 Eternity, Time Theory, Variance, Cosmic Dance, Colbert Raport, Wormhole with Morgue, and Freeman's Show, Sean Carragault talking about physics and the meaning of life. I will bring him to the stage with this rhyme, a doctor whose book is all about time. Wait until you hear what he has to say. S-C-A-N-C-A-R-R-O-L-L, Eternity, Time Theory, Variance, Cosmic Dance. Ladies and gentlemen, Sean from the ridiculous to the sublime. Last week I was fortunate enough to find myself in Geneva, Switzerland at CERN, the home of the Large Hadron Collider, watching the experimental physicist there announce the discovery of the Higgs boson. Or at least something very, very much like it. We think it is the Higgs boson. We need more work to tell if it's exactly that. It's certainly very Higgs boson like. It was an absolute pleasure to be at a place where you knew that history was being made. And one way of saying exactly the level of historic import at that moment is to say that in our thousands of years long quest to understand the universe and how it works, the easy part is now over. It's as if we've been sitting watching people play chess or some complicated game like Australian Rules Football, and we finally figured out what the rules of the game are. Now the next step is to become good at playing chess. So my talk is going to be not about particle physics per se, but the hard part of how we understand the universe, the human part. What it means to be a human being in a world that is fundamentally can be thought of as a world governed by the laws of physics. So let's start with epistemology. I know that we always like philosophy lectures at our TAM meetings. How do we know what we think we know about how the world works? So you're outside on a beautiful night. You're admiring the moon with a perspective, romantic entanglement, and you say, isn't that wonderful that we have this satellite that orbits us that has the metallic core and a rocky mantle and crust? And your friend says, well, you know, I've always been partial to the green cheese hypothesis. I think that the moon is made of green cheese. And you say, well, we've been to the moon. We've brought pieces of it back. We can see the moon. We can take spectra of its composition. It looks like it's rock. It does not look like it's cheese. And they say, well, that would be the naive green cheese theory. But the sophisticated green cheese theory says that there are about 10 meters of moon dust on the surface on top of the main body of the moon, which is all green cheese. And you say, well, I'm pretty sure that we've studied enough about the moon to know its density and its rotation and so forth. And it really matches what you would expect from metal and rock and things like that, not from what you would expect from cheese. And your friend says, well, you shouldn't expect that lunar green cheese is just like regular green cheese. This green cheese does exactly that. So what can you do in this case where your friend is being a little bit overly skeptical? How do you escape the threat of just a nihilism that arose any possibility of knowing things? The answer is that you're allowed to say, but you're crazy. What you're saying is absurd. The only thing is that you need to be able to back that up. Why is it crazy to say that the moon is made of green cheese? It's not because we visited there. It's not because we have analyzed it spectroscopically. It's because it's embedded in a larger context. We know something about the solar system and how it was formed. We know what moons and planets basically are. We know what cheese is. It's a dairy product. It comes from cows and sheep and goats and so forth that does not give rise to things like the moon. The point is that when you analyze the truth or falsity of some fact that you would like to understand about the world you do that within the context of a bigger picture. And the biggest picture we have is the fundamental laws of physics, the way that the universe works. And we know how the universe works. This is going to be one of the major lessons that I have here. It's quantum field theory. And what I'm really concerned with here is the everyday universe, the universe in this room right now. I'm not talking about the big bang or dark matter or anything like that. But quantum field theory is the right theory of the world that we immediately perceive. We don't talk about quantum field theory in popularizations of physics that much. We talk about quantum mechanics, particle physics, relativity. But really quantum field theory is the most successful theory we have in all of science. It has been the most precisely tested. It's a very simple idea. Everything is fields. There is no such thing as particles. Particles as XKCD is telling you here are what you see when you look at fields very, very closely. Particles are the particles of matter come from what we call fermion fields. That would be electrons, quarks, neutrinos, and so forth. And there's another kind of field which gives rise to the forces of nature. The graviton comes from the gravitational field, the photon comes from the electromagnetic field, and so forth. So this idea that the world is basically made of fields and the quantum says that when you look at the fields you see particles has been like I said tested to extraordinary accuracy. There's absolutely no evidence that it is in any