It's surprisingly fun for such a simple little thing, especially since the lack of friction makes it so much more compelling than the "marble in a bowl" demonstration I got when I was a kid.

Would work fine in IE if he just added the ExplorerCanvas js file (from Google) http://excanvas.sourceforge.net/

He's used the Euler method, which I think is why you get aberrant behaviour when the cursor comes near the particle:

http://en.wikipedia.org/wiki/Euler's_method#Error

This also serves as a good repro of a Firefox memory leak (watch your task manager while it's running). There won't be many usable canvas apps until their JS engine is tightened up or replaced.

No, it gcs after a while. Memory usage steadily climbs until it hits a certain point and then drops back down.

I used to do this with a large magnet and a little chip off the magnet... accidentally figured out how orbits work. Fun times. :)

Nice little toy, but what's the next level? 2 objects, try to get a stable orbit? Talk about a steep difficulty curve. (http://en.wikipedia.org/wiki/N-body_problem)