A Quantum Beginning for a Two-Sided Universe with Dr. Neil Turok

how did it all begin out of this universe in which we live come to be the story begins in the early 20th century with George Lemaitre who originated the concept that an expanding universe could be extrapolated back to a point then came the observations of that new Hubble that indicated rather clearly that the universe was indeed expanding then there were other discoveries such as the cosmic microwave background radiation which is literally the afterglow of the Big Bang but there are mysteries still there comes a point where we can no longer study the Big Bang directly a point where everything becomes opaque this and other questions have led to a number of different models for just how the Big Bang played out my guest today specializes in the physics of the early universe and unraveling just what happened you have fallen into event horizon with John Michael Gautier [Music] [Applause] in today's episode John is joined by dr. Neil Turok dr. Chirac was a professor of physics at Princeton University and chair of mathematical physics at the University of Cambridge he was the director of the perimeter Institute in Ontario his research focuses on developing fundamental series of cosmology and new observational tests with Stephen Hawking he discovered in Stanton solutions describing the birth of inflationary universes with Paul Steinhardt he developed an alternative cyclic model for cosmology whose predictions are so far in agreement with all observational tests jarick was awarded the James Clerk Maxwell medal of the Institute of Physics in 2003 he founded the African Institute for mathematical sciences in Cape Town for his scientific discoveries and his work developing aims Turek was awarded a TED Prize in 2008 dr. Neil Turok welcome to the program thank you now doctor you work with the very earliest beginnings of the universe the Big Bang and there's a brick wall yeah there's a brick wall with a big bang where we can only see I believe it's what about three hundred thousand years or something like that and that we can see and then it becomes opaque how do you get past that how do you get past that wall in physics of what you can't observe right so we can see back about 13.7 billion years but then as you say before that there's about four hundred thousand years between the Big Bang itself and the era where the universe becomes transparent so there's this opaque boundary about four hundred thousand light years thickness which surrounds us and as you say it's like a brick wall we we find it hard to see it see-through it with light the problem is the early universe is so dense and full of charged particle that it makes it very it obscures what happened you know at the very beginning however there are ways through it and one of the observational ways to see the beginning of the universe is to use gravitational waves which have only recently been detected by laboratories here on earth and these gravitational waves are are not scattered by the dense material of the early universe so if we're able to measure gravitational waves that they basically give us a way of looking right back to the beginning of the universe itself and so the science is early the sensitivity of currents detectors of gravitational waves is insufficient for us to really see what happened but it's a very very promising direction and for theorists like myself who make theoretical models of what actually happened at the Big Bang it's very encouraging to know that in 10 20 or 30 years we will be able to test these ideas in in experiments and observations now as a theorist what do you think actually happen I've worked on a number of different possibilities I have a fairly open mind what I want to know is the truth and so the whole point of doing science is to discover that and and and not to you know go on the basis of prejudice or preconception so I am most interested in theories which can be proven wrong because those are testable theories and you learn even if you prove your idea wrong long wrong you learn something in the process so I think there are a number of possibilities there's a very popular paradigm called theory of inflation which has really dominated the field of cosmology for the last three decades but I find it rather unconvincing myself based on a lot of additional ingredients which is sort of added by hand to the basic Big Bang picture and it doesn't really answer definitively what happened at the beginning is kind of a theory of what happened just after the beginning and what is postulated is the process of kind of growth and smoothing of the universe to make it into something like what we see but for me the explanation is a little bit too ad-hoc and it's not beautiful enough quite frankly I think there is nothing in nature more beautiful than the universe it's astonishingly simple on large scales I mean so what I like to say is the universe is the simplest thing we know of in the universe what sounds paradoxical but it is indeed amazing but as you go to larger and larger scales in the universe what you see is increasing simplicity so that for me demands a very simple hypothesis as to how it began and so that's what I've been exploring much simpler ideas than inflation which seek to explain the very beginning now how does that work the universe at its very biggest scales is simple and elegant yes as you were describing yeah and then on on other scales though smaller scales it gets increasingly messy why is that right that's the basic puzzle you might have expected that as we began to probe the universe at larger and larger scales what we discover would be more and more complexity right so you think of the universe is built out of LEGO building blocks maybe atoms and elementary particles which are reasonably simple objects and as you combine them you get of course many complicated structures you get molecules you care cells which are the basis for life you get living organisms you know so complexity certainly does grow as you go to large scales the puzzle is that is you go to really large scales that complexity seems to disappear again and so the universe on the very largest scale almost looks as simple as a elementary particle now what do I mean by that I mean that if you look in different directions on the sky the universe is very very similar in all these directions to about one part in a hundred thousand the density of the universe is the same in all directions on the sky and so it's remarkably uniform and