3 Aug
2004
3 Aug
'04
5:06 a.m.
From: "Paul Koning"
<pkoning(a)equallogic.com>
---snip---
For autonomous timekeeping independent of technology, the state of the
art was a second per year or so (that's 10^-8, roughly) around the
early 1900s. First with pendulum clocks (Shortt clock), then around
the 1940s or so crystal clocks came in that could match this. And not
too long after that there came the rubidium (10^-10) and cesium
(10^-14) clocks. Some of that would be found in military gear, I
think (Rb at least, Cs somewhat less likely). Consider GPS
satellites, which have either or both built-in.
paul
Hi
I thought I'd mention that GPS satellites are very precise
but no longer accurate. The world standards like UTC are not
on the same second as used for GPS. I don't recall how
far things have changed but for political and other reasons,
the world time standards have been changing. GPS are still
locked to being relative to particular data and time. Every
one else has had a few leap seconds here and there. There
is a chart someplace on the web that shows how things are.
Dwight