Of all the acts in baseball's version of the Circus Maximus, the one in center ring tonight -- the Home Run Derby -- pays homage to power in prime time. It's like the reverse human cannonball, involving human stars launching cannon shots. And this one has the splashy anticipation of seeing how many baseballs go kerplunk on the fly into the Allegheny River.

		Graphic: What happens with the bat and ball during a home run Multimedia: How to make a home run splash

But according to some who study such things as ball flight, achieving splashdown will be a long shot in more ways than one.

"Oh, yes. That will be exciting. People can say they saw something if a ball reaches the river," said Robert Adair.

As professor emeritus of physics at Yale University, Dr. Adair will watch the festivities with a different eye. For three years ending in 1990, he was the official physicist of the National League under Commissioner A. Bartlett Giamatti, and he wrote the book "The Physics of Baseball."

He's the first to say that getting too technical about the act of swatting a home run takes away some of the unadulterated joy of watching the coordinated, uppercut swing of a wooden bat compressing a thrown ball into an oval shape for a split second before the elasticity of the cork, yarn and hide sphere begins its parabolic flight.

In fact, while the mechanics of hitting a ball in the air a long way are something that reasonably intelligent people know instinctively, science can only go so far in explaining the home run using the immutable laws of mathematics.

"It's simple in detail but impossible to explain," said Dr. Adair.

While Ted Williams could go on expansively about the art of hitting, most baseball players do it on feel: See the ball, hit the ball. Yogi Berra once said, in Lawrence's Law, that you can't hit and think at the same time. And Willie Stargell once mused in Pops' Postulate on the mythology of baseball:

"They give you a round bat, and they throw you a round ball, and they tell you to hit it square" (a quote also attributed to Williams and all-time hits leader Pete Rose.)

Back in the day, the home run was not the be-all and end-all of the game. Old school fans like Dr. Adair get more excited by a crisp, smooth double play. Others favor the well-pitched game. Even Hammerin' Hank Aaron, the most prodigious home run hitter in the major leagues, opined that the triple was the most exciting play in baseball.

"Home runs win a lot of games, but I never understood why fans are so obsessed with them," he said.

Perhaps, but it would be tough to sell commercial spots for Singles Derby, or Pitcher's Fielding Practice Derby, or Bunting Derby, or Relay Throws From the Outfield Derby. Slugfests sell. Baseball is charging a $100 minimum to watch what amounts to glorified batting practice, and sponsors are all lined up so ESPN's Chris Berman can make his signature staccato call of "Back, back, back, back, back." For some, the derby is bigger than the game.

Ever since Babe Ruth changed the game, home runs have inspired.

Ruth's Rule on how to put a charge into one went like this: "I swing as hard as I can, and I try to swing right through the ball. ... The harder you grip the bat, the more you can swing it through the ball, and the farther the ball will go. I swing big, with everything I've got. I hit big or I miss big. I like to live as big as I can."

Baseball has its own colorful language for everything.

But the home run is in its own league with such descriptions as big fly, blast, dinger, jack, johnnie, moonshot, tater, wallop, gopher ball, going yard and dialing 8 (for the long-distance button on hotel phones). Nicknames have evolved from Sultan of Swat to Joltin' Joe and Hammerin' Hank.

Announcers get in on the act. Longtime Pirates fans will recall Rosey Rowswell's "Open the window, Aunt Minnie, here she comes," accompanied by the sound of breaking glass. Bob Prince would intone "kiss it goodbye" and Lanny Frattare implores it to "Go ball. Get outta here!"

Old-timers will recall the Ralph Kiner days in Pittsburgh. He played on some awful Pirates' teams, but fans stayed put late in losing causes just to see him bat, and they exited in droves when he was done.

There are varying opinions on how many baseballs will get wet tonight. Tony Gwynn, in town to raise attention to the medical cause of deep-vein thrombosis, is of the mind that the sluggers will rule.

"You're going to find out how small that ballpark is when these guys get through," he laughed.

But in the 449 or so games played at PNC Park, only one ball reached the water on the fly in meaningful competition. When he was with Houston, Daryle Ward did it off Kip Wells on July 6, 2002. The ball carried an estimated 479 feet, and Mr. Ward said later: "That's a long shot."

