I'm with Stephen Hawking on this subject:
"Stephen Hawking once said that in a universe with 100 billion galaxies, each containing hundreds of millions of stars, it is unlikely that earth is the only place where life has evolved.
"To my mathematical brain, the numbers alone make thinking about aliens perfectly rational," he said, according to The Sunday Times.
"The real challenge is working out what aliens might actually be like."
Hawking says that they could be microbes – basic animals such as worms which have been on Earth for millions of years, but suggests that extraterrestrial life could develop much further.
"We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet," Hawking said.
"I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach."
I open myself to rational thinking too, we are not alone in our universe.