Friday, October 16, 2009

"When I consider Thy heavens, the work of Thy fingers..."

Toby Lester explains how "when America showed up on a map, it was the universe that got transformed" — how a map confirmed the views of a Polish priest and revolutionized the way we understand the cosmos:
.... WHEN CHRISTOPHER COLUMBUS first sailed west from Spain in 1492 in search of the Indies, nobody worried that he would sail off the edge of the earth. Medieval Europeans knew full well that the world was a sphere, and that if you sailed far enough to the west you would arrive in the east.

In that sense, they understood the shape of the world. But when they set their sights beyond the earth, they still relied on a 2,500-year-old model of the universe, one that scholastics during the Middle Ages had made fundamental to Christian theology. According to teachings that dated to Aristotle, the cosmos as a whole consisted of a set of concentric spheres. At the center was the earth, a solid ball of land. Surrounding the earth, successively, were spheres of water, air, and fire; then individual spheres for the moon, the sun, and the planets; and finally, at the outer limits, a single sphere studded with stars, beyond which lay a realm of pure abstraction, or God. Each of these celestial spheres rotated around the earth at its own pace.

This model did a serviceable job of explaining the apparent motions of the heavens, but it had a fundamental problem. If the cosmos did indeed consist of a set of spheres with the earth at its center, then why wasn’t the earth completely submerged in the sphere of water that surrounded it? Why was there any exposed land at all?

European scholars in the late Middle Ages devised a way of explaining this problem away. The earth, they suggested, bobbed slightly off-center in the sphere of water, “like an apple in a basin,” as one writer put it in 1484. How had this happened? God had simply made it so. The Book of Genesis told the story: “And God said, Let the waters under the heaven be gathered together unto one place, and let the dry land appear.” In practical terms, scholars explained, what God had done in working this miracle was to push the sphere of the earth to one side of the sphere of the water, exposing part of it to the air and creating the contiguous lands that would come to be known as Asia, Europe, and Africa.

Copernicus knew the theory of the off-center earth well from his student days. But he didn’t buy it. Mathematically, geometrically, logically — it just didn’t make sense to him. Anybody could see that the earth’s landmass didn’t gradually and uniformly mount upward from the sea toward a high point somewhere in the middle of the known world, as this model suggested it should. “Furthermore,” he wrote in the geographical section with which he opened On the Revolutions, “the depth of the abyss would never stop increasing from the shore of the ocean outward, so that no island or reef or any form of land would be encountered by sailors on the longer voyages.”

But Copernicus went on to add that he had recently come across even more compelling evidence against this theory. And this evidence can only have come from the Waldseemüller map. ....

Copies of the map seem to have circulated widely in the early 16th century. In the years immediately after 1507, it reached a number of German university towns, where professors probably used it as a classroom prop. By 1512, it had made it to Poland, where Jan de Stobnicza, a professor of philosophy at the University of Krakow, published his own partial copy.

Nobody who saw the map could miss what dominated its left side. Rising majestically out of the western ocean, extending deep into the southern hemisphere, was a huge new continent. And printed across the region we now know as Brazil was a strange new name: America. ....

At the time Copernicus came across the Waldseemüller map, he had already begun to look for evidence that would support his new theory of the cosmos. And when he saw America on the map, he knew he had found what he was looking for. The location of this new continent, he realized, disproved the theory of the off-center earth.

If the earth really did bulge out of one side of the sphere of water, he reasoned, then the ocean had to get deeper and deeper the farther one sailed away from the shores of the known world. Land, in other words, could not protrude from opposite sides of the sphere of water. And yet that’s exactly what Copernicus saw happening on the Waldseemüller map. Here was a giant southern continent far off in the western ocean, located diametrically opposite to the known world.

There was only one way to explain this oddity, Copernicus decided: The watery sphere must not exist at all. The earth and its oceans had to be one, and in that single globe there had to be much more earth than water.

Quite suddenly, at its very core, the old model of the cosmos was falling apart. If the theory of an off-center earth was directly at odds with geographical reality, as the Waldseemüller map showed it to be, then the time had come, it seemed to Copernicus, to think about the cosmos from an entirely different perspective.

Perhaps it was not the heavens that were in motion, but the earth. .... [more]
There are those who seem to think that the conclusions Copernicus drew ought to have shaken — even destroyed — the faith of Christians. I'm not sure why. I'm unaware of any evidence that Copernicus — or Galileo — thought the discovery in any way brought God into question.

A world redrawn: When America showed up on a map, it was the universe that got transformed - The Boston Globe

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