392
DOC.
25
SOLVAY
DISCUSSION REMARKS
earlier
analysis
and in
contrast to Einstein,
Planck
applied
the
quantum hypothesis as
well
as
statistical methods
only
to matter
that
interacts with radiation and
not
directly
to
radiation itself. In
the
discussion this
controversial
point
was
first taken
up by Jeans,
and
subsequently
commented
upon by
Einstein in his second
remark,
referring
to
Lorentz's
analysis
of radiation
(Lorentz 1912).
In his
lecture,
Planck also
presented
his
second attempt
at a theory explaining
the
black-body
radiation formula
(for a
historical
discussion, see
Kuhn
1978, pp. 235ff). According
to
Planck's "second
theory,"
the
quantum hypothesis plays a
role
only
for
the
emission of
radiation,
while Maxwell's
equations
are supposed
to
be valid for
absorption as
well
as
for radiation
in matter-free
space.
In his last remark
during
the
discussion,
Einstein
argues
that it
is
not
possible
to
introduce
any
form of the
quantum hypothesis
for
the
emission
by an oscillator,
but
he
upholds
classical
electrodynamics
in
the
space surrounding
it. His reference
to
Planck's
original theory
is
probably a
reference
to Planck's
attempts
at
an analysis
of
black-body
radiation
prior
to
the
introduction
of
the
quantum hypothesis
(see
Planck
1900a).
No.
51
(Planck
et al.
1914,
p. 95;
Planck
et al.
1912,
p.
115)
1)
What
I find
strange
about the
way
Mr.
Planck
applies
Boltzmann's
equation is
that he introduces
a
state
probability
W without
giving
this
quantity
a physical
definition.
If
one
proceeds
in such
a way,
then,
to
begin with,
Boltzmann's
equation
does not have
any
physical meaning.
The circumstance that
W
is equated
to
the number of
complexions
belonging
to
a
state
does
not
change anything
here;
for there
is
no
indication of
what
is supposed
to
be
meant
by
the
statement
that
two
complexions are
equally
probable.
Even
if it
were possible
to
define the
complexions
in such
a
manner
that the
S
obtained from Boltzmann's
equation
agrees
with
experience,
it
seems
to
me
that
with this
conception
of Boltzmann's
principle
it
is
not
possible
to draw
any
conclusions
about the
admissibility
of
any
fundamental
theory
whatsoever
on
the
basis
of the
empirically
known
thermodynamic properties
of
a
system.
No.[53] (Planck
et al.
1914a,
p. 98;
Planck
et al.
1912,
p. 119)
2)
Objections
have
often been raised
against
the
application
of
statistical
methods
to
radiation. But
I do not
see any reason why
these methods should be
excluded
here
(cf.
Lorentz's
report, §6-§13).
3)
Omit!
No.
100
(Planck
et al. 1914a,
p.
106;
Planck
et al. 1912,
p. 129)
4)
If
an
oscillator
is
to emit
radiation in
a manner
different
from
that assumed
in Mr.
Planck's
original theory,
then
this
means a
renunciation of the
validity
of
Maxwell's
equations
in the
vicinity
of the
oscillator.
For
according
to Maxwell's
equations,
the
quasi-static
field
of
the
oscillating
dipole
necessarily
results in
the release of
energy
in
the
form of
spherical waves.