DOCS.
313,
314 MARCH 1917
305
I
have
only
one
test particle
and
no
other
physical[8] masses (sun, etc.) [From
physics
I
know
only
that
I
must find
guv's
very
close to
those
of
the
old theor.
of rel. for finite
distances],
but
perhaps
I
am going
to
need
supernatural
masses,
which
I
assume
to be
static,
thus
T44
=
p,
all
other
Tij
=
0.
Then
the
equations
become:
(in
coordinate
system III)
From this
follows:
for
the
four-dimensional
system
both
cases:
Gii (^
~b
2
^“P)9n
0
i
=
1,
2,
3
Gu
-
(A
+
^np)g4i
=
-up
.
1
2
x+rp=w’
1
=
3
p
=
0
Therefore,
the
supernat.
masses
are
needed.
Supernat.
masses
do not exist.
I
am
curious
about
whether
you
can
agree
with this
approach
and
whether
you prefer
the
three-dimensional
or
four-dimensional system.
I
personally
much
prefer
the
four-dimensional system,
but
even more so
the
original theory,
without the
undeterminable
A,
which
is just
philosophically
and
not
physically desirable,
and with noninvariant
guv’s
at
infinity.
But if
A
is
only
small,
it makes
no
difference,
and
the
choice is
purely a
matter
of taste.
I
hope
that
your
health
has
improved[9]
and
you
will
soon
be back
to
normal
again.
With
cordial
greetings, yours truly,
W. de
Sitter.
314. To Moritz Schlick
[Berlin,]
21
March
1917
Esteemed
Colleague,
Upon rereading your
fine
essay
in
Naturwissenschaften
I
do find
another
small
inaccuracy.
I
am
informing
you
of
it
in
case
your
article
is reprinted elsewhere.[1]
The
derivation
of
the
law
of
the
motion
of
a
point provided
on
page
184
assumes
that,
seen
from
the
local coordinate
system,
the
point moves
in
a
straight
line.
Nothing
can
be derived from
this,
however.
The local coordinate
system
is
generally
of importance
only
at
the
infinitesimal
level,
and at
the
infinitesimal