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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
    Re next July's likely weather, Fred wrote:
    "you don't even need to calculate that!  But I am curious
    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).
    "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
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