The average wristwatch gains or loses about one second every few days, and undoubtedly, few of us notice the difference. But marking time accurately is crucial to some modern technologies. Atomic clocks–which base their ticks on the oscillations between the nucleus of an atom and its surrounding electrons–enable GPS navigation and ensure the proper timing of space probe launches and landings.

One interesting development in the field deals with making these clocks not more precise but smaller. The goal is to outfit portable devices with atomic clocks, which would enable more-secure wireless communications in consumer handheld devices; faster, error-free data flow
between networked computers; and improved GPS navigation. Currently, most consumer devices count time by the vibrations of quartz crystals. The problem is that their rhythms possess only one thousandth the accuracy of atomic clocks.

In an important step, researchers at the National Institute of Standards and Technology (NIST) in Boulder, Colorado, recently constructed an atomic clock that is approximately the size of a grain of rice. The minuscule setup consumes less than 75 thousandths of a watt, which means it could run on a AA battery. The group says that the clock could start appearing in military GPS receivers within three years and in consumer electronics within six.

The NIST team reduced the timekeeping component of the atomic clock to one hundreth of its former size by sealing vaporized cesium atoms in tiny holes etched in silicon wafers. A miniature laser monitors the frequency of the cesium atoms’ natural vibrations, which should drift by just one second every 300 years.