Gregory chap 9

Gregory chap 9 - I76 CHAPTER 8 ISAAC NEWTON A HIGHPOINT OF...

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Unformatted text preview: I76 CHAPTER 8: ISAAC NEWTON: A HIGHPOINT OF SCIENTIFIC CHANGE CHAPTER 9 March 2, 1727. As he lay dying later that same month, Newton affirmed the ribil— lious religious stance he had so long embraced by refusmg the slacrfimeitso .te e church. Three days after his death on March 20, the“ records of tie. on ocr gy marked his passing with the terse announcement: The Cha’ir being acant y the Death of Sir Isaac Newton there was no Meeting this Day. f When Isaac Newton set off for Cambridge University in the early summer 0 1661 there was not yet a consensus about the viability of the new Copernican View of the cosmos. Galileo had offered a reason why planets would continue to move forever around the sun in circular orbits, but Kepler had shown that the orbitsgvege not circular. Why did the planets continue to. move in elliptical orbit; :rmin t ef sun? Not only did Newton give the answer in the Priznegozn throug ais Haws 10 motion and universal gravitation, but his answer prov1ded a means of an yzucilg t 1e motions of all matter, whether in the heavens or here on Earth. Newton funitl: nat- ural philosophy into one comprehensive system that would dominate or t e next two centuries. ——————©—————— Newtonianism, the Earth, and the Universe During the Eighteenth Century © Suggestions for Reading Gale E. Christianson, In the Presence of the Creator: [sane Newton and His Times (New Y 1: Free Press, 1984). . I ’ . I Bettjjr]; Teeter Dobbs, T/aefzznm Faces of Genius (Cambridge: Cambridge Unrversrty P s, 2002). I .- Richrafrsd Westfall, Never at Rest: A Biography of [sane Newton (Cambridge: Cambridge University Press, 1983). The novel ideas that came into science in the seventeenth century were incompat— ible in many. ways with the more comfortable cosmos of former times. Copernicus had already moved the Earth off to the side, away from the center of the system of spheres that had always provided humans a home. But even in the early versions of the Copernican system, including that defended by Galileo, the cosmos at least remained finite in extent. After Descartes and especially after Newton, it was no longer possible to insist that space did not extend infinitely in all directions. It took some time to build a consensus about the meaning of Newton’s achieve— ment. After all, there was much more about it to disagree with than just the question , of whether the universe had a center or not. The linchpin on which all depended in Newton’s system was his notion of an attractive force that acted at a distance. For mechanical philosophers who continued in the heritage of Descartes, this was a major stumbling block. The transmission of Newton’s force appeared to make use of an intervening medium that was occult, and that was simply unacceptable to them. © The Rise ofNewtonianism (Q In spite of the fame Newton enjoyed among his fellow British citizens, his system initially found few followers abroad. After 1730 Newton’s system began to attract followers—particularly in France—who defended a worldview that has been called 'Newtonianism. But prior to 1730, the continuing influence of Rene Descartes in France and Gottfried Leibniz in the German states was sufficient to assure that the Cartesian and Leibnizian worldviews provided strong competition for Newton’s I77 178 CHAPTER 9: NEWTONlAleM, THE EARTH, AND THE UNIVERSE thought. Only in Holland did Newton’s system find avid defenders across the English Channel. Competing Systems of Natural Philosophy The basic assumptions individual natural philosophers made. about how nature worked determined differences among them that carried implications throughout their systems. In the early eighteenth century these differences produced an important debate about force and action in nature and also involved the issue of Gods relation— ship to the natural world. Cartesians, Leibnizians, Newtonians. The most important issue separating Newton’s system from those of Descartes and Leibniz remained an understanding of the nature of force. The Cartesian position was clear: force was a push or pull that acted on material objects by means of material contact. All natural effects were due to mechanical motions of matter, making the appeal of the CarteSian philosophy its intu— itive clarity. Cartesians in the first half of the eighteenth century did not feel obligate:l to accept the specific mechanical motions Descartes had used to explain indiv1 u phenomena, but they did not doubt that things like magnetism resulted from some combination of such motions. Descartes exerted a strong hold on the french mind because his readers understood him to have clarified the basis for intelligibility itself in physics. ‘ Because followers of Descartes insisted that force was transmitted only through collisions of matter, they refused to associate force with nonmaterial agenCies in nature. Nature was a realm of the material. It was unacceptable to. offer explana— tions of natural phenomena that depended on spiritual or nonmaterial occult agen— cies. To Cartesians, the assertion that force acted at a distance was equivalent to an eal to a nonmaterial a enc . . aplLeibniz’s system was fgeprelsented after his death by the natural philosopher Christian von Wolff, whose work was available to German readers Wltl'lln- a year of Leibniz’s death in 1715. Wolff regarded Descartes’s explanations of the physical world as helpful but limited. The Cartesian approach applied to what we see, but it did it: relate to the deeper reality Wolff believed lay beneath appearances. For the superficr level of appearances, Wolff was content to embrace Descartes s mechanical lnFEl‘aCthfiS to make the appearances intelligible. To explain how force acted, he too rejected t e occult agencies of medieval Scholastic thought (and therefore also action at a'distance) in favor of forces transmitted only through contact between masses. Like his mentor Leibniz, he described the physical world as a clock designed by God to work perfectly. Wolff emphasized Leibniz’s appeal to the principle of suffic1ent reason, according to which we understand the existence of something when we find the reason for it. Because everything has a sufficient reason, we can use our reason to show that the world has been made perfectly. ' The difference between the Leibnizians and the CarteSians emerged at the deeper level of reality’s basic components. Leibniz had held that matter was not equivalent to extended space, as Descartes taught, but was made up of unextended pomts he called ' mmamwmmiaw»an:wmWiWXéamassawWmmmsawuwmiamawmwmmmémmwmmmammmmammgwmkwwawmm THE RISE OF NEWTONIANISM monads. Monads were nonmaterial metaphysical entities that resembled souls. They were the source of the force; indeed, they were the source of all the activity that accom- panied matter. By making a distinction between the source of force and the means by which it was transmitted, Leibnizians were both critical of Newton’s action at a dis- tance and of Descartes’s banishing of spirit from the natural world. Newton’s cause was taken up abroad by the Dutchman W J. ’sGravesande (1688—1742), who published an introduction to the philosophy of Newton in 1720. ’sGravesande answered those critics of Newton who asserted that his action at a dis— tance amounted to a return to occult causes by declaring that gravity was not the cause of anything. It was an effect. Gravity was the name we give to the movement of bod— ies toward one another when left to themselves. According to ’sGravesande, physics should focus its attention on the results of experiments rather than try to devise grand causal explanations. Like other Nevvtonians in England, he ignored Newton’s own attempt to find a cause for gravitational force in the special kind of ethereal substance that Newton made public in the 1717 edition of the Optic/es. When Newton died in 1727, many who defended his system shunned the question of the cause of gravity, understanding the system to rest simply on Newton’s laws of motion and a gravita— tional force that acted at a distance according to the inverse square law. The vis viva controversy. Over the course of the eighteenth century Cartesians, Leibnizians, and Nevvtonians became embroiled in a disagreement known as the 212's oil/a controversy. It centered on the question of whether force in the universe could be lost—that is, whether the total amount of force in the cosmos could become dimin— ished, in which case the cosmos, left to itself, would run down and eventually come to a standstill. To many this prospect was inconsistent with their understanding of God’s creative abilities. But if force was conserved and could not be lost, how