The New York herald., 1921-02-13

| urement In physics Is the velocity of
light, for this is' the only thing which
is constant and Independent of all
other things. He shows with nicely of
proof an element OF the Einstein theory
which has been so extensively ex-
plotted for the popular imagination
how, for instance, the length of any
body depends on It's velocity with ref
erence to any system.
So. step by step, the Einstein theory
of relativity unfolds wonder upon won
der of revolutionary physical doctrine.
1t is difficult for us to conceive at
first that the nero presence of large
rotating bodies will set up a rotation
In another body, yet our new theories
point that way. For here again Elm
stein by a simple logical syllogism,
supported by certain fundamental
physical equations, has proven an
identity between Gravitation and In
ertia. In a word, when a body re-
ceives an acceleration-or, as we
usually put 1t in non-physical Ian
guage. "falls"-it is really impossible
to say whether the motion is due to
Gravitation or to Inertia.
Another revolutionary doctrine of
the newer physics is that which In
wolves the relation of mass to energy.
We had, until quite recently, held that
mass was indestructible. We might. for
instance. burn" piece OF wood, but
we simply thereby converted part of
the solid matter into a gas, and the
total quantity Of mass remained the
same. Since we could not destroy
matter, we could not, OF course, create
it. either. But we are now led to the
theory that II a body takes up guam
tity OF energy 1t behaves as II the
total mass has been increased, and
so we go a step further and say that
every mass may be calculated in terms
of the amount of energy contained
in IL
The verification of the identity of
mass and energy was strikingly given
by the observations made during the
eclipse OF the sun in May. 1919, pre-
cisely as predicted by Einstein. It
was found that the light rays from
certain stars were actually DETECTED
by the suns gravitational field. This,
the final justification OF the Einstein
set the people of two hemispheres
talking and thinking about the new
wonders of physical science.
1t may be a comfort to the timid-
minded to know that while the theory
of relatively. which Einstein has so
powerfully developed, is of revolution
ary magnitude, our ordinary physics
which deals with relatively small
things is for the present not TO be
overturned. Even though length be
relative, and function OF the velocity
OF the body; though our masses vary
with the amounts of energy they con-
tain. and bodies are caused to rotate
by the presence of other large bodies;
yet we shall probably never be per-
mitted to see such rotation set up, nor
are the contractions of a body or It's
increase In mass due to its having re-
ceived energy from without of such
amount as to be appreciable. These
are things after all which we shall
have to accept as mathematical de-
ductions. and which the layman will
have to take on faith.
Prof. Schllck writes in vigorous.
scientific style. building proof on
proof. citing simple examples to en-
phasize his points. He Is Justly criti-
cal OF the errors which various physi-
cists have made from time to time In
their deductions. but he appears to
have the greatest admiration and re-
spect for the giant intellect and genius
OF the man whose name In the science
Of physics is by far the greatest since
Newton.