Isaac Newton (Episodes I-IV): Podcast Scripts

Isaac Newton: Burning Down The House

Hello and welcome to this episode of Physical Attraction, the show that tries to explain physics, one-chat up line at a time. Today we’re going to be dealing with the life and works of Isaac Newton, who cast a very long shadow over physics and whose laws are still pretty much the first thing any physicist will learn when they start out.

For our chat-up line: “Are you breaking Newton’s Universal Law of Gravitation? Because you’re unusually attractive.” At which point you probably have to backpedal rapidly and say that you’re not accusing the other person of being unusually massive. Then you go cry in a corner and remind yourself that Newton was highly likely asexual and it helped him get a lot of stuff done.

Because, while it is true that Newton’s law of Universal Gravitation means that everything with mass attracts everything else with mass — which means that you, listening to this, are undeniably and physically attracted to me, and there’s nothing you can do about it — meow — gravity is a very weak force by comparison to the other three. If you’re sitting across the room from me, the attraction that we exert on each other is around 3 billionths of a Newton. That’s tiny. Even if we’re only a couple of metres apart, the force is the equivalent of the weight of about a grain of sand. So you’re not exactly likely to come flying towards me in paroxysms of lust any time soon — at least, not due to gravity.

And it also depends on how massive the objects in question are, and how far apart they are. So you’re more attracted to all of the people who are closer to you — or all of the people who are at the same distance as me, but who weigh more than I do. Which doesn’t mean we can’t make it work. But, by this measure, at least, the Earth will always love you more than I do.

Back to Newton, then, who loved science. When talking about famous physicists — any famous figure from history — you inevitably find that people split into pro- and anti-camps. This is because we like to paint simplified historical pictures, and then we like to make ourselves feel clever by tearing them down. So, for every person who achieves the incredible heights of renown that Newton did, there are people who will attack their legacy for all sorts of reasons. Chances are a lot of the criticisms are valid; and, with science historically often being discovered and lost, it’s foolish to say things like Isaac Newton is solely responsible for modern physics and so on. The same is true for every ‘fact’ I tell you about his personal life. But it seems clear that Newton, alongside Einstein, are the two physicists in the modern era who had the greatest impact on the science. There is a reason why the history of physics is divided into before and after Newton lived. Same with Einstein. His was undoubtedly a rare genius.

So he’s an important enough individual that it’s worth covering him as a person as well as the science that’s associated with him. I also think it’s fun to cover this in a biographical way, though, because by all accounts Newton was pretty eccentric. For example, he was a member of the Houses of Parliament for a few years — you’d think that such a renowned genius would have a lot to say on the issues of the day, and might even be able to direct society towards enlightenment. Representing the University of Cambridge, too — you’d think they might have something to say. But Newton was instead famously taciturn: apparently the only time he’s recorded as speaking, he was complaining that the chamber was cold and asking to open a window. He displayed some incredible snark and often outright anger towards people he disliked, especially longtime rival Robert Hooke. If you’re in Britain, you might have a £2 coin. Look around the edge, and it says “standing on the shoulders of giants” — a famous Isaac Newton quote, that he said to Hooke about his work:

“If I have seen further, it is by standing on the shoulders of giants.”

Famous quote — Oasis even named a rubbish album after it. (By the way, I feel like even after the world ends, the NME will still be publishing articles about the Gallagher brothers’ feud. NO ONE CARES.) But many people now think that he was mocking Hooke, who had kyphosis — what used to be called a hunchback. And alongside this, his temper is notorious: he frequently flew off the handle later in life, but even aged nineteen, the young Isaac — who listed his sins in an act of penance — mentioned amongst them:

Threatening my father and mother Smith to burn them and the house over them.”

Evidence of a turbulent childhood? Possibly. Isaac’s father died before he was born, and his mother remarried. That’s why he refers to Smith — the name of Newton’s stepfather. But then again, who didn’t threaten to burn down their family home at least once while they were a teenager. It’s a difficult time.

I can’t resist a little digression into the matter of Isaac Newton’s faith. He was a devout Christian throughout his life, but he was also what you might technically call a heretic. There’s a bit of an overlap here with the Roman Empire, which anyone who’s met me will tell you is… a slight obsession… for which you can thank legendary podcaster Mike Duncan of The History of Rome. Anyway: when Constantine converted the Roman Empire to Christianity, he found himself a little bit frustrated with his chosen religion: only three hundred years after the life of Jesus, the church was already quibbling over little bits of doctrine, the interpretation of certain words, and so on. One of the key points of argument for the early church was in the nature of the Trinity — and, in the Eastern Roman Empire, whole civil wars would end up being fought partly on this topic. So orthodox belief held that the Trinity means that God the Father, God the Son, and God the Holy Spirit are all aspects of the same being, the same entity. But in Newton’s opinion, whenever “God” is used in the Bible it refers unambiguously to God the Father, and that Jesus and the Holy Spirit are separate entities. These various controversies were all being thrashed out in the 4th century by bishops Arius and Anathasius, with Anathasius and his view of the Trinity winning out.

This might sound to those of you who aren’t theologically minded to be a tiny distinction. But it was enough to get you burned at the stake throughout many eras of history. Also, when the Mongol hordes were invading Europe, the Pope spent a great deal of his letter to the Mongol Khan explaining this ‘correct’ view of the Trinity. The Mongol Khan obviously wasn’t especially interested. He argued that the only God the Pope needed to worry about was the one that was allowing the Mongols to win victory after victory.

I think the key point here is that Newton was, in many ways, a radical. When he was first being introduced to the Greek philosophers that had been taught in Cambridge for hundreds of years, he kept a journal of his thoughts. It was headed with a Latin inscription: “Plato is my friend, Aristotle is my friend, but my best friend is the truth.” His willingness to question the Orthodoxy of the Catholic Church was all part of this truth-seeking. A healthy scepticism of accepted beliefs is absolutely a necessary component of science. Intuition is your friend; so is belief; so is logic. But your best friend — your greatest friend — must always be the truth, followed closely by your ability to prove it.

Like many young geniuses, Isaac Newton was misunderstood at school, at first. His mother briefly pulled him out of education to run the household farm after his stepfather died. But this didn’t work out due a combination of Newton being ridiculously unsuited for running the farm, and his Uncle’s intervention eventually persuading his mother that he should go to University. To prepare for this, he lodged with the headmaster of the school in Grantham for a year or so, and by 1661, he was at Cambridge.

Newton originally wanted to pursue a degree in Law, but eventually his studies became far more mathematical. Mathematics was advancing, but physics — or natural philosophy as it was called then — was taught largely the same as it had been during Aristotle’s day. Aristotle lived in the 4th century BC, so the fact that he was still the foundational text for much of what was taught tells you something about how much development there had been in the meantime.

But there are four major developments that we should talk about, all of which had an influence on Isaac Newton at some point or another. Copernicus was among the first of the Westerners to suggest that the Earth went around the Sun — what’s called the heliocentric model. Incidentally, bit of linguistics — helio-centric — the Sun, helios, at the centre. Helium is called helium because the element was first discovered by analysing light from the Sun. It wasn’t discovered on Earth until later. It’s actually crazy that we put helium into balloons given how rare it is: a huge waste, when it’s also useful in MRI scanners and industrially. Luckily, they found a big reserve of it recently, so we’ll have abundant helium for a while yet; just don’t inhale it all to give yourself a squeaky voice.

So Copernicus, owing something of a debt to the Islamic astronomers who’d figured out that the Earth was moving and not stationary at the centre of the Universe, suggests that we’re orbiting around the Sun. Then astronomer Tycho Brahe makes some very accurate observations of the motions of the planets and so on. Kepler looks at his data and comes up with some key laws that apply to the motions of the planets. Kepler’s laws are essentially the following:

All planets move in elliptical orbits, with the Sun at one focus. Ellipses are squashed circles, and you can imagine that this means one direction of the ellipses is longer than the other — that’s the major axis. The focal points of the ellipse are two symmetrical points on that axis that help you define the curve — so it’s not quite the same thing as the centre, although that gives you a rough idea. That’s law number one: elliptical orbits.

