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Today, we're gonna talk about how awesome Isaac Newton was, and I want to get one thing out of the way right off the bat. He coined the word gravity. Gravity. Gravity, the force that we all know and love, was coined by Newton. He took it from the Latin gravitas, which means weight or heaviness, so it's not exactly exactly a big stretch of an imagination, to use this word for that force, but he applied it to this force.
And the force, he he basically invented the force of gravity too, but we'll get to that in a little bit. So not only did he invent gravity, he invented the word for gravity. The word could have been anything, but Newton picked gravity, and gravity it is. And speaking of gravitas, if you were to make a list of the top five scientists of all time, Newton is always in the running and often has the top spot. I mean, Newton.
His work is so important that you have to learn it in high school. You can't say the same for Einstein, can you? Who's learning general relativity in junior level physics? Okay. No.
You're learning Newton stuff. And yet comparing scientists is always a tricky game. There's certainly something special about Einstein, and it's why I devoted three episodes to his invention of general relativity and a couple more to special relativity. He was undoubtedly a genius who thought like nobody else did and perhaps nobody since. It's quite possible that without Einstein, we still wouldn't have relativity.
But Einstein was a full time scientist. His work on general relativity itself took over seven years, kind of frustrating years, seven years. And he worked on many problems before that and many problems after that, but all in physics. Einstein's whole life was devoted to science, and it shows he's up there. But neck and neck with Einstein in terms of historical importance and reverence is Isaac Newton who, at best, treated physics like a side hobby.
His main work, which is what we're gonna talk about in physics, took two years to complete, and that was mostly fleshing out the details. The core of his contribution to science was done in a couple of months. I'm not joking. His main contribution to science, the kind of science that you have to learn in high school that forms a core of our modern thinking of how the universe works, was done in a couple months, and it took him just a couple years, just to flesh out some details. Actually, write the rest of the book.
Take that, Einstein. And besides that, Newton spent most of his time not doing any science at all. In fact, science wasn't even a thing back in the sixteen hundreds, at least mostly not a thing. Some people call Newton a scientist or a protoscientist or a physicist or a mathematician, but I prefer to call Newton what he called himself, which is a natural philosopher, a philosopher of nature, someone who is interested in the way the natural world works. Some of those investigations into the way the natural world works resembles modern science, you know, like experimental design or use of mathematics or critical thinking, but a lot of it didn't.
Some of it involved alchemy. Some of it involved the occult. Some of it involved quoting Bible verses. To the eighteenth century and seventeenth century intellectual, it didn't matter. It was all connected.
It was all a part of trying to figure out how the world worked. And so talking about Newton is a lot like talking about Kepler, if you remember that fun episode on Kepler's laws. Man, like, you dig into Kepler and you think it's it's gonna be all about planets, and it turns out it's about, you know, the harmonious music of creation. You're like, wow. I was not expecting that.
That's because we're approaching this with modern sensibilities, and Newton is a lot like that. To us, twenty first century sophisticates, most of the work of someone like Isaac Newton looks like total nonsense. But to them and their contemporaries, it was a very, very important stuff. So most of Newton's work is now a mere historical curiosity. You know, it's like, okay.
He was interested in alchemy and finding the philosopher's stone and transmuting elements into gold. Okay. Whatever. Pass. But a portion of it, and I'm gonna emphasize the word portion, laid the foundations of modern science.
So when measuring genius, it's important to grade on a curve. Einstein was a full modern day professional scientist in how we would consider the term scientist. He devoted his entire lifetime to this this cause. He spent every bit of brainpower in his professional life doing science as we understand it. Newton spent most of his life chasing after counterfeit coinmakers and cooking up ways to get them executed and playing with alchemy and rewriting the Bible and just generally being odd and secretive.
I'm not joking about the whole counterfeit coinmakers. He spent a good fraction of his life as, like, the master of the mint, the royal mint, and it was his job to persecute counterfeiters. Like and he apparently enjoyed it. But Newton, the part time science guy that he was, did twice in his life dip into science in a major way, or at least what we consider science, and he wrote about it. And then he would move on like it was no big deal.
