Anti-Meteor?

One exciting new parlor game among physicists is speculating about antimatter in bulk. The earth contains no antimatter because matter and antimatter destroy each other as soon as they meet. Antiparticles are now being created in the laboratory, but the trick of actually building antiatoms is likely to take a long time (TIME, April 21). Meanwhile, those who cherish the laws of symmetry are considering the possibility of distant anti-galaxies in space. Such weird other worlds, balancing galaxies of ordinary matter in the universe, may well exist.

Last week, in the British publication, Nature, Florida State University Physicist Philip J. Wyatt suggested one possible clue: "Of the many craters on the earth known to have been produced by fallen meteors, a few have left no signs of the meteor which caused them, apart from the huge holes created in the earth's crust." Could antimatter possibly have been involved? If so, says Wyatt, "no traces of the meteors would remain, due to the annihilation process." Best example is the huge meteor that blazed over southern Russia on the morning of June 30, 1908. Minutes later it crashed in the forest wastes of central Siberia near the Stony Tunguska River, exploding with a force roughly equivalent to that of a hydrogen bomb.

Though Russian scientists did not reach the site until 1927, they found extraordinary devastation even then over about 62 sq. mi. Yet the several craters are among the smallest known: 30 ft. to 150 ft. wide, only 12 ft. deep. The first visitors found no meteorite fragments to a depth of 30 ft. Another expedition tried again for 13 months in 1930-31, found only minute grains of nickel-iron under one crater.

Physicist Wyatt suggests another search at the site for short-lived radioisotopes, produced by intense gamma radiation, which could prove the point. One theoretical flaw in the argument is that an antimatter meteor ought to explode shortly after whizzing into the earth's atmosphere. Moreover, anti-gravity may be a property of antimatter. Unlike other meteors, which fall into the earth's gravitational field, an antimatter meteor would be repelled. But if antimatter does not have antigravity, an antimatter meteor -- if big enough to survive the annihilation of its surface -- might hit the earth.

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