The Denver Jewish news., 1920-01-21

But in addition to this most weighty
group of theories, there is another
group consisting of what call the
cries of principle. These employ the
analytic, not the synthetic method.
Their starting point and foundation are
not hyptonetical constituents, but EN-
pirically observed general properties
of phenomena principles from which
mathematical formulae are deduced of
such kind that they apply to every
case which presents itself.
Thermodynamics, for instance, start
ing from the fact that perpetual mo-
tion never occurs in ordinary exper-
ience, attempts to deduce from this
by analytic processes II theory which
will apply in every case. The merit
of constructive theories is their com
prehensiveness, adaptability and clarity
that of the theories of principle their
logical perfection and the security OF
their foundation.
The theory of relatively is theory
of principle. To understand 1t, the
principles on which it rests must be
grasped. But before stating these it
is necessary to point out that the the
ory of relatiyity is like house with
two separate stories, the special rela'
tiyity theory and the general theory
of relativity.
Must Be q Comparison.
Since the time of the ancient Greeks
1t has been well known that in describ-
ing the motion OF body we must refer
TO another body The motion of
railway train Is tiescPiSed with refer
enee to the ground. 0f a planet with
reference to one total assemblage of
visible fixed stars In physics the
Lodies to which motions are specially
referred are termed systems of CO.
ordinates. The laws of mechanics OF
Gailleo and Newton can be formulated
only by using a systems of co-ordina-
tion.
The state of motion of a system OF
co-Ordinates cannot be chosen arbi-
trarily If the laws of mechanics are
TO hold good lit must be free from
twisting and from acceleration). The
system of co-ordinates employed In
mechanics is called an iliertia-system
The state of motion OF an inertia sys-
tenn SO far as mechanics are concern
cd. is not restricted bS nature to one
condition. The condition In the follow
ing proposition suffices; system Of
co-ordinates moving in the same di-
| rection and at the same rate as
system of inertia is itself O system
of inertia. The special relatively the.
cry is therefore the application OF the
following proposition to any natural
process: Every law of nature which
holds good with respect to co-ordip-
i.te system X must also hold good for
any other system X, provided that Is
and x are in uniform movements of
translation.
ReIatiyity's Second principle.
The second principle ON which the
special relatiyity theory rests Is that
OF the constancy of the velocity of
light in a vacuum. Light in vacuum
has definite and constant velocity
independent of the velocity of its
source Physicists owe their confidence
in this proposition to the Maxwell
Lorents theory of electro-dynamics.
The two principles which 1 have
mentioned have received strong ex-
pcrimental confirmation, but do not
seem to be logically camhatible. The
special relativity theories achieved
their local reconciliation by making
II change in llinematics. that is to say,
in the doctrine of the physical laws
Of space and time. 1t became evident
that statement of the coincidence OF
two events could have a meaning only
in connection with system of CO.
ordination, that the mass of bodies
and the rate of movement of clocks
must depend on their state of motion
with regard to the co-Ordinates.
Latest Energy in Inert Mass.
But the older physics, including the
laws of motion of Galileo and Newton,
clnshed with the relativistic kline
matics that l have Indicated. The lat
ter gave origin to certain generalized
mathematical conditions with which
the laws of nature would have to con-