Evening star. [volume] (Washington, D.C.) 1854-1972, 1900-10-20

how far away the target is placed. Know
ing how far they are apart ana just now
much their rife barrels were inclined To-
ward each other. II would be an easy mat
ter for these men TO figure out the distance
of the target. Similarly, when two astron-
omerS, one at one side IF the EARN ana inc
other at the other, simultaneously aim their
telescopes at Eros. they can estimate now
far away that little world Is after they
have definitely determined how far apart
their instruments are and how they are m
clined toward each other. Happily, they
have means of estimating these two neces-
sary values. Similarly can a soitary
astronomer do the work. He can aim ms
telescope toward Eros just after sunset to-
night He obtains the direction in which
the instrument points as compared with
the positions of the stars around IT. Ihen
he can aim his telescope at the same planet
just before dawn tomorrow morning. Notlns
the new direction, as shown by the back
ground of stars, he also estimates now
many thousand miles the earth has carried
him since his first observation Thus does
his single telescope, moved around perhaps
1909 miles from where he first sighted his
celestial target, do the work of two tele-
scopes.
From as far north as Fulkora. Russia. to
as far south as the Cape of Good Hope, at
various observatories in the old world and
at thirty-five in America. this measur ng
work will continue throughout four months
According to Internal onll agreement the re-
suits will be combined in universal COM
pGtation of the distance TO Eros ana from
that calculation will he easily inquired the
distance of the sun. Series after series or
celestial photographs will, when measured
up. show the relation OF Eros to Its back
ground stars Eye measurements Will be
made with micrometers. which are oeilcaee
scales inside telescopes. and with helome-
tiers, which also are telescope instruments
for making delicate measurements oil dls-
lance.
Present Figures Wrong.
Aristarchus, a Greek astronomer of twen-
Cd 10
be about 4,s0o 900 miles away. His theory
Of measurement was correct, but his FOOLS
were bad. French astronomers of the sew
enteenth century concluded that If the APP
parent position Of Mars among the stars
could be carefully observed from two pc MS
on the earth, the distance of Mars and IN
directly, that of the sun could thus be de-
termined. Consequently an expedition was
sent to Cayenne, South America, to make
observation of Mars in 1872. Correspond
ing observation were made at PARIS. Ine
resulting computation showed the sun TO be
IS 600, 900 miles away. But there was diff
Guilty in determining Mars exact center
Our naval observatory obta NED It's iaS'
measurement of the suns distance in lSS2,
when Nenus-nearest of the planets eXcepi
Eros-crossed the suns face. But the glare
of the suns light and the ill-defined edge
of its rim, together with the atmosphere
of Venus which is twice as dense az our
own. combined to make the result OF doubt
full value The astronomers of the inStltu-
ton estimated from this work that the
SUMS average distance must be u 'b.?ot
miles, with a possible error of 6o,eD miles
Secretary Langley of the Smithsonian has
estimated that cannon ball would traNel
| this distance in about fifteen years. lie
| further calculated that a limited express
train, which had left the sun for the earth
| at the same time the Maytlower sailed with
the Pilgrim Fathers. from DelftshaVen, ana
which had kept up the modern rate OF speed
! dav and night would be due here somewhere
| about the present time. The fare at the
customary rate he figured a S2,'oouo Tor
| one person. Estimating the suns distance
| in terms of the speed at which sensation
| travels along our nerves. he SAYS that II the
| arm of child standing upon the earth were
| long enough to extend It finger to the sun
| the child would have to live until over a
| hundred wears cid before the pain could
| reach his brain and he realized thereby.
| Other astronomers have estimated mat II
| there were air to conduct a sound from inc
| sun to the earth an explosion upon the sun
| sufficiently loud to penetrate that distance
| would not be heard by us until fourteen
| wears after 1t had occurred. Such Is the
| great distance of the sun as last measured.
! Will the more accurate figures show ms
| vast SPACE to be greater or less? That Is
| the question. I'd
JOHN ELFRETH WATKINS. JR.