Like, okay. It's just one of the many things I did. Like, how how was your how was your month last month? Oh, it was pretty good. You know?
I I, you know, unlocked some secrets of the universe, and now I'm back to doing something I really enjoy. That was Newton. And so with a tiny fraction of Newton's life, with a tiny fraction of Newton's brainpower, we get the genesis of our mathematical understanding of the entire universe. That is no small feat. So I think if we're gonna be grading on a curve and judging impact versus actual effort expended, I think Newton's gonna win.
And like I mentioned, he did two major works that have relevance to science, have relevance to physics. One is, called optics, which is Latin for optics. And it's it was the second book, and it was published in seventeen o four. And I'm but I'm gonna talk about it first because I feel like like it. The main revolution in optics is that he realized that color is an intrinsic property of light.
So for a long time, we had light from the sun, which is vaguely whitish, I guess. But then we live in a world full of color, of green and brown and black and red and purple. And for a long time, we had thought that color was had to was somehow emanated by the object. Like, it received white light and then created its own light that was this very specific color. That's not too far off, but but what Newton found was the subtlety in that is that white light itself is made up of all the colors, and some of those colors can be absorbed or reflected depending on the object.
And that's how we see the color of the object. It's all sourced from the white light of the sun. And what's amazing about this work and set it apart from previous work was that he got this result through experiments. He developed or invented the prism, and he was able to separate white light into a bunch of different colors. He was able to play with these different colors, and he was able to take notes and study and observation and rule out hypotheses and support other hypotheses.
You would think this would be a pretty straightforward subject, but it was pretty hotly contested. And it was hotly contested for a couple reasons. One is Newton actually presented this work way before seventeen o four, decades before. But Robert Hooke, which was, like, his all time nemesis, argued against ideas. And, apparently, Newton hated debate or criticism.
Seriously, like, if you got into a debate with Newton, he would just get mad and walk away. He would take his ball and go home. And that's exactly what he did with this optics work. He's like, hey. I've got this new theory of color.
And Robert Hooke's like, no. You don't. And Newton's like, well, fine. Bye. And he kept it to himself, unpublished until Hook died, which is the ultimate power play.
Well, now now Hook's not gonna argue against me anymore now, is he? Most of optics, most of this book has now been updated or corrected. In other words, Newton got a lot wrong, but he did get the whole color. Oh, the white light is actually a composition of all the different colors. He got that right.
This book was hotly contested. It was a major source of debate because it was a different way of presenting how we know things. Think about think about how we can know things. Like, how how do we know what we know? When I say to you some random fact, like, oh, white light is actually composed of many different colors, how do we know that?
Well, we can know things from, you know, the teaching of elders, from received wisdom. You know? Aristotle, a couple thousand years ago, wrote about it, and he seemed like a smart guy. So let's just go with what he said. That's not a bad approach sometimes because we don't have a lot of time to work this out ourselves.
So we just trust the experts. Right? Or maybe we try to derive it from first person. We sit here and we think about it really, really hard, and we think, well, white light. What is what is whiteness, and what is lightness, and what is light?
And I'll just think about each of these, and I'll make some arguments. And, oh, maybe there's a useful bible quote that will you know? And and you you come up with some sophisticated argument for why light should be composed of many colors. Or maybe you do it from experiment. Maybe you sit down and you shine a bunch of light through prisms, and you try to understand what the heck a prism is, and you try to understand what's going on and you try to shape the different colors that are coming out and try to understand is it are the colors coming from the light entering the prism or the colors generated by the prism itself?
And you can play with some experiments to figure it out. It seems obvious now, when it comes to science at least, that we turn to experiment and observation, but in Newton's time, this kind of thinking was a new thing. It was a new way of making arguments that we hadn't made arguments this way before, at least not in a systematic careful way. I'm not gonna say Newton invented the experiment, but he did in a very, very careful way when it came to this subject. And like most new things, it was generally despised.
And so that's why something as simple as, hey. I think white light from the sun is made of many different colors, could get people like Robert Hooke upset because Newton is approaching it in a new way. Remember, this was optics was Newton's second book. In fact, Newton's first book was also debated on similar grounds. But unlike optics, most of optics, we we we don't rely on anymore.
