Sidelights on Astronomy and Kindred Fields of Popular Science | Page 6

second. They would make the circuit of
the earth every two or three minutes. A body massive enough to control
this motion would throw a large part of the universe into disorder. Thus
the problem where these stars came from and where they are going is

for us insoluble, and is all the more so from the fact that the swiftly
moving stars are moving in different directions and seem to have no
connection with each other or with any known star.
It must not be supposed that these enormous velocities seem so to us.
Not one of them, even the greatest, would be visible to the naked eye
until after years of watching. On our finger-ring scale, 1830
Groombridge would be some ten miles and Arcturus thirty or forty
miles away. Either of them would be moving only two or three feet in a
year. To the oldest Assyrian priests Lyra looked much as it does to us
to-day. Among the bright and well-known stars Arcturus has the most
rapid apparent motion, yet Job himself would not to-day see that its
position had changed, unless he had noted it with more exactness than
any astronomer of his time.
Another unsolved problem among the greatest which present
themselves to the astronomer is that of the size of the universe of stars.
We know that several thousand of these bodies are visible to the naked
eye; moderate telescopes show us millions; our giant telescopes of the
present time, when used as cameras to photograph the heavens, show a
number past count, perhaps one hundred millions. Are all these stars
only those few which happen to be near us in a universe extending out
without end, or do they form a collection of stars outside of which is
empty infinite space? In other words, has the universe a boundary?
Taken in its widest scope this question must always remain unanswered
by us mortals because, even if we should discover a boundary within
which all the stars and clusters we ever can know are contained, and
outside of which is empty space, still we could never prove that this
space is empty out to an infinite distance. Far outside of what we call
the universe might still exist other universes which we can never see.
It is a great encouragement to the astronomer that, although he cannot
yet set any exact boundary to this universe of ours, he is gathering faint
indications that it has a boundary, which his successors not many
generations hence may locate so that the astronomer shall include
creation itself within his mental grasp. It can be shown mathematically
that an infinitely extended system of stars would fill the heavens with a

blaze of light like that of the noonday sun. As no such effect is
produced, it may be concluded that the universe has a boundary. But
this does not enable us to locate the boundary, nor to say how many
stars may lie outside the farthest stretches of telescopic vision. Yet by
patient research we are slowly throwing light on these points and
reaching inferences which, not many years ago, would have seemed
forever beyond our powers.
Every one now knows that the Milky Way, that girdle of light which
spans the evening sky, is formed of clouds of stars too minute to be
seen by the unaided vision. It seems to form the base on which the
universe is built and to bind all the stars into a system. It comprises by
far the larger number of stars that the telescope has shown to exist.
Those we see with the naked eye are almost equally scattered over the
sky. But the number which the telescope shows us become more and
more condensed in the Milky Way as telescope power is increased. The
number of new stars brought out with our greatest power is vastly
greater in the Milky Way than in the rest of the sky, so that the former
contains a great majority of the stars. What is yet more curious,
spectroscopic research has shown that a particular kind of stars, those
formed of heated gas, are yet more condensed in the central circle of
this band; if they were visible to the naked eye, we should see them
encircling the heavens as a narrow girdle forming perhaps the base of
our whole system of stars. This arrangement of the gaseous or vaporous
stars is one of the most singular facts that modern research has brought
to light. It seems to show that these particular stars form a system of
their own; but how such a thing can be we are still unable to see.
The question of the form and extent of the Milky Way thus becomes
the central one of stellar astronomy. Sir William Herschel