Evening star. [volume] (Washington, D.C.) 1854-1972, 1883-09-29


From the North American Review.
The universe of space il, in one sense. full and
| crowded. Everywhere our telescopes find stars,
and for every one We see there are probably hun.
| dreds, and even thousands, too faint or small OF
far away to reach our senses. And of this count
less host Of worlds not one at rest but oil are
rushing through space, free and unbridled, with
velocities far exceeding anything in the range OF
| our terrestrial experience. Our swiftest can
non shot ia kes more than three seconds to so ' J
| mile, but the stars and planets seldom move
slower than five miles seco nd and some OF
them go two hundred The veriest snail among
them would overhaul rifle ball in the same sort
| of way that the rifle ball would overtake a re-
ceding freight train. Is there not. then. dan
| ger Of collisions! Have such collisions ever
occurred and. if so, with what consequences?
CAN SPACE BE CROWDED.?
Now, in the first place, it Is only in sense.
and rather Pickwickian one, that space can be
called crowded. True, stars are to be seen In
every direction; but this is because our vision
reaches 80 unimaginably far If we restrict our
| consideration to bodies of respectable magni-
| tude-a hundred miles in diameter, for instance
| we ought rather to say that space. instead of
being crowded, is almost inconceivably empty
Between any star or planet and its nearest
nelghbor lie usually desolate distances of mill
ions. or even millions of millions of miles. we
assume, what is probably an underestimate that
the region commanded by our telescopes is so
| vast that light takes thousand years in coming
20 US rom Its outer Confines and, further,
| sand millions the number visible with
our largest telescopes is usually esti-
mated at about sixty mllions) then we find
that the average distance from star to star must
be about nine millions of millions of miles This
IA
sun to orr nearest stellar neighbor Ca Centauri).
according to the received value of its parallax:
| but it is distance which quite defies the power
| OF human comprehension. If two stars at such
distance were rushing straight toward each
| other with speed of ten miles a second. it
would require nearly thirty thousand years to
bring them together. Represent the sim as in
Sir John Herschels familiar illustration. by a
globe two feet in diameter SO that oranges.
cherries. peas, and pins heads would stand for
the different planets at distances ranging from
eighty feet to two miles, then, on that scale. a
Centauri would be eight thousand miles away.
Obviously. there Is plenty Of elbow room in the
universe, and the chance of two stars accident
any Jostling each other is far less than that of
the collision of two bullets in midar over bat
tlefeld. Still the possibility remains.
IS THERE IMMUNITY FROM COLLISION?
There is prevalent impression that the i'm
munity from collision between the heavenly
bodies depends mainly on their being held in
orderly orbits by central attraction: and it is
true that their orbital constraints make it quite
impossible for the planets to collide with each
other, or even to approach each other very
closely. But a very impressive picture is some
times drawn of what would happen If the earth.
for instance, should some time free herself
from the bonds of gravitation-how she would
fly of into space (Which Is true, of course). and
soon dash herself to pieces against some other
wandering world (Which is not true at all. or at
| least not probable). Most likely, If gravitation
were suddenly to cease, the earth would travel
four millions, not OF years, but Of ages, without
ever encOuntering anything more important
| than meteors, such as are now continually
| falling upon her surface. And these meteoric
encounters, even, would probably be far less
frequent than at present. since there is reason
to suppose that sEch bodies are much more
numerous in the DeighbOrhood of the sun, ana
OF other great sta1s, than in the rest of space
Evidently. however, the attractions between
wandering star and Others lying near it's path
must considerably increase the chances of COL
llslon, though not to 80 great an extent as per-
haps might be supposed. A body entering our
system at distance from the sun one hundred
times as great as the radius OF the earth's or
bit and moving with no more than the velocity
| natural to comet at that distance (about 2sS
miles per seCOnd), would not strike the snH
! unless it's path were directed within less than
half degree (23.4O otthe suns center; and fits
| velocity were greater. the aim would have to be
! still more accurate to score hit. If bodies
were shot into space at random from the posi-
ton and with the velocity indicated, only about
one in eighty-sx thousand would hit the sun.
| We're 1t not for the suns attraction, however.
| the proportion would be twenty thousand times
| smaller still-only one is seventeen hundred
millions.
| 1t is obvious. therefore, that encounters be-
| tween heavenly bodies Of considerable magni-
tude must be extremely rare. There is not in
all the astronomical record single certain in
staEce OF such an occurrence. And yet it may
confidently be asserted that some time or other
| In the past such events must have happened
| and some time in the future will happen again:
simply for the reason that. in a sufficient length
OF time, the most improbable things If only not
| Impossible, are sure to come to pass. Now, it
Is almost certain that the stellar motions are
not such as to render collisions impossible: the
planets, it is true, as has been said before. can
| never run into each other, because Of the size
| and nature of their orbits, but, so Tar as can
now De ascertained, nothing Of the sort holds
good Tor the motions of the stars. We already
proper motions" to be quite sure that as q
TACT, they are not travelling in any simple
| curves around any common center and also
tnat some stars are flying through space
with such velOcities that no attraction, such as
can reasonably be supposed to act in the prem
ises, can control them. Nor does theory. anv
| more Than observation, indicate structure Of
| the stellar universe at all analogous to that of
| the planetary system. Among the stars there
Is no central dominance and no imperial power,
| but we have to do with republic of COMPARE
lively free and independent members.
| COLLISIONS ARE INEvITABLE-THE EARTH WILL
BE HUGE BALL OF vAPOR, IF 1T IS HIT
Sir William Thompson is therefore fully justi-
fed In writing: ut isas sure that collisions must
occur between great masses moving through
space as it is that ships, steered without intei-
| gence to prevent collision, could not cross and
recross the Atlantic for thousands of years with
Immunity from collision" Undoubtedly the
chance OF an encounter between q pair of
| heavenly bodies selected at random is triaing.
almost beyond the power Of computation, and
the intervals OF time between such catastrophes
| IN that part of the heavens subject to human
observations must be on the average-enormous:
but yet. IN infinite time and unbounded space
somewhere or other now, some time or other
here-such things are happening, or will come
| to pass. y.
If ever two great worlds do really meet in
this way 1t Is possible to predict some of the
consequences: To use the technical language
OF science, their energy of molar motion will
| De converted into various forms Of molecular
ana potential energy" which, translated into
the vernacular, means that there will be evolu-
ton of heat and light, while at the same time
the soiids present will be wholly or in part Ilque