Some baseball fans are content simply to watch the game they love and argue its age-old debates. But then there are baseball fans who also happen to be scientists.

Physicist Alan Nathan of the University of Illinois and mechanical engineer Lloyd Smith of Washington State University wanted to put some of the biggest baseball myths out there—corked bats hitting farther, juiced balls and the effect of humidity on baseballs—to the test. Because collecting measurements on a live batter is next to impossible, Nathan says, the team turned to an advanced testing lab that Smith designed at Washington State.

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How It's Made

Developed in 2002, Smith's testing system measures the burst of a ball off the bat with three key instruments. There's a 12-foot air cannon delivery system including a sabot—a plastic carriage that guides the ball down the tube—a box of three light screens to measure ball speed and a bat pivot to hold the bat in place.

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First, the scientists place a baseball onto a polycarbonate sabot and load it into the cannon. Since the bat is stationary and there's no batter swinging it, Smith's setup must accelerate the baseball to a speed that combines both the velocity of a major league pitch and the bat speed of a major league hitter: about 150 miles per hour. The sabot fits precisely within the cannon's tube, and even at that crazy speed it can keep a baseball along a straight path with little spin or deviation. The stability the sabot provides is the key to hitting the sweet spot and accurately testing the pop in a bat, Smith says.

The air cannon blast ejects both the sabot and the baseball from its barrel, so Smith designed an arrestor plate to stop the sabot and allow the ball to fly free. "That arrestor plate is, in my opinion, kind of a cool design," Smith says. To soften the blow of the sabot, the plate rides on four pneumatic shocks. Yet even this wasn't enough, he says, so he designed the arrestor plate to be moving backward when it catches the sabot, cradling it to soften the impact. "It's kind of as if you were trying to catch a baseball without a mitt."

The baseball then flies free into the light box, which contains three light screens designed to measure the ball's speed. As the ball passes through each screen, the time is recorded. With these three separate times, Nathan and Smith can calculate the speed of the ball both as it enters the box and also after it hits the bat and rebounds backward.

Those speed measurements allow the researchers to calculate what they call the coefficient of restitution (COR). "[It's] the bounciness of the ball off the bat," Nathan says, and it's the primary metric the team uses for testing bats—and busting baseball myths. In a ball–bat collision, the energy is shared between both the ball and the bat. That gives a wooden bat a COR of just under 0.5, Nathan says. Hollow aluminum bats tend to have a higher COR, though, because of the "trampoline effect," he explains. "Instead of going to compress the baseball, which is what happens when it's hitting a rigid surface, it goes into compressing the wall of the bat, and that energy is very effectively returned back to the ball again."

Smith's system is so effective that the NCAA uses it to regulate its bat performance standards. But for a new study, he and Nathan set to testing three of the most debated myths in baseball.

Corked Bats

Corked bats are one of the most notorious examples of baseball cheating, but the researchers suggest it might not do much good: When testing corked bats, Nathan and his team found that instead of adding more trampoline effect, corking a wooden bat actually decreased it. "What you gain in higher bat speed, you lose in a less effective collision," Nathan says. "It does not lead to a higher batted ball speed." And because the bat is lighter, balls hit with a corked bat don't travel as far, he says. However, the lighter weight of a corked bat may allow hitters to get to pitches they might not otherwise hit with a standard bat.


When baseballs were flying out of the park in the late 1990s and early 2000s, speculation abounded that the balls—and not just the players—were juiced. Nathan and Smith wanted to see if modern baseballs truly are livelier than those used decades ago. So they fired two sets of balls, one from the 2004 season and one from the late 1970s, against a solid, flat steel plate, and measured the COR. The result? Identical COR figures between balls present and past, suggesting that the difference was in the players.


In the 1990s, Coors Field in Denver was a launching pad. The home of the Colorado Rockies set the major league record in 1999 with 303 home runs in a single season. This was presumably caused in part by the stadium's high elevation, which meant that batted balls encountered less air resistance. But the Rockies got tired of seeing their pitchers beaten up in slugfest after slugfest, and so the organization began to keep game baseballs in a humidor, hoping the added weight and size would make the balls come back to earth more quickly.

Nathan and Smith tested out the humidor-baseball idea in the lab, and, indeed, they found that a relative-humidity increase from 30 percent to 50 percent would result in a COR decrease of 0.024. That might not sound like much, but Nathan says it would cause an average reduction of 14 feet on fly balls, cutting home run probability by 25 percent. Home run statistics from Coors Field agree with Nathan and Smith's conclusions: They were down from 3.29 per game in the pre-humidor era (1995-2001) to 2.39 per game in the humidor era (2002-2010).

Split-Finger Sorcery?

Now that he's tested some of the game's most common hitting myths, Nathan wants to turn his attention to pitching. While he was watching the New York Yankees recently (though he's a fan of the rival Boston Red Sox), one split-finger fastball by Yankee pitcher Freddy Garcia caught his eye. "The ball breaks in a direction that doesn't agree with our common perception of how it should break, given how it's spinning," he says.

Though the game has been played professionally for more than a century, there are plenty of curiosities that need to be put to the test in the lab. "The players, they know how the game is played," he says. "I'm just trying to understand, or put in some firm physics basis what they already intuitively understand."

What do you think?