Like so many great novel titles, this one comes directly from the Bible. More specifically, it can be found in the passage from Ecclesiastes quoted in the second epigraph (for more deets, check out "What's Up With the Epigraph?").
Basically, the title sums up the statement made in the passage quoted in the epigraph: humans are just a small and ephemeral part of a larger world. We come and go, but the earth always remains (remember, this was written in the days before global warming). The sun will keep rising and setting long after all of us are dead and gone. Real cheery, huh?