was force to be measured? In his Princzples of Philosophy, Descartes had asserted that because God was unchangeable, he “conserves the world in the same action with which he created it.” Descartes envisioned the universe as he imagined God saw it from the outside—a realm filled with material objects in motion. All this motion, which involved many collisions of matter, constituted the world’s action or activity. Descartes felt that God had invested this activity in the world at the Creation and that he held it constant. The constant exchange of motion over time among portions of matter constituted the history of nature itself. Descartes felt that the universe was a machine that would not run down because, in spite of the exchanges, God made sure that no motion was lost. The sum total of all the activity always remained the same because God had given to individual motions of matter the property, as Descartes put it, “of passing from one to the other, according to their different encounters.” But how was one to measure this “action”? Discussion of this problem continued into the eighteenth century and beyond, pitting those who preferred Descartes’s measure—something he called the “quantity of motiOii”—agaiiist others who opted for something Leibniz called 222': viva. \X/hen Descartes asked himself what might be a measure of the quantity of motion, he thought about the force that a piece of matter exerted when it encountered another 179 180 CHAPTER 9: NEWTONIANISM, THE EARTH, AND THE UNIVERSE piece of matter. That, he reasoned, obviously depended on two factors: how big the mass was and how fast it was moving. He concluded that the force of motion could be expressed as the product of mass (m) and velocity (v), and he determined that this was a measure of the quantity of motion. If we consider just two pieces of matter moving toward each other, we can calculate the force of motion of the first piece (m, 2/1) and also that of the second (7722112 ). Adding these two amounts, we have the total force of motion of the two (ml 711 + 7713U2). Descartes held that, after the collision, this total amount remained the same, although the individual velocities of the two pieces of matter might change. Whatever velocity was given up by one piece of matter was given to the other, so that the total sum of the masses times their velocities remained the same. What happened in the case of just two pieces of matter also happened in every other collision in the universe. The sum total of what Descartes identified as the force of motion remained the same, while the changes in the velocities of individual pieces of matter due to collisions constituted the activity of the universe. For Descartes, God’s immutability meant that the total force of motion in the universe was conserved and the universe would run forever. There are problems with Descartes’s claim, the most obvious of which is that it does not work for what are called inelastic collisions. If two equal blobs of clay move directly toward each other at equal velocities, when they collide they do not rebound at the same velocity but stick together, and the motion stops. What hap- pened to the total force of motion in this case? It would appear that it has not been conserved but destroyed. To incorporate situations like this into Descartes’s analy— sis, his follower, Christian Huygens, asserted that it was necessary to specify the direction in which the masses were moving. In other words, the forces of motion of masses moving directly toward each other must be considered opposite in sign. If in the above case the masses are equal, and if the first mass of clay is assigned a positive force of motion (+ my), then the second would have an equal negative force of motion (—— 7722/). Adding up the total before and after the collision would give zero in both cases. Had the masses not been clay, but some perfectly elastic substance, then the total force of motion would still have been zero before and after the collision, except that the velocities of the two equal masses would have changed sign as they rebounded from each other. The contrary motions God had put into the universe at its beginning balanced each other in the end. This improvement made by Huygens, however, still left a major problem. With every inelastic collision there would be less motion in the universe. That would mean that the actual motion in the universe was running down, a result unacceptable to Descartes. He had proposed his idea in order to guarantee that the machinery of the universe would continue to run. In an article in 1686 entitled “A Brief Demonstration of a Notable Error in Descartes,” Leibniz pointed out that Descartes’s measure of the force of motion would not, in fact, prevent the universe from running down. He proposed a differ- ent measure of the force of motion, something he called 111': vim, or “living force.” The problem of the running down of the universe was an issue as long as the force of motion was regarded as a signed quantity—one that could be positive or negative. As such one force could destroy another, diminishing the total God had originally mwwmeMMmWWMW/nWMW/ww . MmmmmmwmmmWmmwxmmsmwmzw THE RISE OF NEWTONIANISM invested in his creation. Leibniz proposed that a better measure of the force of motion was proportional to the mass times the square of the velocity (771112), which was always a positive quantity. He claimed that in inelastic collisions, like the one involving blobs of clay, the vi: aim: was not destroyed when the pieces of clay stopped moving after collision; rather, the motion was transferred to the particles that made up the clay. So the total motion continued at another level, the amount of 111': vz'wz in the universe remained the same, and the universe did not run down. Many people did not accept 212': vim, if for no other reason than it was too abstract a notion. Nor was Leibniz persuasive with his explanation of why 212's viva was not lost during inelastic collisions. Among those who came out in favor of 111': viwz as a meas- ure of the force of motion was the Dutch Newtonian, ’sGravesande. His major con— tribution to the discussion—which resulted from his wish to base conclusions as much as possible on experiments——was to think of measuring the efiéct a moving mass might have, rather than merely the force it might exert. Thinking of the force of a mass in motion as the afict (or damage) the mass produced in a collision, as opposed to the pus/7 exerted during a collision, proved to make a difference. ’sGravesande did a series of experiments in which he dropped masses onto clay and then measured the dents that were made. He varied the heights and the weights of the masses, measuring the various dents produced. He found that the impressions in the clay were the same if, when he used a mass with half the weight of another (although of the same size and shape), he dropped it from twice the height. Descartes, of course, would conclude that, if the dents were the same in the two cases, then the measure of the motion should be mu in both cases. But ’sGravesande showed that because the lesser mass was dropped from a greater height, it hit the clay at a greater speed (Viv). He demonstrated that the product of the lesser mass (Vzm) and the greater velocity (Viv) was not 7720, but $77211. He concluded therefore that Descartes’s measure of the force of motion, mass times velocity, had to be in error. ’sGravesande said the correct measure of the force of motion was %mv2. This meas— ure covered both of the preceding cases. In the first case, when the mass was 772 and the velocity was 1/, his formula gave Van/2212. In the second case, when the masswas 1/2772 and the velocity was Viv, the product of one—half the mass times the velocity squared also gave Vzmvz. So for ’sGravesande the measure of the force of motion caus— ing the dent made in the first case did equal that causing the dent made in the second. ’sGravesande had shown to his own satisfaction that Leibniz’s 112's viwz was a better measure of the force of motion than Descartes’s quantity of motion. By siding with Leibniz here, ’sGravesande not only opposed the Cartesians. In this instance he also went against Newton, who did not regard vi: vim as anything real. Just as Leibniz had found, ’sGravesande discovered that not everyone immediately agreed with him; in fact, the debate about conservation of quantity of motion and of vi: viwz continued throughout the eighteenth century. The discussion, recall, had been initiated in a theological context having to do with God’s preservation of action in the world. With the exception of those who agreed with Newton (who felt that God would step in to correct the universe if it ran down sufficiently), it was impor- tant to the participants in the discussion to find an explanation that would prevent the universe from slowly degrading. 181 182 Voltaire CHAPTER 9: NEWTONIANISM, THE EARTH, AND THE UNIVERSE The Growth ofNewton’s Reputation Newton’s work finally came to the attention of a wider public in France through a popular account of its basic conclusions that appeared in 1733. In addition, a pum- ber of issues came to the surface after 1730 whose outcomes promoted Newtons rep- utation as a man ahead of his time. Not only had he seen farther than those who came before him, but in some cases he appeared to have anticipated solutions to problems that arose only after he had departed. The accumulated effect of these developments contributed to the emergence by the latter part of the century of a prominent group of French Newtonian natural philosophers. The popularization of Newton in France. The introduction of Newton’s ideas to many in France occurred in 1733, when Francois Marie Arouet, who had taken the pen name Voltaire, published his Philosophical Letters. The French authorities had imprisoned Voltaire earlier in his career because of satirical things he had written about the French government. When he insulted a powerful nobleman in 1726, he was given the choice of another stint in prison or a period in exile. He chose the latter, living in England for the next three years. While in England he studied the customs of the English, their form of government, and the ideas of their philosophers, and he was especially drawn to the work of Newton. In his Letters he praised Newton, whom he called “this destroyer of the Cartesian sys— tem,” and went on to present a comparison ofNewton’s system to that of his countryman Descartes. After declaring that Newton had proven by experiments that Descartes was wrong about the universe being filled everywhere with matter, Voltaire proclaimed that Newton “brings back the vacuum, which Aristotle and Descartes had banished from the world.” In the Letters Voltaire carefully explained the role played by gravitational force, “the great spring by which all Nature is moved,” reproducing a summary of Newton’s proof that the moon and planets are held in their orbit by this force. The reader quickly realized that in Voltaire’s view Newton’s system was far superior to any other. Along with his preference for Newton, it was clear that Voltaire also preferred English customs, laws, and society to their French counterparts. The message of the book got Voltaire into trouble once more and he again had to leave Paris. He took refuge in the independent province of Lorraine at the chateau of the marquise du Chatelet, a friend he had recently met and with whom he collaborated until her death in 1749. ' l « (Maomhmmaammmrmzwmlnmwwwmmmw THE RISE OF NEWTONIANISM Du Chatelet also contributed to the popularization of Newton’s thought. She collaborated with Voltaire on the publication in 1738 of Elements of the Philosophy of Newton, a more complete exposition of the Newtonian system than Voltaire’s earlier work. She also completed a translation into French of Newton’s Primzpz'rz, which appeared after her death. Although du Chatelet aligned herself with the Newtonian “party,” as the growing number of French defenders of Newton called themselves, she was not a slavish follower of Newton. Persuaded of the merits of Leibnizian metaphysics, she also published a book on Leibniz’s system in 1740. The controversy over the shape of the Earth. The question about whether the Earth’s shape resembled an egg or a pear provoked a controversy that ended up pitting the systems of Newton and Descartes against each other during the 17405. Earlier in the century a long—standing project to map the kingdom of France had uncovered discrepancies in the terrestrial lengths of degrees of longitude. The leader of the project repeated the measurements to confirm their accuracy, and announced to the Paris Academy in 1718 that the results meant that the Earth was not spherical, as everyone had assumed, but that it had a slightly elongated shape, something like that of an egg. The problem was that both Newton and the Cartesian Christian Huygens, basing their conclusions on calculations made from their respective systems of mechanics, had much earlier predicted that the Earth should bulge slightly at the equator, like a pear. Initially, the question had been whether to believe the predictions of natural philosophers or a claim that appeared to rest on careful measurement. In the 17305 and 17405 the question became something very different. Pierre—Louis Moreau de Maupertuis (1698—1759), son of a recently ennobled mer— chant, went to Paris as a teenager to study philosophy, but soon found his real interest was mathematics. In the early 17205, while Maupertuis was learning the intricacies of higher mathematics, he became aware that the disagreement about the shape of the Earth bore on theoretical systems he had been studying. In the summer of 1728 he spent twelve weeks in London, where he immersed himself in Newton’s work. Between 1732 and 1736 Maupertuis turned his attention to the question of the shape of the Earth. When it was decided that new expeditions would be sent out to determine once and for all whether the Earth was flattened or elongated at the poles, Maupertuis led the group that traveled to the proximity of the North Pole to make meas- urements of the distance along a longitudinal line between two established latitudes. Another group went to the equatorial region of Peru to do the same thing. Because the distance between the equator and the North Pole is divided into equal degrees of lati— tude, any variation in the measured distance between two sets of latitudinal positions would indicate that the Earth was not spherical. A distance less than expected would indicate an elongation, and greater than expected would mean a flattening. There was no reason why the issue of the Earth’s shape had to be regarded as a disagreement between the systems of Descartes and Newton; there were partisans on both sides that made arguments for an Earth flattened at the poles. Nor did most of those arguing about the Earth’s shape initially regard it as a test between these two rival systems. But Maupertuis had taken on the role of a crusader for the Newtonian system, on the one hand recruiting younger impressionable academicians to his side, and on the other ridiculing the Cartesians in the Paris Academy. 183 184 CHAPTER 9: NEWTONIANISIVI, THE EARTH, AND THE UNIVERSE It was a decade before the expedition to Peru returned with its findings. By then the group that had gone to Lapland with Maupertuis had been back for eight years with measurements that proved consistent with an Earth flattened at the poles. Maupertuis exploited these results to the advantage of his defense of Newton; indeed, his duplicity in the affair earned him numerous enemies, some of whom criticized him for defend— ing a foreign English system over the French system of Descartes. Voltaire also helped polarize the issue by portraying Maupertuis as France’s Galileo in his struggle to pro— mote Newton’s system in Paris. The upshot of the matter was that the Newtonian party used the incident to make Newton’s system appear superior to that of Descartes. Questioning the inverse square law. Newton’s reputation in France also grew because his system survived direct challenges. One such challenge surfaced in the late 17405 when a brilliant young French mathematician announced that Newton’s famous inverse square law was incorrect. Alexis Claude Clairaut (1713—1765), son of a Parisian mathematics teacher, was among the gifted young mathematicians who joined the Newtonian party of Voltaire and Maupertuis. Clairaut’s challenge to Newton grew out of his interest in another theoretical challenge—what has become known as the three—body problem. Newton’s original consideration of the problem of the moon’s motion had consid- ered the gravitational interaction of the Earth and the moon. But if the more general conclusion he had come to in the course of solving that problem was true—namely, that all matter attracts all other matter according to an inverse square law—then an object like the moon would be affected by a large body like the sun at the same time it was being attracted by its much nearer neighbor, the Earth. In fact, there were irreg— ularities in the moon’s motion that Clairaut and others hoped to explain by taking the flame mutually attracting bodies into account. The competition for the first successful solution to this three—body problem extended beyond France into Switzerland. Clairaut and his competitors were able to write the equations that described the interacting inverse square attractions of the three bodies, but they then determined that solving them directly was impossible. The best Clairaut or