Law number two is that an imaginary line that connects the planet and the Sun will sweep out an equal area in an equal time.

Law number three relates the time period of the orbit to size of the orbit. Specifically, the square of the time it takes for one full orbit is proportional to the cube of the major axis — that’s the longest length — of the ellipse. It makes intuitive sense that bigger orbits take longer, but this specific relationship is Kepler’s Third Law.

Why am I banging on about Kepler’s laws? Kepler’s laws are observed relationships — Kepler noticed in the data that these things were always true. But he couldn’t really explain them. When Newton discovers his laws of motion, he can use them to explain Kepler’s laws. This is an example of a key idea in physics: your theory is correct if it can explain the observations. Or, sometimes, you set up an experiment to make observations that will confirm or deny your theory.

Incidentally, I think it’s fun to think how — philosophically — superstition kind of led to all of this being possible. Because men like Kepler and Brahe were astronomers, but they were also astrologers. Astronomy is the science of space, while astrology is the superstition of space — star signs, that kind of thing. I was always especially sceptical because I have a twin brother; surely no one could have a closer star sign to mine than him — and yet we’re completely different. Kepler was probably sceptical of astrology — but that was his actual job: he was employed by the Emperor Rudolph II principally to read his horoscope. Without astrology, it’s likely that funding for telescopes would have been a lot harder to come by. So, if you’re listening, and you’re an academic trying to get funding in your field — convince politicians that you can use it to tell the future. Never fails.

So, Kepler and Copernicus. Also Galileo, who made massive improvements in various fields. He contributed to mathematics, and was one of the first people to realize that the laws of nature are best expressed mathematically. He built better telescopes than had been constructed for a very long time, and used parallax — the apparent motion of stars as the Earth moves — to learn about the heavens. He discovered the moons of Jupiter, observed stars, and even tried to measure the speed of light: before people knew that light even had a speed.

Galileo is very famous for an experiment, supposedly involving the leaning Tower of Pisa, where he tested the theory that feathers will fall at the same rate as cannonballs. This experiment was probably done before Galileo, but there’s evidence that Galileo did understand what would later be part of Newton’s First Law of Motion. He said that, in a frictionless world, an object given a finite speed would carry on going forever.

This is an example of where your intuition — and your observations of the world — can lead you astray. If you think about day-to-day life; it’s not frictionless at all. (One of my chatup lines is: “Let’s you and I get together so that we can empirically determine our mutual coefficient of friction.” FILTHY.) But based on your observations, the idea that — if you give something a kick, it will carry on moving in a straight line forever — it’s completely contrary to what we see. You can’t blame Aristotle and the Greeks for thinking that things naturally slow down unless you push them — or that the natural way things want to move is arcing downwards. It makes sense based on what we see. But we are biased by our point of observation: on a very friction-filled planet Earth. If we were conducting all of our experiments in a more typical region of space — surrounded by the cosmos, drenched in nothing — we would see the laws of nature for what they are more easily. That’s why this idea took so long to become accepted.

The final thing to mention that was a major departure from Aristotle was that Islamic scholars had published some pretty important textbooks on Optics, including most famously the Book of Optics by Ibn al-Haytham, which contained some interesting and important ideas. Many people beforehand had thought that vision arose due to something emerging from the eyes, rather than light entering the eyes. Alongside this important experiments about refraction, reflection, and transmission of light were conducted by Islamic scholars 600+ years before Newton. One of the key points here is that Ibn al-Haytham was one of the early advocates of comping up with ideas, or hypotheses, and then testing them by experiment. This is the scientific method. It is this idea, applied to various different fields, that is essentially the single most important aspect of what changed in the 17th century, around the time of Newton, and started this rapid acceleration towards the world we live in today. Galileo was also a big proponent of this idea, but Ibn al-Haytham got there first.


Notching up their improbable second mention in this physics podcast about Newton, the Mongol horde are kinda partially responsible for a lot of this science being lost when they destroyed vast swathes of the Islamic civilizations that had arisen before in the 13th century.

So we can see that Newton was indeed a rare genius, but — as is so often the case with really revolutionary change — the groundwork is laid by the seemingly slow period beforehand. The developments that Newton and others made laid the groundwork for the Industrial Revolution. The Russian Revolution in 1917 is another example. On the surface, incredibly dramatic: a monarchy is toppled and replaced by a Communist government, a swing from the far-right to the far-left. But the groundwork had been laid for hundreds of years in Russia, both intellectually and in terms of the revolutionary movements — and, hundreds of years before that time, in the French Revolution, the English Civil War…

Newton read a great deal of the old, Greek-style mathematics of Aristotle, Plato — but also some of the newer, more scientifically minded ideas of Descartes, Boyle, Galileo and Kepler were starting to draw his eye. He quickly realized that to understand astronomy (and astrology), he would need to learn mathematics, so that was the next step. It was in mathematics that his first real developments would start to come. In 1665, he received his degree — without too many mind-blowing discoveries. His notes at the time have come down to us: “Questions Concerning Natural Philosophy.”

Alongside notes on the texts he was reading, we see the beginnings of his scientific evolution. He accepted and liked the theory of atoms that the Ancient Greeks had come up with under Democritus, but was out of fashion. He was interested in light and colour, but criticised Robert Hooke’s idea that light was a wave. He ruthlessly criticised the theories he didn’t like, coming up with counterarguments and counterevidence, even when they were made by renowned scholars. He even questioned whether you could manipulate gravity to obtain a perpetual motion machine. (By the way — no, you can’t.)

Like many famous geniuses, you can hear rumours going around that Newton was a poor scholar — and it’s true that while he was an undergraduate, he didn’t get the highest marks out there. But this is probably less down to the fact that he wasn’t dedicated to his studies, and more to do with the fact that his studies were mostly extracurricular — the new science of Kepler and Galileo, rather than the old science of Aristotle that they were actually testing him on at Cambridge at the time.

In 1666, twin historical events struck Great Britain. The Plague, which forced the University of Cambridge to be closed, and the Great Fire of London, which may have put an end to the plague. When Cambridge was closed, Newton was forced to return home to Lincolnshire for a couple of years. It was there that his scientific career began in earnest.

And it’s here that we’ll stop for this episode. Next time, we’ll get into the discoveries Newton made in his early career — the mathematics that would become calculus, his research into optics, and start to touch on his obsession with… alchemy.
of course… that time he nearly had his brain smashed in by a rogue, anti-science apple.
Thanks for listening to this episode.
PLUGS — FACEBOOK, TWITTER, DONATE, LIKE, REVIEW, TELL ONE PERSON (30 eps = 1 trillion), whatever’s recent

Until then, don’t burn down any houses, and be kind to each other.

Newton II: the Plague Years, Calculus, and Corpuscular Light

Hello and welcome to Physical Attraction. We are and remain the only show out there that can explain physics, one chat-up line at a time. Today, we’ll be continuing our look at the life and career of Isaac Newton: a man who needed no help with physics, but some serious help with flirting. Or possibly had no desire to chat anyone up at all — which is just fine, by the way.

At one point, he fell out with his good friend, John Locke — and, mid-nervous breakdown, hid himself away from everybody. When he wrote a letter to Locke to explain himself, he apologised:

Being of opinion that you endeavoured to embroil me with women & by
other means, I was so much affected with it as that when one told me you were sickly & would not live — I answered twere better if you were dead.”


