[LEAPSECS] future access to solar time?

[Seaman, Robert Lewis - (rseaman)]

Whatever they do to poor old UTC and by extension to the concept of Universal Time as the modern realization of Greenwich Mean Time, atomic time and solar time will continue to be separate kinds of time scales, both of which are necessary for diverse engineering requirements for civil timekeeping, as well as for technical applications.

“Ceasing leap seconds” is an incoherently stated goal since there already are timescales without leaps. The plan, rather, is to cease easy access to solar time.

The past 20 years have seen a concerted effort to avoid the 2003 Torino consensus to define a new leap-less time scale. We now have a few years before Universal Time becomes Universal-except-for-solar Time. Could we perhaps spend the time more productively and design a new solar time scale, with-or-without leaps? UT1 as it currently exists is not sufficient. Flat files on 19th-century servers are not sufficient.

Arnold Rots supplied an excellent diagram of timescales in the solar system for a session we held at the 2014 meeting of the American Astronomical Society:

http://hanksville.org/futureofutc/aas223/

None of this complexity goes away by waving a wand to vanish leap seconds. Rather, the green box between UTC and UT1 gets much more complicated, including some fictional future leap-minute or repeated redefinitions of worldwide time zones or some fantasy of the whole world moving to a single time zone.

What are the overall engineering requirements for the multi-timescale system-of-systems? What are the best practices for evaluating possible timekeeping infrastructure and standards in a world that freezes UTC at a static offset from TAI? The concept of operations isn’t limited to how our gill-equipped, web-fingered descendants will implement a leap-hour long after we’re all dead. Maybe they’ll switch to tide-based clocks.

The question is how do we optimize access to the diversity of time scales starting now?

Rob Seaman
Lunar and Planetary Laboratory
University of Arizona
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