We've updated our views on light over the past couple hundred years, but Newton's first book has largely survived. And in fact, it was our main lens through which we viewed the workings of mechanics for over two hundred years. And even after the arrival of general relativity and quantum mechanics and all that nastiness of the early twentieth century, Newton's work is still the main way of understanding nature for almost all the situations you're likely to encounter in your everyday life. Construction, cars, baseball, guns, orbits, movement, it's all based on Newton's work. Newton was the king of motion.
And when you're trying to solve problems in constructions or cars or baseball or guns or orbits, you're not gonna bother with Einstein. You're not gonna look to quantum mechanics. You're gonna look to Newton for answers. 300 year old work has all the answers you need. That's how forward thinking Newton was.
That's how revolutionary Newton's work was. Like, it there's not a lot of stuff that we can point to from work done a few hundred years ago that we still use actively today. It's a very short list, and Newton's on that list. Newton's first book deserves to have its full Latin title said out loud, so make sure you're paying attention. Philosophy Naturalis Principia Mathematica, or in English, Mathematical Principles of Natural Philosophy.
And just from the title, you can see how this is something new. Right? Newton was doing natural philosophy same as all his friends and colleagues and enemies and frenemies and acquaintances. He was figuring out how the universe works just like everybody else, but he was taking a new approach, a radical approach, and in some circles, a heretical approach by investigating the nature of the universe with math. This had precedent.
He was not the first person to do this, of course. Kepler was doing it. Galileo was doing it. I'm sure some philosopher thousands of years ago was doing it, but Newton was doing it in a big way, and he was solving lots of problems this way. And he was making big bold statements this way of saying, hey.
I'm gonna combine observations of the universe with firm mathematical principles, and I'm gonna use the mathematics to enhance and evolve my understanding and to make predictions. That is a new thing in Newton's time in the late sixteen hundreds, early '17 hundreds. That's what got people in a ruckus. When they look at it and they're like, wait. How did you figure this out?
It didn't help that Newton wasn't exactly a great writer, especially when it came to the Principia. This work on the mathematical principles of natural philosophy, it's a it's a relatively dense book. It's hard to follow. The math isn't easy to understand. So a lot of people crack this open and said, what?
What crazy pills are you taking today, Isaac? Go back to catching counterfeiters. You seem better at it. But the book had a few proponents that tried to spread the word, and eventually eventually, you couldn't ignore its ripeness as dense and opaque as it was. It was still right, and it was still good and useful.
And so, eventually, that won out over the course of a couple decades. But you can see why it might have a lot of resistance because it's this isn't how people were used to solving problems in natural philosophy. Newton was doing a lot of math and a lot of new kinds of math, which was just weird. I tried to think of an analogy, like a modern day analogy, but analogies are hard to come by because what Newton's approach was just that radical. It's like if someone came down and say, hey, guys.
I figured out some new, rules of the universe, some some new principles, and, you know, I'm gonna base it on, you know, baking cupcakes. You're like, what? We've been baking cupcakes for a long time. Has this teach us how the universe works? You're making no sense.
You're like, no. Listen. There's, like, whole books on, like, how baking cupcakes teaches us about the universe. It's just it's just new. Right?
It seems odd and probably crazy and most likely wrong, but Newton nailed it. He baked some nice cupcakes. So, anyway, it all started with an apple. It's often told as a kid's story like, oh, Newton, the falling apple. Yeah.
Blah blah blah. We all heard this story before, but it's actually true. I mean, Newton himself said it happened. In 1666, there was this plague, happens all the time. And so he left, Cambridge where he was working, and he went up to his mom's farm.
You know, be a little bit. He self quarantined for a little bit to avoid the plague. He was sitting under an apple tree, and he was thinking big thoughts because he's Newton, and he thinks big thoughts all the time. And he saw an apple fall, And he went, something sparked in that moment when Newton saw the apple fall. We all knew, including Newton, that the Earth pulled things to it.
But what was the range of the attraction? How far could the Earth pull something? You know, is it the tops of the trees? Is that as far as the Earth's pole go? Maybe to the clouds, maybe more.
