Physicists have revealed that Brazilian Roberto Carlos's 1997 free kick-dubbed the greatest free kick-against France was not a fluke.

A French team of scientists discovered the trajectory of the goal and developed an equation to describe it.

They say it could be repeated if a ball was kicked hard enough, with the appropriate spin and, crucially, the kick was taken sufficiently far from goal.

Roberto Carlos scored his wonder goal during the inaugural match of the Tournoi de France, a friendly international football tournament that was held in France ahead of the 1998 World Cup.

Many pundits referred to it as "the goal that defied physics", but the new paper outlines the equation that describes its trajectory exactly.

"We have shown that the path of a sphere when it spins is a spiral," the BBC quoted lead researcher Christophe Clanet from the Ecole Polytechnique in Paris as saying.

Clanet described this path as a "snail-shell shaped trajectory", with the curvature increasing as the ball travels.

Because Roberto Carlos was 35m (115ft) from the goal when he kicked the ball, more of this spiral trajectory was visible.

So the apparently physics-defying sharp turn of the ball was actually following a naturally tightening curve.

The study has been published in the New Journal of Physics. (ANI)