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How Dr. Alan Nathan Became Baseball Fans’ Favorite Physicist

The University of Illinois professor emeritus had to do a public talk about his field, so he picked his favorite sport to illustrate it. Then it became an obsession.

Alan Nathan readies his curve.   Photo: Nathan Stauffer

Baseball remains the most pastoral of the major sports. Outside, in the nicest months of the year, it is played at a pace that has always lent itself to contemplation and close analysis. But in the last generation or so, the kind of analysis has deeply changed. The measurability of the sport, once mostly confined to the backs of baseball cards, has exploded into a dizzying collection of numbers the value and reliability of which sometimes even the most dedicated of enthusiasts cannot agree.

But the science of what happens on the field has not really changed, though thanks to the work of people like Dr. Alan Nathan, we are beginning to better understand it.

Nathan, a professor emeritus at the University of Illinois, began teaching at the university in 1977. A native of Maine, he grew up rooting for the Red Sox, but some of his earliest baseball memories include the Dodgers winning their first ever World Series in 1955, and Don Larsen’s perfect game for the Yankees in Game 5 of the 1956 Fall Classic.

And for decades Nathan’s interest in baseball remained like anyone else’s. He followed Boston’s ups-and-downs, including two trips to the World Series—the storied 1975 showdown with the Cincinnati Reds and the tragic 1986 series against the New York Mets—and then in 1997, his attachment to baseball was forever changed.

“Our physics department has an outreach program where we give talks to the public and high school students about physics. Usually when one of us talks, we talk about our own research, and when they asked me to give a talk, I decided to talk about the physics of baseball,” Nathan told Chicago. “Not that I knew anything about it; I hadn’t even thought about it before.”

But Nathan quickly turned his own interest in physics to his favorite sport, beginning by opening a book that had been sitting on his shelf for a few years. The Physics of Baseball by Robert Adair was his jumping off point.

Nathan said he expected to simply read the book and share on what he learned, and that would be that. But thanks to a local reporter who heard his initial talk and interviewed him about it for the Sunday paper, Nathan is still sharing what he’s learning almost two decades later. Not long after that initial talk, Nathan had a sabbatical from the University of Illinois, so he decided to spend it studying the physics of baseball more closely. He almost immediately found a fascinating rabbit hole of study that helped change a long-held perception in baseball.

“Grip on the bat, while the ball and bat are in contact with each other, plays no role whatsoever in the collision itself. And that pretty much goes against what you might call conventional wisdom,” Nathan said.

“Not scientific wisdom, but baseball wisdom,” he adds, elaborating that at the moment when the ball strikes the bat, the hitter’s grip doesn’t matter at all. In fact, he could even let go of the bat altogether—at that point of contact—and it would not change how the ball was hit.

For the skeptics, Nathan said he will show them video of a home run Todd Frazier hit while he was still with the Cincinnati Reds. At the moment of contact, his hands are not gripping the bat at all.

“Most non-science people are somewhat skeptical at first, and then I show them this home run, and they cease to be skeptical anymore,” Nathan said.

Baseball wisdom espouses many things, some of them not backed by science, like grip on a bat at the moment of contact, and others fully reinforced by it. For instance, baseball wisdom has long said that hitting a fastball is one of the hardest things to do in sports. Nathan says that scientifically that’s true. It’s timing, it’s placement of the bat, it’s guessing where a 90+ mph pitch will cross the zone, it’s hitting a round object with another round object. Only the elite of the elite can do it at the major-league level.

“When they say baseball’s a game of inches, it’s probably better said that it’s a game of fractions of inches when it comes to hitting,” Nathan says.

In the modern game, baseball has increasingly become a game of the three true outcomes: home runs, strikeouts, and walks. The first of these, Nathan says, is partly due to hitters’ growing fondness for launch angle. In other words, hit the ball hard and in the air and trust it to carry over the fence.

“The idea is you want to hit the ball in the air, and if you’re trying to get the longest distance on a fly ball, you want to hit it somewhere between 20-35 degree launch angle—25-30 is sort of the sweet spot; it will get you the longest distance,” Nathan says.

This works best for hitters against pitches that are lower in the zone; it’s easier to swing up on the ball just enough. Hitters slightly adjust their swing plane to create more loft and get the ball in the air more than what’s typical.

“10-15 degrees is enough to carry over the infield, but enough to drop in front of the outfielders, so you could get a single pretty much every time if you hit the ball hard and keep it fairly low,” Nathan says.

This is, at least for now, an approach that has been largely abandoned. Pitchers are counteracting this by going high in the zone, but this is hard to do well, thanks to gravity and spin rate. On average, a pitcher spins a fastball at about 2200-2300 rpm. The backwards spin on the ball created by the release from the pitcher’s throwing hand is enough to keep it from falling too rapidly, but not enough for the ball to ever rise in the zone. In theory, Nathan says, a pitcher could create rise on a fastball, but he would have to figure out how to almost double his spin rate. Unless the balls are made lighter or pitchers doctor them themselves, this isn’t possible.

Baseball is full of nuances, and though the game has been studied closely for at least a century, the work in the last two decades of people like Nathan has expanded our understanding of how those little details come together. He’s become a go-to for the sabermetric community for his work on things like the PITCHF/x pitch tracking system. Recently he chaired a committee of scientists convened by Major League Baseball to investigate whether changes in the manufacturing of baseballs led to the sport’s recent home run surge—a report that confirmed the independent work of researchers like Rob Arthur and Nathan himself.

He remains among the Red Sox faithful, but his studies have allowed him to enjoy the sport beyond New England.

“If I’m watching my Red Sox play, I’m pretty well engrossed in the game, sitting on the edge of my seat, and I’m not thinking too much about physics,” Nathan says. “If I’m casually watching a game, I like to look for things that are occurring in the game that are things that I already have some understanding of, or that might be interesting new topics to try and learn about.”

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