following of planets and asteroïds, with the satellites of those
planets, with the comets which from time to time come sweeping on, to
fall into the burning furnace of the radiant star, all that, compared
with the universe, is no more than an ear of corn in a huge granary,
than a grain of sand upon the shore, than a drop of water in the ocean.
The terrible vastness of the universe is such that it is absolutely
inaccessible to our measurement, and it is for us the image of the
infinite, or the infinite itself. Now, my friend, attend to me. Most
certainly God, as to His nature, is absolutely inconceivable by our
minds. His essence escapes us, and always must escape us. We can
only affirm that He is infinite in His moral perfections, and in His
intellectual power. But if, on the one hand, God is _The Infinite_
in the moral order, and if, on the other hand, the universe is _The
Infinite_ in the physical order; if one is _The Infinite_ in spirit,
and the other is _The Infinite_ in extent, these two ideas, although
in themselves inaccessible to human intelligence, are nevertheless of
the same order, and may be regarded in contiguity. It is then possible,
without laying one's self open to the charge of presumption or
absurdity, to place the Infinite, which is called God, in the Infinite
which is called the Universe, in other words, to locate the person of
God at the common focus of the worlds which compose the Universe.
_Theophilus._ Your reasoning is just. But you must prove, or, if you
prefer the phrase, you must teach me that the universe is truly _The
Infinite_ by its extent. I could not admit that assertion without very
convincing evidence.
_The Author._ Very well. Lend me your best attention, and excuse me if
my demonstration resembles a lecture on astronomy. I have said that our
solar system is only a little corner of the universe. When you look at
the vault of the sky on a bright clear night, you see it thickly strewn
with stars, which, you will at once acknowledge, it would be impossible
to count. But all that you see with the naked eye is next to nothing.
Take a good telescope, and direct it to any part of the sky. There
where a moment before you saw nothing, you will now discern legions
of stars, bright spots will come out upon the darkness of space, like
diamonds upon the velvet lining of a casket, each of them a star,
exactly like those which we see at night in the sky. And now, let me
ask you, do you know what a star is?
_Theophilus._ Yes, I know from your manuscript, and I had already
known, that the stars which we see by night, but which the greater
light of the sun hides from us in the day-time, are self-luminous orbs,
each the centre of attraction and the lamp to the particular world it
lights, and which revolves around it. As a whole company of planets,
satellites, asteroïds, and comets revolve round our sun, receiving
heat, motion, and light from that great central orb, so, the stars
dispersed throughout space, communicate motion and activity to a vast
aggregate of planets and satellites. These planets, which revolve round
the stars, constitute _stellar worlds_, analogous to our solar world.
We cannot see the planets, which accompany these stars, by reason of
their smallness, and the prodigious distance between us and them,
beyond the reach of the most powerful telescopes; we only see the suns
which govern them, _i.e._, the stars. But the existence of the fixed
stars, like our sun, implies the existence of planets revolving around
them.
_The Author._ Perfectly correct. Thus, our solar world is not unique,
it is only one member of the family of stellar worlds, which resemble
our world in the disposition and the motions of the stars within them.
The universe is composed of the agglomeration of them all. You know
all this, but there is one fact which, as it is the result of recent
discoveries, you may not be aware of; it is, the great variety of
disposition or of physical aspect presented by certain stars, in which
a kind of overturn of that which constitutes nature on our globe has
taken place. While they remain similar to our world in the order of
their movements, certain stars differ widely in the forces which govern
nature in them.
_Theophilus._ Pray explain your meaning.
_The Author._ While our solar system is governed by a single central
star, there are stellar systems which are governed by two, three,
and even four suns. It is evident that worlds which have two or
three centres of light and heat must present physical and mechanical
peculiarities of which we have no idea. There are also other
differences proper to many of the stellar worlds. The light of our sun
and of the greater number of the stars is constant: it never undergoes
either augmentation or diminution. But this is not the case with
many of those distant suns which we call stars. We see their light
alternately fade and revive; sometimes they shine brightly, then become
almost imperceptible, and anon brilliant again. Some of them become
altogether extinct. The decrease in lustre of several stars has been
noted by different astronomers.[23]
Stars which have been observed in other times no longer exist.[24]
Others have suddenly appeared, shone with excessive lustre, and at the
end of some years have been seen no more.
