[time-nuts] UTC and leap seconds

[Mike S]

At 06:03 AM 6/11/2010, Poul-Henning Kamp wrote...
>In message <815517.110281276250464575.JavaMail.root at wmail51>, 
>"iovane at inwind.it
>" writes:
> >
> >I was wondering, why we assume that  Earth's rotation is slowing 
> down, instead
> >that clocks are speeding up?
>
>Because we can measure it relative to the position of very distant
>quasars.

I assume you mean use a clock to measure the earth's rotation, using 
quasars as a positional reference. That's circular logic.

One answer to the question is that earth clocks agree closely with 
external time sources, like pulsars, and that we can explain why the 
earth slows (tidal forces, etc.), but there is no theoretical basis to 
explain how cesium atoms would vibrate (yes, that's oversimplified) 
faster and faster.