Footballs have been made out of a variety of materials over the years, including bladders, hides, rubber, paint, leather and string. According to Timothy Gay in "Football Physics: The Science of the Game," the shape of the ball is a prolate spheroid. This flattened sphere shape not only makes for erratic bounces and encourages fumbles, it requires a specific set of materials to produce.
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The first footballs to be thrown in the 1860s were not thrown in a tight spiral. They were tossed with two hands because they were round. In the days before vulcanized rubber became a commonly produced and purchased material, footballs were made out of pig's bladders. Balls made from animal bladders were common, they were durable and they were round. They were also kind of gross so they were often encased in leather or a pigskin covering -- hence the pigskin nickname for a football to this day -- and tied closed with laces.
Rubber began to replace pig's bladders as the core of a football in the 1870s. But because rubber was new, the balls leaked a lot of air and usually became more oblong shaped and less round during the course of a game. They ended up looking more like a watermelon than anything else after 60 minutes of play. The leather and laces remained covering the ball. In 1906, the advent of the forward pass changed the game of football and the shape of the ball.
Officials in the 1930s made the ball smaller to accommodate the new passing component of the game ushered in by the forward pass. Now it could be held with one hand for a pass. Officials also kept the laces on the ball, and the leather outer covering to aid in being able to grip it effectively for passing.
The design and materials that go into a football today are testaments to how much passing has altered the game, and how big a role TV plays in the game. According to sport scientist Dan Peterson, a football weighs 14 to 15 oz. The inside rubber ball is encased in a textured leather cover to provide grip. The laces remain to also aid in gripping. The two white lines on either end of the ball make it easier to see the ball under the lights during night games, and easier for fans to see on TV.