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    Re: Delta-T
    From: George Huxtable
    Date: 2004 Dec 4, 00:00 +0000

    In reply to my posting about the long-term unpredictability of planetary
    orbits, Alex replied
    >...I thought you were still talking about Tycho Brahe or anything else of
    >"practical importance".
    Well, it depends on who it might be of practical importance to. Not to us,
    nor to many generations ahead. But the time-scales involved in significant
    changes to planetary orbits, such as that of the Earth, are not long in
    comparison with the time-scales for biological evolutionary changes here on
    Earth. Such orbital changes may well have a long-term effect on the future
    viability of our species, and may have made a significant impact on
    evolution in the past.
    But in terms of celestial navigation, not of "practical importance". Nor
    was Tycho Brahe's contribution.
    contact George Huxtable by email at george---.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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