RIDDLE OF THE COSMIC RAY

Hawera Star, Volume LIII, 30 September 1933, Page 11

RIDDLE OF THE COSMIC RAY

rpHE study of cosmic rays has beep described as "unique in modern physics for the minuteness of the phenomena, the delicacy of ithe observation's, the adventurous excursions of the observers, the subtlety of the anialyisies, and the grandeur of the inferences.” _ It is believed that these rays are bringing some important messages, writes Mr Arthur H. Compton, of the University of Chicago, in the "Scientific Amdricami.” Perhaps they are 'explaining how the world has evolved, or perhaps they are conveying nows of the innermost structure of the atomic nucleus. All attempts are now being made to decode this 'message, adds Mr ■Ooimptom, and he "How ean cosmic rays bo detected and measured? One way is to measure the electrical conductivity ox air. iu our experiments we use a steel bomb, about four inches in diameter, filled with air or argon gas under high pressure. The cosmic rays make this gas slightly conducting, and the tiny electric current which flow® through J » measured with a sensitive deetno-meter. The rays from radium and other radioactive materials also affect the gas inside this bomb. So we surround the bomb with a heavy shed of lead to keep out the undesixed’ rays from the radium.

“If such a bomb, protected by lead, is carried into a deep tunnel, the coim?r.Sed air inside is almost a perfect non-conductor of electricity. On It'he ground outside the . tunnel there r., however, a measurable current through

Amazing Powers of Penetration

. the gas, due to the cosmic rays. If the apparatus is carried to the top of a mountain, or high up in a balloon, the current flowing through the gas rapidly increases, showing that the rayis are much stronger at high altitudes. Another means of detecting the cosmic rays is the so-called ‘counting tube.’ This also consists of a bulb filled with gas, which is made conducting by the cosmic rays. But now, instead of measuring the current with an electrometer, it is amplified a million million times or more and passed through a loud speaker. Each time a ray passes through the counting tube d sudden ‘plop’ is heard from the loud speaker. A« ordinarily' operated in the laboratory some 10 to 50 such impulses pdr minute are heard. Most of these are due to cosmic ravs, coming from outside o± the earth, no one knows how many thousands or millions of light years a/way. One of the most distinctive charaicteristies of these rays is their _remarkable penetrating .power. _ We ttenk otf X-rays as very penetrating, wui they not pass through a man’s hand, or even through Ms body? Yet while rt takas about lin, of water to absorb naUX of a beam of X-rays, or Ift of vrater to absorb half of the gamma ray® from radium, it requires some 20ft. of water to absorb half of a cosmic rays beam. That is how It happens that these rays pass right through the heavy bffianket of air that forms our atmosphere, through the roof and upper floors of a building, and affect our instruments surrounded by heavy shields of lead in the laboratory.”