DOCUMENT 670 DECEMBER 1918
969
[12]That
this
expression
transforms
as a
covariant vector
for
constant
m can
be
seen directly
from
the alternative form
of
the
expression given
in Doc.
657, note
3.
If
m
is
not
a
constant,
there will be
an
additional
term (dm/ds)ui
=
(dm/dxi)ujui,
which also transforms
as a
covariant
vector.
[13]Einstein
had
argued
repeatedly
that
Weyl’s
theory runs
into difficulties
if
one
assumes,
as
Ein-
stein
thought one
should, first,
that clocks and rods
directly
measure
the line
element
ds2
(see,
for
instance,
Doc.
512), and, second,
that the
trajectories
of
free
uncharged particles are geodesics
(see,
for
instance,
Doc.
579).
If
one
makes the first
assumption
in
Weyl’s theory,
Einstein
argued,
the rate
of
a
clock will be
dependent
on
its
prehistory;
if
one
makes the
second,
uncharged particles
will be
affected
by
the
electromagnetic
four-vector
potential.
In Doc.
661,
Einstein reiterated both
charges.
Weyl’s
initial
response
to the first
charge can
be found in
Weyl
1918b,
pp.
478-480
(for a summary,
see
Doc. 526,
note
1).
In Doc.
619,
he offered the
new
suggestion
that clocks and rods
measure
Fds2,
where
F
is
the curvature scalar for the affine connection in his
theory.
In Doc.
626,
Einstein
wrote
that
the
problem
with this
suggestion
is
that
F
changes too
much from
point
to
point
in
space-time.
In
the
manuscript
sent with Doc.
657, Weyl introduced,
albeit in
a
different
context,
the
gauge
condition that
F
is
constant,
which in the revised
published
version
of
the
manuscript
is added to the notion that
clocks and rods
measure
Fds2
(Weyl
1919c,
p.
128).
In Doc.
661, however,
Einstein
expressed
doubts
about the
possibility
of
consistently imposing
this
particular
gauge
condition.
In
response
to
Einstein’s second
charge, Weyl
used the conservation laws
to
derive
an equation
of
motion
according
to
which free
uncharged particles
do
not
move on geodesics
in his
theory
(see
Doc. 657,
note
3,
for
an
outline
of
this
derivation).
In this
derivation, however,
essential
use
is made
of
the
gauge
condition
criticized
by
Einstein.
[14]The
manuscript was
written in the form
of
a
letter
to Einstein
(see
Doc.
657).
[15]The
revised version
was
received
by
the Annalen
der
Physik on
7 January
1919 and
was
published as
Weyl
1919c.
670.
From Heinrich Mousson
Zürich,
den
12.
Dezember 1918.
an
Herrn Prof.
Einstein,
Berlin. Haberlandstr.
5
Die
philosophische
Fakultät II der Universität Zürich
beantragt,
dass Ihnen noch
für
die
II.
Hälfte des laufenden Wintersemesters
an
unserer
Universität ein Lehr-
auftrag
erteilt werden möchte
aus
den
Gebieten
der
theoretischen
Physik
und
zwar
in der Form
von
zwölf
zweistündigen Vorlesungen,
die,
die nähere
Festsetzung
mit
dem Rektorat der Universität
Vorbehalten,
sich
auf
den Zeitraum
von
ca. 5
Wochen
verteilen.[1]
Hochschulkommission und
Erziehungsrat
begrüssen es,
wenn
auf
diese Weise
Ihre
geschätzte
Kraft wieder in den
Dienst
der Universität
gezogen
werden
kann,
und
geben
einer solchen
Anordnung
ihre
Zustimmung.
Wir
ersuchen
Sie, uns
wis-
sen
zu
lassen,
ob und
wenn
ja
unter welchen
Bedingungen
Sie
geneigt
sind,
einen
dahinzielenden
Auftrag
zu
übernehmen.
Ueber
die
Wiederholung
des
Auftrages
im
kommenden Sommersemester
bleiben
weitere
Vereinbarungen
Vorbehalten.[2]
Damit wir die erforderlichen
Anordnungen
noch
für das laufende Semester tref-
fen
können,
sind wir Ihnen
für
eine
baldige
Antwort
zu
besonderem Dank
ver-
pflichtet.
Der Direktor
des
Erziehungswesens:
Mousson