prose. >> host: bradley graham is the new code error of the well-known washington independent bookstore politics and prose. good luck to you. booktv look forward to continuing our relationship with you. for a.. .. >> explains how this would change our understanding of reality. >> well, good evening. it is really a special pleasure and honor for me to welcome brian greene to our fair city.

before we start talking about other universes' call by the we start talking about you. i know a lot of people would like to know some personal details about you. i understand your vegan. >> yes. in this universe i am. that's true. >> my next question. a doppelganger as a mediator. >> very observant to think so. according to our understanding, that is quite possible to be. >> i was on-air plan a few days ago coming from london. a woman next to me, i ordered vegetarian. she said, would you be offended if i ate meat. i don't care what you eat. anyway, offended by your dumping a. so,. >> it does not sit next to me on the airplane. it all works out. >> the kind i am thinking, said next year on an airplane. so tell me something else. i understand you have a number.

what is it? >> the error does. >> yes. can you explain? >> yes. this idea of how many degrees of separation you are from tennis people. so the original one was how far away and give an actor was from kevin bacon. then mathematician's wanted to compete and have their own version of kevin bacon which is paul, he collaborated with many mathematicians. the question is, how far you away from having written a paper with him. then people said, let's put it all together and see how far away an individual is from both. [laughter] as you can imagine, there aren't too many people that are close to both, but there are a handful. i am one of them. >> how many are you? >> i used to be the world leader >> what is your number? >> number five. but i've been overtaken.

>> five in what? >> five total. something like that. but i think when that poulter has taken over. >> is that right? >> she wrote a paper. i am not sure. definitely people who have taken over. >> i see. another universe. >> that's always going to be the case. >> so what is this -- let me ask you. there is one universe. how could there be more? >> book, that is the essential question the start with. you know, long time ago, two years ago, the word universe man just what your saying. meant everything, the totality, every star, every galaxy, the whole shebang. what sense could there possibly be in having more than one every think? what we have found in research that actually dates back a number of decades most

vigorously village of the recently is that our mathematical investigations, or suggestions, what we have thought to be everything may actually be a tiny part of a much grander cosmos. that grander cosmos can contain other rounds that seems to of rightly be called universe just as our round has been called universe which means that you have many universes' to multiple universes' which we call the most diverse. >> it sounds like a brand of cereal to me. maltese serial. so tell me. i understand that physics is a science experiment. so where does this come and? it sounds more like a religion. this universe and another universe. how do we learn about these of the universe is? >> yes. how can you gain confidence in an idea? it speaks of rounds that we can

see, we can't touch, weekend visit, we can't observe directly. let me give you the answer in two parts. in some versions of the multi first, and i should answer -- emphasize it is not one proposal. in some there can be subtle connections between the universes'. that might allow us to have some experiment a window. all of that is an aside for the moment. let's think about the ones where you could not visit. why do we think about these things? well, we have a belief founded upon hundreds of years of experience that math can provide a gateway to reality. it can provide a window onto a reality that at the moment it is being done we can't actually see were observed. i mean, einstein is the greatest example. you go down his equations of the general theory of relativity with back in 1915.

others looked at those and found that they seemed to say the universe was expanding einstein himself said, no, i don't actually believe that. twelve years later observations showed the universe is expanding. the math was confirmed by observation. other examples are black holes. again, einstein's matt gives rise. einstein did not believe. observations now show that there are black holes. we are following in the tradition. reacting mathematical equations following them. as we can discuss in some specific cases they are leading us route by a route to the possibility that ours is only one universe. does that mean the map is right? we don't know. it has to be confirmed alternate the through some kind of observation or experiment. the possibility that the map is revealing, this new picture of reality is sufficiently compelling that many physicists by taking it seriously investigating it vigorously. >> but i think the operational

word here was can because mathematics is not physics. >> exactly. >> sometimes the mathematics works and sometimes it doesn't. you don't have to go very far, but if we go back you can say the epicycles were invented by a mathematician, a greek mathematician and then promptly used them to argue that the earth is the center of the solar system with a universe to be here is mathematics. not very complicated mathematics. >> yes. >> it does describe reality. you can go to later on. for example -- >> before you leave that example because i think that is a great example. you have some individuals who were looking at the notion of the earth and the planet and coming to a certain conclusions that we now know to be erroneous. conclusions about how things were working. there were other physicists, mathematicians who looked at that mad and said, this is so

complicated, so convoluted. and if we look at the map this light it all simplifies. but, the conclusion is that the earth is not the center. we were propelled by mathematical investigations. the earth is not the center. and others using similar kinds of reasons know that the sun is actually not the center either. similar mathematical reasoning showed us that our galaxy is not the center. one of many. we have gone through a sequence of cosmic motions by following the map confirming it through observation. we may be on the threshold of the next by following executive the same pattern. and it is not the center, son is not the center, a galaxy is not to the universe may not. maybe one of many following exactly the same pattern. >> but i think the key is that the mathematics is always simpler. >> that is certainly what we have. >> but when you do very complicated mathematics and you trust your equations, often

these equations. >> i can understand where you might come to the conclusion because if we get into the details, some of the most diverse ideas come from a string theory, which seems like a complicated subject when you hear about its features. when you look at the collations the starting point is actually pretty simple. >> how many are there? >> there is one. there was a time when we thought there were a handful of distinct. wonderfully in the past decade the matter has come together to really realized what we thought were different were all the same, just expressed in a slightly different language. everything has been simplified. if you take even a good example, darwinian evolution. the principles of evolution a pretty straightforward. nevertheless, those principles can yield the rich variety of life that we see on a. the outcome can be complicated even though the starting point is simple. that is the way i would characterize our thinking about

