376
THE
RADIATION
PROBLEM
Doc. 57
ON
THE
PRESENT
STATUS OF THE
RADIATION
PROBLEM
by
W.
Ritz
and
A.
Einstein
[Physikalische
Zeitschrift
10
(1909):
323-324]
[1]
To
clarify
the
differences
of
opinion
that
came
to
light
in
our
respective publications1,
we
note
the
following.
In the special
cases
in which
an
electromagnetic
process
remains
restricted
to
a
finite
space,
the
process
can
be
represented in
the
form
f
=
f
1
=
1
x',
y',
z',
t
- -
dx'
dy'
dz'
as
well
as
in
the
form
f
=
f2
1
x'
y' z'
,t
+
-c
dx'
dy' dz'
and
in
other forms.
While
Einstein believes
that
one
could restrict oneself
to
this
case
without substantially
limiting
the
generality of
the consideration, Ritz
considers this restriction
not
to
be permissible
in
principle.
If
one
takes
this
standpoint,
then
experience
compels one
to
consider the
representation
by
means
of
retarded
potentials
as
the
only
one
possible,
if
one
is inclined
to
the
view
that the fact
of
irreversibility
of
radiation
processes must already
find its
expression
in the
fundamental
equations.
Ritz considers the restric-
tion
to
the
form
of retarded potentials
as
one
of
the
roots
of the
second law,
while
Einstein believes
that
irreversibility is
exclusively
due
to
reasons
of
[3] probability.
Zurich,
April
1909.
(Received
on
13
April
1909)
[2]
1W.
Ritz,
Phys.
Zeit.
9
(1908): 903-907,
and
A.
Einstein,
Phys.
Zeit.
10
(1909):
185-193.