Examples include the daily movement of the sun across the sky, a swinging pendulum or vibrating crystal. But it also means the aluminum ion clock is not a good candidate for measuring magnetic and electrical fields or temperature, whereas other NIST atomic clocks have greater sensitivity to those quantities.Īll clocks must have a regular, constant or repetitive process or action to mark off equal increments of time. This insensitivity is highly desirable for the best timekeeping results. For example, the aluminum ion logic clock's world-record timekeeping performance was due in part to this clock's insensitivity to changes in magnetic fields, electrical fields, and temperature. The suitability of various clocks for different applications can also be seen in recent history. Additional new types of atomic clocks not yet envisioned might also be developed.
Meanwhile, the research has already produced spinoff innovations, such as the world's most stable lasers, and more such discoveries can be expected. All these clocks are likely to continue improving, and leadership in performance may continue to shift back and forth in the future. Now NIST clocks based on cold neutral atoms in optical lattices have taken the lead after lagging substantially behind for many years. Then a NIST clock based on a single aluminum ion and quantum computing technologies surged ahead. Several years ago, an experimental NIST clock based on a single ion (electrically charged atom) of mercury was the world record holder for precision (see definitions below). The unpredictability of research outcomes can be seen in recent history. NIST invests in a number of atomic clock technologies because the results of scientific research are unpredictable, and because different clocks are suited for different applications. Today's precision timekeeping technologies rely on several different types of atomic clocks, but in the future, an even wider range of clocks might be used, each optimized for different applications. In next-generation atomic clocks, the frequency changes are measured to such a fine degree that the clocks could become world-class instruments for measuring gravity, magnetic and electrical fields, force, motion, temperature and many other quantities. In today's conventional atomic clocks, those frequency changes are errors to be tightly controlled. But the new atomic clocks are becoming so extraordinarily precise that they are likely also to be used as extremely sensitive detectors for many things besides time.įor example, the frequency ("ticking rate") of atomic clocks is altered slightly by gravity, magnetic fields, electrical fields, force, motion, temperature and other phenomena. Improved atomic clocks obviously will benefit widely used technologies that have long relied on precision timekeeping, such as communications and GPS positioning. These clocks may enable new technologies, and one or more of them might become future time standards. These experimental clocks have been improving rapidly, and each offers different advantages. Meanwhile, NIST scientists have been developing next-generation atomic clocks based on a variety of different atoms, including mercury, aluminum, ytterbium, strontium and calcium. civilian time and frequency standard based on cesium, keeps time to within 1 second in about 100 million years as of 2013. The NIST-F1 fountain clock, the current U.S. The second is defined as exactly 9,192,631,770 oscillations or cycles of this cesium atom resonant frequency. Atomic time standards have been in use since 1967, when one of the cesium atom's natural frequencies was selected by an international committee as the basis for the international unit of time, the "SI second".
The atomic clock was invented at NIST in 1949 (then the National Bureau of Standards), and atomic clocks quickly became more accurate than any other timekeeping technologies.Ītomic clocks began to have notable impacts on other technologies about 20 years later. NIST's first atomic beam clock, 1949, was based on an ammonia-regulated quartz crystal oscillator and had a precision of about one part in 20 million.Ītomic clocks keep time based on the natural oscillations (or frequencies) of atoms, which are much more stable and accurate than any mechanical devices.