National Institute of Standards and Technology (NIST) has developed the most accurate clocks in the world. Clocks have to be adjusted by _______ ( Added or Subtracted) once in 20 million years.
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Answer:
For a clock updated by radio signals which is sometimes incorrectly called an "atomic clock", see Radio clock. For the clock as a measure for risk of catastrophic destruction, see Doomsday Clock. For other topics, see Atomic Clock (disambiguation).
An atomic clock is a clock device (time standard) that uses a hyperfine transition frequency in the microwave, or electron transition frequency in the optical or ultraviolet region[2] 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 wave frequency of television broadcasts, and in global navigation satellite systems such as GPS.
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