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# Is time always a measurement of movement of matter

Is the oscillation of energy levels of caesium in atomic clocks a form of motion (i. e. is time always a measurement of movement of matter)?

asked Gary Wederspahn

Answer:

The Oscillations in cesium clock is not mechanical. the radiation emission frequency between the two hyperfine levels of the atom is used as the standard for measuring time. Due to the fact that the standardisation of time is based on radiations, the atomic clocks are also called radio clocks.

Caesium clocks are the most accurate commercially produced time and frequency standards, and serve as the primary standard for the definition of the second in SI (the metric system). By definition, radiation produced by the transition between the two hyperfine ground states of caesium (in the absence of external influences such as the Earth’s magnetic field) has a frequency of exactly 9,192,631,770 Hz. That value was chosen so that the caesium second equalled, to the limit of human measuring ability in 1960 when it was adopted,

Very accurate clocks can be constructed by locking an electronic oscillator to the frequency of an atomic transition. The frequencies associated with such transitions are so reproducible that the definition of the second is now tied to the frequency associated with a transition in cesium-133:

1 second = 9,192, 631,770 cycles of the standard Cs-133 transition

Ref http://hyperphysics.phy-astr.gsu.edu/hbase/acloc.html#c2

The oscillation in an atomic clock is between the nucleus of an atom and the surrounding electrons. This oscillation is not exactly a parallel to the balance wheel and hairspring of a clockwork watch, but the fact is that both use oscillations to keep track of passing time. The oscillation frequencies within the atom are determined by the mass of the nucleus and the gravity and electrostatic “spring” between the positive charge on the nucleus and the electron cloud surrounding it.

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