Synthetic plastics and rubbers were very instrumental in the winning of World War II. Bronze is an alloy of copper and tin (not more than 11% tin). It was invented over 4000 years ago. Silver was first used when smelting was developed during the Bronze Age. Its symbol, “Ag,” was derived from the Latin “argentum,” meaning “white and shining.” Gold naturally occurs in a pure state. It was made into ornaments by the Egyptians as early as 3000 BC. Four umpires, one at each base, call balls and strikes, fair and foul balls, and safe or out. The referee, who controls the game from the field, is assisted by two linesmen, one on each sideline. The number of officials on the field increases from high school to college to professional games. College games use two referees; professional games require three. The string side of the bow is called the “belly”; the other side is called the “back.” An outdoor game for most of its history. Indoor bowling became popular in the mid-19th century. Men compete in floor exercise, pommel horse, rings, vault, parallel bars and high bar. Women compete in uneven parallel bars, vault, balance beam and floor exercise. Believed to have originated in India in a version called “poona.” The shuttlecock is hit back and forth over a net with rackets. Modern croquet evolved from paille-maille in France in the early 19th century, reaching England about 1850 and the U.S. shortly thereafter. The first world championships were held in London in 1926. Wimbledon was first played in 1877. The first U.S. championship was held in Newport, Rhode Island in 1881. Originated in Scotland. The first golf course in the U.S. was the St. Andrews Golf Club of Yonkers, N.Y., in 1888. Developed from the ancient game of quoits or a similar ringtoss game. Dates back to mid-19th century Canada. The first formal game was played in Kingston, Ontario in 1855. Developed in Spain, brought to Cuba in 1900 and Miami in 1924. The curved wicker basket is called a “cesta.” Believed to have originated in ancient Persia. “Polo” comes from the Persian “pulu,” meaning “willow root,” from which balls were made. Originated in contests among various North American Indian tribes. Players throw or bat the ball into the goal, but may also kick it in. Probably the most popular sport in the world, soccer originated in England. It became an Olympic event in 1908. Invented in 1895 by YMCA physical fitness director William G. Morgan in Holyoke, Massachusetts. Became an Olympic event in 1964. Until 1936, two-handed standing shots were the norm. In that year, a Stanford University team playing in a Madison Square Garden promotion wowed audiences with the one-handed jump shot. As the new style quickly grew popular, scores rose dramatically. Derived from rugby and soccer, football rivals baseball as the most popular athletic event for spectators in the U.S. Evolved from cricket and rounders. Abner Doubleday is credited with inventing the sport while a schoolboy in Cooperstown, N.Y., but it has not been proven that Doubleday was ever in Cooperstown in his life. Teams of four athletes run separate distances, exchanging a baton within designated zones. Early poles were made of wood. Modern poles are made of fiberglass. The javelin point must land first for a throw to be considered legal. Takeoffs must be from one foot. The “Fosbury Flop” was popularized by Dick Fosbury, who won the gold in the 1968 Olympics. Bob Beamon’s record leap in the 1968 Mexico City Olympics stood for 23 years. The hammer weighs 16 lbs (7.26 kg) and consists of a metal ball attached to a handle by a steel wire. The men’s shot put weighs 16 lbs (7.2 kg); the women’s, 8 lbs 13 oz (4 kg). The most popular style is called the “O’Brien” technique. Popular in the ancient Greek Olympics. The men’s discus weighs 2 kg (4 lb, 6.55 oz); the women’s 1 kg (2 lb, 3.27 oz). Men’s hurdles have 10 barriers in 110 meters (120.3 yds); women’s hurdles have 8 barriers in 100 meters (109.4 yds). Diving from high platforms became an Olympic event in 1904; from low springboards, in 1908. An Olympic event since the start of the modern games in 1896. Sailing’s premier race, the America’s Cup, tests both sailing ability and yacht design technology. Developed on England’s Thames river. The first U.S. race was held in New York City in 1811. Developed as a sport on the lakes of Scotland and the canals of the Netherlands. World-class downhill racers reach speeds of nearly 161 kph (100 mph). Only men compete in this event. There are two competitions, one yielding jumps of around 71 m (78 yds), the other yielding jumps over 91 m (100 yds).