DOC.
23
PROPAGATION OF LIGHT
379
Doc.
23
On the Influence of Gravitation
on
the
Propagation
of
Light
by
A.
Einstein
[Annalen
der
Physik
35
(1911): 898-908]
In
a
paper published
three
years
ago,1
I
already
tried
to
answer
the
question
as
to
whether the
propagation
of
light
is
influenced
by gravitation.
I
now
return to this
topic
because
my
former
treatment
of the
subject
does
not
satisfy me, but, even more
importantly,
because
I have
now come
to
realize that
one
of the
most
important
consequences
of
that
analysis
is
accessible to
experimental
test.
In
particular,
it turns out
that,
according
to
the
theory
I
am going
to set forth,
rays
of
light passing near
the
sun
experience a
deflection
by
its
gravitational
field, so
that
a
fixed star
appearing
near
the
sun
displays
an apparent
increase of
its
angular
distance from
the
latter,
which amounts
to almost
one
second of
arc.
In the
course
of
carrying
through
the
analysis,
further results
regarding
gravitation
were
obtained.
However,
since
the
presentation
of
the
argument
in its
entirety
would
be
[2]
rather
difficult
to
follow,
I shall
present
in what follows
only a
few
quite elementary
considerations
on
the
basis
of
which
one
can
easily
orient
himself
regarding
the
assumptions
and the
line
of
reasoning
of the
theory.
Even if
their theoretical
basis
is
correct,
the
relationships
here derived
are
valid
only
in first
approximation.
§
1.
A
Hypothesis Concerning
the
Physical
Nature
of the
Gravitational Field
[3]
In
a homogeneous
gravitational
field
(acceleration
due
to
gravity,
y)
let there
be
a
coordinate
system
at rest
K,
which
is
oriented
in such
a
way
that the
lines
of
force
of
the
gravitational
field
run
in
the direction of the
negative
z-axis.
In
a space
free of
gravitational
fields,
let
there
be
another
coordinate
system
K' that
moves
with
a
uniform
acceleration
(acceleration y)
in
the direction of
its
positive
z-axis. So
as
not to
complicate
the
analysis unnecessarily,
we
will
disregard
the
theory
of
relativity
for the
time
being,
and
consider, instead,
the
two
systems according
to
conventional
kinematics,
and the motions
occurring
in
them
according
to
customary
mechanics.
Material
points
not
subjected
to
actions
of other
material
points
move
relative
to
K
as
well
as
relative
to
K'
according
to
the
equations
1
A.
Einstein,
Jahrb.
f.
Radioakt.
u.
Elektronik IV.4.
[1]