DOCS.
385,
386
APRIL
1912 289
385.
To
Emil
Warburg
Prague,
25
April
1912
Einstein writes
of
Warburg's "photochemical laboratory."
in
which all
the
things
I
have
been
dreaming
about
in
vague
outlines for
years
have
become
reality.
I
do not
doubt that
you
will
completely
succeed in
the
difficult
investigation
you
have
begun,[1]
and that
you
will
clarify
the mechanism of
your
reaction.
Apart
from
what
we
have
discussed,[2]
the
temperature dependence
of the reaction
O2
+
O
= O3
is
also
of
great
interest,
because
this
reaction
can only
take
place
because of thermal
agitation,
from which it
takes
its
energy.
From
this
there
emerges
a
new
criterion for
the
correctness
of the
underlying
theoretical
conception.
.
.
.
386.
To
Emil
Warburg
[Prague,
after
25 Aprilbefore
11 May
1912][1]
But if
one
refers
everything
to
a
noncomoving system,
then the
clock
already
has
a
finite
v/c
when
it
is at
rest in
A,
and
now
the
infinitely
small
additional
velocity
effects
a change
in
the
speed at
which it
runs
that
is
infinitely
small in
the
first
order,
i.e.,
a
lag
of
finite
magnitude (for
the
whole
trip),
with
respect
to
a
clock
that
has
been
left at A.
However,
all of
this
holds
with
respect
to
the
system
of clocks
that
does
not
move
with
the
train,
but
not with
respect
to
a
system
of
clocks
located
and set
on
the train. At
its
arrival at
B,
the
portable
clock would show the
same
time
as a
clock
of the
system
AB
that remained
at rest at
B.
The latter
runs more
slowly
than
even
the
clock
at A,
if
both
clocks
are
evaluated
from
the
system
that
does
not
move along
with
the train. If
the
clock
is
moved
back
from B to
A
infinitely
slowly,
then
its
rate,
as judged
from
the
system
"at
rest," is
faster than
if it
stayed
at A
or B,
and this
compensates
for the
lag
that
occurred
for the
observer "at rest"
during
the
clock's first
leg
of
the
trip.

Meanwhile
I
have
pondered to
what
extent
the
law
of
equivalents
can
be
justified
in
the
case
when
the
absorbing,
photosensitive
molecule
has
a
finite
photochemical spectral
range.[2]
If
one
applies
the
previous
reasoning
to this
case,
then
one
obtains the
following.
If
the
molecule
is
photosensitive
between
v1
and
v2,
then
in
the
case
of irradiation with
quasimonochromatic
radiation
v,
the
law
of
equivalents
holds for
the value
v
belonging
to
the
radiation,
provided
it
is
permissible
to
introduce
a
virtual
displacement
of
the
system
in which
only
the radiation of
frequency
v
undergoes
photochemical conversion,
while
the
radiation of other
frequencies
of
the
sensitivity
range
is
left
unchanged.[3]
This
is
probably permissible
since
the
absorptions
of
the
different
frequencies
of
the
range
must