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At long last, Opening Day is nearly here. As with each new season, this one arrives with a slew of major-league questions: Can the Phillies repeat? Can the spendthrift Yankees break their World Series drought? Is this the year the Athletics reclaim their freewheeling magic? But the answers to all those big questions will ultimately arise from countless small interactions, both human (a pitcher facing down a batter, a base runner challenging a catcher's arm, a manager's clever double switch) and physical (a ball meeting the bat's sweet spot, a sharp slider slicing through the air, a pop fly tracing a parabolic arc through the sky).
Alan Nathan, a physics professor at the University of Illinois at Urbana–Champaign, has trained his expert eye on those questions of physics that make up the quanta of the game. Nathan maintains an online repository on the physics of baseball, drawing from his own work and that of other baseball-minded scientists. We spoke to him about corked bats, the mysterious "gyroball," and whether his favorite team has the manpower to grind out another championship season.
[An edited transcript of the interview follows.]
How did you become interested in this subject?
It started innocuously enough. We have these outreach programs, mainly aimed at high school science students, and we take turns giving talks, usually about our own research. There's this book, The Physics of Baseball, by Robert Adair, that I'd had on my shelf for seven or eight years and never opened—this is way back in 1997—and I thought, "Well, let me agree to give a talk about this and that will force me to read it." So that's what I did, and it would have been pretty much a one-shot deal had it not been for the fact that there was a reporter for the local newspaper in the audience. He interviewed me afterward and wrote it up in the paper, and then people started calling me up asking me to give talks. So then I started to actually get more serious about the whole thing. I had a sabbatical about a year later and spent some fraction of my time doing some serious research. And it's just sort of grown from there.
On your Physics of Baseball Web page, I see a lot of information about the spin of the ball. To an observer of baseball, this is something that comes up a lot when we're hearing about pitching but very rarely when we're talking about batted balls. Is this a major factor for balls in flight?
Absolutely. It's one of the determining factors in how far a fly ball will carry, for example. Typically, if you want to hit a long fly ball, you want to put backspin on that ball. The so-called Magnus force on the spinning baseball will be upward for a ball with backspin, and basically it opposes gravity. It keeps the ball in the air longer so it travels farther. So this leads to batting strategies—you actually undercut the ball. You don't want to hit the ball head-on, which would give you sort of a line drive. You want to undercut it a bit, which gives it more of a vertical takeoff angle and also gives the ball backspin. And the backspin is essential if you want to hit a long fly ball.
On the other hand, if you do the opposite—if you hit on the topside of the ball—generally the ball goes down, so it's going to be a grounder, and it's going to have topspin on it. But topspin itself can lead to interesting things happening. Sometimes a batter can hit a sinking line drive; again, it's another hitting strategy. In this case the ball is hit as more of a line drive, but it's slightly topped, so the ball has topspin on it. Topspin makes the ball fall more rapidly, and that's what you might want to do for a line drive so it falls in front of the outfielder. So there are all sorts of hitting strategies that batters can employ, and I suspect that although they don't think of it maybe quite in these terms, they really do understand what it's all about.