It's kinda hard to say. Right? Because rain falls to the ground, but clouds don't. Is this because clouds naturally aren't attracted to the earth, or is it because of something else? He pondered it for a while, and he wondered if the same attraction that the earth had to the apple could also apply to the moon.
Does the earth's gravity apply to the moon just as well as the apple? Who knows? He then he went off and did other things for a couple decades because, you know, Newton. Then came a comet in 1680. A big one.
It was visible during the day. It was nuts. Everyone went nuts around the world because who wouldn't go nuts on a big visible comet during the day? It went close to the sun and then it disappeared. And then in 1681, a new comet appeared.
And some other people like, John Flamsteed, who was the royal astronomer at the time in England, he wondered if they might be the same comet. Like, maybe these aren't two separate comets. Maybe we're seeing one comet appearing as it gets closer to the sun, and then it goes behind the sun so we can't see it anymore. And then we get to see it again on its way out. That's not a bad idea.
And this was this itself was a relatively new idea because you just see comets. We have no idea what comets are, where they come from, what they're doing, what they want. And so to see two comets, one comet one year and another comet another year, you might only get like, okay. Whatever. It's just two comets.
But John Flamsteed was like, maybe they're the same. Initially, Newton thought this idea was really lame, and I'm paraphrasing here, but he did get more curious. He got more curious at the time. There was a lot of interest in Kepler's laws of planetary motion. You know, planets move in elliptical orbits.
They carve out equal area and equal time, that kind of thing. These laws were very interesting. Kepler had figured them out a couple generations previous, but they weren't proven. They were based on real observations, but the but Kepler was just like, hey. I found these laws.
I have no idea what they mean, but they seem to work. And so they weren't really grounded. They weren't really proven. Were they really fundamental laws of the universe, or were they just a lucky chance based on a few planets? So, Newton did something cool.
He took Kepler's laws. He took this idea that John Flamsteed had that initially he thought was lame. Conspiracy theory time, Newton knew it wasn't lame, but he said it was lame to discourage John Flamsteed for figuring it out on his own so Newton could get it all the credit. Just putting that out there. There is absolutely no evidence for that, but you know what?
The world has seen stranger things. Newton said it was lame, but then he worked on it in the background. He took Kepler's laws, which had been applied to planets, and he figured out that Kepler's laws could also the behavior of the comet, that these two comets, the one in sixteen eighty and the one in sixteen eighty one were the same comet, and you could explain the path of that comet using Kepler's laws. Intriguing. Right?
This seems like a big deal. This seems like, wow. There is something really powerful about Kepler's laws. It it the first time it's been used to explain something new, Kepler's laws at this point had only been used to explain existing data. This was actual prediction of Kepler's laws, and Newton was able the one to figure out that it worked.
And so in typical Isaac Newton fashion, he put it down, never published it, and went back to working on other things. Around the same time, in the late sixteen hundreds, there were two other major threads of thought that were beginning to bubble up. One of these was this idea of attraction between objects, like maybe the sun attracts the Earth, maybe the Earth attracts our moon, this idea that gravity can extend. People were starting to think about it and talk about it and wonder about it. And they were thinking that there might be this kind of force of attraction between celestial objects that had a particular behavior.
It did extend. It did extend very long range, but it got weaker the farther away you got. And it got weaker in a very specific way. It got weaker by the square of the distance. So if the moon feels a certain level of attraction to the Earth at its current orbit, if you were to put the orbit twice as far away, then that strength of attraction would only be a quarter of what it was before.
And if you were to put the moon four times further away, then the strength of the attraction that it would feel to the Earth would only be one sixteenth the attraction that it feels now. There's this relationship between distance and the strength of the attraction. That's you know, there were a few people, like, starting to have these thoughts and starting to think about it, wondering if there was something connecting Kepler's laws, but not exactly sure where this was going. And the other major thread of thought that was bubbling up at this time was the concept of laws of motion. That maybe, just maybe, that there are some fundamental rules to the universe, and from those simple basic rules, we can explain a lot of behavior.
So it's like it's an extension of Kepler's laws. Kepler's laws, it's it's three rules about how planets work, and it's able to explain the behavior of every single planet in the solar system. That seems kind of powerful. I wonder if we could extend this concept a little bit more. Maybe there are rules that govern how objects move in general.
Maybe there are rules that govern how objects interact. And maybe if we could find these rules and write them down, we might be able to explain a lot. Fast forward three hundred years, this is a this is physics. This is the entire point of physics is figuring out simple rules of how the universe works and applying them to as many situations as we possibly can. But three hundred years ago, this was a new thing.
At the time, a few natural philosophers, you know, buddies of Newton, like Robert Hooke, like Christopher Wren, etcetera, got into a debate about these very important topics of what is the force of attraction, does the force of attraction even exist, are there simple laws of motion. They'd start to bubble up their own ideas and their own thoughts, and so they're beginning to debate about who got it right, what were the laws of motion, what is their force of attraction out there. More importantly, they weren't arguing about who got it right first, because Robert who would be like, well, I wrote down, this square of the distance thingy, you know, in a letter to a friend five years ago, and Christopher Ren's like, well, I gave a talk about the laws of motions to the Royal Society in in five years ago, so I I should get the grad. This is absolutely not how they talked, but it is how they talk in my imagination, so it works. So Edmond Halley, of Halley's Comet fame, was brought in as an impartial judge.
And if your vision of early science and scientists resembles people arguing in a bar, you're not far off. So he went off to ask Newton what he thought. He wanna ask, like, okay. So there's this debate amongst these people, these intellectuals in England about things like loss of motion and forces of attraction. What do you think?
I mean, you're you're a part of this. You know them. Which who's right? And Newton's response was, oh, yeah, bro. Which is a very close approximation of Newton's actual speaking voice.
I totally solved that problem years ago, but, I, lost the notes. Yeah, that's it. Just just give me a couple weeks and I'll, find them. Yep. We honestly don't know if Newton had worked on this already or if he had just vaguely thought about it and didn't really write anything down, didn't have any sophisticated thoughts, and it was only spurred to action because he didn't wanna be scooped by Robert Hooke or Christopher Wren.
We don't know. We don't know. All we know is that that's what he told Edmond Halley. And then a couple months later, he came back to Halley with the core of what would become the Principia Mathematica, and the rest is history. And history started with Newton's three laws of motion, which everybody has to memorize in high school, but nobody gets to learn why they're so dang important.
So that's what I'm gonna talk about. First, like I said a little bit ago, the very concept of a law of motion was something that philosophers have been chasing for a very long time. They believe that there were underlying orders or rules or harmonies, and this work continues to the present day. We call it physics. What made Newton special was that he was the first to get it right or at least close enough to write to make reliable predictions.
And he was able to base this all in mathematics, which makes things so much easier. His first law was that the concept of motion is not a property intrinsic to objects. It was a total oh my gosh. This sounds so simple, but it was a total rejection of all the old philosophical principles, which were they're saying, like, some things prefer to stay at rest, and other things prefer to move. Like, Why does the wind blow, but a rock stays still?
Well, the wind blows because the wind likes to move. It's a windy thing. It's in the wind category of objects, and wind category of objects like to move. Meanwhile, rocks. Rocks are in the earth category of objects, and the earth category of objects do not like to move.
That is how the universe works. Newton realized that moving objects like to stay moving, and things that aren't moving like to stay not moving. The fundamental property of objects that we need to care about is not motion or preference for motion, but resistance to motion, something we call inertia. All objects have a certain amount of inertia. Your resistance to motion.
If you're staying still, it's hard to get you moving. And if you're moving, it's hard to get you to stop. And different objects have different kinds of inertia. Something that's very light won't have very much inertia. Something that has a lot of masses, very heavy, will have a lot of inertia.
This is a huge deal. It completely goes against the common sense notions. It makes it doesn't seem right. Because when I push something, it slows down. Right?
I push it. It goes for all, and it slows down. And so it's natural to say, oh, it slowed down because it doesn't like to move. No. Newton realized, Once it's in motion, it would prefer to keep moving.
Something else is slowing it down. This takes guts to say something like that, to just throw it out. Just say no. You're wrong. And centuries of tradition of understanding are also wrong, and I'm right.
