PSW 2384 The Doom of Space Time: Why It Must Dissolve Into More Fundamental Structures|Arkani-Hamed

I now call to order the Society's 2380 fourth meeting in the 146th years since its founding in 1871 good evening everyone my name is Larry Milstein I am the president of PSW the oldest scientific Society of Washington DC committed to providing a forum to further scientific understanding and inquiry welcome to our members and guests including those who may be tuning in to our live stream to tonight's lecture by NEMA our Connie Hamid in the John Wesley Powell auditorium of the cosmos Club in Washington DC we'll begin with a few announcements including the results of the annual election of officers this will be followed by a reading of the minutes of the 2380 third meeting we'll then turn to this evening's lecture followed by a question and answer period thereafter I will present a small thank you gift to our speaker make a few closing announcements and then adjourn the meeting to the social hour please join me in thanking the sponsors of the fall 2017 and the spring 2018 lecture series the policy studies organization in cooperation with the American public university and a generous sponsor who is asked to remain anonymous we have some luminaries of PSO with us tonight so if we would all please give Paul rich and Dan who Gutierrez a nice round of applause for their support and I think those of us who attended the Dupont summit also thanked PSO and the folks over there for affording free registration to PSW members to attend that all-day conference I am pleased to announce that tonight's speaker NEMA has been elected to membership in the society let's please welcome him to membership and to discover if in addition to NEMA any of our recently announced new members are here tonight and did not pick up their sign reprint of Volume one of the PSW book please see me after the lecture and I will be glad to give you the copy this year there were four offices up for election upon recommendation of the nominating committee the general committee proposed four candidates to fill the openings and ballots were sent out all dues paid and life members proposing the nominees for election by the membership and providing options to write in other candidates for all four offices voting closed yesterday and the results were paui all of the candidates were elected unanimously there was however one ballot voting only for the candidate for treasurer unaccountably and another ballot having instead of a vote for Ann McQueen as a member at large a write-in that was right in so otherwise the election of officers was by unanimous vote of the voting membership and please join me in welcoming Wow well not me but vice-president mark clapping who couldn't be here tonight treasurer Bret mag Aram and member at large and McQueen if they're here and they stand up please give them a round of applause and thank them [Applause] they're lawyers to work on behalf of PSW is really greatly appreciated as you can see we've already put Brett to work streaming and Ann to work doing the social media aspect of our streaming program and we now turn to tonight's lecture oh no we have to have the reading of the minutes sorry we will now have a reading of the minutes of the previous lecture by our recording secretary James healin and I did I did forget one thing it's really important I'd like to thank outgoing president by outgoing vice president Lloyd Mitchell and outgoing Treasurer John Ingersoll for their service to the society so please let's all James thanks Larry good evening everyone at the cosmos Club in Washington DC on November 17th 2017 president Larry Milstein called the 2380 third meeting of the Society to order at 8:06 p.m. president Milstein announced the order of business announced the evenings lecture would be live streamed on the internet and welcome new members the minutes of the previous meeting were read and approved president Milstein then introduced the speaker for the evening Gerald Joyce professor at the Salk Institute his lecture was titled life 2.0 synthetic self-replicating and evolvable systems looking at life here on earth dr. Joyce's research asks where did it come from how did it work and can we make another one in other words can we make a life to point out our planet developed 4.5 billion years ago through a process called orbital gardening and it was initially a violent uninhabitable place around 4.2 billion years ago a hydrosphere developed prebiotic chemistry then took place and many seen many scientists believe around 3.8 billion years ago the first life came into being Joyce said this life was based on RNA genetic material and this RNA life gave birth to the first DNA life around 200 million years later Joyce said we are the dust of the RNA world and we can see remnants of that world in our own biology to it our cell ribosomes our RNA machines they are RNA enzymes that catalyze their own replication remaking themselves many scientists believe that in RNA enzyme was the origin of RNA life on earth RNA molecules are strings of letters similar to DNA these strings are molecules that by virtue of the sequence of the letters fold into a shape some shapes are able to catalyze the self synthesis of the original RNA string to learn about how life began on our planet Joyce said we need to either dig one up of these original RNA enzymes find such an enzyme working in modern life or make one well RNA deteriorates quickly so finding an original replicator molecule on the ground is unlikely and no one has identified such a molecule in living biology so Joyce said he and his team have set out to create an RNA self replicator in the laboratory to create the replicator Joyce's team started with short RNA strings mutated them in a test tube and selected those that could recreate themselves carrying out a kind of Darwinian evolution in the test tube Joyce described the process in considerable detail showing numerous replicators that act by themselves and some that act in tandem with one another Joyce and his team have since spent almost 20 years evolving such molecules to create enzymes that can replicate at longer and longer strings of RNA they also discovered that some of their RNA enzymes can replicate other RNA enzymes even though they are limited in their self-replicating ability Joyce also described a variety of approaches to improving and expanding the replicative abilities of these enzymes he concluded by saying that he was looking forward to exploring how RNA could have led to DNA president Milstein then invited questions from the audience one member asked Joyce if he believes there was a double-stranded RNA intermediary on the way to DNA Joyce said it was possible but that it was also possible there was no intermediate there are examples of such evolution in known viruses although he acknowledged viruses are not perfect analogues because they require a host to replicate another member asked where the energy came from to drive the replication Joyce said the system was not equilibrium and is being fed by the individual building blocks of the RNA the chemical reaction of joining building blocks to one another is energetically favorable in the joining direction and actually releases energy about 10 kcal per mole per bond driving the reaction forward after the question and answer period President Milstein thanked the speaker made the usual housekeeping announcements and invited the guests to join the Society at 9:40 6 p.m. president Milstein adjourned the 2380 third meeting of society to the social hour temperature 6 C weather mostly clear attendance 109 respectfully submitted James Heelan recording secretary [Applause] thank you James are there any Corrections or comments on the minutes if there are none I will entertain a motion from the member to accept the minutes as read Thank You Robin do we have a second now Thank You al all those in favor of approving the minutes ahead please raise your hands or say aye all members opposed say nay the minutes are unanimously approved as read and will be posted to the website in due course may I recommend to you that if you are interested in the subject you really should watch the video for all of these structures that were presented and the more detailed explanation of how these molecules work and how they've been evolved in the test tube it's really quite an interesting subject and with that we'll turn to tonight's lecture and it's my pleasure to introduce tonight's speaker Nima Arkin II hamed Nima is professor at the Institute for Advanced Study in Princeton and concurrently is a D white professor at large at Cornell University Nima is one of the leading theoretical physicists working today his interests include high energy physics string theory cosmology and Collider physics he's made a number of fundamental contributions to modern theoretical physics among other notable contributions including his doctoral work on supersymmetry and flavor physics Nima worked out theories of fundamental physics involving extra large extra dimensions in collaboration with his friend and fellow physicist save us Demopolis develop fundamental physical theories involving emergent extra dimensions referred to as dimensional deconstruction and develop little Higgs Theory working with Howard Geor gie and Andrew Cohn before coming to the Institute for Advanced Study Nima was professor of physics at Harvard he was on the faculty at UC Berkeley before he went to Harvard and had been with SLAC National Accelerator Laboratory at Stanford University before joining the Berkeley faculty he is the recipient of numerous honors and awards not only for his work in theoretical physics but also for his teaching he received the five beta cap award for teaching excellence at Harvard the Sackler prize from Tel Aviv University the gribkov medal of the European Physical Society and the AIA and aft Pisa gam barrini prize in addition he is the inaugural awardee of the fundamental physics prize he is a fellow of the American Academy of Arts and Sciences he delivered the messenger lectures at Cornell University and is one of the physicists featured in the award-winning documentary film particle fever made by his friend and colleague David Kaplan who gave a talk here in this very room almost exactly what year ago NEMA earned a BS in mathematics and physics at the University of Toronto and a PhD in physics at UC Berkeley please hold questions for the question and answer period at the end of the lecture and join me in welcoming NEMA to the podium [Applause] all right well well is that too loud is that okay it's okay all right so it's absolutely wonderful to be here in this beautiful setting and we're going to be enjoying some light after-dinner entertainment with this subject of the doom of space and time let me just say a few things oh I shouldn't start yet is that okay yeah all right fine so let's do this now we're gonna get it hopelessly entangled now we're gonna see what's in my pocket actually I don't want to do that you know cat pictures there we go there we go okay ha that's why I get paid the big bucks all right is that better okay so first just a few words to put things in a little bit of context you know fundamental physics is the most is the oldest and most mature part of science depending on where you start counting our field is 2,000 years old or 400 years old really and it's more modern incarnation starting with Kepler and Galileo and Newton and we understand the way things work really well now okay our our understanding of the structure of the basic physical laws of nature especially after the revolutions of relativity and quantum mechanics in the early part of the 20th century is absolutely spectacular you know a hundred years ago it's amazing that human beings could walk around on the planet and not know the answer to questions like why is water wet and why is grass green okay we have answers to all such questions now really everything about the sort of basic structure of the world around us are beautifully understood and in this in the context of these two great prints bawls the two great revolutionary principles of 20th century physics quantum mechanics and relativity which really quantum mechanics and Einstein's picture of space and time now beyond that we do more esoteric things you know we want to test the way these these laws work we can make predictions for things like the magnetic properties of electrons where we can in some happy circumstances we can do throughout equal calculations to twelve decimal places and our experimental friends can make an experimental measurement to 12 decimal places and they agree to 12 decimal places okay so we have this absolutely spectacular of theoretical structure and understanding of the basic laws of nature and that's why most of the developments in in in most of science certainly but also even in this part of science should not have the character of pulling the rug out from under you okay because things work amazingly well right that's and that's why only every century or so on that kind of time scale do you run into a situation where you suspect something very big is wrong and indeed you do have to pull the rug out from under yourself and something that seemed like an absolutely completely obvious hardwired into the way we think about the universe thing has got to go and has to be replaced in some totally shocking way by more primitive more alien principles and ideas that's the kind of place we are in our field today okay and there's a there's a number of different problems that I could say this about and I'm focusing on this one that it has to do with the end of space-time there's one or two other problems of this of this rough character but but I'm gonna split so I'm gonna try to do something very dangerous in this talk whenever talking about a fundamental physics or theoretical physics to even a slightly general audience and this isn't a perfectly general audience of course I understand but even so there's always a temptation to lapse into metaphor and simile in order to explain concepts that can't real explain them that way they have to be ultimately understood in more precise mathematical terms and that's perfectly fine I've done it myself on more than one occasion I'm sort of sick of doing it though and what I'm gonna try to do in this talk is tell you the very dangerous things I'm going to try to tell you true things gangster everything I'm gonna tell you is going to be true and accurate some of them will be purely with words so you will have to think about them hard okay so not everything I'm going to say will be completely obvious but everything will be correct and if you don't understand everything in real time just remember the words and just know that they're true and so so and that's actually that'll be useful because as you think about it more you learn more you think more you talk to more people that knowing that that thing is true will actually be a helpful in your continuing understanding