certain modern physical theories. the outcome, string theory, if we get into it, extra dimensions, vibrating strings. it seems complicated, but that is the recess of life coming revolution. the setting point of string theory, pretty straightforward. >> i see. so, tell me. what are some of these theories that lead to the motorist? in your book you describe several of them. i could not find the one where the entire universe, that is my favorite into a person, positrons. antiprotons. your favorite route. >> well, there are many ways. maybe a good place to start with the what i consider the simplest of all which is to imagine the possibility the space goes on indefinitely far. if you were to get into a rocket ship and head out into the cosmos with you at some point

hit a brick wall? now, most of us don't think that is the case. with the circle back to your starting point like what would happen on the earth's surface? that is possible. but he simply keep on going forever? we don't know pete let's take that third possibility seriously. if we do there is a startling conclusion that is simply this. in any finite regis based matter can only iran to self in many different configurations. >> a large numbers. similarly like if i take a deck of cards and shuffle the deck in the order that cards differ there are only fiat the different orders. many different orders, but still finite. so if i shuffle the deck enough times, infinitely many times the order of the cards has to repeat. similarly in infinite space the order of the particles, the configuration has to repeat. now, what would that mean? well, it would mean something pretty strange. you and i would just a configuration of particles.

if the configuration of particles repeats someplace out there in the cosmos it means all that we know is repeating. we are out there, and that is a very straightforward mathematical conclusion from the simple starting point. space goes on indefinitely far. >> you're leaving out an important thing. the measure of that is zero. >> it doesn't matter. the probability of us in another universe, do you want to go there? >> absolutely. in fact, frame it in probabilistic terms to be that meet you in a more concrete setting. if i had that deck of cards in the shuffle that over and over again, do you agree it sooner or later the order of the cards will repeat, not the probability. >> and not saying the deck is too large. >> fifty-two cards. >> you are taking the easy way out begun talking about the universe. >> you are discounting the power of infinity. infinite space. this is the supposition. you can challenge that, but

let's not just to get to the end of the argument. if you take on board this idea, which i think most cosmologists and businesses have the space goes on indefinitely far in you got, you've got a lot of room for this to happen. >> i have a problem with an infinitely far. >> that's fine. that is a good place to try to poke a hole. >> in mathematics dimensions kill infinitely far. in physics these three dimensions in which we live in the course of time which is related to the of the three, created in the big bang. so i think if you think of the physics, and to me if i'm wrong, they feel it was created, we are not expanding into another space. we are creating space as we are going out. the galaxies are expanding. we are creating free space. so, where is the of the universe? as the petition, okay.

it goes on forever. call it tax. but i think in one of your universe is, universe here and here and here and here and infinitely many. that's okay, but doesn't really exist from a physical point of view? space and time were created. >> i do need to correct you a little bit. >> sure. that's what i'm here for. [laughter] so there is an incorrect image that many people have in mind which is this. and we think about the big bang typically we think about further and further back in time the entire cosmos was smaller and smaller and smaller. way back toward the beginning the universe, we intuitively think of it as very small and then run that forward. as you are saying, space is created from the big bang. how can it be infinitely been gifted with small in the past? if that was the right picture you would be right, but that was not the picture that is compatible with an infant

universe. in an infinite universe as you had ever further back in time, the universe is still infinitely big. if you go back in time and the universe is half as large as it yesterday, half of an affinity is still infinity. if you go back about one-third of infinity is still infinity. the traditional one. >> the universe is infinite. >> infinitely big. >> of what is the radius of 137 billion years? >> that is the several -- of 0 billion versus. the big bang is an event that gave rise to our rahm, but if the universe is infinite the big in our part, the part that we have access to is only a piece of the entirety. so you need to make -- >> and the others are expanding as well. >> exactly ability to make a distinction between the observable and the entirety. this is just the part that we can see. and you're right. we can't see further back than

roughly 13 billion light years because that is the amount of distance that light can travel since the beginning. almost nobody believes that the universe and this at that point. most everyone believes it goes on at least a far distance beyond that. the supposition of this particular example is that it goes on and had the far. >> you are a magician. you pulled up and finish the out of a hat. having, what does infinity have to do with anything? cost analogy? i mean, to invoke an affinity you have to give me something. >> yes. and the most straightforward definition would be, the same causality as the realigned. the real line extended in exactly the way that you know about from when you took mathematics at a young age. goes on without pounds. let me ask you this. let me turn it around. if the universe is not infinite

the day, what happens when you travel the earth? >> i interviewed steven weinberg a few months ago. i ask tim, the big bang is believed to be a quantum fluctuation. that is what created our universe. what was the constant fluctuation, what was the medium in which we respond to back he said, that, we don't know. we can't go there. we don't know. >> that's right. >> you're telling me something else. there is an infinitude of space. mathematically i agree with you. the reel line exists. exist platonic fleet. >> if you build a space ship and you keep going and what happens? >> if i take physics the way physics has been done, here is the big bang. it started here. there is no location, no meaning. you can't define that point as being located in space because

space doesn't exist before the big bank. i don't know about of the yen versus. so if you start here this space was created with the big bang. >> if you go out to a rocket ship and head into space and keep going, what happens? >> you know this, you can't. >> you have a ship and you go out. the possibility. do you hit an end? the cycle back to your starting point? >> now, you know pretty well. if you in the telescope in this direction in you and the telescope in that direction the two parts, the farthest galaxies you can see to read it receding at a speed faster than light because of the accelerating. you don't even need the acceleration. that part doesn't talk to this part. how would you ever get from this to another? >> if you did in the ship what will happen? >> i don't know. i would be lost in space. [laughter] >> it is a mathematical question.

