Investigations
The discovery of discovery, or our debt to Copernicus
>>The discovery-and the gradual acceptance of-a heliocentric universe says a lot about how a society embraces big ideas.

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Howard Margolis has made a bold move. Not only has the public-policy professor stepped away from his discipline by writing a book about science, but he's also departed entirely from the prevailing stance among science historians: that the Scientific Revolution didn't exist.

"This [view] reminds me of a story of the Old West about a cowboy wandering over the plateau of northern Arizona," writes Margolis in It Started with Copernicus: How Turning the World Inside Out Led to the Scientific Revolution, due out this April from McGraw-Hill. "Innocently he rides right up to the rim of the Grand Canyon. The cowboy sits a long time contemplating the vast gorge. Eventually he mutters, 'Something happened here.'"

Something also happened in Europe around 1600, Margolis says, effecting a permanent change in the course of scientific discovery-and creating a cognitive gorge worthy of being called a revolution. Cognitive is the key term, because what changed, says Margolis, was how scientists thought about their work. Following Copernicus's lead, in the early 17th century researchers began an entirely new form of inquiry. The problem is, he says, science historians take the gorge so much for granted that it's become invisible.

A barrel-chested man whose fine white hair obeys the whims of the static electricity sparked by his cyclist's helmet, Margolis loves problems that involve entrenched and shifting social knowledge. In his peripatetic career he has been a defense correspondent for the Washington Post, a speech writer for the secretary of defense, and a fellow at MIT, where he "stuck around long enough they just gave me a Ph.D." He has written five books, including Dealing with Risk: Why the Public and the Experts Disagree on Environmental Issues (Chicago, 1996).

In It Started with Copernicus, Margolis recreates the Scientific Revolution's cognitive canyon by sketching out the events and people on both sides. By the epilogue, he's speculating on lessons for public policy-and suddenly it seems he hasn't strayed so far from disciplinary confines.

Margolis's tale begins with a rather awkward character straddling the canyon. In 1588 the Danish astronomer Tycho Brahe offered a compromise between two conflicting systems of the "world": Ptolemy's geocentric and Copernicus's heliocentric theory. (The idea of a "universe" hadn't yet been introduced.) Tycho allowed the traditional planets to orbit the Sun but kept the Sun, carrying the planets' orbits, orbiting the Earth. In Tycho's sketch, the orbits of the Sun and Mars seem to intersect-a problem he solved by doing away with Ptolemy's solid spheres, citing for evidence his recent observations of a comet whose path through the heavens proved solid spheres couldn't exist. The compromise was, for some time, the only theory a God- (and pope-) fearing Catholic-scientist or otherwise-could in good faith embrace. In the 20th century, the MIT philosopher and historian of science Thomas Kuhn termed Tycho's elimination of the solid spheres a paradigm shift.

What's interesting is that Tycho's impetus to discount the spheres-the colliding orbits of the Sun and Mars-is in fact an optical illusion. In an April 1998 Nature article Margolis became the first known person to point out the illusion. (There, he explains how to see it, which for most people requires taking scissors to Tycho's sketch and manually making the apparatus rotate, which it does, spheres intact.) For 400 years the illusion had escaped even the most astute scientists and historians-as well as Margolis himself, who referenced Tycho's compromise in his 1987 book Patterns, Thinking & Cognition (Chicago) and only noticed the illusion while writing a Ptolemaic tutorial for his 1993 book Paradigms and Barriers (Chicago). The illusion's mysterious persistence was originally to be the topic of Margolis's current book.

But the more he studied the phenomenon, the more interested he became in the larger question of why, by the late 16th century, astronomers' "habits of mind" were shifting away from Ptolemy and towards seeing the world as Copernicus saw it. Since Tycho was a symptom of this larger shift, Margolis set aside the curious illusion and turned instead to Copernicus.

In 1543 the Polish astronomer Nicolaus Copernicus published De Revolutionibus, proposing that the Sun is the fixed point to which the planets' motions refer and that the Earth itself is a planet that also orbits the Sun annually. Shocking ideas, yes, says Margolis, but it's Copernicus's method that precipitated a revolution.

