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Time Keeps Beating... To The Cycle Of An Atom So you want an atomic clock? They are the most accurate form of time keeping out there, and even have a space age name. But what exactly are they, and how much should we pay for one? While we are at it, are they actually worth the money? Atomic clocks are not really so different from any other kind of clock. At the heart of a clock there needs to be something that taps out a really regular rhythm. Then this beat is turned mechanically or digitally into a time we can understand. It doesn't really matter how rapid the beat is, as long as it is regular, but a pendulum clock is set up to tick and tock every second. These old-fashioned clocks are pretty accurate, as long as you remember to keep them wound - a good grandfather clock can be accurate to half a second a day. Sources used for keeping time have expanded past the source used for pendulum clock, which incidentally was first planned by Galileo but never made by the man himself. One example of a modern use of science in clock technology is quartz, which is often used in today's digital watches. When a small electrical current touches quartz, the quartz vibrates at a relatively reliable frequency. Several modern clocks and watches take their cue from quartz and are able to keep time at an accuracy of one-10th of a second each day. This is where a lot of people are happy to stop - hey, who cannot afford to lose a tenth of a second over the 86,400 that we enjoy each day? For most of us it simply isn't an issue, but there are some applications where accuracy is more important (science and navigation for example), which is why the atomic clock was developed. The atomic clock is very, very accurate. The atomic clock is so accurate that the one in the National Institute for Standard and Technology office is off only 30-billionth of a second every year! If you work for this office, you have no excuse for being late. The atomic clock operates through a rhythmic source called cesium that is extremely predictable and precise. The element cesium has a fast but always constant resonant frequency. For those who are interested, the official definition of a second, as established in 1967, is "9 billion, 192 million, 631 thousand 7 hundred and 70 cycles of a cesium atom..." While the NIST atomic clock is a great example of a high-end model, other versions of atomic clocks exist. It's somewhat unlikely that the average person would own one since the hand-held versions cost upward of $20,000. You may be asking by now what are those $20 versions you've seen advertised? These "atomic" clocks and watches aren't really atomic. These clocks and watches make contact with a real atomic clock, read its time by way of radio, and update its time based on that source. This chain of events gives you the advantage of maintaining time through the accuracy of an atomic clock but at a fraction of the price. For most of us, this convenience is mostly academic rather than a necessity since we really don't need to keep time to this degree. Still, there is one advantage to having one of these clocks - you'll never have to fiddle with setting one! That's why so many people buy these clocks and find their price so worthwhile.
This article was posted on November 30, 2005
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