and meth language, what is the topology, the overall topology? >> that is where i disagree. i think the policy exists in the mathematicians mind as a platonic kind of thing. motives or things that may have nothing to do with the real world. when you as a physicist take parts of mathematics you actually finesse my key point which is mathematics is not physics. >> could. >> a lot of mathematics here does not do anything to be a give you an example. we talked about the epicycles of take years and give you another example. so that actually met. >> yes. fill it up. i want it build up to the same level. so heisenberg was one of the fathers of quantum mechanics. you know, in the '20s he built this theory. everybody knows about the uncertainty principle and the matrix mechanics.

he went a step further. he thought the best going to go into something else. here is a proton. i need three as cubes year. anyway. so the proton and neutron. there is a symmetry between them. a proton and neutron. i'm going to use the mathematical symmetry to explain why these two are so similar. he called it as you to read then we won't go where it went from there, but that section was wrong. that was taking mathematics that makes a lot of sense in your mind as a mathematician but has nothing to do with the real world and the sense of the protons and electrons. they look similar because of nature the mass of small. one of them is a lot heavier than the other in absolute terms, but we compare it to the math of the two. then you think they are really very similar. into century. of course you and i know that he went later.

he did all kinds of things. the mathematics came back, but at that moment what you have is mathematics. yuri powerful and absolutely useless. i rest my case. [laughter] >> but it is a case that i agree with. what i would say is mathematics opens up the realm of possibility. thank you very much. and what the art of physics is, the art of physics is being able to sniff out which mathematics is relevant for reality in which mathematics isn't. now experiment an observation arequipa to the story. ultimately it was. so what we need to do and what we need to spend our professional lives during is trying to understand which body of mathematics is relevant throughout and which isn't. now, in this particular case that we are talking about the argument makes the assumption

that a certain body of mathematics, space can go on infant the far, relevant. if that is not right, and it may not be. on the first to say that it may not be. if it is you come to the startling conclusion. if it's not, then you don't. that is the motive thinking about many of these proposals. many of them start with a certain mathematical framework, puts the matter as far as we can to border of understanding and then use that to look over the horizon and see what's there. are we seeing reality or mathematical ideas? that is a question that has to be confirmed or disputed. let me give you an example. that moat could help us here. could be, perhaps, observational establish that? that would be a nice thing to do. one way to do that is if it does not go on indefinitely far and if it has the shape that the surface of the earth where it comes back on itself, then as

you know, there are structures in space that give off light, galaxies, radiation and so forth. if the universe has the shape but that it hit our i but also passed by s, circle around the universe and come back a second time our third time. so if you can see multiple copies of a given object that would be a nice piece of observational evidence showing that space is. that doesn't mean it and cannot predict could be big. so big that it has time to settle around, but that is exactly what physics is about. during mathematical calculations, pushing to limit and trying to find an observational. >> tell us about some of the specific theories. let's start with the one i dislike the most. >> yes. >> many worlds. >> a different character the proposals for how we can be one of many universes'.

you may note that in the book it is actually one of a later chapters. >> i was worried about that. >> you're right. chronologically. that's right. in thinking about this subject marching through the development chronologically does that give you the most because please sensible way of thinking about where we are today. in particular the many parts of quantum mechanics. it is an interesting proposal, and that's why i have a chapter devoted to it. you're right. it is weird. you know that that in that chapter a basically come to the conclusion that i don't think it works. but that doesn't mean it doesn't. if you talking to other people like david deutsch or various other researchers, david wallace and so forth, they would sit here and sens. i don't want to give the wrong impression. here is the idea. the new idea of quantum

mechanics in the early part of the 20th century was that whereas newton said, tell me how things are today and i will predict how the will be tomorrow. the universe is like a giant clock. out use mathematics to turn the crank forward and predict how things will be. the observations have established that is a very accurate way of did not things when applied to everyday objects or to the men's motion or to rock that you throw in and tells you what happened. you do the observation and tests. and people are being asked to probe the microscopic realm that whole structure begins to fall apart. >> different universe. >> simply different realm. let's not use the word universe into many different ways. a completely different environment. in some ways, why should the laws that work on everyday skills also work on tiny scales? it turns out that they don't. the laws of quantum physics and the idea of quantum physics is

that you can only predict the likelihood, the probability of one outcome or another. so if i'm not dealing with iraq or the moon, but an electron and i want to know where it is the quantum loss say there may be a 50% chance that it is over here and a 50% chance that is over there. >> your 50 percent chance of each, and you can't do any better than that. the weird thing is when you do an observation of the electrons you always find it either here or there. you never find it half year or have there. there is never some melding of the two. so for 80 years even though the probabilities of quantum mechanics are confirmed by doing an experiment over and over again, finding electrons 50 percent of the time here and 50 percent of the time here, how do you go from the fuzzy hazy probabilistic mathematics of quantum theory to the single definite reality that we observe

when we do an experiment? number his answer this question yet. shockingly 2011 and no one has answered this. the proposal that comes in 1957 is this. look, if the map says there is a 50% chance the electorate to be here or here, when you study the matter diligently and relief followed through and apply it to the experiment as well, the math seems to say that when you do the observation you find the electron here. you find the electron here just in two different universes. and each year evers, a copy of your thinking incorrectly that there is a simple definite outcome. from the bird's eye view there are two of you thinking that. that is just a single example with an electron. the idea is that all of the possibilities allowed by quantum lost are realized in one universe or another. this grand collection of possibilities that we call the quantum. that is the idea.

