 30 to 40 kilometers (19 to 25 miles), for these
meteors nearly always cross our path obliquely. The height at which they
arrive is usually 110 kilometers (68 miles), and 80 kilometers (50
miles) at the moment of disappearance of the meteor; but shooting stars
have been observed at 300 kilometers (186 miles).
The friction caused by this collision high up in the atmosphere
transforms the motion into heat. The molecules incandesce, and burn like
true stars with a brilliancy that is often magnificent.
But their glory is of short duration. The excessive heat resulting from
the shock consumes the poor firefly; its remains evaporate, and drop
slowly to the Earth, where they are deposited on the surface of the soil
in a sort of ferruginous dust mixed with carbon and nickel. Some one
hundred and forty-six milliards of them reach us annually, as seen by
the unaided eye, and many more in the telescope; the effect of these
showers of meteoric matter is an insensible increase in the mass of our
globe, a slight lessening of its rotary motion, and the acceleration of
the lunar movements of revolution.
Although the appearance of shooting stars is a common enough phenomenon,
visible every night of the year, there are certain times when they
arrive in swarms, from different quarters of the sky. The most
remarkable dates in this connection are the night of August 10th and the
morning of November 14th. Every one knows the shooting stars of August
10th, because they arrive in the fine warm summer evenings so favorable
to general contemplation of the Heavens. The phenomenon lasts till the
12th, and even beyond, but the maximum is on the 10th. When the sky is
very clear, and there is no moon, hundreds of shooting stars can be
counted on those three nights, sometimes thousands. They all seem to
come from the same quarter of the Heavens, which is called the
_radiant_, and is situated for the August swarm in the constellation of
Perseus, whence they have received the name of _Perseids_. Our
forefathers also called them the tears of St. Lawrence, because the
feast of that saint is on the same date. These shooting stars describe a
very elongated ellipse, and their orbit has been identified with that of
the Great Comet of 1862.
The shower of incandescent asteroids on November 14th is often much more
abundant than the preceding. In 1799, 1833, and 1866, the meteors were
so numerous that they were described as showers of rain, especially on
the first two dates. For several hours the sky was furrowed with falling
stars. An English mariner, Andrew Ellicot, who made the drawing we
reproduce (Fig. 55), described the phenomenon as stupendous and alarming
(November 12, 1799, 3 A.M.). The same occurred on November 13, 1833. The
meteors that scarred the Heavens on that night were reckoned at 240,000.
These shooting stars received the name of _Leonids_, because their
radiant is situated in the constellation of the Lion.
[Illustration: FIG. 55.--Shooting Stars of November 12, 1799.
_From a contemporary drawing._]
This swarm follows the same orbit as the comet of 1866, which travels as
far as Uranus, and comes back to the vicinity of the Sun every
thirty-three years. Hence we were entitled to expect another splendid
apparition in 1899, but the expectations of the astronomers were
disappointed. All the preparations for the appropriate reception of
these celestial visitors failed to bring about the desired result. The
notes made in observatories, or in balloons, admitted of the
registration of only a very small number of meteors. The maximum was
thirteen. During that night, some 200 shooting stars were counted. There
were more in 1900, 1901, and, above all, in 1902. This swarm has become
displaced.
The night of November 27th again is visited by a number of shooting
stars that are the disaggregated remains of the Comet of Biela. This
comet, discovered by Biela in 1827, accomplished its revolution in six
and a half years, and down to 1846 it responded punctually to the
astronomers who expected its return as fixed by calculation. But on
January 13, 1846, the celestial wanderer broke in half: each fragment
went its own way, side by side, to return within sight from the Earth in
1852. It was their last appearance. That year the twin comets could
still be seen, though pale and insignificant. Soon they vanished into
the depths of night, and never appeared again. They were looked for in
vain, and were despaired of, when on November 27, 1872, instead of the
shattered comet, came a magnificent rain of shooting stars. They fell
through the Heavens, numerous as the flakes of a shower of snow.
The same phenomenon recurred on November 27, 1885, and confirmed the
hypothesis of the demolition and disaggregation of Biela's Comet into
shooting stars.
* * * * *
There is an immense variety in the brilliancy of the shooting stars,
from the weak telescopic sparks that vanish like a flash of lightning,
to the incandescent _bolides_ or _fire-balls_ that explode in the
atmosphere.
Fig. 56 shows an example of these, and it represents a fire-ball
observed at the Observatory of Juvisy on the night of August 10, 1899.
It arrived from Cassiopeia, and burst in Cepheus.
This phenomenon may occur by day as well as by night. It is often
accompanied by one or several explosions, the report of which is
sometimes perceptible to a considerable distance, and by a shower of
meteorites. The globe of fire bursts, and splits up into luminous
fragments, scattered in all directions. The different parts of the
fire-ball fall to the surface of the Earth, under the name of aerolites,
or rather of uranoliths, since they arrive from the depths of space, and
not from our atmosphere.
From the most ancient times we hear of showers of uranoliths to which
popular superstitions were attached; and the Greeks even gave the name
of _Sideros_ to iron, the first iron used having been sidereal.
[Illustration: FIG. 56.--Fire-Ball seen from the Observatory at Juvisy,
August 10, 1899.]
[Illustration: FIG. 57.--Explosion of a Fire-Ball above Madrid,
February 10, 1896.]
No year passes without the announcement of several showers of
uranoliths, and the phenomenon sometimes causes great alarm to those who
witness it. One of the most remarkable explosions is that which occurred
above Madrid, February 10, 1896, a fragment from which, sent me by M.
Arcimis, Director of the Meteorological Institute, fell immediately in
front of the National Museum (Fig. 57). The phenomenon occurred at 9.30
A.M., in brilliant sunshine. The flash of the explosion was so dazzling
that it even illuminated the interior of the houses; an alarming clap of
thunder was heard seventy seconds after, and it was believed that an
explosion of dynamite had occurred. The fire-ball burst at a height of
fourteen miles, and was seen as far as 435 miles from Madrid!
In one of Raphael's finest pictures (_The Madonna of Foligno_) a
fire-ball may be seen beneath a rainbow (Fig. 58), the painter wishing
to preserve the remembrance of it, as it fell near Milan, on September
4, 1511. This picture dates from 1512.
The dimensions of these meteorites vary considerably; they are of all
sizes, from the impalpable dust that floats in the air, to the enormous
blocks exposed in the Museum of Natural History in Paris. Many of them
weigh several million pounds. That represented below fell in Mexico
during the shower of meteors of November 27, 1885. It weighed about four
pounds.
[Illustration: FIG. 58.--Raphael's Fire-Ball (_The Madonna of
Foligno_).]
These bolides and uranoliths come to us from the depths of space; but
they do not appear to have the same origin as the shooting stars. They
may arise from worlds destroyed by explosion or shock, or even from
planetary volcanoes. The lightest of them may have been expelled from
the volcanoes of the Moon. Some of the most massive, in which iron
predominates, may even have issued from the bowels of the Earth,
projected into space by some volcanic explosion, at an epoch when our
globe was perpetually convulsed by cataclysms of extraordinary violence.
They return to us to-day after being removed from the Earth to distances
proportional to the initial speed imparted to them. This origin seems
the more admissible as the stones that fall from the skies exhibit a
mineral composition identical with that of the terrestrial materials.
[Illustration: FIG. 59.--A Uranolith.]
In any case, these uranoliths bring us back at least by their fall to
our Earth, and from henceforward we will remain upon it, to study its
position in space, and to take account of the place it fills in the
Universe, and of the astronomical laws that govern our destiny.
CHAPTER VIII
THE EARTH
Our grand celestial journey lands us upon our own little planet, on this
globe that gravitates between Mars and Venus (between War and Love),
circulating like her brothers of the solar system, around the colossal
Sun.
The Earth! The name evokes in us the image of Life, and calls up the
theater of our activities, our ambitions, our joys and sorrows. Does it
not, in fact, to ignorant eyes, represent the whole of the universe?
And yet, what is the Earth?
The Earth is a star in the Heavens. We learned this much in our first
lesson. It is a globe of opaque material, similar to the planets
Mercury, Venus, Mars, Jupiter, etc., as previously described. Isolated
on all sides in space, it revolves round the Sun, along a vast orbit
that it accomplishes in a year. And while it thus glides along the lines
of solar attraction, the terrestrial ball rotates rapidly upon itself in
twenty-four hours.
These statements may appear dubious at first sight, and contradictory to
the evidence of our senses.
Now that the surface of the Earth has been explored in all directions,
there is no longer room to doubt that it is a globe, a sort of ball that
we adhere to. A journey round the world is common enough to-day, and
always yields the most complete evidence of the spherical nature of the
Earth. On the other hand, the curvature of the seas is a no less certain
proof. When a ship reaches the dark-blue line that appears to separate
the sky from the ocean, it seems to be hanging on the horizon. Little by
little, however, as it recedes, it drops below the horizon line; the
tops of the masts being the last to disappear. The observer on board
ship witnesses the same phenomenon. The low shores are first to
disappear, while the high coasts and mountains are much longer visible.
The aspect of the Heavens gives another proof of the Earth's rotundity.
As one travels North or South, new stars rise higher and higher above
the horizon in the one direction or the other, and those which shine in
the latitude one is leaving, gradually disappear. If the surface of the
Earth were flat, the ships on the sea would be visible as long as our
sight could pierce the distance, and all the stars of the Heavens would
be equally visible from the different quarters of the world.
Lastly, during the eclipses of the Moon, the shadow projected by the
Earth upon our satellite is always round. This is another proof of the
spherical nature of the terrestrial globe.
We described the Earth as an orb in the Heavens, similar to all the
other planets of the great solar family. We see these sister planets of
our world circulating under the starry vault, like luminous points whose
brilliancy is sometimes dazzling. For us they are marvelous celestial
birds hovering in the ether, upheld by invisible wings. The Earth is
just the same. It is supported by nothing. Like the soap-bubble that
assumes a lovely iridescence in the rays of the Sun, or, better, like
the balloon rapidly cleaving the air, it is isolated from every kind of
support.
Some minds have difficulty in conceiving this isolation, because they
form a false notion of weight.
The astronomers of antiquity, who divined it, knew not how to prevent
the Earth from falling. They asked anxiously what the strong bands
capable of holding up this block of no inconsiderable weight could be.
At first they thought it floated on the waters like an island. Then they
postulated solid pillars, or even supposed it might turn on pivots
placed at the poles. But on what would all these imaginary supports have
rested? All these fanciful foundations of the Earth had to be given up,
and it was recognized as a globe, isolated in every part. This illusion
of the ancients, which still obtains for a great many citizens of our
globule, arises, as we said, from a false conception of weight.
Weight and attraction are one and the same force.
A body can only fall when it is attracted, drawn by a more important
body. Now, in whatever direction we may wander upon the globe, our feet
are always downward. _Down_ is therefore the _center_ of the Earth.
The terrestrial globe may be regarded as an immense ball of magnet, and
its attraction holds us at its surface. We weigh toward the center. We
may travel over this surface in all directions; our feet will always be
below, whatever the direction of our steps. For us, "below" is the
inside of our planet, and "above" is the immensity of the Heavens that
extend above our heads, right round the globe.
This once understood, where could the Earth fall to? The question is an
absurdity. "Below" being toward the center, it would have to fall out of
itself.
Let us then picture the Earth as a vast sphere, detached from all that
exists around it, in the infinity of the Heavens. A point diametrically
opposed to another is called its _antipodes_. New Zealand is
approximately the antipodes to France. Well, for the inhabitants of New
Zealand and of France the top is reciprocally opposed, and the bottom,
or the feet, are diametrically in opposition. And yet, for one as for
the other, the bottom is the soil they are held to, and the top is
space above their heads.
The Earth turns on itself in twenty-four hours. Whatever is above us,
_e.g._, at midday, we call high; twelve hours later, at midnight, we
give the same qualification to the part of space that was under our feet
at noon. What is in the sky, and over our heads, at a given hour, is
under our feet, and yet always in the sky, twelve hours later. Our
position, in relation to the space that surrounds us, changes from hour
to hour, and "top" and "bottom" vary also, relatively to our position.
Our planet is thus a ball, slightly flattened at the poles (by about
1/292). Its diameter, at the equator, is 12,742 kilometers (7,926
miles); from one pole to the other is a little less, owing to the
flattening of the polar caps. The difference is some 43 kilometers
(about 27 miles).
Its circumference is 40,000 kilometers (24,900 miles). This ball is
surrounded by an aerial envelope, the atmosphere, the height of which
can not be less than 300 kilometers (186 miles), according to the
observations made on certain shooting stars.
We all know that this layer of air, at the bottom of which we live, is a
beautiful azure blue that seems to separate us from the sidereal abyss,
spreading over our heads in a kind of vault that is often filled with
clouds, and giving the illusion of resting far off on the circle of the
horizon. But this is only an illusion. In reality, there is neither
vault nor horizon; space is open in all directions. If the atmosphere
did not exist, or if it were completely transparent, we should see the
stars by day as by night, for they are continually round us, at noon as
at midnight, and we can see them in the full daylight, with the help of
astronomical instruments. In fact, certain stars (the radiant Venus and
the dazzling Jupiter) pierce the veil of the atmosphere, and are visible
with the unaided eye in full daylight.
The terrestrial surface is 510,000,000 square kilometers (200,000,000
square miles). The waters of the ocean cover three-quarters of this
surface, _i.e._, 383,200,000 square kilometers (150,000,000 square
miles), and the continents only occupy 136,600,000 square kilometers
(55,000 square miles). France represents about the thousandth part of
the total superficies of the globe.
Despite the asperities of mountain ranges, and the abysses hollowed out
by the waters, the terrestrial globe is fairly regular, and in relation
to its volume its surface is smoother than that of an orange. The
highest summits of the Himalaya, the profoundest depths of the somber
ocean, do not attain to the millionth part of its diameter.
In weight, the Earth is five and a half times heavier than would be a
globe of water of the same dimensions. That is to say:
6,957,930,000,000,000,000,000,000 kilograms
(6,833,000,000,000,000,000,000 tons).
The atmospheric atmosphere with which it is surrounded represents.
6,263,000,000,000,000,000 kilograms
(6,151,000,000,000,000 tons).
Each of us carries an average weight of some 17,000 kilograms (16 tons)
upon his shoulders. Perhaps some one will ask how it is that we are not
crushed by this weight, which is out of all proportion with our
strength, but to which, nevertheless, we appear insensible. It is
because the aerial fluid enclosed within our bodies exerts a pressure
equal and opposite to the external atmospheric pressure, and these
pressures are at equilibrium.
The Earth is characterized by no essential or particular differences
relatively to the other worlds of our system. Like Venus of the limpid
rays, like the dazzling Jupiter, like all the planets, she courses
through space, carrying into Infinitude our hopes and destinies. Bigger
than Mercury, Venus, and Mars, she presents a very modest figure in
comparison with the enormous Jupiter, the strange system of Saturn, of
Uranus, and even of Neptune. For us her greatest interest is that she
serves as our residence, and if she were not our habitation we should
scarcely notice her. Dark in herself, she burns at a distance like a
star, returning to space the light she receives from the Sun. At the
distance of our satellite, she shines like an enormous moon, fourteen
times larger and more luminous than our gentle Phoebe. Observed from
Mercury or Venus, she embellishes the midnight sky with her sparkling
purity as Jupiter does for us. Seen from Mars, she is a brilliant
morning and evening star, presenting phases similar to those which Mars
and Venus show from here. From Jupiter, the terrestrial globe is little
more than an insignificant point, nearly always swallowed up in the
solar rays. As to the Saturnians, Uranians, and Neptunians, if such
people exist, they probably ignore our existence altogether. And in all
likelihood it is the same for the rest of the universe.
We must cherish no illusions as to the importance of our natal world. It
is true that the Earth is not wanting in charm, with its verdant plains
enameled in the delicious tones of a robust and varied vegetation, its
plants and flowers, its spring-time and its birds, its limpid rivers
winding through the meadows, its mountains covered with forests, its
vast and profound seas animated with an infinite variety of living
creatures. The spectacle of Nature is magnificent, superb, admirable
and marvelous, and we imagine that this Earth fills the universe, and
suffices for it. The Sun, the Moon, the stars, the boundless Heavens,
seem to have been created for us, to charm our eyes and thoughts, to
illumine our days, and shed a gentle radiance upon our nights. This is
an agreeable illusion of our senses. If our Humanity were extinguished,
the other worlds of the Heavens, Venus, Mars, etc., would none the less
continue to gravitate in the Heavens along with our defunct planet, and
the close of human life (for which everything seems to us to have been
created) would not even be perceived by those other worlds, that
nevertheless are our neighbors. There would be no revolution, no
cataclysm. The stars would go on shining in the firmament, just as they
do to-day, shedding their divine light over the immensity of the
Heavens. Nothing would be changed in the general aspect of the Universe.
The Earth is only a modest atom, lost in the innumerable army of the
worlds and suns that people the universe.
* * * * *
Every morning the Sun rises in the East, setting fire with his ardent
rays to the sky, which is dazzling with his splendor. He ascends through
space, reaches a culminating point at noon, and then descends toward the
West, to sink at night into the purple of the sunset.
And then the stars, grand lighthouses of the Heavens, in their turn
incandesce. They too rise in the East, ascend the vault of Heaven, and
then descend to the West, and vanish. All the orbs, Sun, Moon, planets,
stars, appear to revolve round us in twenty-four hours.
This journey of the orbs around us is only an illusion of the senses.
Whether the Earth be at rest, and the sky animated with a rotary
movement round her, or whether, on the contrary, the stars are fixed,
and the Earth in motion, in either case, for us appearances are the
same. If the Earth turns, carrying all that pertains to it in its
motion--the seas, the atmosphere, the clouds, and ourselves,--we are
unable to perceive it, because all the objects that surround us keep
their respective positions among themselves. Hence we must resort to
logic, and reason out the two hypotheses.
For the accomplishment of this rapid journey of the Sun and stars around
the Earth, it would be necessary that all the orbs of the sky should be
in some way attached to a vault, or to circles, as was formerly
supposed. This conception is childish. The peoples of antiquity had no
notion of the size of the universe, and their error is almost excusable.
The distance separating Heaven from the Infernal Regions has been
measured, according to Hesiod, by Vulcan's anvil, which fell from the
skies to the Earth in nine days and nine nights, and it would have
taken as long again to continue its journey from the surface of the
Earth to the bowels of Hades.
To-day we have a more exact notion of the grandeur of the Universe. We
know that millions and trillions of miles separate the stars from one
another. And by representing these distances, we can form some idea of
the difficulty there would be in admitting the rotation of the universe
round the Earth.
The distance from here to the Sun is 149,000,000 kilometers (93,000,000
miles). In order to turn in twenty-four hours round the Earth, that orb
would have to fly through Space at a velocity of more than 10,000
kilometers (6,200 miles) a second.
