NIST-7 was the
atomic clockAn atomic clock is a type of clock that uses an atomic resonance frequency standard as its timekeeping element. They are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, and to control the frequency of television...
used by the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
from 1993 to 1999. The
caesiumCaesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of , which makes it one of only five metals that are liquid at or near room temperature...
beam clock served as the nation's primary
timeTime is a component of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects...
and frequency standard during that time period, but it has since been replaced with the more accurate
NIST-F1NIST-F1 is a caesium fountain atomic clock that serves as the United States' primary time and frequency standard. As of the summer of 2005, it is so accurate that it will neither gain nor lose one second in more than 80 million years...
, a caesium fountain atomic clock that neither gains nor loses one second in 60 million years.
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NIST-7 was the
atomic clockAn atomic clock is a type of clock that uses an atomic resonance frequency standard as its timekeeping element. They are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, and to control the frequency of television...
used by the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
from 1993 to 1999. The
caesiumCaesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of , which makes it one of only five metals that are liquid at or near room temperature...
beam clock served as the nation's primary
timeTime is a component of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects...
and frequency standard during that time period, but it has since been replaced with the more accurate
NIST-F1NIST-F1 is a caesium fountain atomic clock that serves as the United States' primary time and frequency standard. As of the summer of 2005, it is so accurate that it will neither gain nor lose one second in more than 80 million years...
, a caesium fountain atomic clock that neither gains nor loses one second in 60 million years.
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