Through Two Doors at Once: The Elegant Experiment That Captures the Enigma of Our Quantum Reality

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The “double-slit” experiment has flummoxed scientists for 200 years. With concise, compelling prose that makes this complex, bizarre subject not only fathomable but downright fascinating, Anil Ananthaswamy explores the who, what, why, and how of one of the weirdest, most mysterious experiments in the history of science. Recommended By Gigi L., Powells.com

The intellectual adventure story of the "double-slit" experiment, showing how a sunbeam split into two paths first challenged our understanding of light and then the nature of reality itself — and continues to almost 200 years later.

Many of the greatest scientific minds have grappled with this experiment. Thomas Young devised it in the early 1800s to show that light behaves like a wave, and in doing so opposed Isaac Newton's view that light is made of particles. But then Albert Einstein showed that light comes in quanta, or particles. Quantum mechanics was born. This led to a fierce debate between Einstein and Niels Bohr over the nature of reality — subatomic bits of matter and its interaction with light — again as revealed by the double-slit experiment. Richard Feynman held that it embodies the central mystery of the quantum world. Decade after decade, hypothesis after hypothesis, scientists have returned to this ingenious experiment to help them answer deeper and deeper questions about the fabric of the universe.

How can a single particle behave both like a particle and a wave? Does a particle, or indeed reality, exist before we look at it, or does looking create reality, as the textbook "Copenhagen interpretation" of quantum mechanics seems to suggest? How can particles influence each other faster than the speed of light? Is there a place where the quantum world ends and the familiar classical world of our daily lives begins, and if so, can we find it? And if there's no such place, then does the universe split into two each time a particle goes through the double-slit?

Through Two Doors at Once celebrates the elegant simplicity of an iconic experiment and its profound reach. With his extraordinarily gifted eloquence, Anil Ananthaswamy travels around the world, through history and down to the smallest scales of physical reality we have yet fathomed. It is the most fantastic voyage you can take.

“Quantum mechanics asks us to believe a number of bizarre things about the nature of reality. But these demands don’t arise out of thin air; they are forced on us by experiments. Anil Ananthaswamy has provided a lively introduction to the most paradigmatic of these: the (in)famous double-slit experiment.” Sean Carroll, author of The Big Picture

“Upon opening his two quantum doors, Anil Ananthaswamy invites us into the bizarre and wacky world of nature on the smallest of scales. An engaging raconteur, he tells us a story that is confounding, disturbing, and yet eminently fascinating. Ananthaswamy serves as the perfect tour guide to physics’ wild side by closely examining one of its most famous experiments.” Marcia Bartusiak, award-winning author of Einstein’s Unfinished Symphony and Dispatches from Planet 3

“Wondrous book. If I were boarding the Trans-Siberian Railway in Moscow, Anil Ananthaswamy is the companion I’d want in the Lounge car. I would buy him a very good Scotch, say ‘Tell me about quantum physics and the scientists who created it,’ and then I’d sit back contentedly for the seven days to Vladivostok, and listen.” David Quammen, award-winning author of The Song of the Dodo and (forthcoming) The Tangled Tree

“Following up 2015’s acclaimed The Man Who Wasn’t There, Ananthaswamy treats a 19th-century light experiment as a sprawling intellectual adventure story….This accessible, illuminating book shows that no matter how sophisticated the lab setup, the double-slit experiment still challenges physicists.” Publisher’s Weekly, Top 10 Science Books for Fall 2018

“A fascinating tour through the cutting-edge physics the experiment keeps on spawning.” Scientific American

“A thrilling survey of the most famous, enduring, and enigmatic experiment in the history of science.” Kirkus (Starred Review)

“Through Two Doors at Once is a challenging and rewarding survey of how scientists…are grappling with nature’s deepest, strangest secrets.” Wall Street Journal

Anil Ananthaswamy is an award-winning journalist and former staff writer and deputy news editor for the London-based New Scientist magazine. He has been a guest editor for the science writing program at the University of California, Santa Cruz, and organizes and teaches an annual science journalism workshop at the National Centre for Biological Sciences in Bengaluru, India. He is a freelance feature editor for the Proceedings of the National Academy of Science’s Front Matter. He contributes regularly to the New Scientist, and has also written for Nature, National Geographic News, Discover, Nautilus, Matter, The Wall Street Journal and the UK’s Literary Review. His first book, The Edge of Physics, was voted book of the year in 2010 by Physics World, and his second book, The Man Who Wasn’t There, won a Nautilus Book Award in 2015 and was long-listed for the 2016 Pen/E. O. Wilson Literary Science Writing Award.