as Sean Carroll and I brought this up here so I wouldn’t mess this up he is the senior research associate in the department of physics at the California Institute of Technology here we go thank you this is working you can hear me there in the bank science this is working so it’s a great pleasure to be here at skeptic on when they asked me to come there is a nice thing where they don’t tell you what to talk about you can talk about whatever you want for me was easy because I have a book coming out next week but you can pre-order it now if you really wanted to it’s about the Higgs boson and the Large Hadron Collider and the search for this elusive elementary particle but because it is skeptic on I also wanted to give it a different little bit of spin here not just talk about the Higgs boson but put it in a perspective about where this is where the fundamental nature of reality part of the story comes in how it fits into a bigger picture of what we know about the universe and what we will know about it going forward and how we make use of that knowledge so I was fortunate enough to be there in Geneva on July 4th of this year at CERN the European particle physics Center where people camped out overnight to get into a couple of PowerPoint presentations early in the morning on July 4th and of course the reason why they camped out was because that these PowerPoint presentations from the two different experimental collaborations at this laboratory were announcing an amazing discovery the discovery of a new particle a new piece of nature the Higgs boson it wasn’t just the people in the room or the people waiting there were hundreds of thousands of people watching on livestream I was actually there in the capacity as a journalist not a scientist and so I was in the journalism room surrounded by other journalists even though I’m not a journalist myself and when the announcement was finally made the journalism room erupted into applause which if any of you are journalists you know that’s not what you’re supposed to do at news event as a journalist but people got very excited and so the question that you’re allowed to ask is what is the big deal why were people so excited about this and what I want to do is give a very brief overview not to actually answer the question but to first convince you people who are really excited this was something that a lot of effort went into so the Large Hadron Collider is the particle accelerator outside Geneva under the ground it crosses the border of Switzerland and France that we’ve spent a long time building is the world’s largest particle accelerator ever built it’s part of this CERN complex and the numbers stagger the mind the so just to give you some of the numbers it’s 27 kilometers around it’s a hundred meters underground so if you’re walking on top of Large Hadron Collider it looks like you’re on a farm there’s Hills there’s cows underneath three hundred and some feet particle physics is going on it costs about about nine billion dollars to build a thing it’s hard to count because there’s ongoing expenses and there’s different accounting systems but it’s not very inexpensive it’s not a tabletop device about ten thousand people are involved currently with the LHC inside this ring you have protons moving faster than this they’re moving at 99.999999% of the speed of light which is very very fast and to do that you have six thousand tons of magnets moving them around the reason why the LHC and other particle accelerators are big is not because at every point they’re accelerating the protons there’s only one point on the ring where they accelerate the protons the bigness of the Ring is because you have to steer them the amount of energy in the proton beam at any one time is about the same as the kinetic energy in a freight train moving at a hundred miles an hour so you have six thousand tons of magnets just steering the protons in this circle and that takes and there it’s all cooled to a temperature below that of empty space if you were out there in the universe the Cosmic Microwave Background would warm you better than being inside the magnets at the LHC 275 thousand kilometers of cable and you know it could go on and on it’s a big effing deal the LHC and it was not easy to make it you have to steer your equipment in between little streets in these villages of the mountains of France you have to lower these magnets down with a few centimeters of clearance on either side into the tunnel once you start excavating a new tunnel for your experiment you realize holy crap I’m in

France and that means that there are Roman ruins where I’m trying to excavate from the year 418 so I have to stop everything for six months to excavate the Roman ruins and occasionally your accelerator blows up so this is a picture of a there was a terrible disaster just 10 days after the LHC first turned on where one of the magnets blew up and it then spread to other magnets it was it was put out in the news release as a leak but if you’ve been standing next to it you would have been dead because it was actually quite several tons of liquid helium were explosively released into the environment but and here’s the broken magnet afterward but the CERN people working on the LHC picked themselves up immediately did amazing technical feats and got it all running so there are two giant detectors Atlas this one that looks like a spaceship CMS that looks like some weapon of some sort all of my references are from Hollywood movies that’s all I can point to and they’re very big to show you how big they are there are people in each one of these pictures there’s a person there’s a person these are not tabletop experiments they would kind of fit into this room that we’re in right now they collide protons together there’s over a hundred million collisions every second and the amount of data that is