anyone else could do was to devise a means of approximating a solution. The differing methods of approxi- mating a solution used by those engaged in the problem all showed the same unex- pected result: certain positions the moon was predicted to have based on inverse square attractions of the three bodies were way off from the positions the moon was observed to have. Clairaut concluded that the discrepancy was due to the inverse square law itself—it must not be correct as Newton had stated it (f CC 1/ 72); it should rather have the form f <1 (1/ 72 + 1/ 74). (Because 1'4 is a huge number, the correcting factor of 1/ 74 would be tiny.) His public challenge to the authority of the great Isaac Newton, made in an announcement to the French Academy on November 15, 1747, stirred a pot already boiling about the merits and demerits of the Newtonian system. It was not long before Clairaut realized that he had made an error in approximat— ing a solution to the Earth—moonasun problem. In the course of working through the complicated equations he had made a mathematical simplification that seemed harmless, but on closer inspection it proved to make a big difference in the outcome. Clairaut realized that his competitors had also employed the same simplifying i- i i g THE RISE OF NEWTONIANISM assumption and that this explained Why they had all come to the same result. When he corrected his mistake, his approximation of how three interacting inverse square forces affected the moon produced results that agreed with the observed positions of the moon. Less than a year and a half after his first dramatic announcement to the French Academy he made a second one: there was no need to correct Newton’s inverse square law after all. To Newton’s supporters it seemed that the master had known better all along. Halley’s Comet. Newton’s reputation received yet another boost during the 17505 from a prediction that had been made a half century earlier by Edmund Halley. Halley had concluded that a comet that had appeared in 1682 had a path similar to comets that had been observed on four previous occasions, the earliest from 1456. He had determined from the similarity of the paths and from the time between appearances that all the observations had been of the same comet and that it would reappear next about 1758. He refused to be precise about the exact date of the next return of the comet because he could not be sure how large planets such as Jupiter and Saturn might affect the path the comet traversed. Because Clairaut had become the leading expert on the three—body problem, he decided to apply his knowledge of Newtonian mechanics to the problem that Halley could only anticipate. With assistance from a few colleagues, he calculated that the comet would be at its closest point to the sun within thirty days of April 15, 1759. He announced this prediction in the fall of 1758 to the Paris Academy. The comet actually arrived at its closest point two days outside of this thirty—day margin of error, on March 13, but no one considered this an error on Clairaut’s account. The appearance of a comet was something even people on the street were interested in. To them, Clairaut’s prediction meant that he must understand the motions of heavens better than anyone before him had. Being hailed as a new Newton in the public press now brought undisputed fame to the Frenchman, Clairaut. Perfecting celestial mechanics. Another irregularity in the moon’s motion led to the solidification of support for the Newtonian system among French natural philosophers. The problem also originated in Halley’s study of past astronomical events, this time in a paper he had read to the Royal Society in 1693 about the dates of ancient eclipses of the moon. If the machinery of the heavens that Newton had described were run backward, then the position of the moon would not have resulted in an eclipse at those times when eclipses had been recorded. Halley sug— gested that one way to reconcile the discrepancy was to assume that the moon’s orbit had shrunk slightly in the intervening time. As the orbit shrank the moon would revolve at a faster pace around the Earth, thereby decreasing the length of time in a month and providing a means to eliminate the discrepancy mentioned. The gradual shrinkage in the moon’s orbit was in fact confirmed by subsequent observations. \While this strengthened Halley’s suggested solution to the problem of ancient eclipses, it created another problem: it implied that the Earth—moon system was unstable, that it was running down. Yet another brilliant young French Newtonian took up this problem, this time from the generation after Clairaut. Just before the outbreak of the French Revolution, 38—year—old Pierre Simon Laplace (1749—1827) 185 186 CHAPTER 9: NEWTONIANISM, THE EARTH, AND THE UNIVERSE showed that the planets in the solar system exert a gravitational effect that alters the shape of the Earth’s orbit very slightly. As a result of the Earth’s changing position with respect to the sun, a corresponding variation in the sun’s effect on the moon is intro- duced. The presence of this set of perturbing factors is so small that it could only be detected over long periods of time. But did that mean that Laplace had shown the system to be unstable? In fact the opposite was the case. Laplace demonstrated that after many years the factors that caused the moon’s orbit to shrink would begin to move it in the opposite direction. The moon’s orbit underwent an oscillation in and out, one cycle of which took thousands of years. Newton’s universe was stable after all. It would not run down. From this and his other work on Newtonian celestial mechanics, Laplace imagined a determined system of the world, of which we would have perfect knowledge if we could but know “the state of all phenomena at a given instant, the laws to which matter is subjected, and their consequences at the end of any given time.” Others might think it presumptuous and arrogant to speak with such boldness. To Laplace it was simply the perfecting of what Newton had begun. C) An Expanding Cosmos © As we learned in Chapter 2, the notion that God may have created other worlds was long a theological concern. This historical reference to other worlds referred specifically to heavenly homes for living beings. With the growing consensus among natural philosophers of the seventeenth century that Copernicus had cor— rected an ancient error about the structure of the cosmos, interest in this specific theological issue increased. Natural philosophers weighed in on the implications for theology of life elsewhere. Other Worlds Over the course of the eighteenth century speculation about life elsewhere in the universe continued unabated. There were those who objected to the general enthu— siasm in favor of pluralism, as historians have dubbed belief in the existence of other inhabited worlds. The philosopher David Hume based his skepticism on rational analysis. But most of those who objected did so mainly for theological rea— sons, the primary one of which centered on the meaning of Christ’s death on the cross. If there were millions of worlds similar to the one in which we live, then why would God give his son for this one? By far, however, writers in the eighteenth century—whether concerned with theo— logical or philosophical issues—readily accepted the existence of life beyond Earth. They established a consensus of opinion that blurred the lines that otherwise divided religiously minded individuals from each other or that separated religious thinkers from more secular thinkers. It was a consensus that would enjoy remarkable staying power. The rise of the new science had an impact on theological practice beyond merely stimulating interest in the specific question of extraterrestrial life. It also raised the status of natural theology, a branch of theology that had not previously enjoyed prominence. Reasoning in natural theology did not commence with the truths of a . wmmmwmmmmmnwzWWWWmmwmmmnmmmwm«WWWWWWWWW AN EXPANDING COSMOS Systems in . o jncludéjew olar. systems; a divine revelation, as in other branches of theology. The natural theologian began instead with the knowledge of nature. On the basis of evidence of intentional desicrn uncovered in the natural world, natural theologians reasoned to the existence of a divine designer. The development of works of natural theology was not confined to individuals formally trained in theology. Many natural philosophers were delighted that their pursuit of the new science was not only compatible with their personal belief in God, but provided impressive new forms of the argument from design—that it was possible to infer the existence of a designer from evidence of design in nature. Among the early works of natural theology devoted to the plurality of worlds was William Derham’s Astro— T/yeology. Derham was an Anglican clergyman who became chaplain to the Prince of Wales in 1715, the year his Astra—Theology appeared. He wrote the book as a companion to his Playrico— T lieology of 1713, in which his natural theological argument centered on knowledge of terrestrial nature. Both of his works were enormously popular in Britain throughout the eighteenth century, running to fourteen English and six German editions by 1777. In the Astro— T/aeology he used Newton’s work on astronomy not only to justify a Copernican arrangement of the planets around our sun, but also to infer what he called a new system that went beyond the Copernican. Derham argued that “there are many other Systemes of Suns and Planets, besides that in which we have our residence; namely, that every Fixt Star is a sun and encompassed with a Systeme of Planets.n What made Derham confident that so many solar systems existed was that they were “worthy of an infinite Creator.” Nebular Hypotheses Observers of the heavens, even before the invention of the telescope, had identified more than just stars and planets. Some of the lights in the heavens appeared as luminous cloudy patches, which could be mistaken for comets until the observer noticed that the patches retained their position just as stars did. Ptolemy recorded 187 Derham’s Solar Astra—Theology 188 CHAPTER 9: NEWTONIANISM, THE EARTH, AND THE UNIVERSE seven such objects, Tycho Brahe six. Included in the 1690 star catalog of the Polish observer Johannes Hevelius were sixteen “nebulous stars.” Others compiled lists of such nebulae prior to 1750, but it was nor until the second half of the century that they became the focus of attention as possible island universes of their own. In speculations from the time, the concept of nebulae had two distinct mean— ings. Writers referred to nebulae as the distant luminous patches in the sky that, if seen from the proximity we have to our own Milky Way, appear as a cloudy film. Nebulae in this sense denoted systems of stars. Another meaning concerned the matter of the primitive universe, understood as having been distributed in a thin homogeneous fluid. Although different from each other, both meanings contri- buted to the speculations that ultimately became known as nebular hypotheses. Kant’s natural history of the heavens. Among the most famous names in the history of Western philosophy, Immanuel Kant’s ranks at or near the very top. His philosophical contributions, which are treated in Chapter 14, derive from work done primarily during the last half of his adult life. As a young man he was interested in natural science. He studied the systems of both Wolff and Newton at the university in Konigsberg, where he later taught. As a young man of thirty—one, he wrote the Universal Natural History aml Theory oft/76 Hear/ms, published in 1755. It contained his ideas about cosmology, the theory of the heavens, and cosmogony, an account of the origin and development of the universe. In both enterprises Kant used Newton’s principles, which he invoked in the subtitle of his work, as a starting point for his rea— soning. But Kant went beyond what Newton was willing to consider. He suggested that there were systems of stars (systems of systems) that rotated around a central mass. Our Milky Way, he contended, was one such massive system whose orbital motion prevents it from collapsing into its center. According to Kant, nebulae were other “Milky Ways,” each presumably containing systems of stars with their planets. The cosmogony in the second part of the work utilized natural laws more than it did a Creator to explain how such massive systems had originated. Nebulous matter diffusely distributed in an infinite universe gradually coalesced into dense masses as a result of gravitational force, first into rings and then into spheres. Kant thought he could account for the rotational motion that commenced around the primitive cen— ters of gravitational force by introducing repulsive forces acting between particles of mass. This same process occurred at various levels, first in planets that ended up revolving around central suns, next in suns rotating around their own massive centers, and finally in other “Milky Ways” rotating around the center of the universe itself. Although he did not explain how an infinite universe could have a center, he imag— ined that the formation of “worlds without number and without end” had begun near this center and spread out as the order introduced by gravitational force gradually conquered the chaos of diffuse matter. He referred to the “mountains of millions of centuries” that it would take for the formation of worlds to reach perfection. While he conceded that God was the ultimate explanation for the existence of order that con- quered chaos, his interest was primarily in explaining how that order worked. Laplace’s nebular hypothesis and the solar system. Another cosmogony of the second half of the eighteenth century appeared in 1796. It was written by Pierre Laplace barely a decade after his dramatic demonstration that the solar system was , <Wrmzwmmwunmwmwwmmmwmwwuwwmm E E i THE EARTH AS A COSMIC BODY Was Newton Right About Hypotheses? I themselves to matters of fact alone. The NATURE of SCIENCE 189 N ewton’s famous claim,"l feign no hypotheses” (see Chapter 8), served as a justification for many in the late—eighteenth century to refuse to engage in speculation, as if natural philosophy should content itself only with facts.The prize competitions of numerous scientific societies from this time, for example, specified that acceptable answers should confine Natural science relies on careful empirical observation and experi— mentation, but it often also requires creative imagination to formulate theories that in turn suggest new ideas.As is evident in this section, even during a time when speculation was widely frowned on, leading natural philosophers willingly constructed hypotheses to explain how the cos— mos had come about. Newton’s claim may have been invoked by some in this time to justify their anti-hypothetical viewpoints, but in so doing they took his public statement out of context. As we have seen, Newton did speculate about numerous matters on many occasions. not running down. Laplace restricted his attention to the origin of the solar system rather than the entire universe, but its more limited context did nothing to dimin: ish the grandiose implications of his conclusions. By the time Laplace had formulated his hypothesis the astronomer William Herschel had already used powerful new telescopes to confirm the presence of hun— dreds of new nebulae in the heavens. They appeared as structureless masses of a finely distributed substance, some of which displayed apparent condensation in the center. Laplace inferred that they represented various stages in the formation of planetary systems and reasoned that our own solar system had originated from a Similar process. In his book, entitled An Exposition of the System of the World, he postulated a rotating, primitive nebulous solar fluid that contracted as a result of gravitational force into a central mass surrounded by smaller revolving masses. Laplace argued that the origin of our solar system from a rotating nebula explained why all the planets and known satellites revolved around the sun in the same direction and why they were all in planes only slightly inclined to each other. Newton had used this same coincidence of circumstances to atone that the solar system had originated from the direct intention of God. Laplace), too, believed in God, but he did not believe that God’s presence was required to supervise the work— ings of the cosmos. According to an account that originated in the middle of the nineteenth century, when Napoleon asked him where God appeared in his system of the world, Laplace replied: “Sire, I have no need of that hypothesis.” © The Earth as a Cosmic Body (3 It has been said that some of the natural philosophers of the eighteenth century wanted Newton’s physics without Newton’s God. More and more they preferred Leibniz’s God, who created laws that made the universe run by itself, to Newton’s repairman God. In 1692 Richard Bentley defended his friend Newton’s position 190 CHAPTER 9: NEWTONIANISM, THE EARTH, AND THE UNIVERSE against what he called deism, a term that has come to characterize the belief that God was necessary to create the physical and moral world orders, but not to super- intend them. The embrace of both Newton’s physics and deism in the second half of the eighteenth century by many French natural philosophers confirmed that it was indeed possible to separate Newton’s description of how the heavens worked from religious views about their origin and governance. Causal