These successive augmentations and diminutions of luminous brilliance
are not uncommon in the stars with which we are acquainted. According
to M. Flammarion,[25] star ο of the _Whale_ varies very much in
luminous intensity and the constellation itself frequently disappears.
Star χ of the _Swan_ passes from the fifth to the tenth size under
our eyes, the thirtieth star of the _Hydra_, which is of the fourth
size, almost always disappears at intervals of 500 days. These
variations must, as M. Flammarion observes, produce strange results.
To-day, the radiant star is shedding floods of light and fire upon the
planets which it governs, and the soul of that planet is warmed by
its burning rays. A few months later, without the least cloud in the
sky, the shining of the sun becomes fainter, and then, by degrees, the
obscurity increases, until at length the planet is plunged into thick
darkness. When the diminution of the light of the sun is periodical,
this universal night lasts for a fixed time, at the end of which the
light returns, if not, the darkness is dispersed after varying periods.
The light grows, little by little, until at length the radiant star
reappears in all its primitive brightness. The fine days, the glorious
light returns, until the moment when the same fading recommences and
the darkness sets in once more.
Can we picture to ourselves the strange alterations which nature
undergoes in regions which are subjected to torrid heat and glacial
cold by turns? I am convinced that the _glacial period_ which
geologists have defined in the history of our globe, during which an
extraordinary and sudden lowering of the temperature caused the death
of multitudes of living beings, and covered Europe with glaciers from
the mountains--was caused by a momentary weakening of the intensity
of the sun's light. When it resumed its ordinary brightness, the sun
dispersed the ice which had covered the earth with a death mantle.[26]
I have said that there are double stars, that is to say, worlds
illuminated by two suns, and sometimes even by three or four. It is a
strange fact that in almost every instance one of these suns is white,
like ours, but the second is coloured, blue, red, or green. In the
constellation _Perseus_ for example, a double star can be distinctly
seen by the aid of a good telescope. The star η is in fact accompanied
by a second, which makes part of the same solar system. Now, this
second star is blue. In the constellation _Ophiochus_ there is a
similar system of double stars, one of which is red and the other blue.
The same peculiarity exists in the constellation of the _Dragon_. In a
double star of the constellation of the _Bull_, there is a red sun, and
a blue sun. There are double solar systems red and blue; such are the
constellations _Hercules_ and _Cassiopœia_. Other double solar systems
are yellow and green, and sometimes yellow and blue. In all the worlds
which are illuminated by these coloured suns, the effect of light must
be very strange. No painter could represent them, and indeed we, who
know only the white light of our own sun, cannot form any idea of them.
_Theophilus._ These features of the stellar worlds are very
interesting, and I am glad to learn them. But are we not straying from
our subject?
_The Author._ No. After having made you understand that the solar
system which we inhabit is only a member of an immense family of other
solar worlds, only a small fraction of the universe, I wished to show
you by the diversity of those worlds, the facility with which nature
varies the forces and the physical conditions proper to the stellar
worlds, and consequently the living and inanimate types which make a
portion of these different stellar worlds. Now that you understand the
prodigious diversity of the solar worlds which compose the universe,
I will go on to our principal object. I have not lost sight of my
intention of proving to you that the universe has no limits, that in
its extent it is really the Infinite. I am now approaching this great
question. By the consideration of the stars, I am going to bring out
into relief the immeasurable vastness of the universe. Let me speak,
first, of the appalling distances which separate the stars from the
earth, and the figures will show you that on that side we fall into
the Infinite, and then I will speak of the numbers of the stars which
people space; and on this side also the abyss of the Infinite will yawn
before us. First, as to the distances which separate the stars from the
earth, from whence we may logically infer the distances which separate
these stars from one another. The distance between the earth and the
sun is 38,000,000 leagues, and this shall be our unit, our standard of
measurement, by which to estimate the distance of the stars.
