Wolfram's Theory of Everything Explained | Stephen Wolfram and Lex Fridman

maybe we should begin even before that at the very base layer of the wolfram physics project maybe you can give a broad overview once again really quick about this hypograph model yes and also what is it a year and a half ago since you've brought this project to the world what is the status update where what are all the beautiful ideas you have come across what are the interesting things you can always mention it's i mean it's a it's a freaking cambrian explosion i mean it's it's crazy i mean there are all these things which i've kind of wondered about for years and suddenly there's actually a way to think about them and i really did not see i mean the real strength of what's happened i absolutely did not see coming and the real strength of it is we've got this model for physics but it turns out it's a foundational kind of model that's a different kind of computation computation-like model that i'm kind of calling the sort of multi-computational model and that that kind of model is applicable not only to physics but also to lots of other kinds of things and one reason that's extremely powerful is because physics has been very successful so we know a lot based on what we figured out in physics and if we know that the same model governs physics and governs i don't know economics linguistics immunology whatever we know that the same kind of model governs those things we can start using things that we've successfully discovered in physics and applying those intuitions in all these other areas and that's that's pretty exciting and and and very surprising to me um and in fact it's kind of like in the original story of sort of you go and you explain why is there complexity in the natural world then you realize well there's all this complexity there's all this computational irreducibility you know there's a lot we can't know about what's going to happen it's kind of it's kind of very confusing thing for people who say you know science has nailed everything down we're going to you know based on science we can know everything well actually there's this computational irreducibility thing right in the middle of that thrown up by science so to speak and then the question is well given computational irreducibility how can we actually figure out anything about what happens in the world why aren't we why are we able to predict anything why are we able to operate in the world and the answer is that we sort of live in these slices of computational reusability that exists in this kind of ocean of computational irreducibility and it turns out that seems that it's a very fundamental feature of the kind of model that seems to operate in physics and perhaps in a lot of these other areas that there are these particular slices of computational reducibility that are relevant to us and those are the things that both allow us to operate in the world and not just have everything be completely unpredictable but there are also things that potentially give us what amount to sort of physics-like laws in all these other areas so that's that's been sort of an exciting thing but but i would say that in general for our project it's been going spectacularly well i mean i you know i it's very honestly it wasn't something i expected to happen in my lifetime i mean it's you know it's something where where it's it's and in fact one of the things about it some of the things that we've discovered are things where i was pretty sure that wasn't how things worked and turns out i'm wrong and you know in a major area in meta mathematics i i'd be realizing that something i've long believed we can talk about it later that that that uh just just really isn't right but but i think that um the um the thing that uh so so what's happened with the physics project i mean you know it's a it can explain a little bit about how the how the model works but basically we can maybe ask you uh the following question so it's easy through words describe how cellular automata works you've explained this and it's the fundamental mechanism by which you in your book and your kind of science explored the idea of complexity and how to do science in this world of eye reducible islands and irreducible general irreducibility okay so how does the model of hypergraphs differ from cellular and how does the idea of multi-computation differ like maybe that's a way to describe it right we're yeah right this is a you know my life is like all of our lives something of a story of computational irreducibility yes and you know it's been going for a few years now so it's always a challenge to kind of find these appropriate pockets of reducibility but let me see what i can do great so so i mean first of all let's let's talk about physics first of all and you know a key observation that one of the starting point of our physics project is things about what is space what is the universe made of and you know ever since euclid people just sort of say space is just this thing where you can put things at any position you want and they're just points and they're just geometrical things that you can just arbitrarily put at different different coordinate positions so the first thing in our physics project is the idea that space is made of something just like water is made of molecules space is made of kind of atoms of space and the only thing we can say about these atoms of space is they have some identity there's a there's a there is it's this atom as opposed to this atom and you know you could give them if you're a computer person you give them uuids or something yes and and um but that's all there is to say about them so to speak um and then all we know about these