Just last week, Carlos Delgado laughed out loud when asked the prospects of a watery end during the derby.

"Ha! Good luck! People don't realize until they try how far that is," he said.

In San Francisco, site of next year's derby, it's 352 feet into the drink in McCovey Cove. That's a routine flyout in center and the power alleys in Pittsburgh.

At PNC Park, the shortest distance from home plate to the river's edge is 455 feet -- a howitzer shot that must clear the 21-foot high wall, the grandstand, the concrete concourse and the river park. If you're making a bar bet with Pete Rose, you might consider the "under."

For one thing, only two of the eight derby participants will be hitting from the left side -- Boston's David Ortiz and Philadelphia's Ryan Howard. Houston's Lance Berkman, a switch hitter, plans to hit right-handed.

Each slugger can have the batting practice pitcher of his choice during the competition and can opt to swing at only those offerings in their power zones. But participants are rewarded for how many homers they hit, not if they fly to the river, and it would be a risky strategy to try to go the shortest route, along the right field foul line. A ball could reach the water, but if it's foul by the fuzz on a tick's ear, it's an out.

A lot will depend on the variables, according to Dr. Adair.

Warmer air is lighter, so the same ball struck at 80 degrees will fly five feet longer than a ball hit when it's 70. In addition, a ball heated to 80 degrees will be in the air longer than one with a temperature of 70 degrees, which could explain the derivation of a hot hitter.

The wind will be a factor. The Pirates did a wind study of the ballpark site that showed the prevailing winds blow from left to right at 10 to 15 mph. With an average tailwind of 10 mph, you can add about 30 to 35 feet in distance. If it's blowing in, forget it.

A baseball is hardly an aerodynamic model, which is why artillery shells don't look like cannonballs anymore. But if a slugger can generate roughly 10,000 pounds of force from his bat and impart underspin during the 1/1,000th of a second the wood is on the baseball, the stitches act like dimples on a golf ball. They allow the ball to sail. A baseball that travels 400 feet would go only 300 feet without the stitching, Dr. Adair said.

By the way, the professor said that ash and maple wood are pretty much the same. Most professional hitters swing a 35-ounce bat, which pales in comparison to the 56-ounce cudgel that Babe Ruth uncoiled to bludgeon the ol' potato.

Of course, this being the Steroid Age, other variables have crept into the home run picture, adding new nicknames like "The Unnatural." The current and former single-season home run kings, Barry Bonds and Mark McGwire, have been mentioned in the public prints during the steroid mess. And it would take the official pharmacist of baseball to determine if bat speed is best helped by stacking testosterone cypionate, testosterone enanthate, equipoise and Winstrol as opposed to a mix of growth hormone, EPO, insulin, norbolethone, Winstrol, trenbolone and flaxseed oil.

Noted author Jose Canseco has crashed this party, so he might be able to expand on that.

At any rate, home runs seem to go longer over time. Any number of Web sites will list tape measure shots of more than 600 or 700 feet. But Dr. Adair, a man bound by the scientific method, chuckles at what he calls a "long history of lies."

The longest ball he knows of was struck by Mickey Mantle on April 17, 1953, at Washington's Griffith Stadium. The ball glanced off a beer sign on an auxiliary football scoreboard. It was walked off at 565 feet or more, but that was apparently the distance after it stopped rolling. For the record, Mantle's blast went about 510 feet behind a good trailing breeze.

People are still talking about the 509-foot blast Frank Thomas hit during the 1994 derby in Three Rivers Stadium, of which it is said that they now show movies on flights that long. The longest ball hit to date at PNC Park was smote by Sammy Sosa on April 12, 2002, off Dave Williams. Its distance was estimated at 484 feet, which prompted then-manager Lloyd McClendon to note, "I didn't think it was ever going to come down."

All of this will be good fodder for future discussions if the Allegheny is violated.

"For a few hours [tonight], a lot of people will stop worrying about their troubles while watching the show, which is not a bad thing," Dr. Adair said, sounding more like a fan than a man of science.

It's not only chicks who dig the long ball, as the old Nike ad once proclaimed.

In the words of Richard Ben Cramer, the Pulitzer Prize-winning author of a biography of Joe DiMaggio, describing America: "We love power. It's about how we see ourselves. It's how we're good when we're very good -- with overwhelming force."