and even the non-uniformities the fact it's not quite the same in each direction those non-uniformities take a very simple statistical form they look like random ripples with a very small amplitude and a very simple spectrum meaning that the ripples of different sizes have almost the same strength and then they are randomly superposed so it's like a pattern of waves you would see on the surface of the sea except when you analyze this pattern the in in the the most possible detail we can we find that it's the mud it's the simplest kind of pattern you could get superposition of waves almost the same strength or amplitude on all scales across all scales so the large scale universe is very much simpler even than a complicated molecule like DNA you know to describe a molecule like DNA you would need quite a few numbers whereas the large Gill universe requires approximately four numbers to describe one is the strength of these ripples which I've described the second is the relative abundance of particles of the type we are made of called baryons these are neutrons and protons and stuff which atomic nucleus made of and then the relative abundance of those nuclear particles to particles of light or photons that's one number then you have dark matter for which we have a new explanation based on this simple Big Bang hypothesis which I mentioned and thirdly this dark energy which is a kind of energy that fills all of space in the universe and it's absolutely uniform in space and in time just a constant so these four numbers describing the different forms of energy in the universe that light the nuclear matter the dark matter the dark energy and then the fluctuations the structure in the universe those four numbers are all you need so the universe is really incredibly simple on large scales and I do believe that simple phenomena you know written quire elegant solutions elegant theory which explains the simplicity and so these observations which have really been made only in the last few decades are incredibly encouraging to sort of crazy people like me who are looking for an answer we were looking for a theoretical framework which ties this all together in an absolutely compelling way that will convince everyone that sort of once again elegance if you come up with an elegant simple solution that works then you're there or at least closely there yeah now dark matter you mentioned that that in your and you're thinking there's an explanation for it what is it well okay so as I keep mentioning the last ten years the focus of my research is to look for simple explanations and by simple I mean elegant minimal mathematically rigorous but with as few assumptions as possible and able to fit the observations so our picture of the Big Bang maybe let me step back a little bit how can you explain in the coming into being of the whole universe you know that that almost sounds impossible because the laws of physics described how the universe evolves in time and when you say the universe came into being there wasn't he wasn't anytime before it came into being so you know you're almost immediately at a contradiction the theory we have proposed is based on an analogy because often nature uses the same principles again and again and this especially true in physics so rather than thinking about the universe let's think about the coming into being of a part you know is it possible for an elementary particle like an electron to come into being when there was no particle before and the answer is yes it is possible and it happens all the time in the laboratory what what you see in experiments is the creation of particle-antiparticle pairs so for example if I turn on a very strong electric field if I do have a charged particle the charged particle will be accelerated by the field and fly off you know at increasing speed in some direction in the direction of the field now imagine you had no particle and you turned on a strong electric field what happens is the field literally drags a particle out of the vacuum and so the particle goes one way along the field but it also drags an antiparticle out of the vacuum and the antiparticle has the opposite electric charge and travels in the opposite direction so this is a well-established process that electric fields can create particle-antiparticle pairs out of the vacuum out of nothing so our theory was really built on the idea well maybe that's what happened at the beginning of the universe maybe it's possible to in effect drag a universe out of nothing and I'll talk about what does the dragging later you know the electric field called particles of the vacuum in our case it's it's really the dark energy which which does that but the implication of this model is that there would be two sides of the universe one side if you like full of matter ordinary matter and the other side full of antimatter just as in the particle antiparticle pair so we began to explore this hypothesis - we have to check many things that it's consistent with what we know about gravity about particle physics and we found it works remarkably simply and has certain features which other scenarios like this inflation scenario don't have and then one of the surprising consequences of this picture is it gave us the simplest yet explanation for the dark matter so the dark matter you know if you if you look at what we know about physics today we know about various types of particles and and how they couple to forces and and through the forces to each other now we already know that there's a particular kind of particle called a new tree which couples very weakly to other forms of matter so for example a neutrino and travel straight through the earth without colliding with any particle in the earth because it interacts so weakly with the other matter for this reason it's called a ghost particle you know it really and these things are produced in laboratories with enough effort but you can detect them and so this is you know well-established physics one based on the properties of the neutrinos we nut we can infer that which are called left-handed particles and the reason is if you hold out your left hand and point the thumb in some particular direction then the other four fingers you know turn around the thumb in a in in a certain rotation and we say left-handed is because when the particle travels in the directional on your thumb it is spinning in the direction signified by your coughing and fingers so there are left-handed neutrinos will actually see all the time in laboratories