As the year winds to a close, Big Think has pulled together a list of their Most Popular Videos of 2010. Perhaps the biggest thinker on the list is Stephen Hawking, the renowned theoretical physicist, who issues a stark warning. "Our only chance of long term survival, is not to remain inward looking on planet Earth, but to spread out into space." Population growth, limited resources, climate change – these pressures could drive the human race into extinction within two centuries, and possibly even one. That makes space – planets beyond our own – the next great frontier.