[time-nuts] Pendulums & Atomic Clocks & Gravity

Tom Van Baak tvb at LeapSecond.com
Sat May 26 22:51:31 EDT 2007

> As far as I can tell the Russian Fedchenko observatory clock was the ultimate. 
>    About 2 milliseconds per day.

Yes, word on the street is that the Russian Fedchenko did
even better than Western pendulum clocks by Shortt, Riefler,
and Leroy. Possibly because it well-addressed the issue of 
circular error. Perhaps because rusky fiscal-irrelevant invar
was much better than capitalist make-a-profit invar. If you're
interested I have, somewhere, nice long-term phase plots of 
a Fedchenko clock. I also know a couple of people that own
them, although I'm not sure how many surviving Fedchenko's
are in operational condition.

I don't know how many time nuts are interested in this but
you need to realize that the first hint that the Earth itself was
an unstable timekeeper came, not from quartz or atomic
oscillators, but from these astronomical pendulum clocks.

When two or three Shortt's or Fedchenko's agreed better
than earth-based stellar observations the only rational
conclusion was that mechanical clocks were more stable
than the earth itself. This had far-reaching philosophical
and metrological implications. And it is much related to the
origin of the leap second, in case you wondered why I'm
interested in it. See also:


More information about the time-nuts mailing list