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A LEADING earthquake expert has knocked down some of the myths of tenpin bowling by applying rigorous physics. While his analysis mostly confirms expert bowlers鈥� intuitive ideas on how to maximise your score, it also shows up the misleading information some manufacturers produce about their bowling balls.

Good players aim the ball a little to the side of their target, and bowl it with a sideways spin that makes it curve back and hit the pins at an oblique angle 鈥� an excellent strategy for a high score. Different types of balls behave differently, and bowling experts publish guidelines to predict their behaviour. But these are hard to interpret, says Cliff Frohlich, a geophysicist at the University of Texas in Austin, who is also a keen bowler.

To remedy this, Frohlich derived equations to simulate the motion of a bowling ball as it thunders down the lanes, using properties such as the weight of the ball, the position of its centre of mass and the frictional forces it encounters. He has also translated bowling jargon into a rigorous physical description (see Table).

Reassuringly, the simulations confirmed some of what bowling experts say makes the balls curve. For instance, when the ball is bowled to one side of the pins it will curve more sharply into them if its centre of mass is slightly offset towards the target side.

Also, most of the bowling lane is oiled for low friction, while the final part, near the pins, is dry. The simulations confirm that this helps the ball turn sharply.

But there are misconceptions too, Frohlich says. Manufacturers often imply that the behaviour of a bowling ball can be changed by making its central core from an exotic material, such as titanium. His work suggests, however, that all that matters is the material used for the surface of the ball, the position of its centre of mass and its moment of inertia (American Journal of Physics, vol 72, p 1170).

Frohlich suggests that his simulations could be used to develop flashy software that bowlers could consult when buying new balls. 鈥淭hey need an arsenal of three or four balls for different lane conditions, and when a new ball comes out, they want to try it,鈥� he says. 鈥淭here鈥檚 always the hope that the right ball could raise your score by 15 pins.鈥� But he is leaving such commercial applications to others. 鈥淚鈥檓 not a businessman by nature 鈥� if I was, I鈥檓 sure I鈥檇 be a richer man.鈥