Football is the world's most popular sport. This summer's World Cup will be watched on television by hundreds of millions of viewers, many of whom play the game themselves. Given this level of interest, it is remarkable how little attention has been paid to the scientific aspects of the game. Golf and cricket, for example, have been much better served. But for the physicist, the mechanics and aerodynamics of football pose a wide variety of interesting questions.
When the topic of the physics of football does come up, it is usually the curved flight of the ball that is discussed. During the 1974 World Cup, for example, television viewers were amazed by the stunning "banana kick" by Brazil's Roberto Rivelino. Since then, the ability to "bend" a ball has become accepted as one of the skills of the game.
But fans never tire of seeing an expertly struck curved ball. In 1997 supporters around the world were mesmerized by a particularly remarkable curled shot produced by another Brazilian - Roberto Carlos - in a match against France. His shot, taken from a free kick some 30 metres from the opponent's goal, cleared the wall of defenders by at least a metre, before curving back and landing in the top corner of the French goal. England fans will be hoping that David Beckham - the current master of the art - will pull off similar tricks this summer, provided that the broken bone in his foot has healed.
In the May issue of Physics World, retired theoretical physicist John Wesson gets to grips with the physics of the banana kick and other football tricks.