New Clock Will Lead to More Accurate Measure of Time

John Roach
for National Geographic News
July 13, 2001

Never be late again.

Scientists who specialize in the accuracy of time have created a new kind of clock—an optical atomic clock—that "ticks" one million billion times per second and is at least 20 times more stable than current atomic clocks that are based on microwaves.

The technological breakthrough is like acquiring a fine-grain view of nature, say its creators.

"The analog might be in looking at a biologic sample through a magnifying glass versus looking at it through a microscope," said Scott Diddams, a member of the team conducting optical clock research at the U.S. National Institute of Standards and Technology (NIST) in Boulder, Colorado.

Although it will take several decades for the technology to be tested and accepted by the international timekeeping community, optical atomic clocks have the potential to be 100 to 1,000 times more accurate than current microwave atomic clocks.

NIST and other research laboratories make and maintain the most precise clocks in the world against which less accurate clocks, such as wristwatches and alarm clocks, can be calibrated.

As modern technological demands increase, the master clock that sets the international time standard needs to stay ahead of the curve.

Ticks and Tocks

All clocks consist of two basic components: a device called an oscillator, which produces periodic events, or ticks, and a mechanism for counting and displaying the ticks. In a traditional clock, such as a grandfather clock, a pendulum oscillates back and forth to produce ticks, while a set of gears drives a pair of hands that count and display the ticks.

Atomic clocks add a third component: a point of reference against which to synchronize the clock. Because the energy levels of atoms are thought to be constant, atomic clocks use specific atoms as the point of reference.

In microwave atomic clocks, the well-defined resonance of a cesium atom is the reference point. The oscillator is a microwave source, and high-speed electronics count and display the time.

Because cesium atoms provide a stable reference point no matter what the temperature or air pressure is, atomic clocks have become today's official timekeepers.

The NIST's optical atomic clock works according to the same principle as a microwave atomic clock, but at a much faster rate.

Continued on Next Page >>


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