actually kept from a collision is about a megabyte so you can do the math you’re filling up over 15 million gigabytes of data being written to tape or to disk every year and you say well a gigabyte is not that big I have many gigabytes on my computer but this is 15 million of them so it’s not just like there’s a bunch of Macintosh MacBook Pros hooked up they’ve invented new ways to do the information collection and storage not every piece of the LHC is overwhelming in its size and awesomeness this little thing that looks like a fire extinguisher is where all the protons come from the protons come from hydrogen which you then shake to get the electrons to leave the protons and then you fill up the LHC and there’s a hundred trillion hundreds of trillions of protons in the LHC at any one moment which is a lot of protons but it’s not a lot of protons compared to you and me this little canister has enough protons in it to power the LHC for tens of billions of years we don’t have the funding to do that but we have the protons what happens the protons smash together and usually crack comes out just a whole bunch of particles that we already know about those are not interesting and we throw them away the overwhelming majority of data that is produced at the LHC is instantly erased because we can’t keep it fast enough we have a we I say we in the sense that my friends people who I know that a hard-working experimentalist at the LHC have figured out what’s called a trigger to very quickly look at the events that are generated Desai was not they might be interesting and if they might be we keep them so here’s an event at Atlas this is not a simulation this is the real event protons smash together a whole bunch of junk that is happily colored white comes out but in also these two little short lines or electrons and these two long lines are muons and they’re extremely high-energy these electrons and muons and that’s exactly what you would expect to come out if you had made a little Higgs boson in your detector the problem is things like this can also come out even if you did not make a little Higgs boson in your detector so there’s a whole bunch of effort that goes into picking out the signal over the noise Higgs bosons are created and they instantly decay the lifetime of a Higgs boson is about a Zepto second not gonna tell you how short that is but it’s really really short you never see the Higgs bosons in your detector they instantly decay into something else and because of a little thing called quantum mechanics you don’t know what it’s going to decay into you can only talk about the probabilities so we’ve used our theory to calculate the probability of the Higgs boson decaying into different things bottom quarks and their anti particles W plus and minus bosons etc so we know what all the different possible things could be produced if you’re making Higgs bosons and then you go looking for them and the problem is that all of these things can also be produced without making Higgs bosons so what you’re looking for is the statistical deviation from the predicted number of produced particles you’re not looking for a special kind of event because every event there is can be made without Higgs bosons you’re looking for an excess number of events of a certain type so often people say it’s like looking for a needle in a haystack but that’s actually not right it’s like looking for hay in a haystack it’s like trying to verify there’s a few more hay

stalks of a certain fixed length than you would ordinarily expect given the statistics of haystacks as you have experienced them in your life many many highly paid and dedicated and hardworking physicists have set themselves to doing this problem and here is what your nine billion dollars gets you as I mentioned I wrote a book about the Higgs boson coming out next week you can pre-order it did I say that the one plot that I had to fight to keep in the book was this there’s all these pretty pictures of like you know people and equipment and atoms and stuff and they said no this is scary you can’t include that and I said we paid nine billion dollars for this we should include it yeah okay that would work what is this this is a number of events that appear in your detector as a function of the energy of the event and this is M gamma gamma gamma is for some obscure historical reason what particle physicists call photons so this is just you smash your protons together you see two photons coming out with incredible energies you use e equals MC squared to convert energy and mass and back and forth so you treat energy and mass is the same kind of thing and then you say how many events are produced when the two photons coming out have let’s say a hundred and ten GeV of energy GeV is a Giga electron volt billion electron volts I’m also not gonna tell you what that is except that the mass of the proton is about one GeV so we’re talking about energies of our photons coming out that are that could not possibly be produced by protons at rest there’s not enough energy there these are high-energy protons they’re producing these photons you make a plot and you see a bump you might not have seen the bump if they didn’t color in the the helpful red line with a bump there because the bump is very hard to see but here’s an arrow pointing to it look there’s a bump right there and there’s a bump right there why are there two plots because there’s two different experiments that do essentially the same thing that is absolutely absolutely crucial as I don’t need to tell anyone in the skeptic on audience it’s not enough to have one remarkable thing happening you did verify it need to test that you’re on the right track so having two experiments that do the same thing is what helps us believe that we’re not actually cheating so what you see is this bump and what does that mean that