Carla Murphy is known in certain circles as a 'zorbanaut'. This is because she spends some of her free time inside a large inflatable plastic ball called a "zorb". "Zorbing is so much fun, I just can't get enough," she says. Zorbing involves rolling down a steep hill strapped inside the ball, along with up to two other people. The ball can reach speeds of up to 50 or 60 kmph if the hill is steep enough. "It's fantastic. You bounce around as if you're weightless. But it's safe, too. Even if you hit a rock, you will not get hurt, because you're totally protected from bumps and knocks by the zorb. Anyone from 6 to 60 can do it," Carla explains. This bizarre activity originated in New Zealand and now there are centres all around the world. Carla thinks it's great. "When we start rolling, we just start laughing and we can't stop."