What Is Relativity?: An Intuitive Introduction to Einstein’s Ideas, and Why They Matter

“Black holes don’t suck,” says astrophysicist Bennett (Life in the Universe); in fact, their exotic nature is the perfect way to explore relativity. The special theory of relativity, proposed by Albert Einstein in his 1905 paper, “On the Electrodynamics of Moving Bodies,” says in part that nothing can outrace light, but it’s exactly in that highly accelerated realm where you need to be to observe the extreme weirdness of relativity at work: time dilation, mass increasing, and the shortening of the length of high-velocity objects. Bennett shows how particle accelerators can provide that environment on Earth, making special relativity “one of the most well-tested theories in all of science”—but still incomplete, as far as Einstein was concerned. He sought “an underlying simplicity in the universe”—wherein gravity and acceleration are the same—and he found that in the curved spacetime of general relativity where orbiting objects move “like marbles in a salad bowl,” following the curvature of spacetime along the straightest possible path. From black holes and gravity waves, to wormholes and warp drive, Bennett’s fun book shows readers what relativity means, and what it reveals about our universe. (Mar.)