146
DOCS.
196,
197
DECEMBER 1909-JANUARY
1910
(connection
with the
dielectric
constant).
Shaye's
paper
on
the
electrodynamics
of
moving
dielectrics
is
also
nice,[5]
even
if not flawless.
I have
not
yet
arrived
at
a
solution
to
the
light
quanta question,
but
I have
found
quite
a
few
significant things
while
working
at it.
I'll
see
whether
I
might
not
yet
succeed
in
hatching
this
favorite
egg
of mine.
I
like
my
new
profession
very
much.
I
have
quite
an
intimate
relationship
with
my
students and
hope
that I'll
be able
to
stimulate
a
good many
of
them. I have
already
been
able
to
give suggestions
about doctoral
theses.
The director of
our
institute,
Prof.
Kleiner,[6]
is
a
very
kind
man.
He
treats
me as a
friend
and
never
reproaches
me
for
anything.
I
made the
acquaintance
of
several
people
in
Salzburg,
among
them
Planck, Wien,
Rubens, and Sommerfeld.[7]
I'm
completely
entranced
with the
latter.[8]
He
is
a
splendid
man.
Lastly,
I
wish
you a
Happy
New
Year and
success
in
whatever
you
undertake. With
cordial
greetings, your
A.
Einstein
Moussonstr.
12
Zurich
Greetings
from
wife
and
sonny.
197.
To
Arnold
Sommerfeld
Zurich, 19 January
1909
[1910][1]
Highly
esteemed
Prof. Sommerfeld:
It has
been
a long
time since
anything
in
physics
made
such
an
impression
on me as
that
paper
of
yours
on
the distribution
of the
energy
of
Roentgen
radiation
with
respect
to direction.[2]
The theoretical
argument leading to
the
correct
distribution of
the
fraction of the
Roentgen
radiation that
is
due
to
acceleration refers after
all to
a single
elementary
process.[3]
But
according
to
the
quantum conception,
the
elementary
emission
should,
in
essence,
be
directed,
so
that
I cannot
see
why
the
energy
distribution obtained
with the
quantum
structure would have to be the
very
same,
on average, as
that obtained
by
the current
theory.
After
all,
according
to the
quantum theory
one
must
assume
that
the
frequency
of
occurrence
of certain
emission
directions
determines the
observable
spatial
distribution of emitted
energy.
But,
as
I
see it,
this is not
yet
the
worst
difficulty;
what
disturbs
me
the
most is
the
following
consideration:
Suppose
the electron E
is
stopped at
the
wall
W.
Your
argument
seems
to show
quite
convincingly
that
the
effective
deceleration
is
really mainly
rectilinear,[4]
so
that