The physicist Stephen Hawking is convinced that intelligent extraterrestrials populate space, a view shared by many scientists. But his ruminations on this prospect have shifted from the aliens’ existence to their deportment. Maybe they’re dangerous.

In a film recently released online, Hawking points to the potential peril in broadcasting signals to other star systems. After all, we don’t know who is out there, and they might not be well-intentioned. If we betray our presence with signals, maybe the aliens will fire up their interstellar artillery and take us out.

According to Hawking, extraterrestrial societies could be far more advanced than we are – perhaps by billions of years. Their sympathies for us might be meagre, and they “may not see us as any more valuable than we see bacteria”.

Leaving aside the rather considerable value of bacteria, Hawking is right: we have no clue as to the intentions of putative extraterrestrials. Perhaps they live in a utopian Shangri-La similar to the one we’ve always said we want for ourselves, a place that values peace as well as the neighbours. But, of course, no one can be sure. In any Darwinian system, there’s always a benefit to aggression by some. So maybe a warning is warranted. Who would want to make their mark as the person who triggered the destruction of Earth in a misguided attempt to start an interspecies conversation?

Read the rest at https://www.theguardian.com/commentisfree/2016/sep/27/stephen-hawking-li...