Evening star. [volume] (Washington, D.C.) 1854-1972, 1933-07-11


uring cosn,ic rays, Which tMH be
taken up into the stratosphere this
month, and the results he looks TOR.
BY DIR. ROBERT A. MILLIKAN,
and 1923 Nobel Prize Winner for Physics.
Special Dispatch to The Star.
CHICAGO, July IL (NAN.A).-I
have been asked to explain why I am
interested in making accurate physical
measurements in the stratosphere, and
I am very glad to do so. I had to
think that question through very care
fully II years ago, when DR.. s.
of 1922 at the California Institute
of Technology, Pasadena, building our
first self-recording electroscopes to send
up in sounding balloon flights. These
flights were made from Kelly Field
Tex, in April, 1922.
Even these were not the first meas
urements made in the stratosphere. Far
from Though they were the first
made with electroscopes and the first
made for the express purpose of de-
termining the effects of what are now
called cosmic rays at these great
heights.
The precise nature Of these rays is
not here important, though we have
already obtained much excellent evil
dence upon this point. But we are all
agreed that they are the most pene-
trating rays known-fronf to 100
times as penetrating as the hardest rays
heretofore known, which are the gam
ma rays from radioactive substances.
We are also agreed that they manifest
themselves just as do these gamma
rays, by ionizing. or rendering cleo
trically conducting, any gas through
which they pass These cosrlc rays
are not known to be responsible at
bottom for all the electrical effects OBJ
served in our atmosphere below the
from SO to 200 miles above the earths
surface.
Temperature Changes End.
Now the shakespeare, with the Joni
zation Of which by the cosmic rays We
are here concerned, IS that portion of
the upper atmosphere which lies above
an altitude Of 10000 to $4,000 feet, or
to 10 miles. Its distinguishing char
acteristic is that, while up to about this
height the temperature falls rapidly
with increasing elevation until 1t
reaches the very low value OF IS or 10
degrees below zero Fahrenheit-a tenn
perature such as even Minnesota does
from this height on there Is no further
marked drop in temperature with in
creasing altitude.
. In other words, the temperature In
the stratosphere is approximately con-
slant. This is because 1t Is only the
lower part Of our atmosphere that Is
continuously churned by the winds and
by the alternate heating and cooling
Of the earth's surface by the sun.
These facts about the stratosphere were
all well known before our 1922 flights,
for the United States Weather Bureau
and other meteorolog1stS had sent up
in sounding balloons recording ther-
mometerS paragraphs or pressure meas
ures, and hygrometers or moisture
measures.
They had explored the stratosphere
in these particulars, as well as with
respect to wind directions and veloci-
ties clear up to an altitude of % miles,
or $4,000 feet above the earth's sur
face. This is an altitude more than
twice as great as that at which the
stratosphere Is supposed to begin.
Sought Origin Of Rays.
This was precisely what Dr. Bowen
and I set out to do in 1922, the diff
ference between our experiments and
the preceding ones being that we de-
signed and sent up not merely record
ing barometers and thermometers, but
also recording electroscopes. Our par
ticular objective was to md out
whether the intensity Of the cosmic
rays, which are detachable only with
electroscopes or their electrical equiva-
Tents, increased in q geometrical pro-
erosion clear to the top Of the at
mosphere. We estimated then that they
should do so If the rays had their
origin Of the depths.of interstellar space,
beyond the confines Of our atmosphere.
This was the point we were then
trying to settle, and the point that is
now, think, generally conceded. Our
method was to suspend our recording
instruments-which only weighed z
ounces all told, despite the fact that
they included self-recording electro
scopes, barometers and thermometers
with their driving mechanisms and the
recording Photographic filnls-to the
middle Of string Is feet long, each
of which was then fastened to sound
ing balloon inflated with hydrogen to
a diameter Of feet at the earth's
surface.
The two balloons were thus sent up
tied together, the electroscope hangs >,
ing between them. They were expect@
to rise until, a. they expanded moeH
and more in rising TO higher and higher
levels, one Of them burst, and the other
now having to carry the whole load
which had before been supported by
the buoyancy Of the two balloons,
would Of course sink slowly back to
earth, gently bringing down the in
struments.
AS 1t would have been impossible
for us to follow the balloons in their
descent, retrieving our instruments Of
fered some difficulties. We hoped they
would be found by some farmer at
tracted by the 4-foot balloon, and SO
sent back to us. Our hope In this
instance was stimulated by IS award
offered for such return. And the Texas
farmers did not disappoint us in their
eagerness to get IS.
Improved instruments.
These were the first flights Of this
kind, but Just year ago this Summer
DR.. Bowen and I repeated the 1922
experiments, using, however, more SEN
sitive and otherwise much improved
electroscopes. In the same Summer,
also, DR.. Erich Regener made similar
flights in Germany. In both our 1922
a