[tz] [PROPOSED] Improve leapseconds support

Steve Allen sla at ucolick.org
Sun Oct 7 00:14:08 UTC 2018

On Sat 2018-10-06T16:42:23-0700 Paul Eggert hath writ:
> Steve Allen wrote:
> > This is definitely true in this era.  Assuming (bad thing to do) that
> > rotation of the crust does not undergo another strong deceleration the
> > two dates per year should be enough for the next 40 years.
> My eyeballing of the "extrapolated long-term trend" of Figure 18 of
> Stephenson et al. 2016 says that 2 leap seconds per year should be enough
> until 2300 or so.

The red band is the long term average, and two leap seconds per year
is an excess LOD of about 5.4 ms, so that shows around year 2100.

The green curve should be taken with a huge grain of salt because none
of the decadal fluctuations are mapped prior to the 1800s.
Huber, P.J. J Geodesy (2006) 80: 283.
Huber argued that it is possible that the fluctuations of the green
curve are entirely a stochastic artifact of the poor sampling afforded
by the old eclipse records.

Look carefully at the measured LOD and see that 100 years ago the
earth was spinning slower than it is now, and slower than it was in
1972.  The decadal fluctuations demonstrate that the torques caused by
weather in the core/mantle boundary are huge by comparison to any
geophysics beside impact with another planet.

If another large decadal fluctuation slowdown happens there could be
more than two leap seconds per year during this century.

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