And now, my young friends, I am drawing near the close of that
course of lectures which has occupied us, I hope you will think
not unprofitably, for a portion of our Christmas holidays. We have
spoken of the sun and of the moon, of comets and of stars, and I have
frequently had occasion to allude to the relative position of our earth
in the universe. No doubt it is a noble globe which we inhabit, but I
have failed in my purpose if I have not shown you how insignificant
is this earth when compared with the vast extent of some of the other
bodies that abound in space. We have, however, been endowed with a
feeling of curiosity which makes us long to know of things beyond
the confines of our own earth. Astronomers can tell us a little, but
too often only a little. They will say--That is a star, and That is
a planet, and That is so big, and That so far; such is the meagre
style of information with which we often have to be content. The
astronomers who live on other worlds, if their faculties be in any
degree comparable with ours, must be similarly ignorant with regard to
this earth. Inhabitants of our fellow-planets can know hardly anything
more than that the earth on which we dwell is a globe 8000 miles
across, with many clouds around us. Some of the planets would not even
pay us the compliment of recognizing our existence; while from the
other systems--the countless other systems--of space we are absolutely
imperceptible and unknown.
Out of all the millions of bodies which we can see, you could very
nearly count on your fingers those from which our earth would be
visible. This reflection is calculated to show us how vast must be
the real extent of that universe around us. Here is our globe, with
its inhabitants, with its great continents, with its oceans, with its
empires, its kingdoms, with its arts, its commerce, its literature, its
sciences, and yet it would seem that all these things are absolutely
unknown to any inhabitants that may exist elsewhere. I do not think
that any reasonable person will doubt that there must be inhabitants
elsewhere. There are millions of globes, many of them more splendid
than ours. Surely it would be presumptuous to say that this is the
only one of all the bodies in the universe on the surface of which
life, with all that life involves, is manifested. You will rather think
that our globe is but one in the mighty fabric, and that other globes
may teem with interest just as ours does. We can, of course, make no
conjecture as to what the nature of the life may be elsewhere. Could
a traveller visit some other globes and bring back specimens of the
natural objects that he found there, no collections that the world has
ever seen could rival them in interest. When I go into the British
Natural History Museum and look around that marvellous collection,
it awakens in me a feeling of solemnity. I see there the remains of
mighty extinct animals which once roamed over this earth; also objects
which have been dredged from the bottom of the sea at a depth of some
miles; there I can examine crystals which have required incalculable
ages for their formation; and there I look at meteorites which have
travelled from the heavens above down on to the earth beneath. Such
sights, and the reflections they awaken, bring before us in an imposing
manner the phenomena of our earth, and the extent and interest of its
past history. Oliver Wendell Holmes said that the only way to see the
British Museum was to take lodgings close by when you were a boy, and
to stay in the Museum from nine to five every day until you were an old
man; then you would begin to have some notion of what this Institution
contains. Think what millions of British Museums would be required were
the universe to be adequately illustrated: one museum for the earth,
another for Mars, another for Venus--but it would be useless attempting
to enumerate them!
Most of us must be content with acquiring the merest shred of
information with regard even to our own earth. Perhaps a schoolboy
will think it fortunate that we are so ignorant with respect to the
celestial bodies. What an awful vista of lessons to be learned would
open before his view, if only we had a competent knowledge of the other
globes which surround us in space! I should like to illustrate the
extent of the universe by following this reflection a little further. I
shall just ask you to join with me in making a little calculation as to
the extent of the lessons you would have to learn if astronomers should
succeed in discovering some of the things they want to know.
Of course, all of us learn geography and history. We must know the
geography of the leading countries of the globe, and we must have some
knowledge of their inhabitants and of their government, their resources
and their civilization. It would seem shockingly ignorant not to know
something about China, or not to have some ideas on the subject of
India or Egypt. The discovery of the New World also involves matters
on which every boy and girl has to be instructed. Supposing we were
so far acquainted with the other globes scattered through space that
we were able to gain some adequate knowledge of their geography and
natural history, of the creatures that inhabit them, of their different
products and climates, then everybody would be anxious to learn those
particulars; and even when the novelty had worn off, it would still be
right for us to know something about countries perhaps more populous
than China, about nations more opulent than our own, about battles
mightier than Waterloo, about animals and plants far stranger than
any we have ever dreamt of. An outline of all such matters should, of
course, be learned, and as the amount of information would be rather
extensive, we will try to condense it as much as possible.
