The sun. [volume] (New York [N.Y.]) 1833-1916, 1882-12-03
The Transit Of Venus.

The Transit Of Venus.
Thousands Of telescopes will be aimed at
the sun from almost every part OF the civil
lied world on next Wednesday, for on that
day tho planet Venus will be seen passing
across the facc OF the sun. This phenom-
enon, known as the transit Of Venus, is Of the
highest importance to astronomical science,
and astronomers have been preparing for
the observation Of 1t for q great many years,
and at great expense. 1t will be the last OPP
portunity any living astronomer will have
to witness a transit Of Venus, as the next
one occurs in the year 1904. There are four
transits in every 243 years, and they occur
in pairs, the two transits composing pair
being only eight years apart, but the pairs
being separated by more than a century. The
first OF the present pair OF transits occurred
in 1874. The last transits previous to that
were in 1861 and 1863. The next pair will oc-
cur In 1904 and 2O12.
The Importance OF transit Of Venus
is due to the fact that 1t furnishes one
OF the best methods known OF measuring the
distance OF tho earth from the sun. Some
readers, who have not given special atten-
ton to the subject, may be surprised to hear
that this distance is not accurately known
that there is, in fact, an uncertainty of about
half n million Of miles in the most careful
measurements that have been made Of it.
Tho school children OF twenty or thirty
years ago were taught that the distance be-
tween the earth and the sun was ninety-hve
million miles. But that estimate was aban-
doned years ago, and while astronomers
agree that it was too great, they do not agree
what the real distance probably is. The
later estimates vary from ninety-one to
ninety-threc million miles. Prof. YOUNG. in
his recent book on the sun, taking the mean
OF the most trustworthy measurements, esti
mates 1t at 92,8S5 600 miles. with limit Of
error Of about half million miles on either
side. The most learned and skilful astrono-
mers In the world will strive by means Of the
coming transit to reduce these limits Of
error, and to get as near the true distance as
possible
But, it may be asked, Of what use Is 1t to
spend SO much time and money in measuring
the distance between the sun and the earth ?
Because that distance Is the astronomers
yardstick, upon whose accuracy depend all
the other measurements he makes in tho
heavens. Unless we know what that dis
lance Is we cannot have Ineligible and &C.
curate information as to the dimensions Of
the solar system 1t is true that astronomers
know the comparative dimensions Of the sys-
TEN; that is to say, they can give an ac-
curate plan Of it on paper, showing each
planet at its true distance from the sum- as
compared with the distances Of the other
planets, but they cannot give the scale OF
Al -s- L.
number OF miles contained in some one Of
the distances shown in the plan; and the dis
lance which they naturally undertake to
measure in miles Is that between the earth
and the sun. The efforts Of astronomers to
obtain clear and accurate knowledge Of the
structure OF the solar system, and Of the
universe Of which that system is a
part, cannot be regarded with indiffer-
cnce by any Intelligent mind. We
see in tho heavens worlds resembling
our own world in many respects, composed
OF similar substances, moulded in the same
form, deriving light and heat from the same
source, and. like the earth, obeying tho
gravitHting force OF that same central sun.
But with many likenesses, we perceive also
many variations In this great family OF
worlds, which, together with the sun, COM
pose what Is called the solar system. In
some we behold the existence Of conditions
which we cannot but believe indicate that
they arc capable OF supporting, and probably
do support, Inhabitants Intelligent beings,
perhaps resembling ourselves. who, like
u.s. may be attempting to fathom the mys-
terics Of the universe. In other worlds, as
for instance the moon, we see planets which
are apparently dead, having passed through
the stage Of existence in which the earth at
present Is, and showing us what tho earth
may become at some future time. Other
planets appear not yet to have reached the
stage in which life Is possible upon their
surfaces and some, like Saturn with its rings,
present strange forms which, when viewed
with the telescope, are unending sources OF
wonder aud delight. The mind naturally
Graves knowledge in such a field as this. We
are as much interested in knowing all
that can be learned about the distances,
masses. and physical conditions OF these
other worlds, as we are in learning the
height OF our own mountains, the depth OF
our own seas, and all the things that are hid
den in the remote corners OF tho EARTH
Therefore the doings of the astronomers, who
will endeavor on Wednesday to increase the
accuracy Of our knowledge Of celestial dis
tances, must interest everybody who takes
any interest in the universe amid whose
wonders he lives.
Although the main object of observations
OF tho transit will be to obtain more accurate
knowledge Of the SUMS distance than we
now possess, there are some minor points Of
interest about it. 1t is possible, for instance,
that We may be able to increase our
knowledge Of the physical condition of Venus.
This planet Is one OF the most interesting in
the solar system, as it appears in some re-
spccts to resemble the earth more closely
than any other planet. 1t is apparently sup
piled with n copious atmosphere, and OBJ
servers Of previous transits have perceived
singular ring OF light surrounding tho
| planet when it is seen on the suns disk and
evidently caused by this atmosphere. Other
curousappcarancos have been noticed during
transits Of Venus, and by close observation
on tho present occasion astronomers may
be able to explain them. One OF the de-