174 INERTIA
AND
ENERGY
CONTENT
H0-E0
=
K0
+ C
H1
-
E1
=
K1
+
C,
since
C
does
not
change
during
the emission of light.
Thus,
we
get
K0-K1
=
L
1
1
-
V
V
7
1
The
kinetic
energy
of
the
body
with
respect
to (£,
?,
C)
decreases
as a
result
of
the emission
of
light
by an
amount
that is
independent
of
the
body's
characteristics. Furthermore,
the difference
K0
-
K1
depends
on
the
velocity exactly
like the kinetic
energy
of
the electron (loc. cit.,
§10).
Neglecting
quantities of
the fourth
and higher
orders,
we can
put
[2]
Ko
-
K1 =
L
v'
0
1
"
F
2
From
this
equation
it
follows
directly:
If
a body
releases the
energy
L
in the
form of
radiation,
its
mass
decreases
by
L/V2.
Since
obviously
here it is inessential that the
energy
withdrawn from
the
body
happens
to turn
into
energy
of radiation rather than
into
some
other
kind of
energy,
we are
led
to
the
more
general
conclusion:
The
mass
of
a body
is
a measure
of its
energy
content;
if the
energy
changes
by
L,
the
mass
changes
in the
same sense by L/9.1020,
if the
energy
[3]
is
measured
in
ergs
and
the
mass
in
grams.
Perhaps
it will
prove
possible to test
this
theory using
bodies
whose
energy
content
is variable
to
a
high degree
(e.g., salts
of radium).
If
the
theory agrees
with the facts, then radiation
transmits
inertia
[4]
between
emitting and
absorbing
bodies.
Bern,
September
1905.
(Received
on
27 September
1905)