“… the history of physics is littered with metaphorical leaps. Einstein grasped relativity while thinking about moving trains. Arthur Eddington compared the expansion of the universe to an inflated balloon. James Clerk Maxwell thought of magnetic fields as little whirlpools in space, which he called vortices. The Big Bang was just a cosmic firecracker. Schrödinger’s cat, trapped in a cosmic purgatory, helped illustrate the paradoxes of quantum mechanics. It’s hard to imagine string theory without its garden hose.
These scientific similes might seem like quaint oversimplifications, but they actually perform a much more profound function. As the physicist and novelist Alan Lightman writes, “Metaphor in science serves not just as a pedagogical device, but also as an aid to scientific discovery. In doing science, even though words and equations are used with the intention of having precise meaning, it is almost impossible not to reason by physical analogy, not to form mental pictures, not to imagine balls bouncing and pendulums swinging.” The power of a metaphor is that it allows scientists imagine the abstract concept in concrete terms, so that they can grasp the implications of their mathematical equations. The world of our ideas is framed by the only world we know.
But relying on metaphor can also be dangerous, since every metaphor is necessarily imperfect. (As Thomas Pynchon put it, “The act of metaphor is a thrust at truth and a lie, depending on where you are.”) The strings of the universe might be like a garden hose, but they are not a garden hose. The cosmos isn’t a plastic balloon. When we chain our theories to ordinary language, we are trespassing on the purity of the equation. To think in terms of analogies is to walk a tightrope of accuracy.
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