Anti-Proton?

Normal matter is organized into tight little worlds--atoms--with positive protons in their nuclei and negative electrons revolving around them. There is also a homeless waif, the positron (positive electron), that seems to have no place in this orderly scheme. Born in atomic catastrophes, it lives only until it hits a normal electron. Then the two "annihilate" one another, turning into gamma rays.

Some physicists have reasoned that since positrons exist, there should be negative protons (anti-protons), around which positrons could revolve to form atoms of "reversed matter." Last week a group at Massachusetts Institute of Technology, headed by Professor Bruno Rossi, reported that a strange intruder from space had entered one of its cosmic-ray cloud chambers. When it first showed up, it behaved like a rather slow-moving heavy particle. Then it hit a brass plate in the apparatus and set off three powerful electron "cascades" that appeared to have been started by high-energy gamma rays.

Professor Rossi believes that the original particle may have been an antiproton that hit a normal proton in the brass plate and annihilated it. Apparently the encounter produced nothing but energy, and it produced too much (about 1.3 billion electron-volts) to be accounted for by any other process.

No one knows where such an outlaw particle could have come from. One colorful theory holds that somewhere in the universe there may be stars or whole galaxies made of reversed matter. From them escape antiprotons that wander through space, perhaps for billions of years, until they hit normal protons (as in Professor Rossi's brass plate) and are annihilated.

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