DOCS.
564,
565
JUNE
1918 591
I have
had it
up
to
here with what’s
happening
in
the world otherwise. And
still
no
end is in
sight.
Cord[ial] regards
from
your
grateful
student,
Walter
Dällenbach.
Mr. Besso will be
writing you
in
the
next
day
or so
and in the
meantime sends
his cordial
greetings.
565. To
Walter Dällenbach
[Berlin,
after
15
June
1918][1]
Dear Mr.
Dällenbach,
It
was
very
nice of
you
to send
me an
excerpt
of
your
thesis.[2] I
especially
liked
your
fine
expression
for
polarization,
which
seems
to
be
new.
The
energy
tensor is
certainly
correct.
It
has
long
been known
that
the
values
I
had
derived
with
Laub at
the
time
are
wrong; Abraham,
in
particular,
was
the
one
who
presented
this
in
a
thorough
paper.[3]
The
correct strain
tensor has
incidentally
already
been
pointed
out
by
Minkowski.[4]
Its
asymmetry
arises from
the fact that
an
anisotropic quasi-elastically
bonded electron in
an
electrical
field
transmits
a
rotation
moment to
its molecule.
Hence,
Yz
#
Zy,
etc. must
be
true.
Weyl’s
theory
of
electricity
is
wonderful
as a
concept,
an
ingenious
theoret-
ical achievement.
However,
I
am
convinced
that
nature
is different.[5]
Two in-
finitesimal bodies
that
were once congruent always
remain
so, irrespective
of how
different
a
turn
their
fates
may
take. Thus if two
ds’s
lying
at
points
a
finite
distance
away
from each
other
are
measured
as
equal by
one measuring
rod,
or
by
one
measuring technique,
then
when
measured otherwise
they
are
again equal.
This
is
a
deeply
rooted attribute
of
our
world,
which
must
find
expression
in
the
general
foundations
of
physics.
According
to
Weyl’s conception,
it would have
to
be
expected
that
two
originally
identical
measuring
rods
(at space-time
point
P1)
are no longer
identical after
passing
through
different world lines
to
reunite
at
P2.
Their
difference would
correspond
to
the
value
for
the
difference of both
line
integrals[6]
I
pudxu
j
(pi/dsi/•
J
curve
1
J
curve
2
This difference
disappears,
in
general, only
when
there
is
no
electromagnetic
field
lying
between
the
world lines
of
both
bodies.
If,
for
inst.,
I
place
one
of
the
bodies
for
a longer
time T
in
a
metal
box
charged
to
the
potential
p
and leave
the other
one
outside,
then
at
the
end of time
T,
this difference has
the
value
QT,