How Baseball Players Catch Fly Balls

I thought that this was pretty cool. Somewhere my high school algebra teacher is smiling, more proof of math in the real world.

"Years ago, physicist Seville Chapman proposed a model to explain how players manage the path of a fly ball so that they arrive to intercept it at just the right time. His theory, called Optical Acceleration Cancellation (OAC), used the acceleration of the ball through the vision field as a guide for player movement.

As a fielder watches the ball rise, he moves either forward or backwards so that the ball moves at a constant speed through his field of vision. If he moves too far forward, the ball will rise faster and may eventually fly over his head. If he takes too many steps back, the ball will appear to rise slower and will drop in front of him.

By managing the ball's position with his movement, a fielder will end up at the right spot at the right time. This explains why the stationary fielders could not predict where the ball would land, as they did not have the benefit of OAC.If we ask real fielders how they knew where to run to catch a ball, they may not respond with, "Well, I simply adjusted my relative field position to keep the tangent of the vertical optical angle to the ball increasing at a constant rate." So, to test the OAC geometric equations against real life, researchers led by Dinant Kistemaker of the University of Western Ontario, compared the predicted running paths from their mathematical simulation with the real running paths of fielders observed in a previous study.

"We have found that running paths are largely consistent with those observed experimentally," Kistemaker told LiveScience. "Largely, and not completely, because the start of fielders is somewhat strange: They tend to step forward first, irrespective of the fact that they have run either forward or backwards to catch that fly ball."

The research is detailed this month in the journal Human Movement Science."


The Rebbetzin's Husband said...

Where do the steroids fit in?

Or Am I? said...

I gotta share this with my baseball crazy kids. I wonder if knowing this would help emergent baseball players?

Jack Steiner said...


It is kind of neat.


Do you really want me to answer that. ;)


I thought that it was kind of a cool fact. I'd imagine that it might even tie into how we figure out how to shoot a basket.

Anonymous said...

I admit this is interesting, but it's sort of annoying, too.

Science demystifies wondrous experiences. It's cool that scientists can model a fielder's response to a fly ball; but it's wondrous that the fielder, without the aid of higher mathematics, or any computer except his brain, can place himself in the right position to catch the ball.

Jack Steiner said...

There is something nice about the "mystery" of a thing. Sometimes it is more fun not to know that the wizard is just a man behind a curtain.

Soccer Dad said...

It didn't occur to me that moving was an important part of the process. For example, good announcers have a pretty good sense of the trajectory of the ball off the bat. (Not all announcers do.) And there seem to be some players who can do that too. (Granted that's not most of them.)

Still, I've always thought about this. A fielder who catches a ball is unintentionally making all sorts of calculations in his mind.


Jack Steiner said...


I played left and center field for many years. I have often thought about positioning myself to catch the ball. In some ways not so different from catching a football.

Soccer Dad said...

I e-mailed your post to David Pinto. He reminded me of this.

test said...

Well, it is not so much that the fielder actually do the math in their brain. This article is actually providing mathematical evidence that a catcher does not need to do the math. The only thing they have to do is to detect is whether the projection of the ball on the retina is accelerating (this means that the fielder should accelerate backwards), decelerating (accelerate forwards) or has a constant velocity (keep doing what you are doing).
This is in contrast with another theory that states that the brain needs to detect position, velocity and acceleration and then calculates the landing position.

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