Gravitating Toward Einstein

The General Theory of Relativity that Albert Einstein published in 1916 pro posed nothing less than an all-embrac ing theory of gravity. Over the years, as scientists devised increasingly subtle experiments to test Einstein's predictions, the General Theory withstood all challenges But no one was able to check Einstein's conclusion that massive celestial bodies accelerating in space or undergoing cataclysmic events should give off gravitational radiation, a form of energy similar to radio waves that travels at the speed of light. This week, after more than a decade of work, University of Maryland Physicist Joseph Weber offered the first convincing physical evidence of that elusive gravitational energy.

To make his measurements, Weber and his colleagues built a gravitational wave detector of extraordinary sensitivity that can record extremely small stresses and strains caused in its own structure by the impact of gravity waves from distant space. But, Weber had to be able to differentiate gravity-wave pat terns from those caused by any terrestrial movements or electromagnetic disturbances, to say nothing of the constant activity of the detector's own atoms.

Similar Peaks. To make this delicate distinction, Weber set up identical instruments at his headquarters in Col lege Park, Md., and at the Argonne National Laboratory, outside Chicago, nearly 700 miles away. As expected, the wave patterns traced out were at first random and dissimilar because the readings were being taken so far apart.

Then, for a brief instant last December, the waves suddenly jumped into remarkably similar, simultaneous peaks.

During the next seven months, the parallel movements occurred about 40 more times. The only possible explanation for those multiple coincidences, wrote Weber in a report to Physical Review Let ters, a publication of the American Physical Society, was that the instruments had actually recorded gravity waves from far out in space.

Although he has not yet pinpointed the origin of the waves, Weber thinks that they may have come from some massive object in the Milky Way. Weber says that by measuring gravity waves, astronomers may be able to explore still other fascinating mysteries of space.

By building larger detectors, for example, astronomers could learn more about pulsars. If they are actually spinning neutron stars, as many astronomers have come to believe, they could be producing the kind of gravitational effect postulated by Einstein. The detection of gravity waves, Weber adds, gives man "a new set of windows for the study of the universe."

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