that so in the first part of the talk I want to explain why space time is doomed what what the arguments are that we have to get rid of this seemingly fundamental notion and then the in the next part of the talk I'm gonna talk about one particular strategy for going about attacking this problem there are many of them but the one particular strategy that my friends and I've been pursuing for the past decade or so and the first part is just you know I'm sort of reporting from the front of what my my friends and I in this subject of discovered over the last 30 or 40 years really not me I wasn't around forty five years ago but anyway the things that we've learned for that we've collectively learned that set the stage I like to describe where we've gotten to is the last four centuries have been like trekking through Nepal you know you land in Kathmandu you get some Sherpas you go there these complicated hills you do all these things that eventually finally you get the base camp at Mount Everest and there it is there's the there's the the summit it's sitting there and you have no choice but to start going up okay so so the first part of the talk is to get you to base camp okay just so you know what it is what the problem is why we have to do this crazy thing and in the second part I will tell you one particular one particular approach there as I said there are many others and but I present to do as an example a because it's what I'm actually thinking about so it'll be more personal and fun but also be as a an illustration of the way we go about trying to attack seemingly impossible to solve problems of the sort that I will explain to you in our business and what the what the sort of methodology is to try to take very huge scale problems and break them into little chunks that you can do something about when you wake up in the morning ok so so that's just summarizing what I said quickly we had two big revolutions in the first third of the 20th century in our understanding of physics there are the revolutions of Einstein's picture of combining space and time into space-time and in many ways much more revolutionary developments of quantum mechanics now these two pieces of physics are in principle and even as they were discovered are sort of separate intellectual frameworks you could imagine a world that was completely classical but which but which had a finite upper speed had a and so that world would be relativistic or he could imagine a quantum mechanical world that didn't know anything about relativity so there are sort of two different logical frameworks and so the second those were established of theoretical physicists try to figure out how do you talk about universes that are compatible with both of these principles at the same time that have quantum mechanics and relativity at the same time that turns out to be an incredibly difficult thing to do and very very constrained theoretical structure that's known as quantum field theory okay so now a particular quantum field theory this famous standard model of particle physics describes the particular elementary particles and interactions that we see in our universe but quantum field theory more broadly is a sort of the the general rubric in which we could imagine describing any candidate universe that's compatible with these two big big principles as I said it's incredibly incredibly constraining and incredibly successful so these 12 decimal places accurate predictions that we make are very subtle calculations that agree with very subtle experiments these are our principles our our the pillars of our understanding of quantum mechanics and space-time and that's what makes the storm clouds that we have now the early part of the 21st century so disturbing because they're not some little detailed thing here or there that we don't understand or some particular phenomenon that seems strange that we don't yet have an explanation for that's par for the course that's sort of normal science all the time there's something you're confused about otherwise we'd have nothing to do right but mostly the things you're conceived is about are explained within the basic framework that you have already you don't have to like you know turn everything upside down in order to deal with them that's not where we are today we can at least identify certain kinds of very simple thought experiments and I'll walk you through some of them that suggest something very big is wrong that goes to the very foundations of what makes things so spectacularly successful that's that's a paradox on the one hand those ideas of space-time in quantum mechanics underlie this you know are the pinnacle of the four centuries that we've gotten to and work spectacularly well on the other hand I'm just about to tell you they've gotta go okay and so the challenge is to figure out how can they go and why if they have to go where we faked into thinking they were there and that's that's what I'll talk about in the second part of the talk okay but what are the storm clouds first space-time is doomed that's the title of the lecture and that's because of the presence of both quantum mechanics and gravity so I'll explain why that's the case there's even I didn't put this in the title of the of the talk because it would have been a little more technical but some in some sense the second thing I'm saying is more radical that the first thing all of my friends would agree the second thing is the slightly more slightly more a controversial statement but I certainly believe it that that were eventually going to come to see even limitations of the ideas of quantum mechanics I'm not at all saying some crackpot thing like quantum mechanics is modified in some crazy way but that there are situations where quantum mechanics cries uncle we don't know how to apply the rules to things that where the quantum rules have to be applied to making predictions about entire universes all right so let me just say a few things about these two points first why a spacetime doomed all right so here's a very simple thought experiment by the way III take it many people who give these talks of fancy animation and things like that I'm a terrible artist and there's no animation okay so all my pictures are like this so if if this bothers you maybe we can stop and you can just leave right now you know cuz it's just gonna get worse okay so that that up there is a magnifying glass for example okay that is meant to be a magnifying glass anyway so but we're gonna do a little thought it what would I what I don't what I don't have in is there a is there a laser pointer up here oh okay fine yeah what I what I lack in artistic beauty hopefully we'll make up in intellectual content so so here's what we're going to do we're going to try to look at a region in space and time and just see what's going on there I want to measure what's going on in some in some piece of space and I want to see can I actually see what's going on at arbitrarily short distances okay now a basic fact about quantum mechanics that many many of you know is Heisenberg's uncertainty principle the uncertainty principle tells you that if you want the probe what's going on shorter and shorter distances and times you need higher and higher momenta or energies okay that's why the big irony of the LHC if the Large Hadron Collider is the machine that's probing the tiniest distances we've ever probed thank you sir thank you thank you is there a hugest machine we've ever built why is that it's because to go to really tiny distances we need really gigantic energies and so we got to build these humongous rings where things are accelerated around and so on all right fine so short distances means high energies very good now in principle there's no limitation to how short a distance you can you can resolve in that way by the way let me just in order to explain just just to explain that again you know if you're literally trying to look to see what's going on two very short distances you need light whose wavelength is it's sort of comparable to the size of the thing that you're looking at and then because of quantum mechanics you know that if you have light of a certain frequency it just has to have a minimum amount of energy it can't have a tinier energy than that has a minute amount of energy given by Planck's constant multiplied by the frequency of the light so that's why if you're trying to resolve what's going on in very short distances you just must have incredibly high energies fine in a world without gravity there's in principle no limit to the tiny nough sub the distance that you can probe in this way you can just keep keep going forever you just need higher and higher energies you need to beg larger and larger multinational governments for more and more money but but you in principle you can do it but because of gravity at some point something bad happens what do you think happens at some point you're putting so much energy into such a tiny region of space now you know roughly speaking equals MC squared so like having a lot of energy in some region is like having a lot of mass there now you know something bad happens when you put a lot of mass in a really tiny region of space what happens you eventually make a black hole okay and and there's so much mass there that even light can't escape from it okay so that means that your effort to see what's going on in here eventually makes a black hole that makes it impossible for you to see what's going on in there right now let's say after that happens you get frustrated and you build an even bigger accelerator even higher energies what happens make an even bigger black hole okay so this entire idea in fact the sort of basic reductionist paradigm that short that you go to high energies go to short distances eventually wrong and because of gravity there are some distance scale which it's simply impossible to probe what's going on at distances in times of that order now if you put the numbers in that's this famous clock length it's around 10 to the minus 33 centimeters okay it's a minuscule minuscule scale remember the the size of an atom is like ten to the minus eight centimeters okay the as of a nucleus proton or a neutron a set of minus 14 centimeters the distances that we're probing is the Large Hadron Collider a 10 to the minus 17 centimeters it's a 16 orders of magnitude away from that even okay by the way why is this this in so tiny that's a reflection of how weak gravity is compared to all the other forces ok gravity's ridiculously ridiculously weak but eventually if you put enough mass in there or enough energy it becomes strong and it does these terrible things so we can do this thought experiment that tells us it's simply impossible to give operational meaning to distances and times that are short compared to this famous scale 10 to the minus 33 centimetres 10 to the minus 43 seconds which is how long it takes light to traverse that distance and so on now every time this has happened to us in physics before that it's even it's not even in principle possible to give operational meaning to some concept it means that that concept doesn't really exist it's something approximate right this happened to us with quantum mechanics oh the constants of position and velocity of some particle that's something that we can talk about in everyday life we can easily talk about but we know that quantum mechanics forbids you from knowing precisely with the position and velocity of a particle is at the same time it's very important in physics to know and think about the things that you can observe in principle with perfect precision because those should be the objects that your physical theory is about and here we learn that space and time cannot be those objects because we cannot actually do any experiments to resolve distances and times with arbitrary precision all right now there's actually a more subtle aspect of this problem if it'll go over this part a little a little quickly although it's it's it's it's quite deep and important what I just told you might make you think of these difficulties are kind of localized to very short distances okay but in fact it's deeper than that that the the the difficulty the difficulty is is is apparent on all scales ok so here's another way of saying the problem which does not involve a very very high energies it involves experiments you and I could do in principle but very accurate ones okay and where again we run into in principle limitations on what what we can observe now this goes back to something having to do with quantum mechanics now a very important fact about quantum mechanics because the world is quantum mechanical it's not deterministic we can only predict probabilities these are famous facts about we can only observe probabilities a theory can only predict probabilities so what that means that if you want to get a precise answer in a quantum mechanical world you have to do some experiment infinitely often right you want you want to verify that the odds of flipping a coin are 50/50 you you have to you have to repeat the experiment over and over and over and over again and a principle to get a perfect answer you have to do it infinitely often that's one infinity you have to do the experiment infinitely often there's another infinity that we don't talk about as much in you know undergraduate courses and so on but it's also important quantum mechanics forces you to divide the world into the the finite system that you're looking at but the thing that's looking at it has to be an infinitely large apparatus as well okay and the reason is if it isn't then the apparatus itself has these sort of quantum jitters and jumps and so there's an irreducible amount of noise associated with the finite size of the system so of the apparatus oh let me just give you a concrete example I am roughly made out of 10 to the 30 things atoms very roughly okay so let's say I want to measure anything any quantity you want a name you know this famous magnetic moment of the electron that we've measured the 12 decimal places let's say I want to measure it to better than that I want to measure it to 10 to the 10 to the 30 decimal places so this is just pause how how ridiculous this is but I want to measure it so let's say 10 to the 10 to the 40 decimal places I could want to do that so here I don't I go I graduate students food ok I do the experiment everything's fine the 10 to the 10 to the 10th decimal places I'm flying everything's fine death no problem right no but at some point around the 10 to the 10 to the 30th decimal place something very bad happens because I as a finite thing could actually on that scale spontaneously fluctuate into a cloud of dust okay that would put a damper on up making a precise measurement figuring out with the tenth of the 10 to the 30th decimal places one of the less bad things could happen maybe my brain could just have a little random quantum mechanical glitch and even though I should have written down 7 in the 10 to the 10 to the 30th decimal