>> you believe. >> i don't believe it because i don't think that we have established yet in any of the analyses, and again, this was controversial. some people think we have. i don't think we have established get out this way of thinking about quantum mechanics actually describes the observations. that link, i don't think, has been established. >> at think we just don't understand quantum mechanics. >> but that is tantamount to exactly the same thing. to understand quantum mechanics is to say how this quantum mechanics link up with observation, and i don't think we have answered that. >> it doesn't appeal to our understanding of the universe because we are living in a space where things don't happen the way they happen in a micro work. the me ask you. that is why -- >> mostly. things like that. sometimes you can see large objects behaving quantum mechanically. very rarely. >> i just want to emphasize, what your saying explains why

can't some account to the quantum mechanics is counterintuitive. >> worse than that. >> whatever word you like. whatever word you like. >> einstein could not accept it. >> exactly right, but why is that? there are two parts to the story. i wasn't actually asking you a question. >> i want to answer it. there is a part of quantum mechanics that feels very uncomfortable because it's so at odds. that is the part that makes it hard to accept these crazy ideas. but if these crazy ideas have been fully worked out mathematically in the link to observation has been made, we would have to except that our intuition has been built up from thousands of years of living in the world besides. there is no evolutionary advantage to understanding the probabilistic notion of an electron. when you are out on the savannah trying to begin next meal it doesn't matter if you understand the privileges of quantum

physics. it understands if you -- it matters if you understand mitannian dynamics. that is why our brains have developed to really be newtonian. if i take this class and a take the water out and that throw it, somebody could catch it. they would be doing the newtonian calculation because it is intuitive. if i were to do the same thing with an electron there would not be able to catch it. that is only part of the problem. the real problem is not that it is counter intuitive or crazy, it is that there is a real puzzle that we have not answered yet. have you go from the probabilistic map to the definite reality? >> but why do you have to? are you a gambling man? talked about your true habits. do you gamble? have you been to a casino in? okay. you have a roulette wheel. it rolls around. one number. thirty-six members. zero. it chooses one number read to

you have a problem with that? >> july have a problem with that? >> no, no. why do you have a problem with the probability for electrons? >> i don't have a problem with the description of the world and space and probability. have a problem with the theory that it is incomplete. no. einstein. >> he says it is incomplete. >> for a different reason. einsteins problem with quantum mechanics has to do with -- >> it has to do with a lot of things. none locality and the interpretation and all sorts of other things even though he had the vision to actually understand something we call today entanglement. the iep are paradox and so on. but what i'm asking is something at a lower level. you have no problem going to las vegas. well, maybe you do. you have no conceptual problem. hunting and mastodon or whenever. no problem with the world or

whenever you're hunting going one way and then another time you're chasing, going the other way. that is newtonian. would you need to see a shrink if the will of wind one to play and next time it went the other way. >> if the will flick like my mother or father. a master the point you're making. you do an experiment. when you can observe it the electron goes one way. can be to the right and then in another universe, another attorney for to the left. when you don't the electron goes both ways. we know that. we can think quantity. we are not the and atolls. >> we are trained. >> if we are. it's okay. both ways. interferes with itself. typical young experiment. only one particle. you have no problem with that at all. when you open the box you collapse said the speed. you involve the roulette wheel.

goes one way or another. by the way, the problem is not with mathematics. you know that. for a mathematician space operators and would never. >> that we get a sense, how many people are familiar? about three. i think we are going a little bit far afield. let me just say, my problem with quantum mechanics has nothing to do with the fact that it falls probabilities. i am unhappy with probability. >> no more many worlds. >> you somehow we're talking. >> that is the alternative to the probability. >> no. absolutely not. people who believe in many world also believe in probability. they are just trying to make a link between the probabilistic prediction and the fact that when you make an observation ec s&l definite reality. and that link is a subtle one that has resisted solution for about 50 years. if you were talking to a person

who does believe that there were many universes and quantum mechanics you would ultimately find that they are trying to explain the very same probability that niels bohr was trying to explain back in the old days. it is not like einstein where einstein had in his mind that physics needed to make definite predictions. no. we have long since gone beyond that because observations to show that the probabilities work. we are trying to close the gap and the actual quantum. my suggestion is that we move on from this because this is simply one variation. >> what is your favorite whatever? >> you know, it depends the way in which you judge favorite. but i certainly have a leaning toward those that have a chance at being experimentally tested in the shortest time frame, which is one way of thinking about the subject. from that there is a motorist that comes from string theory

which i find particularly exciting. it is called the brain malta verse. it comes from the following idea. so within string theory many people have at least heard of what the string theory is, this idea that the elementary constituents of those tiny particles in the old way of thinking of things. a little tiny dot. the new idea is within these tiny particles there is something else, which is a little tiny filament that vibrates in different patterns. this looks like a little piece of string to be the idea is that deep in the heart of manner is if bill thai a vibrating string. as we study the map of the theory more and more we have come upon the following perry interesting idea. within this theory there are not only did though tiny filament. there can also be what we call membrane, giant sheet that can have two dimensions are even three dimensions and so forth. the math seems to suggest that