Theories of the Earth Buffered about by the impersonal forces of gravitational attraction, the Earth at the midpoint of the eighteenth century no longer enjoyed anything close to the exalted position it had once held in God’s Creation. The Earth was not exempt from the laws astronomers used to understand heavenly bodies. It was inevitable that the same attitude that led some natural philosophers to explain naturalistically how the heavens originated would lead others to consider how the Earth came to be as a result of the operations of natural laws. . To the average person the Bible was clear about how long God’s creative activrty had taken——seven days. Furthermore, the Bible provided clues about the duration of history. A seventeenth-century English scholar, Archbishop James Ussher, had used his extensive biblical knowledge of the genealogies of Adams lineage to determine the date of Adam’s creation. Ussher’s calculation of 4004 B.C. as the date of the creation of the universe confirmed the impression of most that the universe and the Earth were approximately six thousand years old. But as early as the seventeenth century natural philosophers had supplemented the biblical record with what became known as theories of the Earth—conjectures about the causal mam: God might have used. In the earliest of these theories of the Earth the physical causes and mechanisms identified did not challenge the Genesis chronology; on the contrary, the older theories of the Earth used the new science to support it. That would change in the eighteenth century. The Telliamed of Benoit de Maillet. Sometime between 1692 and 1718 Frances ambassador to Egypt, Benoit de Maillet (1656—1738), composed what he called “a new system on the diminution of the waters of the sea.” It was an attempt to explain what had caused the Earth and life to develop as they had. By the time the manuscript reached the public in 1748, de Maillet had been dead for ten years. He had certainly intended to see the work published during his lifetime, but unfortunate delays had frustrated his plan. De Maillet had traveled widely in the Mediterranean, taking with him an intense curiosity about the features of the Earth’s surface in the regions he visited. He did not limit his interest in the Mediterranean area to its geography. He mastered Arabic, read the histories of Arabic writers, and became familiar with historical landmarks. His travels exposed him to cultures whose understanding of history, including the history of the Earth, was very different from that of Christian France. He determined that he would incorporate this broader perspective into his new system. De Maillet’s grandfather had become convinced that the sea was diminishing, through observations he had made of the seashore near the familyhome. From his grand— father’s observations and from knowledge he acquired on his travels, he composed THE EARTH AS A COSMIC BODY 7211221772ch (which was de Maillet’s name spelled backward). De Maillet knew his man— uscript would test the limits of acceptability, so he tried at the outset to deflect criticism by attributing the views expressed in the book to a pagan foreigner. The subtitle declared that the work consisted of conversations between a French missionary and a philosopher from India named Telliamed about the formation of the Earth being due to the diminution of the sea. De Maillet utilized mechanical interactions of vortices together with his own observations to create a specifically non—Christian cosmogony. From the alleged Indian understanding of the Earth’s past the French missionary learned that the Earth was originally covered with water, whose currents carved out the mountains beneath its surface. The depths of the primitive seas gradually decreased, exposing the highest mountains, which immediately began to wear away. Eroded material from the shore settled onto the ocean floor as sedimentary rock, which, as the sea level continued to drop, was exposed as new mountains. As the process of diminution continued, more dry land emerged and on it, life began. Telliamed himself did not invoke the direct act of God to explain the successive appearances of animal life. He did not give details, but he maintained that various forms of aquatic animals had changed during the time the sea was gradually receding in accordance with natural process. Air above the seashore was so moist “that it must be considered an almost equal mixture of air and water,” breathable, for example, by flying fish. While escaping a predator or having been thrown onto the land by the waves, such fish found their features altered. “The little wings which they had under their belly, and which like their fins helped them to walk on the sea bottom, became feet and served them to walk on land.” Clearly such processes had taken a great deal of time, far longer than six thousand years. Telliamed in fact estimated from structures in ancient Carthage that the rate the sea level had dropped from earlier times to his day was three feet every thousand years. Using this rate he concluded that over two billion years had passed since the primi- tive waters had begun to recede. Humans themselves were over 500,000 years old! The public immediately saw through De Maillet’s tactic of camouflaging his ideas in a pagan philosophy. The reaction was outrage. But retribution could not be exacted on de Maillet, who was long dead. Another writer who speculated publicly that same year had no such refiage. From Natural History to Epoch: of Creation. Although Georges—Louis Leclerc (1707—1788) was born into aristocracy, the name by which he has become known to history—Buffon—was given him by King Louis XV of France in 1773 for what he had achieved during his lifetime. The king bestowed on him the title Comte de Buffon (based on the name of an estate he inherited from his mother when he was twenty—five), because of his extensive accomplishments as a natural philosopher. Buffon is remembered for his monumental Natural History, a multivolume work about the living world that even nonspecialists could understand. The first three volumes were published in 1749. In the first volume Buffon included a history of the Earth because, he said, it was “the history of nature in its most ample extent.” It became immediately clear that Buffon believed the Earth was extremely old; he announced that the more recent changes of the previous few thousand years were insignificant compared with those 191 192 CHAPTER 9: NEWTONIANISM, THE EARTH, AND THE UNIVERSE that occurred in the ages following the Creation. Because Buffon Viewed the Earth as just one of the planets, its history was tied to that of our solar system. Readers of the first volume of Buffon’s Natural History encountered an intriguing idea of how the Earth originated. Buffon explained What caused all of the planets to circle the sun in the same direction and within the same plane: a comet had struck the sun at an oblique angle, knocking off huge pieces of mass that settled into orbits at var— ious distances away and then began to cool. To justify his idea that a comet might have struck the sun he invoked the authority of “the great NeWton,” who had suggested that comets occasionally collided into the sun and refueled the sun’s power. Buffon concluded that as it cooled, the Earth became covered with water from the condens— ing atmosphere. Tidal motions of this primitive universal sea carved out mountains and valleys beneath the surface. He was reluctant to say how dry land came about as time passed, although he did make reference to likely violent revolutions. Some reviewers of Buffon’s work immediately noted that his explanation of the origin of the Earth was incompatible with that given in the book of Genesis. In the biblical account the Earth was created befin'e the sun, moon, and stars, which did not appear until the fourth day of creation. One reviewer, who regarded Buffon’s work as outlandish heresy, noted that it required a world “far older than Moses made it out to be.” Buffon had not said exactly how old, but the reviewer asked whether there really was any difference between Buffon’s View and that of authors who believed the world was eternal. Early in January of 1751 the faculty of theology at the Sorbonne in Paris notified Buffon of some fourteen propositions from the first three volumes of the Natural History that they regarded as reprehensible. Among these were Buffon’s speculations on the Earth’s fiery origin. In order to avoid censure, Buffon published a retraction in the fourth volume of his Natural History, which came out in 1753. It is clear from his continuing work that Buffon’s recantation was not genuine. He knew about recently published measurements of the heat in mines and hot springs that had been made in order to