Hawking says in a new Discovery Channel documentary to air next month that it seems "perfectly rational" alien beings exist, given the huge number of galaxies in the universe, The Guardian reported Monday. Mostly likely, they are no match for us -- just microorganisms or lower-level animals -- but they also could be intelligent species out to conquer a new world, he says.
"I imagine they might exist in massive ships, having used up all the resources from their home planet," Hawking said. "Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach.
"If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn't turn out very well for the Native Americans."
The Christian Science Monitor reported online, however, other scientists don't agree we should try to keep quiet and hope aliens don't spot us.
"Ignoring the possibility (alien life) and hiding your head in the sand, waiting for them to find us is certainly isn't a scientifically intelligent way to proceed or a good cultural way to anticipate something like that either," Mary Voytek, senior scientist for astrobiology at NASA, told the Monitor. "Our approach to it has been to be prepared. We're not going to get caught, say like the Native Americans when Columbus came to their shores. We've been actively listening and hopefully we get some information before any eventual encounter ever happens."