148
DOCS.
147,
148 NOVEMBER
1915
147. To
Michele Besso
[Berlin,
17 November
1915]
Dear
Michele,
Just
now
I received
your
letter.[1] I
am
coming,
and
am very
much
looking
forward to
it.
I
am enclosing
the
magnetism
paper.[2]
In these
last
months
I
had
great
success
in
my
work.
Generally
covariant
gravitation
equations.
Perihe-
lion motions
explained quantitatively.
The role of
gravitation
in the
structure of
matter.[3] You
will
be astonished.
I
worked
horrendously intensely;
it
is
strange
that
it
is
sustainable.
I
am
very
much
looking
forward to
our
reunion. Affection-
ate
greetings
to
you,
Papa,[4]
Anna,
Vero, yours,
Albert.
148. To David
Hilbert
[Berlin,
18
November
1915]
Dear
Colleague,
The
system you
furnish
agrees-as
far
as
I
can
see-exactly
with what
I
found in
the
last
few weeks
and have
presented
to
the
Academy.[1]
The
difficulty
was
not
in
finding
generally
covariant
equations
for
the
guv's;
for
this
is
easily
achieved
with the
aid of Riemann’s tensor.
Rather,
it
was
hard
to
recognize
that
these
equations
are a
generalization,
that
is,
a
simple
and
natural
generalization
of Newton’s
law.
It
has
just
been in
the last
few weeks
that
I succeeded in
this
(I
sent
you my
first
communication[2]),
whereas
3
years ago
with
my
friend
Grossmann
I
had
already
taken into consideration
the
only possible generally
covariant
equations,
which have
now
been shown
to
be
the
correct
ones.
We
had
only heavy-heartedly
distanced
ourselves from
it,
because it seemed to
me
that the
physical
discussion
yielded
an incongruency
with Newton’s
law.-[3]
The
important
thing
is
that the
difficulties have
now
been
overcome.
Today
I
am
presenting
to
the
Academy
a
paper
in which
I
derive
quantitatively
out of
general relativity,
without
any guiding hypothesis,
the
perihelion
motion of
Mercury
discovered
by
Le Verrier.[4] No gravitation theory
had achieved this
until
now.
Best
regards, yours,
Einstein.