Evening star., 1935-03-14
STARS, MEN AND ATOMS
Notebook of Science Progress in Field,
Laboratory and Study.
nv TUONlS uENPy
BY THOMAS r. HENRY.

One must look to the great island
universes-the extra -galactic nebulae
which are scattered uniformly through
space at distances ranging upward
from million light years away from
the earth-for the source of the bonn
bardment of coSmic rays, the most
penetrating radiation known, which
will go through the thickest walls like
water through a sieve.
Such is the conclusion Of DR..
Thomas H. Johnson, research associ-
ate of the Carnegie Institution Of
washington, who has been studying
the intensity of these rays in differ
ent latitudes in the hope that their
variations might shed some light on
their nature. This has been one OF
the chief activities Of the inStitution's
Cosmic Ray Committee, headed by DR..
Arthur H. Compton of the University
of Chicago.
THE total energy falling upon the
earth's surface in the form of cosmic
radiation" DR.. Johnson says, lis about
-thousandth that of starlight and
about one-billionth that of sunlight.
The energy of a single ray surpaSses
that of any other form of radiation,
and the rays are easily detected, one
at time. If We had suitable nerve
responses we would be conscious of
about Is shots per second passing
through some part of the body.
THE most discriminating method
for analysis of cosmic radiation con-
sists In passing the rays through a
magnetic field and studying the de-
Elections. In cloud chamber magnetic
analysis the primary radiation is con-
fused with secondary radiations. To
investigate primary rays by this
method an apparatus which works out
side the earth's atmosphere is needed,
and the magnetic field of the earth
itself is just such an apparatus. Ten
billion-volt rays are powerful enough
to reach the earth only within a very
small angle close to the western hori-
zon. Sixty -billion-volt rays are re-
quired to reach the Equator from all
directions"
DR.. Johnson's studies indicate that
the particles of which cosmic rays are
constituted are practically all posi-
lively charged and hence cannot be
ordinary electrons, which are mega
lively charged.
Hence" he says. comes the ques-
ton Of what the unbalanced positive
rays are. Three possibilities have been
suggested. The first is the positive
electron, a particle Of very nearly zero
mass and unit positive charge. Rays
Of this type are often produced when
high-energy gamma rays of protons
collide with atomic nuclei, and they
also are generated by certain types of
spontaneous nuclear disintegrations
Though considerably more rare than
their negative counterparts, they could
possibly be present In the cosmic radi-
alton.
1.-THE second possibility is the posi-
tive proton, the nucleus of the more
common form Of hydrogen. Protons
occur In large numbers In stars and
in the interstellar regions and are
likely candidates. The third possibil-
ity Is the alpha particle, or helium
nucleus, which also occurs abundantly
throughout the universe. The double
charge carried by these particles and
the corresponding rapid loss Of energy
In traversing matter would seem to
put them out Of the picture as far as
sea level radiation Is concerned
though they might well be present in
the higher atmosphere. At sea level,
and up to the tops of mountains, the
principal candidates for the rays are
thus the proton and the positive elec-
tron."
In the light Of his investigations up
to the present, DR.. johnson concludes,
the proton is the more probable con-