The New York herald., 1922-12-17
Relatively in Everyday Life
Familiar Illustrations of the Enstein Theory and the
Deductions Drawn From 1t.
By JACQUES W. REDwAY, F. R.c. S.

| A writer whose opinion Is not lightly
to be disregarded Is authority for the
tatement that very few persons In the
world are able to understand the theory
| Of relatively as propounded by DR.. Al
bert Einstein. r. one appli-s this to the
more abstruse conceptions. which re-
quire mathematical demonstration. the
opinion is well founded. Nevertheless
there are Illustrations of relativity
which come into everybody's life al
most daily.
The scope OF human senses is limited.
| There are sounds audible to other ami
NAL life which the human being cannot
hear. There are things visible which
the human eye cannot see. There are
things tangible which the human touch
cannot feel. We cannot feel light. nor
can we hear Il. We cannot see the air
but we feel It when II strikes against
our bodies. We cannot feel or see
molecules in themselves. but we car
measure them. weigh them and compute
their motions.
Even seeing and hearing ius way
are relative. We see the fash OF light
ming and hear the crash Of thunder
But were a skillful surgeon to sever
the optic and auditory nerves. each a.
proper point. joining each on the
trunk Of the other, we should hear the
| lightning and see the thunder.
Now. because Of the limitations OF the
senses. the human mind must remedy
certain deficiencies by the aid OF math-
ematics. The mind can conceive many
things which to the senses do not ex-
list. The sense OF sight may be mislead-
ing and imperfect, especially whom mo-
ton Is involved as q factor. Railway
ties, for instance, are laid at right
angles under the rails they are straight.
not bent. pieces OF timber Eut when
one Is travelling on the Empire State
Express the ties OF the two tracks or
the left Of the train seem to curve In
ward toward the train. OF course this
is an optical illusion depending on the
sluggishness Of sight But II ono were
travelling throughout life on the train
the illusion would always persist. That
is, re.ativel, 70 the train ties arc bent
and curve inwardly; relative to the
roadbed they are straight and at right
angles thereto. It all depends whether
one considers the matter from tho one
basis or the other.
| What one sees when IN motion may
be- materially different from what one
sees when motionless; In other words,
sight perception is relative to motion
or to fixed position, so far as things
terrestrial are concerned. All this, now
ever. is not part Of Einstein's theory
OF relativity; it illustrates. nevertheless.
some of the elementary principles which
the theory must take into consideration.
| In the broader aspect OF the qucs-
ton one naturally takes three factors
into onsideration--mot!on. time and
space. The watchman on the Albany
night boat walks back and forth across
the deck. SO far as the boat 10 con-
cerned his movement Is g straight line
east and west, many times repeated.
But the boat is moving In northerly
direction. and II his path were protected
as visible line upon the water 1t wouio
be succession Of ziszags reaching from
New York to Albany. ranged In q fairly
straight line. The earth. however, is
turning on Its axis In the meantime and
this motion would whirl the watchnan's
zigzag out OF a straight line. bending II
many hundred miles to the right.
still further. the earth Is revolving
about the sun: and the sun with its
train of planets is flying along in space
To project the watchmans back and
forth ambulation as q line into space
therefore. requires the calculations OF
an astronomer and the astronomer
must first conceive himself In space,
viewing from a fixed point the resultant
of many motions. A graph, or trail. o!
the watchmans wanderinss In space Is
absolute only when viewed from such
a nxed point: from all moving POSI-
tions Il Is relative.
To terrestrial ;rortals space has
three dimensions--length. breadth and
thickness---as human senses permit us
to conceive. But that 70 merely q
casual hallucination inherent upon de-
fectivc human senses. The astronomer
and DR.. Einstein may not be able to
see, usually. the fourth dimension. but
the mathematical sense begins where
the human sense fails.
Even our most elementary problems