Be careful with the word Styrofoam. Dupont will be after you. It is a trademark and should always be capitalized. You think they won't find it here on the UT, think again. A friend's wife got a letter from Dupont for a term paper she wrote. That was years ago, before the Internet. Ever since then, I've used the generic term, polystyrene.

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>Interesting read, and I could understand it. As I was reading the time and motion analogies, I was reminded of an engineering course I took in college. The professor demonstrated that regardless of speed, there is always one part of the tire or wheel that is motionless for just an instant [giving rise to friction]. It is that part that is directly in contact with the path (e.g., the road). If, in that instant, that part was not motionless, the tire would only spin and you would go nowhere.
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>To prove this to yourself, all you need are a bunch of evenly spaced spokes around a hub. You could do this with popsicle sticks in a styrofoam ball. Now "roll" the sticks across a counter top. The tip of the stick in contact with the counter is the one that is motionless for an instant while the rest move. The "contact spoke" does not really move until the spoke ahead of it contacts the counter. Using the model you wrote about, I guess you could say change and the advancement of time does not occur until the next "point of contact" hits the counter, or "when the rubber hits the road". < bg >