Yes! the Sun, splendid orb, source of our existence and of that of all
the planets, a colossal globe, over a million times more voluminous than
the Earth, and 324 thousand times heavier, would have to accomplish this
immense revolution in order to turn round the minute point that is our
lilliputian world!
This in itself would suffice to convince us of the want of logic in such
an argument. But the Sun is not alone in the Heavens. We should have to
suppose that all the planets and all the stars were engaged in the same
fantastic motions.
Jupiter is about five times as far off as the Sun; his velocity would
have to be 53,000 kilometers (32,860 miles) per second.
Neptune, thirty times farther off, would have to execute 320,000
kilometers (198,000 miles) per second.
The nearest star, [alpha] of the Centaur, situated at a distance 275,000
times that of the Sun, would have to run, to fly through space, at a
rate of 2,941,000,000 kilometers (1,823,420,000 miles) per second.
All the other stars are incomparably farther off, at infinity.
And this fantastic rotation would all be accomplished round a minute
point!
To put the problem in this way is to solve it. Unless we deny the
astronomic measures, and the most convincing geometric operations, the
Earth's diurnal motion of rotation is a certainty.
To suppose that the stars revolve round the Earth is to suppose, as one
author humorously suggests, that in order to roast a pheasant the
chimney, the kitchen, the house, and all the countryside must needs turn
round it.
If the Earth turns in twenty-four hours upon itself, a point upon the
equator would simply travel at a rate of 465 meters (1,525 feet) per
second. This speed, while considerable in comparison with the movements
observed upon the surface of our planet, is as nothing compared with
the fantastic rapidity at which the Sun and stars would have to move, in
order to rotate round our globe.
Thus we have to choose between these two hypotheses: either to make the
entire Heavens turn round us in twenty-four hours, or to suppose our
globe to be animated by a motion of rotation upon itself. For us, the
impression is the same, and as we are insensible to the motion of the
Earth, its immobility would seem almost natural to us. So that, in last
resort, here as in many other instances, the decision must be made by
simple common sense. Science long ago made its choice. Moreover, all the
progress of Astronomy has confirmed the rotary movement of the Earth in
twenty-four hours, and its movement of revolution round the Sun in a
year; while at the same time a great number of other motions have been
discovered for our wandering planet.
The learned philosophers of antiquity divined the double movement of our
planet. The disciples of Pythagoras taught it more than two thousand
years ago, and the ancient authors quote among others Nicetas of
Syracuse, and Aristarchus of Samos, as being among the first to promote
the doctrine of the Earth's movement. But at that remote period no one
had any idea of the real distances of the stars, and the argument did
not seem to be based on any adequate evidence. Ptolemy, after a long
discussion of the diurnal motion of our planet, refutes it, giving as
his principal reason that if the Earth turned, the objects that were not
fixed to its surface would appear to move in a contrary direction, and
that a body shot into the air would fall back to the West of its
starting-point, the Earth having turned meantime from West to East. This
objection has no weight, because the Earth controls not only all the
objects fixed to the soil, but also the atmosphere, and the clouds that
surround it like a light veil, and all that exists upon its surface. The
atmosphere, the clouds, the waters of the ocean, things and beings, all
are adherent to it and make one body with it, participating in its
movement, as sometimes happens to ourselves in the compartment of a
train, or the car of an aerostat. When, for instance, we drop an object
out of such a car, this object, animated with the acquired velocity,
does not fall to a point below the aerostat, but follows the balloon, as
though it were gliding along a thread. The author has made this
experiment more than once in aerial journeys.
Thus, the hypothesis of the Earth's motion has become a certainty. But
in addition to reasoning, direct proof is not wanting.
1. The spheroidal shape of the Earth, slightly flattened at the poles
and swollen at the equator, has been produced by the rotary motion, by
the centrifugal force that it engenders.
2. In virtue of this centrifugal force, which is at its maximum at the
equator, objects lose a little of their weight in proportion as they are
farther removed from the polar regions where centrifugal force is almost
_nil_.
3. In virtue of this same centrifugal force, the length of the pendulum
in seconds is shorter at the equator than in Paris, and the difference
is one of 3 millimeters.
4. A weight abandoned to itself and falling from a certain height,
should follow the vertical if the Earth were motionless. Experiment,
frequently repeated, shows a slight deviation to the East, of the
plumb-line that marks the vertical. We more especially observed this at
the Pantheon during the recent experiments.
5. The magnificent experiment of Foucault at the Pantheon, just renewed
under the auspices of the Astronomical Society of France, demonstrates
the rotary motion of the Earth to all beholders. A sufficiently heavy
ball (28 kilograms, about 60 pounds) is suspended from the dome of the
edifice by an excessively fine steel thread. When the pendulum is in
motion, a point attached to the bottom of the ball marks its passage
upon two little heaps of sand arranged some yards away from the center.
At each oscillation this point cuts the sand, and the furrow gets
gradually longer to the right hand of an observer placed at the center
of the pendulum. The plane of the oscillations remains fixed, but the
Earth revolves beneath, from West to East. The fundamental principle of
this experiment is that the plane in which any pendulum is made to
oscillate remains invariable even when the point of suspension is
turned. This demonstration enables us in some measure to see the Earth
turning under our feet.
The annual displacements of the stars are again confirmatory of the
Earth's motion round the Sun. During the course of the year, the stars
that are least remote from our solar province appear to describe minute
ellipses, in perspective, in the Heavens. These small apparent
variations in the position of the nearest stars reproduce the annual
rotation of the Earth round the Sun, in perspective.
We could adduce further observations in favor of this double movement,
but the proofs just given are sufficiently convincing to leave no doubt
in the mind of the reader.
Nor are these two the only motions by which our globe is rocked in
space. To its diurnal rotation and its annual rotation we may add
another series of _ten more motions_: some very slow, fulfilling
themselves in thousands of years, others, more rapid, being constantly
renewed. It is, however, impossible in these restricted pages to enter
into the detail reserved for more complete works. We must not forget
that our present aim is to sum up the essentials of astronomical
knowledge as simply as possible, and to offer our readers only the "best
of the picking."
* * * * *
The two principal motions of which we have just spoken give us the
measure of time, the day of twenty-four hours, and the year of 365-1/4
days.
The Earth turning upon itself in twenty-four hours from West to East,
presents all its parts in succession to the Sun fixed in space.
Illuminated countries have the day, those opposite, in the shadow of the
Earth, are plunged into night. The countries carried by the Earth toward
the Sun have morning, those borne toward his shadow, evening. Those
which receive the rays of the day-star directly have noon; those which
are just opposite have midnight.
The rotation of our planet in this way gives us the measure of time; it
has been divided arbitrarily into twenty-four periods called hours; each
hour into sixty minutes; each minute into sixty seconds.
In consequence, each country turns in twenty-four hours round the axis
of the Earth. The difference in hours between the different regions of
the globe is therefore regulated by the difference of geographical
position. The countries situated to the West are behind us; the Sun only
gets there after it has shone upon our meridian. When it is midday in
Paris, it is only 11.51 A.M. in London; 11.36 A.M. in Madrid; 11.14 A.M.
at Lisbon; 11.12 A.M. at Mogador; 7.06 A.M. at Quebec; 6.55 A.M. at New
York; 5.14 A.M. in Mexico; and so on. The countries situated to the East
are, on the contrary, ahead of us. When it is noon in Paris, it is
already 56 minutes after midday at Vienna; 1.25 P.M. at Athens; 2.21
P.M. at Moscow; 3.16 P.M. at Teheran; 4.42 P.M. at Bombay; and so on. We
are here speaking of real times, and not of the conventional times.
[Illustration: FIG. 60.--Motion of the Earth round the Sun.]
If we could make the tour of the world in twenty-four hours, starting
at midday from some place to go round the globe, and traveling westward
with the Sun, we should have him always over our heads. In traveling
round the world from West to East, one goes in front of the Sun, and
gains by one day; in taking the opposite direction, from East to West,
one loses a day.
In reality, the exact duration of the Earth's diurnal rotation is
twenty-three hours, fifty-six minutes, four seconds. That is the
sidereal day. But, while turning upon itself, the Earth circulates upon
its orbit, and at the end of a diurnal rotation it is still obliged to
turn during three minutes, fifty-six seconds in order to present exactly
the same meridian to the fixed Sun which, in consequence of the rotary
period of our planet, is a little behind. The solar day is thus one of
twenty-four hours. There are 366 rotations in the year.
And now let us come back to the consequences of the Earth's motion. In
the first place our planet does not turn vertically nor on its side, but
is tipped or inclined a certain quantity: 23° 27'.
Now, throughout its annual journey round the Sun, the inclination
remains the same. That is what produces the seasons and climates. The
countries which have a larger circle to travel over in the hemisphere of
the solar illumination have the longer days, those which have a smaller
circle, shorter days. At the equator there is constantly, and all
through the year, a twelve-hour day, and a night of twelve hours.
[Illustration: FIG. 61.--Inclination of the Earth.]
In summer, the pole dips toward the Sun, and the rays of the orb of day
cover the corresponding hemisphere with their light. Six months later
this same hemisphere is in winter, and the opposite hemisphere is in its
turn presented to the Sun. June 21 is the summer solstice for the
northern hemisphere, and is at the same time winter for the southern
pole. Six months later, on December 21, we have winter, while the
southern hemisphere is completely exposed to the Sun. Between these two
epochs, when the radiant orb shines exactly upon the equator, that is on
March 21, we have the spring equinox, that delicious flowering season
when all nature is enchanting and enchanted; on September 21 we have the
autumn equinox, melancholy, but not devoid of charm.
The terrestrial sphere has been divided into different zones, with which
the different climates are in relation:
1. The tropical zone, which extends 23° 27' from one part to the other
of the equator. This is the hottest region. It is limited by the circle
of the tropics.
2. The temperate zones, which extend from 23° 27' to 66° 23' of
latitude, and where the Sun sets every day.
3. The glacial zones, drawn round the poles, at 66° 33' latitude, where
the Sun remains constantly above or below the horizon for several days,
or even several months. These glacial zones are limited by the polar
circles.
We must add that the _axis_ of the Earth is a straight line that is
supposed to pass through the center of the globe and come out at two
diametrically opposite points called the _poles_. The diurnal rotation
of the Earth is effected round this axis.
The name _equator_ is given to a great circle situated between the two
poles, at equal distance, which divides the globe into two hemispheres.
The equator is divided into 360 parts or degrees, by other circles that
go from one pole to the other. These are the _longitudes_ or meridians
(see Fig. 62). The distance between the equator and the pole is divided
into larger or smaller circles, which have received the name of
_latitudes_, 90 degrees are reckoned on the one side and the other of
the equator, in the direction of the North and South poles,
respectively. The longitudes are reckoned from some point either to East
or West: the latitudes are reckoned North and South, from the equator.
In going from East to West, or inversely, the longitude changes, but in
passing from North to South of any spot, it is the latitude that alters.
[Illustration: FIG. 62.--The divisions of the globe. Longitudes and
latitudes.]
The circles of latitude are smaller in proportion as one approaches the
poles. The circumference of the world is 40,076,600 meters at the
equator. At the latitude of Paris (48° 50') it is only 26,431,900
meters. A point situated at the equator has more ground to travel over
in order to accomplish its rotation in twenty-four hours than a point
nearer the pole.
We have already stated that this velocity of rotation is 465 meters per
second at the equator. At the latitude of Paris it is not more than 305
meters. At the poles it is _nil_.
The longitudes, or meridians, are great circles of equal length,
dividing the Earth into quarters, like the parts of an orange or a
melon. These circumvent the globe, and measure some 40,000,000
(40,008,032) meters. We may remember in passing that the length of the
meter has been determined as, by definition, the ten-millionth part of
the quarter of a celestial meridian.
Thus, while rotating upon itself, the Earth spins round the Sun, along a
vast orbit traced at 149,000,000 kilometers (93,000,000 miles) from the
central focus, a sensibly elliptical orbit, as we have already pointed
out. It is a little nearer the Sun on January 1st than on July 1st, at
its perihelion (_peri_, near, _helios_, Sun), than at its aphelion
(_apo_, far, _helios_, Sun). The difference = 6,000,000 kilometers
(3,720,000 miles), and its velocity is a little greater at perihelion
than at aphelion.
This second motion produces the _year_. It is accomplished in three
hundred and sixty-five days, six hours, nine minutes, nine seconds.
Such is the complete revolution of our planet round the orb of day. It
has received the name of sidereal year. But this is not how we calculate
the year in practical life. The civil year, known also as the tropical
year, is not equivalent to the Earth's revolution, because a very slow
gyratory motion, called "the precession of the equinoxes," the cycle of
which occupies 25,765 years, drags the spring equinox back some twenty
minutes in each year.
The civil year is, accordingly, three hundred and sixty-five days, five
hours, forty-eight minutes, forty-six seconds.
In order to simplify the calendar, this accumulating fraction of five
hours, forty-eight minutes, forty-six seconds (about a quarter day) is
added every four years to a bissextile year (leap-year), and thus we
have uneven years of three hundred and sixty-five, and three hundred and
sixty-six days. Every year of which the figure is divisible by four is a
leap-year. By adding a quarter day to each year, there is a surplus of
eleven minutes, fourteen seconds. These are subtracted every hundred
years by not taking as bissextile those secular years of which the
radical is not divisible by four. The year 1600 was leap-year: 1700,
1800, and 1900 were not; 2000 will be. The agreement between the
calendar and nature has thus been fairly perfect, since the
establishment of the Gregorian Calendar in 1582.
Since the terrestrial orbit measures not less than 930,000,000
kilometers (576,600,000 miles), which must be traversed in a year, the
Earth flies through Space at 2,544,000 kilometers (1,577,280 miles) a
day, or 106,000 kilometers (65,720 miles) an hour, or 29,500 meters (18
miles) per second on an average, a little faster at perihelion, a little
slower at aphelion. This giddy course, a thousand times more rapid than
the speed of an express-train, is effected without commotion, shock, or
noise. Reasoning alone enables us to divine the prodigious movement that
carries us along in the vast fields of the Infinite, in mid-heaven.
Returning to the calendar, it must be remarked in conclusion, that the
human race has not exhibited great sense in fixing the New Year on
January 1. No more disagreeable season could have been selected. And
further, as the ancient Roman names of the months have been preserved,
which in the time of Romulus began with March, the "seventh" month,
"September," is our ninth month; October (the eighth) is the tenth;
November (the ninth) has become the eleventh; and December (the tenth)
has taken the place of the twelfth. Verily, we are not hard to please!
These months, again, are unequal, as every one knows. Witness the
simple expedient of remembering the long and short months, by closing
the left hand and counting the knobs and hollows of the fist, the former
corresponding to the long months, the latter to the short: first knob =
January; first hollow, February; second knob, March; and so on.[12]
[Illustration: FIG. 63.--To find the long and short months.]
Should not the real renewal of the year coincide with the awakening of
Nature, with the spring on the terrestrial hemisphere occupied by the
greater portion of Humanity, with the date of March 21st? Should not the
months be equalized, and their names modified? Why should we not follow
the beautiful evolution dictated by the Sun and by the movement of our
planet? But our poor Earth may roll on a long time yet before its
inhabitants will become reasonable.
CHAPTER IX
THE MOON
It is the delightful hour when all Nature pauses in the tranquil calm of
the silent night.
The Sun has cast his farewell gleams upon the weary Earth. All sound is
hushed. And soon the stars will shine out one by one in the bosom of the
somber firmament. Opposite to the sunset, in the east, the Full Moon
rises slowly, as it were calling our thoughts toward the mysteries of
eternity, while her limpid night spreads over space like a dew from
Heaven.
In the odorous woods, the trees are silhouetted strangely upon the sky,
seeming to stretch their knotted arms toward this celestial beauty. On
the river, smooth as a mirror, wherein the pale Phoebe reflects her
splendor, the maidens go to seek the floating image of their future
spouse. And in response to their prayers, she rends the veil of cloud
that hides her from their eyes, and pours the reflection of her gentle
beams upon the sleeping waters.
From all time the Moon has had the privilege of charming the gaze, and
attracting the particular attention of mortals. What thoughts have not
been wafted to her pale, yet luminous disk? Orb of mystery and of
solitude, brooding over our silent nights, this celestial luminary is at
once sad and splendid in her glacial purity, and her limpid rays provoke
a reverie full of charm and melancholy. Mute witness of terrestrial
destinies, her nocturnal flame watches over our planet, following it in
its course as a faithful satellite.
The human eye first uplifted to the Heavens was struck, above all, with
the brilliancy of this solitary globe, straying among the stars. The
Moon first suggested an easy division of time into months and weeks, and
the first astronomical observations were limited to the study of her
phases.
Daughter of the Earth, the Moon was born at the limits of the
terrestrial nebula, when our world was still no more than a vast gaseous
sphere, and was detached from her at some critical period of colossal
solar tide. Separating with regret from her cradle, but attached to the
Earth by indissoluble ties of attraction, she rotates round us in a
month, from west to east, and this movement keeps her back a little each
day in relation to the stars. If we watch, evening by evening, beginning
from the new moon, we shall observe that she is each night a little
farther to the left, or east, than on the preceding evening. This
revolution of the Moon around our planet produces the phases, and gives
the measure of our months.
[Illustration: FIG. 64.--The Full Moon slowly rises.]
During her monthly journey she always presents the same face to us. One
might think that the fear of losing us had immobilized her globe, and
prevented her from turning. And so we only know of her the vague sketch
of a human face that has been observed through all the ages.
It seems, in fact, as though she were looking down upon us from the
Heavens, the more so as the principal spots of her disk vaguely recall
the aspect of a face. If we try to draw it without the aid of
instruments we observe dark regions and clear regions that each
interprets in his own fashion. To the author, for instance, the full
Moon has the appearance represented in the following figure. The spots
resemble two eyes and the sketch of a nose; resulting in a vague human
figure, as indicated on the lower disk. Others see a man carrying a
bundle of wood, a hare, a lion, a dog, a kangaroo, a sickle, two heads
embracing, etc.[13] But generally speaking, there is a tendency to see a
human figure in it.
If this appearance is helped a little by drawing, it gives the profile
of a man's head fairly well sketched, and furnished with an abundant
crop of hair (Fig. 66). Others go much more into detail, and draw a
woman's head that is certainly too definite, like this of M. Jean Sardou
(Fig. 67). Others, again, like M. Zamboni, see behind the man's profile
the likeness of a young girl being embraced by him (Fig. 68). There is
certainly some imagination about these. And yet, on the first suitable
occasion, look at the Moon through an opera-glass, a few days after the
first quarter, and you will not fail to see the masculine profile just
described, and even to imagine the "kiss in the Moon."
