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New S.I. and the second definition standard

Physics Asked on November 23, 2021

The new SI defines the second as the hyperfine splitting transition time associated to the frequency of that transition of caesium-133, 9192631770 Hz, that is 12 decimals precision, but…I wonder two things:
-Shouldn’t it be better to define the second with a pulsar ultraprecise measurement (some of the pulsar timing have 17 decimals of precision I believe)?
Could we manage Planck time precision with a good enough “stick”-rule? Surely not with the current SI second definition, does it?

One Answer

No, it would not be better. Pulsars make terrible time standards. First, the period of the fastest pulsar is only about a millisecond. Second, the period measurably increases as they lose rotational energy. Third, the rotation is measurably glitchy rather than steady because there can be random starquakes that change the moment of inertia.

Metrologists know what they are doing!

The Planck time is $5.4times 10^{-44}$ seconds. We are not going be able to measure times to this accuracy in the foreseeable future.

Answered by G. Smith on November 23, 2021

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