Science: Far-Out Waves

When the results of the experiment were first reported last June, many scientists were outspokenly skeptical. University of Maryland Physicist Joseph Weber announced that after more than ten years of effort, he had finally detected the waves that transmit gravitational energy across space. These gravity waves had been postulated by Einstein’s General Theory of Relativity in 1916 but never before observed. Last week Weber converted many of the doubters. Over the last six months, he told the American Physical Society, he had recorded 200 distinct bursts of gravitational radiation from far out in space.

When Weber first detected gravity waves, he was unable to determine where they came from. Now, using his identical devices at College Park, Md., and the Argonne National Laboratory outside Chicago (TIME, June 20), he seems to have closed in on the source. Roughly two-thirds of the waves were noted when the instruments were pointed toward the center of the Milky Way. Furthermore, the detectors picked up the waves even when they were on the opposite side of the earth from the galactic core. That phenomenon seemed to be still another verification of their existence: Einsteinian physics says that gravitational energy, unlike radio or light waves, should be able to pass through the most dense celestial bodies.

Unknown Processes. Physicists are hard pressed to account for the energy needed to generate even one of the outbursts recorded by Weber. They calculate that a wave could be produced by the equivalent of a hydrogen-bomb-like explosion in which twice the mass of the sun was converted entirely into energy. But at the rate that Weber’s gravity waves are occurring, so great a conversion of mass into energy would have long since consumed all of the hundred billion stars in the Milky Way galaxy.

One possible source of gravitational waves is the death of an ancient, massive star after its nuclear fires have burned out. No longer supported by its own radiant energy, it collapses violently, its density and gravitation becoming so great that it crushes itself out of existence. For all practical purposes, according to theory, the star becomes a “black hole” in space. But to produce waves on the scale observed by Weber, some 200 such stars would have to collapse every year in the Milky Way: scientists believe that the actual rate is only about one per year. Weber is equally puzzled. But the waves are there, he insists, “and the theorists will resolve the problem eventually.”