Lessons in reality from particles that don't exist

WHEN you hear the word “particle”, what image floats into your mind? Chances are you’re thinking small, and then some – like the tiniest billiard ball imaginable. Indivisible chunks of matter pinging off each other in the vast expanses of space, or jostling for position in a crowded chunk of stuff.

Chances are, too, you’re nowhere near the vision of particles painted by our best picture of how they work, quantum theory. This says that despite making up stuff that definitely has a size – ourselves, the paper or screen you’re reading this on – particles occupy a point in space…