DOC.
42
SPECIAL
AND GENERAL RELATIVITY
391
The Experimental Confirmation of the
General
Theory
of
Relativity
151
tions of the fixed
stars;
but
up
to
the
present
the examination
of the available data does
not
allow
of
any
definite decision be-
ing
arrived
at,
as
to
whether
or not
these
displacements
are
to
be referred
in
reality to
the effect of
gravitation.
The
results of
observation have been collected
together,
and discussed
in
de-
tail
from
the
standpoint
of the
question
which
has
been
en-
gaging
our
attention
here, in
a
paper by
E.
Freundlich
entitled
"Zur
Prüfung
der
aligemeinen
Relativitäts-Theorie"
(Die
Naturwissenschaften,
1919,
No.
35, p.
520:
Julius Springer,
[101]
Berlin).
[100]
At all
events,
a
definite
decision will
be
reached
during
the
next
few
years.
If the
displacement
of
spectral
lines towards
the red
by
the
gravitational potential
does
not
exist,
then the
general theory
of
relativity
will
be untenable. On the other
hand,
if the
cause
of the
displacement
of
spectral
lines be
definitely
traced
to
the
gravitational potential,
then
the
study
of this
displacement
will
furnish
us
with
important
informa-
tion
as
to
the
mass
of the
heavenly
bodies.
Note.-The
displacement
of
spectral
lines towards the red end of the
spectrum
was
definitely
established
by
Adams
in
1924, by
observations
on
the dense
companion
of
Sirius,
for
which the effect
is
about
thirty
times
greater
than
for
the
sun.
R.
W.
L.