Repost: The Optical Illusion of Curveballs

[Mike Maffie is on a “thesis-defense vacation” this week, so we’re re-running one of his most popular columns from last year. Note new research at conclusion.]

I was reading an article about Rafa Nadal and the unbelievable topspin he generates on his forehand. Another player described the feeling of returning Rafa’s forehand as “like ripping your shoulder out of its socket.” For those who don’t follow tennis, Nadal can hit a tennis ball with about 500 more rotations per minute than the next best tennis player. Naturally I asked Google how many rotations per minute a curveball has.

Here’s the answer. It turns out the average Major League curve ball rotates at 2,450 RPM. Aces like Justin…