You sit there in the stands, hot dog and beer in hand, when you hear the crack of the bat which is music to your ears. You watch as the ball is silhouetted against a crystal clear Chicago night, clearing the fences as the scoreboard explodes. The runner stomps on the plate and high-fives his teammates, as the announcer thunders the tape-measure distance of a moon-blast home run.
How do they know how far it really went?
"The challenge is that seats are rising beyond the fences," said Tom Jacobius of the Illinois Institute of Technology. "And the fences are changing their location around the field."
Jacobius may be a mechanical engineer by training, but he's a baseball fan at heart. And when the Sox came to him six years ago to come up with a foolproof method for measuring home run distances, he jumped at the challenge.
As he told it, the fans themselves had questioned the home-run derby distances at the 2002 All Star game in Milwaukee. Didn't believe them. Thought the balls most certainly had sailed farther. The 2003 Summer Classic was to be held in Chicago, and the Sox wanted a system which nailed the distances.
"There are a lot of variabilities in the angle that a ball would hit any particular location," says Jacobius, who heads up IIT's Interprofessional Projects Program, a multi-disciplinary effort where teams from various specialties come together to tackle a particular challenge. So he assembled engineers and architects and they began studying home runs, how they fly, and how they fall, from every angle.
"It's deceptive because it looks like the ball would have gone a lot further if it was a straight line, but in reality at that distance from home plate, all balls come down to rest," he said. "It reaches its apex which is the top of the curve and starts to descend, and it doesn't matter too much, within several feet, whether it seems to be a line drive or an arcing ball."
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The I-PRO team planted a surveyor's transit at home plate, and took shots to hundreds of spots between the foul poles. They then wrote an algorithm which computes the distance the ball would have flown, had it not hit something like a seat or a sign in the outfield. And computers came up with a contoured map of specific distances for virtually any place the ball will fall.
"I mean, we have measurements up the back wall," said Sox Vice-President Scott Reifert, who commissioned the study. "And there's never been a ball hit to the back wall here, but if there is, now we have it!"
Still, Reifert notes that home run distance is not an official statistic in Major League Baseball, and he knows there will always be fans who wonder about the numbers. "Here's the first rule of home run distance," he said. "It's always shorter than what people think!"
Sox slugger Jim Thome is intimately connected to those numbers. With 550 career home runs under his belt, Thome was recognized Thursday for a moon-blast he delivered exactly a year ago to dead center field. The ball struck the Sox "Fan Deck" and the IIT system determined its distance at 464 feet.
"You know, they might be wrong here and there but we won't get on them too much," laughed Thome. "You know, it's all in good fun, it's all in good fun!"
IIT said it can take the system one step further. Their team has figured out how to train cameras to respond to the crack of the bat, triangulate on the ball, follow it out of the park and calculate its trajectory and distance. That system would even provide an animation for the scoreboard. And yes, they said, they could even help a player determine the total distance, in miles, of all of his career home runs.
"I'd like to know for sure!" said Thome. "That'd be pretty cool!"
