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The science behind bats and balls

Where some see a simple game of balls and bats, scientists see an incredibly complex interplay of aerodynamics and kinematics, with results that not even Einstein could have predicted.
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Where some see a simple game of balls and bats, scientists see an incredibly complex interplay of aerodynamics and kinematics, with results that not even Einstein could have predicted. In recent years, sluggers have had the upper hand in baseball’s “arms race.” But who knows? Maybe the balance of power will shift again.

Every sport is governed by the laws of physics, of course. However, Paul Doherty, senior scientist at San Francisco’s Exploratorium, argues that baseball is a special case.

“Being the national sport, and being a sport that is just so concerned with statistics and numbers ... it attracts the kind of person who likes numbers in the first place and then might have a little scientific thinking applied to it,” he said.

For example, serious scientific studies have been done on the technique outfielders use to track and catch a fly ball. Another study determined that the “rising fastball” was an optical illusion, based on a batter’s perception of pitching speeds.

And what other sport ever had an official physicist? Yale Professor Robert K. Adair filled that post for the National League from 1987 to 1989, at the request of the late baseball executive (and one-time Yale president) Bart Giamatti.

“I like to point out that Einstein, if he were interested in baseball, still could not from first principles calculate the flight of the ball,” Adair said. “We know the basic rules, but we can’t solve the equations.”

A myriad of mysteries
The unpredictability of a baseball - and the prowess of a pitcher - has much to do with the 216 raised red cotton stitches encircling its cowhide surface. Depending on the way those stitches catch the air, aerodynamic forces can move the ball down or to the side in ways that bedevil batters. For example, as shown in the graphic above, a curveball curves because the stitches create an area of higher air pressure as the ball spins through the air.

Doherty says the ball’s qualities are the happy result of trial and error.

“If you made the seams on the ball really flush and flat, then it wouldn’t have the wonderful curving motions that it has,” he says. Scuffing or moistening the ball adds to the aerodynamic qualities — and to the pitcher’s magic.

But perception plays a role as well as physics: Adair calculates that a typical curveball goes through only 3.4 inches of deviation from a straight line drawn between the pitcher’s hand and the catcher’s glove. However, from the perspective of the pitcher and batter, the ball moves a hefty 14.4 inches. This fueled the decades-long arguments over whether the curveball really curved.

Perception also plays a part in other mechanical aspects of the game:

Does a higher pitcher’s mound help hurlers? As recently as 1997, major league general managers asked baseball’s rules committee to consider raising the pitcher’s mound, in hopes of lessening a perceived advantage enjoyed by sluggers.

Adair says there’s no scientific evidence that the mound’s height makes much of a difference, other than perhaps allowing a slight gain in pitch velocity.

Doherty, however, pointed out that standing taller on the mound could make a pitcher feel more imposing and confident. “We can’t ignore the psychological effect of looking up at the pitcher,” he said.

Does a heavier bat make for more home runs? “Probably 10 percent of the players do better with a heavier bat,” Adair estimated. But he pointed out that there was wide variation, with Babe Ruth’s bat weighing 47 ounces and Hank Aaron’s bat at less than 32 ounces.

“The really good batters are using lighter and lighter bats these days,” Doherty said. There’s a slight loss in the ability to give the ball a ride, but a significant gain in the ability to get the bat around quickly, he explained.

“I’d say the players choose what works for them,” Adair said. “There’s not a tremendous difference.”

Is the ball “livelier”? It’s a scientific fact that frozen baseballs don’t bounce as high or fly as far as room-temperature baseballs. Tales have been told for decades about players who schemed to have their rivals bat with balls that had been put on ice.

But Adair and Doherty both say there isn’t much variance in the liveliness of modern baseballs. “Balls are very carefully measured after manufacture, so it’s really hard to believe that any modern ball is going to be that lively,” Doherty said.

He said it might be just as important for batters to think that the ball is livelier: “If somebody expects to hit the ball further and strikes with confidence, they hit it a little further, too.”

The scientific edge
So if you set aside sociological factors — such as the much-debated dilution of pitching due to league expansion — is science really changing the game of baseball? Are there empirical reasons why the past few years have seen the rise of Ruthian sluggers such as Mark McGwire, Sammy Sosa and Ken Griffey Jr.? And could the game be tweaked to level the playing field?

The answer to all those questions appears to be yes.

First of all, there’s the Denver factor. The mile-high altitude of Coors Field gives batters an edge in two ways: Adair estimates that batted balls fly 7 percent farther, and curveballs curve about 25 percent less. This makes Denver a “pitcher’s purgatory, if not quite hell,” Adair contends.

But that’s just one stadium. The bigger trend relates to the science of batting, said William Murray, executive director of operations for Major League Baseball and chairman of the playing rules committee.

“I would say that there’s more scientific knowledge available now about bats and methods of swinging and properties of the bats, lengths and shapes and weights of the bats than there had been before,” Murray said. “And a number of hitters have really picked up on that and used it to their advantage. It’s tough on the part of the pitchers to pick up and counterbalance what the batters might learn.”

Year-round weight training plays a role in building better batters. And we’d be remiss if we didn’t mention strength-enhancing supplements such as Androstenedione, which created such a controversy for McGwire.

Pitchers are having a difficult time right now keeping up in the “arms race,” Doherty said.

“The pitchers are at the point where they’re ripping their tendons,” he said. “You can actually strengthen human muscles faster than you can strengthen tendons and ligaments.”

What’s the solution? Adair has a low-tech suggestion for tipping the balance more toward the pitchers: calling the high strike.

In theory, the strike zone extends from the bottom of the batter’s kneecap up to the midpoint between the top of his shoulders and the top of his pants. But in practice, the zone has shrunk - making it even tougher for pitchers.

“When I was a kid ... I think the strike zone was 2 or 3 inches higher, and that makes a considerable difference,” Adair said. “There have been efforts a number of times ... trying to raise the strike zone. It’s not easy. It’s a pretty subjective business.”

Every so often, Major League Baseball does urge umpires to be more vigorous about calling high strikes. But in the end, the outcome of each game depends on human judgment and athletic prowess rather than angular momentum and aerodynamic forces. Even bad calls are a part of the mix.

“I imagine you could set up some laser beams and have a robot call the strikes,” Adair said, “but it might not be quite as much fun.”