Our Mathematical Universe: Brian Greene & Max Tegmark

hey everyone welcome to this live session brought to you by the world science festival and in fact those of you who have been avidly watching some of the sessions that we have been putting out to the world over the last whatever 16 18 months or so will note that my background is a little bit different from what it normally has been for the most part i have been coming to you from our home in upstate new york where we had the bucolic rolling fields of green or snowy plains behind me as the seasons change now as you look behind me you see that we have a somewhat different a different view this is the view of manhattan i'm on the 19th floor of the interchurch center in uptown manhattan which is the headquarters of the world science festival so this will be our background from time to time as we begin to migrate back we hope to ordinary normal life who the heck knows so with uh everything that's going on in the world but we'll press forward and look we'll find all of us will find our way now some of you may know that about two weeks ago and in fact not about exactly two weeks ago we posted the first of our programs created in a virtual environment since we can't have our usual live programs in front of a live audience at least not yet maybe sometime in the not too distant future that will be possible again and that was a program called does math reveal reality where we had a interesting conversation with a variety of perspectives on what mathematics is whether mathematics and reality are somehow the same or whether math is just a description of reality whether math is real whether it's something concocted by the human mind the human brain excuse me so that was an interesting conversation now in that a number of you raised questions and indeed inspired by your questions because we do listen to what you guys say in the comments so long as it's positive we tend not to listen to the negative ones no we do that's that's facetious we listen and we read all of the comments but a number of you wanted to hear more about one particular perspective that was articulated by max tegmark in that conversation so indeed that is what we're going to do today but first let me just give a quick advertisement for the next of our programs in that virtual theater the virtual space and that will be a program i'm not exactly sure what we're going to call it but it's a program on on language and the nature of language where language comes from and why we speak and the role that language has in shaping the kinds of things that we're able to think about and whether or not language is the substrate of thought or whether language is a tool of human communication participants in that program you sort of couldn't have a better group to debate and discuss these issues noam chomsky right i mean noam chomsky the grand master of language and master of many other disciplines as well was part of that program stephen pinker again many of you know him from his many books on language and thought more recently focused on other issues the level of violence in human societies across time that have really sparked a lot of interest a lot of discussion we also spoke with evelina federenco and daniel dorr scientists who have been investigating the nature of language both from anthropological sociological but also from a neurological stance examining mri and fmri images of the brain when it's undertaking various tasks some language related some not and seeing parts of the brain that light up and talk to each other when these kinds of activities are being undertaken inside of the head that program is going to be released i believe on september 16th so keep an eye out for that program and that rhythm two weeks ago does math reveal reality now this conversation that we'll have in a moment with max tag mark in two weeks from now the language program that will be partly our rhythm but our goal don't hold me to it immediately because it's in process gearing up but our goal is to have weekly programming not not every other week i never know if that's bi-weekly or semi-weekly perhaps we should have investigated that in the language program but no doubt in the chat somebody will tell me which of those is the correct phraseology but in any event we hope to be weekly but for the time being it'll be every other week so tune in for all of that programming going forward and i can quickly say i believe that after the language program we'll have a cosmology program a discussion with alan guth andre linde and we'll probably follow that up with a related cosmology program that will give alternative perspectives to the viewpoint that guth and linday will espouse in that upcoming conversation one quick thing i'll mention or encourage you to provide thoughts on this language program i mentioned i'm not sure what we're going to call it we're thinking of it as language and thought but if any of you guys have a more catchy title for a program that investigates the origin of language and why we speak and the role that language has in human thought human cognition give us your title we'd be more than happy to give you credit where credit is due but give us a catchy title if anything comes to mind for that language program that is upcoming okay with that little preamble let's now turn to the main part of this live session which is a conversation with my friend and colleague max tegmark who i believe is already with us i see him there in the waiting room so i will alert the folks here behind the scenes to bring max there he is max how are you doing so great to see you again brian virtually yeah exactly and thanks uh thanks for taking a little time to uh discuss things with us here today i mean people were quite um enthralled uh angered uh agitated uh interested by the conversation that we had a little while back that we put out to the world two weeks ago and as i mentioned in in my introductory remarks your position your position is one that people really wanted to uh investigate a little bit further and that's what i'd like to do today but before getting there if you don't mind just a little background on on on who you are where you came from it's always good to frame the conversation so it's always you know it's always mystifying to to you know tracy who you know my wife that we physicists know so little about each other from the personal perspective i knew that you i know that you grew up at least in part in sweden in stockholm but i don't know much more about your your early background than that so give us a a quick sketch of of young max tegmark yeah so i was born in uh i did kindergarten through college and mostly in stockholm sweden and i discovered as i was lying in my hammock that i had put up between two apple trees you know as a teenager that i just loved big questions and and the bigger they were the more on fire i would get about them and um so it was pretty natural that i gravitated towards them and when i came to grad school i you know i fell in love with travel as a teenager and i thought hmm if i'm gonna spend any more time in school why don't why not combine it with some cool travel and i felt so lucky when i got admitted to go to california do grad school in a different country pack my bags and then i saw a poster in the elevator once at uc berkeley saying there was a course in cosmology and hadn't even dawned upon me that there was such a subject before i immediately thought wow what bigger questions can there be than about the cosmos so i signed up for it and and joe silk who thought that course ended up being my my thesis advisor and many of the conversations that you and i have had over the years of course have had to do with these great questions about our universe and its origins and how big is it and and is that all there is but that's not the only big question in fact back when i was in in that hammock between the apple trees is that in a metaphorical hammock or no and it was the real hammock between two apple trees the cloth had deteriorated enough that the other year when i put it up again it actually actually fell through it but my industrious version of newton in the apple right niece sally put up a new one a more modern fabric and i was lying in it actually just recently and i used to think back then that um the two biggest questions actually were about our universe out there and a universe in here and we will be talking i think a fair bit of that also when we talk about the nature of mathematics and whether it's invented out here and whether it's out there and whether math also can describe not just the motion of planets but also mental things like intelligence and consciousness and and throughout my career just to wrap up the answer to your question you can see the first 25 years or so i spent very much going on this outward journey and in the last five years i've really shifted my research on this inward journey my research at mit with my group now for the past five years on artificial intelligence mostly and another area where mathematics has proven able to conquer new ground in science yeah things which we used to think were beyond mathematical description and now we can do it in our in our computers now we'll we'll move on in just a moment i'm just wondering as a kid were you a math kid i mean was math your thing or was that something you came to later on i liked math uh i i thought it's fun but but um uh didn't do much with anything particularly with my my my late father math professor so i feel the love for math from him and and later on uh i had many many fascinating conversations about him not not so much about how to solve equations but about how did he think about what math even is and that certainly influenced me a lot but i i had a very um trajectory through academics like my undergrad was an economics you know go figure oh gosh i didn't know that yeah and there are just so many interesting things you can think about right and now you have a professor salary got your econ friends to be like what did you do max god what a mistake that was it's crazy and then i get to spend all my day thinking about whatever interesting things they want then that they even pay me for it it's quite scandalous yeah right now that side of it is utterly astounding yeah so anyone listening to this wondering about whether they should go into academia or not i highly recommend it yeah yeah well i can't say that i have any other view than that the freedom of life and thought that comes from the academic life is uh second to none but anyway let's turn now to um some of the issues that came up in our previous conversation and uh let's not assume that people watched the previous program although i encourage everybody who's watching this to to take a look at math and reality as it really did cover a lot of ground but i think it's fair to say that you and i while we see eye to eye i think on many things just from the conversations we've had over decades i think there's a lot of alignment between us i think when it comes to mathematics we we have radically different views um and i should preface that by saying there was a time when i think my view is much closer to yours that that math is just out there