Porter W. Johnson and the Physics of Baseball

By Brian Grow

Like a utility player on a baseball team, Physics Professor Porter W. Johnson has done just about everything in his 34 years at IIT.

He has taught, consulted and chaired three different IIT departments. He has published 72 scientific papers on topics from Tullio Regge amplitudes to quark masses. He has promoted science and math in Chicago-area high schools and encouraged teachers to add more science to their curriculums. And now, he is finishing the third part of a four-part book series on Quantum Field Theory.

But perhaps Johnson’s most unique contribution to physics and IIT derives from a different passion—his love of baseball. The physics of baseball, that is.

Porter W. Johnson and the Physics of Baseball
Porter W. Johnson

Since his earliest days growing up in Chattanooga, Tennessee, Johnson says he’s been fascinated by America’s national pastime: its larger-than-life heroes such as Babe Ruth and Joe DiMaggio; its panoply of statistics; and the scientific challenge of understanding baseball’s mental and physical interaction.

That passion grew out of the days when, as a young man, Johnson and friends were members of the Knothole Gang—named after kids who watched minor league baseball games through knot holes in the outfield fence. He and Chattanooga chums used to attend local Southern League games of their minor league team, the Lookouts. And it was there that Johnson first had an inkling that the science of baseball was going to be part of his academic life. “As a player, I was never that great,” he says. “But I realized that I looked at the game from a different perspective: the perspective of a scientist.”

Since then, baseball has become a cornerstone of Johnson’s teaching and made him one of the foremost speakers and analysts on the physics of baseball. He has commented for newspapers and television, including recent chats with Chicago’s WGN and NBC channels on the Sammy Sosa corked bat controversy. “I’m sure he made a mistake,” says Johnson. But like a true scientist, he still gets excited explaining how a corked bat may be just as strong as a normal bat, but because it is lighter, a player can swing it faster.

What’s more, he likes to quote a line from the famous baseball movie "Bull Durham" to explain how the sport can be applied to science: “Baseball requires nonlinear thinking.” Rather than just marveling at the inexplicable skills of baseball players, that belief leads Johnson to ask questions like: How does a batter hit Randy Johnson’s 96-mile per hour fastball? How does Sammy Sosa hit so many home runs? Why does the baseball fly farther in high altitude stadiums such as Denver? How did Willie Mays judge the trajectory of a fly ball?

Here’s one example of Johnson’s answers:

“The major league pitcher stands on the mound a distance somewhat less than 20 meters from the batter’s box, and throws fastballs at a speed somewhat greater than 40 meters per second, so that the entire trip takes place in 0.4 to 0.5 seconds. The batter must decide in that brief instant whether, when, where and how to swing. Because of the influence of gravity, the baseball drops significantly from a projected straight-line path during its travel. The distance dropped is given by: d = 1/2gt2 = 1.2 meters … It is remarkable to me as a scientist that the batter can hit such a thrown baseball. Certainly, a person off the street would have trouble even seeing a major league fastball, although a significant ‘hum’ could be heard as it whizzes by!”

In addition, it’s the deeply embedded tradition of baseball in American culture, Johnson says, that makes it a useful tool to explain complex theories. Especially for young people, Johnson views the sport as a metaphor to explain difficult, inanimate—and supposedly boring—theories of physics. “Most people have never met a scientist,” says Johnson. “And they have rarely appreciated the effect of science in their everyday lives.”

When he began visiting local high schools around 1993 to help kids understand physics, Johnson says he needed a way to explain it in real-world terms. The result: he developed presentations that incorporated fun, simple baseball talks—and found he had the rapt attention of the entire class. “Physics is considered very hard,” he says, “The question is how do you take something that everybody is interested in and apply the rules of science.”

He adds that one positive side-effect of teaching the physics of baseball to young people is that, unlike cooking or golf, both the boys and the girls are intrigued. The reason: many girls have spent time watching boys play baseball, and macho boys don’t want to appear less familiar with the game than the girls. “Anyone who played baseball would be embarrassed not to know something,” he says.

Since then, Johnson has adapted to his presentation to many audiences. He has talked baseball to world-class scientists at the Argonne National Laboratory at the University of Chicago. This year, he worked with students and colleagues on an award-winning IIT Interprofessional Project to develop a map of U.S. Cellular Field, home of Johnson’s favorite team, the Chicago White Sox. That’s because White Sox executives wanted to know how far the home runs actually travel during the 2003 Major League Baseball All-Star Game’s Home Run Derby, a favorite event for baseball fans.

And the sport still has an array of unsolved physics problems. “Only one pitch has been really explained—the knuckleball,” Johnson says. That makes baseball an almost bottomless topic to bring scientists and students together to solve problems.

As a director of both SMILE—Science and Mathematics Initiative for Learning Enhancement, and SMART—Science and Mathematics through Application of Relevant Technology, Johnson also uses the physics of baseball to help teachers understand how to communicate the sciences better to their students. “There are an endless variety of ideas associated with science,” says Johnson. The Bernoulli Effect, the Magnus Effect and the Prandtl Layer can be explained, in part, through the dynamics of a good curveball.

Next up on Johnson’s sports-and-physics agenda? After being invited last year by Web TV to analyze how physics played a role in the 2002 Winter Olympics in Salt Lake City, he thinks he may have a cold-weather candidate to match his presentations about baseball’s “boys of summer.” “There’s lots of physics in hockey,” he says with a chuckle.