378 DISCUSSION
OF
SZARVASSI
Doc. 59
"Discussion"
following
lecture
version
of
Arthur Szarvassi,
"The
Theory
of
Electromagnetic Phenomena
in
Moving
Bodies
and
the
Energy
Principle"
[Physikalische
Zeitschrift
10
(1909):
813]
[1]
Einstein:
I
think that
a body
subjected to
some
forces, that this
body,
when
observed
from
a
relatively
moving
coordinate
system,
because
of
its
being
[2]
subjected to
forces,
represents
an
energy.
If
this
assumption
is
not made,
there
will
arise
a
violation
of
the
energy
principle. Don't
you
think
that
this
may
be
the basis
of the
example
you
considered? Is it clear
to
you
what
I
mean?
Lecturer:
Not completely.
Einstein: It
can
be
shown
that
a moving body
subjected to
forces
whose
resultant
does
not
vanish,
in certain
cases
does
not get
accelerated
thereby.
One
must
therefore
assume
in
the
theory
of
relativity that
the
moving
(rigid)
body
subjected to
forces
possesses
a
certain
energy
content;
otherwise,
one
gets
a
violation
of
the
energy
principle.
Lecturer:
That
would
mean
that,
besides the
so-called kinetic
energy
in
the
currently
accepted
sense,
and
besides the so-called usual
potential elec-
tric
energy
of
the
system,
there exists
an
additional part
of
energy.
Because
I
made
no
assumption
about the
quantity
v,
the
above
part
would
have
to
be
contained
in
this function. After all,
I
did
not
say
anything
about the
form
[3] of
the function
v.
The
energy
equation
expresses
the
energy
principle quite
generally.
It is
very
likely
that this
energy
quantity
is
contained
in
v.
Einstein: I
cannot comment
on
that, because
I did
not enter
suffi-
ciently
into the
spirit
of
this consideration.