Newton's Dark Secrets (2005)
Newton's Dark Secrets
TV Program Description
Original PBS Broadcast Date: November 15, 2005
He was the greatest scientist of his day, perhaps of all time. But while Isaac Newton was busy discovering the universal law of gravitation, he was also searching out hidden meanings in the Bible and pursuing the covert art of alchemy. In this program, NOVA explores the strange and complex mind of Isaac Newton.
Using docudrama scenes starring Scott Handy (Masterpiece Theatre's Henry VIII) as Newton, this film recreates the unique climate of late 17th-century England, where a newfound fascination with science and mathematics coexisted with extreme views on religious doctrine. Newton shared both obsessions.
The program also covers Newton's most important discoveries in mathematics, physics, and optics. And it follows a detailed recreation of one of Newton's little-known alchemical experiments, assembled by Bill Newman, Professor of History and Philosophy of Science at Indiana University, who spent years deciphering Newton's secret coded recipes (see Newton's Alchemy).
Most people know of Newton as the father of modern science, but his tireless genius knew no bounds. A devout Christian, his meticulous study of the scriptures led him to conclude that both Catholicism and the Anglican Church of England were based on dangerous heresies. Prudently, he kept these opinions to himself.
Oddly enough, he often kept his remarkable scientific discoveries to himself as well. While a student at Cambridge University in the 1660s, he had to return home to escape an outbreak of the plague. Working largely from this country setting, he invented the branch of mathematics we now call calculus and began asking fundamental questions about the nature of force and motion that would later lead him to the universal law of gravitation. At the time, he published nothing on these breakthroughs. (For more on Newton's extraordinary scientific accomplishments, see His Legacy.)
Returning to full-time studies at Cambridge after the epidemic, he worked his way up to an appointment as the prestigious Lucasian professor of mathematics, a position now held by the noted physicist Stephen Hawking. Newton's mathematics lectures were so notoriously difficult that few, if any, students attended them. He also continued his optical experiments, which showed that white light is a mixture of all the colors of the rainbow, rather than being a pure form of light as was generally believed at that time.
In 1936 a huge cache of Newton's papers turned up that revealed his lifelong passion for alchemy. Though today alchemy is classed with magic and pseudoscience, in the 17th century it was a respected form of natural inquiry that was methodically laying the foundation for modern chemistry.
But the crowning achievement of Newton's career was his Principia Mathematica, an astonishing book that uses concepts of mass, force, motion, and gravity to explain everything from falling apples to orbiting planets. The mammoth work was sparked by a simple question from Newton's friend Edmond Halley, discoverer of the periodic nature of the comet that bears his name. Halley merely wanted to know the shape of a planet's orbit around the sun (see Birth of a Masterpiece).
NOVA also delves into Newton's religious studies, which he pursued with his characteristic zeal for finding unseen connections. One fixation was dating the Apocalypse based on clues in the Bible. It was recently announced that, according to Newton, the date for all the turmoil predicted in the book of Revelation is in our own century: 2060.
Whether it was in physics, alchemy, or theology, Newton was ceaselessly "looking for ultimate answers to questions," says Indiana University historian Gale Christianson.
A Complicated Man
Is the Newton-and-the-apple story true? Does anybody really understand the Principia? Was Newton a nice guy? In this interview, Dr. Jed Buchwald, an historian of physics and professor of history at the California Institute of Technology, answers these and other provocative questions about the man many consider to be the greatest scientist who ever lived.
The real Newton
NOVA: Everybody has an image of Newton, the guy who got hit on the head with an apple and dreamed up the universal law of gravitation. Is there any truth to this?
Buchwald: I doubt that an apple is what stimulated him to get the idea. The story behind it, of course, is that he was lying in the garden there, and instead of thinking about girls, he was thinking about the moon and how it goes around the Earth and so on. And an apple falls, and the story goes that bang, he suddenly has the idea that the same thing that's making the apple fall is what's holding the moon in its orbit. Then he does a calculation to see whether the mathematical behavior, the acceleration, as it's known, of the moon as it orbits around the Earth would fit with the fall of the apple if you assume that it falls at a certain rate. In other words, he's already got the whole ball game in his hands. I don't believe it.
NOVA: So how do you see Newton? I mean, who was Isaac Newton?
Buchwald: Well, these were, of course, the very early years in which science itself was forming as a discipline. The idea of doing experiments, the idea of taking measurements and what you did with them afterwards, what a laboratory was and what you should do in one, and how you should put it all together with mathematics were really in many ways new. Not that there weren't elements long before that. You can go back to antiquity and find Ptolemy, the great astronomer, handling things mathematically and doing observations. But there were a lot of new things about Newton.
For instance, it's pretty clear that he had the most sophisticated way of handling data, at least that I know about, in the 17th and early 18th centuries. He treated data very much the way scientists much later treated data. To give you an example, if you're an astronomer and you observe the position of a star and you observe the position of a star again, you're going to get different numbers every time because people aren't perfect. Well, what do you do with all those different numbers? Nowadays, really since the end of the 18th century, you take what's called an average. You put them all together with this mathematical procedure.
But almost nobody did that until the middle of the 18th century except Newton. He was extremely sophisticated in the handling of data. This is a major part of the novelty and the difficulty of his science, because he puts that together with a deep and profound understanding of how to build a mathematical structure. Almost nobody at the time was able to penetrate deeply into what he had done there, in part because he never really talked about it. These are the kinds of things that he did but never really discussed. So the way I see it, he is the exemplar of a profoundly new way [of doing science]—mathematically based, grounded in the generation of laboratory data, and the handling of complex data in a very concerted way. You can recognize a lot of the present in Newton, and you can't in most other people in the 17th and early 18th centuries. So to me he represents in some ways the birth of the very ethos of quantitative science.
NOVA: You started to talk about calculus. For the uninitiated, what exactly is calculus and what does it allow one to do? And what was Newton trying to solve that brought him to invent the calculus?
Buchwald: Newton was interested in solving mathematical problems that had gripped people. This was a guy who adored computation of every kind. Among the things that you can see if you open his manuscripts, for instance, is there are places where you'll find he's calculated logarithms out to 50 places and things like that. Not because he needed it, but because he liked doing it. I mean, it was a pleasure to him to do that sort of thing. He was an unusual sort, obsessive, but gripped by the power and the beauty of sheer computation. I think that was a driving force behind what he did.
“Once he was onto something, he worked at it and worked at it and worked at it until he could solve it or until he had to give up.”
And when he hit a problem he couldn't solve, he bounced it off other related problems and saw relationships between them that other people had never seen before. So the mathematical structure really emerged in that sense within the boundaries of what were already intrinsically interesting mathematical problems. Not because he needed something to solve the orbits of the planets.
NOVA: But calculus has very practical uses today. In what way does it?
Buchwald: Well, calculus is about finding the behavior of continuously changing things. Like, for example, when a rock falls, its speed is continuously changing, and you may want to find out the distance that it's traveled or how fast it's going at a given point. The calculus is adapted to continuous change—not jumps, but continuous change—and that raises a lot of philosophical questions that people addressed as well. But it has practical application in the sense of being useful for the solution of problems of that sort.
Now, preeminently, problems of that sort are the problems of mechanics, and among the problems of mechanics are, of course, the motion of the planets. When Newton produced the Principia, he deployed a form of the calculus in order to figure out the relationships between the orbits of the planets, the forces that keep them in their orbits, and indeed what kind of paths they could use. In the absence of the calculus, these problems are, if not unsolvable, close to being unsolvable. So he needed that structure in order to produce the famous Newtonian mechanics itself.
NOVA: When he did his alchemy, was he doing it to gain knowledge for knowledge's sake? Or was there some driving quest to understand truth or whatever? Did he have an aim in this, do you think?
Buchwald: Well, he was a complicated man, and you can't reduce things to single motivations. Lots of things clearly motivated him. For instance, once he was onto something, he was gripped by it and he worked at it and worked at it and worked at it until he could solve it or until he had to give up. In other words, it was the quest to reach a solution, to break the problem, that gripped him. It's the same kind of thing that motivates scientists today in very much the same way, only he was maybe more extreme and successful than many.
NOVA: But when you say solve this thing, what is it?
Buchwald: Well, there were many different things. In the case of the mathematics, he wanted to solve the problems that were out there that other people had treated and that he saw relationships between. When he found that the shape of the sun in the prism wasn't what it should be, [he asked] why is that so? He was driven to figure this out, to probe it, to push, to monkey around, whether he was playing around with prisms in a laboratory or whether he was sitting there with his quill pen and his paper and trying to calculate. This was really the same kind of activity. It was a quest to solve whatever problem it was that he came upon in his voluminous and voracious reading, things that were floating in the air. Same in the alchemical laboratory. He was seeking for methods of transmutation, of course, and he thought he could make progress where other people hadn't. In the end he didn't, but he spent an awful lot of time trying.
NOVA: Were there connections between his scientific accomplishments, his work in early chemistry, and his work in religion? Or were these all separate endeavors?
Buchwald: No, no, I think they were connected but in complicated ways. I think that, first of all, they were connected at a certain level in the way he thought about how to handle information—how to deal with it, how to work with it. His techniques of working on these things were all the same. There was also an underlying belief that all of these things must be connected, because the world was, after all, created by God. God is not irrational. There had to be a logic underlying all of these things. That was a profound belief that he had, a belief derived from a deep-seated religious conviction. Now, there were plenty of others around, particularly by the 19th century, who didn't need that religious conviction to believe that a rational order underpins the universe. But Newton did.
Setting the standard
NOVA: Why is the publication of the Principia held to be such a crucial event?
