What did Sosa do wrong?

He used a corked bat. To cork a bat, a player cores out a few inches of the wood from the very top of the bat, and fills the hole with a lighter substance, such as cork or sawdust. The operation makes a 33-ounce bat an ounce or two lighter. Hitters can swing a lighter bat slightly faster; in theory, the extra bat speed helps them make contact with 94 mph fastballs, and hit them farther. (Players who’ve admitted to corking insist that it added yards to their hardest-hit drives, but physicists say a lighter bat actually costs the hitter a few feet in distance.) In the past 30 years, six major leaguers have been caught with corked bats, though dozens more have gotten away with it. Perhaps the most inventive bat doctor was Graig Nettles of the New York Yankees, who in 1974 cracked his bat in half while hitting a single. Six superballs spilled out of the cored-out bat and skittered across the infield.

Why do baseball players cheat?

The national pastime is a game of supremely balanced opposing forces. Nanoseconds and millimeters can mean the difference between a Hall of Fame career and a ticket back to the minor leagues. To hit a typical major-league fastball, the batter must decide whether to swing his bat, and precisely where, just .13 of a second after the ball leaves the pitcher’s hand. If he swings .001 of a second too late or too early, he’ll hit the ball poorly and probably hit a fly ball, popout, or groundout; if he swings .003 of a second too late or too early, he’ll miss the pitch entirely. Pitchers make it harder by throwing curves, sliders, split-fingered fastballs, and other pitches that change direction in flight, dipping and darting past the bat. “You’re damn straight, hitters cheat,” says Dan Gutman in his book It Ain’t Cheating If You Don’t Get Caught.

How long has this been going on?

Cheating has been part of baseball from the very beginning—and pitchers and fielders have been just as guilty as hitters. The Baltimore Orioles of the 1890s, led by their rabidly competitive third baseman John McGraw, used to hide baseballs in the tall grass of the outfield. When opposing hitters drove a ball over the Orioles’ heads, they’d throw a hidden ball back to the infield, holding a surprised batter to a single. At third base, McGraw grabbed opposing runners’ belts to delay them; later, as a manager, he once ordered his pitchers to try holding the ball with just three fingers, to see if they could mimic the sharp curveball thrown by hurler Mordecai “Three Finger” Brown, who lost some digits in a farm accident. It didn’t work. “It’s lucky for you fellows it doesn’t,” said McGraw, “because if I thought it did, I’d have a surgeon out here tomorrow.”

What is the most popular trick?

Since baseball’s earliest days, it’s been the spitball, a pitch with countless aliases: dew drop, goo ball, gunk ball, the wet one, the damp delivery, and the old meatball. To throw a spitball, any lubricant will do—saliva, Vaseline, mud, or grease. The trick is to make the ball slippery so that it squirts out of the hand like a watermelon seed, with none of the normal backspin that makes the ball cut straight through the air. The spitball jerks about at the whim of air currents then drops suddenly as it reaches the batter. “If it’s a good ’un,” Brooklyn Dodger pitcher Preacher Roe once said, “it drops like a dead duck just as it crosses the plate.”

How hard is it to hit a spitter?

If it’s a good ’un, it’s fairly close to impossible. That’s why baseball banned spitballs way back in 1920. The disappearance of the feared greaser suddenly tipped the scales in favor of hitters, and marked the beginning of the home-run era dominated by Babe Ruth. Over the years, pitchers found ways to circumvent the prohibition on doctoring the ball. Some hid a dab of petroleum jelly on the bill of their cap. Some put a smudge of grease on their sleeve. The notorious spitballer Gaylord Perry, who won 314 games and a place in the Hall of Fame with ample help from the forbidden pitch, experimented with baby oil, axle grease, and fishing-line wax. “I reckon I tried everything on the old apple but salt and pepper and chocolate-sauce toppin’,” Perry admitted.

Aren’t cheaters ever caught?

Occasionally, yes. Perry, for example, was once thrown out of a game for throwing wet pitches—at the age of 43, after years of loading up the ball. Other pitchers have been caught with thumbtacks, nail files, and sandpaper, for producing scuffballs—pitches that break sharply because of uneven surfaces. In 1987, an umpire grew suspicious of the way Joe Niekro’s pitches were darting back and forth. As Niekro emptied his pockets, and raised his hands in the air in a “Who me?” gesture, an emery board fluttered to the ground. Niekro was suspended for 10 games. But more often than not, rule breakers get away with their crimes—including the 1951 New York Giants, who won a pennant by cheating.

How did they do that?

The Giants were trailing the Brooklyn Dodgers by 13 games that season when they installed a spotter with a telescope behind the center-field fence. The spotter read the catcher’s signs, and used a buzzer to signal whether the next pitch was a fastball, curve, or change-up. A relay man tipped off the batter with hand signals. Once the system was installed, the Giants went on a long winning streak and tied the Dodgers. In the game that decided the pennant, Bobby Thomson hit a ninth-inning home run off Ralph Branca to beat the Dodgers—“the shot heard round the world.” Asked 50 years later whether he’d been tipped to Branca’s pitch, Thomson offered this unconvincing response: “I’d have to say more no than yes.”

A new way to cheat

In the modern era, baseball players seeking an edge have changed their focus from tinkering with balls and bats to altering their own bodies. Players today weigh, on average, 20 pounds more than they did just 30 years ago, and it’s almost all muscle. A host of current and recently retired players, from David Wells to Jose Canseco to Curt Schilling, say that anywhere from 20 to 50 to 75 percent of players illegally use steroids to build their bulk, so they can hit the ball harder and amass more home runs. “Look at all the money in the game,” former major leaguer Ken Caminiti told Sports Illustrated last year. “A kid got $252 million. So I can’t say, ‘Don’t do it,’ not when the guy next to you is as big as a house and he’s going to take your job and make the money.”