and we discover it and so forth and i think for me i mean you discussed how the last five years you've sort of had a bit of a shift in your focus i've certainly had a shift in my thinking about things over the last five ten years which has led me to a different view but we'll come to that let's let's begin with your perspective so when you think of mathematics you think of it as much more than a human description of the external world so perhaps give people a flavor for where you see mathematics fitting into the ontology the real stuff of reality yeah so i like how you describe there's this being a spectrum so if this is the spectrum of views you can have on the nature of math right then one extreme is to be here and say well math is just all in your head it's something we've invented it has very little to do with the physical world i'm going to be defending exactly opposite extreme case it sounds like you've kind of moved maybe from here brian when i last spoke to you to hear yeah i'm not very interested in hearing the arguments that drove you there i when you look at the bigger picture it's this is not the new idea obviously and already over 2 000 years ago the pythagoreans were talking about how there was something special about math and galileo you know famously about 400 years ago said that our universe is a grand book you know written in the in the language of math so he was already pretty far over on this side before we go any further i think it's worth just that we clarify for for our viewers here what he even meant about this because when you look around the world like what are you what skelete are you even talking about i look behind you i see clouds you know like i don't see any numbers written there except it says live 16 colon 2 2. that's mathematical but that was put by humans no what is there actually in the world behind you that's that has mathematical properties and it's really not evident at first except when you start looking through the eyes of a physicist because then what i see when i look at you brian is a blob of quarks and electrons no offense that's a compliment you take that as a compliment okay and if i look at you know your electrons like what what properties do they have you know that your electrons have the properties minus one one half one and so on and you also know that we physics nerds have fancy names for those properties like electric charge spin and lepton number but we made up those names what they call them the properties of electrons are just the numbers and as far as we can tell the only difference between your electrons brian and your up quarks and your down quarks are what numbers those properties are right and when the space i see you sitting in there you know that all those particles are in what properties does the space have well three for example because that's the largest number of fingers you can put that are all uh perpendicular to one another right yep and again we humans invented in our language a word for that we call it the dimensionality of space and we measure it and it's three but the property itself is just the number and then einstein came along and said well there's some more probabilities of space also topology and curvature which you know we study in math class because they're also just mathematical so if you take seriously that all the properties we've discovered that the stuff in space has and the space itself has are all mathematical it starts to sound a bit less ridiculous the idea that maybe it's actually universe has only mathematical properties that's the position that i'm going to be defending here so along those lines though and um i think it's a kind of an issue that we need to chip away at somewhat slowly because it is what you're describing is is is for some certainly for me uh a different world view right um and that is curious for me to say because i'm fully on board when we talk about a mathematical description of the particles you know i teach my students and you teach your students you know we stand up there we teach quantum mechanics and quantum field theory and it's certainly the case that when we're doing that we describe the particles using the minus one for the electric charge and then we talk about electromagnetism using even more fancy mathematics that some of our listeners may be familiar with you know a u1 gauge theory right now all of this is is is mathematical structure with the ingredients fully described by the numerical values that you made reference to charge spin and and so on and so forth but for me and i think for some many perhaps what we are talking about is a description of those particles yeah as opposed to the particles themselves and that may sound like a fine distinction but obviously we know it's a kind of huge distinction so to to articulate the issue in a nugget doesn't the electron have one other property that those numbers don't quite capture which is existence right it isn't just the possibility of a particle with charge negative one and you know spin a half and so forth it's a particle that exists in the real world that has those properties so so don't you need more than just the mathematics to go beyond abstract possibility to real existence that's such a great question so let me let me say two things about that first of all when you teach your quantum field theory course right at columbia then you don't just teach them that the electron is a particle you actually say that the real thing that exists is rather this thing called the electron positron field and there is also something mathematical there a number called the occupation number that tells you how many electrons there are in each momentum state right so now whether the electron exists or not just comes down to whether there is a zero or one in a certain place so i think it's not the existence so much that's at the rub of this but there's another question that just you hit out there which is really core and i i think of it as being a little bit related to how humble we are as humans if you take for example um you know my my dad passed away earlier this year so i'll pay tribute to him by by telling you something very cute he asked me once when i was a kid he said max jupiter how do we know that it's called jupiter this planet and we haven't been there i might have been five years old or something i went away thinking about this for a long time he had this wonderful strategy of asking of me questions he knew the answer to but letting me think and if you ask me you know did we invent jupiter or did we discover it right i think it would be really arrogant if we claim that we in that we invented it jupiter was clearly out there for us to discover right and why why is that well it's we we feel that way because jupiter has additional properties there's there's beyond those that we have discovered already and catalogued and so on there's but let's contrast that with something with us playing suppose there is some super advanced computer game in the future because ai keeps progressing and it's so good that some of the characters in this computer game are can have the kind of conversation with each other that you and i can have and they'll feel conscious and aware and so on and one of them looks through their virtual telescope and discovers a new planet in the computer game uh and then they start discussing well did we discover this planet or did we invent it and one of them says well you know we we just discovered it because it exists out there you know to you and me though this whole computer game is just a bunch of zeros and ones yeah and in some sense it's that planet isn't any more real than any other math in this thing and and the uncanny feeling i have been getting the more physics i've done over the years is that the we keep discovering that our reality is more and more like this kind of computer game world where we look at things where we were pretty convinced that there was more to it than just the math mathematical properties and then eventually all the other stuff sort of milled away like we we look at the we look at the jupiter and we realize we can describe the whole the whole thing seems to be made of electrons and quarks in some certain arrangement we then we thought well what about the fact that brian greene is talking to me right now and being very intelligent surely that must mean that there are some other properties of brian that can't be described with math but now artificial intelligence research is even challenging that right it's it's it's not at all obvious that you need anything beyond the list so that i i i fully agree with but if we don't leave your simulation example quite so quickly i'm just wondering so if i go into a virtual reality experience and in that virtual world which is very much like your simulation but at least it's one that you can actually do right now and in there if i go through and and take my virtual reality telescope and i'm looking at jupiter right jupiter of course is just zeros and ones in some elaborate computer program that's creating this right simulation of but that jupiter is not real as the real jupiter is like you wouldn't want to conflate those two ideas even though each has a mathematical description right the mathematical description of jupiter in the virtual world is responsible for my experience in that headset the mathematical description of jupiter in the real world allows us to articulate the trajectory of jupiter and its reflectivity and all that sort of stuff but wouldn't you want to draw a distinction between them that must somehow go beyond the mathematical representation because they're not an equal footing or or are they well if we know that we made that super intelligent computer game then and are looking at it from outside we know of course that they're not on an equal footing we know for sure that that virtual brian green is zeros and ones but the first question we should ask is does that does he know that right does virtual brian realize that he's a simulation it's not so obvious to him right if we program in laws of physics there are the same as in this world he's going to touch himself and he's going to feel this feels really real and if if someone slaps you you know it's going to feel very real and and and then if that virtual brian starts to study the laws of physics and discovers you know the standard model of particle physics uh he's in the same epistemological yeah logical situation that you are so it's not so easy for someone inside right and and what i'm saying is we find ourselves in a situation like this that so far i would argue and this is a controversial thing i'm saying which you should feel free to push back on but i would argue that so far we have found no phenomena at all in science where we're convinced that that we can that they cannot ultimately be described with the tools of of science you know physics and math and some people would disagree and say maybe consciousness is different or or maybe something else but i think it's up in the air but i think we're on the same page regarding i don't expect us to hit a wall so one day suppose that's true that there is no roadblock and that all the phenomena we observe around us can ultimately be