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When we want to quickly figure out how something works, we often consult the experts at HowStuffWorks. To zero in on a specific answer, we use the search box on the site's front page. For this query, we found a concise column, a longer, more detailed article, and links to other resources about the world's most accurate timepiece. Clocks consist of two elements: a "ticker" (referred to as an oscillator or resonator in tech-speak) that "measures" an unvarying unit of time, and a mechanism to accumulate and communicate the discrete time units in seconds, minutes, and hours. In recent history,
clocks have used the oscillation of a pendulum, the resonant frequency of a quartz crystal, or the cycle of the electric power lines to track the passing seconds. Global Positioning System (GPS) satellites, the Internet, and other telecommunication networks require precision timekeeping that is unaffected by the Earth's rotation. For these applications, an atomic clock offers accuracy that's out of this world. Atomic clocks are based on the following principle: ...atoms (and molecules) have resonances; each chemical element and compound absorbs and emits electromagnetic radiation at its own characteristic frequencies. These resonances are inherently stable over time and space. Cesium 133 is the
element used in the most accurate atomic clocks, like those located at the National Institute of Standards and Technology (NIST) in Boulder, Colorado; the U.S. Naval Observatory, in Washington, D.C.; and the International Bureau of Weights and Measures in Paris, France. Cesium oscillates at a frequency of approximately one nine-billionth of a second. The state-of-the-art NIST-F1 Cesium Fountain Atomic Clock uses the fountain-like movement of atoms to measure time. Diagrams and a movie
illustrate a more detailed technical explanation. NIST also operates a specialized radio station that transmits the time codes received by radio-controlled clocks. Just want to synchronize the time on your computer to official U.S. time? NIST has the software to help.
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