means that when your protons came together it’s easy for them to produce two photons but if there was a new particle with a mass of 125 GeV that particle will be produced and then decayed and you get a few more events with the total energy of 125 GeV than you would otherwise expect and that few other events you can see how many more there are a few dozen maybe is the evidence that there is a new particle here with a mass of 125 GeV so that is all just to convince you that we are excited we have spent billions of dollars tens of thousands of people have devoted their lives to this the LHC was first conceived in the 1980s and was first starting to be built in the early 1990s so literally people have devoted much of their professional careers to this machine to get these bumps so you’re gonna say who cares why is it worth nine billion dollars to build this incredible technological I mean it’s impressive when you go and visit you will be overwhelmed was it really the best thing we could have done with our nine billion dollars so my task is to try to explain to you the importance of the search for the Higgs boson I haven’t even really told you what the Higgs boson is yet that will come along the way but I want to admit it is difficult to explain why the Higgs boson is important many of my friends are pulled up by reporters and you know TV crews and so forth please explain why the Higgs boson it’s worth nine billion dollars and we haven’t really polished our answers to that yet it’s gotten so bad that we invented a term that I’m not going to use here but it’s an attempt to convey to the outsiders exactly how important this new particle of nature is we’re gonna try to do better than my friend Leon Letterman here’s the secret the Higgs boson is not all that important that is a bit of a disappointment I know but it’s only temporary as you see there’s still plenty of space here what’s important is the Higgs field from which the Higgs particle is produced and this is just as true for every other particle of nature but the fact that it’s the field that’s important not the particle is only really crucial when you talk about the Higgs boson so we need to explain quantum field theory how much time do I have do I have we’ll have another three months to talk

here’s that okay so we’re gonna explain quantum field theory it’s a true fact of nature that when we talk about particles of nature we’re just being sloppy particles are not what nature is made of despite the fact that we call this particle physics what nature is made of is fields and it’s another remarkable fact that we don’t tell you that that as physicists popularizing our subject we talk all the time about relativity we talk about quantum mechanics we talk about particle physics we talk about string theory and the multiverse and the anthropic principle but we’re all thinking about quantum field theory and we don’t tell it to you so quantum field theory is the central organizing principle of modern physics I can get by in my life as a physicist without telling it to you but I cannot get by in my life as a physicist without learning it and using it all the time quantum field theory is the reconciliation of special relativity with quantum mechanics and it is the best idea we have about understanding the world at a fundamental level right now it might not be true as scientists we always know that there could be better and better approximations to how reality really works but there’s absolutely no experiment that has ever been done here on earth that even hints the quantum field theory is not correct so there’s a lot of books on it you could read those or you could listen to the next ten minutes and I will tell you what quantum field theory really is so in some sense quantum a field is the opposite of a particle a particle has a location here’s a picture from a bubble chamber of tracks left by particles as they move through space and you see that there are lines there was a particle there and then there and then there and then there a field is the opposite a field doesn’t have a location the field exists everywhere and it has a value at every location so a particle exists at one point a field exists everywhere and you are familiar with this here’s a magnet you can put iron filings around the magnet they trace out the lines of something called the magnetic field a magnet is something that has a field that that extends all throughout space and you’ve heard these words and you’re familiar with them but they are still kind of surprising I like to quote my friends in the insane clown posse am I am I allowed to say this so they had a song that you may have heard they can bleep it out in post the Insane Clown Posse hip hop duo with the clown makeup they had a little song called miracles that was explaining how miraculous everything around them was and at some point they said the famous line magnets how do they work we know how magnets work so we were happy to explain that but I want to stand up for my buddies in the Insane Clown Posse because magnets are still pretty awesome okay you know you stick the magnet to a piece of metal and it sticks and you’re like alright that that’s cool but you have to understand other sticky things stick because they’re touching you stick a piece of paper or stick of a piece of silly putty or something like that you touch it to the thing and it sticks there but if you put the magnet there it begins pulling before it actually touches how does it know that it’s next to something it should stick to before it touches it and the answer is that there’s a field that you don’t see it with your eyeballs but stretching out in between the magnet and the metal there is a field that is being affected by both the magma in the metal and it pulls things together how does the laser pointer know to fall down it’s because there’s a gravitational