but we also infer from these experiments that there are right-handed neutrinos okay and the right-handed neutrinos are all ghostly because they literally don't couple to anything any forces apart from gravity the only thing they couple to is is gravity and and actually something called the Higgs boson which which is a you know very very weak force indeed so the these particles were sort of inferred from all experiments people doing high-energy physics labs what we realized is that one of the right-handed neutrinos which we are almost mmm does exist was the perfect candidate for the dark matter in the universe now before us people hadn't been able to calculate how much of this particular right-handed neutrino would be in the universe because it's so weakly coupled it isn't easily created by other particles so it turns out this this very odd right-handed neutrino which we are former sure exists from multiple experiments we could with our picture of the universe sort of being pulled out of nothing this universe and the universe pair we could actually calculate how many of these strange right-handed neutrinos were present just filling the universe and when we work through the numbers we found a number which allowed the the theory to match the the dark matter which we see perfectly so this is really the most economical explanation yet for the dark matter because as soot once you explain the big bag and if you assume the known physics physics we already know from laboratories then this right-hander neutrino turns out to be an excellent candidate to explain the dark matter we don't even need anymore ingredients in the physics we already know now one of the vexing problems those is that dark matter is is all we know about it is from its gravitational influence so these neutrinos he's right-handed neutrinos yeah are responsible for that excess gravity right that's right that's right so it's a very economical explanation but you're right we need further predictions to verify the theory right and if you can't see the stuff all you see it's it's gravity you know how do you what's the next step to verify that your explanation is correct so we have a prediction in fact there are several predictions but one of the most interesting is that if one of the right-handed neutrinos is stable and forms a dark matter it follows from standard physics which we didn't invent we merely interpret it follows from standard physics that one of the left-handed neutrinos is exactly massless it cannot have any mass at all and this is something which current experiments have are checking so the left-handed neutrinos have very tiny masses and so far he is known that that those masses are very small but it is not known exactly what they are all it's measured is the differences of masses the absolute values of the masses are not measured but they will be over the next decades so actually it's amazing the way you measure neutrino masses the most accurate way now is to use the cosmos because these neutrinos are present throughout the cosmos and the way they clump under gravity depends on what their mass is you see if they're very light then they're essentially zipping around at the speed of light if they're massless they have to go at speed of light and that means they don't clump very efficiently so our measurements of the cosmos are now so accurate that we can actually see this effect but the neutrinos are knocked up they would if they had a mass so it turns out that over the next 10 years galaxy surveys and measurements of the radiation of the from the Big Bang we'll be able to test if one of the neutrinos is very nearly massless and if it is that will confirm the basic prediction of us now but there's another prediction which was in a way even more exciting which is so so we wrote this paper saying you know the right-handed neutrino can be the dark matter and this is it's math if it is the dark matter this is its mass we can predict the mass of the particle exactly and it was let me see 400 million times the mass of the proton so 480 million times the mass the probe we just we wrote the paper that was the prediction so it turned out unknown to us they were experimentalist in the Antarctic who were looking for signals of decaying particles and as these particles are very heavy decaying particles they would emit very high-energy particles which would give rise to showers of charged particles in the atmosphere and they designed a very beautiful and clever balloon borne telescope to see the signal of those showers unknown to us they had detected two events at exactly 480 million times the mass of the proton which they could not explain okay and so they immediately you know contacted us and said why we've seen two particles decaying like that now there's a contradiction because I told you already we need these particles to be stable to explain the Dark Matter meaning they have to have lasted at least the lifetime of the universe obviously this experiment is seeing the byproducts of the decay of a particle with the same mass so what happened so it is conceivable that these particles are very stable but not absolutely stable and so they would decay at some slow rate and they could have explained the events in the Antarctic so we're still thinking about that at the moment it seems difficult to reconcile our first hypothesis with their experiment because we predicted they wouldn't decay they're seeing the decays they've only seen two of them in about four years so they're not decaying very quickly but that's a very tantalizing clue and if it turns out we're able to explain those events and of course if they measure more of those events we would actually have real convincing completely compelling theory of the dark matter and we would be seeing the decay products of the dark matter so all of this is up in the air it's all frontier science but very exciting you know and it may be verified or it may all go away and we'll have to see now this idea of of a weakly interacting particle yes and the idea the idea I mean this goes back to you wimps and things like that yeah yeah now that interaction yes would suggest that it's weekly weekly or almost not interacting with the Higgs field right to get back to the higgs boson yes it is that field is not lending this particle mass that's correct but yet it's still responsible for the gravity right how does that work yeah very good questions okay so in the standard model and as I as I say our theory is much I would say is much more compelling than the