Wishing death upon your friends for attempting to ‘embroil you with women’ in your mid-50s might seem a little bit extreme, but I guess if anyone’s ever been on a blind date that their friends set up they might just sympathise.

But we are not Newton, so this episode’s chat-up line is a gravitational one:

“I like those clothes. They’d look better accelerating towards my floor at 9.8 metres per second per second.”

For that is the Universal rate of gravitational acceleration on Earth’s surface that all objects have! Of course, this would only be the rate of acceleration initially — before air resistance comes into play — but, apparently, when someone throws their clothes to the floor in a fit of passion, whipping out a portable whiteboard and attempting to calculate the drag coefficient “kills the mood.” Well, sorry.

So when we left off in our biographical history, Newton had just left Cambridge due to the plague after a successful but undistinguished undergraduate degree. He’s now holed up in his house in Lincolnshire. It was here, in a diary inherited from his stepfather that had plenty of blank paper, he began his calculations in a book that’s now called The Waste Book.

Essentially the most important part of what Newton was working on here was the fundamentals of calculus. I have to point out that Leibniz also developed calculus alongside Newton. There’s a huge controversy about this that started while both men were alive, and has essentially continued to the present day without ever being properly resolved. I think the most likely explanation is that they both came to it independently. After all, mathematics is really discovered rather than ‘invented’, and this is especially true of calculus that governs so much of the world around us. There’s some evidence that Leibniz saw Newton’s papers while he was working on calculus; it’s also fair to say that Newton didn’t publish his calculus in full until well after he claimed to have finished it. The two even worked together on some aspects of the mathematics. For convenience’s sake, I’m going to talk about it from now on in terms of Newton’s life — but just remember the caveat that he probably wasn’t the only one who discovered it, or who could have discovered it.




Fine. So what is calculus? It is essentially the mathematical study of change. Before calculus, we had geometry — which is the study of relationships between things like areas, volumes, distances… here you have theorems, like Pythagoras’ theorem which relates lengths on a triangle, and so on.

You also have algebra. Basically, algebra is the study of calculating where the numbers you’re calculating with are completely general. So for example, the square of a number is the number multiplied by itself. We have squares: 1 squared is 1, 2 squared is 4, and so on. But the operation “to square a number” is an instruction on what to do with the number: multiply it by itself. Algebraic equations are instructions, applied to general numbers. So saying x2 is the same as saying, whatever x is, square it. That way, your calculations are completely general: you plug the numbers in at the end.

So geometry studies shapes, areas, volumes. Algebra studies operations between numbers. Calculus studies changes: and it turns out that you can get to all kinds of rules and useful results by considering infinitesimal changes — changes that can be as small as you can possibly think of.

To see why, it’s helpful to imagine a graph — a line — make it as wiggly or as straight as you like, as long as it’s continuous. If you zoom in on a segment of that line far enough, it will be approximately a straight line. Because the change you’re considering — the section of line you’re considering — is infinitesimal, you can always zoom in far enough that the line is approximately straight. And then you can say: if I am at this point, and I move infinitesimally along the line, this is the direction I’m going in — along that straight line.

But the direction of that local straight line is like a rate of change. It’s like looking at a stock exchange graph and saying, okay, at precisely 12 noon, how quickly was the price changing? If I wait one minute, how much will it go up or down? Finding the rate of change of something is differential calculus.

And, similarly, if you have the rates of change of your stock price at all times, you can work out how much it has changed overall. You can go from the gradients — from the rates of change — to the value of the function itself. This is the reverse of differential calculus: from how something changes, you determine what it must be now. (Providing you know what it was when it started changing.) This is integral calculus.

The importance of this really can’t be overstated. Pretty much anything that deals with anything changing is going to require calculus to deal with. And, since the job of physics is absolutely to make predictions about the future, we need to understand how things change with time. And it turns out there are all kinds of useful relationships. If you differentiate distance travelled, you get velocity — the rate of change of distance. And if you differentiate velocity, you get acceleration: that’s how quickly your velocity is changing. So, if you want to know things like: how quickly something’s moving, where it will be, how fast it’s accelerating — you need to express it all in terms of calculus.

What Newton discovered is that you could get to old mathematical results — things that people knew to be true already — using calculus. By adding together lots of infinitesimal disks, you can calculate the area of a circle. By adding together lots of infinitesimal shells, you can calculate the volume of a sphere. So you could use calculus to get lots of the old results of geometry and algebra — and to prove lots of things that had previously only been observed, or had been discovered but never proved.
This mathematics was so new that when Newton published things he’d discovered using calculus, he basically had to express it all in terms of geometry — which was considered to be proper mathematics. And he derived every result in his work very, very, very carefully — with completely flawless logic — step by step, from a series of statements no-one could possibly disagree with. (In mathematics, these statements, which kinda define the math you’re using, are called axioms.) His habit of doing this meant that it was Leibniz who developed the convenient, algebraic notation for calculus that mathematicians and physicists know today. This style also means that the Principia Mathematica, Newton’s most famous work, is pretty much unreadable.

In fact, when I was applying for undergrad, I originally wrote on my personal statement that I’d read the Principia and been inspired by it. Then I actually sat down and tried to read the Principia. A few hours later, I sheepishly removed the reference to the damn thing from the statement. It. Is. Dense. And what it shows you is that a lot of what Newton discovered, that seems completely obvious now — it was not obvious when it was discovered. It took a very long time, and a great deal of complexity, to figure these things out. In the last few hundred years, we’ve digested it and condensed it down to a form where you can learn about it in school or University, and I can try my best to explain it to you over a podcast: but initially, this stuff was cutting-edge, highly technical mathematics.

Amongst other things, he did work in infinite series. It turns out that you can approximate many functions — like the sine and cosine trigonometric functions that deal with ratios in triangles, and express the mathematics of waves — or the exponential function that we’ve talked about in our TEOTWAWKI episodes, that you get when something’s doubling — by adding together lots of algebraic expressions.

So, for example, instead of the exponential function of x, you can have

1 + x + x²/2 + x³/6 + ….

And so on.

It’s crazy mathematics, really. To get to the true value for e to the x, you technically need to add together an infinite number of terms. But under certain circumstances, the higher order terms are small, and you can ignore them. In this way, more complicated functions can be converted into powers — squares and cubes — which are mathematically easier to deal with. This method is sometimes called Taylor expansion — and it’s basically all of physics.

Okay, that’s a slight exaggeration. It’s most of physics that doesn’t need computers to solve. But, seriously though, anyone who studied a physics degree will agree with me. Taylor expansion is a huge deal. Without the stuff that Newton was working on, we’d be completely stuffed.

This development of calculus was really a life-long work: it took decades to fully exploit it all. But the fact that he was able to prove results in a more efficient and elegant way than before drew people’s attentions: by 1669 he was being described in letters as:

“Mr Newton, a fellow of our College, and very young … but of an extraordinary genius and proficiency in these things.”

Newton was soon appointed as Lucasian Professor at Cambridge, and a Fellow of the Royal Society -which both remain incredibly high honours in the field of science. But he didn’t initially lecture calculus — he was more concerned about optics.

What Newton essentially discovered that had him so excited was that simple, white light was not so simple after all. All the way back to Aristotle, people had thought that light was naturally white — and that colours basically arose from mixing “light” and “dark” in certain ratios. Obviously this wasn’t going to do. Newton noticed something called chromatic aberration when looking through his telescope lenses. We now know, as he discovered, that this pattern of colours is caused because of something very fundamental. The way that light refracts, or bends, in glass — it depends on the wavelength of the light. And, since different colours of light have different wavelengths, they were bending by different amounts. This means that, with a simple experiment — one that you probably did in school — Newton could use a glass prism to split light into all of the colours of the rainbow. The colours weren’t really a mix of light and dark, at all. Instead, somehow, bizarrely, white light was a mix of all of the colours.

