Rockies need to brush up on their physics

Posted: Friday, May 10, 2002

The Colorado Rockies need a few physics lessons. In an effort to prevent balls from flying out so frequently from notoriously hitter-friendly Coors Field, the Rockies have been storing them for the past few weeks in a sort of giant humidor. That's not as kooky as it might sound, though the reasoning offered by the Rockies is misguided.

Rockies president Keli McGregor says that by storing the balls at 40 percent humidity they won't dry out and shrink as much as they normally would in mile-high Denver, where the humidity often is close to 10 percent. He also says the slightly soggier balls will be easier for pitchers to grip and harder for batters to hit out of the park.

That's not quite right.

Yale professor Robert K. Adair, author of ''The Physics of Baseball,'' has done experiments showing that baseballs stored at 100 percent humidity, because of the reduced elasticity of their core, bounce dramatically less than balls kept in low humidity.

''A 400-foot home run would go down to about 350 feet,'' Adair said.

But it's not that simple.

How a ball is affected by humidity is tricky. It depends on how long it is stored and at what temperature. Cold balls travel less than warm balls.

So Adair laughed heartily Wednesday when told the Rockies have been keeping the temperature in their ball chamber cranked up to 90 degrees.

''That's counterproductive!'' he said. ''I would bet the 90-degree balls go farther. The higher temperature would counteract the humidity.''

If the Rockies want to keep the ball in the park more, Adair said, they'd be better off storing them in a household refrigerator at 35 or 40 degrees and taking them out a couple of hours before game time.

''The cover and first quarter-inch would warm up,'' he said, ''but the core would remain cold and you'd have a deader ball.''

While a 90-degree room would allow balls to absorb more moisture than at a lower temperature, according to Carnegie Mellon physics professor emeritus John Fetkovich, it's not clear that it would make a difference in how the ball jumped off a bat. More important than the little extra moisture, Adair said, is the temperature of the ball's core.

Adair once tested the cold ball theory in a simple experiment at home. He put one baseball in his freezer and another in a 175-degree oven, ''to my wife's disgust,'' and left them there overnight. Then he let them sit around awhile so that when he picked them up they didn't feel different.

''I just dropped them out of the 2 1/2-story window of my study onto the concrete and the heights they bounced were radically different,'' he said. ''The one in the oven bounced much higher.''

A colleague confirmed the results with somewhat more careful experiments.

Tampering with the temperature or humidity of baseballs is neither new nor against the rules. Indeed, the Rockies' experiment has the blessing of the commissioner's office as long as it doesn't change the size and weight of the baseballs.

Adair tells an apocryphal story about John McGraw, the New York Giants manager back in the early part of the 20th century. McGraw was said to keep two sets of baseballs for home games, one stored at room temperature, the other wrapped in dry ice -- about 60 degrees below zero -- the day before the game so that the centers would still be cold. When the opposing team was at bat, McGraw tossed out a cold ball. When the Giants were up, he gave the umpire a regular ball.

''It's such a good story,'' Adair said, ''that I tend to believe it, whether it happened or not.''

The Rockies once played to the strength of their ballpark with a lineup of sluggers like Dante Bichette and Andres Galarraga. Whether it was those batters, the altitude or the humidity, the Rockies had some potent teams. But the plan to beef up their pitching staff flopped last season and the Rockies missed the playoffs for the sixth straight the year. At the moment, they're last in the NL West, regardless of the new balls.

You can look at some numbers and believe the balls are having an effect. Runs are down at Coors Field from 15.1 per game the first seven seasons to 9.8 last month. Home runs have dropped 1.42 per game from a year ago. The Rockies' pitching staff has an ERA of 3.91 in 16 home games compared with 5.68 in 15 games on the road.

Does any of that mean anything? Who knows?

''I'm very dubious about complicated statistical analyses applied to baseball,'' Adair said. ''The game changes in ways that are obscure to me. And I've studied it more closely than most.''

Instead of tampering with the balls, the Rockies would be better served working on their lineup. Rather than fighting the altitude and weather, they should embrace them. Go with fastball pitchers, who are more effective than breaking ball pitchers in thinner air, and find more home run hitters. It's more fun, anyway, when balls are flying out of the ballpark.

Steve Wilstein is a national sports columnist for The Associated Press. Write to him at

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