Science as Metaphor

At the leading edge of experience in philosophy, science and feeling there is inevitably a groping for language to translate the insecure novelty of noticing and understanding into a precision of meaning and imagery.

— Frank Oppenheimer

Oppenheimer wrote these words in the introduction to a series of readings at The Exploratorium on "The Language of Poetry and Science." Poetry and science? Not so strange when you consider that Niels Bohr himself once wrote, "When it comes to atoms, language can be used only as in poetry. The poet, too, is not nearly so concerned with describing facts as with creating images."

Science, after all, involves looking mostly at things we can never see. Not only quarks and quasars but also light "waves" and charged "particles"; magnetic "fields" and gravitational "forces"; quantum "jumps" and electron "orbits." In fact, none of these phenomena is literally what we say it is. Light waves do not undulate through empty space in the same way as water waves ripple over a still pond; a field is not like a hay meadow, but rather a mathematical description of the strength and direction of a force; an atom does not literally leap from one quantum state to another; and electrons do not really travel around the atomic nucleus in circles any more than love produces literal heartaches. The words we use are metaphors, models fashioned from familiar ingredients and nurtured with imagination. "When a physicist says 'an electron is like a particle,'" writes physics professor Douglas Giancoli "he is making a metaphorical comparison, like the poet who says, 'love is like a rose.' In both images a concrete object, a rose or a particle, is used to illuminate an abstract idea, love or electron."

Over the centuries the metaphors of science have taken a multitude of forms. Recently, physicists struggling to understand new evidence for a repulsive force in the universe could be heard tossing around terms like "quintessence," "X matter," "smooth stuff," and "funny energy." The more mysterious the emerging landscape, the further they must reach for appropriate imagery to describe it. But there's nothing necessarily odder about this language than the terms scientists have always used to pin down the ineffable.

Here's Francis Bacon's seventeenth-century description of heat: "Heat is a motion of expansion, not uniformly of the whole body together, but in the smaller parts of it, and at the same time checked, repelled, and beaten back, so that the body acquires a motion alternative, perpetually quivering, striving, and irritated by repercussion, whence spring the fury of fire and heat."

And Isaac Newton's account of what we now call chemical reactions: "And now we might add something concerning a most subtle spirit which pervades and lies hid in all gross bodies, by the force and action of which spirit the particles of bodies attract one another at near distances and cohere, if contiguous ... and there may be others which reach to so small distances as hitherto escape observations ... and electric bodies operate to greater distances, as well repelling as attracting the neighboring corpuscles; and light is emitted, reflected, refracted, inflected, and heats bodies; and all sensation is excited and ... propagated along the solid filaments of the nerves."

And Hans Christian Oersteds early-nineteenth-century image of electricity: "The electric conflict acts only on the magnetic particles of matter. All nonmagnetic bodies appear penetrable by the electric conflict, while magnetic bodies, or rather their magnetic particles, resist the passage of this conflict. Hence they can be moved by the impetus of the contending powers."

Compare those with excerpts from a paper proposing a new kind of "dark matter," by physicists Daniel Chung, Edward Kolb, and Antonio Riotto: "The goal of this paper is to show that the Universe might be made of superheavy WIMPs (we will refer to them as X particles), with mass larger than the weak scale by several (perhaps many) orders of magnitude. ... To see the effects of vacuum choice and the scale factor differentiability on the large X mass behavior of the X density produced, we start by canonically quantizing an action of the form (in the coordinate ds = dt - a(t)dx) ..."

The subjects of science are not only often unseeable; they are also untouchable, unmeasurable, and sometimes even unimaginable. The only way to examine these elusive entities is to scale them up, or shrink them down, or give them a familiar, solid form so that we might finally get at least a temporary handle on them. But even in 1882, physicist and lawyer Johann B. Stallo recognized that the current models of the universe were only "logical fictions," useful tools for understanding but in the end only "symbolic representations" of the real world.

When it comes to science — like so many other things — we find ourselves literally at a loss for words. Thus are metaphors born. When botanist Robert Brown first noticed the quick random motion of plant spores floating in water (now known as Brownian motion), he described it as a kind of "tarantella," according to physicist George Gamow, who went on to anthropomorphize it as "jittery behavior." (Brownian motion was the first convincing evidence for the existence of molecules, since it was bombardment by water molecules that made the plant spores dance.)

Later, Gamow described X rays as a mixture of many different wavelengths of invisible light. "Being suddenly stopped in their tracks [by a target], the electrons spit out their kinetic energy in the form of very short electromagnetic waves, similar to sound waves resulting from the impact of bullets against an armor plate." Thus in German they are called Bremsstrahlung, or "brake radiation."

Sometimes the metaphors get confused. A mixture of many colors is called white, but we also call a mixture of sounds "white" noise; we speak of "loud" colors. Something that is "going to seed" is deteriorating, yet "seedy" really means "fertile," since seeds are the origin of new growth. The universe is described alternately as a bubble, a void, or a firecracker. Time is "fluid," or "grainy," or both. Electrons are waves, and light waves are particles. If it all sounds as if the scientists don't know what they're talking about, it is at least in part because a lot gets lost in translation.

Imagining the unseeable is hard, because imagining means having an image in your mind. And how can you have a mental image of something you have never seen? Like perception itself, the models of science are embedded inextricably in the current worldview we call culture. Imagine (if you can) what the planetary model of the atom would have looked like, its satellite electrons orbiting its sunlike nucleus, if people had still thought the earth was flat. It would have been literally unthinkable. "A model or picture will only be...