I do not know, my dear Theophilus, whether you have formed an exact
idea of this extent of 38,000,000 leagues, which lie between us and
the sun. In general, we can only conceive prodigious distances such
as astronomy deals with, by representing them by the interval of time
which certain movable bodies known to us would consume in traversing
them. Let us then have recourse to comparisons of this kind. A
cannon-ball weighing 12 kilogrammes, exploded by 6 kilogrammes of
powder, proceeding at a uniform rate of 500 metres a second, would take
10 years to travel from the earth to the sun.
Supposing sound to travel at the same rate as on the surface of the
air, and at a uniform rate, it would take 15 years to accomplish this
journey. If a railway were laid through space between the earth and
the sun, a train travelling at express speed, 12½ leagues an hour,
would not arrive at its destination until the end of 338 years. This
imaginary train, if dispatched from the earth in January, 1872, would
arrive at the sun in the year 2210. The light from the sun, which
travels 77,000 leagues in a second, takes 7 minutes 13 seconds to reach
the earth.
_Theophilus._ The distance between the earth and the sun is, then,
38,000,000 miles--that is our unit of measurement for the distances of
the stars. Now let us hear about these distances.
_The Author._ I will deal first with those stars which are nearest to
us. One of these is a star in the constellation of the _Swan_. This
star is distant from the earth 551,000 times our unit of measurement,
that is to say, that we must multiply 551,000 times the distance of
the earth from the sun to represent the distance of the star which we
are considering, and yet it is one of the nearest to the earth. If we
wish to represent this distance by the time occupied in the transit of
light, supposing this light to travel, like that of our sun, 77,000
leagues a second, it would take 9½ years to travel from the star to us.
Now, if you wish to know the distance of other stars, and remember that
I only speak of the nearest, look at this table, which I found in an
astronomical treatise:
DISTANCE OF CERTAIN STARS FROM THE EARTH.
_Names of the _Distances from _Time of transit
Stars._ the Earth._ of light._
α Of the Swan 551,000 times 9 years and a half.
α Of the Lyre 1,330,700 21 years.
α Of the Great Dog 1,375,000 22 years.
α Of the Great Bear 1,550,800 25 years.
Polar Star 3,678,000 50 years.
Thus, the star α of the Lyre is distant from us more than 1,330,000
times as far as the earth is from the sun, and its light takes 21 years
to reach us. If, by any celestial catastrophe, star α of the Lyre were
to disappear, to be annihilated, we should still see it for 21 years,
as its light takes that time to reach us.
_Theophilus._ It is then possible that our astronomers are now
observing stars which no longer exist, and are only visible to us
because the light which they omitted is still travelling towards the
earth.
_The Author._ Just so. But to continue. I have begun with the stars
which are nearest to the earth. There are the stars of first and second
magnitude. You know, I suppose, the signification of those terms first,
second, and third magnitude in astronomy?
_Theophilus._ Yes, I know that the word magnitude is only applied to
the luminous appearance of the star, and not to its real bulk. A star
of the first magnitude is one which forms part of the group of the most
luminous stars; a star of the second magnitude is one which comes next
in point of brilliancy.
