Beyond Weird: Why Everything You Thought You Knew about Quantum Physics Is Different

by Philip Ball

This possibility seemed to Einstein to be a profoundly anti-scientific idea, because it meant relinquishing not just a complete description of reality but the notion of causality itself. Things happen, and we can say how likely they are to happen, but we cannot say why they happened just as or when they did. Take radioactive decay. Some radioactive atoms will decay by emitting an electron from inside the nucleus: this electron is, for historical reasons, called a beta particle, but it’s just a common-or-garden electron. Atomic nuclei don’t exactly contain electrons – we saw that these orbit outside the nucleus. But they do contain particles called neutrons, which may spontaneously decay into an electron, which gets spat out, and a proton, which stays in the nucleus.*1 Beta decay of carbon-14, one of the natural forms of carbon atoms, is the process used for radiocarbon dating, and it transforms the carbon atom to a nitrogen atom. Beta decay is a quantum process, so the probability of the neutron decaying is described by a wavefunction. (It’s actually a kind of quantum tunnelling process: the electron tunnels out of the nucleus, where it would otherwise be bound by electrical attraction.) All the wavefunction can tell you is the probability that the decay will occur – not when that will happen. Take any specific atom of carbon-14, and its decay could happen tomorrow, or in 1,000 years. And there’s nothing, nothing, you can do to figure out which it will be, for all the carb...