Laurila: Q&A with Alan Nathan on the physics of pitching

From SABR member David Laurila at FanGraphs on November 5, 2013, with SABR member Alan Nathan:

What is the relationship between spin axis and the backup slider? Alan Nathan knows the answer. He also knows why fastballs move more than curveballs and why split-finger fastballs drop. A physics professor emeritus at the University of Illinois, Nathan is an expert not only on nuclear physics, he is the man behind The Physics of Baseball

Nathan on velocity and break:
“In principle, it would be possible to throw a curveball 100 mph. It’s not the physics that prevent you from doing that. What’s preventing you is that it is biomechanically hard to do. You’re trying to get on top of the ball and put topspin on it, and to do that you’re probably sacrificing speed. But there’s no reason, in principle, that if you were able to spin a 100-mph pitch with topspin you would get even more downward movement.

“You actually see more movement on fastballs than you do, typically, on curveballs. Defining movement as how much the ball deviates from a straight line with the effect of gravity removed, you get a lot of movement from fastballs. People don’t normally think of there being a lot of movement from fastballs, because the upward movement you’d get from backspin on a fastball means the ball doesn’t drop as much as it would just purely from gravity. But there’s a significant amount of upward movement. Rapidly spinning balls moving at high speeds have a lot of movement on them.

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Originally published: November 5, 2013. Last Updated: November 5, 2013.