On Sun, Feb 18, 2018 at 2:27 AM, Steve Allen <sla@ucolick.org> wrote:

On Sun 2018-02-18T00:08:25-0700 Brian Inglis hath writ:
> Pretty presumptuous of the IAU to use Universal: they /should/ know better.

Alas, Universal Time of 1928 is a subdivision of the already approved
Universal Day, and that derives from the Victorian-era knowledge of
astronomy and speech patterns of the 1884 International Meridian
Conference. Of regrettable things left over from time-keeping
history, that is not the worst, and the Germans did explicitly avoid
it by choosing Weltzeit as their term.

If Mars denizens decide to choose a single legal time scale that is
constructed from an amalgam of precision time and planetary rotation
then it will also need leaps of some sort. Hopefully they will avoid
the attempt to bend a pre-existing time distribution system into doing
two different time scales, and simply distribute their calendar days
as one of several polynomial offsets from their underlying precision
time and frequency distribution system.

Only if it drifts. Our planet's UT1 drifts with respect to atomic time not
because of measurement errors, but because of internal exchanges of angular momentum,
predominately due to fluid motions in the liquid outer core. Mars has a fluid outer core; whether or not it actually undergoes

significant long period drifts in planetary spin rate remains to be seen. Hopefully, this will be answered by the

Insight lander set to go to Mars at the next launch window.

(Note - Like Viking and Pathfinder, Insight will not have a DSAC, but will use round trip range and Doppler to measure Mars rotation rate with respect

to terrestrial Atomic Time.)

Marshall

--
Steve Allen <sla@ucolick.org> WGS-84 (GPS)
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