Tropical cyclones are strongly-rotating convective vortices that cause substantial damage to life and society around the world annually. This talk will discuss how we can use models of both real and imagined worlds to understand the behavior of tropical cyclones in the atmosphere of our planet. In particular, we combine model simulation experiments with theory and observations to develop new understanding of the size of tropical cyclones on Earth, and how size may change in the future. The implications for future damage risk will also be discussed.