To aid us in realizing the full magnificence of that scheme in
the heavens of which we form a part, I shall venture to give an
illustration. Let us attempt to form some slight conception of the
number and of the bulk of the books which would be necessary for
conveying an adequate description of that marvellous universe of stars
which surround us. These stars being suns, and many of them being
brighter and larger than our own sun, it is but reasonable to presume
that they may be attended by planetary systems. I do not say that we
have any right to infer that such systems are like ours. It is not
improbable that many of the suns around us have a much poorer retinue
than that which dignifies our sun. On the other hand, it is just as
likely that many of these other suns may be the centres of systems
far more brilliant and interesting, with far greater diversity of
structure, with far more intensity and variety of life and intelligence
than are found in the system of which we form a part. It is only
reasonable for us to suppose that, as our earth is an average planet,
so our sun is an average star both in size and in the importance of its
attendants. We may take the number of stars in the sky at about one
hundred millions; and thus we see that the books which are to contain
a description of the entire universe--or rather, I should say, of the
entire universe that we see--must describe 100,000,000 times as much as
is contained in our single system. Of course, we know next to nothing
of what the books should contain; but we can form some conjecture of
the number of those books, and this is the notion to which I now ask
your attention.
So vast is the field of knowledge that has to be traversed, that we
should be obliged to compress our descriptions into the narrowest
compass. We begin with a description of our earth, for nearly all
the books in the libraries that exist at this moment are devoted to
subjects connected with this earth. They include various branches
of history, innumerable languages and literatures and religions,
everything relating to life on this globe, to its history in past
geological times, to its geography, to its politics, to every variety
of manufacture and agriculture, and all the innumerable matters which
concern our earth’s inhabitants, past and present. But this tremendous
body of knowledge must be much condensed before it would be small
enough to retire to its just position in the great celestial library. I
can only allow to the earth one volume of about 500 pages. Everything
that has to be said about our earth must be packed within this compass.
All terrestrial languages, histories, and sciences that cannot be
included between its covers can find no other place on our shelves. I
cannot spare any more room. Our celestial library will be big enough,
as you shall presently see. I am claiming a good deal for our earth
when I regard it as one of the most important bodies in the solar
system. Of course it is not the biggest--very far from it; but it seems
as if the big planets and the sun were not likely to be inhabited, so
that if we allow one other volume to the rest of the solar system, it
will perhaps be sufficient, though it must be admitted that Venus, of
which we know next to nothing, except that it is as large as the earth,
may also be quite as full of life and interest. Mars and Mercury are
also among the planets with possible inhabitants. We are, therefore,
restricting the importance of the solar system as much as possible,
perhaps even too much, by allowing it two. Within those two volumes
every conceivable thing about the entire solar system--sun, planets
(great and small), moons, comets, and meteors--must be included, or
else it would not be represented at all in the great celestial library.
We shall deal on similar principles with the other systems through
space. Each of the 100,000,000 stars will have two volumes allotted
to it. Within the two volumes devoted to each star we must compress
our description of the body itself and of the system which surrounds
it; the planets, their inhabitants, histories, arts, sciences, and all
other information. I am not, remember, discussing the contents, but
only the number of books we should have to read ere we could obtain
even the merest outline of the true magnificence of the heavens. Let
us try to form some estimate as to the kind of library that would be
required to accommodate 200,000,000 volumes. I suppose a long straight
hall, so lofty that there could be fifty shelves of books on each side.
As you enter you look on the right hand and on the left, and you see
it packed from floor to ceiling with volumes. We have arranged them
according to the constellations. All the shelves in one part contain
the volumes relating to the worlds in the Great Bear, while upon the
other side may repose ranks upon ranks of volumes relating to the
constellation of Orion.
I shall suppose that the volumes are each about an inch and a half
thick, and as there are fifty shelves on each side, you will easily
see that for each foot of its length the hall will accommodate 800
books. We can make a little calculation as to the length of this
library, which, as we walk down through it, stretches out before us
in a majestic corridor, with books, books everywhere. Let us continue
our stroll, and as we pass by we find the shelves on both sides packed
with their thousands of volumes; and we walk on and on, and still see
no end to the vista that ever opens before us. In fact, no building
that was ever yet constructed would hold this stupendous library. Let
the hall begin on the furthest outskirts of the west of London, carry
it through the heart of the city, and away to the utmost limits of
the east--not a half of the entire books could be accommodated. The
mighty corridor would have to be fifty miles long, and to be packed
from floor to ceiling with fifty shelves of books on each side, if it
is to contain even this very inadequate description of the contents
of the visible universe. Imagine the solemn feelings with which we
should enter such a library, could it be created by some miracle! As
we took down one of the volumes, with what mysterious awe should we
open it, and read therein of some vast world which eye had never
seen! There we might learn strange problems in philosophy, astonishing
developments in natural history; with what breathless interest we
should read of inhabitants of an organization utterly unknown to our
merely terrestrial experience! Notwithstanding the vast size of the
library, the description of each globe would have to be very scanty.