way incorrect. And it has incredible implications for how we think about the world. One implication is that there are no unknown unknowns in quantum field theory. This is Ken Wilson, another under appreciated figure in physics. He won the Nobel Prize and if you look up the citation it's for a better understanding of phase transitions. But really what Wilson gave us was what quantum field theory really says. How to think about quantum field theory. And Wilson's answer is you think about quantum field theory by looking at length scales separately from each other. If you want to understand things that are happening on one centimeter length scales and above Wilson teaches us that you don't need to know what's happening at length scales shorter than one centimeter. This is an amazingly liberating feature of the world. We don't need to know the theory of grand unification or quantum gravity to know that we understand the everyday world in which we live. This is a simplistic little picture but it gets the idea across. Wilson says basically you have scale, you have distances and the fields have interactions with each other. And basically what we can easily observe are things that exist on large scales with strong interactions. The things that can hide from us are the things that exist on very, very small scales, very short wavelengths, or with very, very weak interactions. So what we know is that the part of the world that is in the upper right hand corner of this diagram is the part we can easily access. Anything that we're missing, it's absolutely possible we're missing all sorts of things but they are all in the bottom left. They are not relevant for what happens to us in the top right. And in particular now we have a theory of the everyday world that is completely successful. Everything in this room consists of three particles arranged in different combinations. Electrons, protons and neutrons. And those particles are interacting with three forces. The nuclear force that holds the protons and neutrons together. The electromagnetic force and the gravitational force that holds us down to the earth. When I wave my hand here or when I speak words, this is all the interaction of the atoms in my body through electromagnetism primarily according to the laws of physics. There is nothing else that we need or will ever need, even a million years from now, to understand what is going on in this room right now. That is a profound fact that does not get nearly as much publicity as it should until today. So historic event. Now you might say but I'm a skeptic, how do you know Mr. Hotshot theoretical physicist that there aren't new particles or new forces that are relevant to what happens in the world? Well, I'm glad I asked that. This is what quantum field theory lets us talk about in a controlled quantitative way. Let's say you imagine there's a new kind of particle. Richard Feynman gave us a way of thinking about how particles interact. You just draw pictures of them. This is a picture of a new kind of particle labeled X interacting with a proton labeled P by some interaction, a known interaction or an unknown interaction. It doesn't really matter. Let's imagine you would like this to be true. Now there are other particles of nature, not in a standard model. There is dark matter, for example, but dark matter doesn't interact very strongly with us. There are probably literally millions of dark matter particles passing through your body every second, but they just don't bump into you. They go right through you. You can't blame dark matter for being hungry or irritable or anything like that. The particles that we know are the ones that interact with you. If there were a new particle that interacted like this then the rules of quantum field theory say we can take this Feynman diagram and rotate it 90 degrees clockwise and get a new Feynman diagram. That would represent two protons bumping into each other like they do with the Large Hadron Collider and producing the new particle. If there were new particles that interacted in any substantial way with us, we would have produced them already and we have not. Therefore they don't exist. Could there be, you say new forces of nature that we're not yet aware of? Again quantum field theory lets you ask that question quantitatively. It says if there were new forces of nature what would they be like? They would have a certain range over which they interacted. They would have things that they coupled to and it would have a strength of the interaction. But the only things there are to couple to are electrons, protons, and neutrons. And therefore you look for new forces with that kind of range and here is an actual experimental data plot. The upper right are the new forces of nature that we know don't exist. We have ruled them out by doing experiments. If you look at the left this is the strength of the force relative to gravity. Gravity is a very, very weak force. I can overcome the force of gravity right here. Watch very carefully. There I did it. Just the electromagnetic force in my body overcame the gravitational pull of the entire earth. What this plot is saying if you can look at the numbers on the left is that on a scale of about 1 centimeter any new force of nature is less than 100,000th the strength of gravity. Completely irrelevant for everyday life. So there are no new forces. There are no new