WORLD LIGHT

Evening Star, Issue 19800, 25 February 1928, Page 13

WORLD LIGHT

COBHHJ RAYS FROM OUTERMOST SPACE NEW PENETRATING RADIATION A GREAT STEP FORWARD. Professor E. E. Fournier D'Alhe, D.Sc., writes in the ‘Observer’;— _ As Jong ago as 1910 the Swiss physicist Gockei made a balloon ascent of three miles with a delicate electroscope in order to study certain rays which only revealed their presence by their effect on that instrument. To his amazement he found that the higher he ascended the stronger did the rays become. This was one of those observations which might have seemed uninteresting to the lay mind, hat which to the expert conveyed a message of deep significance. Gockei at once suggested that some of the radiation at least might originate beyond tile coniines of the earth. The same view was held by Hess in Austria and Kolhorstcr in Germany, especially after the latter had gone np to live and a-half miles and found the rays at that high altitude seven times as strong as on the ground. After the war the subject received the attention of Professor R. A. Millikan, of Chicago, whoso first experiments induced him to support the theory of his European confreres. Two years ago, however, the cosmic origin of the rays was placed in doubt by experiments of Hoffmann in Germany and Swann in America, whereupon Millikan and G. H. Cameron undertook a new investigation, which established the cosmic; origin of the rays beyond any doubt. EXTREME PENETR ATI VE POWER. The most interesting and significant quality of the new rays is their extreme" power of penetrating matter. Workers with X-rays are now in the habit of protecting themselves against the danger of X-ray dermatitis _ by means oi: lead screens an inch thick. Such screens would be quite useless with these new rays, which are capable of penetrating 16ft of lead and 200 ft of water. Such rays are not produced by any known terrestrial process. Compared, with X-rays the cosmic rays have an extremely short wavelength, estimated at about 5,000 times shorter. Such short waves are very difficult to produce, requiring about sixty million volts, and so far no process has been discovered in the stellar universe by which they could be generated. Millikan suggests that they may originate in the space outside our galactic system, which is contained in the ring of the Milky Way. Far outside the limits of our starry universe there is the region of the spiral nebulae, which are probably worlds in the making. They contain matter in forms ■with which we are not acquainted. They seem to be the workshop in which now worlds are being built up from the raw material, which is transformed or destroyed in the process. The elaborate methods used by Millikan to establish his thesis are clear from a vivid account published in ‘ Nature.’ He endeavored to get into suitable valleys in very high mountains where the rays are three or four times as intense as at sea level, and there to make trustworthy tests on directional effects in cosmic rays, and particularly to see whether the Milky Way is more or less effective than

oilier portions of the sky in sending these rays into the earth. It was also found that there was no difference at all in the value of the readings when the Milky Way was overhead and when it was out of sight, nor could any difference be traced to the position of the sun. NEW IDEAS OF INTERSTELLAR SPACE. There was a time when we thought of interstellar space as a vast emptiness. Astronomers now believe that no part of space is really empty, ft is filled with light and radiation of all kinds, and even of ordinary matter it contains at least one atom per cubic inch. Nor must we consider space cold, for all the particles contained in it are ’moving in all directions with enormous velocities, so that if we define temperature as the mean kinetic energy of agitation of atoms and electrons, the temperature of open space is about fifteen thousand degrees centigrade, which is higher than the surface temperature of the sun and most stars. _ This discovery of the cosmic rays is a great step forward in the exploration of the physical universe and its possibilities. The most penetrating rays hitherto known' were the Gamma-rays. But.' here we have something thirty times more penetrating than anything known before, a form of invisible light which penetrates all space, and the full significance must be left to future generations to realise.