Throughout baseball's history, rule makers have repeatedly adjusted the contest between pitcher and hitter. In 1893 the distance from the pitcher to the batter was lengthened from 55 feet 6 inches to 60 feet 6 inches, which helped the hitters. After 1968, nicknamed the "Year of the Pitcher," baseball lowered the pitcher's mound from 15 inches to 10 inches and shrank the strike zone, the area over home plate between the middle of the batter's body and the kneecaps. The pitching rubber is 60 feet, 6 inches from home plate; the strike zone has changed several times in baseball history, and the current version has been used since 1996, as of November 2026. Umpires enforce the rules and decide whether a pitch is a strike or a ball. On the bases, in 1980 Rickey Henderson broke Ty Cobb's 65-year-old American League record of 96 stolen bases with 100, and in 1982 he stole 130 bases.

The atmosphere itself participates in the contest between pitcher and hitter. Air drag takes a lot of distance off a long fly ball: one that carries 400 feet would carry approximately 700 feet if there were no drag. The Magnus force comes from air pressure that is lower on one side of a spinning ball than the other, which pushes the ball at right angles to the wind. Air in Denver is approximately 82 percent as dense as air at sea level, so the drag and Magnus forces on a baseball at Coors Field are approximately 82 percent of what they are at Fenway Park. Humid air is less dense than dry air, because a water molecule weighs less than an air molecule, so you may have heard that humid air is thicker, but it is not. A pitched baseball loses approximately 10 percent of its speed on the way to the plate: a pitch that leaves the hand at 95 mph crosses the plate at approximately 86 mph.

Equipment has also become a subject of scientific measurement. As of November 2026, the torpedo bat's shape makes it feel easier to swing, and the ball is more likely to hit the bat's thickest section, leading to a more solid hit. Also as of November 2026, a mechanical engineer who studies bats said the torpedo bat probably does not make hitters hit the ball harder or faster; balls may even go a bit slower on average. Exit velocity is the speed of the baseball as it comes off the bat right after contact, and a faster ball gives the defense less time to react. Launch angle is the vertical angle at which the ball leaves the bat: under 10 degrees is a ground ball, 10 to 25 a line drive, 25 to 50 a fly ball and over 50 a pop up.

Rule changes shape strategy. As of November 2026, pitchers are limited to two pickoff attempts or step-offs per plate appearance, and a third attempt that fails to get the runner out advances the runner a base. A Major League pitcher must face at least three batters or pitch to the end of a half-inning, with exceptions for injuries and illnesses. A team can name a player a two-way player, who is both a pitcher and a position player, can pitch in any situation, and does not count toward the team's pitcher total. A pitch timer limits the time between pitches to 15 seconds with the bases empty and 18 seconds with runners on base. Since 2023, Major League Baseball's four infielders must stay within the infield boundary when the pitcher is on the rubber, and infielders may not switch sides, as of November 2026.

Individual careers show what players accomplished within the rules of their times. Nolan Ryan set the modern single-season strikeout record of 383 in 1973, and from 1972 to 1977 he averaged 19 wins and 322 strikeouts a year, as of November 2026. Cal Ripken Jr.'s streak of 2,632 straight games, which began on May 30, 1982, is the longest by anyone in baseball history, as of November 2026. Nolan Ryan struck out 5,714 batters in his career, the most in major league history as of November 2026. Cy Young won 511 games as a pitcher, almost 100 more than any other pitcher in history, as of November 2026. In 1908 Cy Young threw his third no-hitter at 41 years and three months old, setting a record for the oldest pitcher to throw a no-hitter that stood for 82 years.

Words to know

• dense: tightly packed
• Magnus: spin-push force
• torpedo: a bat shape
• pickoff: a throw
• drag: air resistance