The Chaotic Rotation of Hyperion

Prof. Peale from UCSB, and Jack Wisdom, then also at Santa Barbara, proved almost thirty years ago that the rotation of Saturn's moon Hyperion is chaotic, in collaboration with François Mignard.

I just found out yesterday, while studying Wisdom's book for my upcoming Mechanics course.

I remember Stan Peale from way back then; somebody told me he could've easily worked at the biggest Planetary Science Department at UCLA, but that he preferred the leisurely life of Santa Barbara, where he could and did ride his bike around.

One of his students became a world expert on solar system computer work, we were office mates, his name is Alan Boss. He is now at the Carnegie Institution for Science in Washington D.C.

Today I write on this epochal discovery I was not aware of. I knew Stan was good, since he predicted volcanoes in Io, and sure enough, a little later the smoking gun was there, smoking volcano would be a better description.

One can read in the Hyperion paper:

"It is expected that Hyperion will be found tumbling chaotically".

That was also confirmed.

This fit between observational and computational steps is the content of this note.
Mathematics is a cultural product, the moon's motion is something we can model, but maybe not understand the same way we understand a working car engine.

I explain; in Lisp one starts with a few axioms, just like Euclid did, then the logic of the rules leads to new constructs that surprise us. That does not mean that in the real world we are going to find a real process that follows exactly the rules we made up; what we may find out, which is great, is that the rules fit a set of experimental and observational steps.

Very few of us have that pleasure. I am happy to have known somebody like Stan, that has experienced such a pleasure.