place I wrote down two instead okay you see any finite system has an in-principle error associated because of quantum mechanics with any measurement it can make now that error is exponentially small and the number of things that you're made of that's why it's a practically no significance at all compared to the first thing that we talked about we have to do the experiment over and over and over again that's a much more significant source of an error but conceptually we need to do both things we have to do the experiment over and over again and we do with an infinitely large measuring apparatus and now we have a second problem having to do with gravity the fancy word associated with it is that there's no local observables but again let me give the the the quasi practical version of this let's say I'm trying to make any measurement of any quantity in this room okay and I'm trying to do it I want to get the answer arbitrarily accurate so I can't do it I'm 10 to the 10th of the 30 things so I'll make some other apparatus that other apparatus will get bigger and bigger and bigger okay I have to make it bigger and bigger and bigger but the experiment is happening in this room right so if I'm gonna fit all that stuff in this room that apparatus as I make it have more and more components bigger and bigger gets heavier and heavier and before I make it infinitely big what happens it collapses the whole room into a black hole it's not one of these teeny tiny black holes but now if you want to measure something with perfect precision even on humongous scales still there's a problem okay and by the way you turn into a black hole you have another problem that you can't do the experiment over and over again because you get sucked into the black hole singularity and die okay inevitably so that tells you that there is no measurements of any sort in the interior of a region of space and time that can belong as precise properties of the word those cannot be the things that laws of physics are about okay that's so that's already that's a very disturbing thing not only can't we do the sort of course measurement with the big accelerator that makes these black holes but there's kind of no sort of measurement I can make in the in some finite regions in space and time that can possibly have any perfect precision associated with them so these are the these are the deepest reasons we are convinced that space-time has got to be an approximate idea now what can we talk about there are a few things left that we can talk about and one of them is the following kind of experiment what you can do is we can't do the experiment of finite regions of space and time so we do experiments that start and end at infinity so what I can do is take you know I can take some apparatus make it bigger and bigger and bigger but moving further and further apart from other apparatus --is I can use them to shoot some particles in to the interior of the space and time where they bang into each other all sorts of stuff happens they come back out where they're measured in infinitely large apparatuses okay so that's a perfectly reasonable kind of experiment that I can do and where the results can be in principle perfectly accurate right so these kind of experiments are called scattering experiments for obvious reasons the observable that you talk about is the scattering amplitude the word amplitude there's because it's quantum mechanics something different happens every time when you when you collide two particles sometimes two things come out sometimes three things come out everything comes out with some probability the probability is the square of something called the probability amplitude so that's the thing that we should be talking about but the experiments don't happen in the interior of space-time they sort of they start an end in at at infinity now I've just given you very highfalutin reasons why these scattering amplitudes are interesting quantities but there's a very practical reason they're of importance to particle physics as those are the experiments we do okay are very close approximations of those experiments are what we actually do so you know when we collide particles at the Large Hadron Collider here's a picture of the ground outside Geneva Switzerland of course you don't see this oval on the ground but the hundred metres under that oval 27 kilometers around there's protons going around one-way protons going around the other way and they collide with each other now of course they're not literally coming in from infinity and going out to infinity but 27 kilometers is plenty big compared to 10 to the minus 14 centimeters which is the size of these little things so this is an extremely good approximation to to that kind of observable that we're talking about okay so you send some some things in you close your eyes some some things come back out of course in our minds eye we think what happened is well they went and first this hit that and then that happened and something else happened then some other stuff came out but what all you really know is what went in and what came out and those are the kinds of observables that we can talk about all right so that's the reason why space time is a doomed now and the only kind of observables that we can talk about the only kind of experiments that make sense are not in the interior space time but are somehow at infinity on on the walls very very far away now almost exactly twenty years ago in fact twenty years ago three days ago one of my colleagues at the Institute one maldacena sort of revolutionized the field by making a big discovery in string theory of a of a sort of a set of toy universes where you could see these ideas in in in action in a much more concrete setting okay now these are not our world but they're the closest you can come up with to a universe that's kind of like the inside of a box physicists love to put things in boxes okay if you're not a physicist you've suffered through our love of boxes in any physics course okay if you're a physicist you love our love of boxes and any physics course so physicists like to put things in boxes it's hard to put a whole universe in a box but but this kind of universe that one played with is is is an example so these are known as anti de sitter space is that not the word don't matter but masseur geometry looks like the inside of a tin can but it has the peculiar feature that the sort of the the the spatial geometry inside is warped and it's warped in the following peculiar way that even though it takes there's an infinite distance from any point on the inside to the walls of the box it takes light a finite amount of time if I shine a light here take the fine amount of time for it to bounce off the walls and come back okay so it's the closest we can come up to to the notion of a universe in in in a box now in this case if you apply the same logic you would say there are no observables on the inside of the box right there's so the only things that you can do is go to the walls of the box at infinite distance and maybe you can ping the edges of the box and waves would go in and they crash into each other though they'd come back out so you do measurements now on the walls of the tin can and those are the kind of observables that you should talk about so this this basic ideology would suggest that those are the kind of observables that that you should talk about but if that's the case you might wonder well if the experiment sort of starts and ends on the walls of the box what's the inside of the box good for right well one answer is well I can't figure out what happened unless I think there's a wave that went in and this hit that I believe this thing came out in other words the inside of the tin can as a way of making sense of the results of the experiment right but could it be there's another way of making sense of the results of the experiments where I never say that the inside exists at all I only talk about things out on the walls of the box that's the amazing discovery that was made almost exactly 20 years ago that in fact you can and remarkably you could completely forget about the inside of the box you could imagine that there's a theory that just lives on the walls of the box okay the amazing thing is this theory doesn't even contain gravity this is a theory that's very similar to the theory of the ordinary strong interactions in the real world of things that involve particles like quarks and gluons but when the interactions are so strong between them that you sort of lose individual track of what the particles are doing okay and so only Collective excitations of the whole medium is easy to keep track of in that limit where the interactions become incredibly strong what this theory just on the walls looks like all the results of every experiment that you do with such a theory are exactly as if there was an and inside exactly as if there was there was an extra space there that extra space had gravity in it you know even strings all the things that the people in theoretical physics were excited about or actually completely equivalent to a totally ordinary theory of particle physics albeit with very strong interactions on the walls of the box so this is amazing it's our first example you see I maybe I didn't stress it I should have said again if space-time doesn't make sense we know if space-time cannot be part of the fundamental description from the simple thought experiments I told you we have to get rid of it right we have to find some new set of equations some new set of ideas principles that don't have the word space-time in them but which somehow reproduce in some limit what we recognize as nonetheless recognized as a space-time so so the sort of buzzword is you have to come up with somehow space-time as an emergent thing out of ingredients that don't have it fundamentally and this correspondence is our first example it's a kind of baby example it's a gateway drug to the idea of emergent space-time it's a baby example because not everything emerges here you see very importantly time does not emerge there's a time that flows out on the walls of the box and there's the time in the interior at the same time so space is emerging space is emerging gravity is emerging pretty spectacular already but not time okay and so this is like a static infinite universe right it's not our universe we don't have this negative curvature and in fact our universe is expanding time is very important for our for our for our world but it's our first example of what this idea of emergence pace time can look like but if I go from our greatest success of the last 20 years to our greatest failure it's that our universe as I just said it doesn't look like the inside of a tin can in fact our universe is expanding if we run the picture back in time famously there's eventually even provably is Stephen Hawking and Roger Penrose taught us in the 1960s inevitably back there somewhere there's a singularity there's the place where the equations break down so that's what we colloquially call the Big Bang singularity right at the Big Bang you know there's nothing we don't know what came before the Big Bang because the notion of time is breaking down near the Big Bang okay so there is something we really don't understand what's going on at very early times time is the important notion here let's break now also at very late times our astronomer friends discovered in the late 1990s that the universe is accelerating not just expanding but the expansion rate a few billion years ago started accelerating again and that has a very startling consequence as well because that means that what we see now in the universe is what we're ever gonna see we're never going to see more than we see now there are regions there are things out there but they're but light from them will never make it to us because the universe is doubling in size at a uniform rate and every little bit of time that light you know travels to us there the universe doubles in size and it doesn't make it to us okay so what we see now is what we're ever going to see we're not gonna see anymore this is the best few tens of billion years in the history of the universe to do cosmology thanks and but conceptually this is a huge deal conceptually it means there's a fundamental finiteness that's thrust on us by by the fact that the universe is accelerating remember I told you that in order to talk about anything with perfect precision in quantum mechanics you have to have these infinitely big apparatuses with you well you just can't do it the accelerating universe means that you cannot divide the world up into a big infinite piece that does the looking a little piece that's being looked at okay so these are the hardest conceptual problems probably in fundamental physics today I think most of us in the field think these problems are a little too hard to do anything responsibly about right now I mean people mucked around with them for five or ten years they just seemed really really hard okay and why is it hard because we normally have to figure out time is clearly the Bugaboo here so we have to figure out not just emergence pace with emergent space-time and also this is the first situation where it's conceivable that we need to extend our picture of quantum mechanics and I say that because not because again just the stress of not saying quantum mechanics is wrong in any experiment that we might do in anyone's lab but because the necessary condition for quantum mechanics to make precise predictions namely infinite apparatus finite system simply cannot be realized quantum mechanics the rules cry uncle and we don't know what to replace them with so both space time and quantum mechanics both together are are in are in danger they're sort of are being threatened by this little observation that our astronomer friends made 20 years ago that the expansion rate instead of slowing down every 10 billion years is speeding up every 10 billion years or so all right now so that's the that's the first part of the talk I hope to have convinced you these are as you see these are very simple arguments ok they're a bit there may be a little subtle maybe some of them are a little unfamiliar but that's the nature we've learned over centuries the nature of really good questions and really good paradoxes and things that are worth spending a lifetime thinking about in this subject are simple you have to ask simple questions or not detailed complicated things about some funny phenomenon there are simple basic things that go to the heart of the laws as we understand them the questions are very simple to phrase and motivate as I hope I've done how to go about solving them is quite another matter ok so that's what we're going to now transition to but I think it's clear that what we what we what we're looking for some new principles and some new laws from which the usual the word unitary here means quantum mechanical from it's a usual picture of evolution in space and time have to somehow