THE SPEED OF LIGHT.

Dunstan Times, Issue 3383, 18 July 1927, Page 7

THE SPEED OF LIGHT.

The speed of light is 299,700 kilometres per second (180,284 miles per second). This is the final determination for the velocity of light as announced to the National Academy of (Sciences at Philadelphia on November R by Professor A. A. Michelson, of the University of Chicago, and president of the academy.

This figure is the culmination of years of effort on the part of Professor Michelson (says “Science Service”). Ho made his first experiments when a. young officer on duty at the U.S. Naval Academy at Annapolis. Within the past three years he has boon working at the Mount Wilson Observatory, refining the figure for the velocity of light. The most accurately measured base line in the world, about 22 miles long, stretched between Mount Wilson and Mount San Antonio, was used. Professor Michelson projected a powerful light through a narrow slit into a mirror, which was spinning at the rate of about 30,000 revolutions per minute, which in turn projected it on a redacting apparatus at the far station. The reflector returned the light to the original source. With, an accurate knowledge of the rate at which the mirror is revolving and the distance between the two stations the velocity of light can lie calculated. This summer Dr Michelson made five series of observations with revolving faces, having 8, 12 and .10 facets, and all observations showed “remarkable agreement,” which allowed the announcement of a final figure. In 1887 the first of Hertz's papers establishing the similarity between light and electric, waves was presented before the Berlin Academy of Sciences. “In 1873,” wrote Mills in “The Heal] ties of Modern Science,” “Maxwell, who was a prominent physicist, highly trained in the use of mathematical tools, announced that light was an electrical phenomenon, and travelled as an electromagnetic -wave. He further stated the possibility of there being other electromagnetic waves, which would not produce the effect of light, but would travel just as light waves tra vc I.

"In 1887 Hertz verified this prophecy of Maxwell, and announced the discovery of electro-magnetic waves. Hertz studied their properties or characteristics. lie showed how they could he produced, how they travelled through the walks of buildings, and were not affected by obstacles which would completely obstruct the passage of light, and also how they could he detected, siiu-e they do not affect tile eyes as <loes light.”