The Anderson intelligencer. [volume] (Anderson Court House, S.C.) 1860-1914, 1895-07-17
THE DEPTHS OF SPACE.
A Popular Demonstration BY Sir Robert
Ball.
Robert s. Ball in NeaO York Sun.

such vast demands upon the powers Of
the human Imagination as the science
Of astronomy. We have to brace our
minds to the conception Of distances
and magnitudes so utterly transcend
ing all ordinary human experience,
that special means have to be invoked
to render them ineligible. Each ad-
vance in our knowledge Of the heavens
reveals to US the grandeur of the ce-
lestial spaces on an ever growing scale.
I propose to give in this paper some
Illustrations of what is known with re.
gard to the distances Of the stars, and
1 shall naturally take the opportunity
to make special use of certain recent
advances by which our knowledge OF
the subject has been greatly extended. !.
First, let me say that the task of find
ing the distance Of a star involves the
most delicate piece of measurement
that has ever been undertaken.
The great majority Of the stars are
situated at distances so enormous that
it is utterly hopeless to attempt to de-
termine how far away they are. In
fact, only comparatively few stars hap
pen to lie sufficiently close to the earth
to permit Of our making any accurate
determination Of their positions. Nor
is it by any means an easy task to
choose out those particular objects
which do lie within range. It not un-
frequently happens that after much
labor has been expended on observa-
tions Of some particular star, it has
been found that the work is fruitless,
and that the star is so remote that
there is no possibility Of learning what
it's distance actually amounts to.
Much care must, therefore, be taken to
make a judicious selection of the par
ticular star to which it is proposed to
devote so much time and labor. 1t
might naturally be supposed that the
brightest stars are those nearest the
earth ; and no doubt if all the stars
were intrinsically equally bright their
apparent brightness would be safe
guide in placing these objects at their
true relative distances. For in this
case the only explanation ofthe end
less varieties Of lustre which stars ex-
hibit would be that some Of them are
much nearer to US than others. But
there is no such simple connection be-
tween brightness and proximity as
this would imply. We know that the
very brightest star in the heavens is
Sirius, but we also know that Sirius
is by no means the nearest neighbor
of the solar system. Recentresearches
have also shown us that the famous
star Arcturus, the brightest member
of the constellation Bootes, and one
of the three orfour most brilliant stars
visible in our northern skies, is by no
means one of the stars comparatively
near rs. Arcturus has, in fact, been
recently shown to be SO excessively
far off that it must be classed with
those stars whose remoteness renders
it impossible for US ever to learn what
their distance actually amounts to.
There is, however, another indica-
tion of position which is very fre-
quently accepted by astronomers when
discussing whether star is likely to
lie within such degree Of proximity
to the earth as to make it worth their
while to try to determine its distance.
When we are looking at a steamer near
the horizon the vessel seems to change
it's place but slowly, though we may
know as matter Of fact that it is
travelling at the rate Of perhaps more
than ten miles an hour. The nearer
we are to the steamer the more rapidly
does it seem to move. In like manner
if a star were animated by what is
called proper motion, that is to say, if
the star shifted it's position on the sky
with reference to the other stars, and
if the amount of this shift was unusu-
ally great then there would be. pre-
sumption that the star was compare
lively near. twill, indeed, be obvious
that if all the stars were really travelling
at the same speed, those which lie
nearest the earth would move over an
appreciable part of the sky in shorter
time than those which were more re-
mote. OF course we are not entitled
to assume that the stars are moving
with equal rapidity in space. Indeed
we know we'll that such is not the case.
But, speaking generally, we may fair
ly argue that if a star does appear to
be moving rapidly, it is a presumption
that that body is one of the sun 8
nearer neighbors.
The star whose distance is to be
sought having been chosen, an elabo-
rate series Of observations has then
to be undertaken. The astronomer
measures in his telescope the sky in
terval by which that star is separated
from neighboring star which, though b
apparently close by, is in reality much
further away. Indeed, for this aux
iliary star we like, if possible, to have
an object which is about ten times as
far as the comparatively near star. It
is, however, essential that the two shall
lie so nearly in the same direction as
to be both visible in the same telescope
field. By means of delicate instru-
ment applied to the telescope we
measure the width of the bit of sky
between the two stars, and these
measurements are repeated night after
night for twelvemonth. This year s
series of observations is absolutely
necessary, for the astronomer is grad
ually shifting his own position, and in
six months time this shift will amount
to nearly 100000, 900, miles, the earth
having moved during this period round
to the opposite point Of its orbit. The
displacement of the observer alters the
position of the near star in relation to
its more distant companion. We thus
find that the sky interval between the
two objects changes periodically, and
from observations such as these it is
possible, by the magic Of mathematics,
to determine the distances of some of
the stars from the earth.
So far as astronomers have yet
learned, the star which lies closest to
the earth is one which we do not know
in the northern hemisphere, though
it is very familiar to residents in
Southern latitudes. This star is the
brightest gem in the constellation of
lt Il