Are we alone? Setting some limits to our planet’s uniqueness

Are humans unique and alone in the vast universe? This question– summed up in the famous Drake equation–has for a half-century been one of the most intractable and uncertain in science. But a new paper shows that the recent discoveries of exoplanets combined with a broader approach to the question makes it possible to assign a new empirically valid probability to whether any other advanced technological civilizations have ever existed.