at least it is possible that all that we know about every star and galaxy and so forth is living its life out on one of these membranes. a three dimensional membrane. let me just give a two dimensional analogy. imagine a big slice of bread where every star and of the galaxy that we know about is on this slice of bread. that is our universe. now, this proposal suggests the could be other slices of bread, the membranes, the universe is that are all part of the grand cosmic love with our universe just being one slice of bread, one universe in this grand collection. to answer your question, why do i find this particularly exciting? well, at the large hadron collider there is a chance that this proposal might be tested. how? well, the colitis slams protons against protons at fantastically high speeds. the map shows that in some of those collisions if there is enough energy, if they are moving fast enough, when protons

collide it can create debris that we get ejected off of our universe, off of our slice of bread. how would we know that? well, the debris would take away some energy. that means there would be less energy left for our detectors to measure after the collision than before. there would be some missing energy. people looking for these missing images signatures. if the energy is missing in the way that the math suggested it should be this would be interesting evidence that this brain picture is correct suggesting that there might be of the universe is out there. >> have you been depressed recently? >> what do you ask? >> you know that they have not found anything. maybe they will. right now as a lot of people may have heard, the results a negative. there are also-on something else. >> that me just respond to that. very early. if they found anything at all, it would take years of analysis. >> they do, but the importance. >> you're making a great point.

i would be thrilled if it wasn't because this is meant to be an experimental science. if we can rule out string theory. let me just be on the record very clearly to be with at the depressed? , would jump for joy. i am not wedded to a particular theory. i am wedded to working toward true. i think you go around once. you go around once, in this universe, i don't want to spend my time working on the theory that is incorrect. a string theory is right now would like to know today, yesterday. it is not a matter of having a certain emotional investment in one outcome or another. i have an emotional investment in contributing however minimally that may be to the ongoing human search for truth and finding that a given theory is wrong it is progressing because you can throw that one away. so depression, no. excitement. >> good. you will always be excited. >> that, to me, is the nature of

reality of the universe. incredibly exciting. >> running for a full year now. the end of march will be when they started. of course the stop for the break. they create some mini collisions every second. trillions. the data accumulates. they have not found anything. the first thing they ruled out that this energy level is extra dimensions. they don't think they don't exist, but they have not found. another direction. that least for a short while. all right. i just heard the they have not found any proof of supersymmetry either. >> that's correct. >> it just happens now. as of now with all the data they have collected, they have not found any supersymmetry. supersymmetry is another place where the mathematics and physics might diverge. so let me add something. i'm not here to play your psychologist. i am a little bit worried. how many people are familiar? >> i'll explain.

don't worry. >> okay. >> you know what, let me just explain it first. >> you don't trust me. >> it's not that i don't trust you. i don't know. you live here. they can come and visit you. i just come once in awhile. the full name of string theory is superstring theory. i'm not talking about string theory. the full names of superstring theory, over talking about the supersymmetry. now, what is it? supersymmetry is a fantastically interesting mathematical symmetry. it relates things as previously we thought were totally unrelated. now, if i take this class and then begin to turn this class around, it is highly symmetric which means that no matter how i turn it it pretty much the same. each point is related to every other point in a way that suggests that none is special. each can be turned into the other point by simply writing it. similarly there are a class of

particles in the world that are very important to us. particles that make us up, electrons, and things that make up protons and neutrons. those particles seem to be very different from a class of other particles by virtue of the fact that they actually spend around to friendly. those particles that we all know about turn out to have something called spin half, the way these little particles span. there are other particles that we know about that has been one, the photon or the particles that communicate the nuclear forces. there are some hypothetical particles not yet seen that would have been zero. there with nothing at all. supersymmetry is a mathematical symmetry that would relate all of those particles. in some sense each of those particles can be rotated into the others. if that is the case, for that to be true the rich have to be a certain of the class a particles not yet observed that the known particles we know about would turn into under this kind of some interpretation. those are the supersymmetry

particles. for the electron it is partnered under this kind of symmetry. it is known as the super symmetric electron or this electron neutrinos i don't name them. for every known particle there is a cousin call this article. so we are now looking for this article. if they are there it will confirm this idea. if they are not it either means that we don't have sufficiently powerful accelerators to create these particles or it may mean that they don't exist. that is the current state. >> it is a beautiful theory. we don't know if it has anything to do with the real world. the problem with mathematics and physics, the person who -- an english physicist who united quantum mechanics with the special theory of relativity. when he did that in 1928 he looked at the equations. i'm going to sound like brian.

