DOCUMENT
245
JULY 1916 325
Letztere
richtig
herauskommen,
ist
bei
der
allgemeinen
Kovarianz
der
Gleichun-
gen
selbstverständlich,
sodass ein wirkliches
Durchrechnen keinerlei
Interesse
mehr hat. Dies Interesse
ist
nur
dann
vorhanden, wenn
man
nicht
weiss,
ob
Rotati-
ons-Transformationen
zu
den
"erlaubten“
gehören,
d.
h.
wenn man
sich
über
die
Transformationseigenschaften
der
Gleichungen
nicht
im Klaren
ist,
welches Stadi-
um gottlob endgültig
überwunden
ist.[7]
Sei mit Anna und Vero
herzlich
gegrüsst von
Deinem
Albert.
AKS
(SzGB).
EinsteinJBesso
1972,
22
(E.
17). [7
283].
The
postcard
is addressed “Herrn Michele
Besso
z.
Z. Kurhaus
Planalp
Brienz
Schweiz.,”
and
postmarked
“Berlin-Wilmersdorf
1
31.7.16.
2-
3N[achmittags].”
[1]A
letter that is not available but is mentioned in Doc. 237
as
written
on 16 July.
[2]Einstein had felt that Einstein-Maric’s deceitfulness
was
undermining
his
friendship
with
Besso
(see
Doc.
233).
[3]Einstein had addressed
Besso
in this fashion in
Doc. 238. The German edition
of
Tristram
Shandy
that
they
had
probably
consulted
is
Sterne 1910.
For
the characterization
of Uncle
Toby as
someone
with
“an
extraordinary
and
incomparable modesty
of
nature”
(“eine
ausserordentliche und
unvergleichliche Züchtigkeit
der
Natur”),
see
Sterne
1910,
vol.
1, p.
134.
[4]A
few
years earlier,
Besso
had
tried to solve the “Entwurf” field
equations
in first-order
approx-
imation
for
the
case
of
a
rotating
ring
to
see
whether the “Entwurf”
theory predicts a
contribution
of
Jupiter
to the
perihelion
motion
of
Mercury
and Mars
(see
Vol.
4,
Doc.
14,
[p.
50]
and
[p.
47]).
On
[pp.
36-37]
of
the
same document,
Einstein solved the “Entwurf” field
equations
in first-order
approximation
for the
closely
related
case
of
a rotating
hollow
sphere.
Besso did not contribute to this
calculation. For
a
treatment
of
the
case
of
a rotating
hollow
sphere
in the context
of
general relativity
in its final
form,
see
Thirring
1918
(see
also Einstein’s
correspondence
with Hans
Thirring
of
1917).
[5]This
same
iterative
approximation
procedure was
used
in Vol.
4,
Doc.
14.
For
a discussion, see
Vol. 4,
the editorial note “The Einstein-Besso
Manuscript on
the Motion
of
the
Perihelion of
Mer-
cury,” pp.
346-349.
[6]The
recipient
has
appended
the
following
note at the
foot of
the
recto: “Wie soll
das
gehen,
wo
die
Corioliskräfte
vom
Orte
unabhängig
sind?” The Coriolis forces
are given by spatial
derivatives
of
first-order
components
of
the
metric
field.
These
components
depend
on
the
spatial coordinates,
but
only linearly, so
that
the
Coriolis
forces
do not. Three months
later,
Einstein
explicitly
called
the
relevant
components
of
the metric
a
Coriolis field
(see
Doc.
270),
as
he
did
again
in August 1917
(see
Doc.
369).
[7]The
last
part
of this document
strongly suggests
that Einstein believed that the metric field inside
a rotating
ring can
be
replaced by
the metric field
of
a
Minkowski
space-time
in
rotating
coordinates.
Substituting
the latter metric into the
geodesic equation
and
setting
proper
time
equal
to coordinate
time,
one
arrives at the Newtonian
equations
of
motion in
a
rotating
frame. The terms
proportional
to
the
angular
velocity give
the Coriolis
force,
the terms
proportional
to the
square
of
the
angular
veloc-
ity,
the
centrifugal
force.
Starting
from
a
Minkowski
metric
in
a rotating
frame to first order in the
angular velocity
and
using
the iterative
approximation
procedure
outlined in this
document
to calculate the
second-order
terms,
Einstein
discovered,
in
September 1915,
that the Minkowski metric in
rotating
coordinates
is
not
a
solution
of
the “Entwurf” field
equations.
This
was one
of
the results
that
prompted
Einstein
to
abandon the “Entwurf”
theory (see
Doc.
123,
note
3,
for further
discussion).