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Carl Sagan on Epicycles, Ptolemy, and Kepler
Pathological Science - #2
The Copernican myths
The real story of how the scientific and religious establishments greeted the Copernican revolution is quite different from the folklore. And it's a lot more interesting.
Nicolaus Copernicus(1473–1543) Perhaps the most famous of all scientific revolutions is the one associated with Nicolaus Copernicus (1473–1543). The popular version of the story goes as follows:
The ancient Greeks, although they were great philosophers and good at mapping the motions of stars and planets, tended to create models of the universe that were more influenced by philosophical, aesthetic, and religious considerations than by observation and experiment.
The idea that Earth was the stationary center of the universe, and that the stars and planets were embedded in spheres that rotated around Earth, appealed to them because the circle and the sphere were the most perfect geometric shapes.
In the Christian era, the model also pleased religious people because it gave pride of place to human beings—God's special creation. The prestige of Greek philosophers like Aristotle was so great, and commitment to religious doctrine so strong, that many scholars stubbornly tried to retain Ptolemaic astronomy even though increasingly complicated epicycles had to be added to make the system work even moderately well.
So when Copernicus came along with the correct heliocentric system, his ideas were fiercely opposed by the Roman Catholic Church because they displaced Earth from the center, and that was seen as both a demotion for human beings and contrary to the teachings of Aristotle. Therefore the Inquisition persecuted, tortured, and even killed those who advocated Copernican ideas.
Johannes Kepler(1571–1630) Because of the church's adherence to philosophical and religious dogma, scientific progress was held back for a millennium. It was the later work of Tycho Brahe (1546–1601), Johannes Kepler (1571–1630), Galileo Galilei (1564–1642), and Isaac Newton (1642–1727) that finally led to the acceptance of heliocentrism.
Variations on this breezy version of the Copernicus story are common in science textbooks.1 How much of the story is true? Apart from the final sentence, not much. But it's a good illustration of how scientific folklore can replace actual history.
Galileo Galilei(1564–1642) Let us start with the myth that the Copernican model was opposed because it was a blow to human pride, dethroning Earth from its privileged position as the center of the universe. Dennis Danielson, in his fine article on the subject,2 shows how widespread that view is by quoting the eminent geneticist Theodosius Dobzhansky. With Copernicus, Dobzhansky contends, 'Earth was dethroned from its presumed centrality and preeminence.' Carl Sagan described Copernicanism as the first of a series of 'Great Demotions . . . delivered to human pride.' Astronomer Martin Rees has written, 'It is over 400 years since Copernicus dethroned the Earth from the privileged position that Ptolemy's cosmology accorded it.' And Sigmund Freud remarked that Copernicus provoked outrage by his slight against humankind's 'naive self-love.'
The squalid basementDanielson, however, points out that in the early 16th century, the center of the universe was not considered a desirable place to be. 'In most medieval interpretations of Aristotelian and Ptolemaic cosmology, Earth's position at the center of the universe was taken as evidence not of its importance but . . . its grossness.'
In fact, ancient and medieval Arabic, Jewish, and Christian scholars believed that the center was the worst part of the universe, a kind of squalid basement where all the muck collected. One medieval writer described Earth's location as 'the excrementary and filthy parts of the lower world.' We humans, another asserted, are 'lodged here in the dirt and filth of the world, nailed and rivetted to the worst and deadest part of the universe, in the lowest story of the house, and most remote from the heavenly arch.' In 1615 Cardinal Robert Bellarmine, a prominent persecutor of Galileo, said that 'the Earth is very far from heaven and sits motionless at the center of the world.'2
n Dante Alighieri's The Divine Comedy, hell itself is placed in Earth's innermost core. Dante also speaks of hell in ways consistent with Aristotelian dynamics—not full of flames, which would be displaced skyward by the heavier Earth, but as frozen and immobile.
By contrast, heaven was up, and the further up you went, away from the center, the better it was. So Copernicus, by putting the Sun at the center and Earth in orbit around it, was really giving its inhabitants a promotion by taking them closer to the heavens.
When and why did the history become distorted? Danielson doesn't pinpoint when the erroneous view gained supremacy, But he says that from 1650 onward one can find some writers making this revisionist claim. By the late 18th century it had taken hold completely. Johann Wolfgang von Goethe (1749–1832), for example, wrote: 'Perhaps no discovery or opinion ever produced a greater effect on the human spirit than did the teaching of Copernicus. No sooner was the Earth recognized as being round and self-contained, than it was obliged to relinquish the colossal privilege of being the center of the world.' Here Goethe managed to propagate another major distortion: the notion that before Copernicus (and Columbus) it was not known that Earth was a sphere.3,4
Aristotle's cosmologyEven Aristotle did not believe Earth to be the center of the universe. He thought it rather to be at the center. This fine distinction was not driven by religious dogma or human self-importance but by physics arguments: In Aristotle's cosmology the universe was finite and the heavens existed beyond its outermost sphere. The universe had a center—defined as the center of the large outer sphere in which the stars were embedded—and matter was drawn to that center. In that cosmology, 'up' and 'down' were well defined. 'Down' was toward the center of the universe and 'up' was away from it, toward the sphere containing the stars.
The elements were earth, air, water, and fire, and each element had its natural affinity for a location in the universe. As could be seen from the fact that rocks fell to the ground, earth, being heavy, was drawn to the center. Flames leaping upwards showed that fire, being light, was drawn towards the heavens. The model explained many things, such as why objects fell to the ground when released from any point and why Earth's surface was spherical. It also explained why Earth was motionless at the center. For it to move, there would have to be something that took it away from the center. And no such agent was in evidence.
http://www.theroadtoemmaus.org/RdLb/11Phl/Sci/PatholSci2.htm
http://www.youtube.com/watch?v=faqjmAoXpM4&playnext_from=TL&videos=-QnG3Yzgui0&feature=grec
The Copernican myths
The real story of how the scientific and religious establishments greeted the Copernican revolution is quite different from the folklore. And it's a lot more interesting.
Nicolaus Copernicus(1473–1543) Perhaps the most famous of all scientific revolutions is the one associated with Nicolaus Copernicus (1473–1543). The popular version of the story goes as follows:
The ancient Greeks, although they were great philosophers and good at mapping the motions of stars and planets, tended to create models of the universe that were more influenced by philosophical, aesthetic, and religious considerations than by observation and experiment.
The idea that Earth was the stationary center of the universe, and that the stars and planets were embedded in spheres that rotated around Earth, appealed to them because the circle and the sphere were the most perfect geometric shapes.
In the Christian era, the model also pleased religious people because it gave pride of place to human beings—God's special creation. The prestige of Greek philosophers like Aristotle was so great, and commitment to religious doctrine so strong, that many scholars stubbornly tried to retain Ptolemaic astronomy even though increasingly complicated epicycles had to be added to make the system work even moderately well.
So when Copernicus came along with the correct heliocentric system, his ideas were fiercely opposed by the Roman Catholic Church because they displaced Earth from the center, and that was seen as both a demotion for human beings and contrary to the teachings of Aristotle. Therefore the Inquisition persecuted, tortured, and even killed those who advocated Copernican ideas.
Johannes Kepler(1571–1630) Because of the church's adherence to philosophical and religious dogma, scientific progress was held back for a millennium. It was the later work of Tycho Brahe (1546–1601), Johannes Kepler (1571–1630), Galileo Galilei (1564–1642), and Isaac Newton (1642–1727) that finally led to the acceptance of heliocentrism.
Variations on this breezy version of the Copernicus story are common in science textbooks.1 How much of the story is true? Apart from the final sentence, not much. But it's a good illustration of how scientific folklore can replace actual history.
Galileo Galilei(1564–1642) Let us start with the myth that the Copernican model was opposed because it was a blow to human pride, dethroning Earth from its privileged position as the center of the universe. Dennis Danielson, in his fine article on the subject,2 shows how widespread that view is by quoting the eminent geneticist Theodosius Dobzhansky. With Copernicus, Dobzhansky contends, 'Earth was dethroned from its presumed centrality and preeminence.' Carl Sagan described Copernicanism as the first of a series of 'Great Demotions . . . delivered to human pride.' Astronomer Martin Rees has written, 'It is over 400 years since Copernicus dethroned the Earth from the privileged position that Ptolemy's cosmology accorded it.' And Sigmund Freud remarked that Copernicus provoked outrage by his slight against humankind's 'naive self-love.'
The squalid basementDanielson, however, points out that in the early 16th century, the center of the universe was not considered a desirable place to be. 'In most medieval interpretations of Aristotelian and Ptolemaic cosmology, Earth's position at the center of the universe was taken as evidence not of its importance but . . . its grossness.'
In fact, ancient and medieval Arabic, Jewish, and Christian scholars believed that the center was the worst part of the universe, a kind of squalid basement where all the muck collected. One medieval writer described Earth's location as 'the excrementary and filthy parts of the lower world.' We humans, another asserted, are 'lodged here in the dirt and filth of the world, nailed and rivetted to the worst and deadest part of the universe, in the lowest story of the house, and most remote from the heavenly arch.' In 1615 Cardinal Robert Bellarmine, a prominent persecutor of Galileo, said that 'the Earth is very far from heaven and sits motionless at the center of the world.'2
n Dante Alighieri's The Divine Comedy, hell itself is placed in Earth's innermost core. Dante also speaks of hell in ways consistent with Aristotelian dynamics—not full of flames, which would be displaced skyward by the heavier Earth, but as frozen and immobile.
By contrast, heaven was up, and the further up you went, away from the center, the better it was. So Copernicus, by putting the Sun at the center and Earth in orbit around it, was really giving its inhabitants a promotion by taking them closer to the heavens.
When and why did the history become distorted? Danielson doesn't pinpoint when the erroneous view gained supremacy, But he says that from 1650 onward one can find some writers making this revisionist claim. By the late 18th century it had taken hold completely. Johann Wolfgang von Goethe (1749–1832), for example, wrote: 'Perhaps no discovery or opinion ever produced a greater effect on the human spirit than did the teaching of Copernicus. No sooner was the Earth recognized as being round and self-contained, than it was obliged to relinquish the colossal privilege of being the center of the world.' Here Goethe managed to propagate another major distortion: the notion that before Copernicus (and Columbus) it was not known that Earth was a sphere.3,4
Aristotle's cosmologyEven Aristotle did not believe Earth to be the center of the universe. He thought it rather to be at the center. This fine distinction was not driven by religious dogma or human self-importance but by physics arguments: In Aristotle's cosmology the universe was finite and the heavens existed beyond its outermost sphere. The universe had a center—defined as the center of the large outer sphere in which the stars were embedded—and matter was drawn to that center. In that cosmology, 'up' and 'down' were well defined. 'Down' was toward the center of the universe and 'up' was away from it, toward the sphere containing the stars.
The elements were earth, air, water, and fire, and each element had its natural affinity for a location in the universe. As could be seen from the fact that rocks fell to the ground, earth, being heavy, was drawn to the center. Flames leaping upwards showed that fire, being light, was drawn towards the heavens. The model explained many things, such as why objects fell to the ground when released from any point and why Earth's surface was spherical. It also explained why Earth was motionless at the center. For it to move, there would have to be something that took it away from the center. And no such agent was in evidence.
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