Evening star., 1932-07-10
BENT STARLIGHT
TEST SCHEDULED
Eclipse of Sun in February,
1884, May Prove Theory
of EinStein.
BY THOMAS r. HENRY.

A total eclipse of the sun, which
might have been planned to order for
an acid test of the Eanstein theory, is
predicted for February, 1884, by the
Naval Almanac Office.
1t is one Of the four solar and lunar
eclipses calculated for that year by
James Robertson, director of the al
manac Office. TIL shadow of the moon
will come between the sun and the
earth when the sun happens TO be sur
rounded by a great cluster Of stars.
There will be more than a hundred OF
them visible within two degrees OF the
sun.
1t Is just the situation astronomers
have been awaiting for years. one OF
the essential postulates of the Einstein
theory is that light follows curves in
space caused by the warping erect OF
great masses. Such an enormous body
as the sun is supposed to cause de-
preston in space. Light, when 1t enters
the area Of this depression, will not con-
ttnue in an absolutely straight line, but
will be DETECTED slightly along the
banks Of the space hollow"
DcHcCtlOn EAthCluCiy cuiAa'
But the detection is extremely small.
For the light from any individual star
it Is within the limits OF the possible
error of observation. Only when tne
path of the starlight passes very close
to the sun can it be detected at all. But
If the light from scores of stars at the
same time shows the same degree OF
bending relative to the distance OF the
paths from the sun, the probable error
can be eliminated by statistical means.
Thus the astronomers can tell with GER
tainty whether the bending effect is
reality or due merely to mistaken
observation.
Eclipses have an unfortunate tendency
to take place when the sun Is in some
region of the sky poorly provided with
nearby stars. The New England eclipse
this Summer will find only very few
stars sufficiently near the sun for the
bending effect to be observed. There
will not be enough Of them to eliminate
statistically the probable error.
The scientific validity OF the Einsteln
theory still rests largely on this bent
starlight" test. When DR.. Albert Elm
stein first promulgated the theory OF
relativity he predicted this objective
phenomenon might be observed at the
next total eclipse. 1t would not be pos
sible, he said, to explain it by the ac-
cepted laws of celestial mechanics,
while it would fit perfectly into his own
weird explanation of the nature of the
universe He even predicted the exact
amount of the bending. Nobody ever
had considered such phenomenon be-
fore Without some such objective test,
the theory of relatively was little more
than a curious mathematical exercise.
"ReIativity Eclipse"
1t was considered sufficiently i'm
portant for Great Britain to send out
an eclipse expedition during the war.
Then the bending effect was observed
for the first time, although not in the
exact amount EinStein had predicted.
There has been much dispute over the
validity of the observations, while
astronomers have awaited the perfect
"relativity eclipse"
The path of totality of this eclipse,
as calculated by Prof. Robertson, starts
over the Indian Ocean, east of Sumatra,
crosses Borneo, and then takes wide
swing northward across the Pacific. 1t
ends Just east of British Columbia.
Another popularity is that it crosses
the international time line, so that it
is dated on two days, February Is
and IA.
The observable effect of the bend
ing of light is to change the apparent
positions of the stars in the sky. The
method Of observation requires first
that photographs of the part of the
heavens affected be taken for several
nights before the eclipse. Then they
are photographed during the eclipse
itself, advantage being taken of the
short interval when the sun is darkened
and the stars appear in the sky. Then
the photographs are compared at
leisure. If there were no light bend
ing, the positions of the stars in both
sets should be approximately Identical.
Prof. Robertson predicts five other
eclipses during the next two years, all
invisible at Washington. Next year
will be poor eclipse year There will
be an annular eclipse Of the sun Feb
ruary "a, with path crossing Central
Argentina eastward and then swinging
northeastward across the Atlantic and
the African Continent to end over the
Red Sea. Another annular eclipse is
due on August q, 1853, with a path
passing over Persia, Northern India,
Borneo and Northern Australia.
For 1884, however, are predicted
three eclipses, in addition to the total
eclipse. There will be an annular
eclipse on August 10 with a path cross
ing South Africa and swinging far to-
ward the South Pole over the Antarctic.
wastes. Besides, there will be two partial
eclipSes Of the moon. The first, on
January 30, will be visible over most of
the Pacific, Australia, Asia, the Indian
ocean and Northwestern North Amer
lea. The second, on July 26, will be
visible along the Pacific coasts of North
and South America, Australia, the
Antarctic Ocean and the extreme east
ern part of Asia.