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Science File | Mind Over Matter

What You See Depends on How You Look at It


A woman I know was told by three different doctors that the large irregular blob on her mammogram was serious cause for concern. From the looks of it, all three said, it appeared to be a malignant tumor.

But as any scientist can tell you, "from the looks of it" is a phrase that's fraught with peril. Happily, a fourth doctor--more experienced in reading mammograms--decided to take some more pictures from different angles, and lo and behold, the tumor was only an illusion.

The art of seeing comes up in physics and astronomy all the time. Yesterday's newfound planet is revealed as a wiggle in the instrument that took its picture; that newly discovered subatomic particle turns out to be a stray piece of background noise.

It happens the other way, too--when the background noise turns out to be a new particle, or the wiggle that was dismissed as an aberration turns out to be a planet.

Scientists, like doctors, spend most of their time studying things they can never directly see. This means they have to become experts in the art of seeing the obscure, and sometimes the invisible.

Take dark matter--the unseeable stuff that supposedly makes up 90% of the universe. To catch it in the act of holding the universe together, experimenters must devise all manner of clever traps--except they don't know what kind of bait to use because they can't agree on what they're looking for.

Or take the Earth, which is right under our noses. The most interesting slice of it may well be three days' drive straight down--where the outer core meets the molten mantel. And there's no way to get there from here.

Instead, geophysicists, like doctors, look for signs on the surface that tell tales of hidden goings-on underneath--say, scars on the planet that tell of ancient upheavals. Or they resort to reading images created by sound waves reflected from structures inside the Earth. These sonograms are similar to the ones physicians use to see inside the human body. An obstetrician getting a look at a developing baby bounces sound waves off the fetus to get an image; a geophysicist rattles the ground with explosions to set off sonic booms inside the Earth. Astronomers even use sonograms to study the sun and stars, by watching the way they ring like bells under the influence of internal vibrations.

When just looking isn't enough, geologists may resort to a version of surgery--cutting holes in the planet's skin to bring up samples to be studied in the lab. Or they try to re-create events they can't see--like growing cells in a petri dish, or squishing materials together under enormous pressure to simulate, say, the inside of the giant planet Jupiter.

Paleontologists must find ways to peer into the past, re-creating the detailed physiology and family habits of dinosaurs from a few fossilized footprints, a jawbone and some dusty DNA. Climatologists must look both backward and forward in time, using powerful computers to turn eons into seconds, then rewind, throw in some new theories, and try again.

And there are other, less obvious, tools--models, for example, that allow scientists to imagine things they can't see. Chemists have come up with myriad ways of describing the invisible molecules that are the tools of their trade.

Cornell's Roald Hoffmann likes to show the same molecule as a chemical formula, a drawing, a ball and stick, a computer simulation.

Which does a molecule really look like? he asks. Although all four ways describe it accurately, it looks like none of them.

Some scientists must follow clues that seem far removed from their subject--looking for the origin of human life in the dust grains exhaled by passing comets, for example. Others fiddle with equations to look for patterns that reveal unseen forces. Still others use statistics and clever mathematics to tease out needles from haystacks, or tell whether the smudge in the telescope is a star or galaxy.

And nothing trains a seer like a lifetime of looking. Astronomer Vera Rubin studied a galaxy that had been seen and overlooked by many astronomers before, and saw the first-ever case of stars rotating in opposite directions. She did it by taking two years to "make friends" with this unusual cluster of stars.

My personal favorite is the story of antimatter. A theorist discovered it as a minus sign in an equation; an experimentalist saw it as a cosmic ray track that curved the wrong way. What's remarkable is that neither gave in to the temptation to dismiss such an unexpected discovery as a mere aberration, or noise.

Today, of course, antimatter is used routinely by doctors to see inside the human body (in the form of PET scans, or positron emission tomography.)

When all is said and done, being a good looker may be the most important quality a scientist--or a doctor--can possess.

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