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 role 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 _faculae_. 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 _faculae_ (_facula_, a little torch). These faculae, 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 deg.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.