By analysing the new, strange, colourful light he was producing, Newton came to a few conclusions. First, he noticed that no matter whether the new light was refracted, reflected, whatever — it didn’t change colour. It seemed that colour was an intrinsic property of light. In Newton’s own words:

“I might add more instances of this nature, but I shall conclude with this general one, that the colours of all natural bodies have no other origin than this, that they are variously qualified to reflect one sort of light in greater plenty than another.”

In other words, he figured out that the objects aren’t so much generating the colour themselves. Instead, they’re interacting with the light that already has various colours, and some intrinsic property of the object determines what colour it has — because of what types of light it reflects.

Newton, in his theory of light, was starting to touch on a real physical controversy. He didn’t know it yet, but part of what he was thinking about would lead to controversies that would need quantum mechanics to solve. Newton was already thinking about what the nature of light was, fundamentally — and he felt convinced that it must be corpuscular, or made up of little particles. In Newton’s view, this could explain how light was “refracted” — the little particles of light bounced more when they travelled into a denser medium. This, for Newton, explained why glass bent light more than water, and why water bent light more than air.

Newton felt that light should be like particles, and not like waves. This is a belief that Newton had throughout his life, really — even back to the schooldays where he was writing his questions concerning natural philosophy. He said — if light was a wave, as people like Huygens were suggesting — surely it would bend around corners, like sound waves do? Instead, it seemed to travel in straight lines. It could be blocked by objects. Particles travelled in straight lines, so light must be a particle.

The world probably wasn’t ready for our modern theory on light, which has ended up being a rather strange mix — particles that sometimes behave like waves — so it’s perhaps fair enough that Newton didn’t get everything right on light. But it’s worth saying that because of how well-respected Newton was, his corpuscular theory of light dominated for more than 100 years — even though it couldn’t explain aspects of light that Huygens’ theory could. And I think the fact that he never changed his mind on this, maybe, you can begin to hold against him.
And in his corpuscular theory on light, we begin to see some of the dark sides of the character of Newton. Because, whatever else he was, he was a highly sensitive egotist who couldn’t stand for any criticism at all. Remember last episode we talked about his feud with Hooke? This is probably where that feud really began. To quote from St Andrews University:

“In 1672 Newton was elected a fellow of the Royal Society after donating a reflecting telescope. Also in 1672 Newton published his first scientific paper on light and colour in the Philosophical Transactions of the Royal Society. The paper was generally well received but Hooke and Huygens objected to Newton’s attempt to prove, by experiment alone, that light consists of the motion of small particles rather than waves. The reception that his publication received did nothing to improve Newton’s attitude to making his results known to the world. He was always pulled in two directions, there was something in his nature which wanted fame and recognition yet another side of him feared criticism and the easiest way to avoid being criticised was to publish nothing. Certainly one could say that his reaction to criticism was irrational, and certainly his aim to humiliate Hooke in public because of his opinions was abnormal.”

Indeed, he wouldn’t publish his major work on optics — which was called, um, Opticks — until after Hooke died. Even then, to explain some of his observations on optics, Newton needed to appeal to some of the wave-like theories of other physicists. But Newton didn’t like the wave-like theories, because they posed a confusing question for the physicists of the day: if light is a wave, then what’s waving? Huygens, who was in favour of the wave-like approach to the description of light, had posed the idea that there was something called the ‘luminiferous aether’ — some invisible substance that filled the Universe, and vibrated to transmit the waves of light. Newton hated this idea: in his view, if the Universe was full of aether, then surely they’d be able to see how it interacted with matter:

“disturb and retard the Motions of those great Bodies” (the planets and comets) and thus “as it [light’s medium] is of no use, and hinders the Operation of Nature, and makes her languish, so there is no evidence for its Existence, and therefore it ought to be rejected.”

But then, when Newton wanted to explain how heat could propagate through a vacuum, he needed to invoke some kind of aether to make sense of his results. He didn’t realize, as we now do, that light and heat can both be ‘delivered’ by electromagnetic radiation.

Newton may have rejected a universe filled with a wavy aether that transmitted light. But he couldn’t demonstrate that his corpuscles were real, either. The problem of light, and its true nature, probably troubled Newton for all of his life, and would trouble physics for hundreds of years.

It would be wonderful to jump in a time machine and tell Newton about our modern theory of light, and see his reaction. Maybe he would have hated it, or maybe it would have made sense to him — just as soon as it was explained. I think quantum mechanics wouldn’t have upset him all that much, though. He might view it as an aspect of the occult.

But at the same time, he was almost groping after some wilder truths. In Newton’s mind, light was made of very fine particles — so small that it was impossible to see them — while matter, physical things, were made of heavier corpuscules: bigger particles. But, fundamentally, they were the same thing: so, in Opticks, he wrote:

“Are not gross Bodies and Light convertible into one another, … and may not Bodies receive much of their Activity from the Particles of Light which enter their Composition?”

When Newton saw light, he imagined tiny grains of sand, streaming at incredible speed from candles or lamps or the Sun, crashing into things and being reflected and refracted; and, he imagined that these tiny grains of sand might flow into bigger grains of sand and change them — and, perhaps, if you were clever enough and went through the proper procedure, you could turn light into matter.

We now know, of course, that matter — what Newton called ‘gross Bodies’, which is not a good chat-up line — matter is really just a form of energy. And, in fact, matter and light can be converted into each other: when matter and antimatter collide, you get photons of light: and photons can produce matter and antimatter. So in some ways, Newton was hundreds of years ahead of his time in this observation. But we have to remember that he obviously wasn’t thinking of matter and light in terms of energy — he was thinking more of alchemy; some kind of process that could be found which, when applied to light, might somehow compress it or transform it into matter.

What’s so important to remember about Newton was that, in many ways, he was not altogether a physicist. He wrote more about alchemy — transforming substances into each other — than he wrote about physics. Modern physicists have the scientific method established — it’s been used for centuries. We have rationality, and we have experiment, and we have robust theories to explain most of what we see in the world around us to build on. Newton had his experiments, his senses, his judgement — and centuries of superstition and lore, much of which was terribly wrong. His ideas, as we’ve seen, were often his own — and flew in the face of consensus.

The point here is not that Newton was irrational, or crazy, or stupid. It’s that the realm of things it’s reasonable to investigate in science changes over time. We know that he sought out reasons, order, explanations. It’s just that sometimes he thought the explanations were beyond human understanding. Which was true of many things in the 1700s. It’s still more true than we’d like to admit today.

And what’s really fascinating is that you can make a good argument that Newton’s belief in alchemy, in occult and the supernatural, and things that didn’t quite fit with the rationality of men like Descartes and others who had come before him… you can make a good argument that this belief in magic was part of what allowed him to make the intellectual leap to come up with a theory of gravity. Which will be the subject of our next episode!

Next time, we’ll deal with Newton’s Laws and how they laid the stage for all of classical mechanics. We’ll talk about what’s actually in the Principia and how Newton worked out the motions of the heavens. And, of course, we’ll talk about… that time he nearly had his brain smashed in by a rogue, anti-science apple.

Thanks for listening to this episode.

See you next time. Until then, don’t embroil yourselves with anyone. (Unless you enjoy it.)

Newton III: The Cosmic Dance

If you’re from North America, you might have been lucky enough to see the recent solar eclipse. I’ve never been lucky enough to see totality myself — that shimmering, shining moment before everything goes dark. But I imagine that there’s a sense of wonder when you realize that all of the anticipation of the event has passed, and you’re finally about to witness what you’ve been waiting for.

