Illusion of a Curve Ball

The winner of the World's Best Illusion went to a Bucknell University professor and his work on the curve ball. It is a cool way to see why hitting a baseball is one of the hardest things to do in sports.

5 months ago Wilder. 7 comments 6 recs |

Story-email Email Printer Print

Comments

This is a neat find.

by abender20 on May 14, 2009 10:30 AM PDT reply actions 0 recs

That was so cool.

"Part, fools!
Put up your swords. You know not what you do."

by Fearless Frog on May 14, 2009 12:38 PM PDT reply actions 0 recs

I came here to post this link ...

but you’re a step ahead of me. It’s an interesting article, but I’m not convinced that the "sudden break" is caused by transition from central to peripheral vision. Someone trying to follow and track a pitch keeps the pitch in central vision. "Keep your eye on the ball."

The "sudden break" of a curve ball has always been a bit puzzling to me because, as the discussion in the linked page states, the curve of a spinning ball should be uniform. I’ve tried to think of several explanations for why the break might not be uniform, some of which I think are valid.

For example, the ball is subject to atmospheric friction. If, as is likely, friction slows the speed of the ball more than the rotation, the curve should increase simply due to loss of velocity as the ball travels to home plate. This, however, would not be a sudden increase in curvature.

As the article notes, the curve is caused by differential pressure around the ball created by the spin. At the moment the ball is released from the pitchers hand, that pressure field is not present. If it takes a half a second or so for the pressure field to form, the ball will actually suddenly start to curve once the field develops.

So I think it is totally plausible that the sudden break of curve ball is real and not just an illusion.If you compound increasing curvature due to loss of velocity with a sudden onset in curvature caused by establishment of the pressure field around the ball, the result should be a pitch that looks as if it is traveling relatively straight, then suddenly moving off in a new direction. If that movement also causes the ball to suddenly shift toward peripheral vision, the perception of the break could be further enhanced as per the illusion.

by Steve Nelson on May 16, 2009 5:37 AM PDT reply actions 0 recs

Um:

As the article notes, the curve is caused by differential pressure around the ball created by the spin. At the moment the ball is released from the pitchers hand, that pressure field is not present. If it takes a half a second or so for the pressure field to form, the ball will actually suddenly start to curve once the field develops.

No. Even if you had no understanding of physics whatsoever, the common sense act of asking yourself “How long does it take for a ball to reach the plate?” would tell you that is wrong. There is no significant delay in the magnus effect. In fact, it exerts more force on the ball the instant it leaves the pitcher’s hand than at any other point during its flight. This is because the force is a factor of how fast the ball rotates and the speed of the air moving across its surface. As you yourself point out, the friction from moving 60 feet slows it down, which lessons the force acting on the ball.

by Vatinius on May 16, 2009 9:40 AM PDT up reply actions 0 recs

I don't think this sentence is correct either.

Someone trying to follow and track a pitch keeps the pitch in central vision. “Keep your eye on the ball.”

It’s physically impossible for a human eye to stay centrally focused on the ball at all times during an at bat. What hitters do is follow it as long as they can to try and establish a flight pattern, but at some point they have to shift their central focus from the incoming ball to the expected contact point. At that instant, the baseball does indeed move from their central to their peripheral vision.

by Matthew on May 16, 2009 10:30 AM PDT up reply actions 0 recs