[LEAPSECS] Leap seconds, precision time, and technical progress

Daniel R. Tobias dan at tobias.name
Sun Dec 26 18:09:24 EST 2010

On 26 Dec 2010 at 21:35, Poul-Henning Kamp wrote:

> In message <4D17A98A.7090104 at yahoo.com>, Michael Deckers writes:


> > The astronomical phenomenon that is used for determining

> > the phase of UTC is the rotation of the Earth, and this

> > is no longer one of the "fundamental vehicles" for

> > synchronization because it is (currently) neither

> > constant nor predictable to a sufficient degree.


> Nor is it, for that matter, "universal" in any relevant meaning

> of the word.

Probably "Terrestrial Time" would be more logical as a descriptor,
but that's already been taken for yet another different time scale
not tied to the solar cycle.

Already, with various unmanned missions on Mars (and perhaps
eventually manned missions or even permanent colonies), the need for
a Martian time has been seen, and while they're still at a rather
early stage of standardization of this without a full-fledged Martian
calendar system (they just use standards that differ from mission to
mission, with no consistently-kept numbering system), they do use
Martian varieties of hours, minutes, and seconds that are a different
length from the Earthly ones in order to fit in the Martian solar
day. Eventually, if they do establish a complete timekeeping system
that's maintained in the long run, they'd have to tackle the question
of whether the Martian seconds are "rubber" to match the solar day
even if it varies (does the Martian day vary in the manner Earth's
does?), or defined as a fixed length and possibly necessitating leap
seconds from time to time. At any rate, that system would be
distinct from that of Earth, and the same would be true for whatever
other planets might have human activity in the future. Eventually
there might be lots of different solar-based time scales for
different planets, tied to calendar systems based on the local day
and year, and they'd all be distinct from the "universal" scientific
timekeeping which would be based on atomic clocks. At that point it
would be most logical for Earth to also have a solar-based system,
and it would only be for historical reasons that the universal system
used by mankind galaxy-wide happened to have units that approximate a
fraction of the Earthly cycle.

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