PROBING COSMIC RAY MYSTERY

Hawera Star, Volume LIII, 10 June 1933, Page 11

PROBING COSMIC RAY MYSTERY

rpHB exact nature of cosmic rays is 1 not yet known. It is not even absolutely certain whether they are cosmi'cj originating not in the earth’s atmosphere, but in outer space. The true nature of these rays will however, be the remarkable invention made by Mr P. M. S. Blackett and Mr C. Oceialini of the Cavendish Laboratory at Cambridge who have described in the .-journal “Nature,”' the apparatus they iia-v-e devised for making cosmic rays, or the effects of cosmic rays, photograph themselves. Skobelzyn, three years _ ago, showed that particles moving with enormous energy may be detected in the earth’s atmosphere. Whether these particles are themselves cosmic rays or whether they are produced by cosmic rays is not yet decided. But the invention of a machine which automatically goes off when one of these swift particles enters it means that a great increase in efficiency in the observation of \ cosmic ray effects has now been obJk ,• tained. These swift particles discharge the apparatus about once in every two minutes, Hitherto they or their trabks were photographed by taking photographs continuously. Thus, thousands of photographs had to be taken in order to got a few suitable tracks. This neat and ingenious apparatus, which photographs only when a particle goes through it, is typical of the Cavendish experimental style.

Use of New Cavendish Apparatus

Mr Blackett takes pairs of photographs of each track so that its dilection in space may be exactly determined. Of 100 such pairs of photographs he found 50 showed tracks of particles, which, if they were electron's, would exceed 500,000,000 volts. In connection with this it is interesting to remark that Heisenberg has boon able to explain many of the properties of cosmic rays on the assumption tliat tliey are electrons ’travelling under a pressure of about 1,000,000,000 volts. Besides the 59 pairs of photographs showing the high-speed tracks, 17 showed multiple tracks and 24 showed no tracks. Thus (Mr Blackett’s machine appears to be working with an efficiency of no less than 70 per cent. It is remarkable that at the first attempt his apparatus should catch the effects of cosmic rays so efficiently. The energy of the flying particles is determined from the deviation they suffer in a magnetic field.

The research on cosmic rays is now being pursued by many workers throughout the world. The existence of a penetrating radiation was suspected from experiments made by McLennan and Rutherford, in 1903. About 3 910 Kilhorster showed that the penetrating radiation increased in intensity higher up in the atmosphere. This so dried to prove, that it entered the earth’s atmosphere from outside, and the notion of rays from cosmic space arose.