Buchwald: Well, the Principia is objectively a work of profound mathematical insight. And I would argue that anybody in the late 17th century who was capable of reasoning at that level (and there weren't many but there were several) would have recognized the brilliance of what he had done, even though they might quarrel with the basis of the mechanics underlying it, as both [the Dutch mathematician Christiaan] Huygens and [the German mathematician and philosopher Gottfried] Leibniz, his two greatest contemporaries, did. Here he had put together the mechanics of the world with the most profound and advanced mathematics available.
“Except in the rarified world of general relativity, the Newtonian system still reigns.”
It set a standard and a structure that anybody choosing to work in that area subsequently had to meet. It was an almost impossible standard to meet, but it was nevertheless something that did set a structural standard. After, say, 1710 or 1715, you would no longer get people who would be taken profoundly seriously—that is, who would invent stories, so to speak, about the world—without attempting to bind it in some way to a mathematical structure that led to results that could be compared with observation. This was something that the Principia provided and that ever after was a desideratum, something that is necessary for scientists to work towards.
NOVA: Did many people even understand the Principia?
Buchwald: Very few people could understand what this thing was about, but a lot of people could see that there was something important in there. Even some really smart people couldn't figure out the novelty of what was being done in there. In particular Huygens and even Leibniz, when they first ran into this thing, didn't really understand what he was doing. Now, they would argue with him later on about other things in it, and eventually they did understand it, but very few people could.
You know, there weren't tens of thousands of students taking calculus at universities in those days. It was very hard to understand, and moreover, this was very arcane stuff. I mean, after all, what was the point here, right? What were you going to do with this stuff? It was purely abstract. Eventually it had some practical results, and Newton had some in mind eventually. But initially it was very abstract.
NOVA: What is Newton's legacy today? Why are we still interested in him 300 years later?
Buchwald: Well, I think it's reasonable to say that Newton both represents and, in fact, was the founding father in a certain sense of the form of experimental, quantitative science that has ever since become the way in which we do things. He's not the only one; there are many others as well. But I think the dimensions of his accomplishment are really in almost every respect unparalleled in all of these various aspects.
Now, you could find people who did magnificent things in other areas, and even areas that Newton worked in, like Huygens or Galileo. But I think that in terms of the influence that he had, the impact, the way in which it eventually changed the practice of science, both for good and some might say for bad as well, are a part of Newton's legacy. Certainly in England at the Royal Society and elsewhere as well, science did change very radically under Newton's tutelage.
Of course, since really the 1920s and 1930s, we have had an image of a certain basic divide in science—well, really in physics—between what we call the classical world and the quantum world. Interestingly enough, the classical world, if you ask physicists today, usually includes relativity, and the quantum, or non-classical world, is about the strange behavior of particles.
But it's also generally thought that there is a major divide between mechanics as done before Einstein and mechanics after relativity, after, say, 1905 or thereabouts. That divide is often expressed as being represented by the difference between the Newtonian world and the Einsteinian world. And there is some truth to that, that is, that Einstein's innovations do make many of the claims that you might have made in using the mechanics before Einstein incorrect.
“Was he a nice guy? No, he probably was not.”
On the other hand, it is also the case, as historians of relativity will tell you—especially general relativity, the theory of gravity—that one of the most important factors in what lead to the particular form of general relativity that Einstein produced was the necessity of figuring out how to get Newton's world out of it.
NOVA: That's not the way we usually think about it, I guess.
Buchwald: No. No, but what I mean is it was an essential requirement that by choosing certain specific values for all of the various parameters that went into the general relativistic, complicated equation, you had to be able to get the Newtonian system out. And in that sense, the Newtonian system, except in the rarified world of general relativity, which doesn't have that much of an effect on most things, the Newtonian system still reigns. (Although it is the case that we've become so accurate today with GPS systems that they must take account of general relativity—non-Newtonian effects—so our world today is in a fair number of effects quite realistically non-Newtonian.)
NOVA: Final question: Newton was not always a nice guy, I guess you could say. Can you tell me about that? What was he like?
Buchwald: Well, that's a very interesting question. Of course, it's trying for a historian to try and get behind that. There were all sorts of stories that would emerge later on about Newton. Was he a nice guy? No, he probably was not. He led a very self-confined, solitary existence. He didn't seem to care that much, at least in his youth, about other people. He certainly didn't, at least until the 1690s, have any significant relationships with anybody else.
A book written by a now deceased historian, Frank Manuel, tried to probe the psychology of Newton. [See A Portrait of Isaac Newton, Da Capo Press, 1990.] Manuel was convinced, maybe not incorrectly, that Newton's whole persona was formed when his father died before he was born and he was then brought up for three years by his mother. And his mother then married the Reverend Barnabus Smith. He was an older man, I believe in his 60s at the time, and Smith did not want the little boy around the house. So Newton had to stay back at Woolsthorpe Manor, taken care of by his grandmother, I believe, while his mother would see him relatively infrequently. Eventually, Barnabus Smith died and she came back.
But Manuel would argue that this had a very profound effect on the young Newton. It must have had some effect on him because, after all, he was a three-year-old boy when his mother vanished from his life all of a sudden. That cannot have had a good effect on him. And he was not an easy young guy, so the story goes, later on in life. But this is speculative. These psychological things are very difficult to know. But I think there's enough evidence to show that this was not, generally speaking, a man who at least until the 1690s you wanted to spend an evening drinking with. I think there's no doubt about that whatsoever—not that he didn't drink, because he did. But he could not have been very pleasant company on the whole.
by Albert Einstein
Editor's note: This article appeared in the Smithsonian Annual Report for 1927, the second centenary of Newton's death. It's somewhat dense, but then, what do you expect from the "greatest scientist who ever lived" talking about the accomplishments of the other "greatest scientist who ever lived?"
The 200th anniversary of the death of Newton falls at this time. One's thoughts cannot but turn to this shining spirit, who pointed out, as none before or after him did, the path of Western thought and research and practical construction. He was not only an inventor of genius in respect of particular guiding methods; he also showed a unique mastery of the empirical material known in his time, and he was marvelously inventive in special mathematical and physical demonstrations. For all these reasons he deserves our deep veneration. He is, however, a yet more significant figure than his own mastery makes him, since he was placed by fate at a turning point in the world's intellectual development. This is brought home vividly to us when we recall that before Newton there was no comprehensive system of physical causality which could in any way render the deeper characters of the world of concrete experience.
The great materialists of ancient Greek civilization had indeed postulated the reference of all material phenomena to a process of atomic movements controlled by rigid laws, without appealing to the will of living creatures as an independent cause. Descartes, in his own fashion, had revived this ultimate conception. But it remained a bold postulate, the problematic ideal of a school of philosophy. In the way of actual justification of our confidence in the existence of an entirely physical causality, virtually nothing had been achieved before Newton.
Newton's aim was to find an answer to the question: Does there exist a simple rule by which the motion of the heavenly bodies of our planetary system can be completely calculated, if the state of motion of all these bodies at a single moment is known? Kepler's empirical laws of the motion of the planets, based on Tycho Brahe's observations, were already enunciated, and demanded an interpretation.* These laws gave a complete answer to the question of how the planets moved round the sun (elliptical orbit, equal areas described by the radius vector in equal periods, relation between semi-major axis and period of revolution). But these rules do not satisfy the requirement of causality. The three rules are logically independent of one another, and show no sign of any interconnection. The third law cannot be extended numerically as it stands, from the sun to another central body; there is, for instance, no relation between a planet's period of revolution round the sun and the period of revolution of a moon round its planet.
But the principal thing is that these laws have reference to motion as a whole, and not to the question of how there is developed from one condition of motion of a system that which immediately follows it in time. They are, in our phraseology of today, integral laws and not differential laws.
It was, no doubt, especially impressive to learn that the cause of the movements of the heavenly bodies is identical with the force of gravity so familiar to us from everyday experience.
The differential law is the form which alone entirely satisfies the modern physicist's requirement of causality. The clear conception of the differential law is one of the greatest of Newton's intellectual achievements. What was needed was not only the idea but a formal mathematical method which was, indeed, extant in rudiment but had still to gain a systemic shape. This also Newton found in the differential and integral calculus. It is unnecessary to consider whether Leibniz arrived at these same mathematical methods independently of Newton or not; in any case, their development was a necessity for Newton, as they were required in order to give Newton the means of expressing his thought.
From Galileo to Newton
Galileo had already made a significant first step in the recognition of the law of motion. He discovered the law of inertia and the law of free falling in the Earth's field of gravitation: A mass (or, more accurately, a material point) uninfluenced by other masses moves uniformly in a straight line; the vertical velocity of a free body increases in the field of gravity in proportion to the time. It may seem to us today to be only a small step from Galileo's observations to Newton's laws of motion. But it has to be observed that the two propositions above, in the form in which they are given, relate to motion as a whole, while Newton's law of motion gives an answer to the question: How does the condition of motion of a point-mass change in an infinitely small period under the influence of an external force? Only after proceeding to consider the phenomenon during an infinitely short period (differential law) does Newton arrive at a formula which is applicable to all motions. He takes the conception of force from the already highly developed theory of statics. He is only able to connect force with acceleration by introducing the new conception of mass, which, indeed, is supported curiously enough by an apparent definition. Today we are so accustomed to forming conceptions which correspond to differential quotients that we can hardly realize any longer how great a capacity for abstraction was needed to pass across a double barrier to the general differential laws of motion, with the further need to evolve the conception of mass.
But this was still a long way from the causal comprehension of the phenomena of motion. For the motion was only determined by the equation of motion if the force was given. Newton had the idea, to which he was probably led by the laws of the planetary motions, that the force acting on a mass is determined by the position of all masses at a sufficiently small distance from the mass in question. Not until this connection was realized was a completely causal comprehension of the phenomena of motion obtained. How Newton, proceeding from Kepler's laws of the motion of planets, solved this problem for gravitation and so discovered the identity of the nature of gravity with the motive forces acting on the stars is common knowledge. It is only the combination of (Law of motion) + (Law of attraction) through which is constituted that wonderful thought-structure which enables the earlier and later conditions of a system to be calculated from the conditions ruling at one particular time, insofar as the phenomena occur under the sole influence of the forces of gravitation. The logical completeness of Newton's system of ideas lay in the fact that the sole causes of the acceleration of the masses of a system prove to be the masses themselves.
On the basis sketched Newton succeeded in explaining the motions of the planets, moons, comets, down to fine details as well as the ebb and flow of the tides and the precessional movement of the Earth—this last a deductive achievement of particular brilliance. It was, no doubt, especially impressive to learn that the cause of the movements of the heavenly bodies is identical with the force of gravity so familiar to us from everyday experience.
Significance of Newton's achievement
The significance, however, of Newton's achievement lay not only in its provision of a serviceable and logically satisfactory basis for mechanics proper; up to the end of the 19th century it formed the program of all theoretical research. All physical phenomena were to be referred to as masses subject to Newton's law of motion. Only the law of force had to be amplified and adapted to the type of phenomena which were being considered. Newton himself tried to apply the program in optics, on the hypothesis that light consisted of inert corpuscles. The optics of the undulatory theory also made use of Newton's law of motion, the law being applied to continuously diffused masses. The kinetic theory of heat rested solely on Newton's formulae of motion; and this theory not only prepared people's minds for recognition of the law of the conservation of energy, but also supplied a theory of gases confirmed in its smallest details, and a deepened conception of the nature of the second law of thermodynamics. The theory of electricity and magnetism also developed down to modern times entirely under the guidance of Newton's basic ideas (electric and magnetic substance, forces at a distance). Even Faraday and Maxwell's revolution in electrodynamics and optics, which was the first great advance in the fundamental principles of theoretical physics since Newton, was still achieved entirely under the guidance of Newton's ideas. Maxwell, Boltzmann, and Lord Kelvin never tired of trying again and again to reduce electromagnetic fields and their dynamical reciprocal action to mechanical processes occurring in continuously distributed hypothetical masses. But owing to the barrenness, or at least the unfruitfulness, of these efforts there gradually occurred, after the end of the 19th century, a revulsion in fundamental conceptions; theoretical physics outgrew Newton's framework, which had for nearly two centuries provided fixity and intellectual guidance for science.
Newton on its limitations
Newton's basic principles were so satisfying from a logical standpoint that the impulse to fresh departures could only come from the pressure of the facts of experience. Before I enter into this I must emphasize that Newton himself was better aware of the weak sides of his thought-structure than the succeeding generations of students. This fact has always excited my reverent admiration; I should like, therefore, to dwell a little on it.
1. Although everyone has remarked how Newton strove to represent his thought-system as necessarily subject to the confirmation of experience, and to introduce the minimum of conceptions not directly referable to matters of experience, he makes use of the conceptions of absolute space and absolute time. In our own day he has often been criticized for this. But it is in this very point that Newton is particularly consistent. He had recognized that the observable geometrical magnitudes (distances of material points from one another) and their change in process of time do not completely determine movements in a physical sense. He shows this in the famous bucket experiment. There is, therefore, in addition to masses and their distances, varying with time, something else, which determines what happens; this "something" he conceives as the relation to "absolute space." He recognizes that space must possess a sort of physical reality if his laws of motion are to have a meaning, a reality of the same sort as the material points and their distances. This clear recognition shows both Newton's wisdom and a weak side of his theory. For a logical construction of the theory would certainly be more satisfactory without this shadowy conception; only those objects (point-masses, distances) would then come into the laws whose relation to our perceptions is perfectly clear.
2. The introduction of direct instantaneously acting forces at a distance into the exposition of the effects of gravitation does not correspond to the character of most of the phenomena which are familiar to us in our daily experience. Newton meets this objection by pointing out that his law of reciprocal gravitation is not to be taken as an ultimate explanation, but as a rule induced from experience.
3. Newton's theory offered no explanation of the very remarkable fact that the weight and inertia of a body are determined by the same magnitude (the mass). The remarkable nature of this fact struck Newton also.
None of these three points can rank as a logical objection against the theory. They form, as it were, merely unsatisfied needs of the scientific spirit in its effort to penetrate the processes of nature by a complete and unified set of ideas.
The theory of the electromagnetic field
Newton's theory of motion, considered as a program for the whole field of theoretical physics, suffered its first shock from Maxwell's theory of electricity. It was found that the reciprocal action between bodies through electrical and magnetic bodies does not take place through instantaneously acting forces at a distance, but through processes which are transmitted with finite velocity through space. Alongside the point-mass and its movements there arose, in Faraday's conception, a new sort of physically real thing, the "field." It was first sought to conceive this, with the aid of mechanical modes of thought, as a mechanical condition (of movement or strain) of a hypothetical space-filling medium (the ether). When, however, in spite of the most obstinate efforts, this mechanical interpretation refused to work, students slowly accustomed themselves to the conception of the "electromagnetic field" as the ultimate irreducible foundation stone of physical reality. We owe to [Heinrich] Hertz the deliberate liberation of the conception of the field from all the scaffolding of the conceptions of mechanics, and to [Hendrik Antoon] Lorentz the liberation of the conception of the field from a material bearer; according to Lorentz the physical empty space (or ether) alone figured as bearer of the field; in Newton's mechanics, indeed, space had not been devoid of all physical functions. When this development had been completed, no one any longer believed in directly acting instantaneous forces at a distance, even in connection with gravitation, though a field theory for gravitation, for lack of sufficient known facts, was not unmistakably indicated. The development of the theory of the electromagnetic field also led, after Newton's hypothesis of action at a distance had been abandoned, to the attempt to find an electromagnetic explanation for Newton's law of motion, or to replace that law by a more accurate law based on the field theory. These efforts were not crowned with full success, but the mechanical basic conceptions ceased to be regarded as foundation stones of the physical conception of the universe.
The Maxwell-Lorentz theory led inevitably to the special theory of relativity, which, by destroying the conception of absolute simultaneity, negatived the existence of forces at a distance. Under this theory mass is not an unalterable magnitude, but a magnitude dependent on (and, indeed, identical with) the amount of energy. The theory also showed that Newton's law of motion can only be considered as a limiting law valid only for small velocities, and substituted for it a new law of motion, in which the velocity of light in a vacuum appears as the limiting velocity.
The general theory of relativity
The last step in the development of the program of the field theory was the general theory of relativity. Quantitatively it made little modification in Newton's theory, but qualitatively a deep-seated one. Inertia, gravitation, and the metrical behavior of bodies and clocks were reduced to the single quality of a field, and this field in turn was made dependent on the bodies (generalization of Newton's law of gravitation or of the corresponding field law, as formulated by Siméon Denis Poisson). Space and time were so divested, not of their reality, but of their causal absoluteness (absoluteness-influencing, that is, not -influenced), which Newton was compelled to attribute to them in order to be able to give expression to the laws then known. The generalized law of inertia takes over the role of Newton's law of motion. From this short characterization it will be clear how the elements of Newton's theory passed over into the general theory of relativity, the three defects above mentioned being at the same time overcome. It appears that within the framework of the general theory of relativity the law of motion can be deduced from the law of the field, which corresponds to Newton's law of force.
“The whole development of our ideas concerning natural phenomena may be conceived as an organic development of Newton’s thought.”
Newton's mechanics prepared the way for the theory of fields in a yet more formal sense. The application of Newton's mechanics to continuously distributed masses led necessarily to the discovery and application of partial differential equations, which in turn supplied the language in which alone the laws of the theory of fields could be expressed. In this formal connection also Newton's conception of the differential law forms the first decisive step to the subsequent development.
The whole development of our ideas concerning natural phenomena, which has been described above, may be conceived as an organic development of Newton's thought. But while the construction of the theory of fields was still actively in progress, the facts of heat radiation, spectra, radioactivity, and so on revealed a limit to the employment of the whole system of thought, which, in spite of gigantic successes in detail, seems to us today completely insurmountable. Many physicists maintain, not without weighty arguments, that in face of these facts not only the differential law but the law of causality itself—hitherto the ultimate basic postulate of all natural science—fails.
The very possibility of a spatio-temporal construction which can be clearly brought into consonance with physical experience is denied. That a mechanical system should permanently admit only discrete values of energy or discrete states—as experience, so to say, directly shows—seems at first hardly deducible from a theory of fields working with differential equations. The method of [Louis] De Broglie and [Erwin] Schrödinger, which has, in a certain sense, the character of a theory of fields, does deduce, on the basis of differential equations, from a sort of consideration of resonance the existence of purely discrete states and their transition into one another in amazing agreement with the facts of experience; but it has to dispense with a localization of the mass-particles and with strictly causal laws. Who would be so venturesome as to decide today the question whether causal law and differential law, these ultimate premises of Newton's treatment of nature, must definitely be abandoned?
*Everyone knows today what gigantic efforts were needed to discover these laws from the empirically ascertained orbits of the planets. But few reflect on the genius of the method by which Kepler ascertained the true orbits from the apparent ones, i.e., their directions as observed from the Earth.
Magic or Mainstream Science?
An interview on Newton's alchemy with historian Bill Newman
A Legitimate Pursuit
NOVA: Why are people surprised when they hear that Isaac Newton—the grand patriarch of physics—was an alchemist?
NEWMAN: Well, I think it's because alchemy has been portrayed as the epitome of irrationality and a sort of avaricious folly.
NOVA: Sinister, dark-robed sorcerers trying to turn lead into gold. Is that an accurate picture of alchemists in Newton's time?
NEWMAN: It's accurate for some alchemists. But we now know that most of the great minds of the period were involved in alchemy, including Robert Boyle, John Locke, Leibniz, any number of others.
NOVA: Given that so many great minds were interested in it, why was alchemy illegal?
NEWMAN: Well, first of all, it became legal during Newton's time. But why was it illegal? There's a long association, for good reasons, between alchemy and counterfeiting. It's quite likely, actually, that medieval and early modern rulers were consciously employing alchemists to debase their own coinage.
NOVA: But they didn't want other people doing it?
NEWMAN: [laughter] Yeah, right; exactly, exactly.
“He really thought that alchemy provided a sort of limitless power over nature.”
NOVA: So what were these "legitimate" alchemists in the 17th century trying to do?
NEWMAN: Alchemy really encompassed all chemical technology—everything ranging from the manufacture of pigments for paint to making artificial precious stones. It included the manufacture of so-called "chemical medicines." And, of course, it also included the attempt to make the "philosophers' stone."
NOVA: Tell me about the philosophers' stone. I think of it vaguely as some magical substance that could turn ordinary metals into gold.
NEWMAN: The philosophers' stone was thought to be an agent of universal transmutation. It also was viewed as a curative agent that could "cure" metals of their impurities and cure human beings of their illnesses. So it was a sort of universal panacea.
NOVA: Was Newton an alchemist because he wanted to make gold or find the key to immortality? Or was his alchemy just another part of his science—a way to gain knowledge about the material world?
NEWMAN: If you look at the experimental notebooks that he kept for about 30 years, it really is impossible to avoid the conclusion that he was trying to produce the philosophers' stone. But I don't think he was doing it to gain monetary wealth.
NOVA: Was it to gain an understanding of nature?
NEWMAN: And power over nature. Power over nature has always been a key element to alchemy.
Codes and Riddles
NOVA: Did alchemists think that they were going to discover powers they wanted to keep for themselves? Is that why alchemy is so veiled in secret codes?
NEWMAN: That's certainly part of the reason. You find alchemical treatises that claim that knowledge of the philosophers' stone has to be kept secret, because if it gets out to the world that a particular alchemist has it, he'll be strangled in his bed to extract the secret.
NOVA: It seems that Newton also wanted to hold tight to his secrets—he never published any of his alchemical work.
NEWMAN: I think that, like other alchemists, he thought that alchemy promised tremendous control over the natural world. It would allow you to transmute virtually anything into anything else, not just lead into gold. There are other things, too, that probably were in Newton's mind. For example, alchemists realized that if the philosophers' stone were real and it got out to the public, it would ruin the gold standard. [laughter]
“Alchemy was the ultimate riddle [which] provided a challenge to him that he just couldn’t resist.”
NOVA: I think what makes a lot of people think of alchemy as black magic is this bizarre language—phrases like "the Green Dragon" or the "menstrual blood of the sordid whore."
NOVA: It's mind-boggling to think of Newton writing those phrases.
NEWMAN: Well, this was the enigmatic language of alchemy. I mean "enigmatic" in a quite strict sense: it was a riddling language. The best way to look at these metaphors is in the light of riddles. So the "menstrual blood of the sordid whore" is decipherable. It means simply the metalline form of antimony. That is the "menstrual blood" that's extracted from the "sordid whore," which is the ore of antimony.
NOVA: It's a coded language.
NEWMAN: It is a code, and it's clear that the alchemists delighted in this code. It's almost a form of poetry. In fact, lots of alchemists wrote in the form of poetry, quite literally.
NOVA: Did all alchemists share the same code, use the same terminology?
NEWMAN: They shared lots of common elements, but it did vary from alchemist to alchemist. It's extremely tricky for Newton. He was reading alchemists over a period of time, ranging over perhaps a thousand years, and there was a lot of development in these treatises. But Newton generally thinks they're all saying the same thing, so that's a problem.
NOVA: Why did Newton spend so much time copying the writing of other alchemists?
NEWMAN: He wasn't for the most part just copying verbatim. What he was doing in many cases was weaving together extracts from different authors, trying to make sense out of them. I think alchemy was the ultimate riddle. Newton delighted in riddles, and this provided a challenge to him that he just couldn't resist.
Revealed Wisdom For a Chosen Few
NOVA: Why did Newton think that Greek myths somehow encoded alchemical recipes and a path to the philosophers' stone?
NEWMAN: That theory had been in existence for quite a long time. Newton's major source in alchemy, George Starkey, shared this theory. Michael Maier is a famous writer of the early 17th century who tried to decipher as much Greek mythology as he could get his hands on. So it was a common belief.
NOVA: Was it part of a broader belief in some sort of "revealed wisdom" about the natural world?
NEWMAN: Oh, yes. There's a tradition of scholarship that was very popular in the Renaissance called the prisca sapientia, the primal wisdom. It claimed that there was a secret wisdom that was first transmitted by an archetypical figure—say, for example, Moses—and then passed down through a line of successors, usually including Pythagoras, Plato, and so forth, and that this wisdom was really the ultimate tool for understanding the universe. Newton clearly believed that.
NOVA: Did Newton view himself as one of these chosen few, one of the people ordained to receive this wisdom?
NEWMAN: I suspect he did, yes. I don't think he would have admitted it publicly, but one of his pastimes was concocting alchemical pseudonyms for himself. And one of these pseudonyms was Jehovah Sanctus Unus—that is, Jehovah, the Holy One.
NOVA: That's how Newton described himself?!
“It’s really a gigantic jigsaw puzzle, and we’re only at the beginning of having solved it.”
NOVA: Did Newton think that he made progress in developing the philosophers' stone?
NEWMAN: Yes, I think that's quite clear. If you look at his manuscripts, there are stages of development that you can isolate. In his experimental notebooks, there are entries where he says "I found the caduceus of Mercury today" and this sort of thing that reflect real discoveries that he's made in the laboratory.
Newton Under Wraps
NOVA: After Newton's death, why did none of his writings on alchemy come to light? Certainly people going through his papers came across this writing. Was it viewed as not worthy of him?
NEWMAN: Oh, yeah. There's no question that they were considered to be borderline scandalous. Newton died in 1727. By that time you're well into the Enlightenment, and alchemy had become the domain of dunces; it was associated with all sorts of useless medieval knowledge. So the fact that Newton had been a serious student of this obsolete and idiotic field was really problematic.
NOVA: Do you think that today we should think less of Newton, knowing how deeply devoted he was to alchemy?
NEWMAN: No. On the contrary, I think that this opens up a side of Newton that makes him a much more fascinating figure. And I think also the fact that so many of these very, very seminal figures in the Scientific Revolution were heavily involved in alchemy opens up a new historiographical area that really promises to throw quite a different light on the whole period.
NOVA: It opens our eyes to the incredibly wide range of Newton's intellectual pursuits.
NEWMAN: Yeah, it's very important to see the full breadth of Newton's inquiries. And the dreams that were embodied in his alchemical pursuits explain to some degree how and why he was such a driven man. I think he really thought that alchemy provided a sort of limitless power over nature.
NOVA: And even though he recognized that he hadn't solved all the problems in alchemy, he truly felt that he had made strides.
NEWMAN: Well, of course, he's famous for having said that he felt as though he were only a boy on a seashore, having picked up a pretty shell, and that there were many, many other shells remaining to be discovered on the edge of this vast sea. That's what he said about his scientific endeavor as a whole, not just his alchemy.
NOVA: You've said that Newton's alchemy is still a great unsolved mystery. Why?
NEWMAN: In part because his experimental notebooks are so cryptic. These experimental notebooks pick up in 1678, and there is a story that there was a fire in Newton's laboratory immediately before that. So it's likely that we would have more materials if they hadn't been destroyed in this conflagration. Also, Newton doesn't bother to explain his terminology; being Newton, he expects to know his terminology.
And the terminology is very perplexing. He uses standard alchemical decknamen—cover-names like the Green Lion and the Babylonian Dragon, and so forth—but he seems to be using them in ways that don't correspond to how his immediate sources used them. So we have to carry out a huge combined effort, both in our laboratory and in studying the texts, to determine what these substances were.
Beyond that, Newton doesn't tell us why he's doing the experiments. He just says, "I did this and that, and I produced a volatile substance here," and so forth. He doesn't say the purpose of the experiment! So all of this has to be inferred and put together. It's really a gigantic jigsaw puzzle, and we're only at the beginning of having solved it.
NOVA: Wow. Do you enjoy actually getting into the lab and trying to reproduce what he might have been doing with his crucible?
NEWMAN: Oh, absolutely. And in many cases, you can reproduce the products very clearly. It's satisfying, but it's a heck of a lot of work. [laughter]
NOVA: As you continue studying the manuscripts and replicating his experiments, what do you hope to find?
NEWMAN: Well, there are a number of different things. One thing I'm trying to do is determine the chronology of the different manuscripts, so that we can say exactly how his ideas developed over time. Like I said, it's a gigantic jigsaw puzzle. I would just like to be able to put all the pieces together and see what he was really trying to do, what his goals were, and how this fit with his natural philosophy.
NOVA: And if you succeed in making the philosophers' stone, you'll let us know?
NEWMAN: [laughter] If I succeed, I'll disappear.
Sir Isaac Newton's accomplishments border on the uncanny, as does his image in the world of science. As the historian Mordechai Feingold has written, "With time, the historical Newton receded into the background, overshadowed by the very legacy he helped create. Newton thus metamorphosed into science personified." So what is that legacy? What were those accomplishments? Here, familiarize yourself with Newton's greatest contributions.—Peter Tyson
Invented the reflecting telescope
The standard telescope of Newton's time, the refracting telescope, was not ideal. Its glass lenses focused the different colors inherent in light at different distances. This resulted, at the edges of any bright objects seen through the telescope, in colored fringes that rendered those objects slightly out of focus. Newton solved the "chromatic aberration" problem by using mirrors instead of lenses. His original reflecting telescope, which he built himself in 1668, was just six inches long. This modest device not only eliminated the colored fringes but magnified whatever it focused on by 40 times, which, as Newton noted at the time, "is more than any 6 foote Tube can do." After presenting his scope to the Royal Society, the then-unknown Newton was proposed for membership; he later served as its president for 24 years, until his death in 1727.
Proposed new theory of light and color
Not long after he donated his telescope to the Royal Society, Newton delivered a paper to that august body about his novel theory of light and colors. Using prisms and his usual very exacting experimental technique, Newton had discovered that sunlight is comprised of all the colors of the rainbow, which could not only be separated but recombined into white light. "[T]he most surprising and wonderful composition was that of Whiteness," he wrote. "I have often with Admiration beheld that all the Colours of the Prisme being made to converge, and thereby to be again mixed ... reproduced light, intirely [sic] and perfectly white." Though he made his experiments on light as early as 1666, when he was only 24 years old, he didn't publish his classic Opticks, which summarized his findings on light and color, until 1704.
When Newton began to muse on the problem of the motion of the planets and what kept them in their orbits around the sun, he realized that the mathematics of the day weren't sufficient to the task. Properties such as direction and speed, by their very nature, were in a continuous state of flux, constantly changing with time and exhibiting varying rates of change. So he invented a new branch of mathematics, which he called the fluxions (later known as calculus). Calculus allowed him to draw tangents to curves, determine the lengths of curves, and solve other problems that classical geometry could not help him solve. Interestingly, Newton's masterwork, the Principia, doesn't include the calculus in the form that he'd invented years before, simply because he hadn't yet published anything about it. But he did combine related methods with a very high level of classical geometry, making no attempt to simplify it for his readers. The reason was, he said, "to avoid being baited by little Smatterers in Mathematicks."
Developed three laws of motion
Newton's Principia is difficult to comprehend on two levels, even for experts: in its original form, it is written in Latin, and it uses very challenging mathematics. Yet one thing that comes out very simply and very clearly to all is his three laws of motion:
Law of inertia: Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it.
Law of acceleration: Force is equal to the change in momentum (mV) per change in time. For a constant mass, force equals mass times acceleration, F = ma.
Law of action and reaction: For every action, there is an equal and opposite reaction.
To these Newton added, in the Principia, two general principles of space and time, many careful explanations, and much else besides. All of this went into his classic explanation of how the universe works, otherwise known as Newtonian mechanics. (Mechanics developed into a branch of physical science that deals with energy and forces and their effect on bodies.).
Newton's first and second laws of motion, in Latin, as they appear in the original 1687 edition of the Principia
Devised law of universal gravitation
Newton said shortly before his death that it was seeing an apple fall in his mother's garden that set him thinking "that the power of gravity ... was not limited to a certain distance from the earth but that this power must extend much farther than was usually thought. Why not as high as the moon ... and if so that must influence her motion and perhaps retain her in her orbit." This brainstorm (which some scholars suspect Newton may have invented late in life) ultimately led to his law of universal gravitation. The law says that all particles of matter in the universe attract every other particle, that gravitational attraction is a property of all matter. The law explained many things, from the orbits of the planets around the sun to the influence of the moon and sun on the tides. And it held sway as the accepted description of terrestrial and celestial mechanics for almost 200 years—until Einstein came along and rocked the boat with relativity.
As an old man Newton claimed the idea of universal gravitation came to him while watching an apple fall in the garden of his mother's house at Woolsthorpe (above, as it appears today).
Advanced early modern chemistry
Newton spent untold hours of his life practicing alchemy. Like other alchemists, he sought to turn base metals into gold, find a universal cure for disease, and secure the elixir of life, which promised perpetual youth and eternal life. In his garden shed outside his rooms at Trinity College, Cambridge, in the midst of phials and furnaces, mortars and pestles, Newton pored over ancient texts and performed endless experiments. Yet while he never found what he and other alchemists sought, and while he only published one short paper that grew out of his alchemical experiments (a two-page speculation on acids), his work was not for naught. As the historian Jed Buchwald has said, "As historians have shown in the last several decades, there was a much more profound element to the practice of alchemy which really makes it deserving of being called early modern chemistry." Through his meticulous efforts, Newton greatly furthered the practice and techniques of chemical science.
Became father of modern science
Newton essentially invented many elements of the modern scientific method. His paper on the properties of light that he presented to the Royal Society in the early 1670s shows all the hallmarks of the method he would use throughout his long life: conducting experiments and taking very careful notes on the results; making measurements; conducting further experiments that grew out of the initial ones; formulating a theory, then creating yet further experiments to test it; and finally, painstakingly describing the entire process so that other scientists could replicate every step of the way. This method governs how all science is conducted today. Newton once famously said, "If I have seen further it is by standing on the shoulders of Giants." Many scientists today would argue that the greatest Giant of all in the world of science was Isaac Newton himself.
Newton's Dark Secrets
PBS Airdate: November 15, 2005
Go to the companion Web site
NARRATOR: In 1936, a huge collection of scientific documents and personal papers was put up for auction at Sotheby's in London. These papers had never been seen by the public, and a large number of them were bought by the famous British economist John Maynard Keynes. Many were written in secret code, and for six years, Keynes struggled to decipher them.
He hoped they would reveal the private thoughts of the man who invented a new branch of math, called calculus; figured out the composition of light; and gave us the laws of gravity and motion, which govern the universe; the man who is considered the founder of modern science, Sir Isaac Newton.
GALE CHRISTIANSON (Author, Isaac Newton): Newton ushered in an age, the Newtonian age, and it was premised on the concept that everything, virtually, in the universe was amenable to scientific understanding.
WALTER LEWIN (Massachusetts Institute of Technology): Newton's work has a beauty and a simplicity and an elegance that makes it the greatest work of science ever done.
NARRATOR: But what Keynes found shattered his image of Isaac Newton. For, in these manuscripts, Keynes discovered an Isaac Newton unknown to the rest of the world, an Isaac Newton who seemed obsessed with religion and devoted to the occult.
STEPHEN SNOBELEN (University of King's College): He is known, today, as a sort of a high priest of the Age of Reason, but this is a misconstruction of Newton.
SIMON SCHAFFER (University of Cambridge): The modern interpretation of Newton is about as far as could possibly be from what Newton himself thought.
PAMELA SMITH (Columbia University): On the one hand, we can recognize him as a scientist, but on the other hand, he's pursuing an activity which we now label as a pseudoscience.
NARRATOR: Now scientists and historians are trying to reconcile the Isaac Newton they thought they knew with the Isaac Newton they're discovering in his private papers.
JAMES FORCE (University of Kentucky): Our project now must be to see Newton the way that Newton was, rather than trying to see Newton the way we want him to be.
NARRATOR: What are these mysterious documents revealing about one of the greatest scientists ever? Newton's Dark Secrets right now on NOVA.
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Major funding for NOVA is provided by the Howard Hughes Medical Institute, serving society through biomedical research and science education: HHMI.
Major funding for Newton's Dark Secrets is provided by the National Science Foundation, America's investment in the future.
Additional funding is provided by American Playhouse.
Major funding for NOVA is also provided by the Corporation for Public Broadcasting, and by PBS viewers like you. Thank you.
NARRATOR: In a library in Jerusalem lies an intensely curious document. It was written about 300 years ago, and only a handful of scholars have ever examined it. The author was arguably the most important scientist of all time, a genius who uncovered the laws of physics that govern the entire cosmos, Sir Isaac Newton.
The subject? Newton's calculation of the date the Bible said the world as we know it would end in the Battle of Armageddon: the year 2060.
STEPHEN SNOBELEN: If this calculation were correct, then we are close to the, the time of the end. That's exactly what this sort of calculation would point to.
NARRATOR: When this document came to public attention recently, it was headline news. But why was Isaac Newton making this dire prediction?
JAMES FORCE: We find it surprising that Newton sounds like a televangelist talking about the end of time. We only find it shocking because we've made Newton something that he's not. We've made Newton in a rationalist, enlightened image. That's just not Newton.
STEPHEN SNOBELEN: What these manuscripts reveal is a very different Newton than most people conceive of. This is a, a Newton who is not a cold, calculating scientist. This is revealing Newton in all his glory—warts and all, if you will.
NARRATOR: So who was the real Isaac Newton?
On a small farm in rural England, called Woolsthorpe, the conflicted life of Isaac Newton began, in 1642. That same year, the astronomer Galileo had died, and his work was still sending shockwaves through Europe.
Galileo had risked his freedom by challenging the ancient belief, held by the Catholic Church, that the sun moved around the Earth. Based not on faith, but observation, he confirmed the Earth was just one of several planets orbiting the sun.
It was the dawn of the scientific revolution, an age when science and reason would redefine the world.
GEORGE SMITH (Dibner Institute): There was a sense of a whole new era. The very idea of having the empirical world answer our questions, that idea was taking hold in a way that had almost never done so before.
NARRATOR: And from a young age, Newton was gripped by this new outlook. As a boy, he pored over a book called The Mysteries of Nature and Art, a manual for building mechanical contraptions and investigating the natural world.
GALE CHRISTIANSON: He was preoccupied by the things that preoccupy physicists—by time and motion—so he made windmills; he made little boats. He flew kites that supposedly "affrighted" the locals; he tied candles to them, and they were put up, and they thought that they were comets.
NARRATOR: But from the start, there was another side of Isaac Newton. His father died before he was born, and when he was just three years old, his mother remarried and moved away, leaving young Isaac behind with his grandparents. Newton later confessed to such rage that he wanted to burn his mother and stepfather in their house.
And by the time he left home for Cambridge University, Newton had lived through two decades of violent political and social turmoil: a bloody civil war, the beheading of the king, and the restoration of the monarchy under Charles II in 1660.
At Cambridge, Newton buried himself in his studies.
SIR ISAAC NEWTON (Dramatization): Truth is the offspring of silence and unbroken meditation.
