The atom is like a solar system, with electrons whirling around the nucleus like planets orbiting a star. No, actually, it isn’t. But as a first approximation to help us visualize something that is so invisible, that image works as a metaphor.

Science traffics in metaphors because our brains evolved to grasp intuitively a world far simpler than the counterintuitive world that science has only recently revealed. The functional activity of the brain, for example, is nearly as invisible to us as the atom, and so we employ metaphors. Over the centuries the brain has been compared to a hydraulic ma­chine (18th century), a mechanical calculator (19th century) and an electronic computer (20th century). Today a popular metaphor is that the brain is like a Swiss Army knife, with specialized modules for vision, language, facial recognition, cheating detection, risk taking, spi­rit­uality and even God.