Yet, fixed as they seem, the stars are actually moving with a speed in
comparison with which, in some cases, the planets might almost be said
to stand fast in their tracks. Jupiter's speed in his orbit is about
eight miles per second, Neptune's is less than three and one-half
miles, and the earth's is about eighteen and one-half miles; while
there are ``fixed stars'' which move two hundred or three hundred
miles per second. They do not all, however, move with so great a
velocity, for some appear to travel no faster than the planets. But in
all cases, notwithstanding their real speed, long-continued and
exceedingly careful observations are required to demonstrate that they
are moving at all. No more overwhelming impression of the frightful
depths of space in which the stars are buried can be obtained than by
reflecting upon the fact that a star whose actual motion across the
line of sight amounts to two hundred miles per second does not change
its apparent place in the sky, in the course of a thousand years,
sufficiently to be noticed by the casual observer of the heavens!
There is one vast difference between the motions of the stars and
those of the planets to which attention should be at once called: the
planets, being under the control of a central force emanating from
their immediate master, the sun, all move in the same direction and in
orbits concentric about the sun; the stars, on the other hand, move in
every conceivable direction and have no apparent center of motion, for
all efforts to discover such a center have failed.
Pages:
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50