Hovering above the ghoulish terrain, a visitor might feel transported to a distant planet. Rendered in black and white, the lay of the land would seem familiar: Clusters of low, rounded foothills give way to higher, rougher ones, finally converging on majestic snowcapped peaks. But the colors are wrong. The alpine forests are chartreuse. The glaciers and snowfields are yellow at the bottom, orange in the middle, red at the top. Elsewhere, a single peak, ascending through shades of bright yellow, fluorescent green and icy blue, juts above the crimson badlands like an obscene Matterhorn.
Confronted with these images, which appeared in the journal Science in September, one might think they were digital photographs sent from a Viking or a Voyager, an exercise in extraterrestrial cartography.
But the territory exists only in abstraction, as arrangements of data in experiments that have nothing to do with outer space. One involves genetics, the other quantum physics. In each, scientists try to get a better feel for their data by imagining it as a mathematical mountain range -- one of science's dominant metaphors.
Explaining the strange in terms of the familiar, that is the essence of the scientific quest. In every field from molecular biology to cosmology, data are sorted and analyzed mathematically. But the gray nwmbers are often translated into colorful three-dimensional pictures, the language human brains comprehend best. Using metaphor and analogy, the tools of artists and poets, abstract patterns take on subtance and become lodged more firmly in the mind.
For many people, a "mountain of data" evokes a heaping pile of unorganized information. But in science, the phrase can mean data arranged with exquisite precision. Following a trend in the numbers becomes an ascent along a ridgeline leading to a rocky precipice and a stunning view of an expansive valley.
The first landscape, what scientists call a gene expression map, depicts the functioning of the genome of the worm C. elegans. Understanding how its DNA operates can lead to insights about the human genome, a biochemical structure commonly thought of as a map, a blueprint, an enciphered text or, more recently, as cellular software, an operating system.
Adopting instead the montane metaphor, scientists at the Stanford University School of Medicine displayed data from 553 experiments by 30 labs into an image they hoped would give an intuitive feel for how the worm's 19,000-plus genes interact.
Each of the 44 mountains- represents a group of genes that, though scattered throughout the worm's genome, become active under the same conditions, producing proteins that various cells need to conduct their affairs. (The significance of 14 remains unknown, terra incognita.) The higher the mountain, the more genes it represents, ranging from the towering Mount Zero, 2,703 genes high, down to Mount 43, a hillock of five genes. As on a relief map, the arbitrary colors help the eye get a quick fix on the topography.
The second image, from a cover of Science in 1995, represents not genes but molecules of a substance called rubidium used in research that won this year's Nobel Prizein Physics. Here the altitude of the mountain indicates how fast the molecules are moving, with speed decreasing as the eye ascends into the chilly heights. The colors represent the number of atoms movmg at each velocity, red being the fewest and white the most,
At the peak, most of the atoms are frozen near absolute zero, converging into a single superatom called a Bose-Einstein condensate. In this exotic substance, the rules of quantum mechanics allow thousands of atoms to crowd into the same place at the same time -- resulting in a new state of matter.
Like pictures in National Geographic, the most arresting scientific images inspire feelings of wanderlust, a desire to lose oneself in a far-off land. A depiction of the data showing how high-speed laser pulses were used to manipulate the spins of electrons in a substance called cadmium selenide becomes an eerily symmetrical iceberg, casting its lonely reflection in a frigid, impossibly still pond. The research by physicists at the University of California at Santa Barbara and Penn University, earned the cover spot of the June 29 issue of Science.
High-speed computers and "data mining" software are producing increasingly refined visualizations. But the practice of bringing substance to abstractions with pictures and analogies is as old as science itself.
An individual electron is an evanescent entity, acting something like a particle and something like a wave. Really it is neither, hovering in a metaphorical territory in between. But when electrons move en masse as electricity through a wire, they can be pictured as a liquid. Current, or amperage, becomes equivalent to the rate of flow, and voltage to the pressure in the pipes."