[Illustration: FIG. 65.--The Moon viewed with the unaided eye.]
[Illustration: FIG. 66.--The Man's head in the Moon.]
These vague aspects disappear as soon as the Moon is examined with even
the least powerful instruments: the spots are better defined, and the
illusions of indistinct vision vanish. Compare this direct photograph of
the Moon, taken by the author some years ago (Fig. 69): here is neither
a human figure, man, dog, hare, nor faggot; simply deep geographical
configurations, and in the lower region, a luminous point whence certain
light bands spread out, some being prolonged to a considerable distance.
And yet, from a little way off, does it not form the man's face above
indicated?
[Illustration: FIG. 67.--Woman's head in the Moon.]
From the earliest astronomical observations made with the aid of
instruments by Galileo, in 1609, people tried to find out what the dark
spots could represent, and they were called seas, because water absorbs
light, and reflects it less than _terra firma_. The Moon of itself
possesses no intrinsic light, any more than our planet, and only shines
by the light of the Sun that illuminates it. As it rotates round the
Earth, and constantly changes its position with respect to the Sun, we
see more or less of its illuminated hemisphere, and the result is the
phases that every one knows so well.
[Illustration: FIG. 68.--The kiss in the Moon.]
[Illustration: FIG. 69.--Photograph of the Moon.]
At the commencement of each lunation, the Moon is between the Sun and
the Earth, and its non-illuminated hemisphere is turned toward us. This
is the New Moon, invisible to us; but two days later, the slim crescent
of Diana sheds a gentle radiance upon the Earth. Gradually the crescent
enlarges. When the Moon arrives at right angles with ourselves and with
the Sun, half the illuminated hemisphere is presented to us. This is the
first quarter. At the time of Full Moon, it is opposite the Sun, and we
see the whole of the hemisphere illuminated. Then comes the decline: the
brilliant disk is slightly corroded at first; it diminishes from day to
day, and about a week before the New Moon our fair friend only shows her
profile before she once more passes in front of the Sun: this is the
last quarter.
[Illustration: FIG. 70.--The Moon's Phases.]
When the Moon is crescent, in the first evenings of the lunation, and
after the last quarter, the rest of the disk is visible, illuminated
feebly by a pale luminosity. This is known as the ashy light. It is due
to the shine of the Earth, reflecting the light received from the Sun
into space. Accordingly the ashy light is the reflection of our own sent
back to us by the Moon. It is the reflection of a reflection.
This rotation of the Moon round the Earth is accomplished in
twenty-seven days, seven hours, forty-three minutes, eleven seconds; but
as the Earth is simultaneously revolving round the Sun, when the Moon
returns to the same point (the Earth having become displaced relatively
to the Sun), the Moon has to travel two days longer to recover its
position between the Sun and the Earth, so that the lunar month is
longer than the sidereal revolution of the Moon, and takes twenty-nine
days, twelve hours, forty-four minutes, three seconds. This is the
duration of the sequence of phases.
This revolution is accomplished at a distance of 384,000 kilometers
(238,000 miles). The velocity of the Moon in its orbit is more than 1
kilometer (0.6214 mile) per second. But our planet sweeps it through
space at a velocity almost thirty times greater.
The diameter of the Moon represents 273/1000 that of the Earth, _i.e._,
3,480 kilometers (2,157 miles).
Its surface = 38,000,000 square kilometers (15,000,000 square miles), a
little more than the thirteenth part of the terrestrial surface, which
= 510,000,000 (200,000,000 square miles).
In volume, the Moon is fifty times less than the Earth. Its mass or
weight is only 1/81 that of the terrestrial globe. Its density = 0.615,
relatively to that of the Earth, _i.e._, a little more than three times
that of water. Weight at its surface is very little: 0.174. A kilogram
transported thither would only weigh 174 grams.
* * * * *
At the meager distance of 384,000 kilometers (238,000 miles) that
separates us from it (about thirty times the diameter of the Earth), the
Moon is a suburb of our terrestrial habitation. What does this small
distance amount to? It is a mere step in the universe.
A telegraphic message would get there in one and a half second; a
projectile fired from a gun would arrive in eight days, five hours; an
express-train would be due in eight months, twenty-two days. It is only
the 1/388 part of the distance that separates us from the Sun, and only
the 100/1,000,000 part of the distance of the stars nearest to us. Many
men have tramped the distance that separates us from the Moon. A bridge
of thirty terrestrial globes would suffice to unite the two worlds.
Owing to this great proximity, the Moon is the best known of all the
celestial spheres. Its geographical (or more correctly,
selenographical, _Selene_, moon) map was drawn out more than two
centuries ago, at first in a vague sketch, and afterward with more
details, until to-day it is as precise and accurate as any of our
terrestrial maps of geography.
Before the invention of the telescope, from antiquity to the seventeenth
century, people lost themselves in conjectures as to the nature of this
strange lunar figure. It was held to be a mysterious world, the more
extraordinary in that it always presented the same face to us. Some
compared it to an immense mirror reflecting the image of the Earth.
Others pictured it as a silver star, an enchanted abode where all was
wealth and happiness. For many a long day it was the fashion to think,
quite irrationally, that the inhabitants of the Moon were fifteen times
bigger than ourselves.
The invention of telescopes, however, brought a little order and a grain
of truth into these fantastic assumptions. The first observations of
Galileo revolutionized science, and his discoveries filled the
best-ordered minds with enthusiasm. Thenceforward, the Moon became our
property, a terrestrial suburb, where the whole world would gladly have
installed itself, had the means of getting there been as swift as the
wings of the imagination. It became easy enough to invent a thousand
enchanting descriptions of the charms of our fair sister, and no one
scrupled to do so. Soon, it was observed that the Moon closely resembled
the Earth in its geological features; its surface bristles with sharp
mountain peaks that light up in so many luminous points beneath the rays
of the Sun. Alongside, dark and shaded parts indicate the plains;
moreover, there are large gray patches that were supposed to be seas
because they reflect the solar light less perfectly than the adjacent
countries. At that epoch hardly anything was known of the physical
constitution of the Moon, and it was figured as enveloped with an
atmospheric layer, analogous to that at the bottom of which we carry on
our respiration.
To-day we know that these "seas" are destitute of water, and that if the
lunar globe possesses an atmosphere, it must be excessively light.
The Moon became the favorite object of astronomers, and the numerous
observations made of it authorized the delineation of very interesting
selenographic charts. In order to find one's way among the seas, plains,
and mountains that make up the lunar territory, it was necessary to name
them. The seas were the first to be baptized, in accordance with their
reputed astrological influences. Accordingly, we find on the Moon, the
Sea of Fecundity, the Lake of Death, the Sea of Humors, the Ocean of
Tempests, the Sea of Tranquillity, the Marsh of Mists, the Lake of
Dreams, the Sea of Putrefaction, the Peninsula of Reverie, the Sea of
Rains, etc.
With regard to the luminous parts and the mountains, it was at first
proposed to call them after the most illustrious astronomers, but the
fear of giving offense acted as a check on Hevelius and Riccioli,
authors of the first lunar maps (1647, 1651), and they judged it more
prudent to transfer the names of the terrestrial mountains to the Moon.
The Alps, the Apennines, the Pyrenees, the Carpathians, are all to be
found up there; then, as the vocabulary of the mountains was not
adequate, the scientists reasserted their rights, and we meet in the
Moon, Aristotle, Plato, Hipparchus, Ptolemy, Copernicus, Kepler, Newton,
as well as other more modern and even contemporaneous celebrities.
We have not space to reproduce the general chart of the Moon (that
published by the author measures not less than a meter, with the
nomenclature); but the figure subjoined gives a summary sufficient for
the limits of this little book. Here are the names of the principal
lunar mountains, with the numbers corresponding to them upon the map.
[Illustration: FIG. 71.--Map of the Moon.
(From Fowler's "Telescopic Astronomy.")
1 Furnerius
2 Petavius
3 Langrenus
4 Macrobius
5 Cleomedes
6 Endymion
7 Altas
8 Hercules
9 Romer
10 Posidonius
11 Fracastorius
12 Theophilus
13 Piccolomini
14 Albategnius
15 Hipparchus
16 Manilius
17 Eudoxus
18 Aristotle
19 Cassini
20 Aristillus
21 Plato
22 Archimedes
23 Eratosthenes
24 Copernicus
25 Ptolemy
26 Alphonsus
27 Arzachel
28 Walter
29 Clavius
30 Tycho
31 Bullialdus
32 Schiller
33 Schickard
34 Gassendi
35 Kepler
36 Grimaldi
37 Aristarchus
A Mare Crisum
B Mare Fercunditatis
C Mare Nectaris
D Mare Tranquilitatis
E Mare Serenitatis
F Mare Imbrium
G Sinus Iridum
H Oceanus Procellarum
I Mare Humorum
K Mare Nubium
V Altai Mountains
W Mare Vaporum
X Apennine Mountains
Y Caucasus Mountains
Z Alps]
The constantly growing progress of optics leads to perpetual new
discoveries in science, and at the present time we can say that we know
the geography of the Moon as well as, and even better than, that of our
own planet. The heights of all the mountains of the Moon are measured to
within a few feet. (One cannot say as much for the mountains of the
Earth.) The highest are over 7,000 meters (nearly 25,000 feet).
Relatively to its proportions, the satellite is much more mountainous
than the planet, and the plutonian giants are much more numerous there
than here. If we have peaks, like the Gaorisankar, the highest of the
Himalayas and of the whole Earth, whose elevation of 8,840 meters
(29,000 feet) is equivalent to 1/1140 the diameter of our globe, there
are peaks on the Moon of 7,700 meters (25,264 feet), _e.g._, those of
Doerfel and Leibniz, the height of which is equivalent to 1/470 the
lunar diameter.
Tycho's Mountain is one of the finest upon our satellite. It is visible
with the naked eye (and perfectly with opera-glasses) as a white point
shining like a kind of star upon the lower portion of the disk. At the
time of full moon it is dazzling, and projects long rays from afar upon
the lunar globe. So, too, Mount Copernicus, whose brilliant whiteness
sparkles in space. But the strangest thing about these lunar mountains
is that they are all hollow, and can be measured as well in depth as in
height. A type of mountain as strange to us as are the seas without
water! In effect, these mountains of the moon are ancient volcanic
craters, with no summits, nor covers.
At the top of the highest peaks, there is a large circular depression,
prolonged into the heart of the mountain, sometimes far below the level
of the surrounding plains, and as these craters often measure several
hundred kilometers, one is obliged, if one does not want to go all round
them in crossing the mountain, to descend almost perpendicularly into
the depths and cross there, to reascend the opposite side, and return to
the plain. These alpine excursions incontestably deserve the name of
perilous ascents!
No country on the Earth can give us any notion of the state of the lunar
soil: never was ground so tormented; never globe so profoundly shattered
to its very bowels. The mountains are accumulations of enormous rocks
tumbled one upon the other, and round the awful labyrinth of craters one
sees nothing but dismantled ramparts, or columns of pointed rocks like
cathedral spires issuing from the chaos.
As we said, there is no atmosphere, or at least so little at the bottom
of the valleys that it is imperceptible. No clouds, no fog, no rain nor
snow. The sky is an eternally black space, vaultless, jeweled with stars
by day as by night.
Let us suppose that we arrive among these savage steppes at daybreak:
the lunar day is fifteen times longer than our own, because the Sun
takes a month to illuminate the entire circuit of the Moon; there are no
less than 354 hours from the rising to the setting of the Sun. If we
arrive before the sunrise, there is no aurora to herald it, for in the
absence of atmosphere there can be no sort of twilight. Of a sudden on
the dark horizon come flashes of the solar light, striking the summits
of the mountains, while the plains and valleys are still in darkness.
The light spreads slowly, for while on the Earth in central latitudes
the Sun takes only two minutes and a quarter to rise, on the Moon it
takes nearly an hour, and in consequence the light it sends out is very
weak for some minutes, and increases excessively slowly. It is a kind of
aurora, but lasts a very short time, for when at the end of half an
hour, the solar disk has half risen, the light appears as intense to the
eye as when it is entirely above the horizon; the radiant orb is seen
with its protuberances and its burning atmosphere. It rises slowly, like
a luminous god, in the depths of the black sky, a profound and formless
sky in which the stars shine all day, since they are not hidden by any
atmospheric veil such as conceals them from us during the daylight.
[Illustration: FIG. 72.--The Lunar Apennines.]
The absence of sensible atmosphere must produce an effect on the
temperature of the Moon analogous to that perceived on the high
mountains of our globe, where the rarefaction of the air does not permit
the solar heat to concentrate itself upon the surface of the soil, as it
does below the atmosphere, which acts as a forcing-house: the Sun's heat
is not kept in by anything, and incessantly radiates out toward space.
In all probability the cold is extremely and constantly rigorous, not
only during the nights, which are fifteen times longer than our own, but
even during the long days of sunshine.
We give two different drawings to represent these curious aspects of
lunar topography. The first (Fig. 72) is taken in the neighborhood of
the Apennines, and shows a long chain of mountains beneath which are
three deep rings, Archimedes, Aristillus, and Autolycus: the second
(Fig. 73) depicts the lunar ring of Flammarion,[14] whose outline is
constructed of dismantled ramparts, and whose depths are sprinkled with
little craters. The first of these two drawings was made in England by
Nasmyth, the second in Germany by Krieger: they both give an exact idea
of what one sees in the telescope with different modes of solar
illumination.
In the Moon's always black and starry sky a majestic star that is not
visible from the Earth, and exhibits this peculiarity that it is
stationary in the Heavens, while all the others pass behind it, may
constantly be admired, by day as well as by night; and it is also of
considerable apparent magnitude. This orb, some four times as large as
the Moon in diameter, and thirteen to fourteen times more extensive in
surface, is our Earth, which presents to the Moon a sequence of phases
similar to those which our satellite presents to us, but in the inverse
direction. At the moment of New Moon, the Sun fully illuminates the
terrestrial hemisphere turned toward our satellite, and we get "Full
Earth"; at the time of Full Moon, on the contrary, the non-illuminated
hemisphere of the Earth is turned toward the satellite, and we get "New
Earth": when the Moon shows us first quarter, the Earth is in last
quarter, and so on. The drawing subjoined gives an idea of these
aspects.
[Illustration: FIG. 73.--Flammarion's Lunar Ring.]
What a curious sight our globe must be during this long night of
fourteen times twenty-four hours! Independent of its phases, which bring
it from first quarter to full earth for the middle of the night, and
from full earth to last quarter for sunrise, how interested we should be
to see it thus stationary in the sky, and turning on itself in
twenty-four hours.
[Illustration: FIG. 74.--Lunar landscape with the Earth in the sky.]
Yes, thanks to us, the inhabitants of the lunar hemisphere turned toward
us are gratified by the sight of a splendid nocturnal torch, doubtless
less white than our own despite the clouds with which the terrestrial
globe is studded, and shaded in a tender tone of bluish emerald-green.
The royal orb of their long nights, the Earth, gives them moonlight of
unparalleled beauty, and we may say without false modesty that our
presence in the lunar sky must produce marvelous and absolutely
fairy-like effects.
Maybe, they envy us our globe, a dazzling dwelling-place whose splendor
radiates through space; they see its greenish clarity varying with the
extent of cloud that veils its seas and continents, and they observe its
motion of rotation, by which all the countries of our planet are
revealed in succession to its admirers.
We are talking of these pageants seen from the Moon, and of the
inhabitants of our satellite as if they really existed. The sterile and
desolate aspect of the lunar world, however, rather brings us to the
conclusion that such inhabitants are non-existent, although we have no
authorization for affirming this. That they have existed seems to me
beyond doubt. The lunar volcanoes had a considerable activity, in an
atmosphere that allowed the white volcanic ashes to be carried a long
way by the winds, figuring round the craters the stellar rays that are
still so striking. These cinders were spread over the soil, preserving
all its asperities of outline, a little heaped up on the side to which
they were impelled. The magnificent photographs recently made at the
Paris Observatory by MM. Loewy and Puiseux are splendid evidence of
these projections. In this era of planetary activity there were liquids
and gases on the surface of the lunar globe, which appear subsequently
to have been entirely absorbed. Now the teaching of our own planet is
that Nature nowhere remains infertile, and that the production of Life
is a law so general and so imperious that life develops at its own
expense, sooner than abstain from developing. Accordingly, it is
difficult to suppose that the lunar elements can have remained inactive,
when only next door they exhibited such fecundity upon our globe. Yes,
the Moon has been inhabited by beings doubtless very different from
ourselves, and perhaps may still be, although this globe has run through
the phases of its astral life more rapidly than our own, and the
daughter is relatively older than the mother.
The duration of the life of the worlds appears to have been in
proportion with their masses. The Moon cooled and mineralized more
quickly than the Earth. Jupiter is still fluid.
The progress of optics brings us already very close to this neighboring
province. 'Tis a pity we can not get a little nearer!
A telescopic magnification of 2,000 puts the Moon at 384,000/2000 or 192
kilometers (some 120 miles) from our eye. Practically we can obtain no
more, either from the most powerful instruments, or from photographic
enlargements. Sometimes, exceptionally, enlargements of 3,000 can be
used. This = 384000/3000 or 128 kilometers (some 80 miles). Undoubtedly,
this is an admirable result, which does the greatest honor to human
intelligence. But it is still too far to enable us to determine anything
in regard to lunar life.
Any one who likes to be impressed by grand and magnificent sights may
turn even a modest field-glass upon our luminous satellite, at about
first quarter, when the relief of its surface, illuminated obliquely by
the Sun, is at its greatest value. If you examine our neighbor world at
this period, for choice at the hour of sunset, you will be astonished at
its brilliancy and beauty. Its outlines, its laces, and embroideries,
give the image of a jewel of shining silver, translucent, fluid,
palpitating in the ether. Nothing could be more beautiful, nothing
purer, and more celestial, than this lunar globe floating in the silence
of space, and sending back to us as in some fairy dream the solar
illumination that floods it. But yesterday I received the same
impression, watching a great ring half standing out, and following the
progress of the Sun as it mounted the lunar horizon to touch these
silvered peaks. And I reflected that it is indeed inconceivable that
999,999/1,000,000 of the inhabitants of our planet should pass their
lives without ever having attended to this pageant, nor to any of those
others which the divine Urania scatters so profusely beneath the
wondering gaze of the observers of the Heavens.
CHAPTER X
THE ECLIPSES
Among all the celestial phenomena at which it may be our lot to assist
during our contemplation of the universe, one of the most magnificent
and imposing is undoubtedly that which we are now going to consider.
The hirsute comets, and shooting stars with their graceful flight,
captivate us with a mysterious and sometimes fantastic attraction. We
gladly allow our thoughts, mute questioners of the mysteries of the
firmament, to rest upon the brilliant, golden trail they leave behind
them. These unknown travelers bring a message from eternity; they tell
us the tale of their distant journeys. Children of space, their ethereal
beauty speaks of the immensity of the universe.
