London, Sep 2 (IANS): The secret behind the "best free kick" ever in football, by Brazilian player Roberto Carlos, which saw the ball curve around 30 feet and land inside the goal post, has finally been revealed.
Considered one of the most incredible goals in international football, the free kick was no fluke, physicists have claimed, according to the Daily Telegraph.
Roberto Carlos kicked a shot from 115 feet against France in 1997 which was seemingly heading for the corner flag but it "curved like a banana" to land in the net. The bend was so pronounced that French goalkeeper Fabien Barthez made no move for the ball, thinking it would go away safely.
Even a ball boy standing 30 feet away from the goal ducked thinking it was going for him until the ball made a last moment sweep and landed in the back of the net.
Though the free kick was written off by many as an "incredible lucky chance" and that it must have been helped by a gust of wind, scientists have now applied the laws of physics to settle the debate.
Using tiny plastic balls and a slingshot, a research team from the École Polytechnique in Palaiseau near Paris varied the velocity and spin of balls travelling through water to trace different trajectories.
While their research confirmed the long known "Magnus effect", which gives a spinning ball a curved trajectory, it also revealed a fresh insight for spinning balls that are shot over a distance equivalent to Carlos' free kick.
The friction exerted on a ball by its surrounding atmosphere slows it down for the spin to take on a greater role in directing the ball's trajectory, thereby allowing the last moment change in direction, which in the case of Carlos' kick left Barthez stunned.
"Carlos' kick started with a classical circular trajectory but suddenly bent in a spectacular way and came back to the goal, although it looked out of the target a small moment earlier," Christophe Clanet and David Quéré, researchers from École Polytechnique, said.
"People often noticed that Carlos' free kick had been shot from a remarkably long distance, we show in our paper that this is not a coincidence, but a necessary condition for generating a spiral trajectory," they added.
The research paper was published Thursday in the New Journal of Physics.