DOC.
23
PROPAGATION OF LIGHT
387
According
to
equation
(4), a ray
of
light traveling
past
a
celestial
body
undergoes
a
deflection in
the direction of
decreasing gravitational
potential,
and
thus,
in
the direction
toward
the
celestial
body,
the
magnitude
of the deflection
being
a
=
$=+
i
j
kMcosö
-ds
=
2
kM
c2
A
#=-
where k denotes the
gravitation constant,
M the
mass
of
the celestial
body,
and
A
the
distance
of the
ray
of
light
from
the
center
of the
celestial
body. Accordingly, a
ray
of
light traveling
past
the
sun
would
undergo
a
deflection amounting
to
4•10-6
=
0.83 seconds of
arc.
This
is
the
amount
by
which
the
angular
distance
of
the
star from
the
cen-
ter
of the
sun
seems
to
be increased
owing
to
the
bending
of
the
ray.
Since
the
fixed stars in
the
portions
of
the
sky
that
are
adjacent
to
the
sun
become
visible
during
total
solar
eclipses,
it
is
possible
to
compare
this
consequence
of the
theory
with
experience.
In the
case
of the
planet Jupiter,
the
displacement to
be
expected
comes
to
about
1/100
of the
amount
indicated.
It
is
greatly
to
be
desired that
astronomers
take
up
the
question
broached
here,
even
if
the considerations here
presented
may
appear
insufficiently
substantiated
or even
adventurous.
Because
apart
from
any theory, we
must
ask ourselves
whether
an
influence
of
gravi-
tational
fields
on
the
propagation
of
light can
be detected
with
currently
available
instru-
ments.
Fig.
3.
[11]
[12]
Prague,
June
1911. (Received
on
21
June
1911)