particles that are relevant to anything that happens inside this room until you build a particle accelerator inside this room. For astronomers and physicists other particles are relevant but for you, what are you made of? What do you consist of? What are you really? You are electrons, protons and neutrons interacting through gravity, the nuclear force and electromagnetism. Now we don't need, don't mean to say that physics is finished. There's a lot of work yet to be done in physics. This is what I do for a living. I would not be happy if we were all finished. It would be a little triumphant but we're not even close. We don't understand the big bang. We don't understand dark matter. We don't understand quantum gravity, grand unification, many, many things. However the knowledge we have of quantum field theory ensures that none of those things is relevant to what's going on in this room right now. We don't need to understand them to understand how human beings work as physical systems. Of course we do need to understand the complications that arise when many, many, many particles get together and we don't understand any of that. We don't understand hurricanes, we don't understand economics, we don't understand how to cure cancer, biology, etc. Just because we know the rules of chess, we know how that little horsey thing moves across the board, that does not make us a great chess player. But if we're going to come up with a strategy to become a great chess player, it better not involve the little horsey moving diagonally. We need to obey the rules of the world in which we live and in which we are going to answer all of these questions. If we're going to get sensible answers to anything from economics to biology, they would need to be compatible with what we know about fundamental physics. So our knowledge of fundamental physics has consequences. It has both simple consequences and more profound consequences and one of the litmus tests you can put yourself to is how acceptable are these consequences to you yourself. The simplest one is you cannot bend spoons with the sheer force of your mind because there are no forces of nature that would allow you to do that. The only one that is even close is electromagnetism, so if you could focus electric and magnetic fields with your mind, then you could bend spoons, but there would be much easier ways to test that, iron filings and so forth. Astrology cannot work. There is no force that can extend from those stars and planets to my natural birthplace. With all due respect to the great work done by James Randy and everyone else who debunks people who claim to have paranormal abilities, in many cases you already know ahead of time that they can't possibly be right because the claims they're making are not compatible with the fundamental laws of physics as we know them. Of course it is possible that this one person has the ability to violate the fundamental laws of physics. It is possible the moon is made of green cheese. There are many things that are possible, but if you believe the moon is not green cheese, you should also believe in the standard model of particle physics and all of its consequences. The next consequence is a little bit bigger. There is no life after death despite the photographic evidence here offered. That's because there are no particles and forces that could contain the information in your brain after you die. There is no way for that knowledge of who you are before you died to persist after the chemical reaction that defines your life comes to an end. I'm speaking really here about some sort of extra material spirit that would somehow be you even after your body ceased to exist. That is not compatible with the laws of physics as we know it. We don't need to look carefully at past life regression studies or anything like that. The claim violates the laws of physics. The next consequence is there is no ghost in the machine. What you are is a collection of atoms obeying the laws of nature. You are not a physical meat sack that is being driven around by a little blob of spirit energy like a soccer mom driving an SUV. There is no kind of extra material spirit that drives you around. There are electrons, protons and neutrons interacting through electromagnetism, the nuclear force and gravity. The laws of physics tell us what those things do. It is not necessary to bring anything else into the equation. Finally, there are no externally derived morals or purposes in the universe. It is a feature of the way the laws of physics work that if you know exactly what the universe is at any one moment in time and you had perfect computational power then you could predict what was going to happen in the future and retro-dict what had happened in the past. This is absolutely implausible as a practical matter. It will never ever happen. It's not even worth trying to think about it. But what it means is that the laws of physics are not teleological. They do not tend toward a goal. They just work from moment to moment. You tell me what the universe is now. The laws of physics tell you what the universe will be an instant later. Then they will tell you what it will be an instant after that and so forth. The laws of physics do not care what you do. They do not judge you. The laws of physics do not look upon you and frown at that thing that you did the other day. The laws of physics