This book introduces the fascinating subject of hydrodynamics and critical convection in a rotating layer--a model that helps us understand the behavior of the Earth's fluid core and similar regions deep inside many planets and their large moons. It explores how heat and mass are transferred within the simplest possible model of a planet's fluid core, with special attention to asymptotic methods that reveal the underlying physical mechanisms.
All chapters include exercises designed for self-study and for testing the reader's understanding of the material. These have also been used as part of classroom instruction and independent assessments. The book is well-suited for graduate-level researchers and advanced students working in planetary, solar, or stellar physics, as well as computational fluid dynamics and applied mathematics.