THEORY OF RELATIVITY 269
Eine
Konsequenz
der
elektrodynamischen
Arbeit ist mir noch in den Sinn
ge-
kommen. Das
Relativitätsprinzip
im
Zusammenhang
mit den
Maxwellschen
Grundgleichungen verlangt
nämlich,
daß die Masse direkt ein Maß für die im
Körper
enthaltene
Energie
ist;
das Licht
überträgt
Masse. Eine merkliche Ab-
nahme der Masse müßte beim Radium
erfolgen.
Die
Überlegung
ist
lustig
und
bestechend;
aber ob der
Herrgott
nicht darüber lacht und mich
an
der Nase
herumgeführt hat,
das kann ich nicht
wissen.[98]
The idea that inertial
mass
is
associated with
electromagnetic energy was
often
discussed
before 1905. Around the turn
of
the
century,
it
was suggested
that all mechanical
concepts
could be derived from those
of
electromagnetism.[99]
In
particular,
there
were attempts
to
derive the entire inertial
mass
of
the electron from the
energy
associated with its electro-
magnetic
field.[100]
It
was
also
proved
that
a
radiation-filled container manifests
an appar-
ent
inertial
mass,
which
(if
the
mass
of
the container
is
neglected)
is
proportional
to the
energy
of
the enclosed
radiation.[101]
In
his
first
paper
on
this
subject,
Einstein
argued
that,
as a
consequence
of
the
relativity
principle,
inertial
mass
is
associated with
all
forms
of
energy.[102]
He
was
only
able
to
establish
the association for
a process involving
the emission
of
electromagnetic
radiation
by a system,
but
argued
that the result
is
independent
of
the mechanism
by
which the
system
loses
energy.
In
addition,
he
was only
able
to
show that
changes
in
energy are
associated with
changes
in
inertial
mass equal
to
the
changes
in
energy
divided
by
c2.
His
argument was
criticized in 1907
by
Planck,
who
presented
his
own argument
to show that
a
transfer
of
heat
is
associated with
a similarly
related transfer
of
inertial
mass.[103]
Soon
afterward,
Stark attributed the
discovery
of
the
relationship
between
mass
and
energy
to
Planck.[104]
Einstein wrote Stark:
I
was
rather disturbed
that
you
do not
acknowledge my
priority
with
regard
to
the connection between inertial
mass
and
energy.
Es hat mich etwas
befremdet,
daß Sie
bezüglich
des
Zusammenhanges
zwischen
träger
Masse
u. Energie
meine Priorität nicht
anerkennen.[105]
After
receiving a conciliatory reply
from
Stark, acknowledging
his
priority,[106]
Einstein
replied,
regretting
his
original testy
reaction:
[98]
Einstein
to
Conrad
Habicht,
end
of
June–
end
of
September
1905.
[99]
Wien 1900
explicitly
states
the
program
of
an
electromagnetic
foundation
of
mechanics.
For
a survey
of
the
so-called
electromagnetic
world
view, see
McCormmach
1970b.
[100]
See
Abraham
1902a, 1902b,
1903. For
a
contemporary
review
of
such
attempts, see
Bucherer
1904,
pp.
51-68.
[101]
See
Hasenöhrl
1904, 1905,
and Mosen-
geil
1907. For
a contemporary
review
of
work
on
this
topic
that does
not
use
the
theory
of
rel-
ativity, see
Hasenöhrl
1909b.
[102]
See Einstein 1905v
(Doc. 27).
[103]
See
Planck
1907a,
§
17.
The critical
comment
on
Einstein's
argument
is
in
a
footnote
on p.
565.
For
a
discussion
of Planck's
argu-
ment,
and
later
criticisms
of Einstein's
deriva-
tion, see
Stachel and
Torretti 1982.
[104]
See Stark 1907.
[105]
Einstein to Johannes
Stark, 17
February
1908.
[106]
See Johannes Stark
to Einstein, 19
Feb-
ruary
1908.