DOCS.
552,
553
MAY-JUNE
1918 573
In
the
elliptic case,
this
formula reads:
t
-
R
arc6in
(
.
.
.-U.
..
. \\/:r2 +
y1
+
z2
-
v? +
K2
)1
And,
if
one
wants to remain with
the
elliptic assumption,
this
is
where
the
contradiction
occurs
that
I
wrote
you
about
lately:[12]
that
past
and
future
can-
not be
distinguished
from
one
another. For
+/Jx2
+
y2
+
z2
-
u2
+
R2
and
-/x2 ... -
u2
+
R2
are convex
in
the
elliptic space;
the
sign
of t
necessarily
remains undetermined.
On
the other
hand,
the
inconsistency disappears as
soon
as
the
mentioned
square
root is
“adjugated,”
i.e.,
simply
returning
from
the
elliptic
case
to
the
spherical case.
I
think,
therefore,
that
the
assumption of
statement
2b
can cer-
tainly be
taken into consideration
with
the
spherical
interpretation.-
With
this
I
would like to
close
today. My
entire
letter is
only supposed
to be
a more
precise
version
of
my
earlier communication
on
the
topic.
If
I
now
have
provided
certain
formulas
instead
of
geometric
considerations,
this
is
only
because
one can
be
more
explicit
with
their
aid; geometric
considerations nevertheless do
remain
the
source
of
the
entire
train
of thought.
I
do
not
know whether
you
will
find
anything
new
in
this
at all.
In
particular,
I
was
not
yet
able
to
compare
Weyl’s developments.[13]
With best
regards
and
wishing you
a
return
to
health, yours
most
sincerely,
Klein.
553. To Arnold Sommerfeld
[Wilmersdorf, Berlin,] (5
Haberland
St.)
1
June
1918
Dear
Sommerfeld,
Yesterday evening you were
elected Chairman
by
the
Directors
&
Advisory
Board
as
well
as
by
a
plenum
of
the
German
Physical
Society,[1]
and
with
visible
enthusiasm at
that.
In
the
interest
of
the
Society,
I
urge you
to
accept
the
nomination:
No
responsibilities,
so
to
speak,
will
arise from
this
for
you.
When
you
happen
to be in Berlin while
the
Society
is
meeting,
you
would
take
the
chair;
otherwise,
one
of
the Board members
residing
here
(Rubens
in
the
first
place)
would
substitute for
you.
Possible reservations
you
might
have
about
accepting
the nomination
may
be diminished
by
the
following.
We
all shared
the
view
that
a
non-Berliner
ought
to become
chairman.[2]
The
choice
first
fell
on