¤°´Stephen Hawking. AlienS`°¤

*Hawking warns about alien interaction. World renowned astrophysicist Stephen Hawking says aliens are almost certain to exist. But he warns it may be too dangerous for human beings to interact with them. The 68-year-old scientist said a visit by extraterrestrials to Earth might well be like Christopher Columbus arriving in the Americas, "which didn't turn out very well for the Native Americans."

He speculated that most extraterrestrial life would be similar to microbes, or small animals. Microbial life might exist far beneath the Martian surface, where liquid water is thought to trickle through the rock. Marine creatures might also conceivably live in huge oceans of water beneath a miles-thick layer of ice on Europa, a moon of Jupiter.

But if a scientific census could be extended beyond our solar system to the rest of the Milky Way and beyond, the odds in favor of life's existence rise dramatically, Hawking said.

"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."