A baseball is a ball used in the sport of the same name, baseball. The ball features a rubber or cork center, wrapped in yarn, and covered, in the words of the Official Baseball Rules "with two strips of white horsehide or cowhide, tightly stitched together." It is 9.00–9.25 inches (228.60–234.95 mm) in circumference, (2.86–2.94 in or 72.64–74.68 mm in diameter), and masses from 5.00 to 5.25 ounces (141.75 to 148.83 g). The yarn or string used to wrap the baseball can be up to one mile (1.6 km) in length. Some are wrapped in a plastic-like covering.
A significant characteristic of the baseball is the stitching that holds together the covering of the ball. After a ball has been pitched, these raised stitches catch the air and cause the ball to swerve slightly on its way to the catcher. Whether the ball swerves to the right, to the left, downward, or a combination thereof, and whether it swerves sharply or gradually, depends on which direction, and how fast, the stitches have been made to spin by the pitcher. See, for example, curveball, slider, two-seam fastball, four-seam fastball, sinker, cutter.
In the early, mid-1800s days of baseball, there was a great variety in the size, shape, weight, and manufacturing of baseballs. Early baseballs were made from a rubber core from old, melted shoes, wrapped in yarn and leather. Fish eyes were also used as cores in some places. Pitchers usually made their own balls, which were used throughout the game, softening and coming unraveled as the game went on. One of the more popular earlier ball designs was the "lemon peel ball," named after its distinct four lines of stitching design. Lemon peel balls were darker, smaller, and weighed less than other baseballs, prompting them to travel further and bounce higher, causing very high-scoring games.
In the mid-1850s, teams in New York met in attempt to standardize the baseball. They decided to regulate baseballs to weighing between 5.5-6 oz and having a circumference of 8-11 inches. There were still many variations of baseballs since they were completely handmade. Balls with more rubber and a tighter winding went further and faster (known as "live balls"), and balls with less rubber and a looser winding (known as "dead balls") did not travel as far or fast. This is generally true for all baseballs. Teams often used this knowledge to their advantage, as players from the team usually manufactured their own baseballs to use in games.
There is no agreement on who invented the commonplace figure-8 stitching on baseballs. Some historians say that it was invented by Ellis Drake, a shoemaker's son, to make the cover stronger and more durable. Others say it was invented by Colonel William A. Cutler and sold to William Harwood in 1858. Harwood built a factory in Natick, Massachusetts, and was the first to popularize and mass-produce baseballs with the figure-8 design.
In 1876, the National League (NL) was created, and standard rules and regulations were put in place. A.G. Spalding, a well-known baseball pitcher who made his own balls, convinced the NL to adopt his ball as the official baseball for the NL. It remained that way for 100 years.
In 1910, the cork-core ball was introduced. They outlasted rubber core baseballs; and for the first few years they were used, balls were hit farther and faster than rubber core balls. It eventually went back to normal. Pitchers adapted with the use of the spitball, which is now illegal, and an emphasis on changing the ball.
In 1920, a couple of important changes were made to baseballs. They began to be made using machine winders and a higher grade of yarn from Australia. Although there was no evidence that these balls impacted the game, offensive statistics rose throughout the 1920s, and both players and fans believed that the new balls helped batters hit the ball farther.
In 1925, Milton Reach patented his "cushion cork" center. It was a cork core surrounded by black rubber, then another layer of red rubber.
In 1934, The National League and American League came to a compromise and standardized the baseball. They agreed on a cushion cork center; two wrappings of yarn; a special rubber cement coating; two more wrappings of yarn; and, finally, a horsehide cover.
Baseballs have gone through only a few small changes since the compromise. During World War II, the US banned the use of rubber for non war-related goods, including for baseballs. So in 1943, instead of using rubber, baseballs were made with rubberlike shells of balata; a substance, obtained from a particular type of tropical tree, that was also used in golf balls. Hitting declined significantly in 1943.
The introduction of synthetic rubber in 1944 resulted in baseballs returning to normal. Offense would return to normal after the change back to the regular ball and return of players from active duty.
Cushioned wood cores were patented in the late 19th century by sports equipment manufacturer Spalding, the company founded by former baseball star A.G. Spalding. In recent years, various synthetic materials have been used to create baseballs; however, they are generally considered lower quality, stiched with two red thick thread, and are not used in the major leagues. Using different types of materials affects the performance of the baseball. Generally a tighter-wound baseball will leave the bat faster, and fly farther. Since the baseballs used today are wound tighter than in previous years, notably the dead-ball era that prevailed through 1920, people often say that the ball is "juiced". The height of the seams also affects how well a pitcher can pitch. Generally, in Little League through college leagues, the seams are markedly higher than balls used in professional leagues.
In the early years of the sport, only one ball was typically used in each game, unless it was too damaged to be usable; balls hit into the stands were retrieved by team employees in order to be put back in play, as is still done today in most other sports. Over the course of a game, a typical ball would become discolored due to dirt, and often tobacco juice and other materials applied by players; damage would also occur, causing slight rips and seam bursts. This would lower the offense during the games giving pitchers an advantage. However, after the 1920 death of batter Ray Chapman after being hit in the head by a pitch, perhaps due to his difficulty in seeing the ball during twilight, an effort was made to replace dirty or worn baseballs.
In 1909, sports magnate and former player Alfred J. Reach patented the ivory centered "ivory nut" in Panama and suggested it might be even better in a baseball than cork. However, Philadelphia Athletics president Benjamin F. Shibe, who had invented and patented  the cork centered ball, commented, "I look for the leagues to adopt an 'ivory nut' baseball just as soon as they adopt a ferro-concrete bat and a base studded with steel spikes." Both leagues adopted Shibe's cork-centered ball in 1910.
The official major league ball is made by Rawlings, which produces the stitched balls in Costa Rica. Attempts to automate the manufacturing process were never entirely successful, leading to the continued use of hand-made balls. The raw materials are imported from the United States, assembled into baseballs and shipped back.
Throughout the 20th Century, Major League Baseball used two technically identical but differently marked balls. The American League had "Official American League" and the American League's president's signature in blue ink, while National League baseballs had "Official National League" and the National League president's signature in black ink. According to Bob Feller, in the 1930s, when he was a rookie in the National League, baseball laces were black, intertwined with red; the American League's were blue and red. In 2000, Major League Baseball reorganized its structure to eliminate the position of league presidents, and switched to one ball specification for both leagues. Under the current rules, a major league baseball weighs between 5 and 5 1⁄4 ounces (142 and 149 g), and is 9 to 9 1⁄4 inches (229–235 mm) in circumference (2 7⁄8–3 in or 73–76 mm in diameter). There are 108 double stitches on a baseball, or 216 individual stitches.
Today, several dozen baseballs are used in a typical professional game, due to scratches, discoloration, and undesirable texture that can occur during the game. Balls hit out of the park for momentous occasions (record setting, or for personal reasons) are often requested to be returned by the fan who catches it, or donated freely by the fan. Usually, the player will give the fan an autographed bat and/or other autographed items in exchange for the special ball.
There are different types of baseball used.
There are several historic instances of people catching, or attempting to catch, baseballs tied to MLB milestones:
Other famous baseballs:
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