Ultimate Particles

Yale last week stood forth on the busy field of subatomic exploration with a new conception of the neutron. The week prior, Cambridge had brought into the field evidence of "positrons" (positive electrons).

The neutron, since Cambridge's Dr. James Chadwick discovered it last year (TIME, March 7, 1932), has been considered an electrically inert combination of proton and electron. Two pictures of the combination have developed: 1) the heavy proton and the light electron bound together much like a dumbbell; 2) the electron hugging the proton like an onion peel. Such combinations should knock protons in certain definite directions. With a camera he invented, Yale's Franz N. D. Kurie showed that the behavior of protons recoiling from neutrons did not follow the calculated patterns. Only deduction tenable was that the neutron is an elementary, indivisible particle of matter comparable to the proton and electron.

Cambridge's "positron" is a particle of positive electricity no heavier than the particle of negative electricity called the electron. Protons, heretofore considered the smallest unit of positive electricity, weigh 1,850 times as much as electrons. Cambridge's Paul Adrien Maurice Dirac long ago declared that mathematical necessities require the existence of light-weight protons. Last year Caltech's Carl David Anderson noticed some ion tracks which implied impacts from Theorist Dirac's light protons. Before the Royal Society last fortnight, Dr. P. M. S. Blackett, 35, tall, pale member of Lord Rutherford's platoon of physicists who work in Cambridge's Cavendish's Laboratory, produced 500 pictures of positive particles answering the same description. Dr. Anderson in Pasadena suggested the term "positron," with electron converted to "negatron" to emphasize the distinction.

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