Instinct or aerodynamics? How Agassi decides

But there are more obscure debates in the shadows of the tennis world, and they come from an unlikely clan: scientists. Their theories are relevant to a game that is ever more dependent on technology, if all the new-fangled rackets are anything to go by.

The International Tennis Federation, or ITF, takes it seriously, holding a science and technology conference last year in London. It plans another in 2003. Take the pre-serve ball selection, for example. Agassi and a lot of players believe newer balls fly faster than old ones. Not so, says Nasa Aerodynamics expert Rabi Mehta. A new ball travels more slowly because of air friction from the fuzz on its surface, said Mehta, who has conducted tests on tennis ball speed at the Nasa Ames Research Center at Moffett Field in Californiaacirc;euro;trade;s Silicon Valley. acirc;euro;tilde;acirc;euro;tilde;The characteristics change because the fuzz on the ball wears off as you play with it. The fibers basically come off, so its drag goes down,acirc;euro;trade;acirc;euro;trade; said Mehta, who conducted the research as part of Nasa-sponsored effort to encourage students to learn physics and engineering. At the ITF conference, he said, tennis experts told him servers prefer new balls because they have more air pressure and bounce higher, and the fuzz makes them easier to control.

Still, Agassi has found a Grand Slam-winning formula, scientific or not. acirc;euro;tilde;acirc;euro;tilde;If Iacirc;euro;trade;m going to hit a kick serve with the wind, Iacirc;euro;trade;m going to go with a heavier ball because Iacirc;euro;trade;m going to force them to generate pace with a little bit heavier of a ball,acirc;euro;trade;acirc;euro;trade; Agassi said. acirc;euro;tilde;acirc;euro;tilde;If Iacirc;euro;trade;m going to hit a slice up the middle that I want to get away from them, Iacirc;euro;trade;m going to go with a thinner one thatacirc;euro;trade;s going to travel through the air a little bit quicker.acirc;euro;trade;acirc;euro;trade;

Rod Cross, a physicist at Sydney University in Australia, is challenging the widely held notion that tennis is faster on grass than on clay just because of the surface. acirc;euro;tilde;acirc;euro;tilde;I have a lot of difficulty with that idea,acirc;euro;trade;acirc;euro;trade; said Cross, a tennis enthusiast. acirc;euro;tilde;acirc;euro;tilde;I think the pace of the game depends more on how fast the players want to hit the ball as opposed to how fast it bounces off the court.acirc;euro;trade;acirc;euro;trade; Cross said he compiled statistics that showed an average first serve of male pros on Wimbledonacirc;euro;trade;s grass is 115 miles 185 kilometres an hour, while a typical serve on French Open clay is 99 miles 160 kilometres an hour.

Clay is bouncier than grass, Cross said. Players at the French slow down serves with more spin in an attempt to make the ball kick up more, according to his theory. On grass, he said, the ball wonacirc;euro;trade;t fly up as much and pros serve as fast as they can to keep the ball as low as possible. Australian Open chief executive Paul McNamee agreed that players hit flatter and faster on grass, which deadens spin. Clay court tennis, he said, is about long rallies and forcing the opponent into errors. acirc;euro;tilde;acirc;euro;tilde;That tends to make you back off just a little bitacirc;euro;trade;acirc;euro;trade; on speed, he said.

Agassiacirc;euro;trade;s final words on his ball selection for serves was decidedly unscientific. acirc;euro;tilde;acirc;euro;tilde;Thatacirc;euro;trade;s all probably just to make myself feel better,acirc;euro;trade;acirc;euro;trade; he said. acirc;euro;tilde;acirc;euro;tilde;Iacirc;euro;trade;m not quite sure it really manifests itself in a great advantage.acirc;euro;trade;acirc;euro;trade;