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A football is a ball inflated with air that is used to play one of the various sports known as football. In these games, with some exceptions, goals or points are scored only when the ball enters one of two designated goal-scoring areas; football games involve the two teams each trying to move the ball in opposite directions along the field of play. The first balls were made of natural materials, such as an inflated pig bladder, later put inside a leather cover, which has given rise to the American slang-term "pigskin". Modern balls are designed by teams of engineers to exacting specifications, with rubber or plastic bladders, and often with plastic covers. Various leagues and games use different balls, though they all have one of the following basic shapes: # a sphere: used in Association football and Gaelic football # a prolate spheroid # * either with rounded ends: used in the rugby codes and Australian football # * or with more pointed ends: used in American football and Canadian football The precise shape and construction of footballs is typically specified as part of the . The oldest football still in existence, which is thought to have been made circa 1550, was discovered in the roof of Stirling Castle, Scotland, in 1981.〔(【引用サイトリンク】title=Scottish Cup – World's Oldest Football )〕 The ball is made of leather (possibly from a deer) and a pig's bladder. It has a diameter of between , weighs and is currently on display at the Smith Art Gallery and Museum〔(【引用サイトリンク】title=Collections – Stirling Smith Art Gallery and Museum )〕 in Stirling. ==American and Canadian football== (詳細はcollegiate football. Footballs used in recreation, and in organised youth leagues, may be made of rubber or plastic materials (the high school football rulebooks still allow the inexpensive all-rubber footballs, though they are less common than leather). Since 1941, Horween Leather Company has been the exclusive supplier of leather for National Football League footballs. The arrangement was established by Arnold Horween, who had played and coached in the NFL. Horween Leather Company also supplies leather to Spalding, supplier of balls to the Arena Football League. Leather panels are typically tanned to a natural brown color, which is usually required in professional leagues and collegiate play. At least one manufacturer uses leather that has been tanned to provide a "tacky" grip in dry or wet conditions. Historically, white footballs have been used in games played at night so that the ball can be seen more easily; however, improved artificial lighting conditions have made this no longer necessary. At most levels of play (but not, notably, the NFL), white stripes are painted on each end of the ball, halfway around the circumference, to improve nighttime visibility and also to differentiate the college football from the pro football. However, the NFL once explored the usage of white-striped footballs – in Super Bowl VIII. In the CFL the stripes traverse the entire circumference of the ball. The UFL used a ball with lime-green stripes. The XFL used a novel color pattern, a black ball with red curved lines in lieu of stripes, for its footballs; this design was redone in a tan and navy color scheme for the Arena Football League in 2003. Two indoor American football leagues, the Ultimate Indoor Football League and American Indoor Football, use a ball with red, white and blue panels. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Football (ball)」の詳細全文を読む スポンサード リンク
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