Re: Civil Time decision tree v0.5

From: Rob Seaman <seaman_at_noao.edu>
Date: Wed, 17 Aug 2005 16:45:51 -0700

The sound of crickets. Either folks are on vacation - or folks think
the decision tree roughly outlined as v0.5 is perfect as it is - or
folks think the whole thing is silly. A few comments will hopefully
provoke some interest:

> I) Existence [Adopt an international (or intergalactic) civil time
> standard?]
> A) yes
> B) no
>
> II) Multiplicity [How many standards?]
> A) one
> B) many

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?

> 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. Traveling between planets - or simply telecommuting like
the MER project team - is likely to always require resolving
incompatible clocks as per the "Martian jet lag" discussion.

> IV) Synchronization [with underlying time standard(s)]

For the moment, I don't want to refocus on the too-familiar issues of
Solar Time versus Atomic Time - we all know where we each stand.
Rather perhaps we could examine the question of what distinguishes
civil time from underlying time standards. I suspect that part of the
friction is over who "owns" the definition of UTC. Astronomers are
likely to regard this as a flavor of Universal Time and thus
equivalent to its own fundamental time standard (over which they are
perhaps understandably proprietary). Timekeepers perhaps regard UTC
as simply an expedient way to reconcile Universal Time and Atomic
Time and therefore as simply a synonym for civil time itself. The
fundamental standards in this latter case would be UT1 and TAI.

Ignoring issues for the moment of what the "best" standard would be,
one might suggest that a possible way to identify a consensus
position on a change to civil time would be to relayer it upon a
completely different current standard (e.g., GPS) or on a newly
defined fundamental standard (e.g., TI), either of which would be
carefully chosen to avoid such baggage. UTC, and before it, GMT,
have an extremely long history of usage. Removing them completely
from the equation might provide both astronomers and timekeepers
(only two of the many stakeholding communities, of course) enough
common ground to build a new civil time infrastructure.

In the absence of a consensus for change, the default decision should
remain, of course, to retain the current standard.

Rob Seaman
National Optical Astronomy Observatory
Received on Wed Aug 17 2005 - 16:49:02 PDT