GALE CHRISTIANSON: He didn't go anywhere. I mean, he rarely traveled. He never went to the Continent. He was that insular. I mean, he stayed in his rooms. He worked seven days a week, 18 hours a day, and he pushed himself, drove himself. He had a library of his own that had about 1,600 or 1,800 volumes, but it was very much a world that came to him through printed matter or through manuscripts from others.
NARRATOR: The decadent atmosphere of Cambridge was something the reclusive young Newton wanted no part of.
ROB ILIFFE (Imperial College London): It was a time—particularly after the restoration of Charles II—it was a time of great fun and frolicking. And I think Newton would have been dismayed by many of the antics of his fellow students: drinking, going after bad young women in local villages.
NARRATOR: To resist temptation, Newton drew up a plan that he'd stick to for the rest of his life.
SIR ISAAC NEWTON (Dramatization): The way to chastity is not to struggle directly with incontinent thoughts but to avert ye thoughts by some employment, or by reading, or meditating on other things, or by converse. For he that's always thinking of chastity will be always thinking of women.
ROB ILIFFE: He's a very silent, thoughtful young man who, I suppose, looks as though he's utterly tedious from the outside. There's no evidence, I think, that anyone liked him at all, apart from his friend John Wickins.
NARRATOR: John Wickins was another Cambridge student. He and Newton became roommates after both grew unhappy living with students who put pleasure before work.
ROB ILIFFE: They have a very peculiar relationship because Wickins is somebody who is of a higher status than Newton at Trinity and seems to have become Newton's amanuensis, i.e., his secretary, over the following 20 years. But they must have been very close. They lived in the same rooms for 20 years.
NARRATOR: As a student, Newton devoured the latest scientific ideas.
It was widely accepted by this time that the planets orbit the sun. But now the question was, "How did the planets move? What held them in their orbits?"
The most popular theory came from the French philosopher Rene Descartes, who thought of the universe as a giant machine, like a clock. Descartes said everything, even the orbits of planets, could be explained simply as the physical interactions of parts of this machine. But Newton had trouble accepting this view of nature.
JED BUCHWALD (California Institute of Technology): Newton's a very smart guy, and he became convinced that the only types of statements that are acceptable are ones which you could, to put it bluntly, test in the laboratory.
NARRATOR: But just as Newton was probing the limits of Descartes, the plague struck England. Thousands died every week. The university closed, and Newton returned home to avoid infection. And it was here, in the apple orchard just outside the family home, that the legend of Isaac Newton was born.
JED BUCHWALD: The story, of course, is that he's lying in the garden there—and instead of thinking about girls, he's thinking about the moon and how it goes around the Earth and so on—and an apple falls. And the story goes that bang, he suddenly has the idea that the same thing that's making the apple fall is what's holding the moon in its orbit.
NARRATOR: Newton told this tale himself in his old age, claiming that with the fall of that apple, he realized that what held the planets in orbit was not a physical mechanism like Descartes' clockwork, but an invisible force he called "gravity."
And he was convinced that the force pulling apples down to Earth and keeping the moon in orbit around the Earth were one and the same.
He stayed up late in the evening, calculating the strength of that force by the light of the fire. But when the numbers didn't quite work out, he put the idea aside. Or so the fable goes.
JED BUCHWALD: I doubt that an apple was what stimulated him to get the idea.
MORDECHAI FEINGOLD (California Institute of Technology): It's almost certainly an apocryphal story.
WALTER LEWIN: Yeah, I don't think it is even known whether it ever happened.
SIMON SCHAEFER (University of Cambridge): I'm extremely skeptical about the role of fruit in Newton's life.
NARRATOR: But there is no doubt that the motion of objects like apples and the moon captivated Newton at this time.
The Italian scientist Galileo had proved, in a famous experiment on motion, that all objects falling to Earth pick up speed, or accelerate downwards, at the same rate, regardless of their mass. And finding the average speed of a falling object was a straightforward process.
For example, if you want to find the average speed of an apple falling from a tree, all you have to do is divide the distance the apple travels by the time it takes the apple to fall. But Newton was not satisfied with the average. What would be the speed of an apple, which is constantly accelerating, at every point along the way? What would the apple's velocity be halfway to the ground?
To find out, you can measure the apple's average speed over smaller and smaller periods of time. The shorter the time interval, the closer you get to knowing the apple's speed at that moment. But to find its precise speed at a single instant, you have to reduce that time interval as close to zero as you can.
WALTER LEWIN: Newton invented a way to make that time interval infinitesimally small. What is infinitesimally small? That is smaller than any number that you can think of. It's not zero, but it is smaller than any number than you can think of.
NARRATOR: For the first time, it was possible to calculate quantities that are constantly changing, like the speed of a falling apple at any particular moment, or how a planet's position changes over time.
With this technique, Newton invented an entirely new branch of math, called "calculus."
WALTER LEWIN: And that changed all science, of course. The whole way of looking at the world changed because of calculus, yeah.
PETER GALISON (Harvard University): Calculus was a quantitative understanding of the way things change, not just velocity, but in physics, in chemistry, even in populations. How fast is a population changing over time? This mathematical framework becomes the language in which modern science is formulated.
NARRATOR: Today, calculus shows up everywhere, from analyzing the stock market to modeling global climate change.
GALE CHRISTIANSON: By the time he was 22 years of age, working on the calculus at Woolsthorpe, he was the greatest mathematician the world had ever seen, and yet no one knew. Only Newton knew, and it was his secret.
JED BUCHWALD: This was a guy who adored computation of every kind. Among the things that you can see if you open his manuscripts, for instance, is...there are places where you'll find he's calculated logarithms out to 50 places and things like that—not because he needed it, but because he liked doing it. I mean, it was a pleasure to him to do that sort of thing.
NARRATOR: And if that weren't enough, Newton overturned accepted wisdom about how colors are produced, performing an experiment on himself with a large needle, or bodkin.
SIR ISAAC NEWTON (Dramatization): I took a bodkin and put it between my eye and the bone as near to the backside of my eye as I could, and pressing my eye with the end of it so as to make the curvature in my eye, there appeared several white, dark and colored circles.
NARRATOR: Fortunately, Newton found a safer way to investigate light and color using a prism.
From Aristotle to Descartes, scientists thought sunlight, or white light, was pure. Colors were produced by physically modifying white light, which they believed passing it through a prism did.
But Newton decided to see for himself. Sending sunlight through a prism, he produced the spectrum of colors. And then he went one step further: he sent the red ray of light through a second prism. Instead of making a new color, it remained red.
Newton concluded white light is not pure, but a combination of all the colors of the rainbow.
JED BUCHWALD: He thought of the prism actually as a separator of the objects that are all in the original light. This was very hard for almost everybody to swallow because it meant that when you're looking at white light, you're looking at something which has all the colors already in it. This seemed completely counterintuitive, and indeed, frankly, it's counterintuitive to most people today.
NARRATOR: Only 25 years old, Newton had made some of the most stunning breakthroughs in the history of science, but he kept them almost entirely to himself, just as he had done with calculus. After the plague subsided, he returned to Cambridge where he worked his way up to an appointment as the Lucasian Professor of Mathematics, the position held by Stephen Hawking today.
Newton became known for his prematurely white hair and for his longwinded lectures on light.
SIR ISAAC NEWTON (Dramatization): That belongs to refractions, because it be found in there a demonstration on a certain physical hypothesis not well established. I judge it will not be unacceptable if I bring the principles of science to more strict examination.
NARRATOR: The introverted Newton had little time for students and they had little interest in him. Years later, one of Newton's laboratory assistants would recall...
SIR ISAAC NEWTON'S LABORATORY ASSISTANT (Dramatization): So few went to him—and fewer that understood him—that oftentimes he did, in a manner, for want of hearers, read to the walls.
NARRATOR: But Newton's study of light was about to start a revolution. Fifty years earlier, Galileo had built one of the first telescopes. It used glass lenses to gather light from distant objects and focus it for the observer. But this kind of telescope had a problem. Its lenses produced fringes of color around the edges of the objects being observed.
PETER GALISON: And that meant objects you looked at always had this chromatic aberration, this...They always looked colored even when they...the original object wasn't. And Newton began, on the side, to make some things with his own hands. And he designed a remarkably and radically different kind of telescope from anything that had been built before.
NARRATOR: Newton realized that the edges of a lens behave like a prism, breaking white light into different colors as it passes through. So he abandoned lenses and substituted a mirror to gather and focus light from distant objects. And because the light never passed through a lens, it was free of color distortion. Newton's telescope was only six inches long, but Newton bragged that it could...
SIR ISAAC NEWTON (Dramatization): ...magnify by about 40 times in diameter, which is more than any six-foot tube can do. I've seen with it Jupiter—distinctly round—and his satellites.
PETER GALISON: It was an instrument that has left its impact on astronomy ever since. Our huge telescopes of today are built on this model. They're gigantic versions of this tiny little thing. These are the telescopes that sit on the top of the great mountain peaks. These are the telescopes that we launch into space to peer into the deepest parts of the visible universe.
NARRATOR: Newton regarded his invention as just a toy, but a colleague took it to London, where it was shown off to King Charles II.
PETER GALISON: The effect that it had on Newton's contemporaries was immediate and dramatic. It brought Newton onto the world stage of science, and Newton became an overnight sensation.
NARRATOR: Newton was elected a member of the Royal Society, a group of leading scientists in London. Most of them were awed by the whiz kid from Cambridge. And Newton was so delighted that he promised to send the Royal Society a paper he had written on his discovery that white light is made up of different colors.
But members of the Royal Society had no idea that Newton was studying something far more mysterious than light by this time. His private notebooks reveal that the same year he became a professor at Cambridge, he bought two furnaces, an assortment of chemicals, and a strange set of books. Isaac Newton had become an alchemist.