just happen over and over and over again. So that I think is the hard part. I said that finding the standard model of particle physics was the easy part of our quest to understand the universe. Figuring out how to act within a world that obeys the laws of physics is the hard part. And I'm not going to tell you how to do it by the way. So I hope that you're not disappointed. My goal here is not to say, oh yes, if you just understood the standard model, you would be able to live a better life. That's not going to be quite that easy. What I mean to say is that by understanding the standard model we are now enabled to embark on a quest which will undoubtedly take hundreds or thousands of years to figure out what it will mean to lead a good and fulfilling and meaningful life. But whatever the answer is, it better be compatible with how reality works at a fundamental level. And you might say, you can't imagine an answer to this question. If I can talk about the world as nothing but a collection of electrons, protons and neutrons obeying the laws of physics, if that is the whole everyday world, then how can there be anything else to say? How is it possible to talk about meaning or purpose or right and wrong? And the answer lies in how we talk about the world. The world can be described as particles obeying the laws of physics, but it is not the only way to talk about the world. When you meet someone for the first time and you go on a first date and your date says, tell me about yourself, you do not list the positions and velocities of all the electrons, protons and neutrons in your body. I'm from Caltech. At Caltech that would be considered pretty hot actually, but it's not plausible, it's not really feasible. It's not a useful way of thinking about the world. Now, so what you would do is you would describe yourself in more coarse-grained terms. You would use another kind of vocabulary. You would probably not use the word Adam at all for you non-Caltechers out there. When you described about who you are, what you cared about, what it was that made you you, you would tell some story about who you were. All of the freedom to bring meaning and purpose and right and wrong into the world inheres in that ability to tell different stories about the world. So the poet, Muriel Ruckheiser, put it succinctly as you can. The universe is made of stories not of atoms. Now you might say I just told you the world is made of atoms. This is also true. The universe is also made of atoms not of stories. It depends on how you're describing the universe. What Ruckheiser is pointing to is the fact that we bring reality to life. We give it shape by talking about it in different ways. That might sound pretty thin just talking about a universe that exists, but the freedom to do that in different ways really makes the universe what it is for us. We access and confront the world by telling stories about it. And when I say story I don't mean to say a fictional story. I'm talking about a true story. If you want to gussy it up, call it a theory or a model or an ontology or a vocabulary depending on which department you're talking in front of. But these ways of talking about the world are what we need to figure out to make meaningfulness exist in the world governed by particle physics. So let me give you the simplest possible example of multiple overlapping stories you can tell about the world. Before we talk about meaning and purpose, let's talk about fluid mechanics and thermodynamics because I know that's what you've been itching to hear about. So if you have a box of gas you are allowed to talk about it by listing the positions and the velocities of every particle of gas in that box. That's a complete description. You don't need more information to say what's going to happen. But you could also talk about it by just giving the temperature of the gas, the pressure of the gas, the velocity and so forth, the density as a function of where you are in space. That is another way to talk about it. It is not as comprehensive, its range of validity is not as broad as the language of atoms and molecules but it's much more useful if you want to know is it hot in the room or not. And these concepts we introduce like temperature and pressure are not non-existent. They are real. They are emergent at this higher level of description but the temperature in the room is just as real as the atoms that make it up. In this higher level vocabulary there can even be concepts that are crucially important and real even though they completely don't exist in the lower level vocabulary. So here's an example, irreversibility. This is my favorite feature of the macroscopic world. Certain things happen in one direction of time but never the opposite direction. Bring a hot thing and a cold thing together into contact. They will both become warmer. Bring two warm things into contact. They will never separate and become hot and cold. That is a true feature of thermodynamics known as the second law of thermodynamics. And it has absolutely no analog in the laws of molecules and atoms. The laws of atoms are completely reversible. There is no arrow of time at the level of atoms. That does not mean that the arrow of time that we observe in our world is not real. It's just part of a different way of describing the same situation. So that's the context we need to bring to mind when we start