Bowls: Overcoming the natural bias in bowls

Compared with some sports, lawn bowls is usually played in a state of calm fairness, but that doesn't mean there isn't any bias involved.

The sport originated in England and dates back to the 13th century.

It derived from boules, a group name given to games that involved tossing or rolling weighted balls towards a target, such as the popular French game petanque.

Bowls is played on a rectangular grass or synthetic surface. In simple terms, the object of the game is to roll your ball, or bowl, as close as possible to a small white target called a jack.

It sounds easy enough, but the critical aspect of the game is that the bowls are asymmetrically weighted, meaning they curve to one side while in motion. This is called the bias, and there is a great deal of complicated science to it.

The weighting is achieved by shaping rather than adding mass to the bowl, so that one side is larger - and therefore heavier - than the other.

This uneven weight distribution means the centre of gravity of the bowl is offset by anywhere between 0.75mm and 0.9mm.

According to Rod Cross, a physicist from the University of Sydney, the design of a bowl is governed by a concept called 'prescessing', which is defined as the motion of the axis of a spinning body.

As Cross points out, the axis of rotation of a bowl as it travels along a green is not fixed. Rather, the processional motion - that is, the rotation - is coupled with the simpler linear motion of the bowl as it travels forward.

The first step to successful bowling is to deliver the bowl with the bias on the correct side. Because of the uneven weighting, the bowl will move in a curved motion towards the biased side, or the larger and heavier side.

The art of the sport is in judging the curvature of the path the bowl will take as it rolls towards the jack. If the bowl is delivered too straight, it will veer away from the jack. If delivered at too wide an angle, it won't curve back enough towards the target.

The science of bowls doesn't stop with the bowl itself. The delivery action of a bowler moves from high to low as he or she crouches into the release, thus combining gravitational energy and muscular force to propel the bowl.

But more significant is the green itself, in particular its retarding force on the moving bowl. The condition of the green - how well manicured it is, whether it is lush or dry - has a direct bearing on the amount of friction the bowl encounters.

The less friction, the faster it will roll, which goes some way to explaining why so many bowls end up in the deep traps that surround the green.

According to Rob Judson, an Australian bowls coach and bowls science guru, the energy of a travelling bowl is converted into heat, which slightly raises the temperature of the green under it.

As the green absorbs the bowl's energy, it also acts as a breaking force, which ultimately stops it.

How close to the jack, though, is dependent on more than just physics. Successful bowling also needs a few intangibles common to a range of sports - a good eye, a dose of luck and the rub of the green.