Public Release: 

Clock tells time at such speed that reading it becomes challenge

American Association for the Advancement of Science

DENVER, CO - The newest atomic clock is so accurate that its creators theorize that it will neither lose nor gain a second in 4.5 billion years. And, they note that their clock is so promising, it's being tested for use in navigating Global Positioning System satellites and to time minute biological processes, such as protein folding.

But how do you read the time on such a fast clock?

The scientists who designed the new "all-optical-atomic clock" will describe their efforts to count faster and faster things, as the division between "pulses" becomes smaller and smaller.

Using a femtosecond laser to measure time intervals too tiny to be measured in nanoseconds, Scott A. Diddams, a researcher with the National Institute of Standards and Technology in Boulder, CO, and his colleagues were able to keep time with greater precision than can be done with existing atomic clocks, by five orders of magnitude. At the American Association for the Advancement of Science (AAAS) Annual Meeting, the researchers will discuss improvements in the femtosecond laser technology, and their efforts to make counters for the new optical clocks.

The optical clock was made possible by technological advances in measuring optical frequencies, and in capturing and cooling single ions to very low temperatures. The clock uses non-linear optical fibers to generate optical-frequency "combs," which are used to determine frequencies by counting the number of "teeth" in the comb.

"We know the clock is very stable, so now our research is focused on seeing exactly how accurate it is," Diddams said.

Diddams and his colleagues developed the optical clock based on a single trapped mercury ion, and they promise that their research may someday end the reign of the microwave atomic clocks, which use cesium 133 atoms to determine the time. Cesium atoms resonate exactly 9,192,631,770 times per second, when irradiated by a magnetic microwave field. So clocks that adhere to that frequency are extremely accurate. The cesium clock is thought to be able to maintain the correct time for 20 million years-a mere blink of an eye, however, when compared to the 4.5 billion years of accuracy claimed for the optical timekeeper.


Advance interviews possible upon request.

The American Association for the Advancement of Science (AAAS) is the world's largest general scientific society, and publisher of the journal, Science ( AAAS was founded in 1848, and serves some 265 affiliated societies and academies of science, serving 10 million individuals. Science has the largest paid circulation of any peer-reviewed general science journal in the world, with an estimated total readership of one million. The non-profit AAAS ( is open to all and fulfills its mission to "advance science and serve society" through initiatives in science policy; international programs; science education; and more. For the latest research news, log onto EurekAlert!,, the premier science-news Web site, a service of AAAS.

MEDIA NOTE: Diddams and other researchers will participate in a seminar titled, "The Next Generation of Atomic Clocks," during the AAAS Annual Meeting in Denver, at 2:30 p.m. Mountain Time, Friday 14 February, in Room A-110 on the Main Level of the Colorado Convention Center. Press registration is located in Room C-101 of the Colorado Convention Center.

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