282
DOCS.
294,
295 FEBRUARY
1917
294. To Paul
Ehrenfest
[Berlin,]
4 February
1917
Dear
Ehrenfest,
The
paper by
Mr.
Burgers delighted me.[1]
The
adiabatic method and the
Schwarzschild-Epstein
method
now
mutually
support
each
other.[2]
It
is
a
fine
success;
the
paper
is
also
very well
written.
I
have
perpetrated
something again
as
well
in
gravitation
theory,
which
exposes
me a
bit
to
the
danger
of
being
committed
to
a
madhouse.[3]
I
hope
there
are none over
there
in
Leyden,
so
that
I
can
visit
you again
safely.
It
is
a
pity
that
we
do
not live
on
Mars
and
just
observe man’s nasty antics
by
telescope.
Our
Lord
Jehova
no
longer
needs to
send down showers of ash and
brimstone;
he has modernized and has
set
this
mechanism to
run on
automatic.
Cordial
greetings, yours,
Einstein.
295. From Max Planck
Grunewald,
4 February
1917
Dear
Colleague,
Now
that
I
have
gained
a
bit
more
clarity
on
the
dynamic significance
of
the Jacobian
action
integrals,
I
would
like
to
report
on
it to
you.[1]
Let
E
be
the
energy
as a
function
of
the
coordinates
q1, q2,
...
and of the
momenta
p1, p2,
...;
and
if
we
set
in
this
function
dW
Pl
dqi
dW
(1)
the Hamilton-Jacobi
differential
equation
is then:
dW
dt
+
E
=
0.
The
same
is
satisfied
by
W
=
-a1\t +
V,
where
V is
a
function of
q1,
q2,
...
and
of
the
constants
a1, a2,
...,
among
which
the
first
a1
represents
the
value for
E.
Then
the
2n motion
equations are, first,
equations
(1);
second,
the
equations:
dW
da
i
dV
dai
=
ßu
dw
da2
=
-t
+
(2)