Physicists who do not play baseball

baseball batby basheertome

Baseball, cheating, and physics
[Via Boing Boing]

Some good news for Sammy Sosa fans still whispering, “Say it ain’t so.” Back in 2003, Sosa was caught using a corked bat—a normal wooden bat hollowed out in the center and stuffed with lighter cork material. That embarrassing incident did happen, and it does go against baseball rules. But, according to physicists at the University of Illinois and Washington State University, a corked bat probably doesn’t offer much of an advantage. Sure, Sosa technically cheated. But he didn’t actually cheat in a practical sense, they say. At least, not by altering his bat.

There was some anecdotal information from players that there’s something like a ‘trampoline effect’ when the ball bounces off a corked bat,” says Nathan, one of the authors of the new study. So the researchers hollowed out a bat, stuffed it with bits of cork and fired a ball at the bat from a cannon. If anything, the ball came off the corked bat with a slower speed than off a normal bat. Less velocity means a shorter hit. Their conclusion: the trampoline effect was bogus.

But there was another way corking might work: a corked bat is a few ounces lighter than an unadulterated one, and a lighter bat means a batter can swing faster, which means he can generate more force and hit the ball farther. Right? Not quite, as it turns out.

A batter indeed can swing a lighter bat faster, but a lighter bat has less inertia. So there’s a trade-off, says Lloyd Smith, an associate professor of engineering at Washington State University and a co-author on the paper. By once again firing a ball at a bat at WSU’s Sports Science Laboratory, the researchers found that a heavier bat still hit the ball harder (and therefore farther) than a lighter, corked bat. “Corking will not help you hit the ball farther,” says Smith.


As anyone who has played baseball really knows, a corked bat is not about hitting the ball harder. It is about being able to make a long bat lighter so that one can hit balls that would be impossible to hit with a heavy long bat.

Baseball needs to use a hard wood – so that it does not break all the time. But these are dense and heavy. Lighter woods are easier to swing quickly but more prone to breaking. (Part of the reason aluminum bats are so popular is that a long bat can still be very light.)

So there has always been a tradeoff between a long, but heavy bat that allows one to cover the entire strike zone and a shorter but light bat whose light weight lets one wait longer before starting the swing.

Corking a bat changes its density, allowing one to get the benefits of a shorter bat while maintaining the plate coverage of a long bat.

A batter using a corked bat can make good contact with a much greater range of pitches than one using either a short, light bat or a long, heavy one.

The power comes from the steroids. The cork just let them get a bat on more balls.

The researchers were really studying the wrong question. Can a corked bat be swung easier and faster? Does the change in density actually make a difference?