_The Author._ You must bear in mind that the word _magnitude_
signifies in astronomy the opposite of that which it expresses. The
more luminous a star appears to us, the nearer it is to us; the paler
and less visible, the farther it is away. The brilliance diminishes
in proportion as the figure increases. This is an introversion of
terms, sufficiently exceptional to be taken note of, and it ought
to be remembered, for fear of mistakes. Hitherto we have considered
only stars of the first and second magnitudes. Those of the third,
fourth, fifth, and sixth, lead us to the contemplation of such immense
distances, that the unit which we have adopted, enormous as it is,
is no longer of use. The instruments of celestial observation which
may be applied to the examination and measurement of stars of the
first and second magnitudes, do not serve for stars of the third and
following magnitudes, and, because the small visible diameter of those
stars make them appear mere specks of light, measuring instruments
are equally inapplicable to them. In estimating the distances of the
stars after the third magnitude, a method of comparison, based on the
amplifying power of the telescopes successively used, is employed. I
cannot enter into details of this method, which we owe to Sir William
Herschel, but must content myself with explaining its results, which
are as follows in the case of stars of the sixth magnitude. From
certain stars of that class, light would take 1042 years to reach us:
from others it would take 2700. After the sixth magnitude, the stars
can only be discerned by the aid of the telescope, and their distances
become perfectly stupefying in immensity. Certain of these telescopic
stars are so far from the earth, that their light can only reach us in
5000, and even 10,000 years after it leaves the luminous centre. From
the stars of the last category (fourteenth magnitude), light would take
100,000 years to reach the earth, supposing it to travel at the same
rate as the light of our sun, _i.e._, 77,000 leagues per second.
_Theophilus._ But, if we are to accept the results of the labours of
recent naturalists, man exists on the earth only within 100,000 years,
and some of those stars may have been extinct during all that time,
so that the human race may have been contemplating stars no longer
in being for 100,000 years. To what strange consequences does such a
science lead us!
_The Author._ Yes, the luminous rays which these stars send us from the
deepest depths of space may perhaps be emanations from solar systems no
longer in existence. The present shows us only the past. There may be
stars so profoundly lost in immensity, that their light has not yet had
time to reach us. They exist, but we cannot see them, not because the
telescope could not discover them, but because thousands of centuries
are required for the journey of their luminous rays to our earth,
and those thousands of centuries have not yet elapsed; so that this
grand spectacle is reserved, in that awfully remote future, for our
descendants.
And now, my friend, will you not acknowledge with me, that the
universe, considered merely by the distances which separate us from the
stars, and the stars from each other, is truly the Infinite?
_Theophilus._ Yes, it is the Infinite which unfolds itself before my
eyes. Let me breathe a moment.
_The Author._ If we contemplate the number of the stars, we shall also
have the perspective of the Infinite. It is easy to reckon those of the
first magnitude, _i.e._, the nearest to us. They are 20. Those of the
second magnitude are 65; of the third, 170. The number of the stars
increases as their visibility diminishes, in a very rapid proportion.
The number of stars of each class of visibility, in apparent magnitude,
is three times greater than that of the stars of the preceding class.
There are 500 stars of the fourth, 1500 of the fifth, 4500 of the sixth
magnitudes. The stars visible by the naked eye are 6000 in number.
A practised eye can succeed in counting the 6000 stars in the two
hemispheres.
[Illustration: Fig. 6.--A Corner of the Constellation of Gemini.]
But the telescope enables us to push the numbering of the suns much
farther: it opens up to us the depths of the heavens. Instead of the
small number of stars which our eyes can see, it shows us a myriad
of others, so thickly thronged together that they seem to cover the
sky with fine silver sand. Here, for instance (fig. 6), is the aspect
which one corner of the constellation of Gemini presents to the naked
eye. And here is the same portion of the sky seen by the telescope.
By the aid of this wonderful instrument stars of the thirteenth and
fourteenth magnitudes have been distinguished. The number of stars of
the twelfth magnitude is 9,556,000, which, joined to the number of the
same stars proper to the preceding categories, gives a total of more
than 14,000,000. In the third magnitude, a total number of 42,000,000
of stars is counted. Thus, reckoning those visible to the naked eye,
and by the telescope, we have 56,000,000 of suns, and we stop at this
number only because the telescope does not enable us to see smaller
stars than those of the fourteenth magnitude. But, let the telescope be
brought to greater perfection, and the whole region of the sky will be
seen to be covered with this silver sand, with this diamond dust, of
which each grain is a sun. And such will be the accumulation of these
suns, in the depths of space, that nothing will be seen on the field of
the telescope but a luminous network, formed by the agglomeration of
the suns, which will appear to touch each other.
[Illustration: Fig. 7.--A Corner of the Constellation of Gemini, seen
through the telescope.]