maybe another universe. i am talking. what bryan says is we trust the mathematics. that me finish. >> you're putting words in my mouth. i'm saying. mathematics can be a potent guide for what we should consider interesting, what we should investigate further. until observation, until experiment confirms it died down trusted. you can't just observation and experiment. >> fine. so sitting in front of his fireplace at cambridge, he looks and realizes the way of uniting special relativity with quantum theory, creating quantum deal. when he does that he gets his mathematics, and then not going to put words in his mouth. he looks at the mathematics. the mathematics telson that there are negative energy levels for the electrons. he says, well, maybe anybody

else looking would have said this is just a matter. when use of an equation and you get to solutions, one is imaginary and one is real. i'm going to ignore the imaginary. the real one is it for me. but he did not do that. there must be a particle that has these negative energy levels. well, at first she thought it was a proton. then he realized it was another whole new particle. looking for new particles. looks for other particles. that article the positron with a positive electron was actually discovered experimentally sometimes later. so the point is sometimes it works, but it doesn't work all the time. that is the example of eisenberg. we want to follow the mathematics. we are an experimental science. you want to see where it leads us, but the problem is, and i think it is with a lot of physicists. a lot of this system they

believe in supersymmetry were follow supersymmetry a lot more than other theories. so if we don't find these particles that means here is the century. a beautiful but medical construct that may have absolutely nothing to do with this universe or any of the universe. >> that's right. ultimately nature speaks. it speaks to experiment and observation. there is a large segment of the critical community that takes this idea very seriously. we have been working on it in one way or another since the 1970's. so if these particles are found scientists around the world will be popping champagne corks. an exciting moment where the sample you just give us would be recapitulated in a very big way. if these particles are not found we will accept that as the way the world works and go back to the drawing board. that, to me, is drilling. >> fair enough. how about the of the theories? >> the other ways we can get to the multiversity. another simple one is one that comes out of thinking very

carefully about the big bank. so again we touched on the big bang earlier which is this idea that the universe underwent this rapid expansion early on. but one of the things that perhaps we don't emphasize enough when talking in general concepts is that the big bang theory actually invent something pretty important which is the bang. the big bang theory tells us how the universe evolved from a split-second after whatever started the average swelling to happen in the first place, but it does not tell us what cost that's willing to actually occur. people have been working very hard to fill in this gap. the reason i bring this particular gap up is because there is a proposal for what is called the offer and swelling called inflationary cosmology. it is basically the recognition that goes back to einstein that gravity on certain circumstances can be responsive. we are used to gravity being attractive. you got a glass and it falls. the drop the ball and it falls.

that is what gravity does. but actually einstein shows that under exotic circumstances brevity can actually put stands apart. the belief is that the possibility is that and the early universe, that exotic environment was realized. an energy suffusing space that give rise to ripples of gravity that pushed everything apart which is what the universe started swelling in the first place. the thing is when you study this theory in detail this seems to show that this out with swelling would not have been a unique one time event. it says that there could be many of these big bang like beginnings. distinct locations in a much larger cosmos. each giving rise to a swelling realm, each giving rise to an observable universe and a universe that people like us could inhabit. universes' upon universes' upon universes'. this is the inflationary most diverse. the nice thing about this approach is that the idea that space underwent this rapid

swelling early on from this ripples of gravity, that has been subjected to some very interesting observation of tests. if the universe went through this rapid swelling early on, here is what would happen. little tiny quantum jitters, quantum fluctuations in the universe would be stretched out by the rapid swelling and smeared out across the sky. if i had of the balloon with a fine tip pen, imagine i've read a little message on the surface. you could not actually see it. if i blow air in as the balloon stretches, message gets near out across the surface. now you can see it. these tiny quantum jitters may behave similarly. as space underwent this rapid expansion that message gets near out across the sky. tiny temperature differences in the heat leftover from the big bang, the cosmic microwave background radiation. we have measured this eat leftover. the way the temperature varies

from point to point is exactly in line with the mathematical calculation. and that is a very convincing piece of evidence for at least taking the theory quite seriously. >> at think the theory is taken seriously. not only seismologists, but astronomers and physicists. the question is, does it really implied the existence of something that is on observable. i think those microwaves fluctuations. as they expand, i think the galaxies respond. >> sure. >> does that really implied other than the mathematics, you keep going back to the mathematics. does the mathematics really tell you that if you see this picture of the microwave background radiation you must have -- >> no. not must, and that's why i'm not here saying that these ideas are proven. you may recall when we started up this conversation i emphasized that these are

speculative ideas that come from our investigation. until we have observation of them we can't believe that it's real. >> let me just take it a little bit further. what happens in the subject is when you have a theory that is able to describe things that you can't see, it opens your confidence to follow the theory for the. that is where the confidence comes from, to follow it further. does it uniquely implied that there has to be another round? no. there are versions where there is only one round. very hard to come by. very heart -- cumbersome and feel contrived. that doesn't mean they're wrong. it could be right. the ones that don't have that contrived quality of the ones that to give rise to these other universes. do we know they are there? absolutely not. does this suggested as a compelling possibility worthy of further study? yes. what sort of experiment might give you some insight?

well, a rhetorical. [laughter] if you have these expanding rounds, if you have these expellant -- expanding rounds, imagine it as a big cosmic -- a different universes with our universe being one in a bubble bath the bubbles can collide. similarly these universe's as they expand can collide. if they formed close enough together they can smash into each of the. how would we know that if our universe has a kind of offender been there with another universe? well, that collision can send ripples through this he's left over from the big bang, this cosmic microwave background radiation. scientists of looking in the background radiation to try to find finer patterns and the temperature variations in space that might indicate that we get hit by another universe. is there any positive evidence? not yet it could yield something too small for us to access or

maybe it never happened, but ths the way in which in principle you could have observational evidence of a universe that you can't literally see. ec its effect in our universe. feel free. >> how would you know? there have been settled generations of satellites looking at the microwave backgrounds. we know a lot. in fact, it is uniform to one in ten to the sixth. how would you be able to tell? to give us something concrete. they collide. you lost me at the beginning. i don't think another universe can exist on this axis. just the fact that we created this base. what is the space? you have not answered my question on that. hold on to be that if finish. >> you are given the impression that there is something missing command the missing part is your not fully comprehending the idea. >> i know what you're thinking.

