• U.S.

Science: More Light on Light

2 minute read

Almost as long as there have been scientists, man has been trying to measure the speed of light. In 1638, Galileo stationed a brace of lantern bearers on hilltops and tried to time their flashes—with no luck at all. Since then, Danes, Frenchmen and Americans have succeeded in narrowing down the figure to generally accepted modern-day figures, but the search for greater precision still goes on.

As scientists refined their measurement skills, they realized more and more the significance of light’s speed. By the time it was established that all electromagnetic waves move at the velocity of light in a vacuum, that speed was recognized as a constant of nature. Einstein’s theories hold that nothing in the universe can ever move faster. The constant (represented by the letter c) appears in his famous equation E=mc², the formula for the conversion of mass into energy, which was grimly proven July 16, 1945 in the first atomic blast at Alamogordo, N. Mex.

Now scientists working under Dr. Kenneth M. Evenson at the National Bureau of Standards in Boulder, Colo., have measured c with new accuracy. Working with a laser beam—pure light of a single frequency—they have refined the measurement of light’s speed to 186,282.3960 miles per second. In effect they reduced the accepted speed by roughly 144 feet per second. This may not seem important to camera fans worrying about exposure, or yachtsmen timing a flashing light on a dark night. But it could make a considerable difference to scientists calculating the precise landing site of an astronaut, or astronomers studying immense celestial distances which are measured in light years. Most important of all, man will have a more exact knowledge of the limits and the dimensions of the universe of which he occupies so small a part.

More Must-Reads from TIME

Contact us at letters@time.com