_Theophilus._ The Infinite is beginning again. Let me shut my eyes.
_The Author._ Wait, I have not said all, I have only begun. I am
coming to the nebulæ. Here, indeed, you may expect to grow giddy.
The telescope has dispersed all the theories on which the different
explanations of the nebulæ were built, and has shown us that they
are collections of stars, which, in consequence of their excessive
number, and their closeness to each other, appear to form a whole, a
single vague and continuous brightness. But, when their dimensions
and distances are amplified by the telescope, this diffused light
transforms itself into a brilliant point, analogous to that presented
by the sky, tapestried with small stars, in the same telescope. These
nebulæ are groups of enormous numbers of stars, and even their nearness
to each other is only in appearance. They are, in reality, separated by
enormous distances, and it must not be supposed that they are all in
the same plane; they belong, on the contrary, to very unequal depths in
space, and it is only an optical effect which gathers them together on
the field of the telescope in the same apparent plane.
The nebula of the _Centaur_ is one of the most wonderful. To the naked
eye it is but a dimly-lighted point in the sky; but, looked at through
a good telescope, it takes the aspect represented by figure 8.
[Illustration: Fig. 8.--The Nebula of the Centaur.]
On examination of this figure, it will be seen that a nebula is not
the result of a collection of stars simply spread out upon a level in
space, but of that of an assemblage of stars all placed at unequal
distances, and forming almost a sphere. In fact the stars are crowded
towards the centre, and are, on the contrary, more and more distant
from one another as the outer edge is approached. If a spherical
assemblage of stars were observed from a distance, it would present
a similar aspect. This leads us to believe that the nebula of the
_Centaur_, like the greater number of agglomerations of this kind, is
spherical.
Is it possible to reckon the stars which form a nebula? Only
approximately. Arago estimates the number of stars which form a nebula
no larger than the tenth part of the apparent disc of the moon, at
twenty thousand, at least. This result may give us an idea of the
swarms of suns contained in the nebulæ, for these stellar masses
are very numerous in the sky. In the depths of the nebulæ there are
luminous points whose nature is as yet unrevealed by the telescope,
which cannot be resolved into stars; but analogy leads us to believe
that they are other and still more distant nebulæ, which, by reason of
their apparent littleness, elude the scope of our instruments. But the
time will come, when, thanks to the perfection which our telescopes
shall have attained, this theory will be confirmed, and we shall thus
see deeper and farther into immensity.
The stars which form the nebulæ are sometimes grouped so as to form
regular shapes, spheres, or more or less lengthened ellipses. Sometimes
the sphere is hollow in the centre, and so forms a ring. Nothing more
varied, nothing more strange can be imagined than the forms of those
nebulæ which have hitherto been examined, and which already number more
than a million, of which no two are precisely alike. Certain nebulæ
seem to be double, or joined. Others are lengthened out, like serpents,
as in that of the _Shield of Sobieski_, represented in figure 9.
Lord Rosse was the first to discover that curious disposition of the
nebulæ called _spiral_.
Such a form is inexplicable, but it is certain that the suns which
compose the nebulæ are often grouped, not around a centre, not in
shapeless heaps, but in regular curves, on a system which seems to
reveal the existence of some mysterious force acting upon those stars,
which are distributed along lines representing spirals of different
diameter.
[Illustration: Fig. 9.--The Shield of Sobieski.]
In speaking of the stars, I have said that there are coloured stars or
suns. I will add here that nebulæ are observed coloured red, green, and
yellow, which is an additional proof that they are only agglomerations
of stars. That immense semi-luminous band which traverses the celestial
vault, girding it with a silver belt, is not, as it was long supposed
to be, a diffused quantity of luminous matter. The telescopic analysis
of the Milky Way shows that it consists of a long series of nebulæ.
The length of the Milky Way is from 700 to 800 times the distance from
Sirius to the sun, a distance which is 1,373,000 times that from the
earth to the sun.[27]
_Theophilus._ Can any idea be formed of the number of stars comprised
in the Milky Way?
[Illustration: Fig. 10.--The Milky Way.]