Albert Einstein knew already in the early 1900s, when he first published his famous paper about the constancy of the speed of light, that not only did this constancy imply that mass contains energy (E = m c squared), but that faster-than-light motion could lead to paradoxes -- some that seemed to involve backwards time travel.What are these paradoxes? Why is light and its speed relevant? This book will lead you through an obstacle course of conundrums and oddities, building up your understanding of how light's speed creates simple but mind-expanding paradoxes -- one conceptual riddle at a time.This is not your average popular science book. This is also not a textbook. This book takes one theme -- the universally constant speed of light -- and shows how it may appear compromised on scales from the quantum mechanics of the very small to the cosmology of the very large, and the resulting surprising implications can result.