The eclipses, on the other hand, are phenomena that touch us more
nearly, and take place in our vicinity.
In treating of them, we remain between the Earth and the Moon, in our
little province, and witness the picturesque effects of the combined
movements of our satellite around us.
Have you ever seen a total eclipse of the Sun?
The sky is absolutely clear: no fraction of cloud shadows the solar
rays. The azure vault of the firmament crowns the Earth with a dome of
dazzling light. The fires of the orb of day shed their beneficent
influence generally upon the world.
Yet, see! The radiance diminishes. The luminous disk of the Sun is
gradually corroded. Another disk, as black as ink, creeps in front of
it, and little by little invades it entirely. The atmosphere takes on a
wan, sepulchral hue; astonished nature is hushed in profound silence; an
immense veil of sadness spreads over the world. Night comes on suddenly,
and the stars shine out in the Heavens. It seems as though by some
mysterious cataclysm the Sun had disappeared forever. But this
tribulation is soon over. The divine orb is not extinct. A flaming jet
emerges from the shadow, announcing his return, and when he reappears we
see that he has lost nothing in splendor or beauty. He is still the
radiant Apollo, King of Day, watching over the life of the planetary
worlds.
This sudden night, darkening the Heavens in the midst of a fine day, can
not fail to produce a vivid impression upon the spectators of the superb
phenomenon.
The eclipse lasts only for a few moments, but long enough to make a deep
impression upon our minds, and indeed to inspire anxious spirits with
terror and agitation--even at this epoch, when we know that there is
nothing supernatural or formidable about it.
In former days, Humanity would have trembled, in uneasy consternation.
Was it a judgment from Heaven? Must it not be the work of some invisible
hand throwing the somber veil of night over the celestial torch?
Had not the Earth strayed off her appointed path, and were we not all to
be deprived eternally of the light of our good Sun? Was some monstrous
dragon perhaps preparing to devour the orb of day?
The fable of the dragon devouring the Sun or Moon during the eclipses is
universal in Asia as in Africa, and still finds acceptance under more
than one latitude. But our readers already know that we may identify the
terrible celestial dragon with our gentle friend the Moon, who would not
be greatly flattered by the comparison.
We saw in the preceding lesson that the Moon revolves round us,
describing an almost circular orbit that she travels over in about a
month. In consequence of this motion, the nocturnal orb is sometimes
between the Sun and the Earth, sometimes behind us, sometimes at a right
angle in relation to the Sun and the Earth. Now, the eclipses of the Sun
occur invariably at the time of New Moon, when our satellite passes
between the Sun and ourselves, and the eclipses of the Moon, at the
moment of Full Moon, when the latter is opposite to the Sun, and behind
us.
This fact soon enabled the astronomers of antiquity to discover the
causes to which eclipses are due.
The Moon, passing at the beginning of its revolution between the Sun and
the Earth, may conceal a greater or lesser portion of the orb of day. In
this case there is an eclipse of the Sun. On the other hand, when it is
on the other side of the Earth in relation to the Sun, at the moment of
Full Moon, our planet may intercept the solar rays, and prevent them
from reaching our satellite. The Moon is plunged into _the shadow of the
Earth_, and is then eclipsed. Such is the very simple explanation of the
phenomenon. But why is there not an eclipse of the Sun at each New Moon,
and an eclipse of the Moon at each Full Moon?
If the Moon revolved round us in the same plane as the Earth round the
Sun, it would eclipse the Sun at each New Moon, and would be itself
eclipsed in our shadow at each Full Moon. But the plane of the lunar
orbit dips a little upon the plane of the terrestrial orbit, and the
eclipses can only be produced when the New Moon or the Full Moon occur
at the line of intersection of these two planes, _i.e._, when the Sun,
the Moon, and the Earth are upon the same straight line. In the majority
of cases, instead of interposing itself directly in front of the
sovereign of our system, our satellite passes a little above or a little
below him, just as its passage behind us is nearly always effected a
little above or below the cone of shadow that accompanies our planet,
opposite the Sun.
When the Moon intervenes directly in front of the Sun, she arrests the
light of the radiant orb, and conceals a greater or less portion of the
solar disk. The eclipse is partial if the Moon covers only a portion of
the Sun; total if she covers it entirely; annular, if the solar disk is
visible all round the lunar disk, as appears when the Moon, in her
elliptical orbit, is beyond medium distance, toward the apogee.
On the other hand, when the Moon arrives immediately within the cone of
shadow that the Earth projects behind it, it is her turn to be eclipsed.
She no longer receives the rays of the Sun, and this deprivation is the
more marked in that she owes all her brilliancy to the light of the orb
of day. The Moon's obscurity is complete if she is entirely plunged into
the cone of shadow. In this case, the eclipse is total. But if a portion
of her disk emerges from the cone, that part remains illuminated while
the light of the other dies out. In that case there is a partial
eclipse, and the rounded form of the Earth's shadow can be seen
projected upon our satellite, a celestial witness to the spherical
nature of our globe.
Under certain conditions, then, the Moon can deprive us of the luminous
rays of the Sun, by concealing the orb of day, and in other cases is
herself effaced in crossing our shadow. Despite the fables, fears, and
anxieties it has engendered, this phenomenon is perfectly natural: the
Moon is only playing hide-and-seek with us--a very harmless amusement,
as regards the safety of our planet.
But as we said just now, these phenomena formerly had the power of
terrifying ignorant mortals, either when the orb of light and life
seemed on the verge of extinction, or when the beautiful Phoebus was
covered with a veil of crape and woe, or took on a deep coppery hue.
It would take a volume to describe all the notable events which have
been influenced by eclipses, sometimes for good, more often with
disastrous consequences. The recital of these tragic stories would not
be devoid of interest; it would illustrate the possibilities of
ignorance and superstition, and the power man gains from intellectual
culture and scientific study.
Herodotus records that the Scythians, having some grievance against
Cyaxarus, King of the Medes, revenged themselves by serving up the limbs
of one of his children, whom they had murdered, at a banquet as rare
game. The scoundrels who committed this atrocious crime took refuge at
the Court of the King of Lydia, who was ill judged enough to protect
them. War was accordingly declared between the Medes and Lydians, but a
total eclipse of the Sun occurring just when the battle was imminent,
had the happy effect of disarming the combatants, who prudently retired
each to their own country. This eclipse, which seems to have occurred on
May 28, 584 B.C., had been predicted by Thales. The French painter
Rochegrosse has painted a striking picture of the scene (Fig. 75).
In the year 413 B.C. the Athenian General Nicias prepared to return to
Greece after an expedition to Sicily. But, terrified by an eclipse of
the Moon, and fearing the malign influence of the phenomenon, he put off
his departure, and lost the chance of retreat. This superstition cost
him his life. The Greek army was destroyed, and this event marks the
commencement of the decadence of Athens.
In 331 B.C. an eclipse of the Moon disorganized the troops of Alexander,
near Arbela, and the great Macedonian Captain had need of all his
address to reassure his panic-stricken soldiers.
Agathocles, King of Syracuse, blocked by the Carthaginians in the port
of this city, had the good fortune to escape, but was disturbed on the
second day of his flight by the arrival of a total eclipse of the Sun
which alarmed his companions. "What are you afraid of?" said he,
spreading his cloak in front of the Sun. "Are you alarmed at a shadow?"
(This eclipse seems to be that of August 15, 309, rather than that of
March 2, 310.)
[Illustration: FIG. 75.--Battle between the Medes and Lydians arrested
by an Eclipse of the Sun.]
On June 29, 1033, an epoch at which the approaching end of the world
struck terror into all hearts, an annular eclipse of the Sun occurring
about midday frustrated the designs of a band of conspirators who
intended to strangle the Pope at the altar. This Pope was Benedict IX, a
youth of less than twenty, whose conduct is said to have been anything
but exemplary. The assassins, terrified at the darkening of the Sun,
dared not touch the Pontiff, and he reigned till 1044.[15]
On March 1, 1504, a lunar eclipse saved the life of Christopher
Columbus. He was threatened with death by starvation in Jamaica, where
the contumacious savages refused to give him provisions. Forewarned of
the arrival of this eclipse by the astronomical almanacs, he threatened
to deprive the Caribs of the light of the Moon--and kept his word. The
eclipse had hardly begun when the terrified Indians flung themselves at
his feet, and brought him all that he required.
In all times and among all people we find traces of popular
superstitions connected with eclipses. Here, the abnormal absence of the
Moon's light is regarded as a sign of divine anger: the humble penitents
betake themselves to prayer to ward off the divine anger. There, the
cruelty of the dread dragon is to be averted: he must be chased away by
cries and threats, and the sky is bombarded with shots to deliver the
victim from his monstrous oppressor.
In France the announcement of a solar eclipse for August 21, 1560, so
greatly disturbed our ancestors' peace of mind as to make them idiotic.
Preparations were made for assisting at an alarming phenomenon that
threatened Humanity with deadly consequences! The unhappy eclipse had
been preceded by a multitude of ill omens! Some expected a great
revolution in the provinces and in Rome, others predicted a new
universal deluge, or, on the other hand, the conflagration of the world;
the most optimistic thought the air would be contaminated. To preserve
themselves from so many dangers, and in accordance with the physicians'
orders, numbers of frightened people shut themselves up in tightly
closed and perfumed cellars, where they awaited the decrees of Fate. The
approach of the phenomenon increased the panic, and it is said that one
village _curé_, being unable to hear the confessions of all his flock,
who wanted to discharge their souls of sin before taking flight for a
better world, was fain to tell them "there was no hurry, because the
eclipse had been put off a fortnight on account of the number of
penitents"!
[Illustration: FIG. 76.--Eclipse of the Moon at Laos (February 27,
1877).]
These fears and terrors are still extant among ignorant peoples. In the
night of February 27, 1877, an eclipse of the Moon produced an
indescribable panic among the inhabitants of Laos (Indo-China). In order
to frighten off the Black Dragon, the natives fired shots at the
half-devoured orb, accompanying their volley with the most appalling
yells. Dr. Harmand has memorialized the scene in the lively sketch given
on p. 269.
During the solar eclipse of March 15, 1877, an analogous scene occurred
among the Turks, who for the moment forgot their preparations for war
with Russia, in order to shoot at the Sun, and deliver him from the
toils of the Dragon.
The lunar eclipse of December 16, 1880, was not unnoticed at Tackhent
(Russian Turkestan), where it was received with a terrific din of
saucepans, samovars and various implements struck together again and
again by willing hands that sought to deliver the Moon from the demon
Tchaitan who was devouring her.
In China, eclipses are the object of imposing ceremonies, whose object
is to reestablish the regularity of the celestial motions. Since the
Emperor is regarded as the Son of Heaven, his government must in some
sort be a reflection of the immutable order of the sidereal harmonies.
As eclipses were regarded by astrologers as disturbances of the divine
order, their appearance indicates some irregularity in the government of
the Celestial Empire. Accordingly, they are received with all kinds of
expiatory ceremonies prescribed thousands of years ago, and still in
force to-day.
In the twentieth century, as in the nineteenth, the eighteenth, or in
ancient epochs, the same awe and terror operates upon the ignorant
populations who abound upon the surface of our planet.
To return to astronomical realities.
We said above that these phenomena were produced when the Full Moon and
the New Moon reached the line of intersection, known as the line of
nodes, when the plane of the lunar orbit cuts the plane of the ecliptic.
As this line turns and comes back in the same direction relatively to
the Sun at the end of eighteen years, eleven days, we have only to
register the eclipses observed during this period in order to know all
that will occur in the future, and to find such as happened in the past.
This period was known to the Greeks under the name of the Metonic Cycle,
and the Chaldeans employed it three thousand years ago under the name of
Saros.
On examining this cycle, composed of 223 lunations, we see that there
can not be more than seven eclipses in one year, nor less than two. When
there are only two, they are eclipses of the Sun.
The totality of a solar eclipse can not last more than seven minutes,
fifty-eight seconds at the equator, and six minutes, ten seconds in the
latitude of Paris. The Moon, on the contrary, may be entirely eclipsed
for nearly two hours.
Eclipses of the Sun are very rare for a definite spot. Thus not one
occurred for Paris during the whole of the nineteenth century, the last
which happened exactly above the capital of France having been on May
22, 1724. I have calculated all those for the twentieth century, and
find that two will take place close to Paris, on April 17, 1912, at
eighteen minutes past noon (total for Choisy-le-Roi, Longjumeau, and
Dourdan, but very brief: seven seconds), and August 11, 1999, at 10.28
A.M. (total for Beauvais, Compiègne, Amiens, St. Quentin, fairly long:
two minutes, seventeen seconds). Paris itself will not be favored before
August 12, 2026. In order to witness the phenomenon, one must go and
look for it. This the author did on May 28, 1900, in Spain.
The progress of the lunar shadow upon the surface of the Earth is traced
beforehand on maps that serve to show the favored countries for which
our satellite will dispense her ephemeral night. The above figure shows
the trajectory of the total phase of the 1900 eclipse in Portugal,
Spain, Algeria, and Tunis.
[Illustration: FIG. 77.--The path of the Eclipse of May 28, 1900.]
The immutable splendor of the celestial motions had never struck the
author so impressively as during the observation of this grandiose
phenomenon. With the absolute precision of astronomical calculations,
our satellite, gravitating round the Earth, arrived upon the theoretical
line drawn from the orb of day to our planet, and interposed itself
gradually, slowly, and exactly, in front of it. The eclipse was total,
and occurred at the moment predicted by calculation. Then the obscure
globe of the Moon pursued its regular course, discovered the radiant orb
behind, and gradually and slowly completed its transit in front of him.
Here, to all observers, was a double philosophical lesson, a twofold
impression: that of the greatness, the omnipotence of the inexorable
forces that govern the universe, and that of the inexorable valor of
man, of this thinking atom straying upon another atom, who by the
travail of his feeble intelligence has arrived at the knowledge of the
laws by which he, like the rest of the world, is borne away through
space, through time, and through eternity.
The line of centrality passed through Elche, a picturesque city of
30,000 inhabitants, not far from Alicante, and we had chosen this for
our station on account of the probability of fine weather.
From the terrace of the country house of the hospitable Mayor, a farm
transformed into an observatory by our learned friend, Count de la Baume
Pluvinel, there were no obstacles between ourselves and any part of the
sky or landscape. The whole horizon lay before us. In front was a town
of Arab aspect framed in a lovely oasis of palm-trees; a little farther
off, the blue sea beyond the shores of Alicante and Murcia: on the
other side a belt of low mountains, and near us fields and gardens. A
Company of the Civic Guard kept order, and prevented the entrance of too
many curious visitors, of whom over ten thousand had arrived.
At the moment when the first contact of the lunar disk with the solar
disk was observed in the telescope, we fired a gun, in order to announce
the precise commencement of the occultation to the 40,000 persons who
were awaiting the phenomenon, and to discover what difference would
exist between this telescopic observation and those made with the
unaided eyes (protected simply by a bit of smoked glass) of so many
improvised spectators. This had already been done by Arago at Perpignan
in 1842. The verification was almost immediate for the majority of eyes,
and may be estimated at eight or ten seconds. So that the commencement
of the eclipse was confirmed almost as promptly for the eye as with the
astronomical instruments.
The sky was splendidly clear; no cloud, no mist, deep blue; blazing Sun.
The first period of the eclipse showed nothing particular. It is only
from the moment when more than half the solar disk is covered by the
lunar disk that the phenomenon is imposing in its grandeur. At this
phase, I called the attention of the people standing in the court to the
visibility of the stars, and indicating the place of Venus in the sky
asked if any with long sight could perceive her. Eight at once
responded in the affirmative. It should be said that the planet was at
that time at its period of maximum brilliancy, when for observers
blessed with good sight, it is always visible to the unaided eye.
When some three-quarters of the Sun were eclipsed, the pigeons which had
flown back to the farm huddled into a corner, and made no further
movement. They told me that evening that the fowls had done the same a
little later, returning to the hen-house as though it had been night,
and that the small children (who were very numerous at Elche, where the
population is certainly not diminishing) left off their games, and came
back to their mothers' skirts. The birds flew anxiously to their nests.
The ants in one garden were excessively agitated, no doubt disconcerted
in their strategics. The bats came out.
A few days before the eclipse I had prepared the inhabitants of this
part of Spain for the observation of the phenomenon by the following
description, which sums up the previous accounts of the astronomers:
"The spectacle of a total eclipse of the Sun is one of the most
magnificent and imposing that it is possible to see in nature. At the
exact moment indicated by calculation, the Moon arrives in front of the
Sun, eats into it gradually, and at last entirely covers it. The light
of the day lessens and is transformed. A sense of oppression is felt by
all nature, the birds are hushed, the dog takes refuge with his master,
the chickens hide beneath their mother's wing, the wind drops, the
temperature falls, an appalling stillness is everywhere perceptible, as
though the universe were on the verge of some imminent catastrophe.
Men's faces assume a cadaverous hue similar to that given at night by
the flame of spirits of wine and salt, a livid funereal light, the
sinister illumination of the world's last hour.
"At the moment when the last line of the solar crescent disappears, we
see, instead of the Sun, a black disk surrounded with a splendid
luminous aureole shooting immense jets into space, with roseate flames
burning at the base.
"A sudden night has fallen on us, a weird, wan night in which the
brightest of the stars are visible in the Heavens. The spectacle is
splendid, grandiose, solemn, and sublime."
This impression was actually felt by us all, as may be seen from the
following notes, written in my schedule of observation during the event,
or immediately after:
"3.50 P.M. Light very weak, sky leaden gray, mountains standing out with
remarkable clearness from the horizon, and seeming to approach us.
"3.55 P.M. Fall of temperature very apparent. Cold wind blowing through
the atmosphere.
"3.56 P.M. Profound silence through nature, which seems to participate
in the celestial phenomenon. Silence in all the groups.
"3.57 P.M. Light considerably diminished, becoming wan, strange, and
sinister. Landscape leaden gray, sea looks black. This diminution of
light is not that of every day after the sunset. There is, as it were, a
tint of sadness spread over the whole of nature. One becomes accustomed
to it, and yet while we know that the occultation of the Sun by the Moon
is a natural phenomenon, we can not escape a certain sense of
uneasiness. The approach of some extraordinary spectacle is imminent."
At this point we examined the effects of the solar light upon the seven
colors of the spectrum. In order to determine as accurately as possible
the tonality of the light of the eclipse, I had prepared seven great
sheets, each painted boldly in the colors of the spectrum, violet,
indigo, blue, green, yellow, orange, red; and a similar series in pieces
of silk. These colors were laid at our feet upon the terrace where my
wife, as well as Countess de la Baume, were watching with me. We then
saw the first four disappear successively and entirely and turn black in
a few seconds, in the following order: violet, indigo, blue, green. The
three other colors were considerably attenuated by the darkness, but
remained visible.
