EINSTEIN ON THE FOUNDATIONS OF
STATISTICAL PHYSICS
I
Einstein wrote
only
three
papers
devoted
exclusively
to the foundations
of
statistical
phys-
ics: Einstein 1902b
(Doc. 3),
Einstein 1903
(Doc.
4),
and Einstein 1904
(Doc. 5).
Never-
theless,
these
papers
develop a
number
of
ideas that
play a prominent
role in
Einstein's
subsequent work;
and
they represent
the
beginning
of
a life-long
interest in the
foundations
of statistical
physics, an
interest
amply
demonstrated in other
publications;[1]
in
his
corre-
spondence
with, among others,
Michele
Besso,
Paul
Hertz,
Paul
Ehrenfest,
H. A. Lo-
rentz,
and
D.K.C.
MacDonald; in
the
design
of
instruments for the measurement
of
elec-
trical
fluctuations related to Brownian
motion;[2]
in his
university lectures;[3]
and
in
papers
and diaries
of
friends and
acquaintances.[4]
Einstein's
papers on
statistical
physics
start from within the
Maxwell-Boltzmann
tradi-
tion
in kinetic
theory.
His aim
was
to
fill
what he considered
a gap
in the mechanical
foundations
of
thermodynamics by deriving
the laws
of
thermal
equilibrium
and the
sec-
ond
law
of
thermodynamics
from the
most
general
possible
mechanical
assumptions
and
the
probability
calculus.
Although
there
was
very
little
contemporary response
to
his three
papers,[5]
and Einstein later
downplayed
their
significance,[6]
the harvest
of
results used in
his later work
is
considerable. These include: the derivation
of
an energy
fluctuation for-
mula that
presaged
Einstein's
work
on
Brownian motion and other fluctuation
phenom-
ena;[7]
the derivation
of
an expression
for the
entropy
that Einstein used
repeatedly
in his
[1]
See, e.g.,
Einstein
1910c,
1911h,
1915a,
1916a, 1916b, 1924, 1925a, 1925b;
Einstein
and
Hopf 1910a,
1910b.
[2]
See Einstein 1908a
(Doc. 48),
and the edi-
torial
notes,
"Einstein
on
Brownian Motion,"
pp.
221-222, and Vol.
5,
"Einstein's 'Ma-
schinchen'
for the Measurement
of
Small
Quan-
tities
of
Electricity."
[3]
Einstein lectured
on
statistical
physics
dur-
ing
the
summer
semester
of
1908,
University
of
Bern
(see
the Kreisschreiben
of
6
July
1908,
SzBeSa);
summer
semester
of
1910,
University
of
Zurich
(see
Zürich Verzeichnis
1910a,
p.
22);
summer
semester
of
1912,
German
University
of
Prague (see
Prag
Ordnung 1912a, p. 34);
summer
semester
of
1913,
ETH
(see
ETH
Pro-
gramm
1913a,
p. 14);
winter semester
of
1915/
1916,
University
of
Berlin
(see
Berlin
Ver-
zeichnis
1915b,
p.
48);
and winter semester of
1917/1918,
University
of
Berlin
(see
Berlin
Ver-
zeichnis
1917b, p.
44).
[4]
For
example,
Paul Ehrenfest recorded
in
his
diary
that when he met Einstein for
the first
time in
Prague
in
February 1912, they
immedi-
ately
started
to
discuss the
ergodic hypothesis
(Klein 1970,
p.
176).
And Karl F. Herzfeld
re-
ported
conversations with Einstein
concerning
his
objections to
a
derivation
of
the Boltzmann
principle
in
Herzfeld 1913,
p.
1553.
[5]
Einstein 1902b
(Doc. 3)
and Einstein 1903
(Doc. 4)
are
cited in Boltzmann and Nabl
1907,
p.
549. Martin Klein
(Klein 1970,
p.
46)
re-
ported
that the
young
Ehrenfest read
Einstein's
papers during a
visit
to
Leiden
in
the
spring
of
1903. Ehrenfest later cited Einstein 1902b
(Doc.
3)
and Einstein 1903
(Doc. 4)
in
Ehrenfest
and
Ehrenfest
1911,
pp.
6-7,
80. Einstein 1903
(Doc. 4) is
discussed
at
some length
in
Ornstein
1910 and Lorentz 1916. Paul Hertz
subjected
all
three
papers
to
a
careful
analysis
in
Hertz,
P.
1910a, and
they are
cited
frequently
in his other
papers on
the foundations
of
statistical mechan-
ics,
Hertz, P.
1910b, 1912, 1913a, 1913b,
as
well
as
in his
Repertorium
article, Hertz,
P.
1916.
[6]
See Einstein
1911c, p.
176.
[7]
See the editorial
note,
"Einstein
on
Brown-
ian Motion,"
pp.
206-222.
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