Neutretto

The most important question for physics to answer is: What is matter made of? A glass of water or a chinch bug or a copper coin is composed of molecules. The molecules are built of atoms. Twenty years ago the ancient Greek notion persisted that atoms were indivisible. Then Ernest Rutherford of England split nitrogen atoms with atomic bullets from radium. Seven years ago physicists were willing to analyze all the matter in the universe in terms of two parts of the atom: protons and electrons.

Then, in quick succession two more particles were found, the neutron and the positron. Moreover, two particles whose existence has never been experimentally demonstrated cropped up in the lucubrations of theorists: the negative proton and the neutrino. Some of these little entities were charged with positive electricity, some with negative; some were electrically neutral or inert. Some were "heavy" or massive in relation to others--the ratio being about that of a ton to a pound. The physicists wound up. for the time being, with a nicely balanced table of discovered and hypothetical basic particles of matter, as follows:

Plus Minns Neutral

Heavy Proton (Negative proton) Neutron

Light Positron Electron (Neutrino)

At California Institute of Technology a clever, conscientious young physicist named Carl David Anderson found anomalies in cosmic-ray behavior which convinced him that, in the upper air particles were being created which were lighter than protons but heavier than electrons, and both positively and negatively charged (TIME, Nov. 29, 1937). Drs. Jabez Curry Street and Edward Carl Stevenson of Harvard also vouched for the existence of this queer entity. At first there seemed to be no place for it in the physical scheme. Then it was recalled that the Japanese physicist, Yukawa, had postulated the existence of just such a thing to help explain energy exchanges in the atomic nucleus. In honor of Yukawa, there is a tendency in Europe to call the particles yukons. The name barytron ("heavy particle") is gaining favor in the U. S. At the American Physical Society's convention in Chicago last week, barytrons were a popular subject of discussion.

Meanwhile Walther Heitler, co-author of a famed theory of electron absorption in gases, had called into theoretical being still another particle, the neutretto--similar in mass to the barytron but having no electrical charge. The existence of neutrettos has not been proved. But in Chicago last week Physicist Francis R. Shonka of the University of Chicago reported high-altitude cosmic-ray experiments, in which he juggled various arrangements of Geiger-Muller cosmic-ray counters and selective lead shields, obtained evidence of something which he took to be electrically neutral particles of high penetrating power.

"This," he said, "suggests their identification with the neutrettos . . . postulated by Heitler." So the physical family of fundamental particles last week stood as follows:

Plus Minns Neutral Heavy Proton (Negative proton) Neutron Intermediate Positive barytron Negative barytron (Neutretto) Light Positron Electron (Neutrino)

As long ago as 1931, Britain's Physicist Charles Galton Darwin, grandson of the late Charles Darwin, compared physics to "a mother who has given birth to several healthy children, but has not yet recovered sufficiently to know what is going to hap pen next." More closely now than ever does physics resemble a bewildered and bewildering Old Woman Who Lived in a Shoe.

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