The New York herald., 1921-06-19


- collection of the best thought
ON this subject from among the 300
essays submitted for the $4,000 Eu-
gene Higgins prize contest conducted
by the Scientific American The es-
says We're limited to 5000 words. The
first half of the book is an intro
duction to the subject compiled from
more than fifty of the better essays,
synthesized and supplemented by Mr..
Bird. and is intended to prepare the
reader 20 understand better the com
plete essays which follow. The book
reminds one of number of Snapshots
taken of the same object-no single
one gives a clear picture, but there are
so many Of them. each from a differ
ent angle, that by the time one has
seen them all one has fairly distinct
picture. The following is of the nature
of composite photograph" in out
line.
Newtons two laws of motion, ex-
planned in terms of Euclidean geome-
try, have hitherto been thought to be
Fundamental and absolutely accurate
descriptions of physical phenomena.
They are "a "a body i'm state Of
rest Or Uniform motion in the same
straight line will continue so unless
acted upon by some eXtepal force
claw of inertia)." and (2) every
particle in the universe attracts every
other particle with force that is
directly proportional to the square of
their masses and inversely proper
tional to the square of their distances
apart Claw of gravitation)."
In his principles of relativity and
eravitation Einstein shows Cd that
we have no way of determining abso-
lutte space and time: CD that inertia
and gravitation are not. as Newton be-
lieved, two Independent phenomena,
but parts of a more fundamental as
,pect of nature. and go that Euclidean
geometry which has been used for the
statement of general physical laws, is
not universal in it's application.
All investigation of reality presup-
poses an observer. and the first thing
an observer must do is to measure.
The basis of all measurement is a rod
tyard-stick. moter-stick &C., and a
clock. In locating an object on or
above the earth we assume that the
earth is at rest as regards that object.
IT, however. we wish to determine the
position or motion of the earth we
consider the sun as at rest. and there
by ascertain that the earth has uni
form motion Of 1872 miles n second
relative to the sun.
But is the sun itself at rest? AS
tronomers. assuming that distance stars
liSnnVnrnd
that the sun and its planets have a
uniform motion of 400.000.000 miles
year relative to the star Vega. Are
we moving toward Vega, or is Vega
moving toward us. or are we both
moving together. or is Vega moving
away from us. while our speed is SO
great that the distance between Vega
and us is shortened about Ia miles
each second. or vice versa-in short.
what is our absolute motion I'm the
universe. and not our relative motion?
We do not know. For. to be able to
determine absolute motion there would
have to be 2 body in the universe a.
absolute rest. and there probably is
10 such BODY.
The only conclusion we can draw is
that IAN observer on a uniformly NOV
ing system can determine only the
relative motion of his system" Which
forms one part of Einsten's Special
Principle of Relatively.
Now, the greatest speed that man
has been able to discover i'm the uni
verse. and, consequently, the only re-
liable standard for time (time is funda-
mentally motion-the motion OF the
earth. the motion of a clocks pendu-
um) Is that of ray Of light-lS633O
miles a second. 1t was found by
scientific experiment as far back as
1887 that. whether the earth is moy-
ing toward or away from a ray OF
light. the velocity of light remains the
same The experiment has been re-
peated again and again, always veri-
fled. and must therefore be taken as
an established fact. We have here the
rest of Einstein's Special Principle of
Relatively: "In a vacuum the velocity
of light is constant for all Observers
whatever the velocity of their relative
motion"
What. you ask. is the significance
of Einstein's special principle? Space
and time measurements or one system
by an observer on another system
vary as the relative motion OF the two
systems approach the velocity Of light.
IT, for example, an observer on an
other system were passing us at nine
tenths the velocity OF light. objects on
his system. in the direction Of relative
motion. would appear to us less than
one-h half the length that they appear
10 him. and a second on his clocks
would seem like two and half OF our
seconds. And 60 a same degree objects
on our system. in the direction Of rela-
tive motion. would appear shortened
TO him and our clocks too slow
The reason that measurements on
one system In the direction OF relative
motion appear shortened TO an OBJ
server on another system is that, no
matter how accurate the measuring
instruments. some time will elapse In
making the measurements and during
that time the system under observa-
ton will have advanced In the case
Of system moving at nine-tenths the