Anti-Proton

Theoretical physicists have insisted for years that anti-protons--protons with a negative electrical charge--would eventually be found. But their theories also told them that antiprotons, though stable in a vacuum, cannot exist in contact with ordinary matter. As soon as one of them encounters a normal proton, both it and the proton it hits will vanish in a flash of energy. This makes antiprotons hard to find in nature, which is loaded with ordinary protons lying in wait to destroy them. It is like searching for living insects in a bottle of DDT.

Two Bev. into Matter. Last week a team of physicists at the University of California told how they created antiprotons artificially and kept them alive long enough to identify them. Drs. Owen Chamberlain, Emilio Segre, Clyde Wiegand and Thomas Ypsilantis worked with Berkeley's Bevatron, a particle accelerator that was built by the Atomic Energy Commission for just such jobs. It can shoot a proton so fast that it carries 6.2 Bev. (billion electron volts) of energy. Physicists had figured that when a proton of this power hits a neutron, it will create a new proton and an antiproton. In such "pair formation," about two Bev. of energy is turned into matter. This is the reverse of the action in atomic bombs, where matter turns into energy.

The Berkeley scientists turned their 6.2 Bev. proton beam on a copper target. From it emerged a secondary beam of sub-atomic debris (protons, neutrons, mesons, etc.) which presumably contained antiprotons. To prove that it did, the scientists shot the secondary beam into a "maze" (of magnetic fields and mass-or speed-measuring instruments) which only a particle with the anti-proton's properties could pass through. A few of the particles did pass through it, leaping every hurdle and checking in triumphantly at the far end. None lived very long, of course. After a fraction of a second, each antiproton encountered a proton or a neutron, and each destroyed the other.

Antiprotons have no practical use, for the present at least, but scientists are always delighted when one of their basic theories proves so neatly correct. They are sure, too, that the study of antiprotons and experiments made with them will lead to new discoveries.

Anti-Matter. As a result of the new discovery, it is now theoretically possible to create anti-hydrogen. The atoms of ordinary hydrogen have a proton in their centers with a negative electron revolving around it. Anti-hydrogen would have an antiproton and a positron (positive electron). Both these "anti" particles are now available, but since anti-hydrogen cannot live in peace with ordinary matter, it will be hard to create and even harder to preserve for more than a few millionths of a second.

To build up larger atoms of antimatter will require anti-neutrons. Neutrons have no electric charge, but they have magnetic properties that would have to be reversed to put them in the anti category. It may be possible to create them, perhaps by bombarding some other particle with antiprotons, and this is one of the stunts that the Berkeley scientists intend to try soon.

Antimatter is a favorite subject with science fiction writers, who like to write about inhabited planets made entirely of it. A poignant moment comes when the beautiful anti-girl explodes like an H-bomb on kissing a man from Earth. These fantasies are built on the theory that isolated parts of the universe, such as distant galaxies, may be built of antimatter.

Scientists cannot disprove this theory, but they consider it unlikely. It is probable that the whole universe had some common origin, and should, therefore, be made of the same kind of matter. The question might be settled, thinks Dr. Segre, one of the antiproton creators, if astronomers' instruments were sensitive enough to observe the magnetic properties of stars in distant galaxies.

Dr. Segre believes that antimatter should be stable so long as it stays with its own kind. "Of course," he says, "nobody has seen any antimatter. As far as physics is concerned, the antiworld would be identical with our world. An anti-egg would taste like an ordinary egg if you, too, were an anti-man."

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