the hyperspace there. >> no, no hyperspace. >> knowledge can be a dangerous thing. you know too much. of this is nothing to do with hyperspace. bread and butter cosmology that takes space in the quarter dimensions. let me just describe it. the water cosmos' do not think of it as a big sauna. yes. three dimensions. let's stay simple. filled with energy that causes the out word ripples of gravity. what happens is region by region in this day cosmos the energy can degrade. as the energy degrades polls opened up in this water cosmos with the energy turns into particles that make stars and galaxies. so our universe is simply one of these regions with the energy has degraded. the image, think of a block of

swiss cheese. imagine that it's easy part of the swiss cheese is where this energy exist and it is forcing things to experience gravitational repulsion. the holes in the cheese are places with the energy has degraded. said the different universe is that i'm talking about are just different holes in this big expanding block. >> really one universe. >> whenever language you would like. as i said early on. as i said early on hamas the language is confused. >> that me ask you, we are talking about experimentally detecting the evidence of the most diverse. >> yes. exactly. so these universes' colliding debate here is the background, radiation. it is fluctuating. how do you know it's from that and not from something else? >> that is a question you face with all experimental data. he tried to rule out all of the

competing proposals to read the proposal that stands up and is the best explanation is the one that you gain confidence in the beat we have done calculations. actually, i have not done these calculations myself. others should get the credit. other physicists have done calculations on what would happen to the microwave background radiation under this process. very explicit protections for what would happen. how the temperature would vary from place to place. if you find temperature variations in line with those predictions and there is no other competing explanation then, indeed, your confidence in this possibility with hardly grow to be that is the way science works. >> fine. let's assume it will happen someday it will have proof of it. until then we don't know. >> i agree completely. rex of want to make sure people

get access to interactive they want to. i am happy to keep on going. whenever you want to do. >> you have an answer. >> okay. anybody have a question? want to throw anything out? >> he's tired of my questions. >> some questions now. we have to museum staff members with microphones will be walking up and down the aisles. they will select few, and when we do selectee please stand up. don't begin talking until you have a microphone. we are ready for some questions. >> first question down here. >> moves very quickly, but in 2006 lease mullen, the medical physicist at the institute in canada wrote a book entitled the problem with physics.

>> the trouble with physics. >> excuse me. >> it seems to be that he has basically abandoned string theory. chiefly because of lack of experimental confirmation. so my question is, has he abandoned it too early? in his carry-on? >> a bigger question. lee is a good friend of mine. says things that rebuts a misinterpreted. what he plans to viscerally meaning to say is that string theory is not the only approach. there are other approaches. he is a champion. duke constant -- quantum gravity. part of what he was saying was he feels too many people work on a string theory and not enough people work on quantum gravity. the help of the field with the

advance if there was a more balanced approach were more people work on these other approaches and string theory wasn't the primary one that was looked upon as the solution in the physics community. you know, i agree with that. i feel that the health of the field is evidenced by all sorts of different ideas. the reason why more students work on string theory frankly is i think it is a more attractive and more appealing and promising approach. i think that is how graduate students make their decisions. you know, apple will agree that it is -- it would be great to have active research in all these approaches. he helped found the perimeter institute you mentioned, and there are a lot of people working on quantum gravity. the idea that he abandoned, it's not released during. if somebody were to and from time to time because he is one of the folks that really tried to cross over melding them together. he and i discussed this. that would be great, but his main point is that there are

other approaches, and they deserve attention. on that point would agree. >> we have a question over here. >> hi. my question is related to the many world theory. basically about the fact that right here at the world acted be asking the question of someone else. but whose world is it? if we were making these choices, recreating these worlds? whose world is this? is what is the of the world? yours, mind, someone else's? >> well, according to the bread and butter many world approach, as others have developed its the 1950's, if you are in a situation where quantum mechanics says there is a possibility of this, possibility of that and the possibility of this and so forth, all of those possibilities happened. it's not really a matter of you choosing which happen. the mathematics does not allow any possibility to go on realized. all roads are travel in the

quantum of the first. you know, i'm teaching this right now. and teaching undergraduate quantum mechanics. i am literally this week talking about the many worlds approach. we set it up last week. it is if you actually go through the mathematics of it which very few people i've found actually do. few people go back to the 1957 paper and read it. few people go back to the pieces that was written down back in the 50's and read it.

one universe where, like sarah palin is president, you know, and i have to tell them, you know, it has to be compatible with the laws of physics. [laughter] >> next question over here. >> you mentioned other potential theories. do any of them have implications as far as the multiat the universe goes? >> i don't know enough about them to answer that with any degree of confidence. in all of them, quantum mechanics is part of story, so if the quantum multi universe i

tries, witness be embraced in the american i have been discussing, that's true. >> question over here. >> in your many bubbled world, we know that after the big bang, certain specific criteria had to be met or the universe would have blown apart. so in other world, do they have to follow our laws in order to succeed, or did some of them die? how does that work? >> one of the deep questions we have faced over the last 15-20 years, is in line with what you are asking. we have measured certain features of our universe, certain numbers, parameters, like the strength of the electromagnetic force, the masses of the cores, and we found we understand the numerical values but we haven't been able to explain why those

