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The Sciences

How a Baseball Star's Tricky Pitch Strikes Out Hitters---and Baffles Physicists

The CruxBy Guest BloggerNovember 15, 2012 2:07 AM

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Andrew Grant is an associate editor at DISCOVER. His latest feature, "William Borucki: Planet Hunter," appears in the December issue of the magazine.

Dickey.jpg

Last night Major League Baseball announced the winners of the Cy Young Award, given to the year’s best pitchers in the American and National leagues. The National League victor was New York Mets pitcher R.A. Dickey. That he won the award is remarkable, and not just because he is a relatively ancient 38 years old or because he plays for the perennial punch line Mets. Dickey is the first Cy Young winner whose repertoire consists primarily of the knuckleball, a baffling pitch whose intricacies scientists are only now beginning to understand. Most pitchers, including the other Cy Young finalists, try to overwhelm hitters with a combination of speed and movement. They throw the ball hard---the average major league fastball zooms in at around 91 miles per hour---and generate spin (up to 50 rotations a second) that makes the ball break, or deviate from a straight-line trajectory. Dickey does neither of those things. Rather than cock his arm back and fire, he pushes the ball like a dart so that it floats toward the plate between 55 and 80 mph. The ball barely spins at all---perhaps a quarter- or half-turn before reaching the hitter. That lack of rotation turns out to be the reason Dickey can get away with throwing the pitch more than 85 percent of the time. A baseball is not perfectly smooth---it has stitches that rise about seven-hundredths of an inch above the skin of the ball. When a typical pitcher throws, the ball spins so quickly that those stitches become irrelevant; it moves through the air as if it were perfectly round. But when the ball barely rotates, that slight protrusion becomes very important. The seams create turbulence as they cut through the air, leading to forces that can push the ball in any direction. “The movement is all over the place,” says Alan Nathan, a physicist at the University of Illinois at Urbana-Champaign who studies the physics of baseball. “It’s the only pitch that’s as likely to go up as down and as likely to go left as right.” This randomness is the knuckleball’s most endearing yet perplexing trait: Nobody, including the pitcher, knows where and how much it will break. (This is the theme of the critically acclaimed documentary Knuckleball! that premiered in September.) It also leads to a sort of mystique surrounding the pitch, making it difficult to separate reality from perception. Hitters often describe the pitch as dancing or fluttering through the air before making a sharp turn at the last moment. Until recently, there was no evidence to determine whether that is really the case. Fortunately, Dickey happens to be playing in an era in which we can study the physics of his handiwork and measure what the ball really does during its 0.5-second journey between pitcher and hitter. That’s exactly what Nathan did earlier this year. He tapped into the wealth of data from PITCHf/x, a system of cameras that tracks the speed and trajectory of every pitch thrown in all 30 major league stadiums. (Sportvision, the company that makes the technology, is also responsible for the yellow first down line on football broadcasts and the ill-fated glowing hockey puck.) The cameras capture 60 images a second and can identify the location of the ball with half-inch precision. After analyzing trajectories from two games pitched by Dickey and two by Tim Wakefield, a Boston Red Sox knuckleballer who retired after the 2011 season, Nathan was able to uphold one piece of conventional wisdom while striking down another. His measurements confirmed that the knuckleball is indeed the most random of pitches---there is no tendency for the ball to break in any particular direction. But his analysis also dispelled the notion that the ball dances to the plate on an uneven trajectory. His measurements revealed that a knuckleball takes just as smooth a path as any other pitch. Nathan’s findings lead to an interesting question: What accounts for the disconnect between what hitters say they see and what is really happening? Nathan doesn’t have the answer, but he suspects it has more to do with psychology than physics. Hitters aren’t used to seeing the pattern of the seams as the ball approaches them, he notes. Perhaps their observation of the ball’s gradual rotation creates an illusion that the ball itself is moving when it is really just the seams. There is some evidence to back this up. Take a look at this animation. Even though the ball is moving straight down, the changing pattern of shading creates the illusion that it is traveling at an angle. Nathan offers up a fun and effective way to test this hypothesis: Paint the seams of a baseball white (thus removing them as a visual cue) and have hitters take hacks against some knuckleballs. Nathan hasn’t set up such an experiment yet, but he is beginning a study to measure the knuckleball in a wind tunnel to determine why the ball moves so randomly. Perhaps Nathan’s analysis will give us a better understanding of how physics, possibly with some psychology thrown in, makes Dickey’s knuckleball such an effective pitch. Until then, we can marvel at the fact that one of the slowest hurlers in the majors just received pitching’s most prestigious honor. Updated 11/15/12 to reflect that Dickey won the award.

 R.A. Dickey image courtesy of slgckgc / Flickr

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