DOCS.
80,
81
MAY 1915 93
80. To
Tullio Levi-Civita
[Berlin,]
5 May
1915
Esteemed
and
dear
Colleague,
I also believe
that
we
have
given our subject as
full
a
treatment
as our
present
state
of
knowledge
of
the
same
allows.[1]
My proof
is
incomplete
to
the
extent
that it
is
not
proven
that
the
Auv's
can
be chosen
arbitrarily.
Your formulation
Cuv=
1/2guvAp-dp/dxdp/dxv
cannot solve
the
problem
in
the
sense
of
the
relativity
of motion. For if
p
is
constant for
one
coordinate
system,
then it
is
constant for all
the
others
as
well.
Consequently
none
of
the
arbitrarily
moving
coordinate
systems
would have
a
gravitational
field,
which
is
impossible.-
Now
I
thank
you
heartily
for
your
great patience
and add
the
wish
that
we
be able to make each other’s
personal acquaintance
soon
and in
better
times.[2]
With
cordial
greetings, very devotedly yours,
A.
Einstein.
81. To
Michael
Polányi
Berlin,
8 May
1915
Dear
Colleague,
Your
letter
to
me
of
February
25th indeed did
not
arrive. I
am
pleased
that
in
this
“great
era”
you
have
kept enough
leisure and inclination
to
deliberate
on
scientific affairs.
Your
letter
shows
me
that
we
have arrived
at
the
crux
of
the
matter. You
say:
“The existence of zero-adiabats
(and
also
isotherms)
follows
from
the
fact
that
the
system
must
be determined
from
the
dimension
figures
of
the
surroundings.”
However,
this
does not
seem
to
me
to
apply
to absolute
zero
in
particular.[1]