At Wimbledon, where the London Olympic tennis tournament is being held, the fastest serve ever recorded (141 m.p.h.) was struck by American Sam Querry in 2009. Venus Williams owns the women’s fastest serve, of 129 m.p.h., clocked during her championship run in 2008. The average first-service speeds, of course, will be much lower, but they are still fast enough that players basically only have about half a second to react and return the ball. The ball’s fuzzy cover helps slow down its flight somewhat, but Wimbledon’s grass courts favor big servers because they are “faster” and the ball doesn’t bounce as high.