IT was fun while it lasted, but the prospect of building antigravity machines with spinning gyroscopes is no more. Refined experiments have eliminated the apparent weight loss of spinning gyros that Hideo Hayasaka and Sakae Takeuchi of Tohoku University in Sendal, Japan, reported last December.
If real, the effect ``could overturn the foundations of classical physics and could find practical applications in space travel,'' noted University of Edinburgh mechanical engineer S.H. Salter in a skeptical review of the Japanese claim published last month in Nature. Dr. Salter's main point was that small imperfections in the gyros and related effects could produce spurious ``antigravity'' effects.
That now appears to be the case. Yet, while space travel buffs may be disappointed, the scientific work has not been in vain. It gives new insight into gryoscope experiments. And it provides a timely example of how to do speculative physics right.
The experimenters reported their work through normal scientific communication channels - in this case, Physical Review Letters. There were no hurried press conferences to announce half-baked findings. No one urged governments to put money into trying to develop useful devices while the scientific uncertainties were still being worked out. This stands in telling contrast to the media and legal circus that swirled around the University of Utah report a year ago of the still highly uncertain possibility of producing hydrogen fusion reactions at room temperature.
The Japanese scientists weighed spinning gyros in sensitive balances. They found an apparent weight loss when gyros spin in one direction and no loss when they spin the other way. The loss was small - only 11 milligrams for a 175-gram rotor spinning at 13,000 revolutions per minute, for example. Yet the effect - if real - challenged basic physics.
Up to now, classical physics has easily explained gyros in terms of momentum conservation. This requires that all the forces within the gyro system counterbalance each other. There should be no net force, no antigravity effect. No such force has appeared. James Faller and colleagues at the US National Institute of Standards and Technology in Boulder, Colo, and T.J. Quinn and A. Picard at the International Bureau of Weights and Measures in Paris put gyros to exacting tests. They report - respectively in Physical Review Letters and in Nature - that the apparent antigravity force disappears when exacting care is taken.
It's easy to go overboard when something as sensational as antigravity is tentatively reported by reputable scientists who have tried to do careful research. In spite of the scientists' caution, gullible people did rise to the temptation. The American Physical Society, which publishes Physical Review Letters, was flooded with telephone calls from all over the world. Some callers asserted priority for the idea. Some said they had patented it. Others noted that alien ``flying-saucer'' craft use gyro lift.
It pays to be skeptical of tentative findings that seem to challenge basic physics. Meanwhile, we can be grateful for the care the scientists themselves took to respect the integrity of the traditional scientific communication process.