The New York herald., 1921-04-19
EINSTEIN TALKS
AT CITY COLLEGE
Explains the Genesis of His
Theory of Relatively to
Crowded Hall.
THREE MORE LECTURES
Refers to Development
Through Nicholson, Lo-
rentz and Minkowski.
THREE MORE LECTURES
OFFERS LITTLE FORMULA
Length, Time and Mass Re-
fcrred to Unchanging We
locity of Light.

PROT. Albert Einstem deItUored yeS-
terddy afternoon the first Of series
Of four lectures at the College OF the
city Of Nelc York, speaking on "The
Special Theory Of Reldtipity." The
NEW York HERALD requested Or. Bcn-
yaneiit Hdrro,r, associate iR bio-c1tem-
istry al the College OF Physicians and
Surgeons OF Colilm bid University. to
report the lecture. d.. Horro1e is The
author OF "From Einstein TO Nclcton." !"
The report is stbjoined.
ny DIR. BENJAMIN HARROW.
How many are familiar with differ
entail and integral calculus? was the
first question asked by Prof. Albert Elm
stein at the commencement OF the first
of four lectures or the theory OF rels-
.ivity that he is giving at the College
Of The City Of New York; OF the several
hundred that crowded The lecture hall
fully 50 per cent. responded in the af-
.irmative.
That is very encouraging said the
professor. "and now we shall proceed"
Ana proceed he did, making use of his
native German TO an extent which
brought visible distress to many in the
audience.
In his first lecture rrof. Einstein con-
fined himself entirely 10 the special or
earlier part of tho theory Of relativitv.
Though the tools of the mathematician
were in evidence, the derivation Of the
several equations was reserved for to-
days performance.
THE equations without the deriva-
tions are more than enough for me-.
exclaimed a professor OF chemistry TO
me after the lecture.
Prof. Enstein first referred to the
celebrated Nicholson experiment, which
was undertaken. In the hope of proving
that there is an ether in space. With
an ether pervading space, ray of light
travelling a certain distance UP and
down would have taken longer time
for its journey than one travelling an
equal distance across and back. Michel
son could detect no difference.
Explanation or Lorentz.
To explain that anomalous result and
at the same time 10 five further indi-
rect evidence Of the presence Of this
ether in space. Lorentz, the Dutch
physicist. suggested that matter con-
tracts in the direction Of it's motion and
pensate for the longer time taken for
light to travel the up and down distance.
Lorentz's view, II accepted. rot only
strengthens the argument in favor OF the
ether but also explains why motion
through the ether. and the ether itself,
can never be detected
At sthat stage. early in 1905. Einstcin
Joined the merry party. let Us ignore
the ether altogether" he suggested "and
let US see where this will lead US With
the help Of mathematical machinery
which viii be revealed 70 us in detail
to-day. Einstein, using two well recog-
nzed postulates. arrived al exactly the
same contraction formula that Lorentz
did. with this advantage over Lorentz.
that neither the question OF tho ether
nor the nature of matter entered the
derivation OF the Einsteiu formula. Elm
stems two postulates aEc based on the
constancy Of the. velocity OF ight. and
also on the fact that We vannot detect
absolute but only relative motion.
Einstein's equations lead to eour mo-
mentous conclusions In the frst place.
two observers in relative motion viii
not agree In their measurements Of time
interval necessary Tor a gwen event TO
take place. Secondly. the measurement
OF time is no vaguer than that OF length.
Thirdly. neither is the mass of n body
fxed quantity, for il varies with the
velocity Of the body And finally. mat
ter and energy are merely different
names for the same fundamental entity.
An Innocent Little Formula.
To make the subject a little bit more
confusing 10 the layInan and a little
bit more onlightcning 70 the mathe-
matically inclined reader. II may be
mentioned that the chief factor in the
I,orentz- E,instein equations Is little
formula which IL put into words, reads
like this:
'srhe square root Of one minus V
squared over squared
That innocent little formula leads 70
this inevitable conclusion: That so long
as the velocity of an object. say the
earth is small as compared TO tho
velocity OF light. length, time and mass
viii seem TO change little. II at all:
when. however the velocity OF an object
becomes appreciable as compared to
that Of liEht-as in the velocity of
electrons shot out from radium--t this
no longer holds true. Another interest
ing fact that formula brings out is that
no velocity greater than that Of light
Il possible. otherwise the equation
would lead to negative number
which Is therefore imaginary and has
no reality.
The next step In the development OF
the theory of relatively We really owe
20 Minkowski. whose phrase time and
space by themselves are mere shadows"
has since become classical. To MInkowslsi
we owe the development OF the time
space" conception. wherein time merely
figures as a fourth coordinate. the other
three being the usual three-space. or
three-dimensional coordinates. Minkow-
ski showed how. by the application Of a
four dimensional analysis. we get
equations which are more universally
applicable than those OF the three dlmen-
sional type.
But Of this and more, more, much
more, IS promised to-day.