Just In Time

A new atomic clock will lose a second, at most, by the year A.D. 1,600,000

How do the professional timekeepers of the world determine, to the precise nanosecond, when a new year begins? They simply consult an atomic clock. And last week, just in time to ring in the new, the Hewlett-Packard Co., of Palo Alto, Calif., unveiled the latest in these meticulous timepieces. Twice as accurate as earlier models, the $54,000 device -- the size of a desktop computer -- will remain reliable to the second for the next 1.6 million years, a period far longer than modern humans have existed.

Who could possibly need such precision? Practically everyone, indirectly at least. Telephone and computer...