Through Two Doors at Once

Book excerpt: The clearest, most accessible explanation yet of the amazing world of quantum mechanics. How can matter behave both like a particle and a wave? Does a particle exist before we look at it or does the very act of looking bring it into reality? Are there hidden elements to reality missing from the orthodox view of quantum physics? And is there a place where the quantum world ends and our perceivable world begins? Many of science's greatest minds have grappled with these questions embodied by the simple yet elusive "double-slit" 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 theories. Nearly a century later, Albert Einstein showed that light comes in particles, and the experiment became key to a fierce debate with Niels Bohr over the nature of reality. Richard Feynman held that the double slit embodies the central mystery of the quantum world. Hypothesis after hypothesis, scientists have returned to this ingenious experiment to help them answer the deep questions about the fabric of our universe. With his extraordinary gift for making the complicated comprehensible, Anil Ananthaswamy travels around the world and through history, down to the smallest scales of physical reality we have yet fathomed for the answers. ***PRAISE FOR THROUGH TWO DOORS AT ONCE*** A Physics Book of the Year A Forbes Best Book of the Year A Kirkus Best Book of the Year A Smithsonian Favourite Book of the Year Publisher's Weekly Best Books of Autumn 'A fascinating read and a must for anyone who would like to find out the latest experimental advances made in this most fundamental of quantum experiments.' Physics World 'Ananthaswamy cleverly comes at quantum physics from a different direction... An excellent addition to the 'Quantum physics for the rest of us' shelf.' Brian Clegg, author of Are Numbers Real? and The Quantum Age 'A challenging and rewarding survey of how scientists are grappling with nature’s deepest, strangest secrets.' Wall Street Journal 'A fascinating tour through the cutting-edge physics the experiment keeps on spawning.' Scientific American 'Ananthaswamy gives an absolutely mind-boggling tour of how quantum physicists try to explain this “reality” that one of the most powerful scientific models of our era.' Smithsonian 'Offers beginners the tools they need to seriously engage with the philosophical questions that likely drew them to quantum mechanics.' Science 'At a time when popular physics writing so valorizes theory, a quietly welcome strength of Ananthaswamy’s book is how much human construction comes into focus here. This is not “nature” showing us, but us pressing “nature” for answers to our increasingly obsessional questions.' Washington Post 'Ananthaswamy's book is simply an outstanding exploration of the double slit experiment and what makes it so weird.' Forbes 'A thrilling survey of the most famous, enduring, and enigmatic experiment in the history of science.' Kirkus, starred review