You might see aliens in books and movies. They look strange. They are very smart. They travel in spaceships.

    But are there really aliens in space? British scientist Stephen Hawking, 68, thinks so. He says that people should not look for aliens. He thinks they are dangerous. On a new British TV program, Hawking says, "It is quite possible that there are aliens in space. They might live in big spaceships. They have used up all the resources（资源）from their home planet. "He thinks such aliens are sure to get resources from Earth and then go away. They may bring troubles to Earth, too.