World’s smallest atomic clock goes on sale

A matchbook-sized atomic clock 100 times smaller than its commercial predecessors has been created by a team of researchers at Symmetricom Inc. Draper Laboratory and Sandia National Laboratories.

The portable Chip Scale Atomic Clock (CSAC) - only about 1.5 inches on a side and less than a half-inch in depth - also requires 100 times less power than its predecessors. Instead of 10 watts, it uses only 100 milliwatts.

''It's the difference between lugging around a device powered by a car battery and one powered by two AA batteries,'' said Sandia lead investigator Darwin Serkland.

Despite common implications of the word ''atomic,'' the clock does not use radioactivity as an energy source. Instead, where an old-fashioned alarm clock uses a spring-powered series of gears to tick off seconds, a CSAC counts the frequency of electromagnetic waves emitted by cesium atoms struck by a tiny laser beam to determine the passage of time. (There's a fuller, more interesting description of this process below.)

Still, given that the CSAC does not actually display the time of day - measured in millionths of a second, its passage would defy the ability of human eyes to read it - why would anyone want it?

The clock's uses are, indeed, specialized. Miners far underground or divers engaged in deep-sea explorations, blocked by natural barriers from GPS signals, could plan precise operations with remote colleagues who also had atomic clocks, because their timing would deviate from each other by less than one millionth of a second in a day.