Mighty Mesons

Russian nuclear physicists announced a discovery last week, the first they have made since the war (or been allowed to talk about). Physicists P. I. Lukirsky and N. A. Perfilov told the Academy of Sciences of the U.S.S.R. that they knew what happened to negative mesons: the powerful little particles struck atomic nuclei and died while breaking them up. Trumpeted S. I. Vavilov, president of the Academy, "This possibly begins an altogether new chapter in the physics of the atomic nucleus." U.S. physicists applauded mildly, while awaiting more information.

Mesons are subnuclear particles formed when cosmic rays from outer space hit the atmosphere. In mass, mesons are intermediate between electrons and protons. In charge, they can be either positive or negative. The positive mesons disintegrate after a millionth of a second or so, turning mostly into energy (a gamma ray).

What happens to the negative mesons is unknown, but it has long been suspected that they are absorbed by atomic nuclei. This would be natural enough, for nuclei are positive, and so would have a strong attraction for negative mesons.

Tracked to the Grave. The two Russians studied microscopic tracks of free silver which mesons had made on photographic films (probably exposed at high altitudes, where cosmic ray effects are strongest). Their authorized, translated report is far from clear, but apparently they found what they were looking for in the sensitive emulsion: groups of short lines arranged like a star or a chicken-track. Each of these, they said, was an X which marked the spot where a negative meson had murdered an atomic nucleus.

When a negative meson hit a nucleus, they theorized, its mass turned into energy. The added energy made the nucleus break into smaller particles, which flew apart and traced the chicken-track lines.

All this, U.S. physicists agreed, was not directly connected with "atomic energy for military purposes." It was background research. But mesons are close to the innermost problem: how to turn mass wholly into energy. A few pounds of mesons (if obtainable) would release more energy than 10,000 atomic bombs.

At present the only source of mesons is cosmic rays, which rain alike on the U.S. and the U.S.S.R. But the new-type atom-smashers, now building on many a U.S. campus, may produce more of them soon.

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