Take me out of the ballgame

I have a confession to make: although born in the United States, I’m lousy at that country’s national pastime. I hit not, neither do I catch. If I had a dollar for every fly ball I dropped as kid, I could buy…well, a baseball glove, probably, but what would be the point?

So this week I was pleased to discover that there are solid scientific grounds for missing easy pop flies, and they have nothing…well, very little…to do with a complete lack of skill and/or depth perception on my part.

A team of researchers led by Alan Nathan at the University of Illinois, Urbana-Champaign, and Terry Bahill at the University of Arizona, Tucson, will soon be publishing a “pop-up paper” in the American Journal of Physics that explains it all.

Normally, a ball that’s been hit follows a parabolic path, which is pretty easy to figure out. But when a ball is popped up, its path is influenced by the backspin it gets from the top of the bat. This backspin generates a rotating layer of air around the ball, which makes it curve (something known as the Magnus effect).

Sometimes this curve is enough to cause a ball that originally flew forwards at a steep angle to begin climbing vertically, and then actually loop back on itself.

The researchers used a computer simulation to calculate all the various trajectories a pop-up could take. They also simulated a fielder, who reacted to the pop-up just like a real fielder: it moved back and forth in a kind of dance as it attempted to position itself under the ball.

With baseball soon to get underway even here in late-blooming Saskatchewan, the study is a reminder that there’s a lot of physics at play in the game…which may be why a lot of physicists like to study it.

Just last December, two physicists at the University of Colorado at Boulder, Edward Meyer and John Bohn, decided to find out if the Colorado Rockies baseball team’s practice of keeping game balls in a high-humidity chamber for several months prior to their use would actually achieve its stated goal of making the balls more “sluggish,” the better to counteract their propensity to fly up to six meters farther in Denver’s high-altitude air than they do in other parks.

It turned out that in their experiments, keeping a baseball in humidity of 30 to 50 pecent for two months actually had the opposite effect. At first that seems counterintuitive: after all, humidifying the balls increased their diameters by an average of 0.24 percent and their mass by 1.6 percent, making them both squishier and more subject to air resistance.

However, the balls’ slower speed off the bat is more than made up for by their increased mass, which means they take longer to decelerate. Not only that, moist balls curve less than dry balls, making them easier for batters to hit.

And speaking of curves, I could never hit those, either. Turns out that, once again, it’s not really my fault. Rather, it’s the fault of our evolutionary history, according to Cathy Craig, a psychologist at Queen’s University in Belfast.

Craig was investigating soccer, not baseball, but the principle is the same. She decided to see if experienced players could follow the trajectories of balls with side spin. She had them watch simulated shots with a spin of 600 rpm, and asked them to decide whether the balls would end up in the goal or not–and discovered that even professional soccer players couldn’t predict the results accurately.

The reason? Until recently, there was no reason why humans needed to be able to judge the trajectory of a side-spinning sphere travelling through the air. We know how gravity affects objects moving through the air, because that’s been important in evolution, Craig told New Scientist magazine. “But spinning balls don’t occur naturally. Why would nature bother having a visual system that’s adapted to them?”

My point exactly. Which means that I, who am unable to accurately judge the trajectory of spheroids hurtling through the air, am the normal one, and all of you good ball players are freakish mutants.

I feel much better now.

Permanent link to this article: https://edwardwillett.com/2008/04/take-me-out-of-the-ballgame/


    • Edward Willett on April 15, 2008 at 8:46 pm
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    • Ken McConnell on April 15, 2008 at 8:38 pm
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    I guess I’m a mutant, and so is my oldest son. Might be some hope for my youngest as he is just starting T-ball and not really catching anything unless it’s aimed at his open glove.

    My oldest, loves pop flies. We’ll see how he does with hit balls this season. When I was a kid, I loved playing outfield and reaching over the fence to rob a homer. 😉

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