emerged together okay so that's the that's the more the more radical belief and certainly my own belief is that we're going to come to see not just that space-time is doomed is replaced by something else but that space-time and quantum mechanics are both things that have to emerge simultaneously from some more primitive sub sub stratum of ideas and that's the sort of thing that we should expect to be seeing all right so now so now now let's start talking about one angle into this problem and again I stress there are many many angles and if you got another one of my friends here that would give you a totally different talk from this point on but but this is this is a story that I want to tell you about so so how do you go about working on this kind of a problem again it's very good to know what the big questions are but you wake up in the morning you go to your office you sit on your desk and you and you can't just say today I will work on space-time is doomed okay and now what right what do you I have to actually do something right that even after tenure okay you actually have to actually have to do something death is a much bigger problem than absence of tenure okay so you don't want to waste that your a time on planet Earth so you want to do something so what are you gonna do um well I this is such a large-scale problem I think if we if and when we eventually figure it out I think it'll be an even bigger transition in our thinking than the one that that we experienced in going from classical physics to quantum mechanics okay after all physics has been changed a lot over the last 400 years but has always been about describing how things change in space as they move through time it's got to be a big deal to get rid of the notion of space-time so let me give a let me give a kind of a a parable so imagine that we are in the where previous to the transition from classical to a quantum imagine your classical physicist and I don't know the year 1840 and you're in bed and you are visited in the middle of the night by the ghost of theoretical physicist future okay and they say I have a message for you from the 1930s determinism is gone okay the world is not deterministic and they disappear into the night as ghosts of theoretical physicists future I want to do okay so what do you do with this information they've just told you that this thing that you thought was the bedrock of the Newtonian picture of the world that the things are deterministic that thing is wrong right you'd say how the hell can that possibly be right again we've been a kind of very similar situation where we're now right say how can it possibly be after all it works spectacularly clockwork universe all this amazing stuff how can it be that it's that it's wrong and if you want it to do something to try to guess what was happening it's clear you're not gonna guess it right you're not gonna in one shot go from F equals MA to the entire structure of quantum mechanics and Hilbert spaces and all the things that are there in quantum you're not gonna just do that in one shot you could try to do some idiot things like say oh I don't know maybe there's some random terms I can add to Newton's laws haha they're not deterministic anymore it's cheap and stupid and also not the correct answer okay so so what what what can you do well there's I think there's one thing that you can do and say look if that determinism thing is not really there then the determinism that I see in in my my laws right now it cannot be so as necessary as I think to describing to describing the physics after all the actual physics I have is compatible with this thing the ghosts told me about the turbine ISM isn't there in the real thing so there must be some way of talking about what I have right now under my feet in a way where the children ISM is not the star of the show okay and so in other words it motivates you to look around and say if you know that some concept is going to disappear in the next level up you should look and see whether there's some way of talking about what you have right now under your feet right now in a way that where that concept is not central yeah it may not be obvious that it's possible but if someone told you that it's going away you're motivated to look for some other way of talking about normal things that you have now where that concept isn't isn't central so let me skip ahead here so so indeed sometimes the most crucial clues are hiding in plain sight as funny features of the existing theoretical framework and I had a couple of examples will me jump to the one which is when I was just talking about Newton tells you that the way a particle goes from one place to another is completely deterministic you tell me what the position and velocity is now and I go to the next place by F equals MA okay but you can ask is there some way of talking about Newton's laws that were somehow determinism isn't hardwired in from the start there is and people in fact discovered it around this time in the late 1700s and and 1800's people like Euler and LaGrange and demo betwee and others and they're actually motivated by things that they had notice about how light moves so Fermat had noticed that light goes from A to B in a way that minimizes the time it takes to get there okay so that's why you know light light race and move in straight lines in an empty space from A to B but if you have if you have something where light moves more slowly in this medium than then that one then the reason it refracts is that it's choosing the way to make it from A to B using with Snell's law that allows you to get there as quickly as possible that's also why if you're on the beach and someone's drowning and you want to run and get there as quickly as possible the way to run is precisely to satisfy something like Snell's law here as well because you run more quickly on the sand then you can swim in the water okay so so so by that analogy people wondered whether there's some way of talking about how a particle moves from from A to B and they realized that there's a way of talking about Newtonian physics where you say there's a way a particle goes from A to B is it sniffs out all the possible ways that could go from A to B and it chooses the one for which the average value of the kinetic energy minus the potential energy is as small as possible so that quantity is called the action and so that's a totally different way of talking about classical physics you notice in that way of talking about you students when they first learn it when that way of talking about it it's kind of startling because it seems like it knows where it's where it's going right it doesn't look deterministic but it looks like you're sort of sampling every way you could go and then making a choice about one one one way to go to get there this in fact bothered the people who discovered it they wondered why there was this totally seemingly different philosophical way of talking about exactly the same equations in the end because when you figure out what those paths are you discover they satisfy Newton's laws so it's just the reformulation it's just a different way of talking about the same laws but somehow the laws of physics have this amazing feature at any moment of our understanding they can be formulated in seemingly philosophically radically different ways from radically different starting points even though the equations that end up being identical in the end and somehow it tends to be that one of them is the way they're discovered but another one is the one that's necessary to make the jump to the next level of description because it's the second way of talking about things where it determinism is kind of incidental it's the second way that generalizes the quantum mechanics you see not Newton's laws but it's a second way and in fact famously is richard fineman taught us all that happens in quantum mechanics is really in a precise sense you say the particle really does take all the paths from A to B and there's a separate amplitude for each one of those paths and you weight them in some way but and for big objects you get the sort of biggest contribution you get is from the classical path but the reason why so so first this is now changing the story and is going from classical to quantum but you see there was a clue to the coming quantum revolution in the structure of classical physics that's what's that's what's amazing that is the answer to the question how can it be that the that the rug is gonna be so pulled out from under you when everything works so well okay the reason that's possible is this some still miraculous feature of the laws of nature we don't understand why the laws of nature have this amazing feature but they do that exactly the same laws seem to be formulated from radically different from radically different starting points and that's why even though you think you've arrived at something at what's final and perfect from one angle if you rotate it and you think of it as arising from another angle you see ah from this point of view now can be deformed and to go up to another perfect thing okay all right so that was the that was the story with that was a way I just gave you a way that you could have imagined seeing or at least smelling the coming of the quantum revolution from the structure of classical physics and there were these clues sitting there on the structure of classical physics then that the ghosts of theorists future could have even motivated you to discover these things for all I know the ghost of theorists feature visited or Euler and LaGrange which is why they came up with this crazy way of thinking about things they just didn't cite the ghost of theorists future for they didn't give him credit all right so now it's all very philosophical and highfalutin for this part of the talk but now I want to tell you at least one place where many of us think there's an analogous set of hints in the structure of completely ordinary physics under our feet for the the looming disappearance of space-time and the emergence simultaneous emergence of space-time in quantum mechanics for more primitive principles okay and I'm gonna go back to the LHC now so we're gonna I hope you don't suffer too much whiplash we're gonna go from you know 30,000 feet down to very low to the ground even 100 meters underground you talk about very practical things at least practical to high-energy physicists okay so you know the LHC collides these protons and this is the sort of typical thing that happens the protons are made out of quarks they're held together by part it's called gluons so a proton is not an elementary particle by itself it's a big messy bag it's around 10 to the minus 14 centimeters big and when you slam two of them together most of the time they just smash apart we don't care about that and so much but what we really are interested in or when the you know point like constituents inside these quarks and the gluons they hit each other head-on some something new happens okay and just so you have an idea of the kind of rates here there are sort of a billion collisions every second at the LHC and the kind of rate at which you make particles that you care about some of these things you haven't heard of or maybe you have top quarks these are things that are exist experimentalists are still looking for things that are called super partners of ordinary particles if they're there if we're lucky and they're there we haven't seen them yet but if they're there maybe making one of them every minute even though there's billions of collisions a second okay so that gives you an idea that ordinary stuff from the ordinary quarks and gluons bang into each other is happening billions and billions and billions of times higher rate than the needle in the haystack that you're looking for okay so obviously in order to be able to extract useful information from the LHC you have to learn what the rate is for these torti totally ordinary processes okay so you can have two quarks hit each other and two quarks come out well they actually turn into Jets of strongly interacting particles it'll come out as quarks but anyway two things go in roughly two things go out or three things come out or four things go come out and you have to learn how to calculate those things reliably enough to be able to subtract them and look for something new okay and that's why National Labs and places like CERN higher theoretical physicists and do these difficult calculations okay in principle this is like an engineering problem quote-unquote okay we know the laws everything is fine someone just had to sit down and do these calculations so what do the calculations look like well Richard Feynman taught us how to do these calculations and many of you have probably seen these famous pictures that the way you figure out how particles bang into each others to draw fineman's diagrams these are legendary things fine fine even painted them on his van right now when you when you teach courses you tend to give problems where like to particles come in and to particles go out okay and okay you know half of your graduate students don't know how to do the kick you know they flunk that problem set so you don't you don't take them okay half of them can do it so there are candidates for maybe being your students right but that's not good enough for the LHC you need to be able to do calculus there were like two gluons come in these are the particles in the protons two gluons maybe three go out or four go out in fact you have to do up to like eight or nine go out even so what is it that actually happens you have to just draw these pictures okay I starts looking a little bit complicated this was the actual calculation looks like okay 100 pages of things that look like that 100 pretty dense pages right that's if you have like two particles in and four go out right okay fine nobody promise you not every question in physics has to have a simple answer in fact part of the chauvinism of this part of the subject is we declare is most interesting those questions that have simple answers and the ones that are complicated say well they're they're just complicated someone's got to do it the computer does it somebody does it okay that's not deep okay but these poor guys whether it's deep or not they actually have to do the calculation the experimentalist needed the answer sorry one way or another you got to do the calculation 100 pages are still too complicated physics is a wonderful way of rewarding morally good behavior okay and what these people almost thirty years ago actually the first example what I'm what I'm about to just tell you was done almost exactly 30 years ago they discovered that when you've finished they pull out every trick in the book and they already had a breakthrough paper or when they Gogh from a hundred pages to ten pages and everyone was super excited and then after a little bit more work they found that everything collapsed to a single term okay I'm not explaining what these little funny