atoms of space is how they relate to each other so we say these three atoms of space are associated with each other in some relation so you can think about that as you know what atom of space is friends with what other atom of space you can build this essentially friend network of the atoms of space and the sort of starting point of our physics project is that's what our universe is it's a giant friend network of the atoms of space and so how can that possibly represent our universe well it's like in something like water you know they're molecules bouncing around but on a large scale that you know that produces fluid flow and we have fluid vortices and we have all of these phenomena that are sort of the emergent phenomena from that underlying uh kind of collection of molecules bouncing around and by the way it's important that that collection of molecules bouncing around have this phenomenon of computational irreducibility that's actually what leads to the second law of thermodynamics among other things and that leads to the sort of randomness of the underlying behavior which is what gives you something which on a large scale seems like it's a smooth continuous uh type of thing and so so okay so first thing is space is made of something it's made of all these atoms of space connected together in this network and then everything that we experience is sort of features of the of that structure of space so you know when we have an electron or something or a photon it's some kind of tangle in the structure of space much like kind of a vortex and a fluid would be just this thing that is you know it it can actually the vortex can move around it can involve different molecules in the fluid but the vortex still stays there and if you zoom out enough the vortex looks like an atom itself like a basic element yes so there's the levels of abstraction if you squint and kind of blur things out it looks like at every level of abstraction you can define what is a basic individual entity yes but but you know in in this model there's a bottom level yeah you know there's an elementary length maybe that's 10 minus 100 10 to the minus 100 meters let's say which is really small you know proton is 10 to the minus 15 meters the smallest we've ever been able to sort of see where the particle accelerator is around 10 to the minus 21 meters so you know if we don't know precisely what the correct scale is but it's perhaps of the order of 10 to the minus 100 meters so it's pretty small um and but but that's that's the end that's that's what things are made of what's your intuition where the 10 to the minus 100 comes from what's your intuition about this scale well okay so there's a calculation which i consider to be somewhat rickety okay which has to do with comparing so so there are various fundamental constants there's a speed of light the speed of light once you know the elementary time the speed of light is tells you the conversion from the elementary time to the elementary length then there's the question of how do you convert to the elementary energy and how do you convert to between other things and the various constants we know we know the speed of light we know the gravitational constant um we know planck's constant and quantum mechanics those are the three important ones and we actually know some other things we know things like the size of the universe the hubble constant things like that and essentially this calculation of the elementary length comes from looking at these sort of combination of those okay so the most obvious thing people have sort of assumed that quantum gravity happens at this thing the planck scale 10 minus 34 meters which is the sort of the the combination of of planck's constant and the gravitational constant the speed of light that gives you that kind of length turns out in our model there is an additional parameter which is essentially the number of simultaneous threads of execution of the universe which is essentially the number of sort of independent quantum uh processes that are going on and that number let's see if i remember that number that number is 10 to 170 i think and and so it's a big number but um that number then connects you know sort of modifies what you might think from all these planck uh units to give you the things we're giving and there's been sort of a mystery actually in the in the more technical physics thing that the plank mass the plank energy plank energy is actually surprisingly big the plank length is tiny 10 minus 34 meters that you know planck time 10 minus 43 meters i think seconds i think um but the planck energy is like uh is like the the energy of a of a lightning strike okay which is pretty weird in our models the actual elementary energy is that divided by the number of sort of simultaneous quantum threads and it ends up being really small too and that sort of explains that mystery that's been around for a while about about how planck units work but but that you know whether that precise estimate is right we don't know yet i mean that that that's one of the things that's sort of been a thing we've been pretty interested in is how do you see through you know how does you how do you make a gravitational microscope that can kind of see through to the atoms of space you know how do you get in in fluid flow for example if you go to hypersonic flow or something you know you've got a mark 20 you know space plane or something it really matters that there are individual molecules hitting the space plane not a continuous fluid the question is what is the analogous kind of what is the analog of hypersonic flow for for our for things about the structure of spacetime and it looks like uh a a rapidly rotating black