support the claim that the center of the Earth was hot. He also knew of Newton’s estimation that an iron sphere the size of the Earth would take more than 50,000 years to cool from red hot to the temperature of air. Buffon set out in the coming years to conduct his own experiments on the rates of cooling for various substances that make up the Earth. He published his results in a book on minerals in 1774 in which he inferred-he thought co nservatively——-that it had taken almost 75,000 years for the Earth to cool to its present temperature and over 33,000 years to cool to the point when organic life could begin. Four years later, in 1778, he brought his conclusions to widespread attention in a book that came to be regarded as a classic of French prose, the Epoc/as of Creation. By this time the so—called Age of Enlightenment, marked by the appearance of numer— ous ideas that challenged tradition, was in full sway (see Chapter 14). The threat of censure was no longer as immediate as it had been at mid-century, nor was Buffon the only one considering a prolonged age for the cosmos and the Earth. For all that, it was Buffon’s Epoc/ys that more than any other work introduced to the reading public the notion of an extended period of history, prior to human history, in which no life had existed. That is not to say that he was generally persuasive. Most people in Europe remained convinced that history coincided with human history. I, I, M h, ,V I, I , ,p I I My ‘ I 4 ,, , 1 I , K , , . , Wm VWWWWWW/WWWWW WWWaavaW, Wm, ,, ,,WWWWimwM/nrWWMWMLWMWWWWM’M7WWWWWMW/flrwwfiWWMGWWQWWMemW‘WmWM‘WMWkWMWwWfiW/W4 , THE EARTH AS A COSMIC BODY Buffon repeated his theory of the comet striking the sun, splitting off matter that congealed into hot fluid masses circling the sun. He closed this first epoch of creation, which took 2,936 years, at the point when the cooling process had produced a solid Earth that had lost its incandescence. In the next epoch the cooling Earth continued to contract, producing mountains and subterranean cavities over the next 30,000 years. The cooling now condensed the water vapor of the atmosphere in a third epoch, causingtorrential rains that covered all but the highest peaks with water. Over the next 20,000 years the first life, shellfish and plants, emerged and thrived in this primitive universal sea. Volcanic activity marked the fourth epoch, a relatively short time of about 7,000 years, opening routes for the water to recede into the Earth and for the appearance of dry land. Animal and plant life appeared on land near the cooler polar regions during the fifth epoch, which lasted another 5,000 years. During the sixth epoch, which lasted the same length of time as the fifth, life migrated toward the tropical regions and the continents began to separate. Some 70,000 years had passed by the dawn of the seventh and final epoch, in which humans appeared. A Scottish theory of the Earth. Seven years after Buffon’s Epoe/os of Creation appeared in France, James Hutton (1726—1797) communicated to the Royal Society of Scotland his ideas about the Earth’s past. This paper appeared in the Society’s Transactions in 1788, although a longer two—volume work appeared in 1795 under the title T/yeory of t/ae Eart/a, or an Investigation of the Laws Goren/able in t/ae Compo— sition, Dissolution anal Restoration of Lana’ upon the Globe. Hutton rented out the farmland he had inherited from his father and was able to retire to Edinburgh, where he compiled his reflections about the cause of the Earth’s development. Hutton’s understanding of the Earth began with two assumptions that colored his conclusions. First, he believed that the Earth had evidently been made for humankind. For example, a completely solid Earth would not be habitable because plant life requires soil, and humans depend on plant life. It was not accidental that natural forces had bro— ken up the surface of the hard, solid Earth so that it could support life. The second assumption was that the action of nature’s forces was not sudden and dramatic, but, as Hutton put it, “the operations of nature are equable and steady.” To wear down rock into soil, which was then carried by moving water to the sea, required an enormous amount of time. Hutton observed that “the course of nature cannot be limited by time.” Hutton asked what agency had caused strata of rock, especially those that appeared porous, to form at the bottom of the sea. After much consideration he rejected the possibility that they had been precipitated out of the water, embracing rather the idea that they could only have been fused by the action of subterranean heat. Hutton next asked how materials that collected at the bottom of the sea were raised above its sur— face and transformed into continents of solid land. Once again he concluded that this had not occurred by the receding waters of the sea, but by the same action that fused the strata—a deep subterranean heat. The continuous action of heat explained how and why the Earth’s surface had changed. The final section of his paper was where Hutton introduced his most unusual claim. He believed that the development of the Earth as he had described it was just a part of a larger, more general process. He thought that, by asking about the state of the Earth before the present land appeared above the surface of the waters, he could 193 194 CHAPTER 9: NEWTONIANISM, THE EARTH, AND THE UNIVERSE acquire some knowledge of the larger system that governed the world. He asked, for example, where the materials at the bottom of the sea, fused by heat into the strata he had identified, had come from. Some of the strata were composed of the fused remains of marine organisms. But where had they come from? Hutton could only conclude that there had been a phase of development prior to the one he had described. He even allowed that plant life had flourished on land during this phase; indeed, he asserted that cycles of decay and renovation consti— tuted nature’s means of sustaining plant and animal life according to a wisdom that had been in operation for indefinite successions of ages. Hutton may have been convinced that his scheme reinforced the central role life played in nature, but he convinced no more people than Buffon had that the age of the Earth went back indefinitely. Few found any comfort at all in the famous declaration that ended Hutton’s treatise: “The result, therefore, of our present enquiry is, that we find no vestige of a beginning—no prospect of an end.” Hutton differed from Buffon and de Maillet in his concern to demonstrate, through geological phenomena, the presence of a divine plan governing terrestrial processes. Other deists from his time argued that the time scale for geologlcal change could not be constrained by traditional interpretations of Genesis. Hutton agreed, because of the immensely slow pace at which he believed the forces of heat acted. But Hutton differed in his emphasis on the purpose behind the divine plan, one that accommodated the interests of plants and animals. The reason why there were volca‘ noes was to raise strata so that rivers could break rocks into soil for living organisms. Hutton’s work stood as an example of how deism compared with natural theology, in which the knowledge of nature supplied a basis for inferring God’s control over nature. For Hutton the prolonged time scale of Earth’s past revealed intelligent design. Mineralogy and Earth History As noted, the eighteenth—century theories of the Earth, with their emphasis on causal law, stood in a tradition that reached back into the seventeenth century. The search for the causal agency that had molded the Earth according to some grand natural law, however, was not the only means of access to an understanding of the Earth’s past. Paralleling these theories of the Earth was another approach, also with roots in the early modern period, in which the starting point was the composition of the Earth’s minerals. Minerals traditionally included four classes: “earths” (including rocks), met- als, salts, and sulfurs. Scholars gathered information about these various forms of solid materials found on Earth and then, in light of the data assembled, suggested how such diversity might have come about. Here the emphasis was on the description of the development of the Earth from its beginnings to the present in all its complexrty, without reference to a single unifying causal law. The German mineralogical tradition. This treatment of the history of the Earth was common in the German states, where the presence of rich deposits of ore drew primary attention to metals and accounted for the long-established mining-tradition in regions such as the Erz Mountains of Saxony. Mining officials wanted practical infor— mation about the location and properties of such