Abstract
THE twenty-fourth Guthrie Lecture of the Physical Society was delivered by Prof. P. M. S. Blackett on February 26. He took as his subject “Cosmic Rays: Recent Developments”. He said that the most important discovery of recent years in the field of cosmic rays was the realization that the hard or penetrating component of the rays consists of particles of a new type, called mesotrons. This new particle has a mass intermediate between that of the electron and the proton and possesses the peculiar property of being spontaneously unstable. Its average life when at rest is about one millionth of a second, but when moving fast it lives longer—thus giving a nice verification of Einstein's principle of relativity.
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Cosmic Rays. Nature 145, 343–344 (1940). https://doi.org/10.1038/145343c0
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DOI: https://doi.org/10.1038/145343c0