>The movement of the planets make sense. According to Kepler's Laws, the planets move around the Sun in an ellipse, and they move faster when they are closer to the sone. This makes the entire model quite reasonable.

Not only that, but Kepler's second law is a relationship between the speed of the planet and its position on the ellipse. If you watch you'll see this law in action as well.

>I don't want to take the time now to analyze the program in detail, but let me review the physical principles, just to make sure you didn't overlook anything.
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>The Sun attracts the planets. The planets attract each other, unless you make the simplified assumption that the planets have an insignificant mass, compared to the Sun. This assumption is correct, as a first approximation. Even Jupiter has only about 1/1000 the mass of the Sun.
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>The planets, of course, also attract the Sun, so they would affect its movement, too.

Also right. In the model all objects have an effect on the acceleration due to gravity of any object (unless, lIngoreGravity is on, I did that for performance reasons when the effects of the calculuation wouldn't even be noticeable, as you note).

It would be interesting to see implementations of this model if anyone is intrigued enough to post their take. (I'd especially like to see Calvin's stab at it as he's looking for more interesting uses for VFP :-)

I've got a handful of ideas about Newton's laws as they relate to Einstein's, that it may take a far simpler correction of Newton's laws to account for the advances put forward by General Relativity, and in the process explain somethings about our observations that have led to the invention of Dark Matter. A complete, fleshed out, adjustable program would make those ideas pretty simple to test.

More on that later, for now I'll see if anyone is up to posting their re-write.