510
DOCS.
488,
489
MARCH
1918
Hence,
it
is
only along
the
path
of successive
approximation
that
we can
seek
to
arrive at
an
“absolute coordinate
system.”
As
long
as we are
just
dealing
with
purely
terrestrial
observations,
we are
going
to
regard
the Earth
as
at
rest
in
the
universe
(but naturally, rotating
around
its
axis!).
The
coordinate
system
acquired
in
this
way
suffices
entirely
to
explain
the
observational
data.
As
soon
as
the
Sun
and, indeed,
all bodies of
our
planetary
system
are
drawn
into
our
consideration, however,
the Earth
must be
regarded
as
moving along
a
curved
orbit.
One
can
then
assume
the
planetary
system’s
center of
mass as
being
at rest
and thus obtain the
familiar coordinate
system
of Newton’s
theory
of
planetary
motion.
But
as soon as
the other
fixed
stars of
our
Milky Way
also affect
the
phenomena
(for
which,
as
far
as
I
know,
observational
precision
certainly
does
not
yet
suffice),
another
coordinate
system
would be reached in which
now
the
Sun also
is
in
orbit
and
the
common
center of
mass
of
the
entire fixed-star
system
is
at rest.
Whether
one
ought
to
stop
here
we
shall
never
be able
to
say and,
in
a
certain
way,
the coordinate
system
still remains behind
the ultimate
ideal
of
an
“absolute
system.”
Yet it
is
very
important,
nonetheless,
to
emphasize
again
and
again
that,
in
the last
analysis,
the
reason
for this
uncertainty
lies
only
in
the
limited
precision
of
our
observations. In
principle, though,
an
“absolute
coordinate
system”
must exist
but,
in
defining it,
it
is not
admissible
to
limit
oneself to
observations,
which
cover
only
a
very
restricted
region
of
the
world.
I
may
be
coming
to Berlin in
the
course
of next
week.
If
you
are
there
now,
I
shall
inform
you
in advance when
I
am coming
and when
I
might
be able
to visit
you,
in
the
hope
that
I
can
talk
to
you
then
for
an
hour
or
so.
With best
regards,
yours
truly,
Gustav
Mie.
489.
From Elisabeth
Warburg[1]
Charlottenburg, 21
March
1918
Esteemed
Professor,
How kind
of
you
to
want
to write to
my
son.
I
am so
very
worried
and
anxious,
you
know. Would
that
your
letter
still reached him in
good
health.
Living
hell
must
have
broken
loose
over
there.[2]
It
is
a
sin
against
human
beings,
an
outrage,
that
these
mass
murders
are
being
committed
on
and
on.
Do
we
have
a
right
to
this?
My
husband[3]
was always
so
overjoyed
with his
son.
He
once
told
me
in
confidence
that
he
was one
of
the
very greatest.
These
hopes
we
placed
in
him,
must all of
it
be
for
naught?
Is
he not
to fulfill
his
destiny?
I
fear he
is
too much