One day it’s gonna happen. We’ve even stuck it on our Google Calendar (tentatively busy June 15, 5,000,000,2008). On that date (give or take a few millennia), the sun will turn the last of the hydrogen in its core into helium, and voila. No more fusion. No more sunshine. Of course, at that point if the human race still exists and inhabits Earth, that’ll be the least of our worries, what with adapting our new orbit and trying to outrun the leading edge of our now likely red giant sun. But now you have a funny shirt to wear should it happen (and if the human race still comes equipped with a standard package of a torso and two arms in their respective locations).