The individuation begins as soon as the sound waves conveying the gunshot traverse the two meters or so between the speakers and the ears of the men. Reaction times differ. The theoretical limit of reaction time in this race, taking into account the time it takes for the sound waves to reach the ears of the sprinters and the time it takes for their brains to process those sound waves and send a signal to their muscles, is 0.1 seconds. The starting blocks each contain Omega-built pressure sensors, and if these sensors detect a push from the foot of any runner beginning less than 0.1 seconds after the gunshot leaves the speaker, that runner is tagged with a false start and the racers must line up and begin again. There is no false start this evening, August 16, 2008, deep in the Bird's Nest stadium in Beijing. It is the 100-meter finals of the XXIX olympiad, and the first man off the blocks, 0.133 seconds after the shot, is Richard Thompson, of Trinidad and Tobago. He is followed less than a thousandth of a second later by Walter Dix, of the United States. In the next three hundredths of a second, four more runners shove off against their pressure sensors. And then, finally, 0.165 seconds after the start of the race, in second to last place, Usain Bolt of Jamaica begins to run.

Luke Dittrich on Usain Bolt, at Esquire, courtesy Marginal Revolution, the rest here.