It’s hard to contemplate all the things that had to go right for life to evolve on earth.  It’s also difficult for the average joe to comprehend how old our Sun is, and how long it’s got left.  It’s fun to think of the enormous amount of energy expended by the sun in a human’s lifetime…and then compare that lifetime to that of our Sun. So much energy being expended.  I’m glad we’re harnessing it as much as we can. [youtube=http://www.youtube.com/watch?v=piuKlpJmjfg&w=640&h=360] How much energy do you use and how much do you expend?  Are those two values proportional? According to NASA Astronomer …