300
THE
RELATIVITY PRINCIPLE
dQ
=
1
"
^5"
(dE0 +
p0dV0)
or
dQ
=
•
jl
-
(26)
Further, since
according
to
(24)
the
two equations
dQ = Tdrj
[87]
dQo
= T0dn0
hold,
one
finally obtains,
taking
into
account
(25)
and
(26),
T
[88]
1
-
§
•
(27)
Thus,
the
temperature
of
a moving
system
is
always
lower
with
respect
to
a
reference
system
that is
in motion
relative
to
it than with
respect
to
a
reference
system
that
is
at rest
relative
to
it.
§16.
The
dynamics
of
systems
and
the
principle
of
least
action
In his treatise
"On
the
dynamics
of
moving
systems," Mr.
Planck
starts
out
from
the principle
of
least action
(and
from
the transformation
equations
for the
pressure
and temperature of
black-body
radiation)1
and
arrives
at
results that
are
identical with those established here.
The question
arises,
therefore,
as
to
how
the foundations
of
his
study and
the
present
one are
related.
We
started from
the
energy
principle
and
the principle
of
conservation
of
momentum.
If the
components
of
the
resultant
of
the forces
acting
upon
the
system
are
called Fx,
Fy,
Fz,
we can
formulate
in
the
following
way
the
principles
we
used
for reversible
processes
and
a
system
whose
state
is
defined
by
the variables
q,
V,
T
:
1M.
Planck, "Zur
Dynamik
bewegter Systeme"
[On
the
dynamics
of
moving
systems].
Sitzungsber.
d. kgl.
Preuss.
Akad. d.
Wissensch.
(1907).
[89]