The Roanoke times. [volume] (Roanoke, Va.) 1890-1895, 1894-04-12
HOW FAR is THE SUN
NEW LIGHT WHICH HAS BEEN THROWN
ON THE PROBLEM.


ty-five Million Miles, More or Less
A little now light has recently beer
thrown OH the problem of the distance
OF the sun. This is the great yardstick
of astronomy. For more than Il century
every effort has been made to ascertain
the distance us accurately as possible.
Methods direct and Indirect have been
employed. Considering the fact that the
knowledge thus sedulously pursued can
serve no unitarian purpose, the gencr-
Gus expenditure i'll the pursuit does
credit to the intellectual aspirations Of
the human race. From the time of Cap
tain Cooks expedition to the Society is
lands to observe tho transit of Venus in
1850 antil the present day millions of
dollars have been spent in this effort TO
drop a sounding line to the sun.
Coperncus believed that the sun was
not more than 5000 600 miles away
There were philosophers before the
Christian era who knew as much as
that. For several years past we have
been assured that the distance could not
be far from %, 500, 600 miles. But al
most century ago Laplacc assumed a
parallaX for the sun which gave almost
exactly that distance. Since his time
various astronomers have attacked the
problem, and their results have varied
from 81, 900, 900 to 90, 25O 900 miles,
the difference between these extreme cs-
Inmates being nearly as great as the en-
tire distance was believed to be by the
founders of astronomy.
Yet these facts carry no challenge to
the soundnoss of modern astronomical
methods or the substantial correctness of
the results attained by them. Tho dis
tance of the sun is not yet known with
absolute accuracy, for the same reason
that the height of Mount St. Elias or of
Mount Everest has not Yet been exactly
ascertaincd. But the limits of error are
known. and i'll the future we shall not
see estimates of the sun 5 distance vary
ing by millions of miles. If a series of
wires should be cut, each agreeing in
length With one of the recent measures
of the solar parallaN, and all should then
be stretched from the earth toward the
sun, every one of them would end in the
sun. though none might stop precisely
at its center
As TO the recent light upon this prob
lem, it is furnished by the results of OBJ
servations by the United States coast sur
vey at the Sandwich Islands To deter
mlnc tho constant of alteration Of the
stars. By this is meant the amount of
displacement that the stars undergo in
consequence Of the fact that we are look
ing ut them from il globe which i, not
standing still, but is moving i'll ~. orbit
around the sun at the rate of about ISL
miles III Il second. Light travels 1856,
$50 miles i'll Il second. The ratio Of the
velocity of the flying earth to That Of
light measures the displacement in the
position of the stars thar is called their
alteration. But, manifcsty, if we can
learn precisely how far the earth travels
in second, we shall know Just how
long its orbit is. We know that the earth
takes ono year, or, more exactly, ~, Dos,
$50 seconds, to 70 once around that or
bit. II, then we can iind out with rig
orous :. cUracy how far it goes in IL sec
ond, VIZ cal: at once calculate not ONLY
the length OF the orbit, hut The distance
OF the sun, which depends directly upon
the sig, of the orbit OF course allow.
ance l..uSt be made for the fact that the
orbit, instead of being a circle. is an
elipsc, and that consequently the cnrt!l's
rate OF travelling varies littlc. But
mathematics talk care of that.
Now, we have seen that the diSplacc-
mont, on alteration, of he stars fur
nishcs Il means of determining the ratio
of the carth' velocity III its orbit to the
known velocity of light. If that abclra-
ton Is accurately measured, ii must
give by Il simple calculation, the voloc.
ity of the earth and the distance Of the
sun. The alteration IL, ascMUimcd az