By Hamish Johnston
On 16 August Usain Bolt sprinted to gold in the 100 m dash at the Beijing Olympics, setting a new world record of 9.69 s.
But could he have gone faster? Many people think so because after the first 80 m of the race, when it was clear that he would win, the Jamaican appeared to stop trying and begun celebrating.
Now, four physicists in Norway have analysed video of the race and concluded that he could have covered the 100 m in as little as 9.55 s (plus or minus 0.04 s) if he had maintained his pre-celebration acceleration.
In a second calculation, the physicists argue that if Bolt had started to flag in the final 20 m — but still matched the acceleration of runner-up Richard Thompson — Bolt still would have finished in 9.61 s (plus or minus 0.04 s).
Cynics have suggested that Bolt held back so he would have a better chance at cracking the world record again, but the world’s fastest man remains silent on exactly why he appears to have stopped trying.