NATURE OF COSMIC RAYS.

Manawatu Standard, Volume LIII, Issue 63, 10 February 1933, Page 5

NATURE OF COSMIC RAYS.

NOTED SCIENTISTS DIFFER. A wide difference of belief about the nature of the cosmic rays was shown in a discussion before the American Association for the Advancement of Science by two noted physicists, Dr. Arthur H. Compton and Dr. Robert H. Millikan, both of whom gave the results of extensive studies made during the year. Dr. Compton reported that the instruments used in attempts to measure cosmic rays made at 89 stations in the northern and southern hemispheres, both at sea level and at heights up to 20,000 ft., _ recorded everywhere a rain of electrified particles. These particles, apparently broken atoms, were more intense at high altitudes than at sea level, and more numerous near the Poles than near the Equator. Probably they are the cosmic rays. In Dr. Millikan’s view these particles are only a secondary effect of the rays —atoms of the atmosphere smashed and set flying by real cosmic rays, which are themselves the “bullets” of light called photons. He agreed with Dr. Compton that all the instruments recorded only particles, rays being invisible and no instruments having been yet devised that could detect them. He differed from Dr. Compton, however, in his report that the rays showed no such changes in intensity from the Tropics towards the Poles, as was noted by Dr. Compton. Dr. Millikan argued that, because atoms in a block of lead were split by the impact of a cosmic ray, this cosmic ray must have been a photon because it entered the lend unseen. If it had been an electron,- ns Dr. Compton’s theory would suppose, it would have been detected by a track left in a cloud of vapour. According to Dr. Compton’s hypothesis, the photons, which Dr. Millikan believes he had detected, might not be cosmic rays at all, but only “local photons” or particles split off from atoms of the air a few miles above the earth by the impact of the real cosmic rays in the form of electrons. After this splitting occurred a mixture of photons and electrons would speed toward the earth and the photons, because of their great penetrating power, might bo mistaken for cosmic rays.