described with mathematical equations and you know maybe they're even elegant enough that one day you can have a t-shirt that you can give away to people at the world science festival that have them on it you know then where does this leave that leave us right uh does it mean that we're simulated and that the simulators decided that these were the equations they were going to put into the super computer because that was the most important interesting and fun game they could make you know some people think that and and write papers about it or is it the case that you don't even have to simulate it so that's where i got really really interested in you know if you if you talk to physicists we are physicists right when we ask questions about what exists or not you know we very much start with the kind of stuff we can touch and and kind of build on that but when i talk with uh for example my my colleague david vogen at mit he's a mathematician right he has a huge poster in his office of this 10 dimensional league group he spent like in this league group he spent like 10 years mapping out this mathematical object he loves it that's his it's like his baby he feels that that exists you know just as much as he feels that i exist and um see i would say it exists in his head and it can ex exist in other heads and can exist in papers and in textbooks but i don't know what it means to say that it exists beyond that and i know again that's a controversial nominalist perspective on things but you know perhaps it's worthwhile you you noted you noted that your view yeah comes from a place of humility to somebody yeah and i feel like mine does too so let me just let me just tell you where we're it's a different kind of humility so my view and this is the reason why my view has changed uh over the years i've begun over the last i don't know decade to have a clearer and more consistent maybe that's a better way of saying it or more consistent to my mind world view where i look at the continuum of processes that starts from the big bang to the existence of stars and planets galaxies one planet certain macro molecules that evolve over time evolution by natural selection they become a more complex form and that more complex form somehow begins to have self-awareness again we don't really know where that comes from but i assume it is just physics in some way shape or form let's just go everything you said except the word just okay good good good let me take that out on it good it's not essential to anything i'm talking about here so it is very cool it is physics happening exactly so so so the humility that i get from that perspective is when you look at things in that you recognize that we complex collections of molecules who are granted through physics this self-awareness ability to look out at the world we try to describe the world and to understand the world and and we invent natural languages in order to communicate with each other better and then we invent mathematical languages i don't have a temporal quality here but mathematical languages are invented because they have a more precise capacity yes to articulate the patterns but it's all happening because we conscious beings are trying to give a coherent description yes of the external world and we are just the same quarks and atoms and so forth that everything else is made up with the one ability beyond a rock or a chair that we can come up with these descriptions and the mathematical description is the one that we come up with and so the math comes from our heads it's spectacular that it is able to give us such a precise description of the external world but to think that we somehow are tapping into something that is uh the deeper level of reality that to me is is hubris right the human reality the humility of recognizing that all we are doing is giving a description of the world seems to me a a more consistent coherent picture and one that's more humble i love this yeah i can i think there's a you can i love one of the reasons i like you so much is your humility and i think humility can also bring you to the other direction side of this frankly because um we both agree i think we must not conflate the description the language of mathematics with which we describe which is a description of things with what is described right and um we've we should probably say a few words about what we even mean by mathematics right in other words we talk about whether we live in whether the universe is math or not so that's changed a lot in history right it used to be that math was just this cookbook of tricks from multiplying numbers and you know my mom used to view it basic mathematics basically as a sadistic from a torture that they use to make kids feel bad in school but if you talk to modern mathematicians today right they think of mathematics very very differently as simply as a as a study an exploration this study different mathematical structures that are out there like the one david vogen had on his wall and for example plato right over 2 000 years ago was very interested in what kind of regular three-dimensional shapes can you make with beta polygons are all the same and he realized that there are five of them the tetrahedron the cube the icosahedron the dodecahedron and the octahedron and then he went off and also speculated that that's what the four or five elements were made of and he didn't get chemistry quite right but but the thing is so you can ask did he discover or invent the dodecahedron i would say i would claim he actually discovered that there were five of them he could even if he wanted to he couldn't make there be a sixth platonic solid there just isn't one right wouldn't you i don't mean to interrupt but wouldn't you say that he deduced it from a certain set of assumptions a three-dimensional world you know the rules of mathematics and so on and so he deduces it from those assumptions and that deduction to me is a process of invention as opposed to a process of it it's out there and i just sort of pulled the curtain back and there's the joe decahedron well if you it would be so cool if we could get plato on this show and see if he's coming in just a lot about sitting in this cave and imagining that there was this reality out there that he was discovering right and and and his platonic realm i think he envisioned that you know there are certain mathematical structures that exist and some that don't and he was in the process of figuring that out and the key point i wanted to make was regardless of what you call this process right no matter how much he wanted he had the freedom to call the dodecahedron the schmodekahedron or something else because that was the language we invent the language and we can call the things whatever we want but he didn't have the freedom to just make up a sixth one that doesn't exist and the way so one one question i think is really good test for whether it makes sense to say that something exists or not is i think you should only say that something exists if it's logically possible for it to not exist like brian green exists in that you can imagine a world it would be a sad world where brian green doesn't exist right thank you but i cannot imagine a world where there are only where there are only four platonic solids and the dotica heater just ain't there does that make sense it does make sense but i guess i would perhaps challenge your criterion for existence so your criterion for existence is to be able to establish logically that the ingredient that you're talking about could not not be there and but i would say i would be more convinced that something exists if if you gave me one and the fact of the matter is there isn't a dodecahedron in the real universe there are close approximations yeah dodecahedron in the real by real universe i mean i could like touch and have some causal interaction with shine light on it see it through reflection and have it in my hands so it doesn't even exist in the in the right now max doesn't need mix i don't even see it looking like really and i used to have behind me here as well you do okay you know so so whatever you show me is going to be a close approximation but i would say all this is happening in the mind because the things that we're talking about they don't even exist but i think that's let me push back on that being a bit too hubristic because you know space is the big place you're going to have alan guth and andre linde on here and a couple of weeks telling you that space is bigger than the part we can see right yep i even have on my t-shirt the some multiverses here so suppose there is a there is another brian you know brian green the second and he just happens to live 50 billion light years away on a planet that looks a lot like earth no there are things over there that we can never observe who are we to be so arrogant to say that that stuff doesn't exist just because we can't observe it right it's in in our same space you know the humble thing to do to me would be to say well if you can touch it brian green ii and feels it exists and he is just as smart as you are yeah i'll grant him that that's also real so i don't want to limit existence to just things that we can physically but when you say that if if that distant location is governed by the same laws of physics and has the same ingredients and any conclusion we draw here is reasonable to power i agree it's a guess that it would hold over there too so i would be pretty shocked if if that other max or brian could actually say no no here's a here's a real perfect dodecahedron exactly as the mathematical description articulates yeah but what if what if there is a particular artifact that he has succeeded in building and nobody in our universe has managed to make right yeah then we would say it doesn't exist then he were like hold on here it is yeah i i agree i agree i agree i agree in principle but i i guess i have maybe a more flat-footed notion of existence where i want to have some interaction that at least is in principle possible with the thing whose existence i'm going to claim to be really aren't you saying then that you're going to deny the existence of his beautiful dodecahedron that he spent 20 years building because you can't even in principle interact with it because it's 50 billion light years away yeah um uh i i i get the point but i don't find it convincing because it's making use of a oblique quality that the object is just too far away for me to have a causal engagement with it and misrepresenting you okay are you saying that you're denying it you won't agree that it exists for that reason or that you're willing to concede that it exists i'm willing to concede in the existence of things that are too far away for me you know so so that that's not something because i i full well recognize you know from all our discussions of cosmology that it's quite possible and quite likely in fact that space goes on far beyond the observable part of the universe and i'm not going to say that a star that's beyond the cosmic horizon doesn't exist because i can't see it that that's not a position i'd be willing to take well but then it seems like you've softened your your position that i thought you had a few minutes ago that