394
CONSTITUTION
OF
RADIATION
nonuniformities.
I
shall
add
that another consideration
concerning
the
spatial
distribution
of
the
energy
yields results that
agree
quite well with
the
above
consideration
concerning
the spatial distribution
of
the
momentum.
As
far
as
I
know,
it
has
not yet
been
possible
to
formulate
a
mathemati-
cal
theory
of radiation that
would do
justice both
to
the
undulatory
structure
and to
the
structure
inferred
from
the first
term
of the
above
formula
(quantum
structure).
The
difficulty
lies
mainly
in the fact that the fluctu-
ation properties
of
radiation,
as
expressed
by
the
above formula,
offer
few
formal clues
on
which to
build
a
theory.
Imagine
that the diffraction
and
interference
phenomena are
not
yet
known,
but that
one
knows
that the
average
magnitude
of
the
irregular fluctuations
of
the radiation
pressure
is deter-
mined
by
the
second term of
the
above
formula,
where
v
is
a
parameter
of
unknown
significance
that determines the color.
Who
would
have
sufficient
imagination
to construct
the
wave
theory
of
light
on
such
a
basis?
Still, for the time
being
the
most
natural
interpretation
seems
to
me
to
be
that the
occurence
of
electromagnetic
fields of light is associated with
singular points
just like the
occurence
of
electrostatic fields
according
to
[31]
the electron
theory.
It is
not
out
of
the
question
that in
such
a
theory
the
entire
energy
of the
electromagnetic
field
might
be
viewed
as
localized in
these singularities,
exactly like in the old
theory
of
action
at
a
distance.
[32]
I
more or
less
imagine
each such singular
point
as
being
surrounded
by
a
field
of
force
which has
essentially the character of
a
plane
wave
and
whose
ampli-
tude decreases with the distance
from
the
singular point. If
many
such
sin-
gularities
are
present
at
separations
that
are
small
compared
with the
dimen-
sions
of
the field of force
of
a
singular point, then
such
fields
of
force
will
superpose,
and their
totality will
yield
an
undulatory
field
of
force
that
may
differ
only
slightly
from
an
undulatory
field
as
defined
by
the
current
electromagnetic theory
of
light.
I
am
sure
it
need
not
be particu-
larly
emphasized
that
no
importance
should
be
attached
to
such
a
picture
as
long
as
it
has
not
led
to
an
exact theory.
All
I
wanted
is briefly
to
indicate with its
help
that the
two
structural properties
(the
undulatory
structure
and the
quantum
structure)
simultaneously displayed
by
radiation
according to
the
Planck formula should
not be
considered
as
mutually
incompatible.