DOC.
13
GENERALIZED THEORY OF RELATIVITY
151
Doc.
13
Outline of
a
Generalized
Theory
of
Relativity
and of
a
Theory
of Gravitation
I.
Physical
Part
by
Albert Einstein
II. Mathematical Part
by
Marcel Grossmann
[Teubner,
Leipzig, 1913]
I
Physical
Part
The
theory expounded
in
what
follows derives from the conviction that the
proportionality
between the inertial and the
gravitational mass
of
bodies
is
an
exactly
valid law of
nature
that
must
already
find
expression
in
the
very
foundation of
theoretical
physics. I already sought
to
give expression
to
this conviction in several
earlier
papers by seeking
to
reduce the
gravitational
mass
to
the inertial
mass;1
this
endeavor led
me
to
the
hypothesis
that,
from
a
physical point
of
view,
an
(infinitesi-
mally
extended,
homogeneous) gravitational
field
can
be
completely replaced
by a
state
of acceleration of the reference
system.
This
hypothesis
can
be
expressed
pictorially
in
the
following
way:
An observer enclosed
in
a
box
can
in
no
way
decide
whether the box
is at rest
in
a
static
gravitational field,
or
whether
it is in
accelerated
motion,
maintained
by
forces
acting
on
the
box,
in
a
space
that
is
free of
gravitational
fields
(equivalence
hypothesis). [2]
We know the fact that the law of
proportionality
of inertial and
gravitational
mass
is
satisfied
to
an
extraordinary degree
of
accuracy
from the
fundamentally
important investigation
by
Eötvös,2
which
is
based
on
the
following argument.
A
body
at rest
on
the surface of the Earth
is
acted
upon
by
gravity
as
well
as
by
the
centrifugal
force
resulting
from Earth's rotation. The first of these forces
is
[1]
1A. Einstein,
Ann. d.
Phys.
35
(1911): 898;
38
(1912):355;
38
(1912):
443.
2B. Eötvös,
Mathematische und
naturwissenschaftliche
Berichte
aus
Ungarn
8 (1890);
Wiedemann's Beiblätter
15 (1891):
688.
[3]