Stephen Hawking is one of the world's leading scientist in the theoretical physics and cosmology.
He stated in his new documentary series Into The Universe with Stephen Hawking that extraterrestrials are almost certain to exist - but that instead of seeking them out, humanity should be doing all it that can to avoid any contact. Hawking's logic on aliens is, for him, unusually simple. The universe, he points out, has 100 billion galaxies, each containing hundreds of millions of stars. In such a big place, Earth is unlikely to be the only planet where life has evolved. "To my mathematical brain, the numbers alone make thinking about aliens perfectly rational," he said. "The real challenge is to work out what aliens might actually be like." Hawking believes that contact with such a species could be devastating for humanity. He suggests that aliens might simply raid Earth for its resources and then move on and concludes that trying to make contact with alien races is "a little too risky". He said: "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."
And he is not alone. Professor Brian Cox (Wonders of the Solar System) and Lord Rees (The Astromonmer Royal) are a few that agree with Stephen Hawking.
Don’t talk to aliens, warns Stephen Hawking—The Times: The Sunday Times
Wonders of the Solar System—Aliens (2010)
Royal astronomer: 'Aliens may be staring us in the face'—The Telegraph