Eureka: The Ultimate Clock

By Stephen Cass | August 20, 2008 7:01 pm

Screen capture from Euraka Season Three, Episode FourLast night’s episode of Eureka was terrific, easily one of the show’s best, with some amazing performances from the cast. If you haven’t seen the episode, or you haven’t yet watched Eureka at all, get over to the Sci Fi channel’s website and and catch it. The plot revolved around problems with the flow of time—and where you have time, you have clocks.

The clock in question is a new addition to Eureka’s research labs, capable of measuring slices of time less than one billionth of one millionth of a second (one femtosecond). The technically-inclined characters seem quite excited by it, as they should—in the real world, maintaining a grip on the exact passage of time is an essential and technologically-intensive activity. Our ability to measure time accurately is the key to many other measurements–for example, the meter is defined in terms of how far a photon can travel in one second.

Historically, the most accurate way to measure time was to use astronomy. The second was defined as 1/86,400th of the length of time it took the earth to rotate once on its axis. This worked fine in the era when clockwork meant little gears and springs, but eventually clocks were built that were accurate enough to detect the fact that the Earth’s rotation is ever-so-slightly, but continually, slowing down. Rather than have seconds grow slowly longer as the years went by, the second was redefined in terms of the best clock then available, the so-called atomic clocks, which rely on measuring the frequency of specific type of microwave radiation emitted by cesium atoms. The second is now defined as “the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.”

A network of government laboratories all over the world together average the measurement of hundreds of atomic clocks to produce International Atomic Time, the ultimate reference against which all other clocks are calibrated. Because the Earth is slowing, it’s necessary to occasionally introduce leap-seconds into these calibrations, so that noon stills falls when the sun is at its zenith in the sky.

But scientists are trying to push past even the incredible accuracy of traditional atomic clocks, striving to measure smaller and smaller slices of time. The seriously-awesome people at the U.S. National Institute of Standards and Technology have created the most accurate atomic clock ever, a so-called Quantum Fountain that measures time so accurately, it would take 60 million years of operation to be out just one second.

MORE ABOUT: atomic clock, Eureka, NIST

Comments (3)

  1. Cesium and TAI and NIST are just right for robots navigating planes to perfect landings, but humans who want to know a good time for soccer practice want to know when the sun is up. Both kinds of time are important, but there is a big difference between them.


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar