How is faster-than-light related to back-in-time?  Contemplate simply stated paradoxes in this popular-level, nearly math-free book by Robert J. Nemiroff -- a Professor of Physics and Fellow of the American Physical Society. 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. "You've probably already encountered Robert Nemiroff's work, even if you don't know it. As one of the masterminds behind NASA's enduringly popular Astronomy Picture of the Day website, Nemiroff has spent more than two decades penning sparkling descriptions of celestial wonders for an audience of millions worldwide. In this book, he's bringing his encyclopedic expertise and contagious enthusiasm to the fascinating topic of superluminal phenomena—that is, the surprisingly extensive pantheon of things that manifest at timescales exceeding the speed of light. Faster than Light is a one-of-a-kind romp through the everyday familiarities and wild frontiers of photonic physics—and, just as importantly, a whole lot of fun." -- Lee Billings, Senior Editor, Space & Physics, Scientific American " 5 out of 5 The thought-provoking science book Faster than Light unpacks the conceptual riddles surrounding the speed of light with winsome humor. Robert J. Nemiroff's enlightening popular science book Faster than Light probes the mind-bending implications of a universal constant. Albert Einstein's theory of the constant speed of light, Nemiroff says, can result in paradoxes, on both a quantum mechanics level and a cosmological scale. To address these, his book breaks down advanced scientific concepts in straightforward, direct terms, using specialized nomenclature in a sparing and accessible way. Across broad topical sections covering Earth, the universe, and relativity and communications, the chapters focus on subjects including superluminal history, improving light bulbs, and increasing the speed of laser spots. Each is detailed in covering both historical experiments and advanced ideas well, moving through dense concepts with systematic awareness and sharing digestible analogies to aid understanding, as when photon wave packets are compared to a locomotive-led train. Aimed at the general public, the book focuses on ideas rather than particular math and data. Its scenarios are abstract but relatable." -- Clarion Reviews " Starred Review Imagine embarking on a journey to comprehend the physics of the entire universe with a guide who's not only an expert but makes the concepts digestible and entertaining. Robert J. Nemiroff offers such a journey in Faster Than Light, a book that initially describes the speed of light, then touches on subjects as esoteric as time travel using the theory of relativity and speculation on how to send information back in time, among other subjects. In his prologue, Nemiroff explains his goals and encourages readers to attack the book in their own comfort zone, either by reading straight through or by jumping around (what he calls the "butterfly method"). While each section stands on its own, readers can easily look back for more information on concepts introduced along the way. For example, readers can enjoy the chapters on superluminal tricks and illusions without first understanding the definition of superluminal, then look back to the chapter defining the term. Journeying with Nemiroff feels like sitting in a classroom with one's favorite instructor who uses accessible anecdotes to illustrate challenging concepts and sometimes provides simplistic drawings to prove a point. His strongest teaching method is to pose a multiple-choice question with three plausible answers and a fourth that's clearly in jest, allowing readers to appreciate his wit. The author's presentation is based on solid physics concepts. His bona fides include work in astrophysics at NASA as well as ongoing pursuits in astronomy and astrophysics. He also acknowledges associations with other modern physics intellectuals, such as Christina Thone and Qi Zhong. Nemiroff 's helpful glossary and solid index round out the book. While Faster Than Light isn't geared to