In many science fiction(科幻) movies, men travel to faraway stars and even fight with aliens. But are there real aliens in the universe(宇宙)? The answer of some scientists is yes. So they have been searching for aliens in outer space for many years. They hope to find life signs of aliens.
Some scientists are used to using radio telescopes to search for aliens in space. In order to find aliens,they have worked hard for over half a century, but so far they have found nothing. Then some scientists guessed aliens might not want to connect us, but alien s could answer our messages. So some scientists sent radio signals into the universe. They hope one day they would be picked up by alien technology. These scientists want to prove that we are not alone in the universe.
But what should we do if the"alien phone" rings one day? Should we answer it? Stephen Hawking,the famous physicist, thought it could be dangerous to connect aliens. He said that the main purpose of aliens' visiting to our solar system could be searching for our resources. But other scientists think we have no need to worry. David Morrison, a NASA scientist, said,"If an alien radio signal reaches the earth from a planet thousands of light-years away, then they almost surely have solved all the problems we still have including the short of resources. Maybe they are much smarter than us, but why don't they hurt us? I think we can try to connect them."
