702
DOC.
662 DECEMBER
1918
plausible
that
IIdqkdpk
(ƒ-the
system’s degrees
of
freedom)
measures
the
a
priori-probability
of
the
phase
q
p.
The
a
priori-p[robability] means:
I
know
nothing
about the
motion
and
also do not know its
energy.
Liouville’s law
is
cited
here
unjustifiably,
however.
Now,
L’s
law
just
states
that
domains in
phase
space
that
are
transformed
into
one
another
by
motion have
the
same
probability
(carry
an
equal
amount
of
system
points).[2]
If
this
result
is
expanded
to
any
two domains of
the
same
size
in
phase space,
then the
law
is
extended in
a
way
that
leaves
nothing
of
the
original meaning.
This extension
is
what
is
specifically
needed,
though.
Let
us
take,
for
ex.,
Planck’s resonator.
L’s
law refers to two domains like
A
and
B.
They
are
completely unimpor-
tant to
me,
though,
because I combine
them within the
same elementary
do-
main R
anyway.
What
I
rather
need
are
two domains like
3
and
1. They
are never
transformed into each
other
by
motion,
however;
hence Liouville
says absolutely
nothing
about
them.
Thus
if
one
does not want
to
cheat,
one
can actually only say
the
following:
L’s
law tells
us
that certain
specifically
situated, equally large
domains in
phase space
have
the
same
probability.
This
statement is
extended without
any
compelling
reason
to
domains of
the
same
size
in
phase space regardless of
their
location. As
far
as
I
can see,
nobody
has
tried
to support
this
extension-probably
because it
is
groundless.
The
ergodic hypothesis
is of
absolutely no
use
for
this since it
just
relates
to
the
points
of
the
energy surface
in
the
phase space,
thus
on no
account
to
all
the
points
in
the
phase space.
Ehrenfest and
Gibbs[3]
tell
us
nothing
about
a
priori-probability
in
the above
sense.
And
yet
it
is
needed for
the
derivation of
the H theorem
as
well
as
for
the
explanation
of
quantum
theory.
For
the latter
it
would be
more
honest
to
leave Liouville out
entirely
and
to
proceed immediately
with the
elementary
domains R in
the
(q, p)
plane.
Do
you approve
of this? Or
is
there
anyone
who
can
dispel my
doubts?
So
much has been written
on
these
general
matters
that
one
would
think
they
had
been finished off
somewhere.
I
hear from
Kossel[4]
that
you
have confidence in
the
new
times
and
want to
participate. May
God
preserve your
faith![5] I
find
everything
contemptible
and
idiotic
beyond
words. Our enemies
are
the
greatest
liars and
scoundrels,
we
the
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