College of Liberal Arts and Sciences at Iowa State University

Throwing baseball a curve

Eli Rosenberg says physics plays an important role in America's pastime.

Baseball is such a simple game.

You throw the ball. You hit the ball. You catch the ball.

Simple right.

Not so fast says Eli Rosenberg, professor and chair of the Department of Physics and Astronomy.

"In a classic episode of 'Seinfeld' George Costanza teaches hitting to New York Yankees Bernie Williams and Derek Jeter," Rosenberg says, "and he tells them how easy it is to hit a baseball.

"Once again George is wrong, but there are some basic physics ideas that are important in understanding why baseballs behave the way they do when thrown and hit," Rosenberg said.

Rosenberg opened with the "Seinfeld" clip during a presentation on the physics of baseball in late June. He spoke as part of the yearlong series of activities surrounding the 2005 World Year of Physics sponsored by the U.S. Department of Energy's Ames Laboratory and presented by faculty from the Department of Physics and Astronomy to a capacity crowd in the Spedding Hall auditorium.

The lifetime baseball fan hopes to give an encore presentation sometime during the World Series in October.

Some of the seemingly simple aspects to the game are not really that simple – at least when you apply physics to the sport Rosenberg says.

Some pitching physics include:
What makes a curve ball curve?
A 90 mph fastball takes less than half a second to record plate after leaving the pitcher's hand.

Physics can also help explain the factors that are important when hitting the ball including bat speed and where the ball should strike the bat:
When a batter swings, the swing itself takes just 150 milliseconds. During the first 50 milliseconds, the batter can stop, but after 100 milliseconds, the bat is moving too fast and the swing cannot be checked.
If a swing is seven milliseconds too late or too early, the ball will sail foul past the first- or third-base lines.
Why corking a bat gives the batter better bat speed and more time to react but won't make the ball go further.
Why outside the major leagues aluminum bats are more popular than wood bats.
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Physics is also involved in judging a fly ball and ultimately catching it," Rosenberg said. "It's a very complicated game."

OK, but it is still just a game right?

Don't be so sure about that Rosenberg says. There's a lot of literature about the physics of baseball and other sports including football, basketball, golf, tennis, drag racing and even fly-fishing.

"The manufacturers of golf equipment are very concerned about how to improve club and ball design. Understanding the physics involved is an important factor," he said. "They are extremely interested in what makes a golf ball go farther.

"There are some very serious people studying this. In fact there was an article in the recent American Scientist that gave evidence, contrary to many (ball players') opinions, that an overhand four-seam fastball doesn't have more lift than an overhand two-seam fastball."

But don't count on this diehard baseball fan to give up on trying to understand the matter-antimatter asymmetry in the universe by studies at the BaBar experiment at the Stanford Linear Accelerator (SLAC) in California to concentrate on the physics of baseball or another other sport though.

Still there are some benefits to the physics of sports.

"This was a fun talk to put together and I hope one that presents a different image of physicists and makes more students think about physics in terms of course selection and a career," Rosenberg said.