Ryan Wills; adboestock/Getty images
As one of the original architects of quantum theory, perhaps our most successful scientific idea, you would think that Niels Bohr would have been interested in the nature of reality. The subjects of his studies were atoms, electrons, photons – the things we think of as the fundamental ingredients of the universe.
But for Bohr, reality was actually none of his business. “It is wrong to think that the task of physics is to find out how nature is,” he said in an often-repeated quote from the early days of quantum theory. “Physics concerns what we can say about nature.”
Though this distinction may sound pedantic, it can’t be dismissed when it comes to quantum physics. The picture this theory paints of the subatomic world is perplexing: particles can seemingly exist in two places at once, time stands still and there is no such thing as empty space. Can that really be what reality is like?

Some physicists shrug off the question. Like Bohr, they aren’t talking about reality at all, only our pale perception of it. But many find this viewpoint deeply unsatisfying and want to believe in a world composed of sensible objects that exist independently of what we know about them. They are, in other words, realists. One of them is Robert Spekkens at the Perimeter Institute in Canada, who has a plan…