It should be noted that in the normal order of things--that is, every
evening--the contrary appears; violet remains visible after the red.
This experiment shows that the last light emitted by the eclipsed Sun
belongs to the least refrangible rays, to the greatest wave-lengths, to
the slowest vibrations, to the yellow and red rays. Such therefore is
the predominating color of the solar atmosphere.
This experiment completed, we turn back to the Sun. Magical and splendid
spectacle! Totality has commenced, the Sun has disappeared, the black
disk of the Moon covers it entirely, leaving all round it a magnificent
corona of dazzling light. One would suppose it to be an annular eclipse,
with the difference that this can be observed with the naked eye,
without fatigue to the retina, and drawn quietly.
This luminous coronal atmosphere entirely surrounds the solar disk, at a
pretty equal depth, equivalent to about the third of half the solar
diameter. It may be regarded as the Sun's atmosphere.
Beyond this corona is an aureole, of vaster glory but less luminous,
which sends out long plumes, principally in the direction of the
equatorial zone of the Sun, and of the belt of activity of the spots and
prominences.
At the summit of the disk it is conical in shape. Below it is double,
and its right-hand portion ends in a point, not far from Mercury, which
shines like a dazzling star of first magnitude, and seems placed there
expressly to give us the extent and direction of the solar aureole.
I draw these various aspects (which, moreover, change with the movement
of the Moon), and what strikes me most is the distinction in light
between this aureole and the coronal atmosphere; the latter appears to
be a brilliant silvery white, the former is grayer and certainly less
dense.
My impression is that there are _two solar envelopes of entirely
different nature_, the corona belonging to the globe of the Sun, and
forming its atmosphere properly so-called, very luminous; the aureole
formed of particles that circulate independently round it, probably
arising from eruptions, their form as a whole being possibly due to
electric or magnetic forces, counterbalanced by resistances of various
natures. In our own atmosphere the volcanic eruptions are distinct from
the aerial envelope.
The general configuration of this external halo, spreading more
particularly in the equatorial zone, is sufficiently like that of the
eclipse of 1889, published in my _Popular Astronomy_, which also
corresponded with a minimum of solar energy. The year 1900 is in fact
close upon the minimum of the eleven-year period. This equatorial form
is, moreover, what all the astronomers were expecting.
[Illustration: FIG. 78.--Total eclipse of the Sun, May 28, 1900, as
observed from Elche (Spain).]
There can no longer be the slightest doubt that the solar envelope
varies with the activity of the Sun....
"But the total eclipse lasted a much shorter time than I have taken to
write these lines. The seventy-nine seconds of totality are over. A
dazzling light bursts from the Sun, and tells that the Moon pursuing its
orbit has left it. The splendid sight is over. It has gone like a
shadow.
"Already over! It is almost a disillusion. Nothing beautiful lasts in
this world. Too sad! If only the celestial spectacle could have lasted
two, three, or four minutes! It was too short....
"Alas! we are forced to take things as they are.
"The surprise, the oppression, the terror of some, the universal silence
are over. The Sun reappears in his splendor, and the life of nature
resumes its momentarily suspended course.
"While I was making my drawing, M. l'Abbé Moreux, my colleague from the
Astronomical Society of France, who accompanied me to Spain for this
observation, was taking one of his own, without any reciprocal
communication. These two sketches are alike, and confirmatory.
"The differential thermometers that I exposed to the Sun, hanging
freely, and protected from reflection from the ground, were read every
five minutes. The black thermometer went down from 33.1° to 20.7°, that
is 12.4°; the white from 29° to 20.2°--that is, 8.8°. The temperature in
the shade only varied three degrees.
"The light received during totality was due: first, to the luminous
envelope of the Sun; second, to that of the terrestrial atmosphere,
illuminated at forty kilometers (twenty-five miles) on the one side and
the other of the line of centrality. It appeared to be inferior to that
of the Full Moon, on account of the almost sudden transition. But, in
reality, it was more intense, for only first-magnitude stars were
visible in the sky, whereas on a night of full moon, stars of second,
and even of third magnitude are visible. We recognized, among others,
Venus, Mercury, Sirius, Procyon, Capella, Rigel, Betelgeuse."
* * * * *
From these notes, taken on the spot, it is evident that the
contemplation of a total eclipse of the Sun is one of the most marvelous
spectacles that can be admired upon our planet.
Some persons assured me that they saw the shadow of the Moon flying
rapidly over the landscape. My attention was otherwise occupied, and I
was unable to verify this interesting observation. The shadow of the
Moon in effect took only eleven minutes (3.47 P.M. to 3.58 P.M.) to
traverse the Iberian Peninsula from Porto to Alicante, _i.e._, a
distance of 766 kilometers (475 miles). It must therefore have passed
over the ground at a velocity of sixty-nine kilometers per minute, or
1,150 meters per second, a speed higher than that of a bullet. It can
easily be watched from afar, on the mountains.
Some weeks previous to this fine eclipse, when I informed the Spaniards
of the belt along which it could be observed, I had invited them to note
all the interesting phenomena they might witness, including the effects
produced by the eclipse upon animals. Birds returned hurriedly to their
nests, swallows lost themselves, sheep huddled into compact packs,
partridges were hypnotized, frogs croaked as if it were night, fowls
took refuge in the hen-house, and cocks crowed, bats came out, and were
surprised by the sun, chicks gathered under their mothers' wing,
cage-birds ceased their songs, some dogs howled, others crept shivering
to their masters' feet, ants returned to the antheap, grasshoppers
chirped as at sunset, pigeons sank to the ground, a swarm of bees went
silently back to their hive, and so on.
These creatures behaved as though the night had come, but there were
also signs of fear, surprise, even of terror, differing only "in degree"
from those manifested during the grandiose phenomenon of a total
eclipse by human beings unenlightened by a scientific education.
At Madrid the eclipse was only partial. The young King of Spain, Alfonso
XIII, took care to photograph it, and I offer the photograph to my
readers (Fig. 79), as this amiable sovereign did me the honor to give it
me a few days after the eclipse.
[Illustration: FIG. 79.--The Eclipse of May 28, 1900, as photographed by
King Alfonso XIII, at Madrid.]
The technical results of these observations of solar eclipses relate
more especially to the elucidation of the grand problem of the physical
constitution of the Sun. We alluded to them in the chapter devoted to
this orb. The last great total eclipses have been of immense value to
science.
The eclipses of the Moon are less important, less interesting, than the
eclipses of the Sun. Yet their aspect must not be neglected on this
account, and it may be said to vary for each eclipse.
Generally speaking, our satellite does not disappear entirely in the
Earth's cone of shadow; the solar rays are refracted round our globe by
our atmosphere, and curving inward, illumine the lunar globe with a rosy
tint that reminds one of the sunset. Sometimes, indeed, this refraction
does not occur, owing doubtless to lack of transparency in the
atmosphere, and the Moon becomes invisible. This happened recently, on
April 11, 1903.
For any spot, eclipses of the Moon are incomparably more frequent than
eclipses of the Sun, because the cone of lunar shadow that produces the
solar eclipses is not very broad at its contact with the surface of the
globe (10, 20, 30, 50, 100 kilometers, according to the distance of the
Moon), whereas all the countries of the Earth for which the Moon is
above the horizon at the hour of the lunar eclipse are able to see it.
It is at all times a remarkable spectacle that uplifts our thoughts to
the Heavens, and I strongly advise my readers on no account to forego
it.
CHAPTER XI
ON METHODS
HOW CELESTIAL DISTANCES ARE DETERMINED, AND HOW THE SUN IS WEIGHED
I will not do my readers the injustice to suppose that they will be
alarmed at the title of this Lesson, and that they do not employ some
"method" in their own lives. I even assume that if they have been good
enough to take me on faith when I have spoken of the distances of the
Sun and Moon, and Stars, or of the weight of bodies at the surface of
Mars, they retain some curiosity as to how the astronomers solve these
problems. Hence it will be as interesting as it is useful to complete
the preceding statements by a brief summary of the methods employed for
acquiring these bold conclusions.
The Sun seems to touch the Earth when it disappears in the purple mists
of twilight: an immense abyss separates us from it. The stars go hand in
hand down the constellated sky; and yet one can not think of their
inconceivable distance without a shiver.
Our neighbor, Moon, floats in space, a stone's throw from us: but
without calculation we should never know the distance, which remains an
impassable desert to us.
The best educated persons sometimes find it difficult to admit that
these distances of Sun and Moon are better determined and more precise
than those of certain points on our minute planet. Hence, it is of
particular moment for us to give an exact account of the means employed
in determining them.
The calculation of these distances is made by "_triangulation_." This
process is the same that surveyors use in the measurement of terrestrial
distances. There is nothing very alarming about it. If the word repels
us a little at first, it is from its appearance only.
When the distance of an object is unknown, the only means of expressing
its apparent size is by measurement of the angle which it subtends
before our eyes.
We all know that an object appears smaller, in proposition with its
distance from us. This diminution is not a matter of chance. It is
geometric, and proportional to the distance. Every object removed to a
distance of 57 times its diameter measures an angle of 1 degree,
whatever its real dimensions. Thus a sphere 1 meter in diameter measures
exactly 1 degree, if we see it at a distance of 57 meters. A statue
measuring 1.80 meters (about 5 ft. 8 in.) will be equal to an angle of 1
degree, if distant 57 times its height, that is to say, at 102.60
meters. A sheet of paper, size 1 decimeter, seen at 5.70 meters,
represents the same magnitude.
In length, a degree is the 57th part of the radius of a circle, _i.e._,
from the circumference to the center.
The measurement of an angle is expressed in parts of the circumference.
Now, what is an angle of a degree? It is the 360th part of any
circumference. On a table 3.60 meters round, an angle of one degree is a
centimeter, seen from the center of the table. Trace on a sheet of paper
a circle 0.360 meters round--an angle of 1 degree is a millimeter.
[Illustration: FIG. 80.--Measurement of Angles.]
If the circumference of a circus measuring 180 meters be divided into
360 places, each measuring 0.50 meters in width, then when the circus is
full a person placed at the center will see each spectator occupying an
angle of 1 degree. The angle does not alter with the distance, and
whether it be measured at 1 meter, 10 meters, 100 kilometers, or in the
infinite spaces of Heaven, it is always the same angle. Whether a degree
be represented by a meter or a kilometer, it always remains a degree. As
angles measuring less than a degree often have to be calculated, this
angle has been subdivided into 60 parts, to which the name of _minutes_
has been given, and each minute into 60 parts or _seconds_. Written
short, the degree is indicated by a little zero (°) placed above the
figure; the minute by an apostrophe ('), and the second by two (").
These minutes and seconds of _arc_ have no relation with the same terms
as employed for the division of the duration of time. These latter ought
never to be written with the signs of abbreviation just indicated,
though journalists nowadays set a somewhat pedantic example, by writing,
_e.g._, for an automobile race, 4h. 18' 30", instead of 4h. 18m. 30s.
This makes clear the distinction between the relative measure of an
angle and the absolute measures, such, for instance, as the meter. Thus,
a degree may be measured on this page, while a second (the 3,600th part
of a degree) measured in the sky may correspond to millions of
kilometers.
Now the measure of the Moon's diameter gives us an angle of a little
more than half a degree. If it were exactly half a degree, we should
know by that that it was 114 times the breadth of its disk away from us.
But it is a little less, since we have more than half a degree (31'),
and the geometric ratio tells us that the distance of our satellite is
110 times its diameter.
Hence we have very simply obtained a first idea of the distance of the
Moon by the measure of its diameter. Nothing could be simpler than this
method. The first step is made. Let us continue.
This approximation tells us nothing as yet of the real distance of the
orb of night. In order to know this distance in miles, we need to know
the width in miles of the lunar disk.
[Illustration: FIG. 81.--Division of the Circumference into 360
degrees.]
This problem has been solved, as follows:
Two observers go as far as possible from each other, and observe the
Moon simultaneously, from two stations situated on the same meridian,
but having a wide difference of latitude. The distance that separates
the two points of observation forms the base of a triangle, of which the
two long sides come together on the Moon.
[Illustration: FIG. 82.--Measurement of the distance of the Moon.]
It is by this proceeding that the distance of our satellite was finally
established, in 1751 and 1752, by two French astronomers, Lalande and
Lacaille; the former observing at Berlin, the latter at the Cape of Good
Hope. The result of their combined observations showed that the angle
formed at the center of the lunar disk by the half-diameter of the Earth
is 57 minutes of arc (a little less than a degree). This is known as the
_parallax_ of the Moon.
Here is a more or less alarming word; yet it is one that we can not
dispense with in discussing the distance of the stars. This astronomical
term will soon become familiar in the course of the present lesson,
where it will frequently recur, and always in connection with the
measurement of celestial distances. "Do not let us fear," wrote Lalande
in his _Astronomie des Dames_, "do not let us fear to use the term
parallax, despite its scientific aspect; it is convenient, and this term
explains a very simple and very familiar effect."
"If one is at the play," he continues, "behind a woman whose hat is too
large, and prevents one from seeing the stage [written a hundred years
ago!], one leans to the left or right, one rises or stoops: all this is
a parallax, a diversity of aspect, in virtue of which the hat appears to
correspond with another part of the theater from that in which are the
actors." "It is thus," he adds, "that there may be an eclipse of the Sun
in Africa and none for us, and that we see the Sun perfectly, because we
are high enough to prevent the Moon's hiding it from us."
See how simple it is. This parallax of 57 minutes proves that the Earth
is removed from the Moon at a distance of about 60 times its
half-diameter (precisely, 60.27). From this to the distance of the Moon
in kilometers is only a step, because it suffices to multiply the
half-diameter of the Earth, which is 6,371 kilometers (3,950 miles) by
this number. The distance of our satellite, accordingly, is 6,371
kilometers, multiplied by 60.27--that is, 384,000 kilometers (238,000
miles). The parallax of the Moon not only tells us definitely the
distance of our planet, but also permits us to calculate its real volume
by the measure of its apparent volume. As the diameter of the Moon seen
from the Earth subtends an angle of 31', while that of the Earth seen
from the Moon is 114', the real diameter of the orb of night must be to
that of the terrestrial globe in the relation of 273 to 1,000. That is a
little more than a quarter, or 3,480 kilometers (2,157 miles), the
diameter of our planet being 12,742 kilometers (7,900 miles).
This distance, calculated thus by geometry, is positively determined
with greater precision than that employed in the ordinary measurements
of terrestrial distances, such as the length of a road, or of a railway.
This statement may seem to be a romance to many, but it is undeniable
that the distance separating the Earth from the Moon is measured with
greater care than, for instance, the length of the road from Paris to
Marseilles, or the weight of a pound of sugar at the grocer's. (And we
may add without comment, that the astronomers are incomparably more
conscientious in their measurements than the most scrupulous
shop-keepers.)
Had we conveyed ourselves to the Moon in order to determine its distance
and its diameter directly, we should have arrived at no greater
precision, and we should, moreover, have had to plan out a journey
which in itself is the most insurmountable of all the problems.
The Moon is at the frontier of our little terrestrial province: one
might say that it traces the limits of our domain in space. And yet, a
distance of 384,000 kilometers (238,000 miles) separates the planet from
the satellite. This space is insignificant in the immeasurable distances
of Heaven: for the Saturnians (if such exist!) the Earth and the Moon
are confounded in one tiny star; but for the inhabitants of our globe,
the distance is beyond all to which we are accustomed. Let us try,
however, to span it in thought.
A cannon-ball at constant speed of 500 meters (547 yards) per second
would travel 8 days, 5 hours to reach the Moon. A train started at a
speed of one kilometer per minute, would arrive at the end of an
uninterrupted journey in 384,000 minutes, or 6,400 hours, or 266 days,
16 hours. And in less than the time it takes to write the name of the
Queen of Night, a telegraphic message would convey our news to the Moon
in one and a quarter seconds.
Long-distance travelers who have been round the world some dozen times
have journeyed a greater distance.
The other stars (beginning with the Sun) are incomparably farther from
us. Yet it has been found possible to determine their distances, and
the same method has been employed.
But it will at once be seen that different measures are required in
calculating the distance of the Sun, 388 times farther from us than the
Moon, for from here to the orb of day is 12,000 times the breadth of our
planet. Here we must not think of erecting a triangle with the diameter
of the Earth for its base: the two ideal lines drawn from the
extremities of this diameter would come together between the Earth and
the Sun; there would be no triangle, and the measurement would be
absurd.
In order to measure the distance which separates the Earth from the Sun,
we have recourse to the fine planet Venus, whose orbit is situated
inside the terrestrial orbit. Owing to the combination of the Earth's
motion with that of the Star of the Morning and Evening, the capricious
Venus passes in front of the Sun at the curious intervals of 8 years,
113-1/2 years less 8 years, 8 years, 113-1/2 years plus 8 years.
Thus there was a transit in June, 1761, then another 8 years after, in
June, 1769. The next occurred 113-1/2 years less 8 years, _i.e._,
105-1/2 years after the preceding, in December, 1874; the next in
December, 1882. The next will be in June, 2004, and June, 2012. At these
eagerly anticipated epochs, astronomers watch the transit of Venus
across the Sun at two terrestrial stations as far as possible removed
from each other, marking the two points at which the planet, seen from
their respective stations, appears to be projected at the same moment on
the solar disk. This measure gives the width of an angle formed by two
lines, which starting from two diametrically opposite points of the
Earth, cross upon Venus, and form an identical angle upon the Sun. Venus
is thus at the apex of two equal triangles, the bases of which rest,
respectively, upon the Earth and on the Sun. The measurement of this
angle gives what is called the parallax of the Sun--that is, the angular
dimension at which the Earth would be seen at the distance of the Sun.
[Illustration: FIG. 83.--Measurement of the distance of the Sun.]
Thus, it has been found that the half-diameter of the Earth viewed from
the Sun measures 8.82". Now, we know that an object presenting an angle
of one degree is at a distance of 57 times its length.
The same object, if it subtends an angle of a minute, or the sixtieth
part of a degree, indicates by the measurement of its angle that it is
60 times more distant, _i.e._, 3,438 times.
Finally, an object that measures one second, or the sixtieth part of a
minute, is at a distance of 206,265 times its length.
Hence we find that the Earth is at a distance from the Sun of
206,265/8.82--that is, 23,386 times its half-diameter, that is,
149,000,000 kilometers (93,000,000 miles). This measurement again is as
precise and certain as that of the Moon.
I hope my readers will easily grasp this simple method of triangulation,
the result of which indicates to us with absolute certainty the distance
of the two great celestial torches to which we owe the radiant light of
day and the gentle illumination of our nights.
