PERSPECTIVE
The Physics of Baseball: Does a curveball really curve, or is it an optical illusion? By Charlie Freeman
I PHOTO PROVIDED
Charlie Freeman, pitching at MIT
Charlie Freeman, associate professor of physics at SUNY Geneseo, is a nuclear physicist and lifelong baseball fan who honed his curveball during his college days pitching for Massachusetts Institute of Technology. He has given numerous talks on the physics of baseball in a variety of venues including high school physics classrooms, undergraduate physics colloquia, SUNY Geneseo alumni and parent events, and professional physics conferences. He also is a youth baseball coach for his three children and serves as director of the 1.7 MV Pelletron particle accelerator laboratory in the college’s new Integrated Science Center. At the height of Major League Baseball season, he reveals some of the mysteries of America’s favorite pastime.
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geneseo scene
t’s often said that hitting a baseball is the most difficult task in sports. Major League pitchers are able to hurl a baseball toward home plate with speeds approaching 100 mph, giving the hitter only a fraction of a second to size up the pitch. The ball has a diameter of less than 3 inches, and the rules of the game allow the barrel of the bat to be a maximum thickness of 2.625 inches. Hit the ball a fraction of an inch too low and you’ll hit a weak popup. Hit it a little too high and you’ll pound the ball into the ground — where it will likely be scooped up and thrown to the first baseman before you reach the bag. As a nuclear physicist might say, the cross section for a solid ball-bat collision is small. To make matters worse, new generations of pitchers add new devastating pitches to their arsenal — the slider, the splitter, the cutter, even the mysterious gyro ball. It’s enough to keep even the most unflappable hitter awake at night. Perhaps the first “mad scientist” to start experimenting with new pitches was Candy Cummings who, in the late 1860s, invented the curveball. Cummings discovered that if he snapped his wrist downward at precisely the right time during his delivery, he could give the ball an unusual top spin, which caused the ball to curve downward.
Hitters reported that a well-thrown curv eball would suddenly change direction on its way to the plate, making it almost impossible to hit. Soon after the discovery, pitchers everywhere were copying Cummings’ throw. The curveball would change the course of baseball history. ••• THE DEBATE
What makes a curveball so hard to hit? Does the ball really curve or is it merely a carefully crafted optical illusion? Players and scientists have debated this question since its invention. Some have argued that the curve on a curve ball was legitimate. Others said batters’ brains PHOTO were being tricked into thinking thePROV ballIDED was curving. By the 1940s, after a series of wind tunnel and other tests on a spinning baseball, the scientific community’s consensus seemed to side with the reality of the curveball. But this worldview came into question in 2009 when four professors from institutions across the United States developed a nifty Web-based optical illusion, simulating how a batter sees a spinning baseball coming into home plate (http://illusioncontest.neuralcorrelate.com /2009/the-break-of-the-curveball/). As the observer shifts his or her gaze of the ball from peripheral vision to their central vision, it appears to suddenly change direction. However, care-