Exactitude

Fifty-three years ago there was a physics instructor at U. S. Naval Academy who developed a great curiosity. He wanted desperately to know just how fast light travels. He was then a young man of 23. Now he is 76 and has become a veritable epicure in curiosity. He demands the very tittles of exactness.

In his 53 years of experiment Professor Albert Abraham Michelson, now the world famed physicist of Chicago University, has little by little whittled away the inaccuracies surrounding the calculated speed of light. In 1926, he set up two reflecting mirrors of his own design on Mount Wilson and San Antonio Peak near Pasadena, Calif. The U. S. Geodetic Survey measured the distance between his two instruments, about 22 miles, and assured him that its figure was accurate within one-third of an inch. Playing light from mirror, he timed the 44-mile round trip, calculated the speed of light at 186,284 mi. per sec.

Last week he announced another experiment--to try to time the speed of light still more accurately. He will build a pipeline one mile long and three feet in diameter. From it he will exhaust the air, leaving a vacuum. In a vacuum it will not be necessary to make corrections for temperature, pressure and moisture, as it was in the open air. Once more he will set up his mirrors, allow a beam of light to make five round trips through the pipe and time it for the ten-mile trip.

He explained: "I am well satisfied with the accuracy of the present figures of the speed of light, but the vacuum may enable a further correction of one or two parts in a million, and, at any event, will serve as a check on the previous method."