Do you know The Tortoise and the Hare (《龟兔赛跑》)? In this story, a hare and a tortoise have a race. The hare runs very fast. He is sure he will win. He takes a nap (小睡). When he wakes up, the tortoise reaches the finish line. But this is not just a story. Tortoises can win this race in real life (现实生活中), US scientists say.