Yorkville enquirer. [volume] (Yorkville, S.C.) 1855-2006, 1909-04-27
DISTANCE OF THE STARS.
How Astronomers Set About the Task
of Measuring II.

of Measuring It.
With the exception of q hundred
stars at most, we know nothing of the
distances of the individual stars.
What is the cause Of this state OF
things? It is owing to the fact that
we have two eyes that we are enabled
not only to perceive the direction In
which external objects are situated,
but to get an idea Of their distance, to
localize them in space. But this pow
er Is rather limited. For distances ex-
ceeding some hundreds Of yards 1t ut
terly fails. The reason is that the dis
tance between the eyes as compared
with the distance to be evaluated be-
comes too small. instruments have
been devised by which the distance be-
tween the eyes is, as 1t were, artificially
increased. With good instrument of
this sort distances Of several miles
may be evaluated. For still greater
distance we may imagine each eye re-
placed by Photographic plate.
Even this would be quite sufficient for
one of the heavenly bodies-viZ., for
the moon.
At one and the same moment let q
photograph of the moon and the sur
rounding stars be taken both at the
Cape observatory and at the Royal OBJ
servatory at Greenwich. Placing the
two photographs side by side in the
stereoscope, we shall clearly see the
moon hanging in space" and may
evaluate its distance.
But for the sun and the nearest plan
cts, our next neighbors in the universe
after the moon, the difficulty recon-
mences.
The reason is that any available dis
tance on the earth, taken as eye dis
tance, is rather small for the purpose.
However, owing to incredible persev-
erance and skill Of several observers
and by substituting the most refined
measurement for stereoscopic examina-
ton, astronomers have succeeded In
overcoming the difficulty for the sun.
I think we may say that at present we
know its distance to within a thou
sandth part Of its amount. Knowing
the suns distances, We get that Of all
the planets by q we'll known relation
existing between the planetary dIe
tances.
But now for the fixed stars, which
must be hundreds Of thousands OF
times farther removed than the sun.
There evidently can be no question OF
any sufficient eye distance on our earth.
Meanwhile our success with the sun
has provided us with new one dis
tance, $4,000 times greater than any
possible eye distance on the earth,
for now that we know the distance at
which the earth travels in its orbit
around the sun we can take the diame-
ter of it's orbit as our eye distance.
Photographs taken at periods SIX
months apart will represent the stellar
world as seen from points the distance
between which is already best express
ed in the time it would take light to
traverse It, The time would be about
sixteen minutes.
However, even this distance, immense
as it is, is, on the whole inadequate for
obtaining a stereoscopic view OF the
stars. It Is only in quite exceptional
cases that photographs on large scale
that is, obtained by the aid Of big tele-
scopes-show any stereoscopic effect
for fixed stars. BY accurate measure
ment Of the photos We may perhaps get
somewhat beyond what we can attain
by simple stereoscopic inspection; but,
as we said a moment ago, astronomers
have not succeeded in this way in de-
termining the distance Of more than
hundred stars in all.-Scientific Amer
lean.