symbols mean but they're just they're they're are a measure of the energies of the particles involved okay so it's hundreds of pages involve massive amount of cancellations so the final answer is one term just that it's not amazing now this makes something clear and back then it was not universally appreciated you know and it makes it's okay that it wasn't universally appreciated it was not appreciated as a tip of a giant iceberg today we know it's a tip of a very giant iceberg but this already shows you that fineman's way of doing this physics it does something what it does better than any other way of doing the calculations is it makes the rules of quantum mechanics manifest and the rules of space-time manifest after all that those would both of things that we talked about you draw a picture in space and time okay and you have to add up every possible path that was taken in order to make it quantum mechanical you do those two things and that's what you get you get these pictures thousands of pictures hundreds of thousands of terms hundreds of pages of algebra if you want to make spacetime in quantum mechanics manifest that's you're led to believe that the answer is very complicated and yet the answer is shockingly simple okay so it's clear that making space-time and quantum mechanics manifest is hiding something else and we should therefore try to figure out what that something else is and we should try to figure out what the principles and laws and rules are that brings this simplicity to the fore and and and by doing that clearly that way of doing things will not have space time in quantum mechanics as the stars of the show it will have some other ideas as the stars of the show which we don't know what they are yet but we can start trying to discover what they are and hopefully if we understand them well enough we can then see how from the second starting point the description where it does have space-time in quantum mechanics comes out but you see now immediately there's something much more concrete that we can that we can get to work doing right first we can learn how to try to do these calculations you know this is they did this 30 years ago when you tried to do already the next most complicated case again it looked horrendously complicated ok so their methods were no good for the next most complicated case that was one reason people did not immediately see that there was something going on they just thought kind of an accident because they didn't see simplicity everywhere but the first thing you do is say well you dig little morons and see can you actually calculate these things see what the answer looks like this is to get data it's like theoretical data you want to see what the actual answer looks like and then next after you see the answer can you think of some structure that gives you the final answer from some different starting point okay so that's the sort of strategy that we can not pursue and in just my last few minutes I'm and I'm I'm just gonna really fly through some of the ideas just so you have an idea just even a rough sense of the kinds of new ideas and structures that show up because it gives you a sense you'll get a sense for on the one hand how how simple and basic they are on the other hand they're much more abstract and alien just to standard physical pictures then we are used to I'll skip over that so I can say that this subject has been developing really for around 30 years it's accelerated a lot over the last 10 years or so and one of the lovely things about it is that it combines a lot of ideas from different parts of theoretical physics a lot of input from string theory this world in a box picture Roger Penrose is darling from the 1960s that was the ugly duckling of theoretical physics for a long time twister theory it has a absolute role to play in this story there are things that people doing atomic physics and thinking about things like spin chains they've run into structures that are very relevant and very excitingly new structures in mathematics I think that even new to mathematicians or that they've been developing just over the past decade for completely independent reasons we've been finding that this physics the physics of trying to think about the particle scattering without space and time is intimately related to very new parts of mathematics in a way that is being really fruitful II explored by and mathematicians together now but all these things are converging on some new formulation of completely standard physics where space-time in quantum mechanics are not inputs but are but our outputs all right so let me give you just a flavor of the kinds of physical ideas that are involved in the kind of mathematical ideas that are involved in this emerging picture the because as we said on general grounds we should expect that there's some new physical ideas and that there are some new there have to be some new mathematical ideas associated with them as well so the physical idea begins with a very simple observation you don't need to know what any of these simple mean symbols mean precisely but that if you look at the very simplest possible interactions very simplest possible scattering processes where our three particles come together at a point in space and time the answer for those things are not complicated they're incredibly simple and they're furthermore when you understand things a little bit better you don't even actually actually calculate anything they're entirely determined by by basic symmetries of the problem okay so so there isn't even really a calculation to adieu here these are sort of totally nailed kind of god-given simple objects so those things are incredibly simple so why do we get these hundreds of pages the reason we get these hundreds of pages is because what Fineman tells us to do you see the particle that we're talking about there are real particles they move from the infinite pass to the infinite future they started some experimentalist detector they end in some experimentalists detector they're the real particles whereas in all these pictures of fineman's diagrams all these things on the inside there none of them are real particles in fact even in the lingo of the subject we use a word virtual particle to talk about them okay they're not actually real things nobody sees them they're all in our head as the story we're telling on the inside in order to explain the outcome of of the experiment and you can clearly technically trace all of the horrible complexity of the final answer to these virtual particles so the physical idea is to just never talk about virtual particles just eliminate virtual particles okay if you're gonna eliminate virtual particles what can you do all you can do is take those basic interactions where all the particles were real and you can glue them together in a way where still all the particles are always real so these are not fineman's diagrams they're very different kinds of diagrams I didn't explain why you had these black and white vertices but there there are two different the the particles we're talking about here are the quarks and the gluons and and they have a spin they can spend either in the direction of motion or opposite to the direction of motion that's these minus minus plus or that should have been plus plus minus so these are things that are spinning in their direction of motion that's something spinning opposite to its direction of motion so there are two different possible configurations you can have and that's what the black and white vertices are about so you can glue the black and white vertices together where everything inside is real everything is a real particle and so they can just ask what you get so this is these are not fineman's diagrams but they're the only thing you can do if if you refuse to say the word virtual particle and if you start playing this game just gluing these Tinkertoys together and seeing what kind of answers you get you discover something amazing for example you discover that if you glue sort of these things together to a for two particles in the three particles out that this single diagram is the result of the sum of 30 pages of algebra with Fineman diagrams okay so get rid of virtual particles immediate benefit right you actually directly write down just directly write down the answer is this absolutely directly physical process that's that's pretty cool now I go to the next most complicated case and you discover that this picture just gluing a little bit more on here and then you have to add two or more that look exactly like this just with these indices rotated around a little bit that those the sum of those three terms reproduce hundred pages of Fineman diagrams all right so this is good thinking about these physical only processes is good but there's a fascinating rub the rub is that while each one of these diagrams define are sort of designed to make it look like there's quantum mechanics in space-time there that's the point right things moving in space-time and splitting and so on you can show that starting with this example that one's a little special it's starting in this example each one of these pieces cannot be given an interpretation in terms of a process that takes place in space-time and that's compatible with quantum mechanics so and you'll learn more things you learned that there's actually a large number of wait you see there's one set of diagrams you draw here over and over again but for the same process you discover there's a huge number of different ways of expressing the answer when in this kind of language so and if you write down the expressions that they don't seem like will add up to the same thing but they're and then they're miraculous mathematical identities that are satisfied between them that guarantees that the final answer ends up being the same so it's clear that these physical only processes somehow on the one hand they're they give us the right answer on the other hand they're controlled by another world of ideas somehow they're coming from from somewhere else they don't care about space-time they don't care about quantum mechanics they care about something else and they're the origin of all the all the simplicity in the final structure that we see so all of these things started pointing to a picture that we should think of this final answer we should think about the amplitude roughly speaking as like as the volume of some region in some space if this was a fantasy around five or ten years ago that if I give you the energies and directions that all the particles are coming in with that information I build some shape in some auxiliary space and the volume of this shape would give me the answer what the volume would give me the amplitude for the process and if I actually wanted to calculate the volume I'd have to break it up into a bunch of little pieces in this way and each one of those individual ways of expressing the answer as I just showed you would correspond to one particular way of breaking it up into into a pieces so that was a kind of a picture for what was what was going on and in fact that's something that eventually uh at least in a in a theory that in leading order of approximation is literally exactly the same as the theory of the strong interactions in the real world but at the higher orders of approximation differs from it and is the more symmetric cousin of that theory that picture has indeed emerged in the in the last four years or so where if you give me the data of the energies of the momenta of all the particles you know the energy and the momentum is sort of four variables so each particle there's four variables associated with it so if there's you know ten particles you give me ten four dimensional vectors with that external data you build a shape in this auxiliary space and indeed the volume of this shape will literally calculates the amplitude so so that's the that's the that's the that's the end result that's a physical motivation was to get rid of virtual particles and we see that there's this very abstract underlying object that seems to calculate these amplitudes now let me just give you quickly a flavor of the mathematical ideas that went into building this object and we start from a very simple starting point if you imagine that you were telling a mathematician that you're scattering a bunch of particles they would say I don't know anything about physics so what what are the what what what matters for your particles you say are their energies of the momenta is I don't know what energy and momentum is their spin I don't know what those things are so what's left just their labels okay okay I can I can do something with labels okay so how do you scatter things if you only have labels you just permute them okay so that's it so this is this is the this is the most basic scattering we can imagine one two three four five just gets permeated to three five to one four all right now that just seems like an absolutely idiot thing okay but in fact up for around thirty years it's been known that this picture of a permutation is actually beautifully associated the picture of scattering as you'll see not not for things related to the real world we'll come to the real world in a second so this egg can make us start looking look like scattering just draw the permutation you see here's one two three four five and I draw them again up here but I just draw one goes to 4 3 goes to 1 2 goes to 3 and so on ok now all of a sudden this starts looking like a picture of particles moving and scattering with each other right if you think of that as time and this is space then it really looks like gosh one is moving 2 is moving three hits 2 you know they all hit and and and scatter against each other ok and in fact there is an there's an old story really goes back even more than 30 years that really precisely relates permutations to very special systems in one dimension of space with particles moving and scattering against each other ok all right now people have been impressed with this a very beautiful picture people have been impressed with it but it will always seem like is a very special thing to only having one dimension of space ok and in particularly can't apply to the real world there's no creation and destruction of particles all that happens here the fundamental interaction is just two things in coming in and two things going out not the ability for one thing to decay into two things or two things to create one which is what we have in the real world however in the last decade or so a little bit more people have learned how to associate people have learned a new way of representing permutations in a graphical way and it goes like this so let's say I want to represent the permutation 1 goes to 3 2 goes to 1 3 goes to 2 what I do is I don't put 1 2 3 at the bottom and 1 point 2 1 2 3 at the top I just put 1 2 & 3 on the on the outside of a circle and I draw a little black vertex on the inside and the rule is that in order to see where it is like where does 