Two particles behave identically and instantaneously though separated by great space and with no force passing between them. How? Award-winning Scientific American contributing editor Musser (The Complete Idiot’s Guide to String Theory, 2008) probes the riddle.
Locality was the bedrock of physics for centuries. “It means that everything has a place. You can always point to an object and say, ‘Here it is.’ If you can’t, that thing must really not exist,” writes the author in this anything-but-simple story of nonlocality. Einstein understood locality as both separability—things in separate places have independent existences—and local action: objects interact by striking one another or intermediarily. Musser covers the evolution of physics’ method of physical inquiry, “driven by the conviction that the universe is within the human power to understand,” with comprehensible rules and a history of systematic investigation for reference: from Zeno and Democritus to Newton, who turned inquiry—and locality—on its head. Newton couldn’t explain gravity, but his equations proved out. Now, writes Musser, “modern physicists think of any theory as having two separate functions. First, the theory should provide a mathematical description....Second, the theory should provide an ‘interpretation’ of the formulas: a compelling picture of what’s going on….” But the second part is flexible enough that physicists can “kick away the interpretation and let the equations stand on their own.” Much the same can be said about the entire quantum revolution and certainly nonlocality: locality may be a precondition for relativity, but there are enough instances of flabbergasting nonlocality to suggest that space is simply a convenient notion to describe order. With brio and dash, Musser navigates the difficult science and also introduces interesting characters such as Michael Heller, “a physicist, philosopher, and priest” at Krakow’s Pontifical Academy of Theology, and theorist Nima Arkani-Hamed, winner of the 2012 Fundamental Physics Prize.
An endlessly surprising foray into the current mother of physics’ many knotty mysteries, the solving of which may unveil the weirdness of quantum particles, black holes, and the essential unity of nature.