[tz] Fwd: Bulletin C number 58

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Sat Jul 27 07:59:14 UTC 2019

On 2019-07-26 22:49, Steve Allen wrote:
> On Fri 2019-07-26T23:16:08-0400 David Patte hath writ:
>> For my products I use an algorithm (Meeus; Astronomical Algorithms 1998) to
>> 'predict' deltaT into the future. Does anyone have a good source for a more
>> recent algorithm that takes into account IERS values since 1998?
> at the moment we seem to be pretty close to "Matsakis parabolic"
> https://www.ucolick.org/~sla/leapsecs/year2100.html
> but there are no guarantees

We all know what a shock there was after the last break in regular leap second
additions, and given short memories in popular development circles, expect
similar reactions next year or whenever the next addition happens.

Are there any sources providing pointers to explanations of recent changes in
EOP parameters and their likely cause, or info about likely reasons for (rather
than factors affecting) the current (and earlier) period(s) of reductions in
dUT1 change?

https://en.wikipedia.org/wiki/ΔT#References has an interesting comment:
Stephenson, F. R. & Morrison, L.V. "Long-term fluctuations in the Earth's
rotation: 700 BC to AD 1990". Philosophical Transactions of the Royal Society of
London, Series A 351 (1995) 165-202. https://www.jstor.org/stable/54464.
"Includes evidence that the 'growth' in Delta-T is being modified by an
oscillation with a wavelength around 1500 years; if that is true, then during
the next few centuries Delta-T values will increase more slowly than is envisaged."

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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