theory of wimps or indeed any other theory of dark matter because before our work the only way people had to explain the dark matter was to add something else to the standard model right and there are thousand different things you can add and each one could explain the matter so we are trying to explain the dark matter by adding nothing but just taking the absolute bare minimum of what's necessary for the standard model and what we found is that this is a little corner of the standard model involving these right-handed neutrinos which with with some modest assumption but adding nothing with a modest assumption that right-handed neutrino can be the dark matter so let's look a little bit of this right-handed neutrino now it's it's in the in the most general form of the dark matter the right-handed neutrinos are only allowed to couple to two things the Higgs boson and to gravity but what we've done is reduce the model by insisting that one of the three right-handed neutrinos only covers two gravity it doesn't couple to the Higgs boson at all and it's left-handed partner if you like for every right there's a left the left hundred one is massless the right-handed one is stable these two things go together and neither of them couple to names both versa so where do they get where does it get its mass from if not from Higgs boson and the answer is that because the right handed neutrino doesn't couple to any other forces other than gravity you are allowed in the standard model of particle physics to to give it a mass which can be very big and that is what we call a bare mass it's just put in to the model it's not disallowed you say the standard model is sort of very beautiful construction which disallows masses it sorry which according to which the only way mass can be obtained is through the Higgs boson and that's true for electrons for quarks and for the left-handed neutrinos they can only get masses through the Higgs boson but for the right-handed neutrinos you can actually just because they have yeah because they don't couple to any of the forces you're allowed to just give them a mess and that mass can be very very big and so that's what we do we give that right-handed trainer a mass it does not come from the Higgs field but one is allowed to do that by the normal rules of the standard model of sort of consistency of physics this was like the fact you could do that was discovered in the 1970s it's called a seesaw mechanism it very naturally explains you can you're allowed to put in these masses of the right-handed neutrinos they are allowed to be very heavy masses and then there's what's called a c-store mechanism as you make the right-handed Greeners heavy the left-handed neutrino masses get very very small and you know what we observe in nature are is indeed that the left-handed neutrinos do have very small masses and so this is a success of the seesaw mechanism you give the right-hand neutrinos masses big masses and as their mass gets bigger the left-handed neutrino masses get smaller so that's the seesaw and it's you know very well motivated from particle physics we've known since the seventies so what wasn't noticed is that one of these very heavy right-handed neutrinos is the perfect candidate to be the Dark Matter now back to this idea of the universe at large scales being very very simple how does entropy play into this does the universe get simpler as time moves on yes that's a wonderful question indeed the universe it's extremely simple at large scales in space right as I've explained when you look outwards the further you look the simpler it is it's basically almost uniform with this extremely simple superposition of waves on top of it scale invariant random waves very small amplitude so it's simple at large scales in space it's also unbelievably simple at our scales in time now what do I mean by that well we live 13.7 billion years after the Big Bang but if we go to 20 billion years or 30 billion years after the Big Bang based on what we see now we can forecast what the universe will look like and what is happening what will happen is that the dark energy which is absolutely constant in space and constant in time that dark energy will take over the universe because everything else is being diluted away the matter the radiation the density is falling the number of galaxies you know these are all being diluted by the expansion of the universe the dark energy is not diluted by the universe's expansion so in the far future basically it'll be in a universe full of nothing but dark energy absolutely smooth no galaxies or objects and so indeed the the universe in the far future is extremely simple now what about entropy well you know entropy is supposed to grow according to the laws of thermodynamics you know things the entropy never decreases disorder always grows and then it turns out that gravity is able to contribute to the entropy and so you have two types of entropy you've got the entropy in ordinary matter and that's maximized when the ordinary matter is as smoothly distributed as possible but then you have the entropy and gravity and the entropy and gravity is maximized when this dark energy takes over everything else we say the entropy is maximized in de sitter space and de sitter space is this kind of completely smooth uniform universe dominated by dark energy so it turns out that the dark energy future of the universe is the maximum entropy state possible and so the universe started from zero entropy at the big bat an extremely simple beginning it ended up in this maximum entropy state which is ill also extremely simple and all the complexity is in them both in space and in time so we live in the middle we are literally in the middle of the universe around us obviously that's what we can see so we're in the center of it but we're in the center of it in another sense we're in the center of it on scale right so the very tiniest things are elementary particles with the the mezzos scopic things are us and that's where all the complexity is and the very largest scale things boast in space and time is the dark energy which is again extremely simple so you know the this picture is kind of the return of the notion that this we are special we live in the center of the universe you know the the this was discounted by the discoveries in the Middle Ages people used to think that the earth was the center of the universe and then we discovered that no the somnus the center of the solar system and then we discovered lots of other suns and stars and galaxies and that made us feel more and more ordinary but in fact we're not that ordinary because we live in the middle and the universe is you know and the middle is where all the complexity is so I would say you know we physicists are just getting ahead around this notion it's not fully understood yet quite what the simplicity means at very large scales but I believe it's absolutely as fundamental as the simplicity at small scales right so it was a huge discovery when we realized that everything around us is built out of particles elementary particles electrons protons the basic building blocks of matter are extremely simple but I think it's equally important that when we go to large scales the universe itself is like a giant elementary particle it's extremely simple and then of course the large some of the largest objects in the universe the black holes we are now able to detect these are also extremely simple I mean they may be millions of times the mass of the Sun but they really are like just big elementary particles so our physics you know attain simplicity at very tiny scales and at very large scales is I think the characteristic of today today's physics how do you unify physics and see its simplicity on small and large scales and its complexity in the middle you know in a way this tells you so so when you say when I say the complexity is in the middle suddenly you realize well perhaps we are the most complicated things in the universe right because we we're in the middle and when we go to larger scales we don't see anything more complicated than us in fact it goes the other way the larger scales we go we get things are simpler and simpler so I think this means that in a certain sense we may be the leading edge of complexity in the universe and that is occurring on our scale in the intermediate scale they are large and small scales things are extremely simple that's amazing in it it's almost like time repeating itself because I don't it reminds me of Aristotle so right we would be the coma Aristotle's Revenge we would be the culmination of the universe in other words a conscious thinking organism is the most complex thing in the universe there's a beauty to that again an elegance there is a beauty to that now I was trained as an elementary particle physicist right and so for the last whatever hundred years elementary particle physicists have been picturing the universe as built of building blocks right and you build it up into more and more and more complicated structures and that mindset still underlies most thinking in so called fundamental physics in string theory you know you ask a string theory how do you build a universe well you have an awful lot of strings and you add them all together and you put in extra dimensions of multiple ingredients and then a common you know the outcome of string theory was what it was the multiverse with if you go to larger and larger scales in the universe it gets more and more complicated that's where the string theory picture led to and probably was inevitable in any picture that you build from front building grew from the bottom up what I'm saying is that the observational evidence is that that is not our nature works nature works equally from the bottom up and meaning small scales to large and from large scales to small and that second part the large to small is all about gravity and so to understand that we really need to understand gravity and the connections particularly to quantum mechanics because that's how you count states in the system is using quantum mechanics and that is a formalism we're only just developing now so I'm being guided caught by theoretical ideas but in large part by observations observations are just telling us the universe works in this peculiar way from small to large and from large to small and we probably are the leading edge the most complicated things in in the universe so it's a very different way of thinking about physics and I think if it succeeds it will lead to a revolution in physics just as important as the introduction of relativity or quantum mechanics in which the you know if you like the starting point the minimal ingredients are both at small scales and large scales now the genesis of the universe we talked briefly earlier about the universe being pulled out of the ether or what everyone wants to call it whatever whatever a universe is pulled out of how do how does that happen yeah let's say well again I'm working part by analogy there is a real phenomena nature where you can drag particles out of the vacuum a strong electric field and very very beautiful process let's talk it just a little bit about that process because it really is stunningly beautiful and it was understood in the early 1940s that this had to be possible when you combine relativity and quantum mechanics it was inevitable that particles could be dragged out of the vacuum and then we talked a little bit about it so if you're able to picture a particle going forwards in time and maybe think of time as the vertical direction you know in space what to visualize it and spaces the horizontal directions so normal particle would go forward in time you can also imagine a particle which travels backwards and then what you can imagine is a particle which goes backwards in time but instead of continuing backwards in time it turns around and and then goes forwards in time and when it goes forwards it goes forwards in some other place in space you know so it really performs a loop in space-time it goes back in space-time and then forward that was the picture realized in the 1940s that when you combine relativity in quantum mechanics that had to be possible it had to be possible for a particle going backwards in time which is actually an antiparticle to turn into a particle go going forwards in time which is a normal particle and so for an observer sort of looking at the universe at some time after this turnaround they would say oh there are two particles one is an antiparticle one is a particle actually they're just two facets of the same particle it's just that it turned around in time and that's our sort of unified picture of the universe there are two sides to the universe one side on one side you could say is going backwards in time and on the other side it's going forwards in time but it's all a matter of perspective somebody else could say oh no III think of the particle going backwards in time and the antiparticle going forwards in time so you have to be very careful whose perspective you're talking about so yes rather than saying when you have this picture that a particle antiparticle pair is created out of nothing that picture really cell you know there's another interpretation of it which is says no there really isn't a none team a particle antiparticle pair it's really just one particle okay that happens to have gone backwards in time and then turned around and went forwards in time and you're just looking at it at one particular time and you're seeing two particles because you see it going backwards through that moment of time and also going forwards through that moment of time and this is actually a very old idea due to John Wheeler one electron and wheeler used one electron he said maybe you know we see billions of electrons and positrons or ante electrons in the universe they do seem they're more electrons and positrons but in physics we can create both of them and so Wheeler said well what if they're all the same particle and when we see it as a positron it's it's just going backwards in time and when we see it as electrons going forwards in time well then there's no mystery as to why they all have the same charge because they're all the same part so instantly you've explained why every electron has identical charge and every positron is exactly the opposite why because it's all the same particle there is only one particle in the universe right so absolutely beautiful idea and it may that idea may actually be realized in our cosmic because we now have two sides of the universe on one side we have more particles going forwards in time more electrons on the other side we have more going backwards in time those are the positrons right but maybe there is only one okay in fact maybe there's even zero net and maybe it's all our clothes you know there's this single particle and it just goes around and around in this loop and where it's going backwards on one side of universe a that's antimatter where it's going forwards but more of the time that's matter and the quantization of charge the fact all particles have the same electric charges kind of automatically explained so yeah indeed this is one of the directions we're pursuing that maybe we can explain the quantization of charge another issue is the arrow of time this is again one of those philosophical questions whined as time seemed to be going forward away from a Big Bang you know when the laws of physics are the saving when you reverse time the laws are invariant they you know if you run a film of a physical process backwards it's still a valid physical process so where did this direct arrow of time come from and so again our picture of the cosmos gives us the opportunity to solve that problem and this is something where we're looking into very carefully and we have a tentative solution to the problem of time and and indeed it you know the the resolution is that there are parts of the universe where if you like from our point of view time is going backwards and in our part it's it's going forward and and somehow this the the hole does not violate the symmetry of the laws of physics the standard picture of cosmology where you know the universe starts small ends up big that violates the basic symmetry of the laws of physics under reversing time because if you reverse time you start big and you end small our picture doesn't do that because it has these two sides of the universe kind of going in opposite directions and the whole is invariant under reversing time so I think we have a chance to solve some of these kind of deep philosophical questions which which which have been unresolved for decades and and by the way these are not simply academic well they are academic questions but people they're the basis for everything so for example when you use the laws of electricity and magnetism to figure out how particles influence each other you can't use those laws unless you assume a certain you assume something about the direction of time you know so for example when I wiggle an electron it will send out radio waves and those radio waves will influence other charged particles to the future but we always assume that wiggling an electron now does not influence particles to its past because if if we allowed that we'd get into all kinds of conundrum what's going to happen to me yeah causality causality am i influenced by something in my future you know so we always exactly but the way we implement causality and the and it's purely as a result of our observational fact that we see causality works you know but the way we implement in it in our equations is kind of ad hoc we just put it in as an assumption oh in order to preserve causality we have to we have to ignore some solutions to our equations and and keep others so we keep the causal solutions and we throw away the a causal ones what I'm saying now is in this kind of two-sided universe we have an opportunity to mathematically solve that problem to understand why it is that we have to throw away the a causal solutions that may be imposed upon us by the mathematical consistency of the universe so let's give in to this idea of a double sided universe yeah first and foremost very a very popular thing with in cosmology today or if you want to call it cosmology it might even be bigger than that is the idea of a multiverse yes this necessary or is it knocked out in your model I would say the multiverse is a logical consequence of a certain mindset the mindset I mean in in brief I think the multiverse is the most ridiculous scientific theory of all time okay because a lot of things completely untested and its worst it's just an excuse for saying okay well we can't explain certain things about our universe that we all just assumed there were lots of other universes and we happen to be a random sample in the space of all the universes it has no explanatory power at all in the way that it's being used I'm very much against the multiverse because it it it's it's not a tight framework it's not a predictive framework it's that kind of just so switch some people find satisfying but I do not so yeah and then the other reason I don't like the multiverse is it seems to be inconsistent with observations I mean when the larger the scale we look at the simpler the universe is we don't see evidence of wild randomness on large scale so but the reason this kind of crazy hypothesis of the multiverse arose was because of the development of particle physics you know people made colliders and they found electrons protons and then other particles like gluons and W bosons and and neutrinos and basically as you went to bigger and bigger colliders you saw more and more particles so the whole pursuit of theoretical physics became about adding a new particle every time you did a new experiment you saw a new particle so you incorporated another particle into the model the model got bigger and bigger and and this worked fantastically well this philosophy of just adding stuff it worked really well until 1980 and around 1980 the standard model was done we'd seen all the particles which we have ever seen but the theorist kept going they kept adding things okay so the theorists kept adding more and more particles and they made grand unified theories which typically have hundreds of particles and then they went to super unified theories which have thousands of particles and then they went to string theories which have even more particles and extra dimensions of space-time which has many more additional parameters and possibilities and basically the theories either in theorists I believe went overboard experiment ran out of new particles but theory kept going and the logical consequence was the multiverse because the theorists were constructing such complicated setups without any experimental foundation that they ended up in this kind of wild crazy space of hypothetical universes and by the way not one of which have they successfully explained it's beginning because when people talk about the multiverse these are people who don't tackle the real problem of what happened at the Big Bang that you know I just want to solve the universe wherein I I'd rather not speculate about other universes that we can't solve I'd rather focus on the problems which we know are real in our universe and try to stop hell so yeah I think the multiverse will go down as a sort of diversion from good physics I'm very happy about it because it's diverted a lot of very smart people into speculations which I believe won't go anywhere leaving the space of thinking about the real problems to only a few of us and and that's fine again it goes back to simplicity a a solar universe is much easier to understand and probably well it's more probable now let me ask you about this though there's one thing that the multiverse people tend to bring up that gets a little metaphysical I suppose the anthropic principle why should we be special in this universe yes so again this is a very appealing at first sight the anthropic argument and I must admit you know when I first came across it I I got very excited and I thought you know let's recondition Lee you know so for example the expansion rate of the universe is called Hubble's constant right and what does that mean it means the expansion rate has measured by Edwin Hubble who knows so when you calculate it maybe you should of course assume a universe which is expanding but maybe you do need to put in the astronomer maybe you need to put that in as part of your theoretical framework and ask exactly what did that particular astronomer see that's fine that's normal science that's kind of taking into account the selection of observers and asking what they would actually see that's just doing your science better and in more detail so I think no one can object to the you know the influence of the observer on the experiment I mean we know that in quantum mechanics you must be very careful to understand the ways in which the observer you know affects the final experimental observation so that's all good and the anthropic argument is is if done in that way would be completely acceptable unfortunately it's not done in that way it is applied in cases where we can't predict anything as a sort of excuse for why things might be that way so typically you know the most successful application of the anthropic principle principle was to explain the dark energy and it explained it by saying well if the dark energy had been much bigger than we observe it then it would all disappear to expand so rapidly that we would never have formed galaxies you know then you get into the detail of that you know and and the assumptions behind it which are many many many and it doesn't explain the number you know it never it's more of a an explanation which is sort of a just a way of living with an awkward fact which you don't so I'm not in favor of that kind of argument because I think in order for science to progress in a sense we must keep looking for simplicity and looking for real explanations meaning unter tative predictions based on what we already know which can then be verified in experiments and the trouble with the anthropic our argument it's never like that it's always applied to situations where you know something you've measured something it feels a bit awkward you know why is it like that and then you develop this rationale for maybe you know maybe it had to be that and I find that very unsatisfactory and I think particularly for the dark energy because the dark energy is such a fundamental parameter in the universe it's almost like you know it's more fundamental than the mass of the proton I mean the the energy of empty space is a number maybe everything should be referred to that number whereas worked and throbbing people say is you know let's assume that number was random there are parts of the universe in which that number is big then parts where it's small and then we sort of plucked our universe out of the hat and and it happened to take the value that it does and I don't like that explanation because it's not got any real explanatory power or predictiveness whereas I think so I think you know if you think back to Maxwell or Einstein or Dirac you know the theorists who built the standard model and our theory of gravity would they have been satisfied with the anthropic explanations and I am very clear in my mind the answer is no they would say you know come on guys be serious build a real theory so I think the the appeal of the multiverse theory and the entropic principle is very much a phase which modern physics is going through I hope it does get through it but I am convinced it's not really fruitful not not going to be a fruitful speculation and I heard about the entropic principle from Stephen Hawking actually who I was working with and and his endorsement of it made me take it really seriously and I worked with him for a while but to implement it carefully but as soon as you try to do that you realize it's it's really not an idea of which is going anywhere and so I found that opinion about you know 15 years ago and I must say all subsequent developments have just confirmed it in my mind that the entropic principle is superficially attractive but ultimately not a fruitful avenue for research now my last question for you is that barring the multiverse s as its envisioned yes a dualistic view of the universe yes would imply an anti universe yeah what would such a place be like well I think again go back to my picture of the particle antiparticle pair being created it all depends on your point of views so from the point of view of the antiparticle it would say it would say nothing any different from the particle okay so if if we live in part of the universe which is full of matter we will describe things just in the same way as particle living on the somebody living on the other side of the universe it's just that our two points are opposite so I think what I'm looking for is an explanation where essentially the universe we see around us is is the most likely one it's and it's extremely simple and the partner universe is really no different it's only the partner because we if we try to extrapolate our universe a bigger picture we we find mathematically there's this partner but it's really no different than where we are so the framework I'm looking for which I think is emerging is the universe is much more unique than then people have imagined and that there is only one you see a very old picture with a problem with Big Bang cosmology is people say we can only see a certain distance right we can only see 13.7 billion light years or some distant because if we try to look any further we're looking right back at the Big Bang itself and then people speculate what is there at large distances and so on my preferred point of view is that the only thing that's really there is what we can see and so the universe in a sense is a small place but it's not infinite in space it's not really infinite in time it's just that when we try to picture it our classical picture encourages us to extrapolate but but that stuff doesn't really exist it's like speculating about you know green men on the other side of the Moon it doesn't really exist so again we want to look for i believe we want to look for a unified picture of physics in which the universe basically is a small place and and it's as simple as it could possibly be given the laws of physics and what i see in the observations is you know indications of that point of view rather than a crazy multiverse or or even an infinite random universe i don't see any evidence for that at the very least you know we should explore both possibilities and we'll see i I have a gut feel thing about which is more likely to be fruitful it will only really be fruitful if it makes predictions which those are unable to make but the fact we can now explain the dark matter in a much simpler way than any multiverse theorists you know is a real plus and if the experiments come in behind our theory I think ideas like the multi multiverse will gradually fade away because they won't they they haven't worked they haven't predicted the neutrino mass we've big did it if it turns out to be correct our our theory is obviously doing better so that that's how this will all be resolved it'll be resolved by whoever makes the best predictions and ultimately the old adage the simplest explanation tends to be the correct one I do believe so I mean that's what motivates me is the time and again in physics these astonishingly simple theories turned out to be correct Dirac's theory of the electron he he built it on certain assumptions but it explained the positron the anti-electron without any further assumption you know so Einstein's theory of gravity he didn't build it to explain the universe he built it to understand how to reconcile gravity with relativity but it turned out to explain a million other phenomena as well in a very very predictive way so all these sort of foundational theories would have had properties Harry you're very unique they can't be dialed you know they are what they are and and either they're right or they're wrong I haven't said a certain conceptual level the extremely simple extremely predictive that's what we need to aim for in cosmology and I believe ultimately that's the way it'll work the universe will turn out to be indeed simple theoretically simple observational E and we this will help us understand what is our place in the universe I you know I don't think we're a random weird to some extent random of course each of us is a random individual but the the fact that life emerged in the universe is very lightly anything but a random occurrence which it has a certain beauty and elegance and it's I I hope so I'm it sounds mystical but I I don't think that should detract from it well one can one could save one can save completely reasonably that we are the universe perceiving itself yes I love that idea I am driven by trying to find out the truth I don't want our philosophical preconceptions to to dominate a proper style be done and to be checked experimentally mathematically if it turns out that that deed we are you know a part away of the universe to conceptualized itself you know that that really helps us understand what we are and indeed that may be the case doctor we are out of time this has been a fantastic discussion of privilege really and I thank you for being here and I hope you come back sometime thank you very much for having me it's really been fun John did you know that we've not checked the answering machine in six whole months John boat here I guess I'll check the answering machine myself you have one new message yeah where's the podcast go here want to listen on the podcast I'll hold on someone's at my door and there's messages oh dear well message deleted you have no new messages [Music]

Channel: Event Horizon

Views: 341,750

Keywords: Neil Turok, the big bang, big bang theory, cyclic universe theory, cosmic microwave background radiation, Georges LeMaitre, astrophysics, theoretical physics (topic), Edwin Hubble, expanding universe, multiverse, Paul Steinhardt, A Quantum Beginning for a Two-Sided Universe, john michael godier, asmr, john michael godier event horizon, event horizon, physics (field of study), aliens, space, science, documentary, universe, galaxy, ted talk, ted prize, stephen hawking, antiuniverse

Id: EyJzH6LY8bM

Length: 65min 57sec (3957 seconds)

Published: Thu Jul 23 2020

Reddit Comments

[u/capt_fantastic]

and on the other side dr. turok is a dinosaur hunter

[u/maninthedarkroom]

I drew this on acid