Re: Civil Time decision tree v0.5

From: Steve Allen <sla_at_UCOLICK.ORG>
Date: Wed, 17 Aug 2005 17:05:13 -0700

On Wed 2005-08-17T16:45:51 -0700, Rob Seaman hath writ:
> I suspect that we are all agreed that a single civil time standard
> should exist. The question of multiplicity is one of drawing narrow
> distinctions. Many people use devices and systems that rely on non-
> UTC time scales, for instance, GPS receivers. Is GPS a second civil
> time standard already?

To answer other than one for a civil time standard in the vicinity of
earth would be to set the clock back to where it was before the 1884
International Meridian Conference. Some of the point of that
conference was to produce a convention for syncronizing human activity
on the (then relatively new) trans-oceanic telegraphic cables.

> >III) Locale
> > A) restricted to Earth [projects or users, not necessarily
> >hardware]
> > B) other than Earth [e.g., Martian rovers]
> > B) Solar system scope
> > C) truly Universal
> Personally, I think each planet is likely to require a separate
> standard.

The spacetime metric adopted by the IAU does not have enough terms in
it to generalize to a solar-system wide coordinate system with full
precision of current atomic clocks in the vicinity of rotating,
gravitating bodies. In a rough sense the metric was designed to
permit the definition of a self-consistent coordinate frame out to
around twice the geostationary radius.

In the broader sense, even a solar-system barycentric coordinate frame
is suspect at the level measurable by current atomic clocks, and that
is part of the motivation for the various international scientific
unions recommending the establishement of a pulsar-based time scale.

In a still broader sense, there is no meaning for a universal
coordinate time scale. Every observer experiences a proper time
peculiar to the local environment.

For the foreseeable future, each planet will have its own coordinate
time scale.

Steve Allen                 <>                WGS-84 (GPS)
UCO/Lick Observatory        Natural Sciences II, Room 165    Lat  +36.99858
University of California    Voice: +1 831 459 3046           Lng -122.06014
Santa Cruz, CA 95064     Hgt +250 m
Received on Wed Aug 17 2005 - 17:05:30 PDT

This archive was generated by hypermail 2.3.0 : Sat Sep 04 2010 - 09:44:54 PDT