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Moving Clock Found to Run Slower Than Stationary One

From The American Horologist and Jeweler magazine, October, 1938

Moving Clock Found to Run Slower Than Stationary One

Bell Laboratories Scientist Confirms 40-Year-Old Theory

A famous theory of science, announced forty years ago, has at last been confirmed by experiments in the Bell Telephone Laboratories, according to a paper presented by Dr. Herbert E. Ives before a meeting of the National Academy of Sciences in Washington recently. Dr. Ives has shown that a moving clock actually does run slower than one at rest.

So slight is the slowing-down that no speeds available to experimenters when the theory was announced were adequate for a crucial test. But by using as a "clock" the light-giving oscillation of a hydrogen ion, which can be shot down a vacuum tube at a thousand miles a second, it is possible to measure a definite change in the color of the light. That, of course, means a change in the rate of vibration of the atom.

Dr. Ives' apparatus uses a vacuum tube in which there is a small amount of hydrogen. An electric arc breaks down the hydrogen molecules into charged ions.

These are picked up by a high-voltage electric field and brought up to speeds of the order of a thousand miles a second. Looking into the end of the tube, the observer sees these ions approaching him, and by means of a mirror he also sees them apparently receding from him.

If his eyes were sufficiently sensitive to color, he would notice that the receding ones were redder than the approaching ones; this is the Doppler effect, which also makes the horn of an approaching car sound higher pitched than that of a receding car. But as compared with the color of stationary ions, those moving in either direction are redder; that is, they vibrate more slowly. And that is what Fitzgerald, Larmor and Lorentz proposed nearly 40 years agoatomic "clocks" oscillating more slowly as they move through a stationary medium called "the ether." 

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