Alchemy is an ancient and secret practice with roots in the Middle East. By carrying out lengthy and complex chemical procedures, alchemists tried to produce a magical substance called the Philosopher's Stone. The Philosopher's Stone was so potent that even a small quantity was said to perform miracles: curing ailments, conferring immortality, and transforming ordinary metals like lead into pure gold.
PAMELA SMITH: In the 16th and 17th centuries, there were many, many people who came to courts in Europe and claimed that they possessed the Philosopher's Stone, and they were employed by nobles and princes throughout Europe to make gold.
BILL NEWMAN (Indiana University): In some instances, it was immensely profitable. You could milk a duke or prince of a substantial amount of money, no question. But if you got caught, it was extremely dangerous. We know that one of the customary punishments for defrocked alchemists, as it were, was to be hanged on a gilded scaffold. And sometimes they were forced to wear suits of tinsel as they were hanged, to make it a public spectacle.
NARRATOR: As Newton immersed himself in alchemy, his paper on light was igniting a firestorm in London.
The job of evaluating Newton's ideas fell to another Royal Society member, Robert Hooke, who would become Newton's lifelong nemesis.
JED BUCHWALD: The paper got published, and Hooke wrote a report on this. And it's a peculiar report, because, effectively speaking, what it says is, "I accept all of Newton's experiments, but whatever is new in them I already did. And all of his claims about light are wrong."
NARRATOR: For four years, Newton and his critics fought it out, with blow after blow published in the magazine of the Royal Society.
The sensitive Newton was mortified.
WALTER LEWIN: Newton was allergic to criticism, I mean really allergic. He went off the wall when people criticized him.
JED BUCHWALD: The problem for Newton was having anybody question what it was that he had done. He didn't want to tell anybody about it in the first place, but if he was forced to do it, you sure better believe what he said.
ROB ILIFFE: He cannot convince as many people as he wants that what he said is true. And that defeat, if you like to call it that, was very bitter for him. And by the mid 1670s, he's withdrawn completely from the international world of science.
NARRATOR: Newton vowed he would never publish a scientific paper again. In the isolation of Cambridge, Newton threw himself into alchemy.
Alchemy had been outlawed because the British government feared that frauds would debase the currency with fake gold. And for years, controversy has raged over why Isaac Newton took up alchemy. Even Newton's lab assistant was baffled.
SIR ISAAC NEWTON'S LABORATORY ASSISTANT (Dramatization): What his aim might be, I was not able to penetrate into, but his pains, his diligence, as those times made me think he aimed at something far beyond the reach of human art and industry.
NARRATOR: In the past, many scholars dismissed Newton's alchemy as scientifically worthless, but now, they're taking a second look.
To find out what Newton was really up to, Bill Newman has begun deciphering Newton's coded recipes and recreating alchemical experiments Newton did 300 years ago.
BILL NEWMAN: If we want to figure out what's going on in these laboratory notebooks, that's the way to do it, actually try the experiments and see what happens.
NARRATOR: Newton believed that in the distant past, people knew great truths about nature and the universe. This wisdom was lost over time, but Newton thought it was hidden in Greek myths, which he interpreted as encoded alchemical recipes.
BILL NEWMAN: In some instances he interprets the myths in a very, very exact way, so that they correspond to actual recipes.
NARRATOR: But getting these recipes right is no easy matter. Like all alchemists, Newton concealed his ingredients in bizarre-sounding terminology.
SIR ISAAC NEWTON (Dramatization): Our body thus compounded is called a hermaphrodite, being of two sexes, and it is both father and mother to the Stone.
BILL NEWMAN: He used very colorful language that's typical of the alchemy of the time. For example he talks about "the green lion," "the sordid whore," and "the menstrual blood of the sordid whore." These are terms that had very specific reference in 17th century alchemy.
NARRATOR: One of Newton's recipes, called "the net," comes from the writings of the Roman poet Ovid.
In his poem "The Metamorphosis," Ovid tells the story of the god Vulcan catching his wife, Venus, in bed with the god Mars. According to the myth, Vulcan made a fine metallic net and hung the lovers from the ceiling for all to see. In alchemy, Venus, Mars and Vulcan mean copper, iron and fire.
Viewed this way, the myth becomes an alchemical recipe. And if Bill Newman has interpreted the recipe correctly, he should get the same results that Newton got 300 years ago, a purple alloy, known as "the net," which was believed to be one step towards the Philosopher's Stone.
BILL NEWMAN: Behold: "the net." It worked—a purple alloy with a striated net-like surface—it worked perfectly.
NARRATOR: By recreating these recipes, Bill Newman is finding that Newton's alchemy contained key elements of modern science: it was a systematic process with results that could be reproduced and verified. And historians have also discovered that Newton was not alone in pursuing alchemy. Other scientists of the day, including members of the Royal Society, were alchemists too.
Perhaps Newton's alchemy was less an occult practice than another way to investigate the natural world.
PAMELA SMITH: Alchemy was really matter theory. Alchemy was a science which pursued the most basic questions of "What is the Earth? What is all of the universe made up of? What are the components of matter?"
JED BUCHWALD: There was a profound element to the practice of alchemy which really makes it deserving of being called early modern chemistry. He's not a madman playing around with strange spirituous substances, he's trying to actually figure out how to change material particles around to get one thing out of something else. And that's not so weird.
NARRATOR: Newton's alchemy came as a surprise when it was discovered in the papers bought by the economist John Maynard Keynes in 1936. But other manuscripts now housed in Jerusalem contained an even greater surprise.
For most of his life, Newton held a dangerous secret. As a fellow at Trinity College, he was required to become a minister in the Church of England, but this was something he violently opposed.
Newton became convinced that the central doctrine of Christianity, the Trinity, or the idea that Father, Son and Holy Spirit were all equally divine, was not true. The more ancient Christian texts he read, the more he believed Christ was the son of God but not God's equal.
SIMON SCHAFFER: Now, because Newton was so convinced that God is extremely powerful and unique, Newton, as the saying goes, "reads himself into heresy." In other words, Newton begins to minimize, to play down, eventually to deny the divinity of Christ.
GALE CHRISTIANSON: And Newton comes to the conclusion, very early on, that the Trinity is a blasphemy on the First Commandment, because the First Commandment says that "thou shall have no other God before me." And the worship of the Father, Son and Holy Ghost, from Newton's point of view, is a heresy.
NARRATOR: But denying the Trinity was illegal, and Newton was risking everything by holding these beliefs.
STEPHEN SNOBELEN: If Newton had been exposed, while he was at Cambridge, as an anti-Trinitarian, his career would have been over. He would have been ostracized. It's almost certain that it wouldn't have involved being put to death, but definitely prison would have been one possibility.
NARRATOR: Newton was eventually excused from becoming a minister. But he wrote more about theology and alchemy than science and math combined.
Only recently made available to the public, at the National Library in Jerusalem, these documents are now revealing that for Newton, religion and science were inseparable, two parts of the same life-long quest to understand the universe.
SIMON SCHAFFER: Newton himself wanted to design a universe in which God was absolutely present and absolutely powerful. There's an enormous irony there. In the 18th century, gangs of interpreters, most of them French, will take the God out of Newton's world. It's a very common image of what the Newtonian world was, that it was soulless, that it was mechanical, that it really wasn't theologically motivated at all.
GALE CHRISTIANSON: Now, ironically, that's very anti-Newtonian, because Newton argued that God had to be present, you couldn't read him out of the universe.
SIR ISAAC NEWTON (Dramatization): The most beautiful system of the sun, planets and comets could only proceed from the counsel and dominion of an intelligent and powerful being.
NARRATOR: Newton owned more than 30 Bibles, and he examined them as rigorously as he did the natural world. Correlating Biblical passages with astronomical information, he re-dated ancient history, drawing up elaborate charts and chronologies that show civilization starting around 980 B.C.
JED BUCHWALD: I have hundreds and hundreds of pages of computations and workings and re-workings where he tries to probe this over a period of close to 30 years. Time and time again, he'll come back to it, calculating and recalculating, trying to make it work, just the way he tried to make his theories of light work.
NARRATOR: With the same fervor that he brought to science and math, Newton also combed the Bible for keys to the future.
STEPHEN SNOBELEN: What he was trying to do is determine when the end would come, when Christ would return, when all the apocalyptic events of the end times would, would come to a head.
NARRATOR: And that date is now alarmingly close: the year 2060.
JAMES FORCE: Newton is not a man who keeps his theology in a box that he brings out only on Sundays, and then a man who does his science as a working man the rest of the week. Newton sees his work as a seamless unity, and his project is to understand the truth of God.
PAMELA SMITH: Most people today think of religion and science as completely different spheres. In Newton's day, science, the investigation of the natural world, was a part of religion. It was...all questions, in some ways, ended in divine knowledge.
NARRATOR: Alchemy and religion might have continued to dominate Newton's thoughts, but in his early 40s, he received a surprise visit that would refocus him on physics. It was the astronomer Edmond Halley, now known for the comet named after him. He asked Newton an esoteric sounding question about planetary orbits.
EDMOND HALLEY (Dramatization): My question is this: What kind of curve would be described by the planets, supposing the force of the attraction towards the sun to be reciprocal to the square of their distance from it?
SIR ISAAC NEWTON (Dramatization): An ellipse.
EDMOND HALLEY (Dramatization): An ellipse? How do you know?
SIR ISAAC NEWTON (Dramatization): I've done the calculation.
EDMOND HALLEY (Dramatization): You have? How did you calculate it?
SIR ISAAC NEWTON (Dramatization): I'll show you...should be here somewhere. Don't worry, I'll re-do the calculations. I'll send you a copy.
NARRATOR: Halley's question would change science forever. Through years of observation, scientists had discovered that the planets move around the sun, not in perfect circles, but in slightly elongated, elliptical orbits. But no one could explain why.
