Hairline Revolution

The speed of light is science's most revered measuring stick. Among countless other uses, the figure--299,776 kilometers per second--has been built into radars, which measure distances by the time it takes radio waves (traveling at the same speed as light) to cover them.

Commander Carl I. Aslakson of the U.S. Coast and Geodetic Survey recently noted that a long series of land measurements made by shoran (a kind of radar) had gone wrong. Each measurement went wrong by the same small percentage. The measurers checked their instruments, checked their procedures. Everything was shipshape. The only thing left to account for the errors was the speed of light itself. With a guilty feeling and bated breaths, they shaded the sacred figure a tiny bit and made the measurements again. Everything came out exactly right.

Now, admits Dr. Alvin G. McNish of the National Bureau of Standards, the value for the speed of light may have to be changed officially. The new value suggested by Aslakson is 299,792 kilometers per second, a change of one foot in about four miles.

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