Paul said:On Mon, 25 Oct 2004 11:46:14 +0000 (UTC), [email hidden] (Chris
Malcolm) wrote:
Quoted message said:Quoted message said:And the reason for doing that is because the new
system of atomic clockery was *more* accurate.
Quoted message said:But keeps on having to be adjusted to conform with GMT!
You've misunderstood what goes on. GMT is time calibrated to the
earth's rotation, and has been abandoned, nobody is using it
anymore. It has been replaced by a close approximation, properly
called UTC, which is calibrated with respect to atomic clockery, and
adjusted by leap seconds to stop more than a large fraction of a
second discrepancy with real GMT. In other words, UTC is an
approximation to GMT accurate to about a second, but which has
supplanted GMT because it is more accurate for purposes where very
accurate measurement is required, and for timekeeping purposes which
used to rely on GMT, and need its synchronisation with the earth's
rotation, accuracy to the nearst second is good enough.
This isn't just a scientific curiosity. We're using technology now
which needs UTC, and couldn't be made to work with GMT, e.g. GPS.
--
Chris Malcolm [email hidden] +44 (0)131 651 3445 DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]