JohnQ
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The shape of the American football derived from the shape of the rugby ball, a European sport from which football was based. The rugby ball got its shape because in the days before rubber, other natural materials had to be used that could be inflated and hold the air in. The material used for early rugby balls was a pig’s bladder, which is about twice as long as it is wide. The football was later tweaked to the American style of play, but it kept a piece of its origins with the nickname pigskin.
The exact term for the shape of an American football and a rugby ball is prolate spheroid, even though the two balls are of different design, today. A prolate spheroid describes an object that is essentially round, but is longer than it is wide. Rugby was a sport that was imported to the United States in the mid 1800s. It began to be played at Ivy League universities in the 1860s.
By 1875, the rules had changed enough from those of rugby for football to be considered a separate sport, but the balls were made nearly the same with an inner bladder covered with an outer leather shell tied together with laces. Sometime in the 1860s, the pig’s bladder was replaced by a leather or rubber bladder, and the ball gradually became more elongated so it could be carried more easily.
The American football has much more in common with the original rugby ball than does the modern rugby ball. Modern rugby balls are now made with synthetic materials, including plastic, polyester and latex. American footballs are still made of natural leather.
Today, the football is standardized for use by the NFL and the NCAA, but there is some slight variation. It is 11 to 11.5 inches long and has a center circumference of 28 to 28.5 inches. The ends are from 20.75 to 21.25 inches in diameter, and the ball weighs from 14 to 15 ounces. One difference between pro footballs and college footballs is that college balls have white lines painted halfway around each end. High school footballs have the white lines painted all the way around each end.
 Posted 4807 day ago
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