The distance of the Sun has, moreover, been confirmed by other means,
whose results agree perfectly with the preceding. The two principal are
based on the velocity of light. The propagation of light is not
instantaneous, and notwithstanding the extreme rapidity of its
movements, a certain time is required for its transmission from one
point to another. On the Earth, this velocity has been measured as
300,000 kilometers (186,000 miles) per second. To come from Jupiter to
the Earth, it requires thirty to forty minutes, according to the
distance of the planet. Now, in examining the eclipses of Jupiter's
satellites, it has been discovered that there is a difference of 16
minutes, 34 seconds in the moment of their occurrence, according as
Jupiter is on one side or on the other of the Sun, relatively to the
Earth, at the minimum and maximum distance. If the light takes 16
minutes, 34 seconds to traverse the terrestrial orbit, it must take less
than that time, or 8 minutes, 17 seconds, to come to us from the Sun,
which is situated at the center. Knowing the velocity of light, the
distance of the Sun is easily found by multiplying 300,000 by 8 minutes,
17 seconds, or 497 seconds, which gives about 149,000,000 kilometers
(93,000,000 miles).
Another method founded upon the velocity of light again gives a
confirmatory result. A familiar example will explain it: Let us imagine
ourselves exposed to a vertical rain; the degree of inclination of our
umbrella will depend on the relation between our speed and that of the
drops of rain. The more quickly we run, the more we need to dip our
umbrella in order not to meet the drops of water. Now the same thing
occurs for light. The stars, disseminated in space, shed floods of light
upon the Heavens. If the Earth were motionless, the luminous rays would
reach us directly. But our planet is spinning, racing, with the utmost
speed, and in our astronomical observations we are forced to follow its
movements, and to incline our telescopes in the direction of its
advance. This phenomenon, known under the name of _aberration_ of light,
is the result of the combined effects of the velocity of light and of
the Earth's motion. It shows that the speed of our globe is equivalent
to 1/10000 that of light, _i.e._, = about 30 kilometers (19 miles) per
second. Our planet accordingly accomplishes her revolution round the Sun
along an orbit which she traverses at a speed of 30 kilometers (better
29-1/2) per second, or 1,770 kilometers per minute, or 106,000
kilometers per hour, or 2,592,000 kilometers per day, or 946,080,000
kilometers (586,569,600 miles) in the year. This is the length of the
elliptical path described by the Earth in her annual translation.
The length of orbit being thus discovered, one can calculate its
diameter, the half of which is exactly the distance of the Sun.
We may cite one last method, whose data, based upon attraction, are
provided by the motions of our satellite. The Moon is a little disturbed
in the regularity of her course round the Earth by the influence of the
powerful Sun. As the attraction varies inversely with the square of the
distance, the distance may be determined by analyzing the effect it has
upon the Moon.
Other means, on which we will not enlarge in this summary of the methods
employed for determinations, confirm the precisions of these
measurements with certainty. Our readers must forgive us for dwelling
at some length upon the distance of the orb of day, since this
measurement is of the highest importance; it serves as the base for the
valuation of all stellar distances, and may be considered as the meter
of the universe.
This radiant Sun to which we owe so much is therefore enthroned in space
at a distance of 149,000,000 kilometers (93,000,000 miles) from here.
Its vast brazier must indeed be powerful for its influence to be exerted
upon us to such a manifest extent, it being the very condition of our
existence, and reaching out as far as Neptune, thirty times more remote
than ourselves from the solar focus.
It is on account of its great distance that the Sun appears to us no
larger than the Moon, which is only 384,000 kilometers (238,000 miles)
from here, and is itself illuminated by the brilliancy of this splendid
orb.
No terrestrial distance admits of our conceiving of this distance. Yet,
if we associate the idea of space with the idea of time, as we have
already done for the Moon, we may attempt to picture this abyss. The
train cited just now would, if started at a speed of a kilometer a
minute, arrive at the Sun after an uninterrupted course of 283 years,
and taking as long to return to the Earth the total would be 566 years.
Fourteen generations of stokers would be employed on this celestial
excursion before the bold travelers could bring back news of the
expedition to us.
Sound is transmitted through the air at a velocity of 340 meters (1,115
feet) per second. If our atmosphere reached to the Sun, the noise of an
explosion sufficiently formidable to be heard here would only reach us
at the end of 13 years, 9 months. But the more rapid carriers, such as
the telegraph, would leap across to the orb of day in 8 minutes, 17
seconds.
Our imagination is confounded before this gulf of 93,000,000 miles,
across which we see our dazzling Sun, whose burning rays fly rapidly
through space in order to reach us.
* * * * *
And now let us see how the distances of the planets were determined.
We will leave aside the method of which we have been speaking; that now
to be employed is quite different, but equally precise in its results.
It is obvious that the revolution of a planet round the Sun will be
longer in proportion as the distance is greater, and the orbit that has
to be traveled vaster. This is simple. But the most curious thing is
that there is a geometric proportion in the relations between the
duration of the revolutions of the planets and their distances. This
proportion was discovered by Kepler, after thirty years of research,
and embodied in the following formula:
"The squares of the times of revolution of the planets round the Sun
(the periodic times) are proportional to the cubes of their mean
distances from the Sun."
This is enough to alarm the boldest reader. And yet, if we unravel this
somewhat incomprehensible phrase, we are struck with its simplicity.
What is a square? We all know this much; it is taught to children of ten
years old. But lest it has slipped your memory: a square is simply a
number multiplied by itself.
Thus: 2 × 2 = 4; 4 is the square of 2.
Four times 4 is 16; 16 is the square of 4.
And so on, indefinitely.
Now, what is a cube? It is no more difficult. It is a number multiplied
twice by itself.
For instance: 2 multiplied by 2 and again by 2 equals 8. So 8 is the
cube of 2. 3 × 3 × 3 = 27; 27 is the cube of 3, and so on.
Now let us take an example that will show the simplicity and precision
of the formula enunciated above. Let us choose a planet, no matter
which. Say, Jupiter, the giant of the worlds. He is the Lord of our
planetary group. This colossal star is five times (precisely, 5.2) as
far from us as the Sun.
Multiply this number twice by itself 5.2 × 5.2 × 5.2 = 140.
On the other hand, the revolution of Jupiter takes almost twelve years
(11.85). This number multiplied by itself also equals 140. The square of
the number 11.85 is equal to the cube of the number 5.2. This very
simple law regulates all the heavenly bodies.
Thus, to find the distance of a planet, it is sufficient to observe the
time of its revolution, then to discover the square of the given number
by multiplying it into itself. The result of the operation gives
simultaneously the cube of the number that represents the distance.
To express this distance in kilometers (or miles), it is sufficient to
multiply it by 149,000,000 (in miles 93,000,000), the key to the system
of the world.
Nothing, then, could be less complicated than the definition of these
methods. A few moments of attention reveal to us in their majestic
simplicity the immutable laws that preside over the immense harmony of
the Heavens.
* * * * *
But we must not confine ourselves to our own solar province. We have yet
to speak of the stars that reign in infinite space far beyond our
radiant Sun.
Strange and audacious as it may appear, the human mind is able to cross
these heights, to rise on the wings of genius to these distant suns,
and to plumb the depths of the abyss that separates us from these
celestial kingdoms.
Here, we return to our first method, that of triangulation. And the
distance that separates us from the Sun must serve in calculating the
distances of the stars.
The Earth, spinning round the Sun at a distance of 149,000,000
kilometers (93,000,000 miles), describes a circumference, or rather an
ellipse, of 936,000,000 kilometers (580,320,000 miles), which it travels
over in a year. The distance of any point of the terrestrial orbit from
the diametrically opposite point which it passes six months later is
298,000,000 kilometers (184,760,000 miles), _i.e._, the diameter of this
orbit. This immense distance (in comparison with those with which we are
familiar) serves as the base of a triangle of which the apex is a star.
The difficulty in exact measurements of the distance of a star consists
in observing the little luminous point persistently for a whole year, to
see if this star is stationary, or if it describes a minute ellipse
reproducing in perspective the annual revolution of the Earth.
If it remains fixed, it is lost in such depths of space that it is
impossible to gage the distance, and our 298,000,000 kilometers have no
meaning in view of such an abyss. If, on the contrary, it is displaced,
it will in the year describe a minute ellipse, which is only the
reflection, the perspective in miniature, of the revolution of our
planet round the Sun.
The annual parallax of a star is the angle under which one would see the
radius, or half-diameter, of the terrestrial orbit from it. This radius
of 149,000,000 kilometers (93,000,000 miles) is indeed, as previously
observed, the unit, the meter of celestial measures. The angle is of
course smaller in proportion as the star is more distant, and the
apparent motion of the star diminishes in the same proportion. But the
stars are all so distant that their annual displacement of perspective
is almost imperceptible, and very exact instruments are required for its
detection.
[Illustration: FIG. 84.--Small apparent ellipses described by the stars
as a result of the annual displacement of the Earth.]
The researches of the astronomers have proved that there is not one star
for which the parallax is equal to that of another. The minuteness of
this angle, and the extraordinary difficulties experienced in measuring
the distance of the stars, will be appreciated from the fact that the
value of a second is so small that the displacement of any star
corresponding with it could be covered by a spider's thread.
A second of arc corresponds to the size of an object at a distance of
206,265 times its diameter; to a millimeter seen at 206 meters'
distance; to a hair, 1/10 of a millimeter in thickness, at 20 meters'
distance (more invisible to the naked eye). And yet this value is in
excess of those actually obtained. In fact:--the apparent displacement
of the nearest star is calculated at 75/100 of a second (0.75"), _i.e._,
from this star, [alpha] of Centaur, the half-diameter of the terrestrial
orbit is reduced to this infinitesimal dimension. Now in order that the
length of any straight line seen from the front be reduced until it
appear to subtend no more than an angle of 0.75", it must be removed to
a distance 275,000 times its length. As the radius of the terrestrial
orbit is 149,000,000 kilometers (93,000,000 miles), the distance which
separates [alpha] of Centaur from our world must therefore =
41,000,000,000,000 kilometers (25,000,000,000,000 miles). And that is
the nearest star. We saw in Chapter II that it shines in the southern
hemisphere. The next, and one that can be seen in our latitudes, is 61
of Cygnus, which floats in the Heavens 68,000,000,000,000 kilometers
(42,000,000,000,000 miles) from here. This little star, of fifth
magnitude, was the first of which the distance was determined (by
Bessel, 1837-1840).
All the rest are much more remote, and the procession is extended to
infinity.
We can not conceive directly of such distances, and in order to imagine
them we must again measure space by time.
In order to cover the distance that separates us from our neighbor,
[alpha] of Centaur, _light_, the most rapid of all couriers, takes 4
years, 128 days. If we would follow it, we must not jump from start to
finish, for that would not give us the faintest idea of the distance: we
must take the trouble to think out the direct advance of the ray of
light, and associate ourselves with its progress. We must see it
traverse 300,000 kilometers (186,000 miles) during the first second of
the journey; then 300,000 more in the second, which makes 600,000
kilometers; then once more 300,000 kilometers during the third, and so
on without stopping for four years and four months. If we take this
trouble we may realize the value of the figure; otherwise, as this
number surpasses all that we are in the habit of realizing, it will have
no significance for us, and will be a dead letter.
If some appalling explosion occurred in this star, and the sound in its
flight of 340 meters (1,115 feet) per second were able to cross the
void that separates us from it, the noise of this explosion would only
reach us in 3,000,000 years.
A train started at a speed of 106 kilometers (65 miles) per hour would
have to run for 46,000,000 years, in order to reach this star, our
neighbor in the celestial kingdom.
The distance of some thirty of the stars has been determined, but the
results are dubious.
The dazzling Sirius reigns 92,000,000,000,000 kilometers
(57,000,000,000,000 miles), the pale Vega at 204,000,000,000,000. Each
of these magnificent stars must be a huge sun to burn at such a distance
with such luminosity. Some are millions of times larger than the Earth.
Most of them are more voluminous than our Sun. On all sides they
scintillate at inaccessible distances, and their light strays a long
while in space before it encounters the Earth. The luminous ray that we
receive to-day from some pale star hardly perceptible to our eyes--so
enormous is its distance--may perhaps bring us the last emanation of a
sun that expired thousands of years ago.
* * * * *
If these methods have been clear to my readers, they may also be
interested perhaps in knowing the means employed in weighing the worlds.
The process is as simple and as clear as those of which we have been
speaking.
_Weighing the stars!_ Such a pretension seems Utopian, and one asks
oneself curiously what sort of balance the astronomers must have adopted
in order to calculate the weight of Sun, Moon, planets or stars.
Here, figures replace weights. Ladies proverbially dislike figures: yet
it would be easier for some society dame to weigh the Sun at the point
of her pen, by writing down a few columns of figures with a little care,
than to weigh a 12 kilogram case of fruit, or a dress-basket of 35
kilos, by direct methods.
Weighing the Sun is an amusement like any other, and a change of
occupation.
If the Moon were not attracted by the Earth, she would glide through the
Heavens along an indefinite straight line, escaping at the tangent. But
in virtue of the attraction that governs the movements of all the
Heavenly bodies, our satellite at a distance of 60 times the terrestrial
half-diameter revolves round us in 27 days, 7 hours, 43 minutes, 11-1/2
seconds, continually leaving the straight line to approach the Earth,
and describing an almost circular orbit in space. If at any moment we
trace an arc of the lunar orbit, and if a tangent is taken to this arc,
the deviation from the straight line caused by the attraction of our
planet is found to be 1-1/3 millimeter per second.
This is the quantity by which the Moon drops toward us in each second,
during which she accomplishes 1,017 meters of her orbit.
On the other hand, no body can fall unless it be attracted, drawn by
another body of a more powerful mass.
Beings, animals, objects, adhere to the soil, and weigh upon the Earth,
because they are constantly attracted to it by an irresistible force.
Weight and universal attraction are one and the same force.
On the other hand, it can be determined that if an object is left to
itself upon the surface of the Earth, it drops 4.90 meters during the
first second of its fall.
We also know that attraction diminishes with the square of the distance,
and that if we could raise a stone to the height of the Moon, and then
abandon it to the attraction of our planet, it would in the first second
fall 4.90 meters divided by the square of 60, or 3,600--that is, of
1-1/3 millimeters, exactly the quantity by which the Moon deviates from
the straight line she would pursue if the Earth were not influencing
her.
The reasoning just stated for the Moon is equally applicable to the Sun.
The distance of the Sun is 23,386 times the radius of the Earth. In
order to know how much the intensity of terrestrial weight would be
diminished at such a distance, we should look, in the first place, for
the square of the number representing the distance--that is, 23,386
multiplied by itself, = 546,905,000. If we divide 4.90 meters, which
represents the attractive force of our planet, by this number, we get
9/1000000 of a millimeter, and we see that at the distance of the Sun,
the Earth's attraction would really be almost _nil_.
Now let us do for our planet what we did for its satellite. Let us trace
the annual orbit of the terrestrial globe round the central orb, and we
shall find that the Earth falls in each second 2.9 millimeters toward
the Sun.
This proportion gives the attractive force of the Sun in relation to
that of the Earth, and proves that the Sun is 324,000 times more
powerful than our world, for 2.9 millimeters divided by 0.000,009 equals
324,000, if worked out into the ultimate fractions neglected here for
the sake of simplicity.
A great number of stars have been weighed by the same method.
Their mass is estimated by the movement of a satellite round them, and
it is by this method that we are able to affirm that Jupiter is 310
times heavier than the Earth, Saturn 92 times, Neptune 16 times, Uranus
14 times, while Mars is much less heavy, its weight being only
two-thirds that of our own.
The planets which have no satellites have been weighed by the
perturbations which they cause in other stars, or in the imprudent
comets that sometimes tarry in their vicinity. Mercury weighs very much
less than the Earth (only 6/100) and Venus about 8/10. So the beautiful
star of the evening and morning is not so light as her name might imply,
and there is no great difference between her weight and our own.
As the Moon has no secondary body submitted to her influence, her weight
has been calculated by reckoning the amount of water she attracts at
each tide in the ocean, or by observing the effects of her attraction on
the terrestrial globe. When the Moon is before us, in the last quarter,
she makes us travel faster, whereas in the first quarter, when she is
behind, she delays us.
All the calculations agree in showing us that the orb of night is 81
times less heavy than our planet. There is nearly as much difference in
weight between the Earth and the Moon as between an orange and a grape.
* * * * *
Not content with weighing the planets of our system, astronomers have
investigated the weight of the stars. How have they been enabled to
ascertain the quantity of matter which constitutes these distant
Suns--incandescent globes of fire scattered in the depths of space?
They have resorted to the same method, and it is by the study of the
attractive influence of a sun upon some other contiguous neighboring
star, that the weight of a few of these has been calculated.
Of course this method can only be applied to those double stars of which
the distance is known.
It has been discovered that some of the tiny stars that we can hardly
see twinkling in the depths of the azure sky are enormous suns, larger
and heavier than our own, and millions of times more voluminous than the
Earth.
Our planet is only a grain of dust floating in the immensity of Heaven.
Yet this atom of infinity is the cradle of an immense creation
incessantly renewed, and perpetually transformed by the accumulated
centuries.
And what diversity exists in this army of worlds and suns, whose regular
harmonious march obeys a mute order....
But we have as yet said nothing about weight on the surface of the
worlds, and I see signs of impatience in my readers, for after so much
simple if unpoetical demonstration, they will certainly ask me for the
explanation that will prove to them that a kilogram transported to
Jupiter or Mars would weigh more or less than here.
Give me your attention five minutes longer, and I will restore your
faith in the astronomers.
It must not be supposed that objects at the surface of a world like
Jupiter, 310 times heavier than our own, weigh 310 times more. That
would be a serious error. In that case we should have to assume that a
kilogram transported to the surface of the Sun would there weigh 324,000
times more, or 324,000 kilograms. That would be correct if these orbs
were of the same dimensions as the Earth. But to speak, for instance,
only of the divine Sun, we know that he is 108 times larger than our
little planet.
Now, weight at the surface of a celestial body depends not only on its
mass, but also on its diameter.
In order to know the weight of any body upon the surface of the Sun, we
must argue as follows:
Since a body placed upon the surface of the Sun is 108 times farther
from its center than it is upon a globe of the dimensions of the Earth,
and since, on the other hand, attraction diminishes with the square of
the distance, the intensity of the weight would there be 108 multiplied
by 108, or 11,700 times weaker. Now divide the number representing the
mass, _i.e._, 324,000, by this number 11,700, and it results that bodies
at the surface of the Sun are 28 times heavier than here. A woman whose
weight was 60 kilos would weigh 1,680 kilograms there if organized in
the same way as on the Earth, and would find walking very difficult, for
at each step she would lift up a shoe that weighed at least ten
kilograms.