Thus, for instance, in the single book which referred to the earth I
suppose a little chapter might be spared to an island called England,
and possibly a page or so to its capital, London. Similarly meagre
would have to be the accounts of the other bodies in the universe; and
yet, for this most inadequate of abstracts, a library fifty miles long,
and lined closely with fifty shelves of books on each side, would be
required!
Methuselah lived, we are told, nine hundred and sixty-nine years; but
even if he had attained his thousandth birthday he would have had to
read about 300 of these books through every day of his life before he
accomplished the task of learning even the merest outline about the
contents of space.
If, indeed, we were to have a competent knowledge of all these other
globes, of all their countries, their geographies, their nations, their
climates, their plants, their animals, their sciences, languages, arts
and literatures, it is not a volume, or a score of volumes, that would
be required, but thousands of books would have to be devoted to the
description of each world alone, just as thousands of volumes have been
devoted to the affairs of this earth without exhausting the subjects
of interest it presents. Hundreds of thousands of libraries, each
as large as the British Museum, would not contain all that should be
written, were we to have anything like a detailed description of the
universe _which we see_. I specially emphasize the words just written,
and I do so because the grandest thought of all, and that thought
with which I conclude, brings before us the overwhelming extent of
the unseen universe. Our telescopes can, no doubt, carry our vision
to an immeasurable distance into the depths of space. But there are,
doubtless, stars beyond the reach of our mightiest telescopes. There
are stars so remote that they cannot record themselves on the most
sensitive of photographic plates.
On the blackboard I draw a little circle with a piece of chalk. I think
of our earth as the centre, and this circle will mark for us the limit
to which our greatest telescopes can sound. Every star which we see,
or which the photographic plate sees, lies within this circle; but,
are there no stars outside? It is true that we can never see them,
but it is impossible to believe that space is utterly void and empty
where it lies beyond the view of our telescopes. Are we to say that
inside this circle stars, worlds, nebulæ, and clusters are crowded, and
that outside there is nothing? Everything teaches us that this is not
so. We occasionally gain accession to our power by adding perhaps an
inch to the diameter of our object-glass, or by erecting a telescope
in an improved situation on a lofty mountain peak, or by procuring a
photographic plate of increased sensibility. It thus happens that we
are enabled to extend our vision a little further and to make this
circle a little larger, and thus to add a little more to the known
inside which has been won from the unknown outside. Whenever this is
done we invariably find that the new region thus conquered is also
densely filled with stars, with clusters, and with nebulæ; it is thus
unreasonable to doubt that the rest of space also contains untold
myriads of objects, even though they may never, by any conceivable
improvement in our instruments, be brought within the range of our
observation. Reflect that this circle is comparatively small with
respect to the space outside. It occupied but a small spot on this
blackboard, the blackboard itself occupies only a small part of the
end of the theatre, while the end of the theatre is an area very small
compared with that of London, of England, of the world, of the solar
system, of the actual distance of the stars. In a similar way the
region of space which is open to our inspection is an inconceivably
small portion of the entire extent of space. The unknown outside is
so much larger than the known inside, it is impossible to express the
proportion. I write down unity in this corner and a cipher after it
to make ten, and six ciphers again to make ten millions, and again,
six ciphers more to make ten billions; but I might write six more,
ay, I might cover the whole of this blackboard with ciphers, and even
then I should not have got a number big enough to express how greatly
the extent of the space we cannot see exceeds that of the space we
see. If, therefore, we admit the fact, which no reasonable person can
doubt, that this outside, this unknown, this unreachable and, to us,
invisible space does really contain worlds and systems as does this
small portion of space in which we happen to be placed--then, indeed,
we shall begin truly to comprehend the majesty of the universe. What
figures are to express the myriads of stars that should form a suitable
population for a space inconceivably greater than that which contains
100,000,000 stars? But our imagination will extend still further. It
brings before us these myriads of unseen stars with their associated
worlds, it leads us to think that these worlds may be full to the brim
with interests as great as those which exist on our world. When we
remember that, for an adequate description of the worlds which we can
see, one hundred thousand libraries, each greater than any library on
earth, would be utterly insufficient, what conception are we to form
when we now learn that even this would only amount to a description of
an inconceivably small fragment of the entire universe?
Let us conceive that omniscience granted to us an adequate revelation
of the ample glories of the heavens, both in that universe which we
do see and in that infinitely greater universe which we do not see.
Let a full inventory be made of all those innumerable worlds, with
descriptions of their features and accounts of their inhabitants and
their civilizations, their geology and their natural history, and all
the boundless points of interest of every kind which a world in the
sense in which we understand it does most naturally possess. Let those
things be written every one, then may we say that were this whole earth
of ours covered with vast buildings, lined from floor to ceiling with
book-shelves--were every one of these shelves stored full with volumes,
yet, even then this library would be inadequate to receive the books
that would be necessary to contain a description of the glories of the
sidereal heavens.