Sidelights on Astronomy and Kindred Fields of Popular Science | Page 5

near the zenith, in the autumn in the northwest. On the scale we have
laid down with the earth's orbit as a finger-ring, its distance would be
some eight or ten miles. The small stars around it in the same
constellation are probably ten, twenty, or fifty times as far.
Now, the greatest fact which modern science has brought to light is that
our whole solar system, including the sun, with all its planets, is on a
journey towards the constellation Lyra. During our whole lives, in all
probability during the whole of human history, we have been flying
unceasingly towards this beautiful constellation with a speed to which
no motion on earth can compare. The speed has recently been
determined with a fair degree of certainty, though not with entire
exactness; it is about ten miles a second, and therefore not far from
three hundred millions of miles a year. But whatever it may be, it is
unceasing and unchanging; for us mortals eternal. We are nearer the
constellation by five or six hundred miles every minute we live; we are
nearer to it now than we were ten years ago by thousands of millions of
miles, and every future generation of our race will be nearer than its
predecessor by thousands of millions of miles.
When, where, and how, if ever, did this journey begin--when, where,
and how, if ever, will it end? This is the greatest of the unsolved
problems of astronomy. An astronomer who should watch the heavens
for ten thousand years might gather some faint suggestion of an answer,
or he might not. All we can do is to seek for some hints by study and
comparison with other stars.
The stars are suns. To put it in another way, the sun is one of the stars,
and rather a small one at that. If the sun is moving in the way I have
described, may not the stars also be in motion, each on a journey of its
own through the wilderness of space? To this question astronomy gives
an affirmative answer. Most of the stars nearest to us are found to be in
motion, some faster than the sun, some more slowly, and the same is
doubtless true of all; only the century of accurate observations at our

disposal does not show the motion of the distant ones. A given motion
seems slower the more distant the moving body; we have to watch a
steamship on the horizon some little time to see that she moves at all.
Thus it is that the unsolved problem of the motion of our sun is only
one branch of a yet more stupendous one: What mean the motions of
the stars--how did they begin, and how, if ever, will they end? So far as
we can yet see, each star is going straight ahead on its own journey,
without regard to its neighbors, if other stars can be so called. Is each
describing some vast orbit which, though looking like a straight line
during the short period of our observation, will really be seen to curve
after ten thousand or a hundred thousand years, or will it go straight on
forever? If the laws of motion are true for all space and all time, as we
are forced to believe, then each moving star will go on in an unbending
line forever unless hindered by the attraction of other stars. If they go
on thus, they must, after countless years, scatter in all directions, so that
the inhabitants of each shall see only a black, starless sky.
Mathematical science can throw only a few glimmers of light on the
questions thus suggested. From what little we know of the masses,
distances, and numbers of the stars we see a possibility that the more
slow-moving ones may, in long ages, be stopped in their onward
courses or brought into orbits of some sort by the attraction of their
millions of fellows. But it is hard to admit even this possibility in the
case of the swift-moving ones. Attraction, varying as the inverse square
of the distance, diminishes so rapidly as the distance increases that, at
the distances which separate the stars, it is small indeed. We could not,
with the most delicate balance that science has yet invented, even show
the attraction of the greatest known star. So far as we know, the two
swiftest-moving stars are, first, Arcturus, and, second, one known in
astronomy as 1830 Groombridge, the latter so called because it was
first observed by the astronomer Groombridge, and is numbered 1830
in his catalogue of stars. If our determinations of the distances of these
bodies are to be relied on, the velocity of their motion cannot be much
less than two hundred miles a