Blue and Green: In this weeks featured TED talk Lord Martin Rees, astronomer royal and former master of Trinity College, Cambridge, describes the existential threats that could spell the end of humanity.
This century, he observes, is the first where the fate of the entire world lies in the hands of just one species ours.
While we all worry about minor dangers, our species is in denial about the possibility of truly cataclysmic scenarios.
Its not just the nuclear threat, he explains.
In our interconnected...