DOC.
47 301
dE
=
F
dx
+
F
dy
+
F
dz
-
pdV +
TW,?
x
y
z
(28)
[90]
a:
Keeping
in
mind
that
x
It
,
etc.
FJx
x
and
Fx dt
-
xdG
-
d(xG)
-
Gdx
,
etc
X
X'
X
Tdrj
=
d(Trj)
-
rjdT
,
one
obtains
from
the
above
equations
the relation
(29)
d{-E
+
Tr]
+ qG)
-
G
dx
+ G dy
+
G
dz
+ pdF +
rjdT
.
x
y
z
Since the
right-hand
side of this
equation
must
also
be
a
total
differential,
and
taking into
account (29),
it follows that
[91]
d
It
M
dx
=
F
x
d
It
M
ßy.
=
/
y
d
It
M
dz
=
F
z
OH
W
P
dH
« IT =
V
But
these
are
the
equations
derivable
by means
of the
principle
of
least
action
which
Mr.
Planck
had used
as
his starting
point. [92]
V.
PRINCIPLE
OF
RELATIVITY
AND
GRAVITATION
§17.
Accelerated
reference
system
and gravitational
field
So
far
we
have applied
the principle of relativity,
i.e.,
the
assumption
that the physical laws
are
independent
of the
state
of
motion
of the reference
system, only
to
nonaccelerated reference
systems.
Is it conceivable that the
principle
of
relativity
also applies
to
systems
that
are
accelerated relative
to each
other?