The New York herald., 1921-02-13

old, Einstein having first brought for
ward his analysis in 1905 The more
complex general theory has been de-
duced by him and by the world of
scientists since that time.
AS an example. the general theory
disregards the ether We had been
accustomed to talking Of rays Of light
travelling to us from the sun or the
stars. through the ether. But Einstein
says that the ether does not exist; for
we nave been unable to prove its ex-
istence In spite OF ingenious expert
ments. The famous Michaelson and
Morley experiment, in which the in
vestfgators measured the velocity of
beam of light in path parallel
with the earth's flight through the
ether and simultaneously at right
angles to It, showed the velocity of
light to be the same In both directions.
that is, when the earth and the light
We're travelling In the same direction
through the ether as we'll as when
at right angles to each other. They
were thus unable to prove the exist
ence OF the ether. and since, as Elm
stein points out, 1t is not necessary to
our concepts In contemporary physics.
we may hold that it does not exist.
And 90 we Danish the ether, which
we have In the past been using as a
basis of all our physical theory. We
can no longer think of the earth as
slipping through real, though intan-
gible medium. While we believed in
Its reality it served as centre of ref
m ~
solute motion with respect to the
ether. But now that we have lost
even our imaginary stable element we
can think of motion only as relative.
Put into the simplest terms, all mo-
tions of any body may be defined only
by reference to another moving body.
or to a system: and any motions in
system must likewise be referred TO
another system, moving with respect
to the first. And any physical laws
which are true in one system are
equally true in the other system. Thus
does the author formulate the So
called Special principle of relativity,
which he later shows developed into
the General theory OF relativity.
There is wonderful speculation in
all this. which Prof. Schlick imagi-
natively and graphically points out.
He shows and proves by the analysis
Of great scientists that IL the physical
world were completely changed, let ,is
say overnight, we may maintain that
SO long as certain definite relations
obtain for the New World as well as
for the Old we should be unable to
detect any change. And since this is
SO. he goes on to say. we may con-
clude that we actually do exist In
this changed world; i'm other words,
that there are lines which we had pre-
viously called straight which are
curved. and surfaces which we had
been accustomed to call flat which are
really not so.
Sometimes the scientist, no less than
the layman. stumbles on truths. Schlick
recites how, when Michaelson and
Morley failed to prove the existence Of
tile ether. two other scientists (Lo-
rent and Fitzgerald), offered theory
suit obtained. They proposed a most
ingenious theory. that every body suf-
fers certain contraction when in mo-
ton. due to It's velocity. This hy-
pothesis. while correct In its mathe-
matics, was altogether false in the as
sumption on which It was based. The
modern theory shows that such a con-
traction must be considered. but It is
not the result Of the motion. but rath-
er Of the methods used in physics
for measuring space and time For
we have no absolute measure of these
The fundamental unit for all meas