field this was a really hard problem for a guy you might have heard of called Sir Isaac Newton it’s not just the Insane Clown Posse who worried about this how is their action at a distance how does the earth and the laser pointer communicate and now we know the answer there is not a distance between them there’s a field that fills space at every point in space there’s a field called the gravitational field and this is just responding to that gravitational field at every point in space there’s a field called the magnetic field at every point in space there’s a field called the electric field at every point in space there’s a field called the neutrino field there’s a field called the up quark field every particle every piece of reality that you’ve heard of is ultimately coming from a field so quantum field theory says that literally everything is just some kind of wave in some quantum field or another here’s xkcd when we observe them they become ember particles of grain you’ve heard about waves versus particles and if you took just enough but not quite really enough physics education you know that there’s this complicated question our electrons or

photons they really waves or they really particles and there are many people in the world who’ve heard that question and still haven’t known what the answer is and the answer is they’re waves that’s the right answer it’s not a debate we know which is right and which is wrong the world is made of waves so why do we ever think that there are particles that’s the miracle of quantum mechanics that’s why it’s quantum field theory not just classical field theory quantum mechanics as the one you see when you look at the world is much much less than the world really is what the world really is is waves but when you look at it you see particles what the electromagnetic field is is a way both electrical and magnetic through space at every point there’s some value of the electric field the magnetic field but when you look at it closely enough it resolves into particles called photons that’s also true for all of the particles that make up this podium or the floor or you or anyone you like or don’t like in the world they are collections of vibrations in quantum mechanical fields that’s it for the whole quantum field theory lecture I hope that was helpful why do we think this why is that the way the world works well the very fact that we can make Higgs bosons by colliding particles together is evidence of four quantum field theory being right if it weren’t for quantum field theory you would describe the world as the individual particles and the problem is if that were true you could tear apart collections of particles into their individual constituents but that’s all you ever do when you make a Higgs boson by particles colliding together you’re not releasing Higgs bosons that were hiding inside the proton you were creating Higgs bosons anew for the very first time how are you doing that because the quarks and the gluons inside your proton are really vibrating waves and when they collide at high energy they start another wave vibrating and that wave becomes the Higgs boson so the creation and destruction of particles is something that only makes sense if the world is really made of fields fortunately it is so we can make new kinds of particles when we were making that Higgs boson it’s not yeah there’s that the conventional story is it’s like you take two wristwatches and collide them together and watch all the pieces come out that’s not right that is very very misleading it’s like you you smash two time X’s together in a Rolex comes out a whole new kind of thing is created when you do these high-energy particle collisions so an example you can hold on to is if you play a piano and you guys happen to have another piano sitting next to you if you play a note loudly and you listen very carefully the strings on the other piano will begin to vibrate the note from one piano can travel through the air and it will affect the strings on the other piano which will begin to resonate because the fields which in this case are the strings of the piano are connected to each other through some kind of interaction so that’s the world as physicists understand it right now a bunch of fields interacting with each other transferring their energies back and forth so to lay some science on you here here is a Fineman diagram and the way to understand what this diagram is telling you is to read from left to right as time goes on you go from left to right and there’s sort of a particle e language or a field e language you can attach to this cartoon there are gluons the particles of the strong nuclear force that hold the quarks together they can merge together to make a top quark which then spits out a Higgs boson which then decays into bottom quarks and anti-bot em quarks but what’s really true going on I’m revealing to you here is that these are waves in the gluon field and they interact with each other and set up a wave in the top quark field and that converts into a wave in the higgs-boson field which eventually converts into the waves in the bottom quark fields every one of these particles that we see in our detector is just what quantum mechanics lets us perceive of the underlying reality which is fields so by using experiments we’ve now been able to complete what we call the standard model of particle physics and here it is this flow chart there’ll be a quiz at the end so take out your smartphones now and start snapping so it’s it’s actually much more easy to understand what’s going on in the flow chart a glance of the flow chart would lead you to believe there’s only two kinds of fields in nature fermions and bosons are the technical terms what they really are are matter fields and force fields the matter fields the fermions have the simple property that they only vibrate a fixed amount which is interpreted in particle language as you can only have one particle in a place at

