Science: A Question of Time

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Star Treks. This Einsteinian concept of "time contraction," if proved to be a real physical effect, eventually could help man conquer the vast distances to the stars. Aging more slowly at high speeds, astronauts could make trips that would take longer than their normal terrestrial life spans. If their spacecraft traveled close to the speed of light (186,000 miles per sec.), as a matter of fact, so little time would elapse for the astronauts compared with the experience of people back on earth that they might return home to meet their own great-grandchildren.

Some theorists have refused to accept such fantastic consequences of the clock paradox and have sought to disprove it. They have even used the paradox in an effort to challenge all of relativity; for Einstein himself admitted that if only one part of his theory proved wrong, its whole finely structured mathematical edifice would crumble. In the September issue of Physics Today, Physicist Mendel Sachs takes a different tack. He contends that the Einstein theory and equations are correct, but that Einstein misinterpreted the equations in stating the clock paradox. A relativity theorist himself at the State University of New York in Buffalo, Sachs argues that the equations suggest that the difference between a clock aboard a spacecraft and one on the ground is observational rather than real. It is, he says, an effect similar to that experienced by an observer on a station platform who hears a change in pitch of the whistle of a passing train—when no change has actually occurred.

Sachs will thus have more than normal interest in the outcome of the experiment by Hafele and Keating, who by week's end returned to Washington from their eastbound flight. During their 58-hr. 5-min. trip, they had been kept busy taking temperature, pressure and magnetic readings inside the plane; any variations that could affect the experiment will have to be calculated into the results. It will take them another flight, scheduled for this week, and perhaps a month of complex analysis of their data before they come to any firm conclusions. But they are hopeful that the final results will help resolve one of the most enduring debates in 20th century physics.

* Actually, the final figures may be different since the scientists must take into account the varying speeds, altitudes and flight paths of their different planes.

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