Because it take about 3 generations of stars to build enough carbon to the point where life is possible, roughly 9 billion years, our Earth therefore was among one of the first planets that housed enough carbon to make life possible. Stars will continue to exist for hundreds of billions of years. But according to Paul Davies in his book the Cosmological Jackpot: And Alex Vilenkin in his book Many Worlds in one puts the limit on the life span of matter at In other words, life might be possible from 9 * 109 to 1031 and we live practically at the beginning of that span. I find this fishy. Does anyone else? I'm not sure what this fact means, but I'm interested to hear what other people have to say.