DOC.
25
SOLVAY
DISCUSSION REMARKS
391
Doc.
25
Discussion Remarks
Following
Lectures
Delivered
at
First
Solvay
Congress
[30
October-3 November
1911]
III.
LORENTZ
Lorentz's lecture
(Lorentz 1912)
discusses several
ways
of
studying
the
applicability
of the
law
of the
equipartition
of
energy
to
heat
radiation,
one
of
which
is
related
to
the
work
by
Einstein and
Hopf
(see
Einstein
and
Hopf 1910b
[Doc.
8]).
Following
this
approach,
which
was
outlined
by
Einstein in
1909
(see
Einstein 1909b
[Vol. 2,
Doc.
56],
p.
190),
Lorentz
assumes a
frictionlike force
acting
on an
electron
moving
in
the
radiation
field,
and he inserts
the
velocity change
in
the
time
r
due
to
this force into
an expression
for
the
fluctuations
of
the
velocity
of the
electron
(see
Lorentz
1912,
pp. 35-39).
From his
expression
for these
fluctuations,
he
attempts
to
determine
the
mean energy
of
the
electron
but
obtains
unsatisfactory
results. Einstein's first
comment refers
to
an objection
raised
by
Planck
against
the
separability
of
oscillatory
and linear motion
assumed
by
Lorentz
(see
Lorentz
et
al.
1912,
pp. 46-47,
and Lorentz
et
al.
1914,
pp. 39-40),
and his second
comment refers
to two
alternative
proposals
to
Lorentz's
procedure, one suggested by
Planck in his discussion
remark,
the other
by Langevin (see
Lorentz
et
al.
1912, pp. 42-44,
and Lorentz
et
al.
1914, pp. 36-37).
Contrary
to Lorentz,
Planck and
Langevin
in
their
respective
comments
describe the motion
of the
electron
by means
of
ordinary
differential
equations
instead
of
an expression
for fluctuations.
No. 22
(Lorentz
et
al.
1914, p.
40;
Lorentz
et
al.
1912, p. 47)
The smaller the radiation
density,
the
more completely can
the
oscillatory
motion
of
the electron that
is
caused
by
the
momentary
influence
of the radiation
be
separated
from its
translational motion.
No.
25
(Lorentz
et
al.
1914,
p. 40;
Lorentz
et
al.
1912,
pp. 47-48).
The last
sentence
in
the
following
text
reads
in
the
published
version:
"For
this
reason
neither
the
consideration
of
Mr.
Langevin
nor
that
of
Mr.
Planck
solves the
problem,
in
my opinion."
The consideration differential
equation
neglects
those
terms
by
virtue of
which
the
mean
translational
motion
of
the
electron
(independent
of
the
momentary
radiation
field)
can change. Mathematically,
this manifests
itself
in
the
circumstance
that
an
additive
constant in
v
remains
undetermined.
For
this
reason
the consideration does
not solve
the
problem
in
my opinion.
IV.
PLANCK
In his lecture Planck examined various
ways
of
accounting
for
the
spectral
distribution
of
black-body
radiation.
In
one approach,
which
corresponds
to
his earlier derivation
of
his
formula for
black-body
radiation
by
methods
of
statistical
physics,
he determined
the
probability
of
a
given macroscopic state by counting
the
combinatorial
possibilities
for
realizing
this
state
in
terms
of
microscopic configurations (Boltzmann's "complexions"); see
Planck
1914, pp.
86-87.
In his first
comment
on
Planck's
lecture,
Einstein summarized
the
critique
of this
approach,
which
he
had earlier
presented
in Einstein 1909b
(Vol. 2,
Doc.
56), pp.
187-188. In line with his
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