This reasoning as just stated for the Sun may be applied to the other
stars. We know that on the surface of Jupiter the intensity of weight is
twice and a third times as great as here, while on Mars it only equals
37/100.
On the surface of Mercury, weight is nearly twice as small again as
here. On Neptune it is approximately equal to our own.
With deference to the Selenites, everything is at its lightest on the
Moon: a man weighing 70 kilograms on the Earth would not weigh more than
12 kilos there.
So all tastes can be provided for: the only thing to be regretted is
that one can not choose one's planet with the same facility as one's
residence upon the Earth.
CHAPTER XII
LIFE, UNIVERSAL AND ETERNAL
And now, while thanking my readers for having followed me so far in this
descriptive account of the marvels of the Cosmos, I must inquire what
philosophical impression has been produced on their minds by these
celestial excursions to the other worlds? Are you left indifferent to
the pageant of the Heavens? When your imagination was borne away to
these distant stars, suns of the infinite, these innumerable stellar
systems disseminated through a boundless eternity, did you ask what
existed there, what purpose was served by those dazzling spheres, what
effects resulted from these forces, radiations, energies? Did you
reflect that the elements which upon our little Earth determined a vital
activity so prodigious and so varied must needs have spread the waves of
an incomparably vaster and more diversified existence throughout the
immensities of the Universe? Have you felt that all can not be dead and
deserted, as we are tempted by the illusions of our terrestrial senses
and of our isolation to believe in the silence of the night: that on the
contrary, the real aim of Astronomy, instead of ending with statements
of the positions and movements of the stars, is to enable us to
penetrate to them, to make us divine, and know, and appreciate their
physical constitution, their degree of life and intellectuality in the
universal order?
On the Earth, it is Life and Thought that flourish; and it is Life and
Thought that we seek again in these starry constellations strewn to
Infinitude amid the immeasurable fields of Heaven.
The humble little planet that we inhabit presents itself to us as a
brimming cup, overflowing at every outlet. Life is everywhere. From the
bottom of the seas, from the valleys to the mountains, from the
vegetation that carpets the soil, from the mold in the fields and woods,
from the air we breathe, arises an immense, prodigious, and perpetual
murmur. Listen! it is the great voice of Nature, the sum of all the
unknown and mysterious voices that are forever calling to us, from the
ocean waves, from the forest winds, from the 300,000 kinds of insects
that are redundant everywhere, and make a lively community on the
surface of our globe. A drop of water contains thousands of curious and
agile creatures. A grain of dust from the streets of Paris is the home
of 130,000 bacteria. If we turn over the soil of a garden, field, or
meadow, we find the earthworms working to produce assimilable slime. If
we lift a stone in the path, we discover a crawling population. If we
gather a flower, detach a leaf, we everywhere find little insects living
a parasitic existence. Swarms of midges fly in the sun, the trees of the
wood are peopled with nests, the birds sing, and chase each other at
play, the lizards dart away at our approach, we trample down the
antheaps and the molehills. Life enwraps us in an inexorable
encroachment of which we are at once the heroes and the victims,
perpetuating itself to its own detriment, as imposed upon it by an
eternal reproduction. And this from all time, for the very stones of
which we build our houses are full of fossils so prodigiously multiplied
that one gram of such stone will often contain millions of shells,
marvels of geometrical perfection. The infinitely little is equal to the
infinitely great.
Life appears to us as a fatal law, an imperious force which all obey, as
the result and the aim of the association of atoms. This is illustrated
for us upon the Earth, our only field of direct observation. We must be
blind not to see this spectacle, deaf not to hear its reaching. On what
pretext could one suppose that our little globe which, as we have seen,
has received no privileges from Nature, is the exception; and that the
entire Universe, save for one insignificant isle, is devoted to vacancy,
solitude, and death?
We have a tendency to imagine that Life can not exist under conditions
other than terrestrial, and that the other worlds can only be inhabited
on the condition of being similar to our own. But terrestrial nature
itself demonstrates to us the error of this way of thinking. We die in
the water: fishes die out of the water. Again, short-sighted naturalists
affirm categorically that Life is impossible at the bottom of the sea:
1, because it is in complete darkness; 2, because the terrible pressure
would burst any organism; 3, because all motion would be impossible
there, and so on. Some inquisitive person sends down a dredge, and
brings up lovely creatures, so delicate in structure that the daintiest
touch must proceed with circumspection. There is no light in these
depths: they make it with their own phosphorescence. Other inquirers
visit subterranean caverns, and discover animals and plants whose organs
have been transformed by adaptation to their gloomy environment.
What right have we to say to the vital energy that radiates round every
Sun of the Universe: "Thus far shalt thou come, and no further"? In the
name of Science? An absolute mistake. The Known is an infinitesimal
island in the midst of the vast ocean of the Unknown. The deep seas
which seemed to be a barrier are, as we have seen, peopled with special
life. Some one objects: But after all, there is air there, there is
oxygen: oxygen is indispensable: a world without oxygen would be a
world of death, an eternally sterile desert. Why? Because we have not
yet come across beings that can breathe without air, and live without
oxygen? Another mistake. Even if we did not know of any, it would not
prove that they do not exist. But as it happens, we do know of such: the
_anærobia_. These beings live without air, without oxygen. Better still:
oxygen kills them!
All the evidence goes to show that in interpreting as we ought the
spectacle of terrestrial life, and the positive facts acquired by
Science, we should enlarge the circle of our conceptions and our
judgments, and not limit extra-terrestrial existence to the servile
image of what is in existence here below. Terrestrial organic forms are
due to local causes upon our planet. The chemical constitution of water
and of the atmosphere, temperature, light, density, weight, are so many
elements that have gone to form our bodies. Our flesh is composed of
carbon, nitrogen, hydrogen, and oxygen combined in the state of water,
and of some other elements, among which we may instance sodium chloride
(salt). The flesh of animals is not chemically different from our own.
All this comes from the water and the air, and returns to them again.
The same elements, in very minute quantities, make up all living bodies.
The ox that browses on the grass is formed of the same flesh as the man
who eats the beef. All organized terrestrial matter is only carbon
combined in variable proportions with hydrogen, nitrogen, oxygen, etc.
But we have no right to forbid Nature to act differently in worlds from
which carbon is absent. A world, for example, in which silica replaces
carbon, silicic acid carbonic acid, might be inhabited by organisms
absolutely different from those which exist on the Earth, different not
only in form, but also in substance. We already know stars and suns for
which spectral analysis reveals a predominance of silica, _e.g._, Rigel
and Deneb. In a world where chlorine predominated, we might expect to
find hydrochloric acid, and all the fecund family of chlorides, playing
an important part in the phenomena of life. Might not bromine be
associated in other formations? Why, indeed, should we draw the line at
terrestrial chemistry? What is to prove that these elements are really
simple? May not hydrogen, carbon, oxygen, nitrogen, and sulphur all be
compounds? Their equivalents are multiples of the first: 1, 6, 8, 14,
16. And is even hydrogen the most simple of the elements? Is not its
molecule composed of atoms, and may there not exist a single species of
primitive atom, whose geometric arrangement and various associations
might constitute the molecules of the so-called simple elements?
In our own solar system we discover the essential differences between
certain planets. In the spectrum of Jupiter, for instance, we are aware
of the action of an unknown substance that manifests itself by a marked
absorption of certain red rays. This gas, which does not exist upon the
Earth, is seen still more obviously in the atmospheres of Saturn and
Uranus. Indeed, upon this last planet the atmosphere appears, apart from
its water vapor, to have no sort of analogy with our own. And in the
solar spectrum itself, many of the lines have not yet been identified
with terrestrial substances.
The interrelation of the planets is of course incontrovertible, since
they are all children of the same parent. But they differ among
themselves, not merely in respect of situation, position, volume, mass,
density, temperature, atmosphere, but again in physical and chemical
constitution. And the point we would now accent is that this diversity
should not be regarded as an obstacle to the manifestations of life,
but, on the contrary, as a new field open to the infinite fecundity of
the universal mother.
When our thoughts take wing, not only to our neighbors, Moon, Venus,
Mars, Jupiter, or Saturn, but still more toward the myriads of unknown
worlds that gravitate round the suns disseminated in space, we have no
plausible reason for imagining that the inhabitants of these other
worlds of Heaven resemble us in any way, whether in form, or even in
organic substance.
The substance of the terrestrial human body is due to the elements of
our planet, and notably to carbon. The terrestrial human form derives
from the ancestral animal forms to which it has gradually raised itself
by the continuous progress of the transformation of species. To us it
seems obvious that we are man or woman, because we have a head, a heart,
lungs, two legs, two arms, and so on. Nothing is less a matter of
course. That we are constituted as we are, is simply the result of our
pro-simian ancestors having also had a head, a heart, lungs, legs, and
arms--less elegant than your own, it is true, Madam, but still of the
same anatomy. And more and more, by the progress of paleontology, we are
delving down to the origin of beings. As certain as it is that the bird
derives from the reptile by a process of organic evolution, so certain
is it that terrestrial Humanity represents the topmost branches of the
huge genealogical tree, whereof all the limbs are brothers, and the
roots of which are plunged into the very rudiments of the most
elementary and primitive organisms.
The multitude of worlds is surely peopled by every imaginable and
unimaginable form. Terrestrial man is endowed with five senses, or
perhaps it is better to say six. Why should Nature stop at this point?
Why, for instance, may she not have given to certain beings an
electrical sense, a magnetic sense, a sense of orientation, an organ
able to perceive the ethereal vibrations of the infra-red or
ultra-violet, or permitted them to hear at a distance, or to see through
walls? We eat and digest like coarse animals, we are slaves to our
digestive tube: may there not be worlds in which a nutritive atmosphere
enables its fortunate inhabitants to dispense with this absurd process?
The least sparrow, even the dusky bat, has an advantage over us in that
it can fly through the air. Think how inferior are our conditions, since
the man of greatest genius, the most exquisite woman, are nailed to the
soil like any vulgar caterpillar before its metamorphosis! Would it be a
disadvantage to inhabit a world in which we might fly whither we would;
a world of scented luxury, full of animated flowers; a world where the
winds would be incapable of exciting a tempest, where several suns of
different colors--the diamond glowing with the ruby, or the emerald with
the sapphire--would burn night and day (azure nights and scarlet days)
in the glory of an eternal spring; with multi-colored moons sleeping in
the mirror of the waters, phosphorescent mountains, aerial
inhabitants,--men, women, or perhaps of other sexes,--perfect in their
forms, gifted with multiple sensibilities, luminous at will,
incombustible as asbestos, perhaps immortal, unless they commit suicide
out of curiosity? Lilliputian atoms as we are, let us once for all be
convinced that our imagination is but sterility, in the midst of an
infinitude hardly glimpsed by the telescope.
One important point seems always to be ignored expressly by those who
blindly deny the doctrine of the plurality of worlds. It is that this
doctrine does not apply more particularly to the present epoch than to
any other. _Our_ time is of no importance, no absolute value. Eternity
is the field of the Eternal Sower. There is no reason why the other
worlds should be inhabited _now_ more than at any other epoch.
What, indeed, is the Present Moment? It is an open trap through which
the Future falls incessantly into the gulf of the Past.
The immensity of Heaven bears in its bosom cradles as well as tombs,
worlds to come and perished worlds. It abounds in extinct suns, and
cemeteries. In all probability Jupiter is not yet inhabited. What does
this prove? The Earth was not inhabited during its primordial period:
what did that prove to the inhabitants of Mars or of the Moon, who were
perhaps observing it at that epoch, a few million years ago?
To pretend that our globe must be the only inhabited world because the
others do not resemble it, is to reason, not like a philosopher, but, as
we remarked before, like a fish. Every rational fish ought to assume
that it is impossible to live out of water, since its outlook and its
philosophy do not extend beyond its daily life. There is no answer to
this order of reasoning, except to advise a little wider perception, and
extension of the too narrow horizon of habitual ideas.
For us the resources of Nature may be considered infinite, and
"positive" science, founded upon our senses only, is altogether
inadequate, although it is the only possible basis of our reasoning. We
must learn to see with the eyes of our spirit.
As to the planetary systems other than our own, we are no longer reduced
to hypotheses. We already know with certainty that our Sun is no
exception, as was suggested, and is still maintained, by some theorists.
The discovery in itself is curious enough.
It is surely an exceptional situation that, given a sidereal system
composed of a central sun, and of one or more stars gravitating round
him, the plane of such a system should fall just within our line of
vision, and that it should revolve in such a way that the globes of
which it is composed pass exactly between this sun and ourselves in
turning round him, eclipsing him more or less during this transit. As,
on the other hand, the eclipses would be our only means of determining
the existence of these unknown planets (save indeed from perturbation,
as in the case of Sirius and Procyon), it might have seemed quixotic to
hope for like conditions in order to discover solar systems other than
our own. But these exceptional circumstances have reproduced themselves
at different parts of the Heavens.
Thus, for instance, we have seen that the variable star Algol owes its
variations in brilliancy, which reduce it from second to fourth
magnitude every sixty-nine hours, to the interposition of a body between
itself and the Earth, and celestial mechanics has already been able to
determine accurately the orbit of this body, its dimensions and its
mass, and even the flattening of the sun Algol. Here, then, is a system
in which we know the sun and an enormous planet, whose revolution is
effected in sixty-nine hours with extreme rapidity, as measured by the
spectroscope.
The star [delta] of Cepheus is in the same case: it is an orb eclipsed
in a period of 129 hours, and its eclipsing planet also revolves in the
plane of our vision. The variable star in Ophiuchus has an analogous
system, and observation has already revealed a great number of others.
Since, then, a certain number of solar systems differing from our own
have been revealed, as it were in section, to terrestrial observation,
this affords us sufficient evidence of the existence of an innumerable
quantity of solar systems scattered through the immensities of space,
and we are no longer reduced to conjecture.
On the other hand, analysis of the motions of several stars, such as
Sirius, Procyon, Altaïr, proves that these distant orbs have
companions,--planets not yet discovered by the telescope, and that
perhaps never will be discovered, because they are obscure, and lost in
the radiation of the star.
* * * * *
Some _savants_ have asserted that Life can not germinate if the
conditions of the environment differ too much from terrestrial
conditions.
This hypothesis is purely gratuitous, and we will now discuss it.
In order to examine what is happening on the Earth, let us mount the
ladder of time for a moment, to follow the evolutions of Nature.
There was an epoch when the Earth did not exist. Our planet, the future
world of our habitation, slept in the bosom of the solar nebula.
At last it came to birth, this cherished Earth, a gaseous, luminous
ball, poor reflection of the King of Orbs, its parent. Millions of years
rolled by before the condensation and cooling of this new globe were
sufficiently transformed to permit life to manifest itself in its most
rudimentary aspects.
The first organic forms of the protoplasm, the first aggregations of
cells, the protozoons, the zoophytes or plant-animals, the gelatinous
mussels of the still warm seas, were succeeded by the fishes, then by
the reptiles, the birds, the mammals, and lastly man, who at present
occupies the top of the genealogical tree, and crowns the animal
kingdom.
Humanity is comparatively young upon the Earth. We may attribute some
thousands of centuries of existence to it ... and some five years of
reason!
The terrestrial organisms, from the lowest up to man, are the resultant
of the forces in action at the surface of our planet. The earliest seem
to have been produced by the combinations of carbon with hydrogen and
nitrogen; they were, so to speak, without animation, save for some very
rudimentary sensibility; the sponges, corals, polyps, and medusæ, give
us a notion of these primitive beings. They were formed in the tepid
waters of the primary epoch. As long as there were no continents, no
islands emerging from the level of the universal ocean, there were no
beings breathing in the air. The first aquatic creatures were succeeded
by the amphibia, the reptiles. Later on were developed the mammals and
the birds.
What, again, do we not owe to the plant-world of the primary epoch, of
the secondary epoch, of the tertiary epoch, which slowly prepared the
good nutritious soil of to-day, in which the roses flourish, and the
peach and strawberry ripen?
Before it gave birth to a Helen or a Cleopatra, life manifested itself
under the roughest forms, and in the most varied conditions. A
long-period comet passing in sight of the Earth from time to time would
have seen modifications of existence in each of its transits, in
accordance with a slow evolution, corresponding to the variation of the
conditions of existence, and progressing incessantly, for if Life is the
goal of nature, Progress is the supreme law.
The history of our planet is the history of life, with all its
metamorphoses. It is the same for all the worlds, with some exceptions
of orbs arrested in their development.
The constitution of living beings is in absolute relation with the
substances of which they are composed, the environment in which they
move, temperature, light, weight, density, the length of day and night,
the seasons, etc.--in a word, with all the cosmographic elements of a
world.
If, for example, we compare between themselves two worlds such as the
Earth and Neptune, utterly different from the point of view of distance
from the Sun, we could not for an instant suppose that organic
structures could have followed a parallel development on these planets.
The average temperature must be much lower on Neptune than on the Earth,
and the same holds for intensity of light. The years and seasons there
are 165 times longer than with us, the density of matter is three times
as weak, and weight is, on the contrary, a little greater. Under
conditions so different from our own, the activities of Nature would
have to translate themselves under other forms. And doubtless the
elementary bodies would not be found there in the same proportions.
Consequently we have to conclude that organs and senses would not be the
same there as here. The optic nerve, for instance, which has formed and
developed here from the rudimentary organ of the trilobite to the
marvels of the human eye, must be incomparably more sensitive upon
Neptune than in our dazzling solar luminosity, in order to perceive
radiations that we do not perceive here. In all probability, it is
replaced there by some other organ. The lungs, functioning there in
another atmosphere, are different from our own. So, too, for the stomach
and digestive organs. Corporeal forms, animal and human, can not
resemble those which exist upon the Earth.
Certain _savants_ contend that if the conditions differed too much from
terrestrial conditions, life could not be produced there at all. Yet we
have no right to limit the powers of Nature to the narrow bounds of our
sphere of observation, and to pretend that our planet and our Humanity
are the type of all the worlds. That is a hypothesis as ridiculous as it
is childish.
Do not let us be "personal," like children, and old people who never see
beyond their room. Let us learn to live in the Infinite and the Eternal.
From this larger point of view, the doctrine of the plurality of worlds
is the complement and the natural crown of Astronomy. What interests us
most in the study of the Universe is surely to know what goes on there.
* * * * *
These considerations show that, in all the ages, what really constitutes
a planet is not its skeleton but the life that vibrates upon its
surface.
And again, if we analyze things, we see that for the Procession of
Nature, life is all, and matter nothing.
What has become of our ancestors, the millions of human beings who
preceded us upon this globe? Where are their bodies? What is left of
them? Search everywhere. Nothing is left but the molecules of air,
water, dust, atoms of hydrogen, nitrogen, oxygen, carbon, etc., which
are incorporated in turn in the organism of every living being.
