Football (ball)

A football is a leather ball with which the sport football (soccer) is played. The traditional football's outer covering consists of 12 pentagons and 20 hexagons of leather sewn together. The ball is like the corresponding polyhedron (designated a truncated icosahedron), except that it is more spherical, because the faces bulge due the pressure of the air inside.

This polyhedron with 32 faces has 60 vertices (corners) and 90 edges. One easily verifies Euler's formula for polyhedra (see Leonhard Euler): 32 + 60 = 90 + 2.

It is a model for the Buckminsterfullerene (C₆₀) molecule. The diameter of the football and this buckyball are 22 cm and ca. 1 nm, respectively, hence the size ratio is 200,000,000 : 1.

Other designs for footballs exist, mainly being made up of curved strips of leather. There are also indoor footballs, which are made of one or two pieces of plastic. Often these have designs printed on them to resemble a traditional leather ball.

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In North America, the term football refers to a prolate leather ball (originally made from pigskin) which is used to play American football.