any one time the reason this podium is solid the reason why doesn’t just collapse in on itself it’s because the electrons in the atoms that make up the plastic molecules of this podium take up space because they are fermions if you go through the flowchart do you take up space yes you’re affirming on you interact with a strong force no you’re a lepton if you have an electric charge yes it’s minus one you are an electron you could be a muon or at Al but those were just decay into electrons pretty quickly the boson fields can oscillate wildly that’s what they can do they can oscillate as much as you want that means the particle language you can pile bosons on top of each other that’s why the earth can pull down this laser pointer even though the gravitational field is so weak the earth is made of a lot of particles so the gravitons are created in enormous numbers and can reach out and tug on the laser pointer so if you pile on your boson are you non-zero an empty space will get there what force do you carry gravity your graviton so those two kinds of particles make up everything that we have ever observed in any experiment ever done that’s a very impressive story and let me I’m going to say that that fact at least two more times just to drive at home into your head everything every particle every field every phenomenon of nature that you personally have ever seen or heard or smelled or touched or tasted I didn’t include taste but taste also counts in your life is some aspect of the standard model of particle physics in fact if you’re not a professional physicist it’s only a small fraction of the standard model that is even relevant we have neutrons and protons that are made up of quarks two downs in an up make up a neutron two ups and down make a proton this is a deuterium nucleus heavy hydrogen one proton one Neutron there’s an electron moving around it the quarks inside the proton and neutron are held together by the strong nuclear force gluons the electron is held to the proton by the electromagnetic force photons and the whole shebang is pulled down to the earth by gravity those are the only ingredients you need to describe everything you’ve ever seen if your professional physicist or an astronomer maybe you’ve also interacted with some muons or neutrinos or something like that those are also in the standard model so this picture right here is the 99% story of the universe of your everyday life not of the universe of your everyday life the hundred percent story is the whole standard model there’s no experiment we’ve ever done that requires physics other than the standard model here on earth it’s out of these particles electrons up quarks and down quarks and the forces that hold them together that the podium is made of that I am made of that you are made of every thought you’ve ever had every person you’ve ever loved is a dance of these particles interacting with each other according to these forces so why do we need a Higgs boson the whole point is that the standard model is enormous ly successful it fits every experiment we’ve ever done here on earth again space is different but here on earth the standard model reigns supreme why do we need the Higgs because without the Higgs field the hague the standard model would make no sense it would not work it would not fit the data it would describe a world with that world would not be our world at all so here this is the one slide on which you’re allowed to get completely lost I’m going to try but if you get lost I’ve given you permission ahead of time the thing that makes you’re already lost I didn’t even start yet hang in there the thing that makes the Higgs field different from all the other fields is that if you go out into empty space if you make a little region of space out there in the interstellar vacuum so it says empty is empty can be there’s no radiation no dark matter anything like that and you say you make the minimum energy that the universe can have in that little cubic centimeter and you say well what are the fields doing in that cubic centimeter well all the fields are set to zero right if you make a magnetic field if it’s zero it has zero energy if it’s nonzero it has some positive amount of energy and all the other fields work like that so this cartoon on the left is trying to tell you how does the energy change as I push the field away from zero the magnetic field or the electric field are zero there’s zero energy as I increase them it costs energy I need to put energy in to make that happen so far so good yeah no we have a tough crowd here tonight folks the Higgs field is different because the minimum energy thing that the Higgs field can be doing is not sitting at zero if the Higgs field were sitting at zero it would have

more energy than it does stuck outside at some other value the difference between the Higgs field and every other field in nature is that the Higgs wants to be nonzero even in entered empty space even if its lowest energy configuration so here’s a different plot this is now space and this is now the value of the different fields you have all the different fields that make up nature electromagnetism quarks gluons etc they’re all almost zero but there’s small vibrations around zero the Higgs field is not zero in empty space it sits out there when you move through space when you breathe if you are a particle traversing between galaxies you’ll be moving through the Higgs field you’re not moving to any of the other fields they’re close to zero but the Higgs field is everywhere it’s like the fish in the water you don’t notice it but the Higgs field surrounds you all the time the Higgs boson particle is a little vibration in that Higgs field and what that does is that it affects the behavior of all the other particles that are moving through it every particle that you’re made of feels that Higgs field you don’t notice it because it’s just what you were born with but there’s a big difference between a world in which there were no Higgs field in a world of which the Higgs field is all around us the elementary particles the electrons and quarks and so forth without the Higgs they would all move at the speed of light they would have zero mass Einstein says that particles can be massless like the photon or the graviton but if so they have to move at the speed of light fortunately for us electrons do not all move at the speed of light because otherwise you could not make atoms for example without the Higgs every electron would be massless and zipping by this without the speed of light with the Higgs if you can see the little the Higgs in the background there the electron keeps bumping into the Higgs field as it moves through space and that gives it some heft that gives it some inertia it gives it some mass and what that does is the Higgs field is kind of like Ritalin if you imagine trying to organize a bunch of unruly kindergartners we’re running around very very fast you’re trying to calm them down and have them do some interesting tasks that they’re all moving it you know the speed of light practically for all intents and purposes if you if you give them something that slows them down and lets them do interesting work that’s what the Higgs field actually does it makes particles of nature slow down join together form complex structures like you and me and what that means is that without the Higgs field electrons would be massless there would be no atoms an atom happens when an electron joins up with a nucleus and those atoms can join together to make molecules but if the electrons are moving at the speed of light they would never get stuck to a nucleus they would just zip through space all by themselves the world would be devoid of anything complicated it would just be particles moving at the speed of light all throughout space fortunately with the Higgs everything slows down you can explain atoms you can explain molecules you can explain everything we have ever seen in any experiment we’ve ever done that is the significance of the finding of the Higgs boson it completes a theory that is the complete theory of the everyday world there’s plenty we don’t yet understand but with the Higgs boson found we now have a theory that is in 100% agreement with everything around us right now here in this room Democritus would be happy Democritus the philosopher from ancient Greece known as the Laughing philosopher because he was laughing cause he was like hahaha it will take you 2,500 years to prove that my idea about the atoms is on the right track Democritus had this idea that that despite the wonderful variety of stuff around us in nature it was kind of like Legoland it’s a wonderful variety of things made out of a few simple pieces which he called atoms and now we have his pieces the standard model of particle physics so the laws of physics underlying everyday life are completely understood and the reason why I emphasize this is because scientists and skeptics for that matter love to go right to the unknown things there are many many things that are unknown from dark matter to quantum gravity to finance ok but there are also things that are known and among the things that are known or how the matter around us in our everyday life actually works and it’s not just we have a theory that works it’s better than that we know that there are no new parts of nature that we haven’t found yet that could exert a substantial influence over our everyday lives there are no new particles or for

forces that could be relevant to your everyday life that science hasn’t found yet and that’s a much more dramatic claim that I’m gonna try to justify just a little bit so this guy Ken Wilson is one of the unsung heroes of 20th century physics you might have heard of Albert Einstein Richard Fineman Stephen Hawking Ken Wilson made an absolutely central contribution to our understanding of quantum field theory because what he explained to us is that quantum field theory is organized by scales by lengths he invented what he perfected really what we now call the renormalization group not gonna tell you what that is but basically it’s a way of saying if all I care about our objects bigger than this I don’t need to worry about the details of what’s going on on distances smaller than that this is what makes physics possible as a practical discipline you don’t need to know string theory to understand chemistry you can understand how atoms work and you don’t need to know if there’s anything that the atoms are made of you don’t need to know atomic physics to do biology you can do biology in its own right if you don’t care about the individual pieces it’s made out of you don’t need to know biology to do economics or sociology or so forth so this is a a good way of thinking about the world dividing it up into a hierarchy of scales Wilson made it rigorous and mathematical in the case of quantum field theory he said let’s think about different fields that could have a different range if they’re very very massive they’ll be short-range if they’re very light they will be long-range and let’s think about how strongly they interact with other fields so you have a nice division into the upper right in the lower left the upper right is the part of nature that is accessible to us if things existed long enough distances and interact with us strongly enough we will notice them whether it’s quarks and gluons or electrons and gravitons but you can hide things from us in quantum field theory and we know how to do it this is the important point there are ways to hide things but there also ways to not be hidden if something is long-range