DOCS.
439,
440
JANUARY
1918
447
Your
other
comments
are
just
as interesting
per
se
and
new
to
me.
I
am
not
so
bold
as
to
want to decide whether
they will
lead to
an
advance. In
any event,
I
wish
you
luck in
your
efforts!
With best
regards,
I
am
yours,
A.
Einstein.
440. To
Rudolf
Humm
[Berlin,]
5
Haberland
St.,
18 January 1918
Esteemed
Colleague,
You
are,
in
fact, entirely
correct.[1]
The
equations
(+)A¿#JI/
=
-k
m
dxu dxv
T
=
o----
ds ds
cannot be satisfied in
any
way.
The
equations
p(dx1/ds)2
=
...
=
p(dx4/ds)2
read
more
completely
as
(since
x4
=
it
must be
set
so
that
guv
=
-Suv
also for
m
=
n
=
4):
p(dx/dt)2/c2-v2
=
p(dy/dt)2/c2-v2
=
.
=
-p/c2-v2,
which cannot be satisified.
Changing
anything
in
the
energy
tensor
is out of
the
question.-
But
this
finding presents absolutely no
difficulty,
according
to
my conception
of
the
boundary
condition
problem.
The
supplementary
term
serves specifically
to allow
the
quasi-spherical
(or quasi-elliptic)
world to take
the
place
of
the
quasi-
Euclidean
one.
Thus
it
is
desirable
that the
equations
just
preclude any quasi-
Euclidean world.
I
presented
in
detail the
reasons
that
led
me
to this
interpretation
in
my
article
of
last
year.[2]
To
repeat,
I
only
note
that the
boundary
conditions for
a quasi-
Euclidean
world
(guv =
const. at
spatial
infinity) are
not
relative,
i.e.,
not
valid