3 go I walk into the graph and if they hit a black for a text I make a right turn okay now with the white vertex when I hit it make a left turn that's it now glue them together any which way you like the claim is that every permutation can actually be realized by some way of gluing black and white vertices like this together okay so that gives you this funny permutation one goes to three you go in you go you turned right left right okay so just these dumb pictures with black and white vertices are now ways of representing permutations now of course we've just seen moments before in physics these pictures with black and white vertices and believe it or not these are identical pictures okay so every permutation can be represented like this and then and this this begins to become more technical but we start with an object which is fundamentally determined by this idea of representing permutations graphically but then associated with if canonically are in a very very simple way are some geometric notions the geometric notions in turn are generalizing very simple things like the notion of the inside of a triangle or the inside of a tetrahedron we can have simple notions like this that are that are that are slightly generalized into into larger mathematical spaces and and so every one of these pictures first starts off life as something that represents a permutation but but quickly becomes associated also with with an interesting set of mathematical objects matrices for example that have the funny property that all the determinants all the 2 by 2 determinants in these matrices are positive or I can get a general matrix general matrix with some number of rows and some number of columns the only game that you want to play is that all the determinants of these matrices are positive that game turns out to be completely related to these pictures with black and white vertices completely related to this way of realizing permutations and completely related to the physics in the end ok so there's just one basic object this interesting way of representing a permutation that gets lifted through a variety of structures until it ends with a scattering amplitude at the top ok so again that you're not meant to understand any of that but just so you got the flavor I just wanted you get to get you a flavor of what what are the ideas that are involved here if we're gonna replace space and time with something else we can't have space and time so what could we have we have to have much more primitive things around we have to start with we have to start with much more primitive and basic mathematical ideas and that's indeed the kind of thing that we have been that's indeed the kind of thing that we've been seeing just to give you just to give you a concrete example I told you that there are some there's something there's this concrete geometric objects things we called the Apple to hydron that and that the the the volume of that space calculates calculates scattering amplitudes well let me give you an example so if you want to calculate just two particles in two particles out but what in fineman's language would involve more and more complicated pictures on the inside with more and more internal loops of particles these are the calculations you know at the LHC we need to do them at one loop and maybe two loops but they get a really incredibly incredibly complicated you would never even you would never dream of forcing a graduate student even do a one loop calculation okay but so these are quickly the number of Fineman diagrams is larger the number of atoms in the universe okay those calculations are replaced by a geometry problem of the following variety just just so you see it's a problem I can describe to a kid in grade 8 you have a two-dimensional plane you imagine you have some red vectors and some green vectors and they're all in the upper quadrant so that's the first requirement they're all in the upper quadrant and they just need to have the following property that if you take the the the vector from any pair of A's like a1 to a3 it should always point in the opposite direction as the vector between a pair of the B's the same pair of the B's that's it so just solve that geometry problem all the possible configurations of red and green vectors in this upper quadrant that satisfied this property if you solve that problem there's a dictionary that converts a solution to that problem to the answer to this calculation with space-time in quantum mechanics in it okay alright so in this example we begin to see the kinds of ideas that could show up indeed the final answer is the the volume of some region you can break up the region into lots of little elementary pieces each one of the pieces are one of these simple pictures there are many different ways of doing it but the final answer is always the same crucially the pieces don't have a space time or a quantum mechanical interpretation but the full volume does and in a very precise way the rules of quantum mechanics and space-time emerge a sort of derivative notions from this underlying geometry and I'll just end with this with this picture so this is a process that you could care about it the Large Hadron Collider you might imagine two gluons coming in and six gluons going out that's something that actually matters and so if you wanted to calculate again I'd not hundreds thousands I don't even know how to count how many pages of Fineman diagrams it would be but if you want the leading the the the leading contribution to the rate for this process in this picture you would literally draw a shape like that okay so you would take the energies and the momentum of the particle the energies immense of the particle would tell you to draw not in space-time in some funny abstract space and this funny abstract space we draw a picture and then you just compute the volume of that thing and you're done okay so there's a long way to go to to make these things fully realistic but where we're at a starting point we're in leading approximation these ideas that we're talking about actually describe the real world and they also show us in a very concrete way how it might be that the rules of space-time and quantum mechanics emerge together sort of hand-in-hand from more primitive building blocks all right so so I hope that at least from the first part of the talk you got an understanding for why where it has sort of dramatic moment and we're we need big new ideas it's not clear yet exactly the shape the big new ideas will take there's lots of different kinds of work going on in many different directions in the field they give you a snapshot of one of them in the second part of the talk but I hope from that part you've got at least a sense for how we go about attacking these problems you you can't you can't attack them in a completely direct frontal way often you have to go a little bit sideways find some slight cousin some some some some question that has some some of the flavor of the big questions that you're trying you're trying to solve but which has enough chinks in its armor that you can start making making progress on it and so what's what's nice about the particular subject I told you about a problem of fact that it's actually directly relevant for experiments or related to things that are directly relative relevant for experiments is that there's a there's a notion of right and wrong you know we can we can decide if we've managed to compute something that we couldn't compute before we can check whether it's right or wrong we can check since we're not putting in the rules of relativity and quantum mechanics space-time in quantum mechanics we can check if they nonetheless agree with them when they when when when we're done all right I think this has been even this little part of it has been an exhilarating adventure so far one of the things that I find very interesting is it's that fizzes and mathematicians have been working together in this subject a lot of developments relating physics and math of us have a storied history going back centuries but normally one subject or another is ahead knows more about what's going on and then tells the other one what to do and this is a little bit unusually of course is also very recent so we'll see how it develops one where we're both seeing exactly the same kind of ideas from radically different starting points that roughly exactly the same time and so it's in a fruitful and meaningful way we're actually talking to each other but it's also clear that we don't have a grand synthesis if we had one I could give you a normal length talk about it so the grants if this is yet to come so hopefully someone will find it in 10 or 20 or 50 or 100 years and and I trust the cosmos Club will still be around on that time scale so someone will come tell you about it thanks a lot [Applause] so we have time for a few questions there is a procedure for the questions we have three people with microphones who will be running around the room to bring the microphone to you we have a new a new colorful addition to our microphone procedure we have a bright red microphone and a bright green microphone and a bright blue microphone and so I will be able to identify you and when you get the microphone and your identified as blue green of red please stand up please tell us your name please tell us if you're a member there's no penalty for not being a member and then ask a question so we'll start with Joel with the green microphone oh thanks dr. Deema thanks for your president you have to hold the microphone very close to your mouth okay thank you for your presentation sir Joe Wilson member two questions with the amplitude hadrian I guess I kind of cheat a little but I tried to read some of your papers on it you just talk something about a positive geometry and which its embedded right is is is that is your sense that that's kind of and this might not be a good question the real thing at which which it's the primitive the geometry is the primitive well I think I think it's it's fair to say it's such such early days in this story it's a very bad idea to take the latest thing that you understand and and and think that's that's the real thing but I think what we can with confidence say is what's not the real thing okay and so that's a kind of the the whole point here is to to sever as much as possible to eviscerate as much as possible all of the usual language and comfort and luxuries of having a picture of a space time and having you know if you're doing quantum mechanics if you're a physicist you know you have a hilbert space you have all these spaces that you're used to and if you see any of them around what you're doing from this point to you were doing it wrong right we have to get really uncomfortable all right we have to go somewhere we just have to cut the cord we have to we have to be in territory that just does not feel like that we're clearly in territory like that okay so now at every point we have a provisional understanding for what we think the most important thing is and it changes every two or three years because it's it's still developing so right now yes it seems like certainly in this in the kind of stories that I'm telling you what replaces the rules of space-time in quantum mechanics are things that that loosely are just the existence of some geometric shapes and it's what the so the just just to give a just to get a slightly concrete idea of what it is you check like if I hand you some answer if I hand you the actual the the rate to see what happens when two things go on and two things go out how would you check that the answer is compatible the principles of space-time and quantum mechanics well one thing that you know is that it when do when do any kind of amplitudes in physics become large it's when you have some kind of resonance right so if you're sitting on a swing you sit on resonance the amplitude becomes larger and larger and larger so if so that means in this context if some particles come in and they have the ability to make a real particle that then travels a long distance and then spits back out to a bunch of other ones then you'll have a big amplitude for that just like the resonance on the swing so that's one way of checking if someone hands you a formula that says and claims this is the amplitude you have to see well where does it blow up is there any place where it blows up and it can only blow up in that kind of configuration where a bunch of the particles have the ability to make something that then goes out and decays and then it has to blow up in a very specific way to be able to interpret it that way so those are the things that fineman's diagrams come make blindingly obvious so now you can ask if you don't have the picture of space-time if you don't have the picture of quantum mechanics where is that going to come from and the answer is that that comes from the geometry so there there's a there is a dictionary the the dictionary says that where the amplitudes blow up corresponds to moving to the faces of this geometry and then the fact that the way it blows up isn't splitting in two is reflected in the fact that when you go to the face you actually see on the face the geometry sort of splits into two or pictures of the geometry but all those things are not being put in by the existence of an underlying space-time picture but they have their own purpose in life that comes from these these geometric starting points so but so if I stop there indeed the positive geometry as we say it would be the star of the show but but we're so far from being done that that I imagine that's gonna go through many iterations before we figure out what the actual principles are thank you sir we have the red microphone back there somewhere hi Tom Hartman I forgot to sign up for membership the last time I open I when I went home the last times I would make sure to do it this time because I do enjoy these lectures have been here a few times one thing if I'm understanding the problem correctly it's what you're basically saying is you don't have you're looking for the first principles that emerge into what we have been calling space-time and quantum mechanical theory and that's what we don't have so how did you draw the diagrams if you don't have the underlying if you don't have those principles we don't see like like where do the rules come from for join those diagrams that's you know like yeah that's that's why it's it's an it's an it's an adventurous subject so we don't have the rules we have to come up with the rules so it's not but it's not quite as bad as it seems because because we know something about the final answer so that's that's that's a big key thing right we have a lot of data theoretical data we have data with the what's the final answer because remember we're not changing anything here this is really the analog of looking for the principle of least action we're not removing space-time and quantum mechanics we're just trying to find a way of talking about them talking about