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Re: Delta-T: was [NAV-L] Tycho Brahe Mars oppositions
From: Frank Reed CT
Date: 2004 Dec 4, 00:50 EST
From: Frank Reed CT
Date: 2004 Dec 4, 00:50 EST
Re next July's likely weather, Fred wrote:
"you don't even need to calculate that! But I am curious
how you might."
how you might."
Nothing but the obvious: a few decades of statistics. The point was simply
that the "chaotic" aspect of the weather doesn't mean that the weather is
insane. Short-term weather can be chaotic while long-term climate is predictable
with no contradiction (99.9...% of the time).
And:
"Are the JPL ephemerides similar to the data in the Nautical Almanac,
i.e. tabulated declination and right ascension over time?"
"Are the JPL ephemerides similar to the data in the Nautical Almanac,
i.e. tabulated declination and right ascension over time?"
Yes. Nothing more than that. It's a detailed almanac generated by ultr-high
quality numerical integration carefully matched against known historical data
and modern observations. It's interesting to note that the gravitational effects
of the largest asteroids are significant for accurate predictions of planetary
positions over centuries.
Another little item in the news recently: the climate time scale for the
past few hundred thousand years (IIRC) has recently been revised by numerical
integration of the Earth's orbit (which drives the ice).
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
[ ] Mystic, Connecticut
[X] Chicago, Illinois