and strongly interacting if it’s up here we would have noticed it there is no way we could have failed to notice it because we’ve done the experiments required to figure out what the quantum fields could be doing here which means that the known knowns in Donald Rumsfeld’s famous formulation are all up here in the accessible region both the known unknowns and the unknown unknowns are down here in the inaccessible region there’s plenty of room for new physics and surprising phenomena that we have not yet discovered but what Wilson is telling us is that you don’t need to know it to understand how atoms work to understand how molecules work to understand how the human brain functions for example and we can make this cartoon very very specific if you believe quantum field theory and of course you might just disbelieve quantum field theory you might believe all sorts of things but if you believe quantum field theory which is our best tested physical theory of all time then there are tight constraints on what new kinds of particles can exist you might say well how do you know there’s not a Zil BOTS particle that you just haven’t noticed in your experiments yet maybe the Zil BOTS is very important because it comes in and it interacts with your brain and gives you thoughts and freewill and feelings and then it goes on its own way maybe you’ve heard people say things like that so that has meaning all of these statements can be analyzed in the framework of quantum field theory you’re saying here’s a proton it’s moving from left to right here’s a Zil bot spelled with an X it comes in it interacts with the proton it goes on its own way that is what you are proposing you might not be meaning to propose that but if you’re working with in quantum field theory this is what you mean you mean there is this Fineman diagram this new particle this new interaction and it is a rule of quantum field theory that I can take these diagrams and I can rotate them by 90 degrees and get another diagram that is real so I can rotate this I just take the bottom and move it to the left if this interaction exists then I can smashed protons together and create Zil BOTS if it’s a strong enough interaction that it would have any effect whatsoever on your brain we would have made it before in a particle accelerator and we have not so Zell BOTS could exist but they cannot both exist and interact with you strongly enough to be interesting if you’re a person other than a particle physicists so we’ve looked there could be plenty of new particles of nature but they must be either weakly interacting too heavy to create or too short live to detect and what that means is they can’t

possibly be very relevant to your everyday life they cannot affect your consciousness you cannot blame them for being in a bad mood you and everyone you know is made of the standard model of particle physics and nothing else likewise could there be new forces of nature and the answer is yes of course there could be new forces but again what is the range of the force what is the strength of interaction we have looked this is an actual photograph of an actual experiment looking for new forces of nature over distances of about that Bay and we know what they could interact with because we know that you’re made of protons neutrons and electrons so you just have to ask what forces are there that interact with protons neutrons and electrons and the answer is we haven’t found any so if there are any they better be either very very weak or very very short ranged like smaller than an atom and therefore they’re not going to be relevant to your everyday life you can’t blame your stomachache on the new forces of nature and so forth and again fearsomely quantitative results here is the actual experimental version of that cartoon I showed you of Wilson’s ideas before here’s a range of a force strength of an interaction we’ve ruled out every possible force that is both long-range and strong enough to notice if you go to the numbers here this is the the lengths and meters so this is about 1 meter about a centimeters down here and you look up here the strength relative to gravity the constraints are that any new force over that range has to be a hundred thousandth as strong as gravity or weaker gravity is really weak so any gravity’s up here is the green arrow right so if there’s some new force of nature that interacts over this kind of length scale it’s much much weaker than gravity is and the gravitational force between you and me is utterly utterly irrelevant therefore if there are any new forces of nature which there might very well be they don’t affect your everyday life just to convince you that gravity is weak I have a picture of people overcoming the force of gravity through a discipline called yogic flying where you sit on the mat and you concentrate really hard and you fly you levitate up into the air it helps if you like jump also but but you can overcome the force of gravity just through the electromagnetic interactions in your muscles you’re very small and the earth is very big the earth is exerting gravity on you and you are overcoming it with your neurochemical influences that makes your muscles twinge so any new forces must be weaker than gravity and gravity is nothing so any new forces of nature are not going to be relevant to your everyday life so that’s the conclusion the conclusion is is that as far as the immediate world of our experience is concerned as far as what you see and touch and taste and feel as you go through your everyday life we have the theory we are done we that does not mean we understand everything but the underlying laws that describe what baseball’s are made out of our tables or living beings we understand them it’s electrons and quarks with masses from the Higgs field interacting via those forces that’s the everyday world and