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I think the question of whether we can make a Nautical
Almanach for a hundred of thousands years or for a million
years is out of the scope of this list, but because George seems
to be highly interested in this subject, I can tell what I know.

The question of stability of Solar system is unsolved.
I mean we just do not know whether it is stable or not.
There were several attempts to prove stability mathematically
(beginning from XVIII century to some recent works) but they
failed. But there is also no mathematical demonstration that
it is unstable, not speaking of "chaotic".

There were indeed some recent works claiming that instability
was demonstrated by calculation (over the period of hundreds
of millions to billions of years). I read some
of these papers published in "Science" and "Nature" in 1990-s.
But the
validity of these
calculations was disputed by mathematicians.
From which I made a
conclusion
that reliable numerical solution for such long times is impossible.

For what period of time we can really make a reliable almanach,
I don't know. But surely for several thousands years.

I also think that the motion of the main planets
(say, those 4 used in navigation) can be predicted for much
longer periods than the motion of the Moon, which is
by far the most complicated.

Alex.

   

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