The Unseen World and Other Essays | Page 8

and the heat into which this lost energy is
metamorphosed is poured out most prodigally in every direction. Let us
consider for a moment how little of it gets used in our system. The
earth's orbit is a nearly circular figure more than five hundred million
miles in circumference, while only eight thousand miles of this path are
at any one time occupied by the earth's mass. Through these eight
thousand miles the sun's radiated energy is doing work, but through the
remainder of the five hundred million it is idle and wasted. But the case
is far more striking when we reflect that it is not in the plane of the
earth's orbit only that the sun's radiance is being poured out. It is not an
affair of a circle, but of a sphere. In order to utilize all the solar rays, we
should need to have an immense number of earths arranged so as to
touch each other, forming a hollow sphere around the sun, with the
present radius of the earth's orbit. We may well believe Professor
Tyndall, therefore, when he tells us that all the solar radiance we
receive is less than a two-billionth part of what is sent flying through
the desert regions of space. Some of the immense residue of course hits
other planets stationed in the way of it, and is utilized upon their
surfaces; but the planets, all put together, stop so little of the total
quantity that our startling illustration is not materially altered by taking
them into the account. Now this two-billionth part of the solar radiance
poured out from moment to moment suffices to blow every wind, to
raise every cloud, to drive every engine, to build up the tissue of every
plant, to sustain the activity of every animal, including man, upon the
surface of our vast and stately globe. Considering the wondrous

richness and variety of the terrestrial life wrought out by the few
sunbeams which we catch in our career through space, we may well
pause overwhelmed and stupefied at the thought of the incalculable
possibilities of existence which are thrown away with the potent
actinism that darts unceasingly into the unfathomed abysms of
immensity. Where it goes to or what becomes of it, no one of us can
surmise.
Now when, in the remote future, our sun is reduced to vapour by the
impact of the several planets upon his surface, the resulting nebulous
mass must be a very insignificant affair compared with the nebulous
mass with which we started. In order to make a second nebula equal in
size and potential energy to the first one, all the energy of position at
first existing should have been retained in some form or other. But
nearly all of it has been lost, and only an insignificant fraction remains
with which to endow a new system. In order to reproduce, in future
ages, anything like that cosmical development which is now going on
in the solar system, aid must be sought from without. We must
endeavour to frame some valid hypothesis as to the relation of our solar
system to other systems.
Thus far our view has been confined to the career of a single star,--our
sun,--with the tiny, easily-cooling balls which it has cast off in the
course of its development. Thus far, too, our inferences have been very
secure, for we have been dealing with a circumscribed group of
phenomena, the beginning and end of which have been brought pretty
well within the compass of our imagination. It is quite another thing to
deal with the actual or probable career of the stars in general, inasmuch
as we do not even know how many stars there are, which form parts of
a common system, or what. are their precise dynamic relations to one
another. Nevertheless we have knowledge of a few facts which may
support some cautious inferences. All the stars which we can see are
undoubtedly bound together by relations of gravitation. No doubt our
sun attracts all the other stars within our ken, and is reciprocally
attracted by them. The stars, too, lie mostly in or around one great
plane, as is the case with the members of the solar system. Moreover,
the stars are shown by the spectroscope to consist of chemical elements

identical with those which are found in the solar system. Such facts as
these make it probable that the career of other stars, when adequately
inquired into, would be found to be like that of our own sun.
Observation daily enhances this probability, for our study of the
sidereal universe is continually showing us stars in all stages of
development. We find irregular nebulae, for example; we find spiral
and spheroidal nebulae; we find stars which have got beyond the