hole right at the sort of critical rotation rate um is it looks as if that's a case where essentially the the structure of space time is just about to fall apart and you may be able to kind of see the evidence of sort of discrete uh elements you know you may be able to kind of see there the sort of gravitational microscope of actually seeing these discrete elements of space and there may be some effect in for example gravitational waves produced by rapidly rotating black hole that in which one could actually see some phenomenon where one can say yes they don't come out the way one would expect based on having a continuous structure of space time that it is something where you can kind of see through to the discrete structure um we don't know that yet so you can maybe elaborate a little bit deeper how a microscope they can see to 10 to the minus 100 how rotating black holes and uh presumably the the the detailed accurate detection of gravitational waves from since black holes can reveal the discreteness of space okay first thing is what is a black hole actually we we need to go a little bit further in the story of what space time is because i explained a little bit about what space is but it didn't talk about what time is and that's sort of important in in understanding space time so to speak and your sense is both space and time in this story are discrete absolutely absolutely but it's a complicated story yes and um needless to say well it's simple at the bottom it's it's very simple at the bottom it's it's very in the end it's simple but deeply abstract and um and something that is simple in conception but kind of wrapping one's head around what's going on is pretty hard um but so so first of all we have this so you know i've described these kind of atoms of space and their connections you can think about these things as a hyper graph you know a graph is just you connect nodes to nodes but a hypergraph you can have you know you can have sort of not just friends individual friends to friends but you can have these triplets of of friends or whatever else it's it's um and so we're just saying and that's just the relations between atoms of space are the hyper edges of the hypograph and so we've got some big collection of of these atoms of space maybe 10 to the 400 or something in our in our universe um and that's the structure of space that's and every feature of what we experience in the world is a feature of that that hypograph that spatial hypograph so then the question is well how does what does that spatial hypograph do well the idea is that there are rules that update that spatial hypograph and you know in a cellular automaton you've just got this line of cells and you just say it every step at every time step you've got fixed time steps fixed array of cells at every step uh every cell gets updated according to a certain rule and that's um that's kind of the that's the way it works now in this hypergraph it's sort of vaguely the same kind of thing we say every time you see a little piece of hypergraph that looks like this update it to one that looks like this so it's just keep rewriting this hypograph every time you see something looks like that anywhere in the universe it gets rewritten now one thing that's tricky about that which we'll come to is this multi-computational idea which has to do with you're not saying in in some kind of lock step way do this one then this one then this one it's just whenever you see one you can do you can go ahead and do it and that leads one not to have a single thread of time in the universe because if you knew which one to do you just say okay we do this one then we do this one then we do this one but if you say just do whichever one you feel like you end up with these multiple threads of time these kind of multiple histories of the universe depending on which order you happen to do the things you could do in so it's fundamentally asynchronous and parallel yes yes which is very uncomfortable for the human brain that seeks for things to be sequential and synchronous right well i think that this is this is part of the story of consciousness is i think the key aspect of consciousness that is important for sort of parsing the universe is this point that we have a single thread of experience right we have a memory of what happened in the past we can say something predict something about the future but there's a single thread of experience and it's not obvious it should work that way i mean we've got 100 billion neurons in our brains and they're all firing in all kinds of different ways but yet our experiences that there is the single thread of of of time that that goes that that goes along and i think that you know one of the things i've kind of realized with a lot more clarity in the last year is the fact that our the fact that we conclude that the universe has the laws it has is a consequence of the fact that we have consciousness the way we have consciousness and so the fact so i mean just to go on with kind of the the basic setup it's uh so we've got this spatial hypograph it's got all these atoms of space they're getting they're getting these little clumps of atoms of space are getting turned into other clumps of atoms of space and that's happening everywhere in the universe all the time and so one thing is a little bit weird is there's nothing permanent in the universe the universe is getting rewritten everywhere all the time and if it wasn't getting rewritten it would space wouldn't be knitted together that is space would just fall apart there wouldn't be any way in which we could say this part of space is next to this part of space you know one of the things that i was people were confused about back in antiquity you know the ancient greek philosophers and so on and how does motion work you know how can it be the case that you can take a thing that we can walk around and it's still us when we walked you know a foot forward so to speak and in a sense with our models that's again a question because it's a different set of atoms of space when we you know when i move my hand it's it's moving into a different set of atoms of space it's having to be recreated it's not the thing itself is not there it's it's being continuously recreated all the time now it's a little bit like waves in an ocean you know vortices and fluid which again the actual molecules that exist in those are not what define the identity of the thing and but it's a little bit uh you know this idea that there can be pure motion that it can that it is even possible for an object to just move around in the universe and not change is it's not self-evident that such a thing should be possible and that is part of our perception of the universe is that we we parse those aspects of the universe where things like pure motion are possible now pure motion even in general relativity the theory of gravity um pure motion is a little bit of a complicated thing i mean if you imagine your average you know teacup or something approaching a black hole it is deformed and distorted by the structure of space time and to say you know is it really pure motion is it that same teacup that's the same shape well it's a bit of a complicated story and this is a a more extreme version of that so so anyway the the the thing that that's happening is we've got space we've got this notion of time so time is this kind of this rewriting of the hypograph and one of the things that's important about that time is this sort of computationally irreducible process there's something you know time is not something where in kind of the mathematical view of of time tends to be time is just to coordinate we can you know slide a slider turn a knob and we'll change the the time that we've got in this equation but in this picture of time that's not how it works at all time is this inexorable irreducible kind of set of computations that go on that go from where we are now to the future but so so the thing and one of the things that is again something one sort of has to break out of is your average trained physicist like me says you know space and time are the same kind of thing they're related by you know the prank array group and and lawrence transformations and relativity and all these kinds of things and you know space and time you know there are all these kind of sort of folk stories you can tell about why space and time is the same kind of thing in this model they're fundamentally not the same kind of thing space is this kind of sort of connections between these atoms of space time is this computational process so the thing that the first sort of surprising thing is well it turns out you get relativity anyway and the reason that happens the few bits and pieces here which one has to understand but but the the fundamental point is if you are an observer embedded in the system that are part of this whole story of things getting updated in this way and that there are there's sort of a limit to what you can tell about what's going on and really in the end the only thing you can tell is what are the causal relationships between events so an event in this sort of an elementary event is a little piece of hypograph got rewritten and that means a few hyper edges of the hypergraph were consumed by the event and you produce some other hyperedges and that's an elementary event and so then the question is uh what we can tell is kind of what the network of causal relationships between elementary events is that's the ultimate thing the causal graph of the universe and it it turns out that well there's this property of causal invariance that is true of a bunch of these models and i think is inevitably true for a variety of reasons um that makes it be the case that it doesn't matter kind of if if you are sort of saying well i've got this hypograph and i can rewrite this piece here and this piece here and i do them all in different orders when you construct the causal graph for each of those orders that you choose to do things in you'll end up with the same causal graph and so that's essentially why uh well that's in the end why relativity works it's why our perception of space and time is is as having this kind of connection that relativity says they should have and that's that's kind of that's kind of how that works i think i'm missing a little piece uh if you can go there again you said uh the the fact that the observer is embedded in this hypergraph what's missing uh what is the observer not able to state about this universe so basically if you look from the outside you can say oh i see this uh i see this particular place was updated and then this one was updated and and i'm seeing which order things were updated in but the observer embedded in the universe doesn't know which order things were updated in because until they've been updated they have no idea what else happened so the only thing they know is the set of causal relationships let me give an extreme example let's imagine that the universe is a turing machine turing machines have just this one update head which does something and otherwise the turing machine just does nothing right and and the turing machine works by having this head move around and do its updating uh you know just where the head happens to be the question is could the universe be a turing machine could the universe just have a single updating head that's just zipping around all over the place you say that's crazy because you know i'm i'm talking to you you seem to be updating i'm updating etc but the thing is there's no way to know that because if there was just this head moving around it's like okay it updates me but you're completely frozen at that point until the head has come over and updated you you have no idea what happened to me and so if you sort of unravel that argument you realize the only thing we actually can tell is what the network of causal relationships between the things that happened were we don't get to know from some sort of outside sort of god's eye view of the thing we don't get to know what sort of from the outside what happened we only get to know sort of what the set of relationships between the things that happened actually work yeah but if i somehow record like a trace of this i guess would be called multi-computation can't i uh then look back in the way some you place throughout the universe like throughout like a log that records in my own pocket of in this hyper graph can die like realizing that i'm getting an outdated picture can't i record see the problem is and this is where things start getting very entangled in terms of what one understands the problem is that any such recording device is itself part of the universe yeah so you don't get to say you never get to say let's go outside the universe and go do this and and that's why i mean lots of the features of this of this model and the way things work end up being a result of that so but what i guess from on a human level what is the cost you're paying what are you missing from not getting an updated picture all the time okay i got i i understand what you should say yeah yeah right but like what like how does consciousness emerge from that like how like wha what are the limitations to that observer i understand you're getting uh a delay well that's true there's a okay so there's there's a bunch of limitations of the observer i think maybe just explain something about quantum mechanics because that maybe is a is an extreme version of some of these issues which helps to kind of motivate why one should sort of think things through a little bit more carefully so one feature of the of this okay so in standard physics like high school physics you learn you know the equations of motion for a ball and the the you know it says you throw the ball this angle this velocity things will move in this way and there's a definite answer right the story the the key story of quantum mechanics is there aren't definite answers to where does the ball go there's kind of this whole sort of bundle of possible paths and all we say we know from quantum mechanics is certain probabilities for where the ball will end up okay so that's kind of the the core idea of quantum mechanics so in our models you quantum mechanics is not some kind of plug-in add-on type thing you absolutely cannot get away from quantum mechanics because as you think about updating this hyper graph there isn't just one sequence of things one definite sequence of things that can happen there are all these different possible update sequences that can occur you could do this you know piece of the hypograph now and then this one later and etc etc etc all those different paths of history correspond to these quantum quantum paths and quantum mechanics these different possible quantum histories and one of the things that's kind of surprising about it is they they branch you know there can be a certain state of the universe and it could do this or it could do that but they can also merge there can be two states of the universe which their next state the next state they produce is the same for both of them and that process of branching and merging is kind of critical and the idea that they can be merging is critical and somewhat non-trivial for these hypographs because there's a whole graph isomorphism story and there's a whole very elaborate settlement that's where the causal invariance comes in yes among other things right okay yes that that's but but so so then what happens is that what what one's seeing okay so we've got this thing it's branching it's merging et cetera et cetera et cetera okay so now the question is how do we perceive that what you know how do we do we why don't we notice that the universe is branching and merging why you know why is it the case that we just think a definite set of things happen well the answer is we are embedded in that universe and our brains are branching and merging too and so what quantum mechanics becomes a story of is how does a branching brain perceive a branching universe and the key thing is as soon as you say i think definite things happen in the universe that means you are essentially conflating lots of different parts of history you're saying actually as far as i'm concerned because i'm convinced that definite things happen in the universe all these parts of history must be equivalent now it's not obvious that that would be a consistent thing to do it might be you say all these parts of history are equivalent but by golly moments later that would be a completely inconsistent point of view everything would have you know gone to hell in different ways the fact that that doesn't happen is well that's a consequence of this causal and variance thing but that's and the fact that that does happen a little bit is what causes little quantum effects and that um if that didn't happen at all there wouldn't be anything that sort of is like quantum mechanics it would be uh quantum mechanics is kind of like in this uh in this kind of this bundle of paths it's a little bit like what happens in statistical mechanics and fluid mechanics whatever that most of the time you just see this continuous fluid you just see the world just progressing in this kind of way that's like this continuous fluid but every so often if you look at the exact right experiment you can start seeing well actually it's made of these molecules where they might go that way or they might go this way and that's kind of quantum effects and and so that's so the this kind of idea of where we're sort of embedded in the universe this branching brain is perceiving this branching universe and that ends up being sort of a story of quantum mechanics that's that's part of the the whole picture of what's going on but i think i mean to come back to sort of where does conscious what is what is the story of consciousness so in the universe we've got you know whatever it is 10 to the 400 atoms of space they're all doing these complicated things it's all a big complicated irreducible computation the question is what do we perceive from all of that and the answer is that we are we are parsing the universe in a particular way let me again go back to the the gas molecules analogy you know in the gas in this room there are molecules bouncing around all kinds of complicated patterns but we don't care all we notice is there's you know the gas laws are satisfied maybe there's some fluid dynamics these are kind of features of that assembly molecules that we notice and then lots of details we don't notice when you say we do you mean the tools of physics or do you mean literally are the human brain in this perception system well okay so the human brain is where it starts but we built a bunch of instruments to do a bit better than the human brain but they still have many of the same kinds of ideas you know their cameras and their pressure sensors and their these kinds of things they're not uh you know at this point we don't know how to make fundamentally qualitatively different sensory devices right and so it's always just an extension of the conscious ex experience or a sensory experience sensory experience but sensory experience that's somehow intricately tied to consciousness right well so so one question is when we are looking at all these molecules in the gas and there might be 10 to 20 molecules in some little little box or something it's like what what do we notice about those molecules so one thing that we can say is we don't notice that much we are you know we are computationally bounded observers we can't go in and say okay i'm they're 10 to 20 molecules and i know that i can sort of decrypt their motions and i can figure out this and that it's like i'm just going to say what's the average density of molecules and so one key feature of us is that we are computationally bounded and that when you are looking at a universe which is full of computation and doing huge amounts of computation but we are computationally bounded there's only certain things about that universe that we're going to be sensitive to we're not going to be you know figuring out what all the atoms of space are doing because we're just computationally bounded observers and we are only sampling these these small set of features so i i think the two defining features of consciousness that and i you know i would say that the the sort of the the preamble to this is for years you know because i've talked about sort of computation and fundamental features of physics and science people ask me so what about consciousness and i for years i've said i have nothing to say about consciousness and you know i've kind of told this story you know you talk about intelligence you talk about life these are both features where you say what's the abstract definition of life we don't really know the abstract definition we know the one for life on earth it's got rna it's got cell membranes it's got all this kind of stuff similarly for intelligence we know the human definition of intelligence but what is intelligence abstractly we don't really know and so what i've long believed is that sort of the abstract definition of intelligence is just computational sophistication that is that as soon as you can be computationally sophisticated that's kind of the abstract version the generalized version of intelligence so then the question is what about consciousness and what i sort of realized is that consciousness is actually a step down from intelligence that is that you might think oh you know consciousness is the is the is the top of the pile but actually i don't think it is i think that there's this notion of kind of computational sophistication which is the generalized intelligence but consciousness has two limitations i think one of them is computational boundedness that is that we're only perceiving a sort of computationally bounded view of the universe and the other is this idea of a single thread of time that is that we and in fact we know neurophysiologically our brains go to some trouble to give us this one thread of attention so to speak and it isn't the case that you know in all the neurons in our brains that that uh in at least in our conscious know the the you know the correspondence of language in our conscious experience we just have the single thread of attention single thread of of perception um and you know maybe there's something unconscious that's bubbling around that's the kind of almost the quantum version of what's happening in our brain so to speak we've got the the classical flow of what we are mostly thinking about so to speak but there's this kind of bubbling around of other paths that is all those other neurons that didn't make it to be part of our sort of conscious stream of experience you

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Id: o8Cu0_A_rfg

Length: 33min 44sec (2024 seconds)

Published: Wed Oct 27 2021