Stephen Hawking says in his new Discovery Channel TV Show Stephen Hawking's Universe (previews May 9th at 9:00 PM) that aliens are probably real but are probably not friendly.
Hawking bases these opinions--which he admits are speculative--on probability theory and direct observation.
Given the number of possibilities for life beyond Earth, Hawking says that alien races are statistically likely. Given what usually happens when one culture drops in on another for the first time however, Hawking believes an alien visitation is probably not going to result in anything resembling peaceful sharing, space brotherhood, or warm woo woo fuzzies for all.
Hawking cites the arrival of the first white people in the Americas and the effect that exploration had on indigenous peoples as an example. Even if aliens didn't mean to harm us initially, they would likely carry germs and social practices that would detrimental to our health. They'd be looking after themselves, not us. As anyone would, really.
But the greater likelihood is that they'd drop by specifically to steal our natural resources.
After all, that's what we do.
Hawkings asks, why would aliens be any different?