For a Second

Time was when a second was I/60th of a minute. Or 1/3600th of an hour. Or 1/86400th of a day. But all of this assumes that the earth takes 24 hours to turn on its axis, which it does not. By scientists' standards, not only is the earth's spin uneven, it is positively erratic. Between 1680 and 1800 the earth slowed down enough to lose 27/100ths of a second. During the 19th century it picked up nearly 31/ lOOths of a second. Then it slowed down again between 1900 and 1920. And lately the giddy old world has been speeding up again.

So, for science's sake, the International Bureau of Weights and Measures will discuss at its meeting in Paris next month the adoption of a new official standard for measuring a second. If a new standard is adopted, a second will be as long as 9,192,631,770 cycles of vibration of a cesium atom. No more, no less. Well, perhaps.

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