FOM: lagrangian pebbles

[Martin Davis]

At 04:26 PM 3/18/98 -0700, Reuben Hersh wrote:

>
>Why do I believe astronomers can "predict" the motions of the
>planets far in the past?  Or your cute thing with Lagrange's
>pebbles?  Because I believe nature is in some senses orderly,
>behaving in the past in a way like it behaves  today.
>
>So if Newton's law seems good today, we can believe it was
>good at least in the recent past (astronomically speaking.)
>That means it was a good description of the behaviour of the
>nine planets.  It was an appropriate adjective.  
>
>But the mathematical subject of potential theory (the 3 dimensional
>gravitational potential) as existing apart from, independently of
>physical phenomena, was created by Newton and his successors.  It
>did not exist even in Neanderthal times, let alone in the Jurassic.
>
But then how can we justify the mathematics that derives the rules of
planetary motion from Newton's laws applying to jurassic times?

Martin