You can explain to people who don't know much of the physics, the early history... how Newton discovered... Kepler's Laws, and equal areas, and that means it's toward the sun, and all this stuff. And then the key - they always ask then, "Well, how do you see that it's an ellipse if it's the inverse square?" Well, it's God damned hard, there's no question of that. But I tried to find the simplest one I could.