Human Speed Limit? We're Nowhere Near It

Jamaica's Usain Bolt (right) won the men's 100-meter final race in the world track and field championships Sunday in Berlin in 9.58 seconds, just ahead of the U.S.'s Tyson Gay.
Jamaica's Usain Bolt (right) won the men's 100-meter final race in the world track and field championships Sunday in Berlin in 9.58 seconds, just ahead of the U.S.'s Tyson Gay.