Hmmm. When I first heard this song, I didn't really know what to think. I just kinda ignored it. But now, I think I know what he is getting at:.
Life is short. Sure you might hear stories of people living to 109 but that isn't everyone. The average death age is 76. I think what he is saying is (i'll quote the song a lot here):
"I like to make myself believe that planet earth turns slowly"-He doesn't want life to pass him by. He wants to keep living.
"A disco ball is just hanging by a thread"-Pretty soon, that disco ball will fall and shatter. That is what some people think about the earth: that we will pretty soon die off and the world we know will be a barren waste land.
"It's hard to say that I'd rather stay awake when I'm asleep"- This can be taken two ways: 1- When you sleep, time seems to go quicker. We all know that. He might think that if he sleeps too much then he will miss everything and not live life as well. 2- He doesn't want to sleep because when he is awake, he is able to catch fireflies and play games and dance and have fun. He can't do that in his sleep.
That is as far as I will go on quotes, but in simple words, he is afraid to die!