Evening star., 1937-12-11
Millikan
Continued From First Page.)

unknown. The most powerful of them
are propelled by forces as great as
1900, 100000 volts. Since they are
hitting the earth night and day they
cannot come from the sun and must
result from some unknown phenome-
non taking place in the stars or in
outer space, possibly from the creation
of the elements themselves out of
energy dispersed by the heavenly
bodies.
Hypothesis in Doubt.
Various considerations have led
physicists generally to believe that
the most highly penetrating of these
rays are electrons, shot with tre-
mendous speed and power through
space, knocking outer electrons off
atoms through which they pass, and
sometimes making direct hits on the
nuclei of atoms, thus causing Sec
ondary electron showers. Dr. Milli-
kan himself never has been entirely
satisfied with this hypothesis. One
difficulty has been the so-called Bethe-
Heitler theory which states, in gen.
eral, that the greater the voltage pro-
pelling an electron the relatively
shorter the distance it will travel
through matter. 1t can be stated, a
Carnegie physicist explained, that the
higher the energy the more it is alb
sorbed per inch of path traversed.
Mathematical considerations showed
that even an electron with a push of
17,000,0 100000 volts behind it would
have relatively little chance of passing
through the earth's atmosphere The
observed penetrations have been ex-
planned away by the unproven as
sumption that the Bethe- -Heitler hy-
pothesis, which holds for all energies
within experimental limits, does not
hold true for very high energies.
DR.. Millikan, by highly specialized
type of observations made on two
sides of the earth-at San Antonio,
Tex, and Madras, India, was able
to prove, he reports. that the Bethe-
Heitler theory actually held true for
cosmic rays covering the entire range
from about 1000, ,Oo0, 900 to II ,O00, ,000,-
Voo titCLfO Oh VOLS.
Certain of Newness.
THE results show" he reported,
that contrary to the most approved
of preceding assumptions, electrons
even of that huge energy, instead of
being highly penetrating are so rap
idly absorbed by nuclear collisions in
the upper layers of the atmosphere
that they reach their maximum of
ionization by the time they have got
but one-twentieth of the way through
it, and at half the way through they
have retained not more than one
sixteenth of their ionizing power.
Thus our experiments show that the
observed, penetrating particles are not
electrons. They must be either pro-
tons or else particles of intermediate
mass between electrons and protons.
If they art protons, since they are
both positive and negative in sign, a
negative proton has been discovered.
In any case a new particle has come
to light
From other considerations, DR.. Mil
likan reported, the cosmic radiation as
it comes from outer space and hits the
outer atmosphere of the earth may
consist either of electrons or photons,
which are corpuscles of radiation. But
when they strike the atoms of the
atmosphere they knock out of them
showers of these new particles. which
do not exist except in atoms which
have undergone high energy collision
and absorption. He says:
THE energy of the photon is trans
ferred to penetrating particle, which
then acts merely as a. connecting link
to carry cosmic ray energy further
down"
Evidence for the x-particle-per-
haps identical with the assumed mega
tive proton-was obtained by two OF
DR.. Millikan's fellow workers at Pasa-
dena, Drs. Anderson and Neddermeyer
who measured the loss OF energy OF
cosmic rays in their passage through
q bar OF platinum. Altogether they
studied SIS tracks of particles with
energies of from 10000, 900 to 500,-
100000 electron volts behind them
Certain OF these tracks, they found
did not obey the Bethe- Heitler tl1eor,
and hence could not be, electrons.
They then took 1000 photographs o.
cosmic rays passing through a cloue
chamber, where a visible track is pro.
duced due to the electrical effect. Sew.
eral heavily ionizng particles wer,
found, all but one Of which could b,
ascribed to protons. A single one
however, was found which seemed t.
have a mass only one-half that of {
proton. This could only be particl,
unlike anything ever before known il
the universe.
The discovery of this new particle
if both turn out finally to be the sam,
1T ng--is likely to have far-reachin,
effects on current theories Of th,
physical structure OF creation. Up I.
4