48
DOCS.
40,
41 DECEMBER
1914
Greetings
from
me
to
the
children do not
seem
to
be
relayed,
otherwise
they
would have sent
their
regards
to
me
at least
once
in
this
long
period.
Thus it
is
actually
useless to
renew
the
same
every
time.
I
am going
to send
you
the
lace crocheted
by
Zora.[3]
By
the
way,
I don’t want
to be
bothered
with trifles
anymore.
Apart from
furnishing
one
bedroom
and
one
office
with the
bare
essentials,
I
have
kept
nothing.
41. To
Michael
Polányi
Berlin.
13
Wittelsbacher
St.,
13 December
1914
Highly
esteemed
Colleague,[1]
You
use
the
zigzag process
in
the
accompanying
illustra-
tion in order to make abso-
lute
zero
accessible to
thermo-
dynamic
examination.[2]
The
following
is
immediately
clear and
granted:
Were
the indicated
reversible
process
carried
on
ad
infinitum,
or
until absolute
zero
is
reached,
and if
the
finally
attained
entropy
value
is
denoted
as
Sl,
then
you
have
S'
-
Sl
=
(S
-
S1)
+
(S1
-
S2)......+
(Sl-1
-
Sl).
To conclude
more
now, you
need two
assumptions:
1)
S
-
Sl
is
finite.
2)
The
right-hand
side has
infinitely many components l
=
oo.
For
then
it
really
follows-as
has
to
be
proven-liml=00(Sl-1
-
Sl)
=
0.
Condition
(1)
will
undoubtedly
be conceded from
the
current state of
experience.
Condition
(2),
however,
is not
evident.
If,
for
ex.,
the
law of osmotic
pressure
remains valid
in
principle
down to absolute
zero-which
according
to
various studies
is not
at
all improbable-then
system
parameters
v
exist for which
the
execution
of
your
process
would
yield a
finite
l.[3]
But then
your proof
fails.
Your
tacitly
made
assumption
(2)
thus amounts to
a "petitio principii.”
With
all due
respect, yours truly,
A.
Einstein.
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