EINSTEIN ON
GRAVITATION
AND
RELATIVITY:
THE
COLLABORATION
WITH
MARCEL GROSSMANN
I
Einstein's collaboration
with
Marcel
Grossmann,[1]
which
probably began
in late
sum-
mer
1912
after Einstein's
return
from
Prague
to Zurich, led to two
joint papers:
Ein-
stein and Grossmann
1913
(Doc.
13)
and Einstein and Grossmann 1914b
(Vol. 6,
Doc.
2).
The
first
of these
was
published
before
the
end of June
1913,
the
second
almost
a
year
later, two
months after Einstein's
move
to
Berlin.
The
first
paper
is
modestly
entitled "Entwurf einer
verallgemeinerten
Relativitäts-
theorie und einer Theorie der Gravitation"
("Outline
[or Preliminary Version]
of
a
Generalized
Theory
of
Relativity
and of
a
Theory
of
Gravitation"),
but
it
actually
contains the
first
comprehensive theory
of
gravitation
that
according
to
Einstein also
generalized
the
principle
of
relativity
of classical mechanics
and
of Einstein's
paper
on
the
electrodynamics
of
moving
bodies,
Einstein 1905r
(Vol. 2,
Doc.
23).
Although
the "Entwurf"
theory
of Einstein and Grossmann later turned
out to
be
untenable, it
has
important
characteristics
in
common
with the
final
version of Einstein's
general
theory
of
relativity, published
more
than
two
years
later:[2]
The
gravitational
field is
represented
by a
metrical
tensor; the
mathematical
apparatus
of the
theory
is
based
on
the work of
Riemann, Christoffel, Ricci,
and Levi-Civita
on
differential
covariants;
and the action of
gravity on
other
physical processes
is
represented
by
generally
covar-
iant
equations.
The
major
difference
is
that
the
equations determining
the
gravitational
field in
the "Entwurf"
theory
are
not
generally
covariant.
The restricted covariance of the
theory posed
some
intricate
problems.
At
first it
was
only
certain that the
field
equations
were
covariant for linear coordinate
trans-
formations;
whether
any
other transformations,
for instance
to
accelerated frames of
reference,
were
allowed
was
unknown. Thus Einstein felt unable
to
announce
that the
theory incorporated
a
true
generalization
of the
principle
of
relativity
for uniform
motions.
Initially
Einstein
perceived
this feature
as
a major flaw,
but later
on
he found
two
arguments
that seemed
to
justify
the restricted covariance
and
even
suggested
that
a
meaningful generally
covariant
field
theory
of
gravitation
would be
physically
unac-
ceptable.[3]
In the
spring
of
1914
the
matter
seemed
to be
further clarified when Ein-
stein claimed that certain accelerated
frames of reference exist
in
which the
gravita-
tional
field
equations
of
the "Entwurf"
theory are
valid.[4]
This claim
was published
in
Einstein and Grossmann 1914b.
[1]Marcel Grossmann
(1878-1936) was
Professor of Mathematics
at
the ETH and
a
friend
of Einstein's since their student
days.
See Vol.
1,
Biography,
pp.
381-382.
[2]See
Einstein
1915e.
[3]For
a more
detailed
discussion of these
arguments
and of their
validity,
see sec.
III
below.
[4]See
Einstein
to
Michele
Besso,
ca.
10
March
1914
(Vol. 5,
Doc.
514).
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