you're only going to say that things exist if you can actually touch them or interact with them or observe them right yeah but i really mean there is an in principle version of that and so you know if i was to be transported beyond our cosmic horizon i could see that star and so forth i don't think that there's any space-time event where i could be located where i'm actually going to see you know a perfect cube or now you're going to say to me how do you know that that's an experimental question and and i agree that it is an experimental question but i can't even envision it happening in our observable universe and since i can't even envision it even in principle happening then i'm less convinced that simply by transporting myself you know a billion light years from here all of a sudden it's going to be an experience i can have to interact with this dodecahedron okay so but did you i hope i conveyed how i i view the opposite uh storyboard there's also more humble because i think the austro the proverbial ostrich and i think that's an urban legend actually that they stick their head in the sand and claim that nothing exists at the company but you've heard the legend uh that would be very arrogant yeah the opposite of humble to say if i can't observe it for sure exist and i think we've made that mistake as a species actually many times right assuming that everything we knew of was everything that existed just to realize that actually we live on this gigantic sphere here that's 40 000 kilometers around and oops in this huge solar system in this huge galaxy and a cluster of galaxies etc and our universe and maybe more and i you know alan guth and andre linde you're undoubtedly going to chat with them two weeks from now also about how this level one multiverse is probably not all there is it's just even more diversity in our space even in our own space time where there are other regions where maybe space even has a different number of dimensions and you couldn't live because the number of quarks are different and and so then i think we have to have a much broader we can we have to be much more open and humble about what things we're going to grant existence to but will you grant existence to something that is permanently beyond the capacity to have a causal interaction with us human beings even in principle because i think you know the traditional platonic realm where say the perfect shapes the perfect square the normal not normal but the view that i've often heard articulated is that is a place that exists but it's not a place that even in principle we could have a causal interaction with because it's beyond space time whatever space time or it could be yeah so since i've been picking on you here let me make myself vulnerable and stake out a position that you can attack then because this is the perfect segue to this so you just mentioned space time right where is space time exactly it well what einstein said right was not that uh there is a certain place you go beyond a little bit beyond neptune and then to the left and that's where you find space time you had to say well we're in space time the position that i'm ar that i argue for example in in that subversive uh book i wrote on the topic is rather that if you take as a starting point that there are these mathematical structures that have mathematical existence like the perfect odecahedron the perfect cube some columbia et manifold et cetera mathematicians basically make a living out of discovering different kind different mathematical structures that correspond to different axiom systems and so on and they've cataloged ever more complicated ones and today they even use computers sometimes to catalog you know new ones if you were to grant existence to those you can call it for now just mathematical existence to not conflate it with the kind you're comfortable with okay and now you ask the question um suppose one one of those mathematical structures that you've granted mathematical existence to actually describes the equations that this the same exactly is described by the exact same equations that we think describe our physical world what's it going to be like there there's a then presumably there are people in there and what are they going to experience their life as i would posit that that the brian green is that in there is going to feel subjectively exactly the way you feel so that this mathematical existence implies subjectively to its inhabitants uh brian green existence that you think is bona fide a okay you know physical existence right and in that case who am i to come to that brian green and be arrogant to him and say well you don't actually exist sorry you just feel that you do you know right um and um i think it's look part part of the uh the subtext here is to what extent do we equate the feeling of something being real with something actually being real which of course takes us to the whole question of consciousness because um but before we go there i just want to make sure i fully understand your your perspective because we've sort of hinted at it but it hasn't been put out fully on the table if i understand again i should i should probably mention to the audience a lot of what we're talking about here is in max's book which is actually we borrowed the title for the title of this session our mathematical universe so it's a great read so if anyone want to go a little bit deeper uh max's book is a place to go but in that book you stake out the position that that we're sort of been walking the periphery of which is any mathematical object exists perhaps in a way that is outside of the observable universe that we are aware of so it's a kind of multiverse of a very extreme variety where any mathematical entity has an existence in this larger landscape this larger multiverse of reality is that a an accurate representation of of the view that this perspective takes you to so if you if you um take this rather modern view of mathematics that that it's about mapping out these mathematical structures right then mathematicians have actually a very nice definition of what they mean for something to exist mathematically hilbert said it most succinctly that it's freedom from contradiction you know if you have the axioms that you put in ultimately contradictory the thing goes poof and there's nothing there and it's remarkably hard actually to come up with a system of axioms that is consistent and actually describes something that mathematicians would consider it to exist and that's why that mathematicians get so excited when they discover like a new lead group or a new columbia manifold that they can can study and um it's it seems to me that everything we've seen in the history of science so far is consistent with the hypothesis that we live in one of those mathematical objects and what we call physics theory physics equations are just discoveries of ever more accurate approximations of the properties of this thing that we actually live in you know we were first we got all excited about newton's gravity which clearly it was an approximation then einstein gave us a better approximation but we know that can't quite be right either with general relativity we still don't have the exact description mathematically of where we think we live in but if we did we would have a theory of quantum gravity um but um this is this is my guess is the what's what's actually happening that it's we're not um discovering physics approximating mathematics we're discovering mathematics approximating the true mathematical properties of of what we inhabit and we didn't it's if you think about it this way i know it's very counter-intuitive and and you've articulated better than than virtually anyone else also how complicated the whole time issue is in this right because when you talk about something existing you often think about it first not existing and then poof you know you create it um but you can't create space time there isn't the idea that there is first no space time and then later in time there is poof rather space time has time in it already the whole future and past it's all there and you know just either the whole thing just exists or it doesn't there's no no creation involved and stephen hawking has this famous quote what is it that breathes life into equations yes makes something exist that for them to describe i think that priest said that's a wrong way of looking at it presumably yeah i mean what do you mean make make space time exist as if you can create time itself right um in plate in this in this mathematical landscape you have to be very humble and realize that there are mathematical structures that are so different from the one we think we live in they did some of them don't even have time there's no time in the dodecahedron what's it like to live there um probably very boring it's too simple i'm pretty sure there's no self-awareness going on in the dodecahedron right at people one corner talking to another no sure but you are saying if i go across the street to colombia and i go to the math library and i pull any volume off the shelf go to a random page and there's some equation on that page that equation in your view exists as much as like this cup exists it it has the same level and same claim if i anthropomorphize unnecessarily to existence as anything else does is that fairly accurate sort of the the uh can i show you it's like a very very yeah sure yeah yeah dirty picture to just i i never feel i can understand anything unless i can make uh unless i can somehow visualize it sure yeah yeah i just want to show you uh do we the means of bringing up an image uh yeah we do either knock on wood so i'm just gonna share my screen here very very briefly so here we have a little picture that i want to show you and uh so here a little picture yes yeah i i made this back when i i remember that coming out just a little map of this of plato's landscape mathematical things so you know mathematicians have discovered these things that i've drawn as little blocks here that they call mathematical structures yeah the integers here's an o or the natural numbers is probably the one most of our viewers have heard about the mathematical structure consists of zero one two three four and so on and it has all sorts of properties that you can study and the plus and times and prove difficult theorems about and so on it's a different structure though from for example the real numbers or metric spaces or semi groups or whatever and and over time mathematicians have start discovered more and more of these boxes that are interesting and they can prove things about them and discover their properties and now some people think it's if you if you grant it to the mathematicians that they haven't screwed up okay and then there are all these mathematical structures that exist in this mathematical sense that they that they're not inconsistent now one one theory is well one of them is special different from all the others because god or the cosmic simulator or someone you know went up to it and and puts the magic smoke in and made it exist also for real maybe it's uh something related to what we we could describe string theory up here or whatever right and then poof now that's also real so that people who live in there will feel that they're in a real space and all the others are just illusory they're just figments of the mathematician's imagination um that's a tenable position i think some people have and that i think is the motivation of stephen hawking's question you know what was it that breathed fire into our equations and made a universe for them to describe um so john wheeler a huge hero of mine right um he really didn't like that very much he felt so sort of arrogant that we should think that just our stuff exists somehow and it felt that we needed to have some answer to this question about what was so special about ours and what i think we've seen again and again on a smaller scale was that there wasn't anything so special about earth there are also other planets yeah or our galaxy they're also others and so my guess is that it's the same exact thing here that you know what special about earth to us is that that's our home that's where we find ourselves and what's special about our box in math space is that that's where we find ourselves but the other ones are just as real in the sense that if there's anyone home there with this subconscious experience they're going to feel that they're in a real world and and if that's true right then suddenly there's no fire breathing required anymore and no longer need any distinction between physical existence and mathematical existence there's just the same right distance and if the mathematical structure exists then the only question is what properties does it have are the properties complex enough that there's actually life there and consciousness or not so i certainly agree that by having this vision that all the mathematics exists the same that it's on the equal footing and we just happen to live in one of the boxes and there are other by that certainly gets rid of this issue of picking out the one mathematical structure that we are familiar with and this is a technique that we've seen used in the past when i was an undergraduate i i took philosophy from robert nozick i think you're you're familiar with some of his ideas i remember well at the candidate yeah yeah right exactly because i was like the only kid in the freshman physics class that went to his office hour right so i'd sit there and and we talk about things and he would say like what are you interested as a unified theory i didn't know what i was talking about as a freshman i want to do unification and all these kind of things gravity and so forth and he said to me so let's say you're successful and you guys figure out the unified theory you'll still be faced with the question why that theory and not some other theory and so he said to me the only way that he could imagine addressing that was as you mentioned this principle of fecundity where all of these possible explanations are real and out there they're just out there in other universes so so i get the philosophical move and the power of obviating the issue of picking one from the many by saying that many are all out there but i guess i would say and it comes back to how we were talking about things earlier you described that as coming and i i know that you're genuine about this coming from a place of humility just saying you know it's just one of many i would just turn it around i just put it out there that to me when you think about mathematics as i was saying early on as the output of this long series of evolutionary developments that start with insensate particles in the universe that gain the capacity to think and then these particles come up with natural language and mathematics for those particle collections to then say i'm now going to take all the mathematics that came in here and assume it's real out there to me it's kind of the diametrically opposite view of humility it's like we have this idea and this way of describing the world and now everything i see you know yeah i i can see where you're where you're coming from there there but but we don't have to judge things based on humility i mean i'm not saying it's an important one though i mean first of all i would say regardless of whether this mathematical universe hypothesis that i'm pushing is true or not i think it's useful if there's a spectrum of stances you can take to look not just in the middle but to actually explore the two extreme ends also to intellectually see what the strengths and weaknesses are uh um that i i i obviously i'm not trying to be humble also i don't i like to make bets and i'm not gonna put a hundred percent of my money on on this being true even though i put a lot of it the second thing i think is worth emphasizing and coming back again to humility here i think this willingness to um accept the possibility that reality is much bigger than we thought is a humble idea yeah right right i think the copernican idea that everything doesn't center around us is fundamentally humble and i suspect that some of the resistance you see to people talking about even parallel universes are the first kind never mind this this crazy fourth kind i'm pushing uh are kind of incensed by the fact that they feel it it makes us humans smaller in the grand scheme of things and that's something i think we should just need to let go of you know i agree i bring that complete vanity get in the way of seeing the truth and yeah there's no doubt about that and and um then let's see if i can articulate your source of unease why you feel it sounds a little bit heristic it feels like you're saying that it's hubristic to assume that something that we have started to get glimmers of through this messy evolutionary process certainly would be like the perfect description of everything right so of course we need to be humble about that then i know you'll be the first to to concede that you don't know for sure the string theory is correct even though i would go beyond that even you know it's a separate conversation but i'm not yeah a proponent of string theory i i'm interested in its possibilities i don't think i don't know that it's right by any means but but stephen weinberg had a really interesting uh counterpoint to that actually where he says that the biggest mistakes theoretical physicists make is not that they right or some arrogant that they take themselves too seriously but they don't take themselves seriously yeah no there's an interesting view i remember reading that and having conversations with him about that yeah and just to give you my take on this you know would he have gone as far as you though i i'm not gonna i doubt it i don't take that to mean that we should be full of ourselves and assume that we're right yeah which what i mean is uh that when nature gives us some very strong hints sometimes uh which where it seems like our methods are working unreasonably well yeah it's a mistake to refuse to follow that evidence where it leads and we look how we've screwed that up big time again and again right from from aristotle's silly theory of motion to newton we spent over a thousand years where people were just refusing to take seriously the idea that maybe we should just maybe the laws of gravity that archimedes and others understood on earth actually applied in the sky you know right and then gamma had to redo the whole thing for the big bang because people weren't taking seriously the idea that maybe the the laws we had discovered of plasma physics and nuclear physics and generally could actually be taken back to the first second after a big bang um had they tried you know they would have seen wow you know it really works and and here i think we have a situation which is very analogous we've seen for the last hundreds of years again and again and again nature giving us all these hints oh now this is also described by math colors are described by math oh my goodness even atoms intelligence to describe a map it would be a mistake to just keep us missing this and i agree but but all of that could also one could say it's been pointing toward the hours of explanation been pointing toward a kind of unique mathematical structure that we don't have yet none of that has the outward spreading mathematical hours saying that all of the mathematics is relevant to reality it's all pointing ever more tightly toward one mathematical structure not all matter i think you're being unfair to yourself actually brian because you have done more than most people and shifting it from one to all you know in your in your awesome work on string theory where where you know thanks to string theory and people like alan guth and andre linde we've kind of requested one theory realized that actually there's probably this huge diversity of stuff diversity like in inflationary cosmology or string theory is all under the umbrella of a single mathematical structure so in inflationary cosmology we don't have the equations yet but imagine they were you know so it's einstein's general relativity some scalar field but it's one mathematical structure that gives rise to the many universes i don't know anything that points toward many distinct mathematical structures all being equally relevant to what we call reality that's the part that i don't see any evidence for mm-hmm there's maybe one piece of evidence there we could we could talk about but even without you going there i think wouldn't you agree with me that the trend has been though away from the one and more towards towards the many like for example when uh i remember when we celebrated uh andre linda's 50th birthday i sat next to ed whit and then he and i had had some wine and we were he told me about how he had sort of shifted his his betting pool away from the one to the many we have these numbers we measure really accurately like the fact that the proton is 1836 times heavier than the electron and back when i first met ed whitton he was hoping we could compute that number yes just on pencil and paper and then at that point he was like nah no it's probably just some sort of multiverse thing and there's diversity and i think it's too quick to say that we've gone from the one to the many and therefore that paradigm that template applies to mathematical structures agree to say i i that's not the argument i'm making i'm just saying that yeah i agree that no no i i would agree with the the the the tendency for people to take the possibility of other universes more seriously today than than before i would certainly need that point but then pushing it to the place that we're talking about that's a move that i don't see evidence for but let me change gears for if unless you have something you want because i just think that the the historical trend is is one of greater humility i think we you can ask what's so special about the number of eights you know why there are eight planets in our solar system that would have seemed like very little nine a while ago yeah and then neil degrasse tyson took up take us down to eight by demoting pluto but you know how can we predict eight from string theory nowadays it sounds ridiculous but it didn't seem ridiculous kepler you've seen probably seen his very cute model where he tries to pick radii of the planets by putting platonic solids yeah and now we're like no misguided i agree that those numbers and the radii of those orbits don't tell us anything about reality they tell us about our address in reality they tell us that we're in this solar system i agree that one and now it seems like 1836 the proton electron mass ratio is also probably just part of our zip code it could be an environmental quality as opposed to a fundamental number in the world and and i agree that that's an interesting perspective and you're right from a string theory or in cosmology perspective there are trajectories that naturally lead us to us i don't see the trajectories that take us from that to the fecundity of mathematical structures but anyway the point that i did want to make or have you get your view on where does girdle fit into this so if we are giving mathematics this this place of of reality and primacy girdle comes along and perhaps just bring the audience i'm sure most of the folks who are listening to us are familiar with girdles ideas but speaks to a certain kind of incompleteness of these ideas maybe give us a moment on that and then say does that have any impact on this perspective yeah so this is a fascinating questions so girdle came along and and threw a big monkey wrench into this quest to map out all those boxes of mathematical structures right because hilbert had said well existence is freedom from contradiction and he wanted to be able to prove for each mathematical structure whether it was consistent or not and then journal came along and said look you can't even take the integers with number theory and prove whether it's consistent or not you cannot prove that you can't prove that two plus two is five and this is really really really shocking so that means that for mathematicians they have to be very careful when they start talking about what actually exists mathematically for us though for this conversation i feel this is actually a pretty big red herring because what what journal keeps talking about is that we humans cannot prove that things are consistent if our universe could talk to us it would probably be like who cares uh uh whether you humans can prove that that i the universe i'm consistent or not you know our universe seems to be doing just fine without us it did fine without us for 13.8 billion years right and if we can't prove exactly all sorts of things about it it's not the universe's problem so but um does that not suggest to you that um thinking of all mathematical structures might be too big a landscape and that it should be curtailed to systems in which we can answer the kinds of questions that in these other systems would be on the reach due to girdles insights yeah so this is actually a fascinating controversy not really involving our topic about whether our universe is mathematical but within math itself you know but some people think that even though politicians have these very spirited debates against each other mathematicians all agree on all the foundations and that that is really not true right there has been this very spirited debate for over 100 years about what should actually count as mathematical existence and where people get queasy in math is where infinity comes in you know the famous uh leopold chroniclers once said that you know god created the integers all else is the work of man yes exactly because he really didn't like the business with real numbers with infinitely many decimal places computer scientists don't like them so much either because you can't store even one such number in your computer because you need infinitely much memory and and uh so i sometimes wonder you know i'm gonna be teaching uh freshman physics starting next week again and i'm gonna be doing integrals and all these things where i'm telling the students that infinity is real and and the position the distance between two points actually is meaningful to infinitely many decimal places but in my heart of hearts do i really believe that that's how the world is no i don't actually i i take very seriously what what you and others have said about quantum gravity that beyond the fourth the 34th decimal place distances probably don't make sense and that is probably just a really useful approximation much like it's much easier to figure out the sound that makes you hear me now if you treat the air as just the continuum where no matter how much you zoom in it's just smooth with a density and a pressure the truth is no it's a bunch of atoms which are very much finite uh but which is easier assuming infinity is easier so we do that i wouldn't be too shocked actually in the future if it turns out that um you know maybe when one of your grad students grad students discovers the theory of everything hey or maybe you will leave it if it turns out to actually get rid of infinity in a big way uh with with our current understanding there's some there is at least something curious that might be worth pointing out i mean we discussed we started by talking about the electron you know minus one and a half you know the quarks you know two-thirds so the very theory that we currently have yeah that does involve you know the issues that we're raising so the very theory that's our best guess yeah provisional guess kind of stands outside this notion of not involving the things that would run afoul of a of a girdle kind of blockage incompleteness does that concern you or you just say hey that's just provisional we're on we're enroute toward the final theory whatever it may be and when we have that it will not suffer from these issues yeah that might this is just a wild guess actually but i'm happy i would be happy to make a wager that if we do discover what you what you will sign off on as a as the theory of quantum gravity in our lifetime that it will not involve any of the girdling completeness issues you know it's pretty it pretty interesting hint i think that all the engineers and scientists who simulate our universe always manage to do that just fine on their super computers with finite number of bits right and whereas even if you're going to sneak a single real number in there it has infinitely many decimals and infinite bits you couldn't even input it into the computer let alone do anything with it so if if we can actually do all the computations with finite you know who's to say that nature can't also right right yeah no no i i i think fundamentally there's a resonance of that view with my own uh even though um again coming back to unique mathematics versus plurality of mathematics i think it's all pointing perhaps toward the uniqueness at least in our observable universe let me if you don't mind a few questions come in from uh the audience and and and just uh just to make it a little interactive um yeah it might make a dark confession to me yeah right between your audience and a faculty meeting here and uh if you promised not to tell my faculty colleagues i prefer talking to your audience yeah good good good we will uh keep that just between us folks right here um so and we also have this program world science scholars where we have kids from around the world who have exceptional mathematical talent who have an interesting program that we create from them a couple of those scholars have some questions so ahmed ali from qatar asks over the past few centuries it looks like the laws of physics have become more complex for example newton's three laws of motion and the inverse square law seem more fundamental and more obviously part of a reality than the collection of you know tens and dozens of particles complicated forces long equations that exist today the standard model and so forth so would you number one say that the laws of physics have become more complex and can you extrapolate from that to where you think things are going oh that's a great question i actually think it's been going kind of on a sawtooth pattern like like more and more complex than poof simpler and then more and more complex and then simpler and more and more complex and simpler let's take a concrete example of this so you know first there were just the four elements earth wind fire and air right and then it got more complex actually no that's not quite enough you actually need carbon and oxygen and nitrogen and by the time people were up to you know many many dozens of elements people like man what a mess then mendeleev comes along puts it all in a periodic table and then suddenly we got this fast simplification when it turns out there are only three things you need you don't need the hundred atoms you just need protons neutrons and electrons great you know so suddenly simplification then it got worse again then we started discovering well there's also other particles you know what about the k ons and the phi psi and the sigma particle and this and that and that and then another unification people realize actually these are all made of quarks and they're actually just six quarks and three leptons and and so on and maybe they are all made of ultimately a vibrating super strings or something like this uh so it seems to me like what the periods when things seem to be getting more complicated it's kind of that experimentalists are pulling ahead of the theorists piling on more and more evidence that we haven't yet managed to fully make sense of and then comes this click you know when the theorists catch up and realize that actually there's this new hidden simplicity where all falls into place again and and um i'm not i'm curious what you think actually do you think there's going to be a final click or where we get some theory where there's some ultimate theory which is actually really beautifully simple or or do you think the ultimate truth is actually a total mass no i think um if one means by ultimate theory the ultimate description is the way i would describe it going back to our other conversation of of the elementary ingredients and the forces by which they interact then i do think that there will be a final articulation of that particular story but whether that story is as exhaustive as we want it to be that's a question mark for me whether whether that will be enough at least in principle or whether we'll find that somehow it's not the full story but i do think when it comes to the ingredients and their interactions there will be um a final description and i find that we physicists and mathematicians are very good at taking an initial theory that might look very complicated and finding a way of expressing it in simpler language i mean for those of you who studied maxwell's theory electromagnetism you know it's often described as four equations that you've probably seen a divergence of e rho over epsilon naught and so forth and we can now describe it really in using differential forms as you know two equations but if you go back to maxwell's original papers which i did by the way oh you did right it's a mess it's a whole page with six different variables and for the different components of the field yeah crazy and it didn't even have yeah exactly so so as time goes on we are pretty good and in fact you know there's this famous image that i love to post on twitter now and then but people use it in all different contexts of the standard model of particle physics where every single term in the equation is written out and with very small type it's like you know densely packed on a page but then we can articulate it with you know a single equation if we're clever about the notation so and then it's more than just notation understanding the symmetries that relate the various terms allows us to express them in a more concise framework so so i do think that ultimately it will be quite simple whether it's full and and exhaustive i think that is another question um and speaking yeah eugene wigner another hero of mine had this interesting argument also about how we think about what's simple so i i have my mathematical universe t-shirt on to your to honor you today here where thank you illustrate that things usually look like most complicated on the human scale and if you start looking smaller and smaller it looks simpler here is tribute to you brian little string in a columbia manifold but also when you look out on much larger scales you start to see a lot of simpler things and and it looks the messiest exactly on our scale and and you know wegner talked about how traditionally we've taken everything that we could describe with math and so that's the simple part it's physics and everything else we call initial conditions and we say blame it on the historians and to say it's not our department we don't have to explain it yeah but but on your next show alan guth and andre linda are going to tell you that actually they can explain that because their inflation just makes all of the initial conditions somewhere all the same in some sense in that sense more is actually simpler because now the only thing that all the complexity is describing is your address in this big space and and the very properties of nature are actually simple yep um one more question from the audience i hope i'm pronouncing a name correctly michael lipiak from poland assuming that a world is a mathematical structure do you think it's possible for humans to unambiguously determine it or will it be physically impossible for some reason well that's a really really great question uh we've in the past sometimes been in the situation where we kind of almost thought we had it like when i showed you that little family tree of mathematical structures there was one that was three plus one-dimensional pseudo-romano manifolds obeying these certain field equations einstein was kind of hoping that that was it in in 2015 right with general relativity uh it was nineteen percent 1915 thank you yeah and oopsie of course no quantum mechanics put a stop to that and um it um i try to be very open-minded about whether we'll ev whether we'll get to the point where we can actually guess one that is the right one or whether we'll still be wondering whether there's this one that fits perfectly all the evidence but it could also be some of these other more complicated ones and the only experiment we can think of to tell the difference is so complicated you know we can't do it in our universe yeah yeah there yeah it might yeah it might also be that in some way we have yet to fully understand uh that maybe simple things it's some mathematical way exist a little bit more and have some more weight if you ask alan and andre about the measure problem sure a fascinating discussion about no doubt it will come up um yeah so me let me turn to one final topic um one in which i think we do uh a line perhaps completely but it'd be good nice wait face to end kick it around a little bit so you described your own trajectory focusing for a long time on the external world and then last few years focusing somewhat more on the the inner world of conscious experience and of course the big questioning consciousness so-called hard problem of consciousness and the language of david chalmers is how in the world is it that these particles that we've been talking about electrons quarks and so forth that we don't think have any inner world of experience themselves how can collections of them somehow come together swirl move in the right pattern execute the right choreography and give each of us this inner world that lives inside of our heads where does that come from how is that even possible yeah where do you come down on that question fantastic question let me say two things first why i'm so excited about the question and then what i think about it sure so why am i so excited about it if you had uh a time machine and you could bring galileo on on this show right he would tell you that he could describe beautifully with mathematics how a grape and a hazelnut would move if he threw them he could show you the equation with the parabola and all of that stuff but he would have no clue how to explain why the grape was green and the hazelnut was brown and why the grape was soft and squishy and the hazelnut was really really hard but then so at that point of galileo really of all the things you could try to do with physics there was very little you could you could describe motion of things and not much else right sin then maxwell came along you mentioned him and figured out all the stuff of colors with math and physics then quantum mechanics explained why the hazelnut is hard and why the grape is soft and so on and now we've gone from physics being able to to handle almost no natural phenomena to almost all of them there and what's the final front here aside from the the very biggest things in the very tiniest quantum gravity the the ultimate final frontier really is what's in here i think intelligence and consciousness and and um many people had for a long time thought that uh that was gonna be hopeless uh then our ai then artificial intelligence researchers started to show that you could replicate more and more of what we considered intelligence also mathematically in machines and uh we're still not at the point where you have to worry about your job being replaced by an ai but we have to start being open to the idea that intelligence itself is probably some form of information processing not any old information processing but some form and so it's quarks and electrons you know moving in very particular patterns but that is what intelligence is and so what about consciousness then many some people mistakenly i think put an equal sign between intelligence and consciousness which i think is a huge mistake you know there are obviously things which are intelligent without being conscious you your brain does a lot of very intelligent things that you're quite unconscious about from regulating your heartbeat to even recognizing me when you open your eyes there you have no idea how you took those millions of pixels on your screen and computed this was maxed you should have got an email from some unconscious module of your brain saying you know image completion image analysis face recognition task completed infusive workface area you know here is a result and then your consciousness module kind of got that right and so so that shows right there i think that consciousness intelligence doesn't have to be conscious and what about the other way around um can you have something which is conscious without being intelligent i certainly think so there have been times when i felt very dumb i was just sort of sitting gazing out over a beautiful view i felt very conscious of how beautiful it was but i couldn't get any coherent thought through my brain and my personal guess is that the answer to your question about what consciousness is is that both consciousness and intelligence are certain types of information processing they're not exactly the same type and that consciousness is basic is the way information feels when being processed in in certain ways so let me just unpack that a little bit here you know the the amazing thing which is powered the computer revolution is the insight that you can process information without worrying very much about what how exactly the quarks and electrons are moving around all that matters is the structure of the information processing and it doesn't even matter whether the zeros and ones are represented by you know how many volts there are on a capacitor which corresponds to how many electrons there are somewhere or whether it corresponds instead the some totally different physical way of representing it it's the structure at this higher level only that matters for how smart something is right and i i suspect it's the same with consciousness that there's some kinds of some structure of information processing which when it takes place has a subjective experience which which david chalmers has articulated so well so you know if if you're driving a car right you're experiencing uh maybe road rage if it's in manhattan you're certainly experiencing colors and vibrations and sounds and so on but a self-driving car is it subjectively experiencing anything at all does it feel like anything to be a self-driving car you know we don't know but i fundamentally think that this is a science question we have been a little bit too lazy to tackle properly and and uh my guess is that it has an answer that there are some equations maybe that um if information processing satisfies them then there's an experience there you know otherwise there isn't giulio tinoni has written down some equations he presented at a conference david chalmers organized there are others like scott aronson who think those equations are wrong yeah but the beautiful thing is that finally after thousands of years you know this question of consciousness has gone from being speculated about in bars becoming an actual respect the stable science topic which i think is a sign of this final frontier that's resisted the scientific description you know at least being a contender now for something that maybe we can describe now having mentioned both of us mentioned david chalmers perhaps it's worth just asking he beat his head against the wall for a very long time starting from uh i believe he was trained as a physicist i think so yeah and ultimately came to the perspective i i think he probably started his journey from a place very similar to the way that you've described things trying to push that perspective forward ultimately felt he couldn't do it and that forced him in his mind to conclude that our assumption that particles don't have any kind of conscious quality is wrong and that we do need to assign some kind of proto-consciousness quality beyond the minus one for electric charge and the half for the speed does that do you think we will be pushed to do that i i'm very i try to be very humble about this i'm guessing that he's wrong about that one and i'll explain why but i i i try to keep an open mind the reason i think it's not that way is instead of talking about consciousness let's talk about the property of wetness okay yeah so like this water has definitely has a property of wetness is it because it's made of protons and electrons and neutrons that are wet no right that makes no sense to talk about whether a single electron is wet or not right wetness is something is at a higher level it only makes sense to talk about in terms of the nature of how the different particles are interacting with each other my guess is that consciousness is very much like that it's some it's an emergent phenomena that happens only only exists at the higher level you can't talk about whether one you don't have to be able to talk about whether one proton is conscious or not but if you have 10 to the power 27 of them in your brain you know and they're doing this elaborate information processing it may very well be that that is conscious yeah the one thing i would say in that i mean i have to say fundamentally i do have a perspective that is pretty much in alignment with yours but just to be fair you know david would say and i know this because i've had the conversation with him that sure when it comes to wetness that's a collective phenomenon of the particles but in principle you could determine that objective third-party quality from our understanding of the objective third-party qualities of electric charge and spin and so forth but he would say when it comes to consciousness because it is fundamentally distinct it's not an objective third-party quality it's an inner first person subjective quality he just doesn't see any way that that could emerge from particles that themselves don't have any of those subjective first person qualities themselves but anyway yeah don't get me wrong i i'm absolutely not claiming to know the answer to this right and it's in fact my my favorite question to lose sleep over what it why is it that you can put together a big blob of quarks and electrons and it's going to feel like something to be them yep yeah i think not only is it fascinating but it's like the most important question of our time as we start building ai because meaning and purpose are all they're they're emotions their subjective experiences right if we try to create a good world rather than a bad world where you want to eliminate suffering suffering is a subjective experience right yeah we can't just be talking about oh our goal is to have a universe where the electrons are moving this way rather than that way that's not why you're against torture you're against torture because there's a negative subjective experience there so if we have no clue what it mean what it is that causes subjective experience how can we be sure that if we build very advanced ai systems that we can talk with and interact with and and like spread into our universe and do all sorts of cool stuff how can we be so sure that they're not going to suffer or or that they're just going to be some kind of zombies which are going through the motions and don't experience anything that would be the ultimate zombie apocalypse if if what we maybe one day think of as our descendants or something if they don't experience anything and then the universe just goes back to be dead i'd much rather that david chalmers and and others figure out what quirk blobs are conscious and what aren't then when you get your home helper robot in the future you know to help you through you and tracy through retirement you maybe have a little switch maybe you can put it in unconscious mode when you wanted to take out the trash and do boring stuff and you can how kind so you don't have to feel guilty about that then and turn into consciousness and erase those memories before our consciousness turn back on the first thing you do is understand at least what this is but in all seriousness do you think that there is any fundamental obstacle toward an artificial system having an inner world of conscious experience no i i i think the whole distinction between artificial and not it just means whether we figure out how to build it yet or not a robot is made of exactly the same kind of quirks and electrons that you are right and i know you don't believe that your ability to do string theory or fall in love with tracy is specifically because you're made of carbon atoms as opposed to some other kind of atoms right as far as i know no other collection of atoms has fallen in love with tracy yet so as an experimental question but uh i absolutely agree with you i i too don't see any fundamental obstacle to all of the inner experiences that we have being experienced by a system that happens to be constructed in a different way from how human beings are currently constructed which i think is just a feature of how evolution has gotten us to this point but as we go to the future that need not be the only way that these kinds of common collections of particles are constructed i'm so glad brian that you're not a carbon chauvinist because i do have some colleagues i respect greatly who just take that as an axiom like of course nothing else can be conscious if it's not biologically evolved and i i think that's an assumption that there really isn't very much scientific basis for the other scary uh attitude i often see is that this is all this bs talking about consciousness we shouldn't talk about it but then in that case we should also stop talking about torture and we should stop saying that we're against it you know i've never met anybody who can explain to me what's so bad about torture without invoking the idea of subjective experience yeah and for me as scientists you know no matter how much we'd like to geek out about equations we should never forget our humanity they were ultimately trying to do good things and and all of our notions of of what's good and what's not good hinge on consciousness on subjective experience and how can we possibly say with a straight face that we're trying to make the world better if we refuse to talk about consciousness refuse to talk about what good means yeah no and i fully agree and i think both of us are are pleased and tell me if you feel different but i can't imagine you do with the fact that there was a time when scientists couldn't talk about consciousness in a serious way without being ostracized it was the topic that you only spoke about when you were too old to do real thinking about real science and now it's come to a place where it's respectable to begin to talk about these ideas we all agree that we are in the infancy of understanding consciences but as you say you know coke and chanoni and others are even trying to put mathematical might behind these early ideas of what consciousness might be and i think that's a very positive development for science and for humanity going forward yeah i couldn't agree more and you know there's a lot of historical precedence to this so people you have to be as you know if you are a scientist right then you are very well aware that that the boundary between what's considered science right now and what's not is um not an immutable boundary it keeps shifting right there was a time when when people were pretty serious about ghosts right and now that's considered utterly unscientific and and there are a lot of other things which once upon a time also people thought was maybe scientific and now you sort of just uh smile when you hear about it and then technology and things like that yeah and then there are other things which have gone the other way i actually geeked out on this uh your question of yours to the point that i actually drew a picture of of it as well if i can we can just put this super briefly on the yeah on the screen here let's see do you see my um i do i think i see it i don't know if the audience is seeing it i assume are yep they are yeah so you know witchcraft and ghosts and psychokinesis and telepathy and so on they have left uh mainstream science and other things came in instead like you know einstein was very dissed when he came up with a relativity theory some of the nazis in charge said this was jewish physics and bad stuff dark matter was considered very flaky black holes were considered very speculative and now they're considered mainstream science parallel universes right now is just kind of on the verge there yeah plate tectonics used to be this right and in math there were also things which used to be considered very irrespective but even people who started talking about irrational numbers or imaginary numbers were often criticized at the time and now can you imagine walking into calculus class at columbia and claiming that it's not science to talk about complex numbers i mean things change and consciousness i think is exactly one of those questions one of those topics which is coming in is just in the process of coming in to the mainstream of science yep and welcome i totally agree so max it's been a it's been a fascinating conversation thanks thanks for joining us and let me just end by encouraging everyone who's watching to number one check out max's book or any of max's books but we've been focusing on ideas that he developed in our mathematical universe but he has a wonderful book on the future of life and and and intelligent thought which is called uh life 3.0 is that the correct title great so you should check those out and also you should look at the program of the world science festival that we posted two weeks ago max was part of that conversation as was david albert shelly goldstein and sylvia jonas on a more broad conversation about does math reveal reality you can find that on the world science festival website and finally i'll just uh encourage you to keep your eyes out for the next program which will be in about two weeks a program on language i mentioned this at the outset with noam chomsky stephen pinker evelyn federenko and daniel dorr and again if any of you have the killer title for that program on language and thought send it to us we'd be uh happy to use it happy to credit you we haven't really come up with the right title yet and then uh in steady state we hope to have these conversations and those more produced formal programs in our virtual theater on average every week but we're starting every other week as we gear up our production in this unfortunately persisting coveted world maybe next june we'll have a live world science festival in new york there will be i think a live world science festival they're claiming in brisbane australia for those of you in that part of the world in march unfortunately i won't be able to go nobody from here will australia apparently is not going to open its borders until post that date but we will stay in touch with you through these online programs and our virtual conversations in our virtual theater as those will be coming on a regular basis all right that's all from us here again thank you max for joining us and guys uh in in two weeks with our program on language okay thank you thank you to the awesome viewer questions from around the world as far as poland and thank you brian for this absolutely fascinating conversation i really enjoyed it my pleasure thank you for joining us okay folks signing off here from world science festival headquarters in new york city

Channel: World Science Festival

Views: 85,877

Rating: 4.898787 out of 5

Keywords: Brian Greene, Nikola Tesla, Does Math Reveal Reality?, Mathematical Universe, Mathematical mysteries, math, mathematics, Quantum Physics, search of answers, prime numbers, nature of infinity, geometry of hyperspace, mathematical truths, infinity, boundaries of math, masterminds, 2021, breakthroughs, Hypothesis, David Z. Albert, Sheldon Goldstein, Silvia Jonas, Max Tegmark, Orman Quine, David Chalmers, Kurt Godel, Hartry Field, Richard Feynman, History of Math

Id: Gu28y7vZmrI

Length: 96min 57sec (5817 seconds)

Published: Thu Sep 02 2021