Cosmic Rays

Abstract

PROf. P. M. S. BLACKETT took “Cosmic Rays” as the subject of the thirtieth Kelvin Lecture which he delivered before the Institution of Electrical En-gineers on Thursday, April 27. He gave a resume of what had been done to discover the nature of these mysterious rays, from their properties. As a rule, engineers consider natural phenomena first of all to find out some possible utility for them. In addition, Prof. Blackett stimulated the imagination of his audience to consider all manner of possible consequences which might arise from the bombardment of the earth from outer space by some twenty particles per minute at astronomical values of electron volts. The effects of cosmic rays can be obtained, shown by experiment and recorded photographically without much difficulty and with quite simple apparatus, but calculation of these effects depends upon equations which, although easily written down, can only be approximately solved with great labour. The labour can be lightened by the use of calculating machines invented by engineers, but it is a lengthy operation. There is little exact knowledge about these rays and it is assumed that they are due to radiation from the extra-solar universe. Interesting accounts were given of the attempts that had been made on these rays by researches in the upper atmosphere, by investigations on the surface of the earth and by experiments below its crust. He said that, in the last case, the necessary apparatus had been installed in one of the underground platforms of the Holborn station of the London Passenger Transport Board, but it was found that the symmetry of the readings was effected by the presence overhead of the tunnel which carries the electric trams below Kingsway.