[time-nuts] Why 9,192,631,770 ??

[Tom Van Baak]

> Who decided 9,192,631,770 cycles of 'light' constitute one second?  I don't
> mean who the person was, or which company or institution or when. 
> 
> I ask, why not ...771 cycles ...or ...669 cycles????

Hi Don,

It was the result of 4 astronomical measurements made over several years.
    9,192,631,761
    9,192,631,767
    9,192,631,772
    9,192,631,780
You take the mean and get 9,192,631,770 +/- 20. That's how the atomic
second was "calibrated" against the astronomical second. Clearly the
number is only a rough estimate; the earth is a poor timekeeper.

Details here:
<http://www.leapsecond.com/history/1958-PhysRev-v1-n3-Markowitz-Hall-Essen-Parry.pdf>

/tvb