Why am I right? Because of this newfangled way of understanding the universe. That was his first law. That's the yes. But that was his opener.
It's like, boom. Now what? His second law was that force equals mass times acceleration. Force equals mass times acceleration. A simple little formula we all learned in in high school.
This is really conservation of momentum written in a funny way. It is without a doubt the absolute cornerstone of all of physics. Conservation momentum is the bedrock principle that underlies not just Newtonian physics, but general relativity, special relativity, thermodynamics, particle physics, quantum mechanics, quantum electrodynamics, the works. Cosmology, everything. It's important.
Momentum is conserved. Period. Newton wrote it down. Boom. Third law, you shall support Patreon.
Go to patreon.com/pmsetter. I don't know how Newton was able to do this because Patreon wouldn't even be created for another three hundred years. But here we are in the twenty first century with Patreon and patreon.com/pmsutter, and Newton's third law is you should go out and support me if you haven't already. His third law was actually every force has an equal and opposite force. Forces do not exist in isolation.
For example, if I push on a block, that block is pushing back on me. If I'm sitting on a chair, the chair is pushing up on me. Again, this flies in the face of common sense. This isn't how the world appears to behave. Because when I push on a block, I'm moving the block.
What do you mean the block is pushing back on me? Like, if I'm I'm saying moving my couch, I wanna rearrange my room. I push my couch. I push, the couch moves. How are you saying that the couch is applying a force on me if the couch is the one doing the moving?
The way through that is through the force equals mass times acceleration. I'm applying a force on the couch. The couch is applying a force equally on me in the opposite direction, but I have more mass than the couch does. So the couch gets a bigger acceleration than I do. It moves more than I do.
This doesn't make sense. It flies in the face of how we think the universe works, but it's how the world needs to behave for Newton to make the calculations that he does in order to make predictions. And what does he do with these three laws? Well, he introduces one more concept, because this explains all sorts of motion, and now he's gonna go big. He's gonna introduce the concept in Principia of universal gravity.
And to understand universal gravity, we have to go back to his little apple back in 1666 on his mom's farm. When he saw that apple fall, he realized that the apple is falling in a straight line. The apple is accelerating. If there's an acceleration, force equals mass times acceleration, there must be a force being applied to the apple. The gravity of the Earth is a force.
The same way you pushing on something is a force. It's an invisible force and it acts over a distance, but it's still a force. And when you apply the third law, the earth is applying a force on the apple, the apple must be applying a force on the earth. The Earth is pulling on the apple, the apple is pulling on the Earth. Now the apple does most of the moving because it doesn't have a lot of mass, but the forces are still equal.
The apple feels the Earth, the Earth feels the apple too. This force of gravity, and we're gonna introduce that brand new word here in Principia gravity. This force connects every object in the universe to every other object in the universe, and it must have infinite range to explain the motion of objects in space. Gravity really does extend past the atmosphere. It extends past the moon.
It extends past everything. Gravity is universal. Kepler was the first to hope that there was some sort of universal harmony to the cosmos, but Newton was the first one to actually figure it out. He cracked it. And I can't overemphasize how much of a big deal this is.
Universal gravity, same gravity. Unified physics, unified understanding. It's all the same. This is a revolution in our understanding of the way things work. Once you make the claim that this force of gravity is universal, you unlock so much understanding.
And the rest of the Principia Mathematica is a showcase of just how powerful Newton's ideas are. He was able to, using his three laws of motion plus the concept of universal gravity, he was able to explain all of Kepler's laws. Boom. Kepler didn't know where they came from. Newton does.
He was able to explain the behavior of the tides. He was able to explain the motion of the sun. The sun wobbles in it, and it it wobbles about its center. Newton was able to figure out why. He was able to explain the motion of comets.
He was able to estimate the masses of planets. He was able to predict that the Earth is in a perfect sphere. It's actually a little bit oblate. He was able to explain the precession of the equinoxes, the fact that the Earth wobbles a little bit, and it goes on and on and on. He derives Boyle's laws, compressibility, air resistance.