talking about values about what it means to lead a meaningful life, to have purpose in our existence. It is not given to us by the laws of nature. Quantum field theory does not tell you right from wrong. Does not tell you how to lead a meaningful life. It is your choice how to judge things as right or wrong. The story that you choose to tell. What are you going to label as right? What are you going to label as wrong? What are you going to count as having a fulfilling purposeful existence? It is not fixed by the facts of physics. It is in the story that you choose to tell about the physical world. So how do you choose one story over the other? The answer is, well again, I'm not telling you the answer. I'm not telling you how to do it. I'm telling you what we need to take into account when we talk about doing it. And that is we are not blank slates. Human beings do not just pop into existence in the world free of any judgments ourselves. We have goals. We have aspirations. We have feelings. We have desires. We have judgments. And the point is how can we tell a consistent story, a reflective equilibrium that takes our judgments into consideration with those of other people and the laws of nature of the universe in which we live. We need to tell a story that makes sense to us that fits in with the natural aspirations we have and the laws of physics that lets us go to the places we want to go. So I have time for precisely one example. And again, I'm not telling you what is right from wrong. I'm telling you how to think about right and wrong. So here would be two fundamentally different ways of thinking about the problem of should we let same-sex couples get married? A very down-to-earth, real, political question. One point of view would be to say that there is a natural way for human beings to live. There is a right and wrong arrangement of our social order. The right arrangement is to have marriage be between a man and a woman and therefore same-sex couples should not be allowed to marry. And what I would argue is that this is simply a mistake. This is simply wrong. This is based on an incorrect way of thinking about our world. Our world does not have natural ways to be. It does not have right or wrong ways to be. We invent those right or wrong ways. So the second way is that how to live, what is right and what is wrong, is a decision we human beings have to make. No configuration is naturally correct. It is something that we create inside ourselves. We decide how best to guarantee happiness and protect individual dignity. Now with that understanding, you could still argue that same-sex couples should not be allowed to marry. You could say, I think that given who we are as human beings, we should decide not to let that happen. But I would also argue that once you realize that this notion of rightness or wrongness is not given to you by either God or the universe, that it only comes from within ourselves and our attempts to make a just society that is fair to everyone, chances are that you're going to come down on the side that we should let people who are in love get married to each other. As I began with pictures of things in the sky, I have two pictures. This is us. This is a famous picture. This is the pale blue dot. This is an image taken by the Voyager satellite 1.4 billion miles away from Earth when Carl Sagan encouraged NASA to turn it around and take a last parting photograph of us here on Earth. There we are. The universe gave us a little blue circle to live inside. That was very sweet. And the thing to take home from this picture is that we are very small in the universe. We do not take up a lot of space. In just in case this is not sufficient at making you humble, here is the universe. This is the Hubble Ultra Deep Field. This is what you get if you take your camera and you point it at an empty section of the sky and you leave the shutter open for a long time and your camera is attached to the Hubble Space Telescope. You will see that what you thought was an empty section of the sky is in fact alive with all of these galaxies. We live in a galaxy, the Milky Way. Roughly a order of magnitude about 100 billion stars. Every one of these other galaxies typically has about 100 billion stars in it. There are about 100 billion galaxies in the observable universe. So we are very, very tiny indeed. There is probably all sorts of interesting things going on in these other galaxies. Probably there is no Las Vegas anywhere else in the observable universe. But the point is really even though we are small, that's not the point I actually want to make. My point is that despite the fact that we are small in both space and in time we've been doing science seriously for a few hundred years, the universe is 13.7 billion years old, we've figured this out. We know what is going on out there. We know why this light is shining. We know what those galaxies are. There's a lot we don't know and we're working on that full employment for people like me. But we've taken the first steps toward a true, deep, rich, fulfilling understanding of the universe which is knowing the rules of the game. It's now up to us to become good at playing the game, to be good human beings in ways that does not impose on the universe an image we would like it to have, but rather accept the universe for what it is and creates meaning within that universe. Thank you.