now from experience I know that 2% of the people in this room we’re going to wildly misunderstand what I’m saying and think that I’m claiming that all physics is done even though I’ve already said three times I’m not saying all physics is done so for the fourth time all of physics is not done there’s plenty that we do not understand this is what I do for a living I think about the parts we don’t understand dark matter dark energy the origin of the universe quantum gravity unification of the forces and that’s just within high-energy physics there’s also the rest of the world once you know that the world is made out of electrons protons and neutrons you are not done in terms of understanding it what about chemistry what about biology what about sociology and psychology there’s an enormous amount of effort still to be done in understanding how the world works my point is we know what the ingredients are the analogy I sometimes use this is like chess you can learn how to play chess which means you know what the pieces do you know what the pawn is allowed to do and what the knight is allowed to do and so forth guess what that does not make you a good chess player there’s still a lot to learn after you’ve mastered what the pieces do so when it comes to for the everyday world we have figured out what the pieces are in what directions they can move in it does not make us good world players or chess players it does constrain the kind of games you can play someone has come up with a great new chess strategy that involves the rook moving diagonally you know that you can rule that out without listening to their elaborate presentation on it

likewise if someone has a great new theory of living their lives that involves homeopathy or astrology you can tune them out without listening to the details because just knowing the fact that the standard model of particle physics is the right theory of the matter that makes up the everyday world is immediately enough to rule out a whole host of possible phenomena anything you can’t do with electrons protons neutrons gravity and electromagnetism you can’t do in your basement at the LHC you can do it but here in this room you cannot you cannot bend spoons with your mind unless your mind tells your other arm to go out and bend the spoon but you can’t just do it with a new force that is emanating from your cortex because there are no such forces you could not predict the future you’ll see around corners the position of Saturn when you were born sadly irrelevant to the rest of your life blah blah blah and in fact we know that there is no life after death sometimes even atheists and skeptics like to be open minded about this because we haven’t done all the right double-blind experiments blah blah blah forget it if you believe in life after death tell me what particles contain the information that moves your soul from place to place is it electrons because those would be easy to notice because electrons are electrically charged and it’s actually quite a lot of charge is it atoms but the atoms don’t move very much when you die if you believe that there’s some way that you have an immortal soul that travels from place to place then you are not just saying we don’t know how it works you are saying that our current knowledge of the laws of physics is wrong which means you better give me a good reason to believe that our current knowledge of the laws of physics is wrong because it’s not and I’m gonna move on to do more interesting things so to bring it back to where we started I want to emphasize the world is a really big place this is a picture of from the Hubble Space Telescope so this is the Hubble ultra-deep field if you take a camera take your camera and you point at the sky at a blank empty region of the sky and you push the button you leave the shutter open for a long time if your camera is attached to the Hubble Space Telescope this is what it will see you will see that what you thought was a blank region of the sky is alive with these little blobs of light and every one of those blobs of light is a galaxy much like our own Milky Way galaxy so we live in a galaxy with a hundred billion stars every one of these little blobs even the tiny ones are galaxies with about a hundred billion stars and there are about a hundred billion galaxies in the observable universe there’s also the unobservable universe there’s also the things in the universe that we don’t observe like dark matter and dark energy we are very tiny and the universe is very big just to drive that home here’s us this is very bright in here so you can’t see it this is the pale blue dot image this is the photograph that was taken by the Voyager 1 spacecraft when it was 4 billion light years away from the earth and Carl Sagan coaxed NASA into turning it around taking a last picture of the earth it takes up a pixel or two in this image we are really really tiny and universe is very very big and there are many many things we don’t understand about it but almost 50 years ago people theoretical physicists sitting around trying to figure out how the world might work predicted that there was this thing called the Higgs boson knowing what we knew about nature as it already was we could figure out that the best possibility to make sense of the whole shebang was to invent a whole new kind of field that no one had ever seen before and make very explicit quantitative predictions about what it would be like 48 years later nine billion dollars 10,000 people working hard we found the thing we are very tiny we human beings here we’re very tiny compared to the universe’s a lot we don’t know but we are able to figure things out we were able to stretch our intellect over billions of light years in many many years figure out how the world works and it’s a lot of fun to keep going that’s the big deal thank you [Applause]