The schism lies between Ptolemy's what-you-see-is-what-you-get method of direct inquiry and what Margolis calls Copernicus's "around-the-corner inquiry." When Ptolemy traced the planets' paths from month to month and year to year, he saw that they looped like pretzels. He explained the loops by embedding an epicycle within each solid sphere, like a circular track mounted on a merry-go-round platform. If a toy train chugged around the track as the merry-go-round whirled, Margolis explains, the train would trace out looping motions like those seemingly traced by the planets.

Copernicus had a hunch that a simpler explanation lay behind this clumsy apparatus. What Copernicus found in pursuing his hunch was "not the heliocentric idea but a reason to take that idea seriously," writes Margolis: "that if the Earth might orbit the Sun, then the looping motions of the planets would be reduced to mere illusions of parallax." Copernicus had an unwitting helpmate: Columbus, whose westward path in 1492 proved the flat Earth actually had a backside. It took until 1508 for this second continent to be published as a map-and find its way into the astronomer's library. If the Earth were round, suddenly the possibility that it also moved wasn't so ludicrous.

Copernicus discovered a reason to take the heliocentric idea seriously because he "had the boldness to look around a corner no one else had thought to explore," thus initiating the crack in scientific inquiry that would strand Ptolemy on the other side. Such inquiry, Margolis argues, "turns discovery in science from a process which needs an epiphany...into a process that might sometimes (or even ordinarily) need two or more epiphanies: the promising hunch, then eventually another hunch about where to look for some striking evidence or novel argument that could support or clarify or (also crucial, since that is often what it deserves) embarrass the original hunch."

Epiphanies, he continues, "only come to people who have been persistent in thinking hard about relevant things. Hence that second epiphany only comes to someone alert to the likelihood that a second epiphany is just what is needed."

What changed around 1600, then, writes Margolis, "was not something explicit but a habit of mind," which we take so much for granted nowadays that the shift required to embrace it has become invisible. As evidence, he cites four scientists whose methods were strikingly similar: Simon Stevin, the Flemish mathematician who demonstrated the law of free fall; William Gilbert, the British physician who proposed that the Earth is a magnet; Johannes Kepler, the German astronomer who discovered the elliptical paths of the planets; and Galileo, the Italian astronomer and mathematician who made fundamental contributions to the development of the scientific method. All were either explicitly or implicitly Copernicans.

Why did it take until the early 1600s for scientists to follow Copernicus's 1543 lead? Here Margolis describes a peculiar quirk of social knowledge. "When something takes hold as social knowledge," he explains, "it begins to seem automatically both more economical and more comfortable." These are the two conditions, he says, under which people-scientists included -make up and change their minds. "Sometimes logically, sometimes merely by trained inattention, we learn to ignore aspects of it that might otherwise seem clumsy." The heliocentric idea, he suggests, had simply been around long enough that it was no longer so shocking, and Tycho had primed the pump with his compromise, illusory though it was. Copernicus's theory was clearly economical in the way it untied the pretzels, and by the early 1600s it was comfortable too.

Yet despite this shift, Tycho's illusion went unnoticed. Why? Because humans, even brilliant ones like Kuhn, are not always rational, argues Margolis, who is among a growing group of academics studying the tendency to be irrational-or, as he puts it, "illogical, and more often so than we can notice." He cites the passionate debates recently sparked by the findings that having mammograms does not prevent women from dying of breast cancer or help them avoid mastectomies. "If you read the study, it makes logical sense," he explains, but people don't want to let go of a "cognitive illusion"-that having regular mammograms will keep them healthy-they'd trusted for so long.

With It Started with Copernicus, Margolis shows that everyone is susceptible to illogic-mathematicians and astronomers, popes and peasants. The next task for academics who study public policy, he says, is to sidle up to a Grand Canyon and figure out what happened there.
-S.A.S.

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