this ordinary physics where it's not there with the hope of finding the right grammar and the right words of the right language that will get us in the right mental space to be able to make the bigger transition where we actually remove it that's what's ultimately needed but but because of that we have a great luxury that we know the right answer in many cases we have a lot of data and so that's a big guide to what you should do and in particular when I withdrew those pictures with black-and-white diagrams the reason it was completely nailed what kind of picture I could draw is that the simplest case where just three things come together in that case quite beautifully you didn't need Fineman to tell you what the answer was for that most primitive simple case because the answer could only be one thing just dictated by very simple essentially just symmetries of the via problem so so there are some things that are just locks you don't need any rules they're just sort of essentially dictated by by the by the by the symmetries of our relativity and then but now you can ask what what you do with them and now you have to decide to play a game what happens if I glue them together right I ignore the fact that doesn't look like Fineman diagrams I mean people didn't they could have done it at any point in the last sixty years played that game but but but when you but when you're motivated to do it like this and relax for a little while and just see what happens then you start making these interesting observations my goodness if I put them together in this way just this one picture gives me the whole answer and then and and then it starts developing from there Green microphone back there and if anybody has a question please keep your hand up long enough for the microphone runners to see you so we have one on the way back there but the green microphone yeah yes yes yes you like oh wonderful how could you hear me yes okay wonderful thank you I am Elena Keith with your Citizen project and I'm a guest of vice president of the club and happy to be here and nima thank you so much for this this is terrific and you I definitely definitely would like to acknowledge you you step outside what's comfortable so you are in definitely uncomfortable space and that's the space where older see we create and we find new things so they discover in the space of discovery so this is terrific and the question that I have did you get to see parallel so to say correlation with what we call one point six golden mean it looks like positive geometry what we call positive geometries based on the number consistently whenever the matter wants to be organized and then when we go into disorganized space cows or whatever's negative geometries it's all man you mean like hyperbolic versus positive yeah it's um there's no direct relationship there's no direct relationship yet I should say that that the that there is some important that it is it is interesting that that that this inside of the tin can universe that so much progress has been made wealth is negatively curved but there is a sense in which these shapes are convex so they are they are positively curved so there there is a there's a difference but they're in totally different spaces so I don't see any direct relationship unfortunately yet we have a red microphone question oh and yes Rudy Qatar and I am one once in future member of the club I decide a fundamental question that your notion may answer is the Planck length the Planck length diminish with the Lorenz Fitzgerald contraction ah no it does not no it's not I mean it's not a well yeah a no in no meaningful sense does it does it it's not there isn't like a little rod sitting there in fact that this is this is a very important point so we're we're being a little loose when we talk about the Planck energy right because of course and an actual energy would depend on the observer and so on and so forth what we're really but something which but there is something which is observer-independent which is not just the energy of one particle but if you have one particle here another particle there right then the kind of the the the what that the violence of that collision is something that all observers agree off okay so while for example we say that at the Large Hadron Collider were colliding protons that you know roughly an energy ten thousand times bigger than the MC squared of the protons but that really what that means if I go to a frame of reference is moving incredibly quickly in in in one direction then I could make the energy of one of the beams vastly bigger okay but then the energy of the other beam would be vastly smaller and there's something that everyone would agree on is that the LHC produced a Higgs particle okay it had enough energy to produce the Higgs particle there's something completely invariant which is there not for the energy of one particle but something involving two of them colliding so when we talk about the Planck energy we're talking about those kind of physical experiments when I'm trying to probe very short distances that's what I'm doing I'm sort of colliding particles at higher and higher energies and that's what will eventually produce a black hole and cause all those problems and that will happen in with the same value of that energy and the same value of that inferred length scale for all all observers okay so it's uh however what what what you say raises it is the answer to a very very important point you see you might have thought that all this business about space-time breaking down just is pretty boring after all the notion smooth surface of table breaks down looks like a smooth surface but I know when I go to very small scale just made out of atoms and molecules and stuff like that right so why isn't it just atoms of space-time oh no big deal like where why are you making such a big fuss right we've seen all the time things that look smooth turn into things that look choppy when we see they're made out of microscopic constituents so why isn't it just that it's just atoms of space-time it can't be that and it can't be that because of your point because for it to be atoms of space diamonds are very important that those atoms are small but small and whose frame there is no universal notion of small and whose friend you see and another way of saying it is that is that we can say that the table is made out of stuff because the table chooses a frame okay but we can't say it about the vacuum without breaking Einstein symmetries so that's why you can't just have atoms of space-time the notion of atoms space-time is in radical conflict with Einstein's relativity if it wasn't this is another aspect of the problem a guy kept mentioning that relativity and quantum mechanics space-time and quantum mechanics these two things that put such a ridiculously tight straitjacket on our imagination if we just had one or the other life would be much easier much less constrained and many fewer people would be working on it cuz it'd be no point okay after all you could have made it justifiable completely you can make a justifiable complaint all this stuff at the Planck length is happening at energies sixteen orders of magnitude bigger than anything you can do with your with your accelerators so aren't you just making crap up right now it's a great great work if you can get it I guess right you know just sit there you know I think this is going on no I think that's going on I think this is pretty I think that's lights I like strings violins cellos Nova specials right if that's what was going on that would be a complete this intellectual disaster right and the field would be just that's not what's going on and it's not what's going on precisely because it's almost impossible to monkey with the rules without breaking something and so despite the fact that we can't actually do experiments at the Planck length or a plunk energies even if we imagine trying to write down something which grapples with these problems which is not automatically dead not by new experiments up there but by all the old experiments that told us that relativity and quantum mechanics are right that is such an incredibly high bar to pass that that that well essentially only one theory has even come close to passing over the last 50 years in that string theory that's why people work on string theory it's not there's clubs and cliques and these people like it they think this is pretty that's pretty there's an actual beefy accomplishment to write down some concrete formulas that don't violate relativity and quantum mechanics and fix something up at very high energies involving gravity right no one else has done that it doesn't mean that it's right but that's why we have because there might be if we work another 50 or something we'll find a second way this radically different than that one then will be then will be an interesting situation you don't we'll have to we'll need an experiment up there to tell us which which one of them is right but that's why the maturity of the subject matters because you don't need new experiments to rule out ideas 99.999% of you ideas are wrong already out of the box because they violate all the old experiments that gave us these big principles to a begin with so but anyway your question about the Lorentz contraction Planck length is one of them because that's a word level idea oh just make some crystal atoms of space-time that's just dead out of the box okay so you have to do something more subtle and all the things I'm talking about are much more subtle than that you know this world in a tin can picture of this holographic picture that's way more interesting right it's not like you just put the inside on some kind of crystal or lattice no it's this other theory that lives on the walls of the box and all this fancy stuff what I was just telling you about in the last part of the talk again even more alien more abstract all in an attempt to a grapple with this question of our space-time comes from precisely because we can't mess with relativity three more questions it's going to be green and then it's going to be blue and then it's going to be red oh you could we'd have bloody makhachev I'm not a member and then what we'll take one from our lives first of all thank you very much for the talk oh there you are beautiful American ideas in there i named vladimir Tkachev I am NOT a member okay so thank you for the talk as a beautiful mathematical ideas and I have a question you mentioned at the very end that this volume picture responds to the leading term in the expansion and could you comment on how much of the beauty and the symmetry of the answer comes from the fact that is the leading term and if you want to consider chance afterwards that would be extra complexity coming in oh so so two things first the the symmetry is actually there separately for each term in the expansion okay so there is there's a well-defined symmetry it's it's there and leading the sub leading is there in all of them that literally the picture of literally that volume literally that shape is true literally for a cousin of the theory of gluons that has maximal supersymmetry okay so it is not the real world but it is the real world - the leading order of aprox so what that means is that the real world - leading order of approximation has the magical symmetry that that that it has some magical properties it literally it has some I didn't have a chance to describe it it has some it has an infinite amount of symmetry that could have been spotted by people 60 years ago it just wasn't it wasn't smart until eight years ago okay but it really has sort of some some magical features that that again they're all these clues lying there under our noses that there's something going on and in the real world that thing is probably that symmetries in the way we understand it is is is definitely messed up by the sub sub sub leading corrections but but but that's not necessarily that's that's that's not necessarily good or bad for this for this picture what we don't know yet know is is what if there is one and if there is what it is analogous kind of geometric understanding for not just the leading piece in the real world but the sub leading for but all the pieces and in fact some you know even better understand me the whole answer that doesn't force us to divide it up into these little pieces that that that we add up before before we get to the blue we're gonna do a couple from the web from our livestream audience so an so we have two questions from YouTube the first one is what do you think of James Gates is supersymmetry research suggesting error correcting codes are embedded in the fabric of the universe oh yeah I know Jimmy it's very well it's very very interesting work yeah I mean I don't know I'm not an expert in the subject you know yeah who is it from fabric fabric of the universe is pretty heavy stuff so but what what Watterson did not give their name is Journal from Maryland that's okay the next question but it is fascinating stuff is does the polyhedron have to conform to certain relevant or familiar symmetry group properties um no no I mean it in other words at least so far on this picture it doesn't matter if the shape it doesn't matter if it's like a dodecahedron shaped or something like that it doesn't matter if you give a particularly special looking version of these shapes what matters more is the sort of network of relationships between the vertices and the edges and the faces and how they're all sort of tied together that's much much more important so go to our blue i'm joseph powers and i'm not a member and while i appreciate the color charge theme of the microphones tonight i wondered sort of at the end of your talk when you're when you're talking about these pictures that are much simpler than than the Fineman diagram in my mind I'm imagining testing that these theories to find out what is the truth and I'm one and it seems to me that while the the strong force is what you measure at the Large Hadron Collider it should be more fruitful to look at places where you know the standard model isn't working like flavor oscillation and then the neutrino mass and so I'm wondering what's sort of how would you draw a diagram for various predictions for that sort of thing yeah well so first first let me make just a few comments about that first the the whole nature I tried to emphasize but I'll say it again the whole nature of what we're trying to do is not to change anything we don't want to change anything now I mean right and now we're now we have a pretty modest goal which might still take the rest of our lives but it's still a fairly modest goal to try to reformulate standard physics in a different language where we don't rely on this notion of space-time and quantum mechanics we're not trying to change it we're just trying to find a different starting point that will give us identical results and in fact the the the the very modesty is what's giving us as was giving us a way of knowing that