Spindizzy

Spindizzies, or tether cars, come in three categories of descending value: original as raced, restored and reproduced. […] The best indicator of a spindizzy’s authenticity is its size, said Eric Zausner of Berkeley, Calif., who has an extensive collection. “Repros are always smaller because they come from second-generation molds.”

So the twin scientific themes of the first book are the development of antigravity technology called spindizzies that enable whole cities to lift into space, and the production of "anti-agathic" drugs that can extend life indefinitely, necessary for the immense journey times in interstellar space.