DOC.
453
FEBRUARY
1918
459
453. To Arnold Sommerfeld
[Berlin,]
1
February 1918
Dear
Sommerfeld,
Your warm-hearted
letter
pleased
me
very much,
even
though
my
illness
is
not
at all
so
troublesome
that
I
should deserve
so
much
sympathy.
It
is
an
antiquated
gastric ulcer,
thanks
to
my
neglect,
which
is
now
supposed
to be combatted with
prolonged
bed
rest.[1] I
thank
you
just
as
much for the kind
package consisting
of
that
now rare
material.
The
endeavor to master
dispersion
makes
sense
to
me
for
slow
waves,
the
indications
about the
rest
were
not clear to
me.[2]
It
is
striking
how much
can
be done
satisfactorily
with classical mechanics. If
only
it
were possible
to
clarify
somewhat
one
day
the
principal
ideas behind
quanta!
My
hope
of
witnessing
this
is
diminishing steadily, though.
At
the
end of
April
we are
holding
a
meeting
in honor
of
Planck’s 60th
birth-
day.
You would do
us
all
a
great
favor
if
you
were
willing
to
present
a
talk
at
this
occasion
on
the
development
of
radiation
and
quantum
theory during
the
special
session of
the
German
Phys.
Society.[3]
Nothing
more specific
has been
arranged
yet;
but
I
am
telling you
now
already
so
that
you
hear
of
it
as
early
as
possible.
No
one
here could do
it
nearly as
well
as
you;
and
I
think that
anything
that
would
please
Planck
ought
to be
done.[4]
Nothing
new can
be found from
general
relativity
anymore:
identity of
inertia
and
gravity.
The
metric
laws
behavior
of
matter
(geometry
&
kinematics)
are
is
determined
by
the interaction
of
the
bodies; independent
properties
of
“space”
do not exist.
With
this,
in
principle,
all
is
said.
I
am
also convinced
that
a
coherent
theory
without the
hypothesis
of
spatial
closure
is not
possible.[5]
How
the world
radius is determined
by
the
world
mass
can
be
seen
superficially
in
that[6]
k/c2
M/R=
number
(of
the
order of
1)
10-23
k nor[mal]
gravitational
constant
c
light velocity
M
world
mass
R
world
radius
Schlick’s
exposition
is masterful.[7]
This must
surely
be
an
inspired
teacher
there,
as
well.
It
is to
be
hoped
that
he does
not
remain
stranded
too
long
in
Rostock.-