Like, he does it all. Just boom, boom, boom. Just hitting you over the head with example after example of why his ideas are the best. That's what Principia is really about. Three laws of motion plus universal gravity explains just about everything.
So the Principia is uniformly awesome. Why did he get some heat for it? Why was it controversial? It was actually his universal law of gravitation that was the major sticking point. Besides the whole Newton's three laws rejecting centuries of philosophical tradition part, that was, like, okay, kind of expected from Newton.
Like, okay. Fine. You're gonna upend our philosophical traditions, but we're at least willing to talk about it. But this whole, what, universal gravity? The problem was action at a distance.
This concept that the Earth can be connected to the moon without anything physical touching them. Like, how does the Earth actually affect the moon? How does this universal gravity actually work? This is a big question. It's a valid question.
This is what a lot of people got upset about. And this is what we have to be careful because we want to take Newton's work in isolation, or we want to take his fit work in physics and science in isolation from all the rest. But in alchemy, in this ancient tradition of transmuting elements and etcetera, there is a concept of action at a distance, that certain elements can affect other certain elements without actually touching. That concept already existed. And because Newton was really into alchemy, he was able to apply this thinking to something new, something physical, something that applied to our universe, something that was right.
If Newton wasn't interested in alchemy, he may not have had that little bit of knowledge that he could draw from to make a revolution in understanding. So we have to take it as a whole. We have to we can't just discount his work, his nonscience work because it all fed into each other because he's just trying to figure out how the universe works. This this concept of universal gravity is incredibly powerful, but Newton had no explanation for it. Just like Kepler had no explanation for his laws, Newton was able to explain Kepler's laws using universal gravity, but you can say, I don't know what universal gravity really is.
I don't know what's making it do its thing. And he said at the end of Principia, he said gravity must be caused by an agent acting constantly according to certain laws. But whether this agent be material or immaterial, I have left to the consideration of my readers. Yep. It's the ultimate homework problem.
I don't know what gravity is. Why don't you figure it out? All I know is that it exists. And he concluded in a note in a revised version decades later. He said, I feign no hypotheses, which means he's not even gonna try to guess what universal gravity is.
He knows it works. He knows it's powerful. He doesn't know how or why gravity works. He doesn't know what it is, so he's not even gonna try to guess. He's just gonna say, you know, this is as far as I go.
This is where Newton gets off the gravity stop. It wouldn't take another couple hundred years for Einstein to realize what gravity is. It's bending in space time. But Newton was the first one to write down this concept of universal gravitation, which itself was a massive revolution in understanding. By the way, did I mention that in order to do this, you know, all this applying the laws of motion and universal gravity to solving all the problems in the universe, he had to invent an entire field of mathematics.
In his spare time, Newton invented calculus. An entire way of solving problems in order to solve the problems that Newton needs to solve. He's like, man, I can't crack this with the existing methods. I guess I'll invent a new mathematics just to get it done in his spare time. Why is Newton a big deal?
Because he basically invented modern physics when nobody else could. As for Newton himself, we have millions of words of surviving books and letters and documents and notes. His mind went in so many places and so many directions that it's almost incomprehensibly powerful to us, And I hope I've been able to explain that today of just how outrageously smart Newton was, that in his spare time, he started modern physics, laid all the groundwork we need, and was able to explain so much about the universe. But according to Isaac himself, he said, quote, 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 seashore and diverting myself now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me. Whether that's genuine humility or the world's greatest humble brag, I don't know.
So we'll just leave it as it is. Thank you to Chris c for today's question, today's episode. And, of course, thank you to my top Patreon contributors this month, Matthew k, Justin g, Justin g, Kevin o, Duncan m, Corey d, Barbara k, Newdredr, Chris c, Robert m, Nate h, Andrew f, Chris l, John Cameronell, Nalia, Aaron s, and Kirk t. It is your contributions, all of you. Patreon.com/pmsutter.
That keep this show going. Speaking of keeping it going, send me questions, hashtag ask a spaceman. Find me on social media at paulmattsutter. Go to askaspaceman.com. Email askaspaceman@gmail.com.
Go read my new book, How to Die in Space, coming out soon. And I'll see you next time for more complete knowledge of time and space.