TAI zone?

[Andy Lipscomb]

>>The latter is more complicated, given that the orbit and rotational speed of the ball in question weren't set up with
>>reference to the energy level difference between the two hyperfine levels of the ground state of the cesium-133 atom,
>>and that both change over time.

>*both*?  Surely, sir, you jest.  

>I have a Cs atom calibrated by BIPM, preserved in a bottle of snake oil, which it breaks my heart to sell, but I have
>an old mother ... 

Both the orbit and the rotational speed, I think he might mean...