valuable metals as lead, copper, and THE EARTH AS A COSMIC BODY silver. In an earlier period, state—appointed officials drew on individuals trained in the universities to oversee the acquisition of mineralogical knowledge, but in the eigh— teenth century they established separate technical schools for the purpose of training the officials they required. As a result, the German approach to mineralogy expanded beyond a primary interest in metals. German mineralogists of the eighteenth century began to subject rocks, previously regarded as mere conglomerations of individual minerals not worthy of study in their own right, to classification. They categorized rocks according to the effect heat had on them (the “dry way”), the purest rock being that whose mineral content remained unaltered even by intense heat. They began to gather more information than just the mineral content of the rocks; for example, they recorded such things as the elevation of rocks, their fossil content, their contour, and they listed impressions about the age and mode of origin of the rocks as well. For “earths” other than rocks mineralogists preferred the “wet way,” which could run in two directions. They could test the solubility in water of minerals with names like magnesia and baryte, or they could precipitate out the mineral contents of waters from hot springs and health spas. Chemists, who were also interested in earths, con— tributed their understanding of the interactions of earths with acids and bases. From numerous investigations experimenters differentiated a whole range of earths based on their solubility. Where the history of the Earth was’ concerned there was widespread acceptance among eighteenth—century mineralogists that the original ocean referred to in Genesis had been a thick gelatinous aqueous fluid made up of minerals in solution, and that rocks and most other solid minerals formed over time by a process of consolidation. There were various explanations of exactly how the consolidation of rocks occurred, but the end result was that rocks began to form and were laid down under the primal ocean. The oldest rocks, which formed the Earth’s core, were therefore almost the same age as the Earth itself. On top of these primal rocks came others, whose diverse properties reflected the variations in the contents of the primitive ocean waters at dif- ferent locations. Eventually the primitive waters diminished, at least in part due to evaporation, and the rocks were exposed to air. The variation in position that rocks now displayed as exposed land was a reflection of the effect that underwater motion— sometimes chaotic and sometimes calm—had on the pattern of their consolidation. Abraham Werner and the Freiberg School. The most influential figure in the history of geology from the late eighteenth century was Abraham Werner (1749—1817), who studied and later taught at the mining academy in Freiberg. Werner inherited the general ideas described in the preceding section fi‘om his predecessors and he openly acknowledged his debt to them. Although he published little, his powerful influence on his contemporaries and on a succeeding generation of scholars on the Continent and in Britain came from his considerable abilities as a teacher and from the new system he created. As a result, his influence extended well beyond Saxony and lasted into the third decade of the next century. Werner’s greatest contribution was to articulate that the period during which rocks were formed, rather than their mineralogy, was their most important feature. He gave 195 196 CHAPTER 9: NEWTONIANISM, THE EARTH, AND THE UNIVERSE to geology the historical entities that he called formations, which were rocks that had been produced in the same period. Werner focused on the variety of information mineralogists had begun to gather about rocks. Unlike his predecessors, Who relied only on mineral content when classifying rocks, his goal was to develop a systematic knowledge of all the data gathered about individual regions in order to determine when and how their rocks had been laid down. He called his new approach geognosy, based on the Greek word for abstract knowledge, to emphasize the intellectual rea‘ soning needed to put together the results of careful and widespread observation. In Werner’s account of the Earth’s history, the oldest rocks from the calm waters of the primeval ocean, many of which were crystalline but also included metals, consol— idated in successive individual formations to form a “primitive class.” Next came a small class of formations he called transition rocks, some of which had formed in tur— bulent waters. The third class of formations he called Stratified rocks; some of these resulted from mechanical pressure while others consolidated by chemical means. The final class of formations, called the recent class, came from eroded material deposited by moving water and from the extruded material of volcanoes. Contrary to a widespread impression, Werner did not appeal to sudden and dra— matic events to explain how the Earth had developed; rather, like Hutton, he held that the processes going on in the present were the same as those in the past. For example, he believed that the primeval ocean had gradually retreated over time and that there was evidence to indicate that the retreat had occasionally reversed itself. Werner pre— ferred not to endorse speculations about where the retreating water had gone. He believed it was sufficiently clear that the waters land retreated and that speculating about the cause Was relatively unimportant. However, late in his life he invoked the new knowledge that Water was composed of gases to suggest that primal waters had decomposed when forming the atmosphere. At the close of the eighteenth century Werner joined others who were willing to extend the history of the Earth far beyond the six thousand years inferred from a literal reading of the Old Testament. Once again, his preference was not to speculate about matters that did not easily lend themselves to precise determination. The most he would concede was an oblique reference to a time “when the waters, perhaps a million years ago, completely covered the earth.” As the century came to a close, then, there was ample indication that natural philosophers had begun to accept the Earth as a cosmic body whose past had been shaped by natural processes that they were responsible to identify and comprehend. (3 Suggestions for Reading Michael Crowe, T/Je Exnnrerrertriol Life Debate, 1750~Z900 (New York: Dover Publications, 1999). Thomas Hankins, Science and t/ye Enlzg/otenment (Cambridge: Cambridge University Press, 1985). Rachel Laudan, From Mineralology to Geology (Chicago: University of Chicago Press, 1994). Mary Terrall, The Man W/Jo Flattenen’ t/ae Eort/o: Moupertuis and the Sciences in the Enlightenment (Chicago: University of Chicago Press, 2006). CHAPTER 10. The Emergence of Chemical Sci‘enc,e'_ lthough chemical science was a product of the eighteenth century, refereiittes to “chymistrie” began to emerge early in the seventeenth century. In a 1605 trans— lation of a Latin work devoted to the maintenance of health, for example, the author referred to “those philosophers which have writtenof chymistrie.” This Vof course tells us nothing about What the term meant. It’soon becomes clear that in the seventeenth century there was no clean separation of chemistry from alchemy. By the 16505, for example, in a work with the wonderful title 'Mng—oszroAmonoer,' or the MngiooZZ—Astrologicnll Diviner Posed and Puzzled (1652), therewasxno doubt that at least some people viewed chemistry with the same suSpicionthat often plagued alchemy. Chemistry was _“a kinde of preestigious, covetous,‘ cheating magick.” Another author writing in the 16505 associated the sinful sons of Adam [with “the devil’s chymistry.” _ 5 ‘ . « - The existence of separate terms for chemistry and alchemysignals that the tv‘vo enterprises, however much related and however often confused With eachother, were not identical endeavors. “Chymistry” was the more i_ncluSive termehat is, chemists early on shared the alchemist’s search for the philosopher’s stone by Which - they could transmute one substance into another andfor a medicine that would produce immortality. But chemists also soughtother more mundane knowledge about how substances combined. ' i i ‘ l i I, © “Chymistry” in the Seventeenth Century (3 The four basic elements originally identified by Empedocles and adopted by [Plato and Aristotlee—earth, air, fire, and water—were still accepted by many natural philosophers of the seventeenth century. In addition to the'elements, hOVvever, there were other theories of matter. There was a tradition of identifying material 197 ...
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