And then, when the darkness sweeps over the land, I imagine there’s another realization: deeper, more profound. Maybe with a little twist of primal fear from the unnatural sensation of the lights going out. That moment when you realize that — for all our pretentions, for all the grandeur and gilt of the world we’ve built… all the solidity of the stories we tell each other: the stories called society, the stories of employment, the stories of money and the stories of safety and security… all of this could be snuffed out in an instant. The moment you realize there are things in the Universe beyond our control. That Earth is not isolated, eternal, and perpetual — but a miraculous spaceship hurtling through the cosmos. And, more than anything else, as the shadow falls over the land and the Sun disappears, you realize that everything — this delicate scaffolding that we call civilization — rests on our own nuclear fusion generator. Whirling through space with us, a hundred and fifty million kilometres away. We’re locked in a dance with the Sun: and we still will be, dancing through the cosmos together, long after we’re all dead.

But, if, for some unknown reason, we were plunged into darkness — and we no longer had this nourishing light… the thin veneer of that civilization would fall away. Our food would no longer reliably be delivered to the supermarket shelves. Cue mass panic, collapse, and a dark age in more ways than one.

Even knowing that eclipses are temporary, caused by a chance alignment of the Sun, Earth, and Moon — even knowing this, they still have the power to shock, amaze, and even terrify. So it’s no wonder that they were considered such a terrible omen — and also, the occasional presence of this terrifying apparition on the skies motivated us to study the heavens in a way we might not have done otherwise.

The ancient Mesopotamians had it kinda figured out — they had worked out the cycle of times when the Sun, Earth, and Moon aligned. But, as you probably know, eclipses obviously don’t happen everywhere on the Earth at once — and the Mesopotamians hadn’t figured out the geometry of it to that extent.

They didn’t know the mechanics of what was going on: they just had observations, and had noticed the pattern. So they could tell you that there might be an eclipse on such-and-such a date, but they couldn’t tell you where, or for how long it would last.

In 1715, more than 300 years ago, things were aligned in more ways than one. Edmond Halley, the astronomer, had used the new theories of Newton to create an eclipse map — one of the first of its kind. When the eclipse was about to hit Britain, he sold a map that showed its projected position across London. This wasn’t just a quick way of making a buck out of his astronomy career — Halley hoped that his prediction would help people appreciate the advances made by science. Yes, get ready for some terribly formal old English:

The like Eclipse having not for many ages been seen in the Southern Parts of Great Britain, I thought it not improper to give the Publick an Account thereof, that the sudden darkness, wherein the Starrs will be visible about the Sun, may give no surprize to the People,

who would, if unadvertized, be apt to look upon it as Ominous, and to interpret it as portending evill to our Sovereign Lord King George and his Government, which God preserve.

Hereby they will see that there is nothing in it more than Natural, and no more than the necessary result of the Motions of the Sun and Moon; And how well those are understood will appear by this Eclipse.

And, on the whole, the eclipse of 1715 was a triumph: Halley was a few minutes out, but he’d applied Newton’s laws successfully to predict the broad sweep of the eclipse.

Newton’s laws — the laws of motion, and the law of Universal Gravitation — were good enough to put men on the moon, hundreds of years later. And that programme — putting people on the moon — that was what inspired Elton John to write the song ‘Rocket Man’ — which led, inevitably, to William Shatner’s cover of the song, which is arguably the greatest moment in all of human history. They are a triumph of physics — that essentially enabled an entire field, mechanics, to be understood. They have given us extraordinary power, because they allow us to reliably predict things, mathematically.

Humans get by in the world through a sort of direct association between cause and effect. When you’re learning to play football, or cricket — or to walk — it’s really a process of trial and error. You get more data, more information, and you understand that if you move your legs like so, or twist the bat like this, you can achieve the desired result. What we’re doing — in our own, strange, approximate, experience-driven way — is gradually approximating, gradually getting closer to the laws of nature. What Newton did was understand those laws, and write them down using mathematics. This means that we can make predictions about things we’ve never seen: that we can understand the dynamics of stars and planets on the other side of the Universe, as well as in our own solar system — and that we can understand how objects will behave before we invent them. And the laws of motion are valid for a huge swathe of physics — they can describe all kinds of systems. They are deceptively simple: there are whole branches of physics that are almost just applying these laws to different systems.

So, without further ado, Newton’s Laws of Motion — first, as he wrote them in Principia, and then in a translated form.

Law I: Every body persists in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed.

Law II: The alteration of motion is ever proportional to the motive force impress’d; and is made in the direction of the right line in which that force is impress’d.

Law III: To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.

Or, in modern terms:

Newton’s First Law: Objects stay still, or moving in a straight line at a constant speed, unless a force acts on them.

Newton’s Second Law: When a force is applied to an object, it accelerates in the direction of the force, at a rate proportional to the force.

Newton’s Third Law: Action is equal and opposite to reaction.


So what these laws actually do is they give us a framework for understanding how things move. They pretty much define a force — it’s something that can cause a body to accelerate. Newton was thinking of pushes and pulls: the physical forces that you can exert on objects. He was probably also thinking about gravity. But we now know about electromagnetic forces, and nuclear forces, too. Newton’s First Law tells us that, basically, only forces can change the velocity — that’s the speed and direction of movement — for an object. Aristotle, whose word had been law before the 17th century — he insisted that if nothing continued to propel an object, it would eventually stop moving. Of course, this makes intuitive sense in our world — full of friction and air resistance and things that like to stop moving — but it’s not true. Things stop because unbalanced forces act on them. Newton gave credit to Galileo for this one, because — as we discussed in the first episode — he really came up with it first.

Then there’s the second law. The first thing I remember being told when I came into undergrad physics is that Newton’s Second Law is really just a differential equation — and this is the power of Newton’s Second Law, really. We talked about how differential equations deal with how things change, and solving them allows you to make predictions; in the same way, Newton’s Second Law tells you that if you know the force acting on an object — and you can express it mathematically — then it’s just a matter of mathematics to work out its acceleration. Once you have that, you can work out the speed, and then the position: you can calculate where the object has been and where it’s going to go — anything you might want to know about its motion. So this is incredibly powerful. And something complicated, like — a fluid dynamics equation, like the Navier-Stokes equation, which is mathematically impossible to solve without using a computer. This is really just Newton’s Second Law, applied to a moving parcel of fluid. But all this is for another episode!

Newton’s second law often gets expressed as F = ma. Here, we use the algebra convention that two letters next to each other is multiplication: so this is force = mass times acceleration. Which instantly defines this strange thing called mass, which is not the same as weight. Mass is basically a measurement of how much you resist accelerating, when someone applies a force. It’s how difficult it is to push a particular object. These ideas will be familiar to anyone who has accidentally kicked the ground instead of a football. Just me? Maybe it’s a physicist thing.

The Third Law says that action is equal and opposite to reaction. This is easy to misunderstand. But essentially, what it’s saying is that when you push on a wall, for example, the wall pushes back on you with the same force.

By the way — it’s always been a fascinating question for me that turned out to be really hard to get a straight answer to. Why don’t we fall through the floor? Seriously. We know that the atom is 99.9999% empty space, we covered that in our episodes on atomic physics. So why don’t we just fall through objects — when there’s such a low chance of the nuclei of our atoms colliding?

And, also, we’re all familiar with the fact that you can push on objects, and exert forces of your own. But we also know that there are four fundamental forces — electromagnetism, gravity, and the strong and weak nuclear forces. So what’s the force that stops you from falling through your seat, the ‘reaction’ force? Seems weird that the force we’re most familiar with aren’t one of the four fundamental forces.

You can see people give two different answers. It’s either electrons — the electrons in the atoms of your body, and the atoms of the seat — pushing against each other, by electromagnetic repulsion. Or it’s Pauli exclusion — a quantum-mechanical effect that means you can’t force electrons too close together. We talked about this waaaay back in the early episodes on stellar formation — remember neutron stars, that can’t collapse any further because the neutrons don’t like being squished together? This electron degeneracy pressure might also be a part of the day to day forces. You can find people who will tell you both, but it seems like electron degeneracy is more important — although it took until the 1960s, when Freeman Dyson calculated it, to really understand the solution to this problem. Incredible to think that until the 1960s, physicists couldn’t tell you why we don’t just fall through all the empty space in atoms towards the centre of the Earth — and that you need quantum mechanics to explain it!

Anyway: back to Newton’s laws. We have the three laws. Later, these laws would be re-expressed in terms of momentum. It turns out that momentum — the mass, multiplied by the velocity of an object — is a very important quantity. It’s conserved in any interaction. And Newton’s laws, in many ways, are all laws about momentum. The first law says that if no force acts, momentum is conserved for a single object. That is to say, it will carry on going in the same direction, at the same speed. The second law says that force is the rate of change of momentum — how quickly your momentum is changing depends on the forces that act on you. (Newton didn’t appreciate when he wrote it that momentum can change for two reasons: you can speed up, or your mass can change.) And the third law — the one that says action is equal and opposite to reaction — is also just conservation of momentum. Since momentum can’t change overall, forces have to be equal and opposite. Imagine two objects, pushing on each other: if they don’t push in opposite directions with the same force, then you’re getting momentum for free. Instead, the forces are equal and opposite. If one object gains momentum, the other has to lose it. So momentum is conserved.

There we go! Newton’s Laws. On the surface, fairly simple, but a whole world of consequences. And now we have to talk about his most famous discovery of all. So it annoys me when people say that Newton ‘discovered gravity’. I know they mean it as shorthand, but it kinda implies that for thousands of years before Newton, people hadn’t noticed that stuff falls to the ground when you drop it. This is obviously NOT TRUE! The Greeks knew this, for example, and called it “gravitas” — which now means something slightly different. What Newton did was understand how gravity worked — at least, mathematically.

[Newton’s Law of Universal Gravitation Section]

So — this is from the Royal Society, written by a friend of Newton;

“After dinner, the weather being warm, we went into the garden and drank thea, under the shade of some apple trees…he told me, he was just in the same situation, as when formerly, the notion of gravitation came into his mind. It was occasion’d by the fall of an apple, as he sat in contemplative mood. Why should that apple always descend perpendicularly to the ground, thought he to himself…”

So no, the apple didn’t hit him on the head. But yes, there was an apple, or at least, Newton said there was one. I think this is just a poetic way of putting it, to be honest: Newton’s theory of gravity probably didn’t come to him in a flash of inspiration like this. That kind of divine intervention would have appealed to his sense of drama, and maybe his ego, too — but chances are it was a longer process of thinking about gravity and trying to come up with a consistent theory to explain it. Saying that Newton ‘discovered gravity’ really irritates me: of course he didn’t! People knew that things fell down. And, further, they knew that objects in the heavens were moving — after Copernicus, they knew that the Earth was orbiting the Sun. What they didn’t have was a consistent theory that explained why. But it was the motion of the planets, more than the motion of any apples, that confirmed Newton was right.

So, Newton’s law of gravitation, which was published in the Principia, says that every object with mass attracts every other object with mass. It pulls on them with a force. And that force depends on the masses of the two objects times together, divided by the distance between the objects — squared. Now, clearly square numbers get big quite quickly — 1, 4, 9, 16, 25, 36…. So if objects are twice as far apart, the force of gravity is four times weaker. For this reason, the dominant force of gravity for you is the Earth pulling down on you — that’s your weight. The Earth is a sphere, and Newton worked out that mathematically his law meant that spheres act like all of their mass is concentrated at the centre. From outside, it’s kinda the same as if all the matter was a blob in the middle. So you’re actually being pulled towards the centre of the Earth. And, because action is equal and opposite to reaction and gravity conserves momentum too, you are also pulling the centre of the Earth towards you. But the Earth doesn’t really notice, while you are stuck on the ground, requiring aeroplanes, spaceships, and trampolines to temporarily free yourself from the gravitational pull.

Suddenly, with the law of Universal Gravitation, everything made sense. Remember Kepler’s laws? Newton could re-derive them all now. The inverse square law gave you elliptical orbits for the planets, and explained their motions in the heavens almost perfectly. The Sun pulls inwards on the planets, which pull outwards — like if you’re whirling a lasso around, you pull inwards towards the centre to drag it in a circle or ellipse. The mathematics of the orbits meant that equal areas were swept out in equal times — this was because angular momentum was conserved in the orbits. And the time period of the orbit related to the distances in just the right way. In fact, Newton’s law of gravitation meant that by measuring the time period of the orbits of the planets around the Sun, they could map out distances in the solar system. The law of gravitation was an incredible triumph.

F = GMm/r2 — get it tattooed on your chest.


And while Newton was feuding with Hooke over who came up with the inverse square law first — I’m not going to get into that little debate, either; Hooke was working on gravity and celestial mechanics as well, but I don’t know that he got quite as far as Newton did — physics was faced with a problem.

Because Newton’s gravitational law worked incredibly well. It predicted the way the world behaved to within tiny margins of error. It opened up a whole new field of study and understanding; and for most interactions, this law is all you need to understand gravity. It was clearly good physics — it was just so correct; it explained nearly every observation they could make, and stood up to all tests of logic and experiment. But philosophically, it left something to be desired.

This reminds me a lot of when quantum mechanics was discovered, which we’ll cover soon. Essentially, it’s the same problem: they find this theory, mathematically, that explains everything wonderfully and makes amazing predictions. But no one understands why it works. In fact, it seems very illogical. It was maybe only the fact that Newton believed in the occult, and weirdness, and strange things beyond our understanding, that allowed him to come up with the theory of gravity.

To understand why it was so distressing: think about just how weird gravity is. I am attracting you with a gravitational force, right now, whoever you are, wherever you are. You are pulling on the Sun, and Mars, and the volcano Krakatoa, and the Empire State Building, and stars and planets in the faroff distance Universe that you’ve never even seen. Never, ever allow yourself to forget just how weird and amazing this is — it is a way that you’re, in a sense, at one with the Universe, with people you’ve never met, with places you’ve never seen, with neutron stars and strange suns, all feeling your force and sending theirs back to you. How can it be possible that every object with mass in the Universe knows about every other object with mass?

At the time, they didn’t know — as we know now — that gravity travels at a finite speed; the speed of light. So communication of the motion of objects is not instantaneous. On the scales of our solar system, it doesn’t matter all that much. But gravity was still incredibly strange. It didn’t behave like the other forces — there was no obvious reason why there was action-at-a-distance. Everything else seemed to be more obvious: things pushed and pulled on each other because they were touching, or colliding, or maybe because little particles streamed out and physically bashed into things. But what was gravity? Little grappling-hooks that spread between every pair of objects in the Universe, pulling on both of them all the time? Tiny strings between you and everything? Newton didn’t know. And it worried him.

Newton said:

“That one body may act upon another at a distance through a vacuum without the mediation of anything else, by and through which their action and force may be conveyed from one another, is to me so great an absurdity that, I believe, no man who has in philosophic matters a competent faculty of thinking could ever fall into it.”

But he was never quite able to work out what it was that was communicating gravity — why it was that gravity behaved in the way that it did. Instead, he did what the early scientists of quantum mechanics did with the aspects they didn’t like so much; he eventually gave in and said — all that matters is that it works, so it must be true; why can come later (or maybe not at all.)

“I have not yet been able to discover the cause of these properties of gravity from phenomena and I
feign no hypotheses…. It is enough that gravity does really exist and acts according to the laws I have explained, and that it abundantly serves to account for all the motions of celestial bodies.”

In Newton’s defence, as we’ve mentioned, gravity is still a problem. We still don’t know if it’s communicated via particles or not. There are still huge mysteries surrounding gravity; so perhaps it’s not too much of a failure on his part not to understand it in the 17th century. He knew how it worked, and that was enough to ensure his place in scientific history — and send rocket men to the Moon.

Thanks for listening to this episode of Physical Attraction. Next episode, in our final show on Newton, we’ll be dealing with his other discoveries and writings; his dives into alchemy and the occult — his personal life, such as there was one — and that time he was put in charge of printing all the money in Britain.

Newton IV: Mercury, Alchemy, and Newton’s Legacy.

In the last episode, we talked about Newton’s greatest achievement — the Principia Mathematica, which dealt with his laws of motion and the law of Universal Gravitation, which means that you’re all attracted to me whether you like it or not. This episode, we’ll talk about the rest of his life and career, and try to assess the legacy of such an influential physicist. If he was a physicist.

The French writer and philosopher Voltaire, who was in London at the time of Newton’s funeral, said that he “was never sensible to any passion, was not subject to the common frailties of mankind, nor had any commerce with women — a circumstance which was assured me by the physician and surgeon who attended him in his last moments.”

Couple of questions here — how did the surgeon know? Why on Earth is Voltaire, at Newton’s deathbed, saying “Give it to me straight, doc — did he do the deed?” But anyway…

So, you know, if you’re single and anyone asks you why, you can always try to tell them that you’re simply “not subject to the common frailties of mankind”. And, when they’re done laughing at you, you can cite Newton as an influence. This is probably how r/incels was born. ANYWAY.

Since we are a podcast about chat-up lines as well as physics, it’s time to quickly rake up Newton’s personal life before we do the proper thing and focus on his career. Because there is some evidence that he was, possibly, intimately involved with a fellow mathematician — Nicholas Fatio de Duillier. He drifted into Newton’s orbit in the 1690s. At this point, Newton had already published the Principia, and was the closest thing to a rock-star in terms of Natural Philosophers of that era. Duillier was clearly star-struck — I want to pinch a line from H2G2, which is the online encyclopedia maintained by Douglas Adams fans that has all kinds of entries. Please enjoy that guide if you can, it’s like Wikipedia’s crazy Uncle. They comment on the relationship like this:

“There is little doubt that Fatio was starstruck by the older man; a modern tongue might even go so far as to call him a groupie.

there are existing letters between Fatio and Newton that do hint at a romantic relationship, even more than the social mores of the time would usually allow:

‘…the reasons I should not marry will probably last as long as my life’, wrote Fatio, then later, ‘I could wish sir to live all my life, or the greatest part of it, with you.’

Newton responded with gifts of cash and offers of accommodation in or near his own rooms.”

Given Newton’s devout religious beliefs, and the social mores of the time, it’s possible that Newton couldn’t express his true feelings. Or it’s possible that Fatio was just a groupie and while Newton was perfectly willing to display some affection towards people, he didn’t quite reciprocate Fatio’s feelings. Unfortunately, at some point, things went south: Fatio and Newton stopped communicating with each other; Fatio would later have another close same-sex relationship with a quack doctor. And, to add more circumstantial gossip ‘evidence’ to these rumours, we should mention that Newton’s nervous breakdown — which was what led to him sending that nasty letter to his friend we discussed a few episodes back, about embroiling him with women — shortly followed the end of this relationship.

Really, beyond that, there’s not much more you can say. If it is the case that Newton wasn’t celibate out of a sort of monastic choice and devotion to science, but instead because of the social pressures of the time, I think it’s a tragedy. But, unless new evidence comes to light, we’ll probably never know: it’s one for the gossip-mills of history, and, officially, Newton was probably asexual.

There is another reason for Newton’s nervous breakdown that we can point to. After Newton died, it was discovered that his hair contained much more mercury than was normal — around fifteen times the usual sample. He was also contaminated with lead, antimony, and arsenic. It seems likely that Newton’s alchemical studies — attempts to turn base elements into gold — had lead to him suffering from chronic, heavy metal poisoning. The body can’t deal especially well with these heavy metals, and there’s lots of evidence that they can cause brain damage, amongst other things. For example, the expression ‘As mad as a hatter’ has a tragic history: hat-makers used to use mercury in their trade, and it often caused this heavy-metal poisoning. Similarly, someone who is irrational or has violent mood swings is often called “mercurial” for the same reason. And, since I know there are podcast fans listening to this… podcast… those of you who’ve listened to S-Town (spoiler alert!) will remember that this may have played a part in John B’s story, too. Newton wasn’t just inhaling mercury by accident, though — he actually documented over 108 metals by tasting them, which we now know is a wildly unsafe thing to do. We even have evidence, in Newton’s own hand, that he was chomping Mercury: he described the taste as “strong, sourish, ungrateful.” Newton’s nervous breakdown included physical symptoms that are very similar to mercury poisoning; it almost certainly contributed to his instability later in life. Another tragedy.

By this stage, Newton was 55. He had achieved worldwide fame for his achievements in physics and with the Principia. Typically, at that time, notable people would be given a cushy role, or sinecure, as a mark of respect for their careers. Usually, this was to denote that you’d been honoured by the state — it let you draw a nice little salary without doing too much work. Sometimes these positions would be used as rewards by those in power for loyal servants. Newton’s sinecure was being made Warden of the Royal Mint. For those of you who don’t know, the Royal Mint is where Britain makes its currency.

Newton didn’t see this as a cushy job, though — he took his responsibilities very seriously. You have to remember that at the time, and for thousands of years before, the principles of economics that we take for granted today weren’t really understood. This stretches all the way back to the Roman Empire and before. Like us, they have the problem of inflation — the more money you print, the more money that’s in circulation, the less that money is actually worth.

Nowadays, we basically understand that the value of money is a psychological thing. Our coins are made of cheap metals, and we’re happy to use paper notes that can’t exchanged for lumps of gold. In fact, most of our money is — sometimes worryingly — just numbers on a screen. The value of money is something that’s generally agreed-upon. Although, if you’re lucky enough to have a £10 note, you can see that it says “I promise to pay the bearer ten pounds” — it’s an IOU note for the actual gold. If you showed up in your local bank and demanded a lump of gold, they’ll laugh at you, of course, but that was the idea.

Back in the day, though, they didn’t understand that the value of money was based on this common consensus type argument. Instead, people thought, the value of money was based on the value of the metal that the money was made out of. This caused serious problems in the Roman Empire, where cheap emperors would make the coins out of less and less precious metal — called debasement — and there would be a financial crisis as a result, with people concerned that their money was literally worthless. England, when Isaac Newton became head of the Mint, was about to face a similar crisis.

Inflation had meant that, bizarrely, the face value of a coin was worth less than the metal it was made out of. Rather than spending your coins, you were better off melting them down and selling the silver. People would clip the edges off coins to sell that silver, and then spend the coin. Forgery was common — although you did need an actual forge — with people producing debased, low-silver coins. And, to make matters worse, Britain was running out of silver and coins as people melted them down and sold the silver abroad. To cap it all off, they were in some very costly wars with France — and if you can’t pay your soldiers, or they think the coins they’re being paid with are actually worthless… well, there’s plenty of headless Roman Emperors you can ask about that.

Newton had a simple, but radical solution to this crisis. Print more money. You may feel that this is a stupid way to solve a financial crisis, but you have to remember that at the time they hadn’t invented fancy-pants terms like quantitative easing. (Boom take that Keynes!) Recall all of the coins, and issue new ones, with a value that was set by their silver content. You can see that Newton still didn’t understand why the value of currency is what it is, but similar solutions had sort-of worked for problems in the past. Unfortunately, the job of recalling all of a nation’s currency and replacing it by a new type of coin turned out to be a really, really big job.

