110
DOC.
153 MAY 1909
This
calculation
is
exactly
analogous to
a
calculation that
you
once
gave.[11]
3
If
one
takes the
mean
kinetic
energy
of
a
molecule to
be
/2
kT,
then
Ū
=
kT,
and
if
one
sets
el =
hv,
one
obtains for the
mean energy
of the element
G1
hv
hv
kT
_ X
(1)
One
could
apply
this
to
a
Planck resonator
but
also
just
as
well to
the different
degrees
of freedom of
the
ether
in
my
rectangular box.[12]
To
determine then the
energy
contained
in
the
latter,
insofar
as
it
corresponds
to the
interval
(v,
v
+ dv),
one
need
only
multiply (1) by
the number of those
degrees
of freedom
for which
v
lies
between the
limits
indicated.
One
then obtains Planck's radiation formula
directly.
If
in
this
way
one
conceives
of
the
constant
h
as
expressing a
property
of the
ether,
then the
difficulties that the simultaneous
existence
of free
electrons and
resonators
would
otherwise
create disappear,
as
already
stated; it would
now
be
the ether that
would
stubbornly
resist the
absorption
of
energy
in
any
but
whole
quanta quite
independently
of
which
particles proffer
this
energy
to it.
If
one
ascribes
the
discussed
property
only
to
the resonators and
not to
the
ether
itself,
and
thus
assumes
that
the latter
can
also absorb
energy
in
infinitesimally
small
quantities,
then
I
fear that
one
would
perhaps
arrive
again
at
a
law
for the ether
such
as
Jean's
law.
However,
all
of
this
is
still
so
hazy
that
it
is
only
with
a
certain
reservation
that
I
would
want to
express my
views
on
the
matter.
In
any case,
it
must
be
noted that
if
one
regards
h
as a
constant
of the
ether,
one
then
deprives
this medium
of
part
of its
simplicity
and
directly opposes
the
views
of those
physicists
who want
to
deny
to
ether
almost
all
"substantiality."
You
too
are
inclined
more or
less
to
give
up
the
prevailing
conceptions
of
the
ether,
and in this
respect
our
views
are
in
agreement.
But
I
find it
hard
to
subscribe
to
the
view
that the
light
quanta
retain
a
certain
individuality even
during
their
propagation,
as
if
one were
dealing
with
"punctiform" energy quantities
or
at
least
energy quantities
concentrated
in
very
small volumes.
It
seems
to
me
that
it
can easily
be shown
that
a
light
quantum
can
have
a
considerable
extension in the
direction of
propagation
as
well
as
perpendicularly to
it,
and
that under certain
circumstances
only
a
part
of
a
light
quantum
reaches the retina
and
brings
about
the
perception
of
light.
First let
me
note
that
a
light
quantum
hv
is
not all
that
small.
It
can
be
deduced
from
von
Kries's observations
(Zeitschr.für
Sinnesphysiologie,
Vol.
41, p.
373)[13]
that
the
perception
of
light
is
produced
when
as
little
as
30
to 60
light
quanta
strike the
eye
within
a
short
time
interval,
while
about
140 quanta per
second
are
required
if the
radiation
is
continuous.
In view
of the
complexity
of
phenomena
that
must
take
place