出典:Wikipedia
出典:『Wikipedia』 (2011/05/28 06:48 UTC 版)
An atomic clock is a clock that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element. Atomic clocks are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, to control the frequency of television broadcasts, and in global navigation satellite systems such as GPS.
a clock
a sun-dial
a day-clock
a timepiece that shows the time of day
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procathedral
heliozoans
a globule