Stephen Hawking warns not to make contact with visitors from out of space. The British scientist said "If aliens visit us, the outcome could be the same as when Columbus landed in America - which didn't turn out well for Native Americans". He's in a new television series which explores a fictitious world where aliens invade earth in huge spaceships looking for resources after depleting their own planet. It's called Into the Universe on the Discovery Channel which has just started in the US.
He suggests that these very advanced alien invaders could become nomads looking to conquer and colonise whatever planet they can reach. Does he really think there could be aliens out there? "To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is to work out what aliens might actually look like" he said.
So far scientists haven't found any evidence that aliens exist but in 2008, NASA beamed the Beatles song "Across the Universe" into deep space to send a message of peace to any alien that happens to be in the region of Polaris - also known as the North Star - in 2439.