The issue was that the Mint couldn’t produce the coins quickly enough to replace the ones that had been withdrawn from circulation. 1696 was the height of the collapse; with barely enough money circulating in the system, people were reduced to bartering for goods and services in the old style — seven chickens for my wooden barrel, type bartering. Newton had to get down and dirty in the mint itself, taking up some cramped lodgings in London. In a sense, he kind of invented the much-maligned profession of management consultancy: he went through the Mint’s operations, worked out where the inefficiencies were, and changed things around. Under Newton, the mint went from producing £15,000 in 1690s money to £100,000 and, eventually, fiscal collapse was staved off. He moved the currency onto the gold standard, which helped stabilise things further.

Alongside this, Newton was actively involved in the prosecution of forgers. In the 17th century, forgery was a capital crime, punishable by death. And not just any old death: being hung, drawn, and quartered, which involves a bit of hanging, a bit of intestinal extraction, and then some basic division. Newton personally interrogated some of the forgers — and, when particularly rich people tried to evade justice by bribing the officials and judges, Newton was able to bring some of the forgers to justice. I think his time at the Royal Mint is a good indication of his overall personality, and his abilities: ruthlessly dedicated, single-mindedly capable of pursuing his goals, and extremely well-organized.

Finally, I want to talk about alchemy. In our previous episodes, we’ve mentioned how the study of astronomy was essentially motivated by the superstitions of astrology as much as it was motivated by anything else. People didn’t necessarily recognise the value of science for the sake of science. Scientists would probably argue that they still don’t appreciate the value of pure research today, but that’s another topic… Just as astronomers could convince people to pay them to study the heavens by telling them that, with astrology, they’d be able to tell the future — it was also the case that chemists managed to convince people that chemistry was a worthwhile pursuit by talking about alchemy, the ability to turn ordinary metals into gold.

Newton was fascinated by alchemy. Many of his papers on the subject were destroyed in a fire, but we know that he wrote over a million words on the topic. It’s possible that the fire was intentional, because the study of alchemy was actually illegal in England: and you can see why, too. Since the whole of the currency system was based on the value of these metals, gold and silver — if anyone discovered the secret to changing metals into gold, they’d be unimaginably wealthy and powerful. Alchemy was a threat to national security: so Newton had to pursue it in secret.
What Newton was attempting to find was nothing less than the Philosopher’s Stone — the fabled substance that would allow for these magical transformations to take place. It could turn lead into gold, produce the Elixir of Life that would lead to immortality, and transform an author of books about a boy wizard into a global celebrity and multimillionaire…

Newton had an interest in history, and he wrote a chronology of ancient events; in Newton’s day, they were trying to make sense of all of the documents that had come down to them from the Ancients, unsure Newton also intensely studied the Bible, and was obsessed with drawing the secrets of alchemy, mathematics or physics from the writings of the Bible. He felt sure that, hidden — encoded in the word of God — were secrets that would allow mankind to prosper — or perish. While a lot of people say that he predicted the end of the world to take place in 2060, he actually said that he’d calculated it wouldn’t take place BEFORE 2060 — quite a bold claim — and he also frequently referred to the passage of the Bible that states it’s not for us to know the hour of the second coming of Jesus, so he probably would have thought making a prediction about the precise date would be arrogant.

People often present this alchemy and biblical obsession as a shameful, dark side of Newton’s character — irrelevant nonsense that he also believed in while advancing physics. But this is unfair. For a start, we already talked about how his belief in the occult meant that it was easier for him to accept the weirdness of gravity — a spooky force that can act over any distance — compared to some of his contemporaries. And, in many ways, his theories on light were also influenced by his occult readings. The idea that white light contained all of the different colours of light, and that a prism would allow you to separate them out — this was somewhat similar to the idea that matter contained within it all other forms of matter, and the Philosopher’s Stone would allow you to ‘extract’ the golden part — separate it out — from the base metals.

Alongside the fact that the occult beliefs may have helped his physics, we need to understand the world as it was at Newton’s time. The scientific method was a source of truth, but it was not dogmatically accepted as the *only* source of truth. If you believe that the Bible is the word of a divine being, then surely it only makes sense to search for clues there — a deeper sort of truth.
For Newton — as is the case for many scientists today — his discoveries in physics did not shake his faith in any way. Instead, it was all a manifestation of God’s divine grace.

“The most beautiful system of the sun, planets and comets could only proceed from the counsel and dominion of an intelligent and powerful being.”

In some ways, Newton wasn’t so much a physicist as a seeker of truth. To him, with so much of the nature of reality invisible and poorly understood, all of his studies — physics, mathematics, alchemy, religion — were parts. Patches in the quilt of the Universe, that all contributed to our understanding. In each field, he felt like he was approaching the truth. It was this, above all things — “Plato is my friend, Aristotle is my friend, but my best friend is the truth” that motivated Newton until the end of his days.

Isaac Newton, knighted by the Queen, died in 1727 in his sleep. He had lived a long life, and a good life. He was buried, alongside royalty, in Westminster Abbey. His legacy will always be with us.

What did Newton achieve? He laid the foundations for modern physics. With the principles of Newtonian mechanics, carefully applied, you can calculate all kinds of motions in the day-to-day world. And Newtonian gravity is good enough for us to map out the solar system, and understand how gravity works on Earth, to an astonishing degree of accuracy. Without Newton, it’s likely that others would have discovered his laws — maybe a little from his rivals, like Hooke and Huygens — but it would have taken much longer, and history would be deprived of a towering genius.

Famous economist, John Maynard Keynes — whose theory of Keynesian economics, for better or worse, governs much of how we think about economics in the modern world, had this to say about Newton:

In the eighteenth century and since, Newton came to be thought of as the first and greatest of the modern age of scientists, a rationalist, one who taught us to think on the lines of cold and untinctured reason.

I do not see him in this light. I do not think that any one who has pored over the contents of that box which he packed up when he finally left Cambridge in 1696 and which, though partly dispersed, have come down to us, can see him like that. Newton was not the first of the age of reason. He was the last of the magicians, the last of the Babylonians and Sumerians, the last great mind which looked out on the visible and intellectual world with the same eyes as those who began to build our intellectual inheritance rather less than 10,000 years ago. Isaac Newton, a posthumous child bom with no father on Christmas Day, 1642, was the last wonderchild to whom the Magi could do sincere and appropriate homage.

The inscription on the base of his tomb reads:

Here is buried Isaac Newton, Knight, who by a strength of mind almost divine, and mathematical principles peculiarly his own, explored the course and figures of the planets, the paths of comets, the tides of the sea, the dissimilarities in rays of light, and, what no other scholar has previously imagined, the properties of the colours thus produced. Diligent, sagacious and faithful, in his expositions of nature, antiquity and the holy Scriptures, he vindicated by his philosophy the majesty of God mighty and good, and expressed the simplicity of the Gospel in his manners. Mortals rejoice that there has existed such and so great an ornament of the human race!


Newton, meanwhile, learned the lesson of many scholars. The more you study something — the closer you come to understanding it — the more you realize the vast quantity of what you don’t know. He said of his own life:

“I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.”

And so I wrote him a poem:

The sun rises, and on the beach

there’s a little child gathering shells.

He finds one here, nearby the creek:

he finds another amongst the rockpools.

The prettiest shells he knows by sight;

the ones that will fit in his collection

and arranges them all, by a logic

known at first only to him

which, upon closer inspection, reveals itself

to any traveller who cares to pass.

It could be that the sea-shells, which once

were home to crabs and sea-creatures divine

now chart a map of the stars and heavens above.

Or else the dance of the grains of sand in the wind.

The sun goes down, the child goes home;

the tide comes in, the world turns

but the shells remain.

— — — — — — — — — -

We’re still discovering more of these shells to this day — but, of course, when we do so — whatever small discoveries we can make in physics — we are standing on the shoulders of giants.


Thank you for listening to this episode of Physical Attraction.
Until next time.

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