The metaphor has its limits. Cut a wire and you won't get wet, any more than you'll freeze on top of Gene Mountain. But analogy helps the mind get a more visceral grip.
The procedure used to make thousands of atoms sit still long enough to merge into a Bose-Einstein condensate can be precisely described with mathematics. But it is more evocative, with a bit of poetic license, to call it "optical cooling." Heat is defined, after all, as the random movement of atoms. So ambush each atom, hitting it from every direction with photon guns shooting tiny projectiles of light -- striking it this way and that way until it is almost stationary. The resulting glob of slow-motion matter is called optical molasses.
Metaphors are always inexact; in the quantum realm they are stretched to the breaking point. Physicists talk about a subatomic particle's "spin." Like a top, a particle can rotate clockwise or counterclockwise. But take the analogy too far and it crumbles. An ordinary top can revolve faster or slower across a smooth range of speeds. Particles, being quantum in nature, can spin only at certain fixed velocities, preset by nature. And they can spin in various combinations -- 43 percent clockwise and 57 percent counterclockwise, for example -- at the same time.
Space itself has become a metaphor. Think of cyberspace, which can be explored but not measured, or the "desktop" of your personal computer, a simulated expanse across which you "drag" folders and icons. The motion is illusory. All your mouse strokes are really doing is rapidly switching pixels on and off.
You can construct your own "restaurant space" describing dining in your neighborhood. Categorize them according to three parameters -- price, quality and years in business -- and plot the information on a three-dimensional graph. Each restaurant becomes a point in an abstract space in which nearness is a measure of similarity. Two adjacent establishments might be in reality blocks apart.
There is no need to stop with three dimensions. Imagine another axis measuring the number of tables and another measuring the variety of wines in the cellar. Now you have a five-dimensional "hyperspace," impossible to really picture but something scientists use all the time.
It is not always clear whether a space is real or artificial. Superstring theory holds that the particles making up matter and energy are secondary manifestations -- epiphenomena -- generated by tiny objects called strings and branes vibrating in 10 dimensions. The theory is enormously successful on paper, but a question, perhaps unanswerable, lingers: Are these extra dimensions physical or mental, like restaurant space?
Sometimes metaphors are outgrown. The biggest break in the Human Genome Project came half a century ago, when scientists realized that DNA could be thought of as a text, the chemical letters spelling out instructions for making and operating cells. But as experiments reveal that genes switch each other on and off, it begins to seem like a text that can read and edit itself -- more like a computer. But is DNA software or hardware? As with wave/particle duality, neither metaphor exactly fits.
As the discoveries of science become part of popular culture, the metaphorical flow sometimes goes the other way. Novelists look to science for linguistic lenses to cast the familiar in a new light. The patterns of circuitry on a computer chip are commonly compared with the layout of a modern city. In "The Crying of Lot 49," Thomas Pinchon turned the tables, comparing a sterile, overly planned Southern California community (called San Narciso) to a computer chip. In his best-known novel, the parabolic arc of a missile is memorably called "Gravity's Rainbow, a metaphor that seems especially apt if you remember some college calculus.
In Jonathan Franzen's new novel, "The Corrections," Arthur Lambert, a retired engineer, sits in his basement gloomily testing Christmas lights, only to discover in the depths of the tangle a blacked-out string of bulbs. A "substantia nigra," Franzen calls it.
The metaphor is pitch-perfect. The substantia nigra ("black substance") is a region deep in the brain that produces the neurotransmitter dopamine. But the analogy cuts deeper. A burned-out substantia nigra is a symptom of Parkinsonism, the disease that afflicts Arthur. He is no more able to repair the lights than his doctors are able to fix his brain.
And here is how the novel describes the neurotic dependence Arthur's son Chip has on his sister, because of all the money he owes her: "He'd lived with the affliction of this debt until it had assumed the character of a neuroblastoma so intricately implicated in his cerebral architecture that he doubted he could survive its removal."
By daring to use such allusions, Franzen compliments his readers: Novels like his are a reminder that in literature, as well as science, illuminating the intangible with a good metaphor is a powerful art.