we're not screwing up you know we can't we're not just speculating and and and and and you know wondering whatever we do we have a way of checking whether it's right by either matching it to standard ways of doing the calculation or often that's not available but you can still check whether the results conform to space-time in quantum mechanics ok you can check whether they conform to the rules so we're not trying to change anything and is not a quit so it's not a question of whether is it's Fineman diagrams more correct or this is correct by design they should give us the exactly the same answer as as 5min diagrams now you could say why the hell are we doing it well a there's the practical thing that if i'm diagram is very hard to calculate but b is for all the philosophical reasons i said in the first part of the talk that this is a safe way or a beginning way to dislodge our addiction to these concepts that we suspect we have to get rid of eventually but your question about neutrino oscillations and other things like that first yes it's true neutrino oscillations go beyond the standard model they go beyond the standard model in a very very mild way okay so so a you know a competent second month graduate student in this field will know how to change the standard model in a very small way in order to accommodate neutrino masses so it's not some big it's not it's very very easy to easy to do if you ask that so it's not it's true it's officially beyond the standard model but only in some in in a rather minor way it's it's a it's a very interesting phenomenon we should measure them and learn everything we can about them it's part of nature but it's not like it's not some dramatic extension of the standard model in any way now you could ask how do we see any of those things from this other kind of point of view that's that's a that's a very interesting question there's a lot of both you know theoretical technology that needs to develop in order to figure out how to apply all these ideas to the case everything I talked about is some idealistic the particles don't have a mass there you know they're there there are the strong interactions but they're not they don't have all the complexities that we'd have if you dealt with top quarks or even electrons interacting with photons is actually a slightly harder problem than the one that we're than the one that we're talking about so there's a lot that needs to needs to be developed but there is a you could imagine as a goal to try to figure out some underlying principles Oh be it geometric be it you know as time goes on we see that it's not even geometry so much is something really fundamentally combinatorial which is sit systems everything but be a geometric or combinatorial or whatever it is is there something that actually works to describe everything in what we see in the real world around us that's that's a very concrete goal we're very far from that we're very very far from that but we're we're taking four steps towards last question red microphone hi there yes Brad cook and I'm not a member and I'd like to thank you again for terrific talk and I'm afraid what I have to say though it may seem something like a complaint because you did a really good job did a really good job in in conveying to me at least the relationship of the amply - he drawn to particle physics but I didn't get from the talk though was how it relates to gravity ah well if there's a good reason you didn't get it from the talker as we don't know yeah I I wasn't trying to hide that fact yeah it's a well I mean that's a little glib it's a little glib but that that's basically true yeah I could I could I can make sure it is well so let me let me let me not let me be slightly less less clip okay so so so so just for some observational facts about the the data again just the theoretical data so if you're a student learning how to do these calculations you love the answers you get from very simple toy theories at the beginning of all the text books where the particles don't have any spin okay they're called scalar theories but never mind those are things that you can do even with four or five or six points no prob you can impress your professor but they're not impressed anyway okay then the next most complicated ones is one of the particles of spin one they're like gluons right and that's the one where you know two to two you can do in a problem set two to three is fifty pages very hard then the next most cop then after that is gravity which is spin two and then even just two to two for gravity is like a thousand terms complete nightmare okay just you think totally insane so usual point of view textbook picture Fineman diagrams you order complexity low spin simplest gluons in the middle are pretty complicated gravity ridiculous okay now now at this moment in time what we know about the actual final answer how do you think the simplicity is organized it's exactly backwards okay gravity has the simplest possible final answer gluons have intermediate and the worst and most complicated horrible ones are the ones that involve the ax scalar so there's lots of evidence that the answer in gravity is somehow has the most remarkable structure in it furthermore the answer in gravity is a thing that's naturally lifted into into the sort of first avatar of string theory that people were excited about in the in the 1980s and even well they're still excited about today but where it was born and they're there's lots of mysteries left over that we still don't understand there's clearly an ocean of structure associated of magical theoretical structures associated with gravity much of what is is still hidden so why do we care so much about gluons in the middle right this that's what I just told you it seems to be some intermediate objects well two reasons one is the sort of practical one that experimentalist care about them but the other one is a little more interesting is that something that the strength there is really discovered is that to begin with but which has been seen in a way that's that that kind of removes it's stringy origin and you can see it more directly kind of as an intrinsic statement is that in a in a in a very concrete sense if you know the answer for gluons you can kind of square it and get the answer for gravitons so there's a very interesting relationship completely hidden I mean if you stare at the the rules for general relativity or the rules for gravity the rules for gluons this fact is completely on obvious the only thing that would make you think there's a relationship is just the glories of spin 1 and graviton selves spin 2 so in the absolute dumbest sense you might think that two gluons going like that would kind of look like a graviton which is of course just super lame because just move them a little and they don't anymore right so that's not that that can't be it but that's that's the beginning of what what gives it a chance of working ok and and and that that relationship has actually been seen and there's something deep and important about it so it's and it's actually the way strength or you'd like to think about gravity's fundamentally is squaring what you get from from gluons so so so for instance if you've seen any nova specials you'll know that that gravity is associated with little closed strings like this gluons are associated little open strings like this well but you know a little closed string is like two closed strings glued together like that and so on okay so so that's why in some sense it seems like gluons might be the most primitive sort of basic object that then get get get transformed into gravity in in in some way on the other hand there's something against that which is just that that the gravity the gravity answers directly have even more structure in them than you would expect so I'm giving you no clear answer to your question but I can tell you we don't know anything like an amphitheater not even close for gravity never mind for strings but there's lots of suggestive links between things that have been seen in string theory the squaring relations or other things that says that that if we're mucking around the right neighborhood for gluons we can't be too far from saying something interesting for gravitas well thank you so much so before you go we have two gifts for you one is a framed copy of the announcement of your talks I'm like oh thank you members of the General Committee on behalf of all the membership thank you you're saying copy of Volume one of the Fiesta you bought and well you wanted 1871 where you're going so you can learn you can learn many things among which are the original members and and why they should have called the PSW science instead of what they did go out thank you thank you very much thank you while I'm handing out volley sign volumes I think Emily is in the audience somewhere and she can come up and get any signed volume - now before we go there are just a few housekeeping announcements first and foremost thank you to all of our members sponsors and supporters the SW dispense up depends on them and if you're not a member please join if you want to join it's pretty easy you can just go to the PSW homepage which for the time being looks like this but pretty soon thanks to our our web overseer Jared McQueen that's going to look a lot nicer but you go to our web page and there's a little button that says membership and you push that button this is when you'll get a membership application surprising hey and you go fill it out and go down to the bottom and push the submit sign-in button and that's not will come up it'll come up is the payment page a payment page will come up and you can pay with a regular credit card don't be confused by the paypal logos that appear on the page PayPal is just our bank clearing a service for credit card payments just look for your usual credit card logo and and fill out the form and pay your dues and that's all there is to it really right and there's no IQ test in any way if there were one anybody and to hear this lecture would pass and if you are a member and you haven't paid your dues please pay your dues our next lecture and the 2,380 fifth meeting will be on Friday December 15th right here in the Paulo auditorium this would be the last lecture of 2017 his people will be Douglas Smith of the University and he will be speaking on the topic of metamaterials Cornell which can be used to make just cloaking devices or horrific lenses among other things Doug is the leader in the field of now structure materials that have properties that are impossible for conventional materials among these are unique optical properties of lossless refraction frozen light and cloaking devices technologies based on such meta materials are going to advanced many other areas of science and enable magical materials and devices in the marketplace the spring 2018 kind of lecture series is under construction it's almost completed as of now our speaker for the president's lecture on January 5th will be Margaret Lehman who is the Dean of the Scripps Institution of Oceanography and the vice chancellor for marine sciences at University of California San Diego she'll be speaking on some recent very interesting developments in oceanography and about some of the unique institutional facilities at sio that make these advances possible on January 19th we have a young and very increasingly important scientist Aviv Regev from MIT she's a Howard Hughes Medical Investigator and she has an appointment at the browed she's going to talk by the catalog and diversity of cells she is a fantastic young researchers develop methods to do whole genome expression profiling on single cells and to do it on large numbers of cells in parallel her work is rewriting our understanding of how many different kinds of cells there really are and how much a given type of cell varies in its gene expression profiles and other characteristics it's very interesting work well worth hearing about on Feb 9th we have Christopher Ralston from gwu on faking cultural heritage the Israeli for jury trial in particular Chris is a brilliant linguist capable of rubbing a few feathers with the facts he likely will be telling us about the trade and antiquities and in forgeries including how we detect them and about the ways in which antiquities frauds impact scholarship and when they have religious significance communities of believers on February 23rd we have Thomas the Virgin of NASA and he will be speaking on a topic that we don't know yet but probably has something to do with space and rule null of Harvard will be speaking on life on Earth the deep history it will be interesting to see if he found any self-replicating RNA enzymes for those of you who are at the previous lecture but he will certainly be speaking on identifying studying fossils that constitute the remains of the earliest living things so far detected it's a subtle and challenging endeavor and I'm sure you will find it interesting to learn about these far distant relatives or at least these living creatures who might or might not be far distant relatives of ours and whether and where we might find the residual of even earlier forms of life on our planet and what will it tell us about finding life or signs of life in other places off of Earth on April 6 we have Geordi Puig swari from Cal Poly and he'll be talking about cube stats and he should be able to tell us a lot about them since he is one of the inventors of them and then finally on May 18th skipping the two dates that haven't been scheduled just yet we will be having a Cassini special sure many of you know a lot about Cassini and it has Metis ends in the gravitational and exotic and very horrible condition of Saturn which they plunged into not too long ago so we're working hard to make this year's Joseph Henry lecture a set of several presentations on Cassini by scientists who brought this space vehicle into being goddess to saturn oversaw its navigational gymnastics and took fantastic pictures of the planet itself its rings and moons and have interpreted the vast rich ocean of data that Cassini sent back to us during as many years inhabiting the Saturnian system so with that I will entertain a motion to adjourn the meeting to the social hour which usually ends at 10:30 but I think we'll extend it tonight to 10:40 do I have a motion by a member Erik do I have a second Karl all members of favor of journeying to the social hour all members opposed we are adjourned to the social hour

Channel: PSW Science

Views: 167,392

Rating: 4.6825395 out of 5

Keywords: PSW, quantum mechanics, physics, space-time, particle collsion experiments, Large Hadron Colider, Nima Arkani-Hamed, PSW Science

Id: qTx98PUW6lE

Length: 127min 10sec (7630 seconds)

Published: Mon Dec 04 2017

Reddit Comments

[u/Andos]

The actual talk starts around 14:20 into the video

[u/dougb]

That was outstanding. He's a great talker.

[u/[deleted]]

Cool. Thanks for sharing.

[u/callingallplotters]

understood 90% of this. not.