The Great Filter

There is a troubling silence in the universe. When we look up at the stars on a quiet night, the darkness seems peaceful, but scientists see a deeper mystery. With billions of stars in our galaxy and billions of galaxies beyond, planets are now known to be common. Many of them are in regions where life as we know it could thrive. The sheer scale makes it seem likely that intelligent life must exist elsewhere. Yet as we listen and search, we have found nothing definitive. No signals, no artifa...