Olympic champion Usain Bolt, of Jamaica, points to the sky in his signature victory pose, upon his arrival as he exits his plane in Kingston, Jamaica, Monday, Sept. 8, 2008. Bolt, who won three gold medals and set world records in the 100 meters, 200 meters and the 4x100 relay at the Beijing Games, was greeted by hundreds of Jamaicans, including Prime Minister Bruce Golding, in his first visit to the Caribbean island since his starring role at last month’s Olympics. At left is Jamaica’s Sports Minister Babsy Grange. (AP/Collin Reid)

How quickly would Usain Bolt have run the 100 metres at the Beijing Olympics if he hadn’t slowed in celebration before the finish line? A team of physicists have calculated an answer: the Jamaican gold medallist could have slashed his time from 9.69 seconds to 9.55 seconds.

In the final 20 metres of the race on 16 August, Bolt extended his arms and thumped his chest in celebration, slowing himself a little. But he still broke the world record he himself had set in May.

Hans Eriksen of the Institute of Theoretical Astrophysics at the University of Oslo, Norway, and his colleagues, who normally spend their time pondering deep mysteries of the cosmos, wondered whether a few simple calculations might reveal how fast Bolt could have run.

So, in their spare time, they used television footage to measure Bolt’s positions, speeds and accelerations as well as those of the runner-up, Richard Thompson. Their measurements show both Bolt and Thompson decelerating in the final 2 seconds of the race, with a larger drop in speed for Bolt.

The team then calculated what Bolt’s time would have been had he only slowed down as much as Thompson, arriving at an answer of 9.61 seconds. But this may be too conservative, given how much Bolt outperformed Thompson in the first 8 seconds of the race. So the team also tried assuming, somewhat arbitrarily, that Bolt would have decelerated less than Thompson, by 0.5 metres per second squared in the final 2 seconds, which they say would have given Bolt a time of 9.55 seconds.

It is difficult to get precise measurements from ordinary TV footage, which records at 30 frames per second or less, says Matthew Bundle of the University of Wyoming in Laramie, who studies human locomotion. More precise human motion studies rely on cameras operating at 125 to 250 frames per second, or on tracking motion with a series of light beams which get tripped as people go by, he says. However, he thinks the team’s numbers are reasonable.

"We don’t mean to say that this is the final and ultimate result," says Eriksen. "Instead, it’s a fun application of simple physics, and we’ve done the best we can." The researchers have submitted their findings to the American Journal of Physics

After his phenomenal performance, the Jamaican, aged 22, is now known universally as ‘Lightning Bolt’. On his return to Jamaica on Wednesday for the first time since he won at Olympics, he was questioned by journalists on a range of issues. Here are some of interesting ones.

• On Asafa Powell: "Yeah we’re good friends, we mess around, we laugh, and stuff like that. But when we’re on the track it’s all about competition."

• What he said before he beat Michael Johnson’s world record: "If I’m gonna get this world record, it’s gonna be here because the track is fast. So I’m gonna just go out there and leave everything on the track."

• On next year: "I know that the US didn’t do so well so they’ll be working even harder to get back next season. Tyson Gay was injured so he’s coming back even better."

• How fast can he go: "You can’t put a limit on anything. They say anything is possible. So, I just work hard and do my best and try to stay focused and work hard."

• On Real Madrid: "They have invited me to train with them. I’ll definitely go. I think Raúl and Van Nistelrooy are some of the best goalscorers ever. I’ve watched Van Nistelrooy from when he was with Manchester United, so I know he’s a great guy."

The Scientist