INTRODUCTION TO VOLUME
3
xxiii
any
harm because the
most
intimate
contact
with
experiment
is
maintained.
Einstein's
"quantum
hypothesis"
is
probably
one
of the
most
re-
markable
ever
devised;... if
it
is
false, well,
then it
will
remain for all
time "a beautiful
memory".[36]
Nernst's
positive
reaction
to
Einstein and his work would
soon
have
impor-
tant
consequences
for Einstein's
career.
Einstein had
developed
his
theory
of the
specific
heats of
solids
in
1907
on
the basis of
a simple
model: the N
atoms
of
a
solid vibrate
independently
about
their
positions
of
equilibrium,
and
all
3N of these vibrations have
the
same
frequency
v.
The
average energy
of each such oscillation
was
then
assumed
to be
given by
the
same
formula Planck had used in his
theory
of
black-body
radiation. The
frequency
v
was
the
only quantity characterizing
a
given
solid,
and the
key question, therefore,
was
how
to
determine this
frequency
from
some
measurable
property
of
this
solid, a
property
other than
the
specific
heat.
For
those substances
that
absorb infrared
radiation,
Einstein
suggested
that
the
frequency
at
which this
absorption
is
a
maximum-the
frequency
of the residual
rays
(Reststrahlen)-should be
identified with the
frequency
of atomic vibrations.
Since not
all substances exhibit this
phenom-
enon,
there
was no independent general
method available for
finding
the
atomic vibration
frequency
of
Einstein's
theory.[37]
When Nernst's
experiments
confirmed
beyond
any
doubt that
Einstein's
theory captured
the essential features of the behavior of
specific
heats with
temperature,
Einstein returned
to
the
problem
of
determining
v,
the
frequency
of atomic
vibrations.[38] Since
the
same
forces
give
rise to
both
the atomic
vibrations and the elastic
properties
of the
solid,
it
is
not
surprising
that
Einstein
was
able
to
derive
an
equation expressing
v
in
terms
of the
com-
pressibility
of the solid
along
with its
density
and molecular
weight.
Einstein
was
not alone
in
making
this connection between
an
elastic
constant
and
an
optical property
(the
absorption
frequency)
of
a
solid.
The Australian
physicist
[36]"Wir können
im Hinblick auf
der
Entwicklung
der
Physik, wie
ich
glaube,
sehr froh
sein,
einen
jungen so originellen
Denker
zu
besitzen,
einen 'Boltzmann
redivivus';
dieselbe Intensität
u. Schnelligkeit
der
Auffassung-grosse
Kühnheit in der
Theorie,
die
aber
nichts schaden
kann,
weil
der
innigste
Contact mit dem
Experiment gewahrt wird.
Die
'Quantenhypothese'
Einsteins
gehört
wohl
zu
dem
Merkwürdigsten, was
erdacht
wurde;
...
ist
sie
falsch, nun so
wird
sie
für
alle
Zeiten 'eine
schöne
Erinnerung'
bleiben!" Walther
Nernst
to
Arthur
Schuster,
17
March
1910
(UkLRS, Sc.
130).
See
Barkan
1990,
which
first
drew
attention
to
this remarkable letter.
[37]See Einstein
1907d
(Vol. 2,
Doc.
42).
[38]Einstein
1911b
(Doc.
13).