236
THERMAL, ELECTRICAL,
&
RADIATION PHENOMENA
Weber's
supervision
(see
Doc.
63, especially
notes
2
and
3).
After
graduation,
he
hoped
to
use
Weber's
laboratory
for research
on
the Thomson
effect
(see
Doc.
74).
Around the
turn
of
the
century,
Riecke and Drude
published comprehensive
theories
of thermal and electrical
phenomena
in
metals
that
were
based
on
an
atomistic
conception
of
electricity.[3]
The
following
letter shows
that,
by 1899,
Einstein
also
looked
upon
the
study
of the
relationship
between
thermal and electrical
phenomena
as a
way
to
explore
the
microphysical
structure
of
matter: he
had
an
experimental
method to decide "ob
die
latente Wärme in Metallen auf
Bewegung
der
ponderabeln
Materie
oder der
Elektrizität zurückzuführen ist."
In the
spring
of
1901
Einstein raised the
possibility
that
the internal kinetic
energy
("latente
kinetische
Energie
der
Wärme")
of
solids
and
liquids is
"elektrische Resona-
torenenergie"
(Doc.
93).
If
it
were,
there should
be
some
link between the thermal and
optical properties
of
matter.
Einstein decided
to
look
for
a
correlation between
spectral
properties
and deviations from
Dulong
and Petit's
law
(see
Docs.
93,
94).
These
speculations
are
his first
known
attempt
to
relate Planck's
resonator
model
(men-
tioned
in Docs.
96,
97)[4]
to
the
problem
of
specific
heats. He
soon
came
to doubt
these
speculations (see
Doc.
97),
but half
a
decade later
he
developed
the first
quantum
theory
of
the
specific
heat of
solids.[5]
By
1899
Einstein
was
pondering
the nature of radiation
(see
Doc.
45).[6]
In
April
1901 he
discussed Planck's
work
on
black
body
radiation,
to which
he
had
an
objec-
tion
(see
Docs.
96,
97).
These
comments
seem
to
concern
Planck's classical
theory.
Einstein
probably
read
one
of
Planck's
quantum
papers soon
thereafter
(see
Doc.
97).
He
noted
a parallelism
between black
body
radiation
and
the kinetic
energy
of
molecules,
which
led
him to raise the
possibility
of
a
direct transformation of kinetic
energy
into
light
(see
Doc.
102).
Soon
afterwards,
Einstein commented
enthusiastically
on
Lenard
1900,
a
paper on
the
generation
of
cathode
rays by
ultraviolet
light (Doc.
111).[7]
In
1901
Einstein studied Drude's electron
theory
of metals
(see
note 2
and Docs.
96,
97).
This kinetic
theory
of
freely
moving charge
carriers
("Kerne"
or
"Elektronen")
provided explanations
for thermoelectric
effects
and the Wiedemann-Franz
law,
among
other
phenomena.[8]
Einstein
was
enthusiastic
about
Drude's
theory, noting
that
its
basic
assumption
had
previously
occurred
to
him,
"daß
es
vorzugsweise nega-
[3]
Riecke 1898
and
Drude
1900c, d.
Their
theories elaborated earlier ideas of
W. Weber,
Giese,
and F. Kohlrausch
(see
Riecke 1898,
pp. 355,
381,
and Drude
1900c,
p. 566).
[4] Adolf
Fisch,
a
fellow
student
at
the
Aargau
Kantonsschule and
the
ETH,
Section
VI
A,
is
said
to
have drawn Einstein's
atten-
tion
to
Planck's
articles
(see
Lüscher
1944, p.
623).
[5]
See
Einstein 1907.
[6] See also
the
editorial
note,
"Einstein
on
the
Electrodynamics
of
Moving
Bodies."
[7] Later work
by
Lenard
on
the
photo-
electric effect
is
cited
in
Einstein
1905a, a
basic
contribution
to
the
understanding
of both
black
body
radiation and the
photoelectric
effect.
[8] Einstein
1905a,
p.
133,
refers to
Drude's
explanation
of
the
Wiedemann-Franz
law.
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