344
DOCS.
455,
456
JULY
1913
my
fundamental
hypotheses.[4]
The
corresponding generalization
of
the
relativity
theory
was
successful.-
Next semester
I
will
lecture
on
the
ordinary theory
of
electricity
and
probably
also
on relativity.[5]
This will
once
again
be
my
farewell semester.
Because
on
Easter
I leave
for Berlin
as an Academy-man[6]
without
any obligations,
like
a living
mummy
in
a
way.
I
am
very
happy
about
such
a
difficult career!
Besides,
last
year's
work
took
so
much
out
of
me
that
I
do
deserve
something.
456.
From Fritz Haber
Karlsbad Villa Victoria
[22
July 1913]
Dear
Mr. Einstein,
Thank
you
so
much
for
your
letter. The
thought
that
you
are
coming
to
Berlin
gives
me
constant
pleasure.[1]
Stern's
work
is
an
excellent achievement.[2] I
wanted
to write
you
a
letter,
but that
brings
me
to the
theory,
which makes
me
outright
sick. I
am
therefore
abandoning
the letter that
I
began &
writing
a
postcard.
This allows
room
for
only
one
question:
If
one
transforms[3]
hv
1
=
-
+
hv
T
9
hv
ekT-l
then
one
obtains[4]
Et
Eq
i
2
E0
2
E0
ekT~l
and
by
differentiating
after
a
suitable, simple,
further
transformation[5]
Er-E0
^
dE
~~kĨ~ "
dt
According
to
my
recollection,
this
formula
is
completely
analogous
to
your
formula
for
energy
fluctuation.[6]
But
you
have
already
demonstrated
that,
in the
absence of
zero-
point
energy,
the
energy
fluctuation itself attains
the value
ET.[7]
What
would it
take
to
2 2
prove
that
ET
-
E0
is
the
mean
square
value
that
you
denote
in
your
fluctuation
theory
by
e2
?
Is the
radiation
argument
actually necessary
for
that?
Cordially yours,
Haber