The whole Earth is a vast cemetery, and its finest cities are rooted in
the catacombs. But now, in crossing Paris, I passed for at least the
thousandth time near the Church of St. Germain-l'Auxerrois, and was
obliged to turn out of the direct way, on account of excavations. I
looked down, and saw that immediately below the pavement, they had just
uncovered some stone coffins still containing the skeletons that had
reposed there for ten centuries. From time immemorial the passers-by had
trampled them unwittingly under foot. And I reflected that it is much
the same in every quarter of Paris. Only yesterday, some Roman tombs and
a coin with the effigy of Nero were found in a garden near the
Observatory.
And from the most general standpoint of Life, the whole world is in the
same case, and even more so, seeing that all that exists, all that
lives, is formed of elements that have already been incorporated in
other beings, no longer living. The roses that adorn the bosom of the
fair ... but I will not enlarge upon this topic.
And you, so strong and virile, of what elements is your splendid body
formed? Where have the elements you absorb to-day in respiration and
assimilation been drawn from, what lugubrious adventures have they been
subject to? Think away from it: do not insist on this point: on no
account consider it....
And yet, let us dwell on it, since this reality is the most evident
demonstration of the ideal; since what exists is you, is all of us, is
_Life_; and matter is only its substance, like the materials of a house,
and even less so, since its particles only pass rapidly through the
framework of our bodies. A heap of stones does not make a house.
Quintillions of tons of materials would not represent the Earth or any
other world.
Yes, what really exists, what constitutes a complete orb, is the city of
Life. Let us recognize that the flower of life flourishes on the surface
of our planet, embellishing it with its perfume; that it is just this
life that we see and admire,--of which we form part,--and which is the
_raison d'être_ of things; that matter floats, and crosses, and crosses
back again, in the web of living beings,--and the reality, the goal, is
not matter--it is the life matter is employed upon.
Yes, matter passes, and being also, after sharing in the concerted
symphony of life.
And indeed everything passes rapidly!
What irrepressible grief, what deep melancholy, what ineffaceable
regrets we feel, when as age comes on we look back, when we see our
friends fallen upon the road one after the other, above all when we
visit the beloved scenes of our childhood, those homes of other years,
that witnessed our first start in terrestrial existence, our first
games, our first affections--those affections of childhood that seemed
eternal--when we wander over those fields and valleys and hills, when
we see again the landscape whose aspect has hardly changed, and whose
image is so intimately linked with our first impressions. There near
this fireside the grandfather danced us on his knee, and told us
blood-curdling stories; here the kind grandmother came to see if we were
comfortably tucked in, and not likely to fall out of the big bed; in
this little wood, along these alleys that seemed endless, we spread our
nets for birds; in this stream we fished for crayfish; there on the path
we played at soldiers with our elders, who were always captains; on
these slopes we found rare stones and fossils, and mysterious
petrifactions; on this hill we admired the fine sunsets, the appearance
of the stars, the form of the constellations. There we began to live, to
think, to love, to form attachments, to dream, to question every
problem, to breathe intellectually and physically. And now, where is
this beloved grandfather? the good grandmother? where are all whom we
knew in infancy? where are our dreams of childhood? Winged thoughts
still seem to flutter in the air, and that is all. People, caresses,
voices, all have gone and vanished. The cemetery has closed over them
all. There is a silent void. Were all those fine and sunny hours an
illusion? Was it only to weep one day over this negation that our
childish hearts were so tenderly attached to these fleeting shadows? Is
there nothing, down the long length of human history, but eternal
delusion?
It is here, above all, that we find ourselves in presence of the
greatest problems. Life is the goal, it is Life that produces the
conditions of Thought. Without Thought, where would be the Universe?
We feel that without life and thought, the Universe would be an empty
theater, and Astronomy itself, sublime science, a vain research. We feel
that this is the truth, veiled as yet to actual science, and that human
races kindred with our own exist there in the immensities of space. Yes,
we _feel_ that this is truth.
But we would fain go a little further in our knowledge of the universe,
and penetrate in some measure the secret of our destinies. We would know
if these distant and unknown Humanities are not attached to us by
mysterious cords, if our life, which will assuredly be extinguished at
some definite moment here below, will not be prolonged into the regions
of Eternity.
A moment ago we said that nothing is left of the body. Millions of
organisms have lived, there are no remains of them. Air, water, smoke,
dust. _Memento, homo, quia pulvis es et in pulverem revertebis._
Remember oh man! that dust thou art, and unto dust thou shalt return,
says the priest to the faithful, when he scatters the ashes on the day
after the carnival.
The body disappears entirely. It goes where the corpse of Cæsar went an
hour after the extinction of his pyre. Nor will there be more remains of
any of us. And the whole of Humanity, and the Earth itself, will also
disappear one day. Let no one talk of the Progress of Humanity as an
end! That would be too gross a decoy.
If the soul were also to disappear in smoke, what would be left of the
vital and intellectual organization of the world? Nothing.
On this hypothesis, _all_ would be reduced to _nothing_.
Our reason is not immense, our terrestrial faculties are sufficiently
limited, but this reason and these faculties suffice none the less to
make us feel the improbability, the absurdity, of this hypothesis, and
we reject it as incompatible with the sublime grandeur of the spectacle
of the universe.
Undoubtedly, Creation does not seem to concern itself with us. It
proceeds on its inexorable course without consulting our sensations.
With the poet we regret the implacable serenity of Nature, opposing the
irony of its smiling splendor to our mourning, our revolts, and our
despair.
Que peu de temps suffit pour changer toutes choses!
Nature au front serein, comme vous oubliez!
Et comme vous brisez dans vos métamorphoses
Les fils mystérieux où nos coeurs sont liés.
D'autres vont maintenant passer où nous passâmes;
Nous y sommes venus, d'autres vont y venir,
Et le songe qu'avaient ébauché nos deux âmes,
Ils le continueront sans pouvoir le finir.
Car personne ici-bas ne termine et n'acheve;
Les pires des humains sont comme les meilleurs;
Nous nous éveillons tous au même endroit du rêve:
Tout commence en ce monde et tout finit ailleurs.
Répondez, vallon pur, répondez, solitude!
O Nature, abritée en ce désert si beau,
Quand nous serons couchés tous deux, dans l'attitude
Que donne aux morts pensifs la forme du tombeau,
Est-ce que vous serez à ce point insensible,
De nous savoir perdus, morts avec nos amours,
Et de continuer votre fête paisible
Et de toujours sourire et de chanter toujours?[16]
_Note.--Free Translation._
How brief a time suffices for all things to change! Serene-fronted
Nature, too soon you will forget!... in your metamorphoses
ruthlessly snapping the cords that bind our hearts together!
Others will pass where we pass; we have arrived, and others will
arrive after us: the thought sketched out by our souls will be
pursued by theirs ... and they will not find the solution of it.
For no one here begins or finishes: the worst are as the best of
humans; we all awake at the same moment of the dream: we all begin
in this world, and end otherwhere.
Reply, sweet valley, reply, solitude; O Nature, sheltering in this
splendid desert, when we are both asleep, and cast by the tomb into
the attitude of pensive death.
Will you to the last verge be so insensible, that, knowing us lost,
and dead with our loves, you will pursue your cheerful feast, and
smile, and sing always?
Yes, mortals may say that when they are sleeping in the grave, spring
and summer will still smile and sing; husband and wife may ask
themselves if they will meet again some day, in another sphere; but do
we not _feel_ that our destinies can not be terminated here, and that
short of absolute and final nonentity for everything, they must be
renewed beyond, in that starry Heaven to which every dream has flown
instinctively since the first origins of Humanity?
As our planet is only a province of the Infinite Heavens, so our actual
existence is only a stage in Eternal Life. Astronomy, by giving us
wings, conducts us to the sanctuary of truth. The specter of death has
departed from our Heaven. The beams of every star shed a ray of hope
into our hearts. On each sphere Nature chants the pæan of Life Eternal.
THE END
INDEX
A
Aberration, 300
Adams, 168
Agnesi, Marie, 5
Alcar, 34
Aldebaran, 44, 66
Alexandria, 3
Algol, 39
Ancients, views of, 30
Andrew Ellicot, 195
Andromeda, 37, 38
Angles, 289
Antares, 45, 66, 70
Antipodes, 208
Arago, 275
Arcturus, 39, 66
Asteroids, 146, 195
Astronomie des Dames, 9
Attraction, 208
Aureole, 279
Autumn Constellations, 54
Axis, 225
B
Babylonian Tables, 30
Bartholomew Diaz, 176
Bear, Little, 35
Great, 32, 34, 35
Betelgeuse, 49, 66
Biela's Comet, 189, 198
Bode's law, 167
Bolides, 201
C
Cancer, 72
Capella, 38, 66
Cassiopeia, 36
Castor, 44, 68
Catalogue of Lalande, 65
Catharine of Alexandria, 3
Centaur, 52, 64, 65, 80
Ceres, 147
Chaldean pastors, 30
Chaldeans, 271
Chariot of David, 32
Charioteer, 38
Chart of Mars, 140
Châtelet, Marquise du, 4
Chiron, The Centaur, 30, 51
Chromosphere, 102
Clairaut, 3
Clerke, Agnes, 7
Cnidus, 31
Coggia's Comet, 187
Comet of Biela, 197
of 1811, 186
of 1858, 174
Comets, 111, 185
Constellations, 28
figures of, 31
Autumn, 54
Constellations, Spring, 52
Summer, 53
Winter, 51
Copernicus, 125
Corona Borealis, 40
Corona of the Sun, 104
Cygnus, 40
D
de Blocqueville, Madame, 5
de Breteuil, Gabrielle-Émilie, 4
de Charrière, Madame, 5
Deneb, 41
des Brosses, 5
Diaz, Bartholomew, 176
Dipper, 32, 34
Donati, 187
Double star, stellar dial of, 86
Double stars, 68, 70
Dragon, 36
du Châtelet, Marquise, 4
E
Eagle, 41
Earth, 205
ancient notions of, 19
distance from the sun, 215
how sustained, 21
inclination, 224
in space, 20
motion of, round the Sun, 222
movement of, 217
rotundity of, 206
viewed from Mars, 144
viewed from Mercury, 119
viewed from Venus, 130
weight, 210
Eclipse of Sun, May, 1900, 273
Eclipses, 259
Ellicot, Andrew, 195
Entretiens sur la Pluralité des mondes, 9
Equator, 225
Eudoxus, 31
Evening Star, 123
F
Faculæ, 98, 100
Fire-balls, 198
Flammarion's Lunar Ring, 253
Fleming, Mrs., 7
Fontenelle, 9
Foucault, 219
G
Galileo, 95, 98, 125, 244
Galle, 168
Globe, divisions of, 226
Great Bear, 32, 34, 35
Great Dog, 50
Grecian Calendar, 229
Greek alphabet, 33
H
Hall, Mr., 143
Halley, 181
Halley's Comet, 3, 175
Heavens, map of, 61
Hercules, 41, 66, 79
Herdsman, 39
Herschel, Caroline, 6
Hevelius, 246
Hipparchus, 31
Houses of the Sun, 43
Huggins, Lady, 8
Huyghens, 49
Hyades, 44
Hypatia, 3
J
Janssen, 102
Jupiter, 148
satellites, 155
telescopic aspect of, 150
K
Klumpke, Miss, 7
Kovalevsky, Sophie, 6
L
Lacaille, 292
Lalande, 3, 9, 65, 292
Latitudes, 226
Leonids, 195
Lepaute, Madame Hortense, 3, 4
Le Verrier, 167
Little Bear, 35
Little Dog, 50
Lockyer, 102
Longitudes, 226
Lucifer, 122
Lunar Apennines, 251
landscape, 254
topography, 252
Lyre, 40
M
Mars, 131
chart of, 140
Measurement, 289
Medes and Lydians, 266
Mercury, 114
Meteorites, 201
Meteors, 190, 191
Metonic Cycle, 271
Milky Way, 78, 87
Mira Ceti, 77
Mitchell, Maria, 7
Mizar, 34, 69
Moon, 232
diameter of, 242
distance of, 292
geological features of, 245
map of, 247
mountains of, 246
phases of, 241
photograph of, 240
revolution of, 234
rotation of, 242
size of, 242
temperature of, 250
total eclipse of, 263
N
Nebula, in Andromeda, 81
in Orion, 81
in the Greyhounds, 82
Neptune, 65, 166
revolution of, 169
Newton, 181
Nucleus, 95, 185
O
Orion, 48, 49, 81
P
Parallax, 292, 293
annual, 306
Pearl, 40
Pegasus, 38
Penumbra, 96
Periodic Comet, orbit of, 182
Perseids, 195
Perseus, 38, 70, 78
Phenician navigators, 30
Phoebus, 67
Photosphere, 101
Piazzi, 147
Planets, 109, 113, 146
distances, 110, 302
orbits of, 115
orbits of, 116
Pleiades, 38, 39, 44, 83
occultation of, 85
Pleione, 84
Polaris, 63
Pole-star, 34, 63
Poles, 225
Pollux, 44
Pope Calixtus, 176
Prodigies in the heavens, 178
Ptolemy, 31, 217
R
Radiant, 195
Riccioli, 246
Rigel, 49, 70
Roberts, Mrs. Isaac, 7
S
Saidak, 34
Saros, 271
Satellites, 110
Saturn, 156
revolution of, 157
satellites, 162, 165
volume, 158
Saturn's rings, 161
Scarpellini, Madame, 7
Scheiner, 95
Schiaparelli, 139
Secchi, Father, 7
Seven Oxen, 32
Sextuple star, 74
Shepherd's Star, 11
Shooting stars, 193, 194, 196
Sirius, 66, 309
_Solar storms_, 100
flames, 105
system, 65
Somerville, Mrs., 6
Spring constellations, 52
Stars, distances, 62
double, 68, 70
first magnitude, 57
number of, 60
quadruple, 73
second magnitude, 58
shooting, 193, 194
temporary, 77
Stars, triple, 72
variable, 75
weight of, 313
Star cluster in Hercules, 79
in the Centaur, 80
St. Catherine, 3
Summer constellations, 53
Sun, 88
houses of the, 43
measurement of distance, 297
photograph of, 96
rotation, 99
temperature of, 105
total eclipse of, 276
weight, 106
Sun and Earth, comparative sizes of, 93
Sun-spots, 95, 101
telescopic aspect of, 97
T
Temporary stars, 77, 78
Three Kings, 49
Total eclipse of the moon, 263
of sun, 276
Triangulation, 288
Triple Star, 72
U
Umbra, 95
Universe, 22, 23, 90
Urania, 8, 9
Uranoliths, 201, 204
Uranus, 162
V
Variable stars, 75
Vega, 40
Venus, 121, 296
phases of, 124
Vesper, 122
Victor Hugo, 24
W
Weighing worlds, 309
Winter constellations, 51
Z
Zodiac, constellations of, 46, 47
Zones, 225
FOOTNOTES:
[1] The French edition of this book is entitled Astronomy for
Women.--TRANSLATOR.
[2] 1 kilometer = 0.6214 mile; 100 kilometers may be taken as 62 miles.
1 kilogram is about 2.2 lb.; 5 kilograms = 11 lb.--TRANSLATOR.
[3] It is useful to know the letters of the Greek Alphabet. They are
easily learned, as follows:
[alpha] Alpha
[beta] Beta
[gamma] Gamma
[delta] Delta
[epsilon] Epsilon
[zeta] Zeta
[eta] Eta
[theta] Theta
[iota] Iota
[kappa] Kappa
[lambda] Lambda
[mu] Mu
[nu] Nu
[xi] Xi
[omicron] Omicron
[pi] Pi
[rho] Rho
[sigma] or [sigma] Sigma
[tau] Tau
[upsilon] Upsilon
[phi] Phi
[chi] Chi
[psi] Psi
[omega] Omega
[4] All the stars visible at any hour during the year can easily be
found with the help of the author's Planisphere mobile.
[5] Let it be remarked in passing that the stars might be much farther
off than they are, and invisible to our eyes; the Heavens would then
assume the aspect of an absolutely empty space, the moon and planets
alone remaining.
[6] 14" = 14 seconds of arc. One second of the circle is an exceedingly
minute quantity. It is 1 millimeter seen at a distance of 206 meters.
One millimeter seen at a distance of 20 m. 62 = 10 secs. These values
are invisible to the unaided eye.
[7] These fine double stars can be observed with the help of the
smallest telescope.
[8] For the explanation of the angular distances of degrees, minutes,
and seconds, see Chapter XI, on Methods of Measurement.
[9] The author has endeavored on the plates to represent the aspect of
the Earth in the starry sky of Mercury, Venus, and Mars; but in all
representations of this kind the stars are necessarily made too large.
By calculation the diameters of the Earth and Moon as seen from the
planets, and their distances, are as follows:
Diameter of Diameter of Distance
the Earth. the Moon. Earth-Moon.
Of Mercury (opposition) 20" 8" 871"
Of Venus (opposition) 64" 17" 1,928"
Of Mars (quadrature) 15" 4" 464"
Of Jupiter (quadrature) 3.5" 0.1" 105"
These aspects will be appreciated if we remember that the distance of
the components of [epsilon] Lyre = 207", that of Atlas in Pleione =
301", and that of the stars Mizar and Alcor = 708".
[10] A few evenings ago, after observing Venus in the calm and silent
Heavens at the close of day, my eyes fell upon a drawing sent me by my
friend Gustave Dore, which is included in the illustrations of his
wonderful edition of Dante's Divina Commedia. This drawing seems to be
in place here, and I offer my readers a poor reproduction of it, taken
from the fine engraving in the book. Dante and Virgil, in the peaceful
evening, are contemplating _lo bel pianeta ch'ad amar conforta_ (the
beautiful planet that incites to love).
[11] Strictly speaking, 1 kilometer = 0.6214 mile. Here, as throughout,
the equivalents are only given in round numbers.--TRANSLATOR.
[12] Translator: Compare the well-known English rhyme:
Thirty days hath September,
April, June, and November.
While all the rest have thirty-one,
Excepting February alone,
In which but twenty-eight appear
And twenty-nine when comes Leap Year.
[13] Fifty-eight different pictures of the aspect of the Moon to the
unaided eye will be found in the Monthly Bulletins of the Astronomical
Society of France, for the year 1900, in pursuance of an investigation
made by the author among the different members of the Society.
[14] My readers are charged not to speak of this property (which is
fairly extensive), lest the Budget Commission, at the end of its
resources, should be tempted to put on an unexpected tax. This ring,
which the astronomers presented to me in the year 1887, is almost in the
center of the lunar disk, to the north of Ptolemy and Herschel.
[15] "La fin du Monde." Flammarion, p. 186.
[16] Victor Hugo. _Tristesse d'Olympia._
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