inverse-square law through geometry

Since it's cloudy here and the aurora probably couldn't be seen this
far down anyway even if it were clear, I passed some time demonstrating,
somewhat less than rigorously, the inverse-square law of gravity using
only geometrical methods--without analysis, in other words. If you find
that sort of stuff interesting (and I can't see why you would), I've
made a short PDF of it available at

http://astro.isi.edu/notes/gravity.pdf

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt