Your Daily Equation | Live Q&A with Brian Greene

hello everyone it is Friday a little after 3 p.m. and you know what that means it's time for our live version of your daily equation in which in the live version we talk about equations but basically anything else that you feel like talking about most of the time we do talk about science quantum mechanics relativity Einstein's string theory unified theories and so forth yeah as funny as I say there and I realize that we never talk about what's happening in the world maybe you're tired of hearing all about that and seeing it all on the news but man oh man what an insane period of time we are living through in the United States and all I can say to the rest of the world is I'm sorry there's nothing more that can be said what a disgraceful situation we have in this country right now so anybody want to talk about that I'm happy to but let's go to the rarified beautiful pristine elegant realm of math physics and the universe just to have a little bit of mental rest bite from everything that's happening in the world so I'm gonna jump right in to some questions and let's see what will I begin with well Andrew Hanny asks when was the first time that the fourth dimension was introduced and what was the scientific motivation for that and I understand exactly what you're asking Andrew when was the fourth dimension introduced as an idea in physics I think is really what you have in mind there I'm guessing that's what you have in mind but mathematically people were thinking about shapes and spaces that could exist in any number of dimensions long before and you know what mathematicians do they they write down the equations to describe things that you can first visualize and see and then they're motivated by the language of mathematics to generalize the insights that they have in the ordinary three dimensions that you can see to higher dimension so Riemann who really wasn't thinking about physics applications that's not completely sure Riemann did have some of his thinking oriented by physics but to first approximation for non physics reasons Riemann and others began to think about higher dimensional geometrical shapes how do you describe the curvature of a higher dimensional geometric shape how do you scribe distances on a higher dimensional geometric shape and so the fourth dimension was introduced way back in physics it really came to light through we often think Einstein but it was really Hermann Minkowski Hermann Minkowski was Einstein's teacher Einstein's professor famously called him a lazy dog thought that Einstein was not going to really achieve anything with his life at least not in science but man was he wrong has perhaps the worst prediction in the history of being a professor my goodness makes us all feel a little bit better but Minkowski did have the great insight when Sein Stein put forward the special theory of relativity was Minkowski who said we really think about space and time unified together three dimensions of space and one dimension of time and the reason it came to that realization is because Einsteins insights showed that motion through space affects your passage through time let me say that again because that is a deep mind-blowing sentence motion through space affects your passage through time nobody thought that before according to Newton you can move through space any which way and the temporal quality the time it just elapses the way that it always would Einstein said that's not true if you move through space then someone who's watching you will note that your clock is ticking off time more slowly than it was when you were stationary motion through space slowed your passage through time so Minkowski says we now have a deep connection unexpected deep connection between space and time let's knit them together into a four-dimensional structure called space-time and within that rubric the equations that Einstein gave us have the most elegant and economical formulation so that's where it happened in physics and that's the scientific motivation for that let me go over I saw some question that I'd liked him oh yeah well here's a so Jessica from Wichita asks when you talk about the equations of the universe are you referring to equations that are somehow out there part of the universe or are you describing something that we humans make up to describe the universe so yeah it's a very deep question is math a description of the world or is math part of the world and by world I mean reality and I don't know the answer to that question nobody knows the answer to that question in the course of my own career in my perspective on that has shifted a number of times there have been occasions where you just sort of feel that the math is out there and all you're doing is revealing and for I'm Stein of course you're revealing a masterpiece sort of like the way sometimes people describe the sculptures that are created by the great se Renaissance sculptors as being embedded in the marble and although sculptor is doing is chipping away the excess material to reveal this masterwork embedded within the marble or is it that the marble just has no internal fundamental structure and it really is the artist who is sculpting out of that chaos if you will something of great beauty and great order so it's kind of analogous to that question my view now and it's been this way for a while so maybe I'm done waffling back and forth on the issue my view now is that math is a language it is a language of human invention it's a language that's particularly good at articulating patterns and because the world happens to abide by patterns I'm talking about the patterns abstractly that two plus two equals four or the pattern of the moon going around the earth at a certain regular rate or the earth going around the Sun at a regular rate or when you throw a ball through the air it goes in a shape that is repeated over and over again when you throw the ball over and over again these kind of patterns are right for articulation right for description in the language of mathematics and that's what we do as physicists try to find those equations that describe those patterns so I would put it that way as of today I would say that's not that the math is actually out there it's the language that we invent to describe what is out there and I should say that question brings to mind what a question that hasn't been asked right here but it's very similar to that question which is am i inconsistent and someone has called me on this am i inconsistent in my description of the universe because often times I will speak as though the laws of Einstein's general relativity laws as Schrodinger quantum mechanics laws of Newton some mechanical I often describe it as if those laws govern the universe as if they are somehow there and they are enforcing the mathematical description and if they're there enforcing it and they are transcending human presence if the laws are governing the worlds not we humans are governing the world then haven't I now said something inconsistent on the one hand I'm saying the mathematics is a human invention at the other hand I'm saying that the math is governing the universe and I'm not trying to say that we humans are governing the universe so what in the world am I going on about well it's often just a softness of language that I think most of us understand if I was being really precise here's what I would say and if ever I say something in these sessions or others that feel inconsistent on this point come back to this description my view is there are laws there are laws out there that transcend human presence I don't know the right language for describing those laws as of today the best language that we have is mathematics and therefore we use mathematics to articulate the laws of general relativity and quantum mechanics and classical mechanics and so forth but that's a description the laws are out there the laws do govern the laws are controlling in the sense that the processes of the universe don't step outside of those laws not can I prove that I can't what do we do we look at the enormous mountain of data accumulated in some sense since the beginning of human civilization and we have never found repeatable examples in the world in which the patterns were violated sometimes we didn't understand the patterns and we needed very intelligent individuals to come along and give us a deeper understanding of what their patterns are and they phrase those insights in the language of mathematics but to my mind those mathematical sentences are approaching an explanation and understanding of the laws that are out there but I'm not saying that the laws themselves are necessarily framed in the language of mathematics maybe they are maybe they're not so from that perspective it's consistent to say that mathematics is human invention that language to describe the patterns the patterns described by laws are out there what's the real fundamental way of describing those patterns I don't know maybe it is math maybe it is not on that we do not have an answer okay what else do we have so a seat - asked what are the future goals of CERN's Large Hadron Collider which is an important question to ask a lot of money was put into the collider and the primary initial goal was to find the Higgs particle the Higgs boson this little packet of the Higgs field which Peter Higgs conjectured surmised would be a field uniformly filling space that would exert a kind of molasses like tug on any particle moving through the universe and that molasses like tug would be the origin of the mass of each and every particle so there was a big puzzle before Higgs came along which is how do fundamental particles acquire mass because the mathematics seemed to suggest that all particles should be massless the mathematics relies on certain deep symmetry principles and the symmetry principles seem to demand that the particles were massless and Higgs is resolutions this was he said look the particles are massless fundamentally from the get-go but once those particles are moving through space they acquire mass through an interaction with the environment not because they intrinsically have heft per se but rather because they're interacting with the quality of the environment as the particles move they are like little pebbles trying to make their way through molasses and just as the pebble will feel a drag force from the molasses particles feel a drag force from the Higgs field how do you try to prove this crazy sounding idea well the theory that Higgs put forward also shows that you should be able to slam space by having particles collide at high energy and when you slam in some sense empty space it can cause the Higgs field to jiggle and if you jiggle it in the right way little particle sprays will fly off the higgs field sort of like if you slap the surface of water droplets of water will spray outward and the droplets of the Higgs field that would spray outward would be Higgs particles so the Large Hadron Collider was built to try to find those Higgs particles and as everybody here I hope knows that was an incredibly remarkably successful undertaking 2012 we found the particle okay good so the question then is what's next now what we hoped would be next would be the detection of so-called supersymmetric particles these are particles put forward by a different theory a theory called supersymmetry whose development goes way back to the early 70s it's a another type of symmetry first discovered actually by people studying string theory just saying it was then generalized to other areas of particle physics that don't have to have strings in them at all but it's a very general phenomenon that for every known particle that we have so far detected supersymmetry requires that there's a partner particle so for electrons you should have select ron's for quarks squarks neutrinos neutrinos don't look at me like that I don't make up the names all right I just follow the conventions and so the hope was that the Large Hadron Collider would find these partner particles to the known particles and that was the next goal and the fact of the matter is we've been at it for some time and none of the supersymmetric particles have been found and that's kind of sad at some level for many of us but I mean nature not constructed to make physicists happy that's something that steven weinberg has emphasized to us repeatedly but yeah it would have been nice to find those particles we still may if I look back at my own career I would say that 90% of the papers that I've written in one way or another touch on supersymmetry so how sad would it be if if this quality in the mathematics is not realized in the real world thankfully some of my papers are just in the mathematical side of things so whether or not the particles are real the mathematical insights derived from the symmetry they're unassailable but yeah it would be great to find the supersymmetric particles circumstantial evidence even for string theory so my hope is I see that that's what will be next but the window of opportunity is shrinking and shrinking so I wouldn't hold your breath on that one and then after that we may need really to upgrade the Large Hadron Collider to a machine that has greater energy reach China is talking about the possibility of building the next detector the next accelerator with detectors of course and that may be ten twenty years into the future so it could be that in the worst of all circumstances particle physics may at least at the level of the energy scales that we hope to probe ever higher and ever smaller length scales that may go into a hiatus in the not-too-distant future as we wait for a machine that can really take the leap to ever higher energies so I don't know the answer but that is certainly one possibility perhaps that's the the least happy one but look we can still find the supersymmetric particles we could still find unexpected things in fact that's probably the best answer to your question I see what's next I don't know but I hope it's a big surprise we live for the unexpected results that forced us to go back and rethink our theories so that that may be hopefully what happens next Yash Shah asks can general theory of relativity be questioned on the basis of Hawking radiation and the answer yosh is absolutely not absolutely not so Einstein's general theory of relativity is a classical theory it is a theory that doesn't know about the quantum nature of the world Einstein developed the general theory of relativity in you know 1907 to 1915 those were the years in which a parallel track was developing quantum mechanics but Einstein wasn't waiting for quantum mechanics to be completed before he dove in to try to come up with a new description of the force of gravity so Einstein's theory doesn't talk to quantum mechanics from the get-go and Hawking radiation emerges only when you meld certain aspects of quantum mechanics with the general theory of relativity so it's not that Hawking radiation contradicts Einstein's theory Hawking radiation is a natural outcome of extending the general theory of relativity to include certain quantum mechanical qualities so in that sense they are naturally linked together in a progression from the classical description to the description that goes one or two steps further to bringing quantum mechanics in to the story okay hello professor greens Sami Saeed asks if we go into space and rotate in the opposite direction of Earth's rotation and twice the speed isn't that time-traveling so so the answer to that question is yes and no I kind of think from the framing of the question Sami that what you have in mind is that scene from Superman where Superman kind of circles around the earth really quickly in the opposite direction to the Earth's rotation and somehow goes backward in time and I think the intuition there is that if the earth is turning this way and time is going forward then if time was going back where the earth would kind of go the opposite direction or at least if we go the opposite direction we're going backward in time and none of that none of that holds any any real water the orientation of the spin of the earth whether viewed saved from the North Pole down is counterclockwise or clockwise is not what determines the arrow of time from the past toward the future instead the arrow of time from the past toward the future as you can see in your daily equation maybe it's the last episode that I did the things I think it was number 32 or something that comes from considerations of entropy second law of thermodynamics the Big Bang being a highly ordered state and so forth and those qualities of the world are not dependent upon the very specific orientation of the Earth's spin now there is a way of interpreting your question which does yield a more positive result which is whenever you go into motion your clock will slow down relative to my clocks if I'm looking at you in motion then your clock is going slow so if you then return toward me undergoing some round-trip journey some accelerated trajectory to return to the starting point you will have not traveled into the past you'll have travelled into the future because my watch will have ticked off more time than yours and by my watch I mean everything about me itself will have elapsed in a greater duration during your journey so you will have jumped into a later time period and so there is a kind of time travel that comes from precisely what you described that kind of motion but it's not time traveling toward the past although you didn't actually say toward the past so maybe that's what you have had in mind it's time traveling toward the future so Sami if I misunderstood your question you should come back at me I'm happy to revisit it if I didn't interpret your question correctly Paul C asks with eight stars and therefore definitely requires me to answer hi professor Greene how was the Big Bang low or even zero entropy and the quickest answer is I don't know yeah I'll go a little further than that can't help it so we make an assumption that the Big Bang was highly ordered low entropy why do we make that assumption we make that assumption because it's the only way that we can articulate it's not the only way but to my mind is the most convincing way that we have ever come to for articulating why there is a direction to time right so we all know that there are these qualities of the world that are asymmetric in time various things right we age we don't UNAIDS and you guys maybe it's not you guys explicitly there are many people on my videos who remind me that I am ageing I really do appreciate that so I love it when you guys tell me how old I've gotten so thank you I really I really do enjoy that but yeah that's you're just reminding me of this important physical fact that time has a direction to it it goes from the past toward the future but even more mundane things they become hackneyed after a while but you know glasses shatter they don't uncheck splatter they don't unsplit a candles burn and they don't unburned right a gazillion things that have a temporal orientation to them why in the world do they have that temporal orientation and if you look at the laws of physics themselves as I emphasized in episode 32 the laws treat past and future an equal footing so you can't just appeal to the laws and say the laws don't allow glasses to unshadowed people to on age now the laws and principle do allow that to happen then what do you do well this is what took us to this idea of entropy that there is a natural tendency simply by the law of large numbers for systems to go from order to disorder because to be disordered is a very easy configuration to achieve there are so many ways to be disordered an order situation well that's highly organized that's hard that requires everything to be in its proper place and therefore it's very difficult compared ly speaking to be ordered and so as particles are randomly moving around of course they're gonna move toward disorder because it's so much easier there's so many more ways to be disorder than ordered but that only really holds any water if there was a state of order to begin with if you have a state of disorder at the start at the Big Bang then you'd have disorder all the time you need order in order to anchor the hour of time so that as time unfolds from the Big Bang you are creeping up toward ever greater disorder but along the way and route today you still have some residual order that's why we make this assumption now can we explain the order of the Big Bang I've tried everything papers on this none of them really are convincing because oftentimes you find that you're sneaking in an assumption of order in a different language or a different mathematical formalism so I would say that today there are some people who say it's not a question that even is worth asking because they say look you know we have one universe when people say that the Big Bang was highly ordered and therefore that's very unlikely because ordered states are very unlikely they're basing that on intuition from everyday life yeah it is unlikely that if I take a hundred pennies and I throw them on the floor they will land in the order state of all heads if very unlikely if I throw those pennies it's far more likely that the land were roughly 50 heads and 50 tails because there are so many ways in which you can get 50 heads and 50 tails someone told me how to pronounce that number maybe is on your daily equation a hundred octillion someone told me is how you pronounce that number so it's you know much more easy but that's in everyday life with pennies or other familiar structures when it comes to the universe what do you mean when you say that it was unlikely for the Big Bang to be ordered did you have many big bangs and you look at all of them and you found that the preponderance of examples had high disorder and very few had high order is that the sense do you imagine that you're throwing darts at possible universes from a range of possibilities and for your dart to hit the universe that has an ordered Big Bang is just unlikely because there's so many more universes that have a disordered Big Bang what do you mean by unlikely in the most straightforward interpretation you can say look if there's one universe you can say if these ideas are correct that it began ordered with 100% certainty it was ordered and there's only one universe period that's it so you have to be careful when you generalize from unlikely events in everyday life to unlikely events when it comes to the universe as a whole so look if we could find an explanation that really gave us some insight into a process that required or insured or entail that the universe was highly ordered at the Big Bang we'd all be happy we'd all feel like we'd made progress but if you don't have that explanation it may simply be telling us that we're asking the wrong question that the orderly state of the Big Bang may have been an environmental state that we just need to accept as is because the universe happened once and for whatever reasons for whatever reason there is something rather than nothing that something came into existence in an orderly state that could however unsatisfying that could be the answer sir view Muntean hi professor O'Brien can you explain how Einstein theory of gravity applies to us or objects sitting on the surface of the earth yeah I can't I can so the imagery that we often use in the general theory of relativity is say you have a star and the presence of the star warps the environment around us we often give a 2-dimensional image for that which is not perfect by any means but you have say the Sun and you have this warped shape underneath it now there is no underneath the Sun what's really happening it's warped all around and so forth but let's use that imagery just to have something to hang my answer on visually the earth does the same thing to the environment and means is our bodies want to slide down that indentation in space-time but what happens is the surface of the earth gets in our way like right now my body wants to slide downward but my body is hitting this chair and this chair has legs that are hitting the floor and the floor is hitting the surface of the earth the earth is getting in the way so you can think about it as if there's a slide that in the absence of the Earth's surface if the earth surface they were compressed so it was a hundred miles closer to the center of the earth my body would want to slide all the way along that from where I currently am but because the Earth's surface is there my body slams into it so the upward force that you feel right now that I feel right now from whatever structure is supporting us that upward push is happening because general tivity is trying to guide our bodies along the indentations in the space-time fabric that the earth creates but this surface of the earth is getting in the way that's certainly one way of thinking about it now as a caveat I'll note to you that near the surface of the earth the better description is not really that space is warped it's actually that time is warped I haven't actually discussed this in a your daily equation yet but I kind of should because it's a beautiful idea and it's one that doesn't get as much play as it might but when you try to understand ordinary gravity that we experienced from Einstein's general theory of relativity it's the temporal part of the distortion that really captures the kind of gravity the relatively weak gravity that we all feel and so in some sense what Einstein tells us is that time elapsed is slower and slower and slower toward the surface of the earth or toward the source of gravity more generally and objects according to Einstein are drawn toward those locations where time elapses more slowly so rather than thinking in the spatial example which is a fine way so I'm not trying to undermine my own answer here but in the spatial example I had our bodies trying to slide along an indentation as if it was a slide in a in a in a children's park or water slide in in a play world type of environment but a better description is that we're trying to move toward the direction where time elapses more slowly so maybe the cosmetics industry is a better metaphor or a cosmetics industry we spend billions of dollars trying to look as though time is elapsing more slowly Einstein's theory fits in with that urge because the geodesics in a spacetime environment point in the direction of the slowing of time that's actually what happens in the general theory of relativity and as you say that I'm gonna have to keep them back in mind I realize I've never given the geodesic equation in general relativity I don't think I've given you the equation D 2 X mu D tau squared plus gamma mu nu lambda DX nu D tau D X lambda D tau equal to 0 or gammas the Christoffel connection good I got our equation and I'm happy now so that equation till tells you the shortest possible trajectory in a spacetime environment with a connection gamma determined by a metric G and what I just described is what happens in the vicinity of a body that doesn't have a fantastically strong gravitational field and a body that's not moving relativistically so that is the answer to your question dang JA says that should be our next day of the equation dang I agree with them just not sure when exactly that will be so captain Benzino is a long question so I'm taking a risk on you captain Benzino I'm gonna read it without knowing whether it's a question that I want to address but here we go maybe dipping into science fiction here oh I'm setting to worry but black holes all right now I'm feeling a little bit better must hold infinite mysteries is it theoretically possible to create a material or substance with elastic properties to probe and send a signal so I think what you have in mind there is kind of unfurling some kind of object maybe like a big piece of rope or a bungee cord that could be rolled out from a safe distance from a black hole toward a black hole in order to probe its properties and captain BZ no I don't know if that's ever going to be practical in the real world probably it will be if life persists long enough in fact there's something called the Penrose process that Roger Penrose real iconic figure in in math and physics and by the way I'm not I'm gonna answer captain ben zena's question but I'm just just comes to mind I was thinking that it might be fun in some of these are daily equations if I bring in some of my colleagues that you maybe read their books or read their their ideas to sort of have an informal conversation of their favorite equations and some of the insights into the world that are due to them so if you would be interested in me doing that on occasion as opposed to me just talking to you straight out let me know I'd be happy to do that but but the Penrose process is one in which in principle if you have a rotating black hole and you can somehow lower down a bucket toward the black hole you can in some sense scoop out energy from the black hole through this process so people have thought about this idea at least hypothetically Captain Beenzino moreover when you try to understand the entropy of black holes the disorder of black holes one of the ways of doing that is you imagine lowering one bit of entropy into a black hole and you ask yourself what happens when the black hole absorbs that disorder but happens is the event horizon grows by a minimal amount a Planck area divided by four which is all just to say that even though you thought of this in a kind of science fictiony way we physicists often make use of thought experiments today that invoked the very kind of setup that you envision lowering things into a black hole so the answer is yes very much so at least from a theoretical standpoint it's been very useful to think that way practically I don't know we'll uh we'll have to wait and see how things evolve toward the future okay what do we have oh there's a 0.99 question maybe I'll come back to that if but let's see so Leandro scheppers asks hello professor green what happens to the energy of a photon that gets red shifted by the universe that is expanding and and that's a that's absolutely a justifiable question you know we often say that when you have a photon in expanding environment what happens is that the photon itself is somehow sufficiently woven into the threads of space-time that as the fabric expands the photon itself gets kind of pulled outward like an accordion and that stretching of its wavelength it lowers its energy makes it head more toward the red part of the spectrum assuming that was on the other side of red redshifting can be an increase in energy if you're on the other side but if you're on the higher energy side of red then the red shifting takes you to the lower energy so where does the energy go when that happens and the answer is that it goes into the gravitational potential energy you have to remember what happens when a baseball is thrown upward there's a baseballs thrown upward to go slower and slower where does the energy go it goes into gravitational potential energy because the baseballs fighting against gravity in some sense and gravity is also what's responsible for the expansion of space so in some sense the stretching of the photon is going into a kind of gravitational potential as well so that's the answer to the red shifting energy of a photon and expanding universe okay see hackers lab hi professor what do we mean by a tear in space and how does strength Eve explain these and then repair the tear in space-time always a fun question for me to address as III think hackers lab knew that I would be open to the question since I was the person with a cup of college who wrote the first papers on these ideas but so a tear in the fabric of space what does that mean well literally what we mean not literally what we mean is I hate hate when people use the word literally wrong what we mean is there are shapes that cannot be smoothly deformed one into another there are other shapes that you can smoothly deform one into another for instance if you gave me a beach ball and it was made up of elastic material I could smoothly stretch the beads fall and turn it into more like an egg shape so the beach ball in the egg shape are what we say they have the same topology they have shapes that can be smoothly deformed continuously is probably a better word from one into another there are other shapes where there is no such continuous motion of that for instance if I give you a doughnut and a ball to turn the ball into a doughnut you've got to somehow rip an opening inside there's no way that you can continuous deform one into another and so when we say that space tears what we really mean is the topology the shape of space is changing in a manner that cannot be accomplished through a continuous process so have in mind going from doughnut to ball our ball - doughnut you've got a tear or you've got a rip open the shape be going from doughnut to ball you've got to kind of cut along one of the circular parts around the the center of the donut and then you can turn it into like a banana shape and then you can reshape that into a sphere so what we found is in string theory the universe can evolve continuously smoothly between two different shapes that are topologically distinct shapes that cannot be smoothly continuously transformed into one another and string theory protects us from what otherwise would have been a disastrous consequence inside the general theory of relativity where the space cannot tear and that's really what we mean by the fabric space ripping and what we mean by strength you're allowing these processes to happen Alice says that she's getting hungry I guess that was my reference to Donuts you know Alice I'm kind of hungry too I'm wondering you know if we did these sessions long enough we should set it up in such a way that everybody gets dinner delivered regardless of where you are in the world that would be kind of we will do that no doubt one day not yet but I am tempted to bring my dinner to these sessions as they seem to go longer week after week Niraj ask professor does the size of a black hole increase as it eats space-time there's a culinary theme that we see threaded through a number of these questions now so we're back to questions of imbibing food so does the size of a black hole increase as it eats space-time well I don't know exactly precisely what you mean by eating space-time but I would say that when the black hole eats material objects if you throw those doughnuts into a black hole the doughnuts have mass they've energy and as the black hole absorbs the energy the black hole grows in size because remember that the radius of a black hole and by radius I'm there's a precise meaning but roughly speaking you can think of it as the size of the black hole it's related to the surface area of its event horizon but the the radius of a black hole is proportional to its mass right R equals to GM over C squared that's the formula for the radius of a black hole of mass where G is Newton's constant and C is the speed of light so if the mass goes up the radius goes up so as the black hole eats stuff that increases its mass its size does increase I'm not exactly sure what you mean by eating space time I've seen you have a second part of the question can it be used to test a spacetime as made of particles so you really do mean the eating of space itself and I'm trying to think how to interpret that I'm not exactly sure how to interpret that statement it is the case that according to Stephen Hawking the reverse happens that a black hole can have particles radiated toward infinity that's kind of the reverse of eating I don't want to get into the kind of gross description that is running through my head right now and the concept of reverse eating is brought to bear so I will exercise restraint and I don't know if my my wife is listening to this but I hope that you're proud of me for not saying what crossed my mind a moment to go but as the radiation comes out of a black hole the black hole is emitting energy emitting food if you will and because of that it's size gets smaller and smaller so it's kind of the reverse of what you're talking about the black hole is giving back space-time because now you have more and more space outside the event horizon of a black hole and as it's giving back that space the way it does so is it's emitting particles toward infinity so you kind of see the interplay between the size of a black hole the amount of space outside of it and the radiation that it's emitting so I hope that approaches an answer to the question that you have again come back if somehow that does not satisfy you pry out that's what is mirror symmetry and I think you guys conspired today and said let's ask let's ask Brian crane all the questions about this stuff that he did so he'll he'll feel good today so thank you for that I do it does feel good for you to ask about the stuff that I've been involved in so mirror symmetry is a property that I found with my colleague Ronan Plesser who is now at Duke this was in the late 1980s and I should say there was a another group that found effectively the same idea from a very different perspective that was led by my colleague and friend Phillip Ken Delos is now at Oxford and various of his students trying to remember it's been a long time Monica linker Rolf shimmer ik I believe are on the initial paper that they wrote back then and and the insight that we found is that when you're looking at the extra dimensions in string theory so in the most conventional formulation of strength there there are six extra dimensions note to self I should do your daily equation on extra dimensions I think I will do that but you have these six extra dimensions in string theory and what we found is the shapes of those extra dimensions come in pairs that look completely different technically they're topologically distinct they're completely different geometrically topologically and yet they give rise to exactly the same physical properties in a universe in which they are taken to be the extra dimensions and that's highly unexpected because in the general theory of relativity even if you don't understand the mathematical details what we have been describing over the course of your daily equation but even here today is the geometrical shape of space-time dictates the physical processes that ensue right if you've got a shape like this then the shortest trajectories which are the geodesics that particles will follow will be different from a shape which is radically different from the initial shape but surprisingly we found that there are pairs of shapes of the extra dimensions that look completely different to a geometers to a mathematician but are completely identical from the standpoint of physics now why is that interesting well there's a lot of interesting things there but the first application and this application we actually wrote down in our original paper with run and Plesser but it was really Philip Ken Delos and another team that put this into action in a spectacular way we found that there are certain mathematical questions about these higher dimensional shapes that can be ferociously difficult to answer on one geometrical shape but if you make use of its partner shape the mirror partner that looks different but it has the same physical properties many questions that are horrific ly difficult to answer on this shape when you translate them into a question on the mirror shape the question becomes easy to solve in essence you have a dictionary to go from difficult math questions on this shape to easy math questions on the mirror shape guaranteed that the answer you get in the easy setup will be the right answer for the difficult setup and that's a powerful tool obviously it's much easier to answer easier questions and so Philip can Delos and his crew were the first to put this into action again we wrote down the formula in our paper toward the end of our paper but I never really thought anyone would evaluate the formula I just thought it was a cool observation to go from hard to easy but Philip actually put it into into practice and was able to answer questions having to do with the number of spheres that you can pack in a certain way into these higher dimensional shapes mathematicians had answered very few of these questions you can characterize the embedding of the sphere into the shape of how many times it winds around itself and people mathematicians had answered the question for the number of such spheres if once twice but for three times the mathematicians at that time had not been able to crack that problem but in our reformulations the easy question it winds out that you can easily just write a little computer program and spit out the answer for a winding one two three four up to whatever number you've got patience for so I remember there's a wonderful conference in 1991 in Berkeley where a bunch of mathematicians came bunch of us physicists string theorists came to try to understand the math and physics of mirror symmetries real exciting time I remember I gave the opening talk at that conference trying to speak as best as I could at the time and a language that would be acceptable and relevant to both the physicists and the mathematicians who generally speak completely different languages you might think we all speak mathematics but honestly it's like when I went to Scotland I met some people in Scotland and I was like I could understand like only I don't know 25% of what they're saying we all speak English but man it was tough and mathematicians and physicists it's often the same kind of thing we got a different dialect going and the way we speak are mathematics so trying to speak to both audiences is a challenge but what happened at that conference is some mathematicians came along and they claimed that they had finally cracked the problem of how many times you can embed these spheres with winding number three it turns out into a particular six dimensional shape the quintic hypersurface and complex projective force based details don't really matter but it's just a complicated problem they had their answer and the physicists had their answer coming from our work in the work of Ken Delos and the answers were different and of course the mathematicians thought the mathematicians were right the physicists thought the physicists were right and we left that conference not knowing which group was correct a few months later the mathematicians send around an email saying that they found a computer bug in their code and when they fixed it lo and behold the answer they got agreed with what the physicists had been saying so physics triumphed it was very exciting time and again the mathematicians at that time had difficulty going to winding number 4 or five or six but we physicists it was just a matter of hitting a button on a computer and spitting out the answer so there's a very powerful realization this mirror symmetry for solving a collection of interesting mathematical problems anyway so you brought me back thirty years now to some exciting times in the early days of my own career so thank you for doing that okay let's see so lion king lion king asks in the last daily equation you said that entropy can actually decrease if a system has a small configuration like I did if you remember I don't know if I did it I think I did I did like 10 pennies I think I did do that I did 10 pennies and we found that if you throw the pennies over and over again using this computer code that Danny Swift wrote for me World Science Festival so that was sort of fun to have that that you know if you allow the computer to throw the pennies on the floor on the table ten thousand times certain number of times you see an ordered outcome all heads are all tails so entropy in some senses is going down to metaphor of course but the metaphor is that on occasion random processes can yield ordered results it just happens on occasion so the question of Lion King asks is is it possible therefore for a particle to travel back in time if you're sort of in a small enough region or a small enough number of particles and I understand the intuition behind the question lion king but I don't mean to be flippin but it's a conflation of two ideas and this is really important point if time were to go backwards if you actually wind a film backwards then indeed you can easily go from disorder to order and I showed you films of that in your daily question you've seen them on your own you wind the film backward and the shadow glass does unshadowed the egg does on splatter so it leads you to the intuition that going to lower entropy is the same as going back in time and that intuition is wrong it's a natural intuition I get it it really comes from thinking about as I just mentioned winding films backward in time but that's not the right way to think about things lowering entropy in the manner that I was showing you is a forward directed temporal process I was truly imagining throwing those coins with time ticking off in the ordinary temporal direction and noticing on occasion holy smokes I got all heads entropy went down nothing to do with traveling backward in time it's simply the fact that entropy and its increase is a statistical likelihood not an ironclad law and that's the point that I was making there are these ironclad provisional laws be they Newton Einstein Schrodinger when we write down those laws we're imagining that the laws hold whether the right laws is a separate question but if they were the right laws they would hold they would always hold they would never not hold that's what we mean by the traditional word law when applied to the universe the second law of thermodynamics however changes the meaning of law a little bit we are not saying that there's an ironclad rigid progression of entropic increase we are saying that there's an overwhelming likelihood of that progression but on occasion entropy can go down nothing to do with traveling backward in time okay um he's going by too fast I saw one that I liked and it's gone Alpha Omega spy asks how was your mother thank you alpha mega spy that is so nice of you to ask she's she's hanging in there she is having a tough time but you know when you're 92 going on 93 it is difficult it is it is hard but she actually moved from my house to my sister's house in Massachusetts so she is convalescing there at the moment at some point she will be back here but thank you thank you for asking okay so your question is since particles do not care about time why should particles care about natural selection why should particles seek to improve themselves and there are two questions in there they are highly related let me take the second one first why should particles seek to improve themselves so Alpha Omega spy you're framing that in language that I often used to you're framing it in anthropomorphic language you're framing it as though the particles have a will have a consciousness and you know my perspective I don't think that they do so when we talk about why particles seek to improve themselves I'd rather reframe it as why is the case that over time particles can find themselves in more refined more orderly more organized configurations how in the world would that come to be and the idea here is that when molecules learn a particular unusual trick when they accomplish a systematic basis a particular feat then they're subject to a version of natural selection that ordinarily we applied to living systems but can equally well apply to nonliving systems which is this so as particles learn to replicate make copies of themselves so imagine I've got a collection of particles if that collection of particles can make a duplicate of itself and the duplicate can make a duplicate of itself then we find a natural means of taking stuff from the disordered environment and templating it into a repetitive molecular order a repetitive molecular structure a parent molecule has children the children have children and the way the children come to be is by the parent grabbing raw materials and making a copy of itself and therefore you can see that those collections of particles that are better at making copies for whatever reason their electromagnetic structure more readily pulls in the same ingredients out of which they're made their arrangement provides a natural template that allows for a quick replication whatever the reading whatever the meaning and reason for that the point is when particles get better at making copies they dominate they dominate the environment and if they have a progeny a child that perhaps is mutated maybe an interchange of two particles in the arrangement if that arrangement is better able to make copies and have progeny then that version will dominate the demographics so you see a natural move toward more organized structures that comes not because animal species one is battling species two in an arena of combat among living systems but rather molecule one is battling molecule two in a combat that's taking place right down at the level of particles and winners of that combat can naturally dominate the world now how does this relate to the fact that the particles don't care about past and future well again it's coming from in essence the order of the Big Bang the orderly structure of the Big Bang allows for little pockets of order to form those little pockets of order which are in some sense residual order from the Big Bang can make copies of themselves and the molecular Darwinism that I was just described can roll on forward if the Big Bang was a highly disordered state maximal disordered State from the beginning if it was a collection of black holes then we wouldn't have the opportunity for the ordered structures to ever get off the ground so the arrow of time that I described in the last episode in terms of the orderly Big Bang second law of thermodynamics and drive toward ever higher entropy is really an arrow of time that would apply to all processes for which we see a temporal asymmetry including molecular Darwinism so it's the same answer as an episode 32 ok gemstone replicators yes I'm absolutely talking about replicators but replicators down at the level of collections of molecules would II live at last hello Bryan Chad yes I give you the thumb up woody you feel free to ask a question if you'd like Naveen Kumar makes a quantum-mechanical prediction that the probability that I will see this question is certainly zero did you see this question or do you see this andnothing Kumar I do not see your question so your prediction is correct the probability of my seeing it is zero and I never ever saw it okay so what else do we have here I am asked do we understand space-time fully if not then what are the gaps in our understanding of space-time and I would say that really is the central question for 21st century fundamental physics we don't by any means understand everything about space-time at best we understand certain qualities of space-time we learn those qualities from mostly from Einstein's special theory of relativity general relativity we learn that time has this weirdness it slows down in motion it slows down in a gravitational potential we know that space also contracts along the direction of motion from special relativity you know that space warps from the general theory of relativity but is that the end of the line no way not at all if you were to ask me what do we even mean by space and time I can only give you a very rough answer an answer that's really not much more satisfying than the answer given by Isaac Newton you know Isaac Newton basically said what is time didn't give a definition Isaac Newton the per capilla just says time flows equably he's just sort of saying they're sort of equal intervals and a repetitive pattern to the beat of time but that doesn't give a definition of time and when talking about space I don't remember the exact language someone can give it to us from the Principia but when talking about space Newton's description was again very much focusing upon intuitive characteristics of space but wasn't telling us what what space actually is so the answer to your question I am is we do not full understand space-time and the gap is we don't have a definition we're gonna have a definition for space or a definition for time some fundamental definition I think of I said before my suspicion is that the next leap and understanding will be when we can identify ingredients that make up space and time sort of molecules and atoms of space and time and loop quantum gravity is an approach that believes that it has insight into that question I'm less clear that those insights are the right direction to go but it's just to say that in loop quantum gravity there's some thought about what the atoms of space and time might be in string theory in recent days by days I mean last few years there's been insight into relationship the relationship between quantum entanglement and in a sense the threads of the space-time fabric and that's an exciting development but these are all tentative and so the next big breakthrough will be moving from these tentative ideas to ones that have a more solid mathematical and ideally observational footprint so that is vital to have a full understanding of space-time we are certainly far from that at the moment all right let me just look over from our Twitter side of things I haven't been giving much Twitter love in the last hour okay Amanda says it seems like every single event when analyzed specifically enough can be seen as an unlikely event and I agree I agree so why don't we take that up with with the pennies because that's an important point and I remember when I was doing episode 32 in the back of my mind Amanda I was wondering if I had said enough to address that question or not and I don't think I did so let me point out following when you throw pennies on a table hundred pennies every outcome is just as likely as every other outcome in the sense of specifically delineating the disposition of each and every coin so imagine the coins are numbered one to a hundred and every outcome if you want to specifically delineate it requires me to say coin one heads coin two heads coin three tails coin four heads and onward up to coin with label 100 let's say it's heads every configuration delineated at that level of specificity is just as likely or just as unlikely as every other because just as a single coin has an equal probability of being either heads or tails then if you got two coins each of them has an equal likelihood of being heads or tails so whatever outcome you have is just as likely just as unlikely as every other now framing it that way you mean to say well whoa what about the hole entropy stuff what about the hole statement that it's more likely to have 50 heads and 50 tails how do we square that with as Amanda says every outcome being highly unlikely it's one out of you know a hundred octillion possibilities each and every specific outcome what we do is we group together certain outcomes and we consider them part of the same group of possibilities so when I talk about 50 heads and 50 tails I'm not worried about whether the first coin is heads or tails or whether the second coin is heads or tails I don't care all I care about is the grand total number of coins that are heads and the grand total number of coins that are tails and there are an enormous number of configurations in that group because again as I described in the episode if you watched it you know I don't care whether it's the first 50 coins that are heads and the second 50 better tails or if you know 35 of the first 50 coin our heads and the other heads come from 15 of the remaining 65 coins right so what only matters to me is the grand total number of coins at our heads and number of coins that who tells not the specifics of which particular coin is heads in which particular coin is tails and by grouping together the possible outcomes now I have a different kind of comparison that I can make I can send to my selves how many outcomes are in that group versus this group and if one group say has only one member like all heads one soul member every single coin is heads whereas a group that has a total of 50 heads and 50 tails has a hundred octillion members because of the different rearrangements of the individual coins that can fit the bill of 50 heads and 50 tails so that's the way we get the skewing of the odds not by looking right down at the specifics of any individual outcome but rather by grouping the individual outcomes according to a more macroscopic quality in this case the net number of heads and the net number of tails very good question Amanda um another one I'll just for the heck of it since I'm over there on Twitter Zala Alex Boye 92 I have a question regarding regarding that was a very New York accent II so I'm gonna rewind the film we'll just edit that out of de finished you know we don't edit these at all so zal ex-boy 92 I have a question regarding your illustration with the change of trajectory of each and every piece of the wineglass in order for the glass to reassemble would gravity also be required to be at an opposite for this to happen wouldn't that break Newton's second law and the answer is you don't need gravity to be opposite so if you actually go to episode of 32 I spell this out mathematically I won't do the math here but in Newton's second law where the force is due to the force of gravity so you have the force of gravity as mass times acceleration when you look at the acceleration D 2 X DT squared for the original trajectory of the splattering shattering glass versus D 2 X DT squared for the reverse motion you wind up getting two minus signs in the reverse motion because X of the reverse motion is simply X of T of the reverse motion is basically X of minus T of the forward motion T goes to minus T every time you take a derivative you get one more minus sign you take two derivatives minus times minus is plus so the reverse run trajectory exactly satisfies Newton's second law with the ordinary everyday version of gravity not a reverse version of gravity that's how it works so dang jaws and says I don't agree with that gravity matters I'm not sure what dange is referring to maybe what I said I don't think so I was saying that gravity matters too but you can't change his orientation or maybe ding jaws was referring to something in the chat maybe you guys are having a side conversation that I missed but any event Paul C asks hypervisor green will you be putting episode number 24 up on the your daily channel again so episode number 24 has become this kind of enigma this legendary episode did it ever really exists is the question that we could ask now it's far less mysterious than that it's not like the what was it in The Maltese Falcon writes the MacGuffin right it's the MacGuffin episode no it really did exist as a and I'm pretty honest with you guys not pretty honest I'm completely honest with you guys and I was rushing to do episode 24 or some of you may know and later in the evening when I came back and looked at it after it had been posted I realized that I had made a little mathematical mistake in one little equation toward the end of the episode and I probably should have just left it up and done one of those I don't know errata thingies that you can do in the description I should have just done that but I felt look I'll just fix it tomorrow and tomorrow it turned into episode 25 episode 26 and on it went so I never got back to it so bottom line I am gonna redo episode 24 maybe I hate to say promises that I don't keep maybe this weekend I'll find a little time to redo episode 24 episode 24 was about bohmian mechanics the browbone mechanics I don't know maybe I could actually fold episode 24 into a longer episode where I talk about the various interpretations of quantum mechanics maybe that's what I should do so I could do the many-worlds interpretation I could do the Fineman approach to quantum mechanics I could do Dubrow Boehm approach as was the core of episode 24 and I could also do grw theory which is another approach to try to make full sense of quantum mechanics that would make for a longer episode but that's okay as you've noticed I've been doing fewer episodes but longer so maybe that's what I should do interpretations of quantum mechanics giving a little bit of the math of each but maybe spending the bulk of the time on the bomb debris theory yeah I don't know I think I think I may do is kind of like that I guess so so I think so al baqarah Farooqi professor green wants perfection in his work smiley face well you know we try we try for perfection we never achieve it but you know if you see a an era it's a little hard it kind of makes your heart hurt to leave that up so that's why I had fixed it or didn't fix that's why I took it down but we'll fix him Joshua asks hi professor green Joshua pasa can we set the geodesic equation equal to the equations of motion to derive the metric tensor for that theory example given Maxwell's equations could be quantized in metric or not like gravity and it's a natural question and you know anybody who studied quantum mechanics and then studies general relativity naturally wonders whether the means by which we quantize feels like Maxwell's field or the strong nuclear or the weak nuclear fields could those techniques be applied to quantize the metric which is the natural field in Einstein's theory of gravity and the problem is when you try to do that in the most straightforward way the quantization yields nonsensical results that's the problem we know how to go from classical electromagnetic theory to quantum mechanical electromagnetic theory we know how to go from classical strong and weak nuclear force to quantum mechanical strong and weak nuclear force and it all works all holds together it agrees with the observations spectacular when you apply exactly the same template gravitational theory of Einstein the result that you get falls apart it's nonsense I mean do calculations and the most straightforward approach to quantizing gravity the answer you get is infinity it's not like infinity should be interpreted as a highly likely probability it's infinite probability it's definitely gonna happen no and infinite probability is nonsense a hundred percent probability we know what that means 101 percent probability no idea infinite probability nonsense so that nonsense tells us that the standard approach to quantizing a system fails when it comes to gravity so what have people done will the loop quantum gravity people they found a way to modify the standard quantization approach they start with different degrees of freedom not exactly the metric something related to the metric and this is somewhat controversial but even the quantization approach that they use some would say differs in important ways from the standard quantization approach that any undergraduate learns in a quantum mechanics course string theory takes a different tack string theory says look let me just look at the quantum mechanical motion of a vibrating string not even thinking about gravity and lo and behold when you look at the quantum mechanical vibrations of a string you find in there Einstein's equations with modifications but in certain contexts those modifications would be small leaving us with Einstein's equations so in loop quantum gravity you basically start with Einstein's equations and apply a quantization procedure to go from the classical theory to the quantum theory in string theory you start with a string a classical string you quantize it and then you look at the kinds of forces that that vibrating string can transmit and within there you find the force of gravity miraculous so it's a very different approach and which is the right one nobody as of today can really say because neither of these approaches is make contact in a specific way with observations so koala Jeet asks if strings are one-dimensional then how do they vibrate in more than one dimension and this is kind of fun because this is my third note itself that I should do an episode on string theory I mean it would be kind of weird to conclude your daily equation without having any mention of string theory in the more formal versions of the episodes so just to refresh my own mind I don't want I want to do on extra dimensions I want to do one on string theory I want to do impossible interpretation of quantum mechanics so just to reiterate to myself but back to your question koala Jeet when we say that a string is one-dimensional what we mean is that if you were say an ant on that string did only be one direction in which you could walk you could go forward or backward but there's only one independent direction in which you could move but that is intrinsic to the string itself the string can be embedded in a higher dimensional space and therefore the motion of the string can make use of all of the dimensions of the ambient environment even though intrinsically along the string itself there's only one dimension in which that ant could move so that's the difference you need to distinguish between the intrinsic dimension associated to an object which is a dimension that spans the physical extent of the object itself or the string the span is only in one dimension versus the ambient environment within which that object is embedded and that in bate and that ambe the vironment can have more dimensions than the object itself this happens all the time right so you could have a flat piece of paper embedded in a three-dimensional world of course the paper can ripple or flag right a flag if it's infinitely thin it's got two dimensions on the surface of the flag but you put that flag up a flagpole the flag is embedded in three-dimensional space and then the wind blows the flag is moving it's vibrating in the three-dimensional environment within which it is embedded even though the flag itself only has two dimensions intrinsically on its surface that is the difference between these two ideas okay Siavash asks do you think AI will help us understand the universe or will it end us well it could easily be both I think I may have mentioned in the last episode but I do get my live sessions and mine on live sessions and interviews and other conversations that I have sometimes mixed up so sorry if I'm repeating myself but not everybody who was at here now was at my other daily equation say last time around so so there our AI researchers who came from the world of physics who are incredibly optimistic that we will use AI to solve problems in physics that the patterns that we need to recognize in the external world and the mathematical embodiment of those patterns we will find AI systems that are better able to spot those patterns and better able to find the mathematical framework for understanding them so hasn't happened yet but when I listen to them speak I do find it at least exciting and possibly even convincing that's a really good shot that AI will assist us in taking the next step in perhaps the not-too-distant future at the same time that's not in contradiction with the possibility that a Iong as you note in your question could be the end of us I mean a eyes goals need not align with human goals I mean we certainly hope that they will will try to program things that that happens but the whole point of of general artificial intelligence is that there is a freedom and flexibility in the kinds of ideas and insights that run through the AI system and who's to say that those ideas insides goals will align with ours moreover how do we know that they won't be detrimental to us or ours and you know they've been doomsday scenarios that people have written down you know I I think I saw I know where it was you've probably seen it maybe was in New Yorker cartoon or something and maybe wasn't a cartoon I don't know but I saw this image where you know he had some AI system that was charged with making more efficiently paperclips many cartoons he probably seen it is you know this system became so efficient at making paper clips that basically extracted all resources in the environment and filled the earth with paper clips making it uninhabitable so it was very effective in cheating its goal not so effective at achieving or preserving our goal so I can certainly imagine some catastrophe like that happening obviously everybody will do all they can to avoid that okay so fabulous Ali asked how was your experience on the set of The Big Bang Theory non-scientific question sort of fun to answer those sometimes it was great it was great fun a long time ago it was when it was when my next to last book came out yes that must have been 2011 oh my god that long ago I guess and I was on a book tour I'm the producers of the creators of Big Bang Theory I don't know they must have seen me on a book show or something and they said how would you like to do a book signing on national television on Big Bang Theory because their idea was I'd be on the show and Sheldon and it's a name Amy I always get mixed up with the glasses the scientists counterpart to Sheldon they would be at your book signing and riffing in the back of the bookstore that was the conceit of the piece so I said to them well let me think about whether I want to do a book talk book signing on national television on the number-one rated television let me think about yes I do want to do that and so I I went and they had actually scripted it for me but I said to them much better unscripted I got the gist of where they wanted to go with Heisenberg and uncertainty I said look let me just let me just talk as I would at a real book signing it'll be more natural to be more real nerfect fine so I just sort of did that I just kind of talked at the front of the room and Sheldon and if her name is Amy sorry in the back I mean Maya is real know what's around there Mayim I think so I'm really I'm hearing I I need help when it comes to names obviously but anyway so they were in the back of the bookstore set chatting away and making wisecracks and jokes and I said I tell you so one funny thing and then I'll move on back to science because of scheduling we didn't shoot that in front of a studio audience and everything they do when it was still in the air is shot in from a studio audience and they only use things that get a good laugh so after this day of shooting they said to me we're gonna show this segment tomorrow in front of our live studio audience and we'll record them and if they laugh we'll keep it in the program but they don't have we won't they oh goodness gracious and thankfully they laughed and so it was kept in the show which is sort of fun and it's also a funny thing from the perspective of you know I've done I'm not that a lot of TV I've done a fair bit of television you know I had seven hours of documentaries on nova elegant universe fabric of cosmos had a 90-minute documentary last year light falls that I've mentioned here from time to time and you know I've been on interviewed in a lot of shows and so forth over the years but none of that has any impact compared to the impact of 90 seconds on Big Bang Theory number of times that people ask me about that to wharfs the number of times that people ask me about elegant universe and fabric of the cosmos I was just interesting the power the power of popular culture all right so moving on from there I saw some kind of Columbia question but I can't it went by too fast and I don't know where it went Erik Dobie says her name is blossom blossom I don't actually watch Big Bang Theory but blossom doesn't sound right that's not who I have in mind awesome who's blossom everyone's like oh it doesn't have a blossom this time I know what you're talking about bill Hussam now I'm talking about she's like a scientist in the show she a scientist in real life she was a PhD in in neuro science I believe by though I can't remember it's it not Amy someone tell me it's not her name in the show consumer I think it is I think it is I'm gonna assume that it is all right so Abdullah TV says I have a theory and I want to share it with you where can I do that and how do I answer this question and it is a good question to address the number of theories that I'm sent is far greater than the number of theories that I can possibly look through in a lifetime and it makes me feel bad because people work very hard on these ideas and they put their heart and soul into some of the papers that they write but it is simply impossible for me to read through them and I don't know what to say about that you know I wish there was some way in which all the interesting theory is that people in the general public come up with that they could be vetted in some way maybe there's like some public crowd-sourced website that we could create in which the various theories that people come up with could at least be looked at I mean how sad is it to work hard on something for years I've gotten letters from people who've been working on theories for 20 or 25 years and no one's ever looked at these theories and they send them to me off his thick stacks and I look at them and like oh my god it's gonna take me like months to read through this and and I don't have great confidence maybe I don't want this to sound come off sounding wrong but I don't have great confidence that with our present state of understanding that someone can sort of leap to the frontier without having a full grounding and all the physics that came before I think many people have in mind the image of Einstein in the Patent Office the outsider but bear in mind Einstein had a PhD in physics it wasn't Einstein was just sort of some guy in the patent office he was number one you know kind of the most brilliant scientific think of the world has ever known but put that to the side but he had training yet training in math he had training in physics he was therefore well equipped especially at a time when insights into certain key ideas had were in their infancy but right now maybe there are other ideas that are would be in their infancy if we were to come up with them but right now general tivity is such a mature subject quantum mechanics is a mature subject if you want to push the boundary of generality in quantum mechanics you've got to know the state of the art in these subjects and oftentimes what people are sending me is something that's meant to push quantum mechanics forward push general relativity forward push unification forward and I look at the papers and the first paragraph I don't recognize any of the things that we hold to be true so that diminishes my confidence that that theory is actually going to be right so the answer to your question abilities I don't know don't send it to me I mean I don't mean to be mean but if you send it to me I know I'm not gonna read it so I don't want you to take the trouble to send it to me but I wish I you know in the best of all worlds you send it to a journal and the journal usually does make a quick assessment as to whether that paper will go into the review process so that's certainly an option available to or posted I know there are these various physics what are they called chat rooms nots an old word no there's a more modern murdered for it bulletin boards no there's some word but you know what I'm saying this place is where people get together and discuss physics maybe there's somebody there would take a look but I apologize for just not having the time to go through everybody's here maybe somebody has the answer and I'm missing it by not reading it so that is the the risk that I take okay [Music] what do we got here quantum jumps from Austin Texas questions was your opinion of Colombia move guess impact partway through the question I have to keep going Columbia Professor Peter White's blog criticisms from not even wrong look I've known Peter white since I was a graduate student at Harvard yeah yeah I went to give a talk at Stony Brook in 1987 or so 1987 a long time ago and Peter white was a postdoc there I think and and we met and we had great conversations and and I have you know I think Peter is fundamentally a good person and his heart is in the right place of trying to bring ideas to the public to try to minimize the hype that sometimes does happen out there in the world I mean I think sometimes it's probably accused me of hype and that actually strikes me in a deep place I mean you gain a thick skin after a while when you're out there in public and at one level or another but I do all I can really not to hype the public I really do I'm very sensitive to qualifying radical sounding statements when I talk about the multiverse inevitably I say these are hypothetical ideas that emerge from the mathematics we don't know if these ideas are correct from string theory when I talk about it I inevitably emphasize that we don't know if these theories are correct because we haven't connected them with observation experiment so and I don't do that for Peter I do it for me I do it because it's part of my DNA that I want to be out there speaking in a way that people can trust I've turned down being on major television interview programs because the topic wasn't something I felt I had any expertise in and I don't want to be out there just spouting hot air so so so I think it's important to have someone policing if you will or indicating when science is described with unnecessary hyperbole unnecessary hype if you will so so I get it and I think that's fine it is good I do think that Peter becomes unnecessarily negative sometimes on ideas at the forefront that we know are speculative but nevertheless the mathematics is to us so interesting and compelling that we're willing to spend some time on it so you know IIIi think what he's doing is fine and people enjoyed and learned something from his blog fantastic that people get excited about science and it reorients their thinking about what aspects of recent work are worthy of attention and which aren't fine but I do think you need to listen to a spectrum of people a spectrum of people that you can trust and I hope that these sessions have given you confidence that I'm one of those trustworthy individuals who really does put effort in to giving answers that are sufficiently qualified and sufficiently aware of the ways in which other outlets may promote unnecessarily certain far-out ideas that really don't hold any water I mean that's why for instance in the last one of these live sessions I think I began by talking about these headlines talking about NASA finds evidence of a parallel universe in which time elapses in the reverse direction so I go my god really again it's not that that isn't an idea that was put forward by some scientists but it's put forward as just one of a collection of ideas many of which are much less far-out and I think it's unlikely that that far out explanation will explain the data of the cosmic rays being found in Antarctica so it's unfortunate that those kind of over-the-top suggestions which are put forward by well-meaning scientists no one's trying to mislead the public that's not our goal but in the hands of journalists sometimes things get hyped in a way that can be misleading so anything that helps pull that back ultimately I think is a it's a good thing okay Danny Elma Cowie asks does the fact that a scientific theory makes correct predictions necessarily mean it is true would it be accurate to say that Newtonian physics is false but still makes good predictions so to the first question know what John I just sorry about that I was not different my microphone it is not the case that a theory that has a history of making highly accurate predictions is necessarily true by any means right I mean the theory can make accurate predictions for experiments number one through experiment a million and then on experiment a million and one all of a sudden you're like we have a crack in the foundation the prediction of our tested theory is disagreeing with observation so all theories are provisional right it's it's virtually impossible to prove a theory all you can ever do is increase your confidence in the veracity the truthfulness the relevance of that theory by testing it in as many distinct contexts as you can and so you know Newton's theory was tested and a great many experiments between the late 1600s and say the early 1900s and it worked but then Einstein revealed that if you would have tested Newton's theory in environments excuse me where the speeds involved were enormous it would not work and the special theory of relativity supplanted Newton's in that case but exactly as you're saying Danny we still use Newton's theory from a practical standpoint if you want to calculate the trajectory of a baseball flying from a home plate to the outfield if you want to calculate the trajectory of a rocket going to the moon the Newtonian description is so fantastically accurate even if it has been superseded by the quantum mechanical on the Einsteinian view of the world those theories only yield the mo modest modification to the Newtonian prediction in everyday situations and so it is accurate to say that Newtonian physics is in some sense false but still makes good predictions in fact the way I really like to say it is not exactly in that language I like to say that Newtonian physics is accurate in a certain domain of the world when things are not moving too quickly not near the speed of light and when their masses are not so large that the general theory of relativity comes into the picture and so if you want to enlarge the domain and allow yourself to consider very high speeds you better shift your theoretical frame or to special relativity if you want to enlarge that even more to allow for aggregates of matter with the force of gravity is really strong like black holes you need to enhance enlarge your framework to include the general theory of relativity so that's really the way science progresses you have a theory that works in some domain of reality and when you want to expand that domain you need a new theory I mean I want to expand that domain you need a new theory still will that ever stop will we ever have a theory that just works in any domain that you could possibly imagine maybe that is string theory it could be maybe not again we don't know if the theory is right it hasn't made contact with observation or experiments in a way that allows us to adjudicate to distinguish it in a manner where we can say that's the theory that's describing the world but that is the way physics progresses okay let's see what else do we have here actually what time is it oh it's a quarter to five all right let's uh let's just answer a few more questions today so this is a question that seems to come up on it on occasion maybe mr. castle asked it last week I just I don't remember things well enough but our brain thoughts quantum processes so if if if if mr. castle is asking this a second time sorry for answering the second time but at least I'll remember for the third time so our brain thoughts quantum processes of course their quantum processes are they due to the physical motion of the particles are they due to the physical development of the fields that are existing within the architecture of the brain absolutely I don't think that consciousness and thoughts are anything more than that are the mathematical description of the forces at play for the motion of particles and fields regardless of it's a brain or a piece of Swiss cheese are those laws quantum mechanical of course they are so in that sense I would say the answer is both yes and no I don't think and I could be wrong on this maybe future discoveries will reveal some iconic quantum quality that is the essence of consciousness maybe but without that I would say that a brain processes internally that are quantum-mechanical and a block of Swiss cheese involves internal processes that are quantum mechanical because everything is quantum mechanical the real question is is there some iconic feature of quantum mechanics like quantum entanglement or something like that that's at the essence of physical processes feeling the way they do to us human beings feeling like grief or joy or excitement or boredom as the case may be and that's a question that I can't answer my suspicion is that it's not intrinsically quantum mechanical in some fundamental way that distinguishes the processes inside a brain from those of a block of Swiss cheese but we will see going forward if that perspective continues to be viable Maddy Ann says the best theories are those we can quickly disprove they allow us to learn and move on well yeah sure in the best of all worlds and the best of all worlds that excuse me and the best of all worlds you're right Maddy if every time we came up with an interesting idea we could put it out there and there was a machine that could just test it disprove it say allowing us to throw that away and move on that would be the best and frankly we could do that today with string theory if we could find any means of proving string theory wrong I would be thrilled to bits and I'm not joking when I say that I'm not I'm not wedded to string theory I've enjoyed working on it the math has been incredibly exciting the math has forced me to learn and expand my own knowledge in what for me have been gratifying ways I've been fortunate on occasion to work on questions that were ready to be cracked and was able to contribute insights that people found valuable that always makes you feel good but I'm not wedded to any particular theory I am enamored with the possibility that our generation will take us one step closer to the truth but there were many ways to take that one step and as you point out Maddie one way is to rule out theories that are wrong because then it focuses your attention hopefully on theories that have this chance of being right but the thing that you need to bear in mind maddie is just because a theory is so rich and complex and just because a theory shows its true colors in domains that are so small or so energetic that they're beyond the reach of today's equipment that shouldn't be taken as a black mark against that theory no it should be taken as a recognition of the state of play and so because string theory is difficult to test because it does really reveal itself on a short distance scales and high energies that are beyond the reach of at least today's equipment that's not a reason to say that the theory is not worthwhile it's simply a reason to recognize that it's gonna be hard to come to a determination of whether string theory is right and wrong and notwithstanding people like Peter Hoyt saying that string theory qualifies for Wolfgang Pauli statement not even wrong that to me feels very counterproductive that kind of harping from the sidelines feels very counterproductive to me if it was me harping from the sidelines on string theory I'd rather be spending my time trying to prove string theory wrong or maybe even trying to prove it right they're trying to contribute something to the theory of trying to take a different direction entirely and say aha this is the way to quantum gravity to simply say that a theory like string theory is not even wrong it's so unnecessarily negative it doesn't accomplish anything because we who are in the forefront of string theory itself we readily say that this theory is hard to test that we've yet to test it we'll have yet to find direct observational signature of the theory and we keep that in the forefront of our thinking because it keeps us on the lookout for indirect ways that we might make contact between strengths you're in observation so you don't throw away a theory because it takes a while for it to be tested that's just I would say not a good means of adjudicating between worthwhile theories and theories that are not worthwhile yeah so Jacob boon er said yes that is paulie's phrase it absolutely is paulie's phrase and you know Pauli was a famously caustic physicist who had a very sharp intellect sharp insight and look if you take it in good fun if you take not even wrong in good fun sure yeah that's the way things are at the moment we just don't know but I would say that many theories in the stage of development I don't must say that every theory in the stage of a develop if you're pushing the frontier of understanding then you are in a domain of not knowing whether your theory is right or wrong and that domain of development can stretch on for decades if a theory sufficiently rich and interesting that progress can be made even though the theory is yet to be tested so that is just the way things are currently with string theory yes a quantum jump says it's easy to criticize is difficult to provide an alternative and and I agree it's you know that's a quicker way of saying what I was saying just a moment to go if you're gonna spend time an effort criticizing a theory that's one way look life is short life is short so you have to ask yourself why would someone spend their time criticizing a theory spending their time trying to develop a theory how much more exciting how much more useful how much more impactful to come up with new real ideas that push the frontier of understanding forward as opposed to standing on the sidelines and saying II mm-hmm mmm people make their own choices how to spend their time I have an outlook I like to think that I'm optimistic and positive and certainly I spend my time trying to push understanding forward trying to bring understanding to a wide audience that might allow others in the group to push understanding forward and to me it's just so much more exciting your life is more exciting when you're developing new ideas then when you're sitting on the sidelines writing a blog that's critical I don't know Oh to each his own Paul see your book really is good by the way thank you I appreciate that so si monster from last week was asking what is gauge symmetry and I think I promised oh goodness I promised I'd answer what is gauge symmetry this week and I don't feel unprepared good answer to that I know I've I promised for next week si Mon so I must start it's this hard question what is gates him and let me just point out in the elegant universe in Chapter it must be must be Chapter seven I think I take against image I tried to describe it in general terms I'll go back and reread what I wrote there 20 years ago it was hard then it's only it's just as hard now but let me just try to come up with something that will satisfy you si monster I apologize okay what do we got well I haven't looked over at the Twitter stuff in a while let's see if we got here let's see anything that strikes me some Morgan wex hland wassailing asks if time moves differently relative to math but I think that means if mass itself can impact the passage of time which it does and the universe can have more mass here or there at a different moment in time could our perception of time be skewed because of that and and the answer is absolutely yes if a civilization was born and existed hovering in ship at the edge of a black hole then time as it elapses for those individuals would be quite different from time as it elapses for us so as we look at them we would say their clocks are ticking off much slower than our clocks in this environment here on earth far away from say that black hole and therefore their perception of the universe would be skewed in the temporal aspect by virtue of the environment that they inhabit now you might say then ok then like who's right and I say well no one's really right it's just that time is not universal in the way that Newton described it time is very much I hate to say it sounds hackneyed that's in the eye of the beholder in the sense that time elapses at different rates for different observers moving in different ways and in the question of Morgan experiencing different gravitational fields so what makes us think that there is any sense to a statement like the universe is 13.8 billion years old what does that mean if in different environments the different amounts of mass happen to be different motion clocks tick off time at different rates what do we mean by this seemingly Universal cosmic statement about the age of the universe and the answer to that is this we live in a very special universe we live in a universe which is highly homogeneous and highly ossetra isotropic not isotropic isotropic what I mean by that is that let me just talk loosely if you take a chunk of the universe I don't know it's got to be pretty big call it a hundred million light-years across like a big chunk of the universe every hundred million light your tongue of the universe if you average out over the mass and if you average out over the variations in temperature and so forth if you average all those physical qualities in that big chunk of the universe then every hundred million light years basically the same as every other hundred million light years of the universe that's what I mean by homogeneous you know the example that i that i use i don't have my murky or gray water here any longer but you know you think of a cup of coffee macroscopically it looks like a uniform brown liquid let's say you've got some milk in their uniform brown liquid but you know if you dive into the coffee you examine it on sufficiently small scales it's not homogeneous on small scales water over here milk molecule over here sugar molecule over here whatever it's got all sorts of stuff all over the place it's only when you average out over the entire cup of coffee that it looks like uniform brown sludge similarly the universe certainly has differences from place to place you could be near a black hole or you could be near a plan or you could be an emptiness of space but if you average all of the matter in a big enough chunk and average out all the temperature make big enough chunk then like the coffee which looks like uniform brown sludge the universe looks like uniform visible properties and so if you use a clock that is sensitive to those average uniform properties in a given 100 million light years the universe then all clocks of that sort will have experienced more or less the same physical environment and conditions and evolution since the Big Bang and that's the kind of clock that we use when we talk about say a universal notion like the age of the universe so yes at the level of the individual the matter in your environment can absolutely skew your temporal perspective on reality but we in order to remove that very individualistic quality of time when we talk about cosmic time we're talking about time measured on clocks sensitive to the overall average features of the physical universe and because the universe is homogeneous those physical features from place-to-place on average are more or less the same therefore clocks tick off time at more or less the same rate important very important idea very important question all right what do we five o'clock guys should we wrap it up for today I'm starting to feel a little bit exhausted and hungry myself but let me just see if there are any other questions that catch my eye before we do that well Ian Richard grad well asks maybe we perceive one linear hour of time because we perceive only three dimensions of space plus one of time what would happen to our perception of motion in trajectories and so on if we were perceiving not just three but five or more dimensions and if so Ian my answer to that question is if we had more space dimensions that we were sensitive to I don't think that that would give us much insight into the arrow of time in a universe that has a plurality of spatial dimensions like three that doesn't give us any particular insight into the hour of time and so if we had one more dimension of space or two more whatever I don't think that the insight that we would gain from picturing reality with those extra dimensions would really help us at all with the arrow of time others have suggested something similar to what you suggest in though which is even yet more radical people have suggested maybe if there are more than one dimension if there is more than one dimension of time if there are two dimensions of time could there be some kind of symmetry between past and future among these multiple time dimensions and I don't know people have tried to work out the mathematics of a multi time universe it seems as though in some versions you can make some sense of the universe with two dimensions of time it's never really caught the physics world by storm so nothing that I've ever seen has provided me an aha moment imagining a world with more than one time dimension but who knows maybe in the future that someone will develop something in there that is insightful but I've never I've never seen it at least not as of today so Andre Veltman says enjoying your equations in the Netherlands daily almost the only they were daily for a while now I think it's really two or three a week including this live session I think it's probably the rhythm that we will get into I think I will try to have one for Monday and I think I will focus on extra dimensions since a lot of people are asking about that but Andre Development asks how can a quantum bit be of any use in spending my PhD in electrical engineering I fail to understand the details and well I don't know if my answer is gonna help Andre it's probably a description that you've heard in one form or another but I'll say it anyway just in case it is useful to you or to anybody else listening we all know that computers are based on an architecture in which you have bits binary digits that can be 0 or 1 plus or minus whatever and that's a very computationally useful way of breaking down interesting questions they string problems to frame them in terms that only require us to process zeros or ones that are moving through various integrated circuits and the idea of a quantum bit a qubit is to make use of the fact that in quantum mechanics sure you can have say spin up or spin down that's like a 0 or a 1 but the quantum mechanical wave function allows for the weirdness of superposing and up and down and you can't really think about that as going off at a diagonal pictorially I guess you can but it's really that we can have a bit that simultaneously has a little part of 0 and a little part of 1 simultaneously so in some sense if you have a collection of qubits you're able to do a whole variety of computation simultaneously because those qubits can embody both the 0 state and the 1 state simultaneously and if you want to think in what I would say is unnecessarily speculative language but I think it's useful and some of my colleagues do not think this is speculative all they think this is how quantum mechanics works but if they use the so called many-worlds interpretation of quantum mechanics where when something is a mixture of up and down and you go about engaging with it interacting with it according to this view of the world what happens is there's a universe in which it is up and a universe in which it is down so these are not just hypothetical blendings of mutually incompatible realities it's an actual blending of what we would normally in classical language described as mutually incompatible rounds how can we be up and down simultaneously Agins up between a 0 and a 1 simultaneously but if you allow for the quantum flexibility that allows for a blending of up and down or 0 & 1 and if you interpret that in the many-worlds interpretation then in some sense when you're doing a calculation with qubits you're making use of a huge number of parallel universes to carry out the calculations for Wednesday the first bit is up and the second bit is up or a different universe when the first bit is up of the second but is down and so on so using the quantum flexibility of qubits in some sense their ability if you think this way to access many worlds simultaneously to use the computational power of many universes to exponentially speed up the duration for a given calculation and that's what a quantum computer promises us now again in the spirit of not overhyping things although some would say I'm about to under hype quantum computing we know that there are certain kinds of problems that are amenable to algorithms that will leverage the computational power of a quantum computer but it's not like every problem every question that we've ever asked we know how to frame it in a way that will truly make use of the power of quantum computation and so it's not like once we have quantum computers every calculation speeds up exponentially that's not guaranteed by any means the only thing that we're certain about is that those computations for which we have already developed a quantum algorithm for enacting that computation then those will be sped up enormous Lee but it could be the case that there are a limited number of problems which quantum computers will give you that kick and maybe these are the most important questions the ones the most interest whatever so I'm not going to value judge it but it's just to say that don't immediately think that quantum computation universally speeds up all calculations exponentially that requires finding the algorithms that will do that well I've got an interesting do you see this beam of light that's kind of going through my head right now well kind of dramatic what does that mean is that like is that the alien ship the UFO booming beaming in I should say on our conversation trying to distract us I think not but there it is area 51 shining a ray of light through the Catskill Mountains in New York I like this one Alice Alice vache yes sir have you any life advice to offer us I've no doubt you much wisdom to offer many thanks Alice well I like to think that I've got some advice I don't know if it's great wisdom but you know I certainly to young scientists I would say that the most important thing in early stage is not to be at the frontier of knowledge the most important thing is not to spend three hours talking with me about critical questions at the forefront of string theory of quantum mechanics the most important thing is to learn the basics inside out and sure you can spare three hours a week to do something like this that's really not what I was meaning as the number of people listening dropped off by 50% when I said then what I really mean is that it's so important that you learn the groundwork that one day you will use if you go on in science because nothing is more valuable than the foundation upon which you can build insights at the forefront but without the foundation you will constantly find yourself collapsing through rotted floor boards unstable joists in your understanding and it's best to get that solid now at the learning stage not try to fill that in later on I guess vice vice number two I would give with someone gave me a long time ago when you come to do your PhD those are a little more advanced I'd say don't view your PhD is the best work of your life do your PhD is an important stepping stone to get you into the community of researchers to get you out of school and into the realm of full-time research because there are many people who spend an inordinate amount of time on their PhD thinking that this is a defining moment in their career it's not for most people I mean for a few it is but for most people their PhD is a necessary step and route to the important discovery that they will subsequently make again there are exceptions to all of this but I wouldn't allow an unnecessary focus on achievement in your PhD to slow you down get it done get the PhD done get out into the world get a postdoc job get into full-time research focus your attention fully at that point and don't unnecessary reading that PhD six okay don't go more than six five that's even better for better still which I took got done two years two years I just wanted to get it done then I was out in the world doing stuff so that would be one piece of us again Alice I'm not sure with which side of the academic or non-academic world you approach that question from but at least for the academic side of things those are pieces of advice that I do feel strongly about because a they helped me and B I've seen them in action so many times so I wants me to be the PhD advisor to his or her or their PhD thesis maybe gotta come to Columbia though for that where'd that question go I've got to keep my fingers off of this thing Randi lemundo says maybe great life advice could be to find some talented physics student and fund them well yeah I mean funding it I mean you hat you end it with lol but yeah I mean funding is a big deal and it's become ever more difficult you know the Department of Energy for instance is cutting funding in subsequent years with all that's going on in the world and the funding directly affects the number of students that we can support the number of PhDs that will be granted the number of new able smart energetic physicists that will enter the field so rather than looking to government I think we may at least the United States need to look to philanthropy you know think about the people who got trained in physics and went on or mathematics and went on to make billions of dollars you know great example is Jim Simons as you may know who incredibly successful in the financial world who was a mathematics professor before he made that move into finance and now he's using his money to do the most wonderful things supporting postdoctoral fellows around the country supporting for instance the World Science Festival the support that the Simons Foundation Jim and Marilyn Simons provide also providing support for faculty who are going on leave to pursue research so more the more people who would do that the better off the field would be so that is actually a vital part of from a student perspective of what the future will be like so Joel Jarvan n asks hi Brian thanks for the PhD advice you're welcome gonna keep that in mind I hope you do anyway could you elaborate on the concept of speed and time what unit do we use seconds per what yeah exactly so what I really have in mind when I talk about speed through time is the more general idea of speed through space-time and you may know again I'm not sure what your background is but in the special theory of relativity there is a natural notion of speed through space-time that comes from the for vector DX alpha D tau and that for vector has length in the Minkowski metric that is a magnitude equal to 1 so when I taught him 1 is where the speed of light is equal to 1 so when I talk about speed through space-time being one in equations that's really what I have in mind that the X alpha D tau contracted with the X alpha D tau with the Minkowski metric ada alpha beta gives you a number whose magnitude is equal to 1 what do I mean in more general language the more general language is that when you're sitting still you not moving through space but you do have motion through time and you really can think about that if you want as one second per second you might say oh that's kind of a silly idea but it's not that silly when you think about it because if you allow for that notion of one second per second then when you start getting up to move the rate of ticking on your clock from my perspective won't be one second per second it'll be a number that's less than one second per second because I see your clock taking off time slowly so what I'm really talking about is it's the rate of your motion through time compared to the rate of my motion through time and when we are mutually at rest then our passage through time is the same 1 second per second but as you get up and start to move through space your speed through time slows in the sense that the ticking of your clock is less than one second per second as I'm watching it go tick-tock and I'm watching mine go tick-tock yours is tick-tocking less frequently than mine and that's the sense in which I can say your speed through time is seven seconds per second or 1/2 a second per second your clock is only ticking one half a second while mine is taking off time one second so it's a very concrete operational definition of your speed through time it's the measure of your passing through time compared to my passes through time okay so eat m79 says my video and my sound are not in sync anymore that is a relativistic effect that happens when my thoughts are near the speed of light there is a disjuncture between my visual and my audio when my thoughts are that fast so I will try to slow my thoughts down to try to bring synchronization between my audio and my video I think I may have accomplished it by now but it could also be an internet slowdown okay so Joel gets back oh I see thank you that clears things up a lot actually great I'm glad in fact I'd love to hear a little bit of feedback so I know whether what I'm saying is getting across at all oh it isn't sync for Thomas and others good all right I'm glad glad to hear that all right maybe one or two more questions and then we will call it a Friday day out here which those of you I mean how many of you is it like early morning anybody it's like two o'clock in the morning or something I know that occurs for some of the regulars on this yeah so koala g wants to know about our general relativity course I don't know I don't know I'd love to create a general relativity course for world science U but um it's so time-consuming to create but I was thinking maybe this is a way to think about it quality maybe instead of putting out a full general relativity course maybe I just said as a goal to get out like the first five modules of a general relativity course put that out there and then sometime later to the next modules I don't know maybe maybe I can break one course up into ten courses and do parts one through part ten maybe that will be less intimidating so it's almost 3:00 a.m. for our young it's 11 p.m. in Sweden Joe where are you in Sweden I have a warm spot for Sweden quantum jumps can't wait for a talk on dimensions what math will you use oh well I'm not going to do heavy-duty math I was thinking of just doing an explanation of you know the very basic distinction between 0 1 2 3 & 4 dimensions just using hypercubes tesseracts as the operative example that's sort of what I had in mind and I also you know we have a VR project I don't know how many of you have VR equipment at home or have access to VR equipment I don't know if you have that I wouldn't mind hearing you just sort of note it in the chat because we have this VR lecture that we're developing we did it once but now we're redeveloping it even a more refined way in which if you have VR equipment I think you need an HCC vibe or something like that using that you'll be able to join me in a futuristic lecture theater floating in outer space and I'll explain the basics idea of string theory in that VR environment and we will also be able to build in virtual reality tesseract hypercubes in in four or five or six dimensions so if you have the equipment that is the coolest way to experience some of these ideas so I'll maybe in the link for your daily equation when I talk about the extra dimensions I'll have a sign up place for those of you who happen to have the equipment or access to it so you can you can join in on that and that's sort of the best way to experience this stuff but I don't intend to really do a higher dimensional romani and curvature and things like that I think it'll just take us too much into the technical details of higher dimensional spaces that won't be as interesting to the people who typically watch your daily equation morano's l just asked one little question toward the end here is there a god I don't know I don't know Murat what do you think all I can say is that if there is a God God's been doing a pretty good job of staying behind the scenes recently God's been doing a pretty good job of allowing lunacy to hold sway in America you know it's the old problem of evil that the philosopher is debated across the ages if there is a good all loving God wise or evil in the world and you know there are many answers I'm sure you familiar with them the idea that God creates some life form and then allows that life form autonomy and only by allowing that life form autonomy can the good acts of that life form really have meaning but the capacity to do good comes with it the capacity to do evil I don't know I'm not really all convinced by this kind of stuff but if you ask me my gut feeling my gut feeling is sure there could be a God behind it all set it all in motion and all we're doing is figuring out God's handiwork possible I don't see any evidence for that whatsoever but that doesn't mean it's not true on the other hand if all that we physicists are doing is working out the underlying laws and there is no God and what we're figuring out of the mathematical patterns that govern reality if that's what we're doing not revealing God's handiwork but just revealing the patterns that for some reason or woven into the texture of reality I'm quite excited to be part of either of those journeys if what we're doing is revealing the truth that God put into place Wow what a noble way to spend your time if what we're doing is just working out the patterns articulated in the human language of mathematics wow what a noble way to spend your time so in a real concrete sense it doesn't affect my day-to-day work whether there is a God behind it all but for other questions for many people questions of value and meaning are intimately connected with the potential existence of a god from my own perspective I like to flip it around a little bit I don't I don't view the journey toward those insights that for some people not all but for some people that religion helps reveal I consider those journeys not to understand the external reality but rather to understand the internal reality of conscious awareness the internal subjectivity of what it means to be a life form a human being living in this universe and that journey to understand our own conscious awareness to try to understand why we behave the way that we do why we have the feelings that we do to try to under the understand the truths that are not amenable to description and ordinary language the kinds of truths that would be diminished by trying to describe them in ordinary language the truths that we can sense and feel but we can't quite articulate for some people that's what the spiritual journey is all about and I consider that to be a valuable journey I consider that to be a complimentary journey to the one that we physicists try to reveal in the equations describing an object of world so that doesn't necessarily mean that the journeys toward a god in any conventional sense one of the dominant world religions rather I see it as a spiritual journey that recognizes that there's more to the world than the objective truths that are available to everybody who studies the universe with adequate intensity the subjective truths that are only true for you or only true for me those are not available to everybody they're only available to the individual and you can do your best to explain them if you want if you're motivated but ultimately they are deeply personal qualities of your peculiar combination of particles that defines you as an individual being in this reality and I think that the journey to understand yourself in that way is a valuable one and I consider that spiritual some would say it's religious but clearly the language and the approach that I'm describing is not fully aligned with any of the more conventional world religions so its oblique to perhaps what you had in mind more at when you're asked is here at God but nevertheless I hope that gives a sense of how I organize my own thinking about the qualities of the world that matter all right so rubber jjigae Nome Nome says I think it is a bad idea to call subjective stuff quote someone's truth plenty of good names for those things and I'd be interested to know what you mean by that rubber genome rubber genome because I really am using that language with forethought and it for me at least it does capture in language as best as I'm able to the ideas that I'm trying to communicate which is there really are to me qualities of the world qualities of being alive that are deeply personal and deeply iconic it's not that others don't have similar feelings that's not what I'm trying to say but they're not things that I need to be verified through observation or experiment they're not things that I need to have a mathematical equation in order to feel that I've grasped you know when I'm listening to a great piece of music you know the Goldberg Variations Goldberg Variations number 25 Wow when you listen to listen to Glenn Gould version of Goldberg Variations number 25 and the feelings that that can inspire I don't know the words to describe them but I can't help but describe them with the word truth and I can't help but put the word subjective in front of it because you know it's a truth that's emerging not from some objective analysis of say the electrons magnetic moment but rather a subjective feeling that I don't even care if I'm able to describe to the object of world with any degree of accuracy I know it's true I can feel it it's a quality of the world that I deeply value and therefore I tend to use the language subjective truth to describe it so if you have other language that you think is better and works better for you by all means use it really I mean that but for me I have found that notion of subjective truth to be a useful and now I do agree that you can take these notions and twist them in dangerous ways you can start to twist them and talk about alternative facts you say well that's a fact that's true for me but not for you that's not what I'm talking about I'm not talking about qualities of the world that are accessible to all of us I'm not talking about what happened in a conversation between one leader and another I'm not talking about whether the climate is undergoing certain transformations I'm not talking about the objective qualities of the world that in principle are available to all of us if we are privy to the information and if we are privy to the equipment necessary to become aware of that information I'm talking about the deeply personal qualities of existence and there is a pretty clear way to have a demarcation between my use of the word subjective truth and the ridiculous the dangerous the unjustifiable the devious use of terms like alternate facts no connection whatsoever yeah so the Chopin March I agree there there there there are many there are many ways to achieve the kind of experience that I was referring to rubber genome by the way I gotten to strength through research with the elegant universe thank you so much for that so so yes no I wasn't I was in China I hope I hope my little diatribe here was not taken as a critique of what you said at all I'm just giving you my honest reaction to to the comments that I'm reading here so Brad Dibble hi professor Greene Louisville Slugger here by which I suspect Brad is reminding me that he has spoken of the Louisville Slugger that I see currently in the corner of this room how do physicists know that the CMB started 380,000 years after the Big Bang and the answer to that is we have an understanding of how the universe changed in time coming from the equations of the general theory of relativity we have an understanding of the temperatures at which say electrons will be so juiced by the ambient temperature that they will not stick in orbit around protons and it's when electrons are able to stick in orbit around protons that the material in the universe becomes overall neutral positive proton negative electron high enough temperatures they're all floating this way and that and when they're floating this way and that light can't penetrate why light is affected by the electromagnetic force light is the carrier of the electromagnetic force if you've got charged particles around the light gets buffeted to and fro and it can't get through the plasma of particles it becomes opaque only when the protons grab the electrons making neutral atoms can light freely travel because now it's not encountering the charged particles of the plasma and we can work out how long it takes for the universe to cool down after the Big Bang for that so-called recombination that putting together of electrons and protons into neutral atoms how long it will take and it will take about 380,000 years for the universe to settle down into a state where there isn't a plasma of charged particles that prevents the Cosmic Microwave Background photons from traversing through space unimpeded and that's where that number comes from the other thing it comes from is we can measure the degree of redshift this came up early the degree of redshift of photons and the degree of the redshift of the photons gives us an understanding of how long they've been traveling together their cosmological theories we can figure out how long they've been traveling so that's where that's where these numbers come from so so ban so van so I don't think I'm pronouncing that's right so ban Rabbani last night I was watching the episode you talked about the big bang with dr. Tyson Neil Tyson on a star talk show absolutely fantastic thank you it was amazed by the effort you put on string theory all these oh okay that was just a compliment not a question so thank you so van I appreciate that alright anything left to go any time left oh it's 5:30 so I don't know maybe we'll them go for a few more minutes and then wrap it up okay well life and thought always exist in the universe and it's cyclical in the universe cyclical infinite well look if the universe is cyclic expands and contracts expands and contracts then our universe is one episode in that sequence and we have no idea whether life is a natural outcome or a rare outcome and therefore we have no idea whether life will persist in the other cycles we just don't know it's possible you know this interesting work by jeremy england and clappers beck Jeremy's coming out with a book I'm meant to read it I've got to read it really soon I want to give it a it seems like a wonderful book so I want to endorse it but I have to finish the reading of it but Jeremy has these these theories or a theory about life that perhaps suggests that life might be a fairly commonplace outcome of a hot star raining down energy on a planet with certain kinds of complex molecules and you know if that's the case then maybe life is commonplace and maybe indeed life would be commonplace across all the cycles in a cyclical cosmology but there's nothing that establishes that as an absolute truth so who knows maybe that a cyclical universe maybe none of the cycles except ours would support life possible don't know all right I'm gonna look for a final question here and then wrap it up all right I'm gonna end with short cut well psychedelics help us understand consciousness I think the answer to that is yes and I'll tell you why you know one of the most difficult things about understanding consciousness is that we try to understand consciousness with consciousness we try to understand the phenomenon by experiencing the phenomena and that's not to say that researchers careful researchers don't do everything that they can to try to find objective signatures of conscious awareness and they look for correlations within the physical properties of the brain the physical processes in the brain they try to line up certain kinds of qualities of conscious experience with certain kind of physical processes taking place and it brings all this is great but you can't help but wonder about the possibility that if our experience of consciousness is much broader then it would be in the absence of psychedelic experiences that that can't help but broaden our perspective on what consciousness is and what it's capable of and what the phenomenon that we're trying to explain what they actually are and look this is a slippery slope and a dangerous path to walk down because not all psychedelic experiences are benign not all of them are safe so these kinds of explorations need to be done in a safe way and is it controlled away as possible but I am of the opinion that broadly broadening our understanding of the spectrum of conscious experience can only help to provide insight into a consciousness actually is so who knows and again I don't do research on consciousness nor do I take psychedelics so I'm one step removed on both of these fronts so it'd be better for to ask that question from somebody in the trenches who's actually working on consciousness from a scientific perspective and there many researchers who do that but speaking as someone who knows what it takes to make progress on difficult scientific questions I will say that we've always found that when you can broaden your perspective on that issue on that question see it from a variety of different angles bring an unexpected links to other qualities of the world that can sometimes be what it takes to seed a breakthrough and experiences can be one pathway toward that kind of broadening of perspective it cannot be done in a way that is irresponsible it cannot be done in a way that isn't carefully thought-out and controlled but if that is the context in which it takes place then yes I do think psychedelics potentially have something to offer in our understanding of consciousness all right with that I will wrap it up for today as I said I'll try to do a your daily equation for for Monday maybe on extra dimensions we'll certainly meet again next Friday next Friday I think I'm also going to do one of these reddit public access network things from 2 to 3 o'clock one hour before this and that may impact how long I go next week on your day of the equation so if you want to start an hour earlier you can absolutely do that our pan just look it up and other than that I will see you metaphorically on Monday I believe and in this live session one week from today all right thanks for all the questions thanks for hanging out have a good weekend see you then you

Channel: World Science Festival

Views: 203,948

Keywords: brian greene, Live stream, #livestreaming, #livestream, #live, #streaming, Albert Einstein, daily math lesson, Your Daily Equation, brian greene interview, brian greene until the end of time, professor brian greene, astrophysicist brian greene, professor brian greene interview, physicist brian greene, brian greene book, professor brian greene until the end of time, brian greene physics, brian greene joe rogan, brian greene string theory, number theory, daily series, math series

Id: T44nS6xJ1Fc

Length: 157min 41sec (9461 seconds)

Published: Fri Jun 05 2020