DOC.
8
REPLY TO A COMMENT BY
M.
ABRAHAM
133
points moving
in
a
static
gravitational
field for both
cases.
However,
one
arrives
thereby
at
results
that contradict the
previously
mentioned
consequences
of the
principle
of
the
gravitational
mass
of
energy.
Thus,
it
seems
that the
gravitational
vector
cannot
be
incorporated
into the scheme of the
present theory
of
relativity
in
a
consistent
manner.
But in
my view,
this
state
of affairs does
not at
all
represent
the failure of the
method based
on
the
principle
of
relativity,
just
as
the
discovery
and
correct
interpretation
of Brownian motion does
not
lead
one
to
view
thermodynamics
and
hydromechanics
as
false doctrines. In
my opinion,
the
present theory
of
relativity
will
always
retain its
significance
as
the
simplest theory
for the
important limiting
case
of
spatio-temporal
events
in the
presence
of
a
constant
gravitational
potential.
It
must
be
a
task
of
the immediate
future
to create
a
relativity-theoretical
scheme in which
the
equivalence
of inertial and
gravitational
mass
finds
expression.
I
sought
to
make
a
first,
quite
modest contribution to the attainment of this
goal
in
my
papers on
the
static
gravitational
field. There
I
started from the
most
obvious
conception
that the
[11]
equivalence
of the inertial and
gravitational
mass
is to
be traced
to
the essential
identity
of
these
two
elementary qualities
of
matter and
energy
by
conceiving
the
static
gravitational
field
as
physically
identical with
an
acceleration of the reference
system.
I
have
to
admit that
I
was
able
to
carry through
this
conception
in
a
consistent
way only
for
infinitely
small
spaces,
and that
I
cannot
give
any satisfactory
reason
for that fact.
But I do
not
see
this
as
any
reason
to
reject
the
equivalence
[12]
principle
for the
infinitely
small
as
well;
no one
can
deny
that this
principle
is
a
natural
extrapolation
of
one
of the
most
general
empirical
laws
of
physics.
On the
other
hand,
the
equivalence principle opens up
for
us
the
interesting perspective
[13]
according
to
which the
equations
of
a
relativity theory
that would also include
gravitation may
also be invariant with
respect
to acceleration
(and rotation)
transformations. In
any
case,
the road
to
this
goal seems
to
be
a
quite
difficult
one.
One
can already
see
from
the
previously
treated,
highly specialized case
of
the
gravitation
of
rest masses,
that the
space-time
coordinates will
lose their
simple
physical
meaning,
and it is
not
yet possible
to
foretell the form that the
general
space-time
transformation
equations
can
have.
I
would like
to
ask
all
of
my
colleagues
to
have
a
try
at this
important problem!
And
now,
a
few
more
comments
on
Abraham's
note.
In
his
response,
Mr.
Abraham
says
about his
theory:
"There
can
be
no
talk
of
any
kind of
relativity, i.e.,
of
a correspondence
of
two
systems
that would be
expressed
in
equations relating
their
space-time parameters
x,
y,
z,
t and x',
y',
z',
t'."
I
do not wish
to venture
a [14]
judgment
about whether this
was
Abraham's
original assumption
or
not.
In
any
case,
the relativistic scheme that Abraham used
as a guide
in
his
theory
is
no longer
convincing
if the
principle
of
relativity
is
abandoned. Abraham also calls
my
attention
[15]