294 DOCS.
306,
307
MARCH
1917
people existed,
if
I
did not
see
them
before
me.
Now I
can
only hope
for salvation
from
an
external
force.
Affectionate
greetings
also
to
Anna and
Vero,
yours,
Albert.
307. From Friedrich Adler
Vienna
VIII,
1
Alser
St.,
9
March
1917
Dear
Professor
Einstein,
Now
that
I
have
plenty
of free
time at
my disposal,
I
have
taken
up
my
studies
on
the
foundations of
physics again,
which
I
had abandoned
7
years
ago.[1]
I
intended
to assemble in
a
book
my previously published
and
unpublished
papers
on
Mach
and
to
expand
on
them in various directions. The work had
already
progressed quite
far when
I
started
the
chapter
on
relativity.
Then
something
quite unexpected happened
to
me.
Ever since
taking
Mach’s
point
of
view
(1903)
I
also assumed
as a
matter of
course
the
relativity of
rotation and
already
advocated it in
1907
in
my
lecture
courses
in Zurich.[2] You
may
still remember
as
well
that around
1909
we
had
a
longer
argument
about it in
our
attic
rooms on
Mousson
Street.[3]
It
remained
vividly
in
my memory
because it
was very
important
to
me.
I
was
very
irritated,
you
see,
that
in
taking
the
centrifugal
effects
into
account, you rejected relativity
for
rotations.
I
asked
myself
at
the
time whether
an error
existed in Mach’s
or
my
argumentation
after
all.
But
I
could find
none.
So
much
the
greater
was
my
joy
when
your general
theory of relativity
came
out. I
did
not
have
the
time
to
follow
the
subject
closely,
however. It
is
only
now
that
I sent
for
the
more
recent
literature
in order
to
be able
to
present
Mach’s
position
on
relativity.
And
there
I
saw,
first in Freundlich’s
brochure,[4]
and
then
in
your
own
papers,[5]
that
you
have
accepted
Mach’s
position entirely, including
the
centrifugal phenomena.[6]
I
was
in
ecstasy
when
suddenly,
4 weeks
ago,
a
turning
point
came
in
my
considerations
which reveals
the
whole
problem differently
from
how I
had
seen
it
previously.
I
found,
first in
a more
recent discussion of Foucault’s
pendulum experiment,
and
then
generally,
a
criterion
that
you
and Mach do not take into
consideration,
or
at
least,
not
sufficiently,
which sheds
new light on
it
all. I
believe
I
have found
where
the
error
in
the
assumptions
not
only by
Mach
but
also
by you
lies. I
cannot discuss
this
in
detail
within
the
bounds of
a
letter,
but
just
want to
say
that,
naturally,
it does not involve
a
return
to “absolutes”
but
a
criterion of
a
relativistic
nature for
preferred
reference
systems.[7]
In
the last
7
years,
I
was
able to follow
the
course
of
the literature
only very
cursorily,
of
course,
and
now can
catch
up only
with
the
most important
papers.