a particular species of super novanova, they're potent to meae the expansion and size of the universe. two teams, one in california and one on both coasts were working on the answer and shared the nobel prize for that recently. >> rose: are we alone? my best guest is the universe is teaming with life, and our galaxy, in particular. our galaxy is sort of proxy for other galaxies, is teaming with life, but that complex life might be much rarer. >> rose: why is that? well, here's the argument. you have the time line of the earth. earth is born. this is today. that's 4.5 billion years. put this planet out there, some are born yesterday, some at the beginning of the universe. you don't know when in the time line of the planet you will land there. here's earth. throw a dart at the time line. most the time the dart hits earth, there is only single-celled life. then we have the cam bringian explosion of life. oxygen is rocket fuel for complex life and life now has the carte blanche to become complex because the system can support it, and you get limbs and detecters like, and sensors and it's