Billy Joel (reportedly) wrote this song because he overheard a child say that he felt sorry for "older people" like Billy Joel because no "history" happened in their lifetime, that NOW (or the time the song was written) was going to be the world's most historical time period. The comment got to Billy Joel so much that he sat down and wrote this to prove that his lifetime has been FULL of history.
We Didn’t Start the Fire by Billy Joel