What are the motifs in Lucifer's Hammer by Larry Niven?

Coming of age is a recurring idea in the story. For several of the characters, this novel serves as a typical coming of age story. Andy is one of the first to come to mind. As the story opens, Andy is nothing more than an indulged teenager. His father says that there was a time when boys were a benefit to a family but that children are now merely a drain on a family's resources.