NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Long-term orbit predictability: was [Nav-l] Delta-T
From: Alexandre Eremenko
Date: 2004 Dec 5, 13:23 -0500
From: Alexandre Eremenko
Date: 2004 Dec 5, 13:23 -0500
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.