xxii
INTRODUCTION
TO
VOLUME
2
thermal
radiation.[29]
Were there other such
principles upon
which
one
could
rely
in the search for
"elementary
foundations"?
In
retrospect,
whether
or
not
Einstein
saw
it in such
terms at
the
time,
one can
view the
development
of
the
theory
of
relativity
as
Einstein's
first
great success
in
finding a
"universal
formal
principle."
For
some years,
he had been
trying
to
develop an electrodynamics
of
moving
bodies
that
did not
invoke
an
ether frame
of
reference.[30]
After
vain
attempts
to
modify
the Maxwell-Lorentz
equations
or
replace
them with
an
emission
theory
of
light,
he found that the correct
way
to
approach
the
problem was
to start from
principles,
whose role is
analogous
to that
of
the laws
of
thermodynamics.
In 1907 he summarized the nature
of
the
resulting
theory:
One is
not
dealing
here in
any way
. .
.
with
a
"system," in which the
individual laws would
implicitly
be contained and from which
they
could be found
merely by
deduction,
but
only
with
a principle
that
(in
a
way
similar
to
the second law
of
thermodynamics) permits
certain laws
to be deduced from others.
Es
handelt
sich hier
. . .
keineswegs um
ein
"System,"
in
welchem
implizite
die einzelnen Gesetze enthalten
wären,
und
nur
durch Deduk-
tion daraus
gefunden
werden
könnten,
sondern
nur um
ein
Prinzip,
das
(ähnlich
wie der zweite
Hauptsatz
der
Wärmetheorie) gewisse
Gesetze
auf
andere zurückzuführen
gestattet.[31]
The
theory
demonstrates that the
relativity principle,
in
conjunction
with the
principle
of
the
constancy
of the
velocity
of
light,
requires
a new
kinematical
foundation for all
of
physics. By
applying
this kinematics
to
the
Maxwell-Lorentz
equations
for bodies
at rest,
Einstein
was
able
to
formulate
an electrodynamics
of
moving
bodies that is in accord with
experiment.
Einstein's
1905
paper
discusses
Maxwell's
equations
in
empty space.
The
problem
of
formulating relativistically
invariant
equations
for
electromagnetic
fields in
moving
media,
first discussed
by
Minkowski in
1907,[32] was
addressed
by
Einstein
in
1908,
in
collaboration
with Jakob
Laub.[33]
[29]
Describing many years
later
the
deep
impression
that
thermodynamics
had
made
upon
him, Einstein stated:
"It
is the
only physical
the-
ory
of
universal content
concerning
which
I
am
convinced that, within the framework
of the
ap-
plicability
of
its basic
concepts,
it will
never
be
overthrown" ("Es
ist die
einzige
physikalische
Theorie
allgemeinen
Inhaltes,
von
der ich
über-
zeugt
bin,
dass sie im Rahmen der Anwendbar-
keit
ihrer
Grundbegriffe
niemals
umgestossen
werden
wird")
(Einstein
1979,
p.
30,
transla-
tion,
p.
31).
[30]
See Vol.
1,
the editorial
note,
"Einstein
on
the
Electrodynamics
of
Moving
Bodies,"
pp.
223-225.
[31]
Einstein
1907g (Doc. 44), p.
207.
[32]
See Minkowski 1908.
[33]
See the editorial note,
"Einstein
and Laub
on
the
Electrodynamics
of
Moving
Media,"
pp.
503-507.
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