Halley and many other scientists had begun to suspect that the planets were attracted to the sun by some kind of force. They guessed that this attraction became weaker with distance in a mathematical relationship called the "inverse square" law.
For example, the inverse square law says that when a planet is twice as far from the sun, the gravitational attraction it feels is four times weaker. But no one had been able to prove this resulted in elliptical orbits.
Several months later, Halley received a paper from Newton. It was Newton's mathematical proof that a planet obeying the inverse square law of gravity must travel in an elliptical orbit.
Newton may have used calculus to arrive at this, but he had not published this new form of math, and his proof was written in the traditional language of Euclidian geometry.
But Newton wanted more than a mathematical proof; he wanted to know how the planets move through space. For the next 18 months, Newton worked on this question day and night. He barely ate, he barely slept, and he saw no one.
GEORGE SMITH: When you look at what he did during that time, it's difficult to believe that any one human being carried out this amount of novel mathematical and mathematical physics research.
NARRATOR: Finally, he submitted a 500-page draft of his masterpiece, the Principia Mathematica, to the Royal Society for publication.
GALE CHRISTIANSON: It is the greatest book of science ever written, bar none. It is the most magnificent work, it is the most all-encompassing work, it is the most daring book of any scientific treatise ever written.
JED BUCHWALD: After the publication of the Principia, Newton, Newton...Newton is the man. I mean, you know, very few people can understand what this thing is about, but a lot of people can see that there's something important in here.
NARRATOR: What people saw was that Newton was providing a new framework for understanding the universe, building on centuries of work by his predecessors. Galileo had spent years studying motion on Earth and discovered that projectiles always follow a curved path called a parabola. But Galileo believed that motion of celestial objects like the moon was very different.
PETER GALISON: Galileo still believed there were differences between the terrestrial and celestial, he retained the idea that was ancient: that motion was different up at the moon and above.
NARRATOR: Newton disagreed. He thought the same laws must govern motion on Earth and in the heavens. To demonstrate, he would have to devise a set of laws so powerful they could explain motion everywhere.
He began the Principia with a set of ground rules, his famous three laws of motion: an object in motion will remain in motion forever unless acted on by an external force; an object's rate of acceleration is proportional to the force exerted on it; and for every action there is an equal and opposite reaction.
These laws allow scientists to make such accurate predictions about how objects move that they are still used today to send rockets into space and explore other worlds. But explaining the orbits of the planets required another ingredient.
This brought Newton back to the work he had begun 20 years earlier on gravity. To show how gravity works on Earth and in the skies, Newton designed a thought experiment. He imagined firing a cannon from the top of an extremely tall mountain. From his first law of motion, he knew the cannonball would travel in a straight line at a constant speed forever. But gravity pulls the ball downward. If its speed is low, the cannonball hits the Earth near the mountain: the higher the speed, the farther away the ball lands.
WALTER LEWIN: If you throw it faster, it comes farther away; even faster, farther away; even faster, it may go a thousand miles; even faster, it may actually go almost half way around the Earth and there hit the Earth.
NARRATOR: Newton imagined that if its speed were high enough, the cannonball would travel all the way around the Earth and settle into orbit.
PETER GALISON: The orbit of the cannonball around the Earth was a balancing act between the cannonball's tendency to fly off in a straight line, and it's being yanked back towards the center of the Earth continuously by the force of gravity.
So, in Newton's picture of the world, there were two things: the natural tendency of an object to travel in a straight line—which was true on Earth or in space or anywhere—and there was the attraction of gravity, which was true on the surface of the Earth, and it was true up in space.
NARRATOR: Newton's breakthrough was to see that the moon's orbit around the Earth and a cannonball's motion on Earth were governed by the same law of gravity.
WALTER LEWIN: That is a beautiful way of persuading you, me and probably his colleagues that cannonballs falling to the Earth and the moon falling to the Earth is one and the same law of physics: gravity. The moment that he realized that, almost everything else follows from that.
NARRATOR: Newton reasoned that if gravity governed motion on the Earth and the moon, why not on Jupiter and its moons, which he had seen with his reflecting telescope? Why not the entire solar system?
In a bold leap, Newton proclaimed that this invisible force operates everywhere in the universe.
GEORGE SMITH: It's an incredible leap. It's beyond anything anybody had imagined at the time.
NARRATOR: Newton called it the "universal law of gravitation," and he wrote it in one simple mathematical equation.
GALE CHRISTIANSON: It's so important because it really tells us how nature operates in a fundamentally new way. Newton is saying, "The same thing that is going on in the heavens is going on on Earth and vice-versa." It gives us a guidebook to answering the age-old question of what causes the rise and fall of the tides. It gives us answers to the orbits of the planets and their positions. It's a tremendous act of intellectual triumph, one of the great keystone, cornerstone pieces of our intellectual heritage.
WALTER LEWIN: It was a total revolution. The universal law of gravity was a complete revolution, the way that we think about the world, the solar system, therefore the universe—whatever the size of the universe was in those days—and therefore, the way we think about ourselves.
GEORGE SMITH: The Principia showed a promise that gravity by itself could account for virtually all the motions we know of in our planetary system. And the rest of science, to this day, has built off of that foundation. Newton turned out to be more correct about that than he could possibly have been confident of.
NARRATOR: But Newton was not able to enjoy his success for long. As soon Principia was published, Newton's old rival, Robert Hooke, claimed he had come up with some of the key ideas first. And later, others attacked it because Newton did not explain what gravity is, just how to calculate its strength.
WALTER LEWIN: And Newton himself didn't understand it. How can this object attract this object? There is nothing in between them.
MORDECHAI FEINGOLD: That seemed to them as going back to some sort of an occult philosophy.
NARRATOR: In fact, some think Newton's idea of gravity was related to the occult practice of alchemy. Newton was fascinated by an alchemical process called the "vegetation of metals" in which inert metals seem to come to life and grow like plants. Today, we know this is just the reaction of mercury and silver with a solution of nitric acid, but Newton thought these kinds of reactions showed that mysterious, invisible forces he called "active principles" were at work everywhere in nature. Perhaps he thought of the invisible force of gravity in the same way.
PAMELA SMITH: Newton pursued alchemy because it gave insight into the active principles of nature. Gravity was an occult force, it didn't have an explanation, and Newton believed that it was possible that gravity was one of those forces, one of those active principles. And so, in that sense, Newton's alchemy could give insight into gravity.
NARRATOR: Yet by the early 1690s, after more than 20 years of research, Newton's alchemical experiments had yielded no scientific breakthroughs like those he'd made in math and physics.
MORDECHAI FEINGOLD: We're not quite sure exactly what he was trying to do. He certainly was looking for something—it's obviously something quite big—and he obviously did not find it because he opted not to publish anything about it.
GALE CHRISTIANSON: I think there's no question that he was disappointed because he was looking for ultimate answers to questions, and he had failed in alchemy as he had not failed in any other pursuit.
NARRATOR: Finally, Newton had what many think was a nervous breakdown. He made wild accusations against his few friends, charging one, the philosopher John Locke, with trying to "embroil" him with women.
JED BUCHWALD: Locke is puzzled by the whole thing. You know, "What's up with Isaac there?" He wasn't running a brothel on the side and bringing Sir Isaac to it.
NARRATOR: When Newton explained that he was sick and had gone without sleep for five nights, his friends forgave him.
SIMON SCHAFFER: He was knackered. If he had a breakdown, I think it was probably because of exhaustion.
NARRATOR: Whatever the cause, Newton's illness was brief. Within a few months, he seemed to have regained his composure. And soon a strikingly different Isaac Newton began to take shape.
Newton moved to London and was appointed Master of the Mint, a well-paid job that put him in charge of issuing new currency and cracking down on counterfeiters—about two dozen counterfeiters were executed while Newton was in charge. Newton become a Member of Parliament, president of the Royal Society, and was knighted. He commissioned at least 14 portraits of himself.
GALE CHRISTIANSON: It is an extraordinary change. He's very much this icon, and he settles into that role, I think, in London, and likes the, the role of the great man.
NARRATOR: A year after Robert Hooke died, Newton published his second great masterpiece, Opticks, which expanded on his work with light. At the end of this book, Newton finally wrote up some of his key ideas about calculus, 40 years after they were conceived. And although he had given up alchemy, he continued to devote himself to theology.
ROB ILIFFE: Right up to his death, he tried to keep his heresy as secret as possible, and he thinks, "There's no point trying to convince these people of, of what I'm doing, because the time is not right. These people aren't fit to receive the kind of word that I'm giving out."
NARRATOR: Newton died in 1727. He was 84 years old. He was buried among kings and queens in Westminster Abbey, beneath a monument to his scientific achievements, his alchemy and passionate, but heretical, religious beliefs virtually unknown.
Now, two and a half centuries later, a new picture of Sir Isaac Newton is emerging, along with a new understanding of the roles that science, religion and alchemy played in his life.
JAMES FORCE: He sees his world as one world, he sees his pursuit of truth as one pursuit, and whether it takes him to books of theology or to books of nature, whether it be books of astronomy or books of alchemy, it doesn't matter to him.
SIMON SCHAFFER: What Newton does is brilliantly use the tools appropriate to every field in which he worked. He's an ingenious and energetic builder who's astonishingly brilliant at composing gorgeous monuments of the most intensely clever design. Sometimes these appear as great books like the Principia itself. Sometimes they appear in experiments. But we would be wrong to look for a single key which unlocks the whole mystery of Isaac Newton.
WALTER LEWIN: The man was a complete genius. I mean people like Newton, if I shoot off the hip, maybe once in 500 years, at best.
NARRATOR: What did another great genius, Albert Einstein, have to say about Newton? Find out on NOVA's Web site. For Newton's Dark Secrets, go to pbs.org.
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