values have been found. you might say, should we care if the electron is lighter or not? if those numbers had been somewhat different, then the universe as we observe it and know it wouldn't exist. if i had a machine up here with 20 dials and i called someone randomly to come up and you make gravity stronger or the force weaker, the fiddling you do, the universe doesn't evolve, the stars don't farm, planets don't form, and it's hard to imagine how life would exist in such a universe. so the deep question has been, why do those numbers have the right -- we have hit a dead end so far in trying to answer that question. the task is a different way of thinking. the idea is maybe there are

many, many universes in which those numbers vary from universe to universe to universe, and in most of those universes, we couldn't exist because the stars wouldn't be there, the planets wouldn't be there. and the answer for why the numbers have the values we observe, we couldn't observe any other value. we couldn't exist in those other realms, and that is an approach that may ultimately hold water. now, let me just give you a little analogy on this that happened to me two years ago as my four-year-old, which i think helps one understand this a little more. my son is sick years old now. he was three and a half. we went to a shoe store. this is the first time he was really old enough to begin to think about what was happening. we go into the shoe store. the guy measures his shoe, goes in back, brings out a shoe. my son turns to me and says, wasn't it lucky they had my shoe size? [laughter] >> and is a drove further, i

realized what he had in mind was that shoe store had a single shoe size and it just so happened it fit his foot. what a mystery that would be. but when i explained to him that in the stock room there are many, many different shoe sizes and the guy picked out the one he measured, the mystery went away. the moral is, if you think there's a unique object to explain, that can be mysterious. but if you realize it's not unique, the mystery can evaporate. that may be true for these parameters. we find a universe where the parameters fit our existence, >> are you familiar with a man named ronald mallet and his time machine experiment?

>> in connecticut, yeah, right. i guess he says you can twist time enough -- >> go back in time? >> well, or at least a subatomic particle spring back to when the machine was turned on. if such a machine were built, could something like that possibly be used to maybe test some of these theories? >> oh, boy. we're now no speculation squared here. how would time travel interface with these ideas. let's turn it in that direction. and one of the big puzzles of of the time travel is you go back in time and you affect things in the way that prevent your own existence. you kill your parents before you

were born, you know, "back to the future." hollywood loves this idea. a variation on the paradox, you know, which comes from the following idea. imagine that you travel to the future. national i traveled to the future, let's just say, and i want to see what happened in string theory, whether it's proven or not. so i go to the library or the floating internet station, and i see that surprisingly the awe author of the paper is my mom and i'm like, that's weird because my mom doesn't know about physics. she wants me to be a doctor but that this kind of doctor and all this stuff. and i look in the acknowledgement to the paper in the future, and she thank me for teaching her all these physics. i'm like, holy crap. i got to get back. and i go back and start to tut

for my mother and it's not going well. and years go by, and i'm like, how in the world is she going to write that paper? then i said to myself, know what was in that paper. i read it. i can tell her what to write. so she writes the paper and everything turns out. the question is, who gets the credit? [laughter] >> not a question of credit. at it a question of, where did the information come from? did she think of it? no. she got it from me. i got it from her paper. so things are possible. how does that relate to multiple universes? here's a possible idea. imagine when you travel to the past, for instance. never come back to your own universe. you come back, say in the quantum -- in another copy of our universe. so if i go back in time and kill

my parents before i'm been, i wouldn't be born in that universe, but so what? my origin would still be unaffected because my parents would be unfaked -- unaffected in the universe which i started. so that's some interaction with time travel. >> question over here. >> i just had a question about something i am recently aware of. the einstein condensation theory, and something that physicists now -- we're lucky to live in a this time. if they can hypothetically if they can create that instant in a room, assuming they can -- is that to -- do all the basic theories break down? if you have a situation -- >> i don't think it does that. brian will be the final are

arbiter. >> you cool some atoms to a very, very low temperature and what happens is the wave, the particles of wave also so the waves overlap. so you really creating quantum mechanics for a collection of atoms. i don't think it relates to anything else we have been talking about. >> it really comes out of basic quantum mechanics. >> the principle? >> pardon me? >> actually reach a bowes einstein principle. >> i personally wouldn't describe it that way. >> m.i.t. describe it that way.

>> we have time for one last question over here. >> excuse me. i should preface this by saying i'm a die hard miniworldser. so i was impressed by an observation in your first book where you noted a duality between one over a time, which seemed to have a special meaning, if i understand this correctly, at one time after the big bang when the energy wound and unwound, and there was something -- i don't recall the details now but something you said there, and a note prompted this idea, and i'd like to know if anyone is pursuing anything like this. if you imagine there's a moment, perhaps, one moment after the big bang of perfect symmetry. finitely described universe that is many-world style.

and whatever it takes to get us forward to all the different versions of us here now and caps. we could look at the same thing. you expect the same thing to be happening in that one overinterpretation going back towards the moment of the so-called big bang, and now singularity turns into the illusion. here's this image of us and we have another moment in time. anyone pursuing ideas like that? >> it is one of the most surprising features of string theory, which shows that under the circumstances your recounting, universe that is bigger than -- plain and

expanding, that's the r in the one over r world you're talking about. i wouldn't use the word image to describe these two realms. they're real distinct descriptions of the same reality. so two different ways of looking at the same thing. even though say seem vastly question. as to your question, how would the singularity look in this picture. here at harvard, they study cosmology and the found something along the lines of what you're suggesting. so if you run the universe back in time, it gets denser and denser, to infinity. they found that in this setup, when the universe gets smaller than a plain, about a tenth to

minus 35 meters. the temperature levels out, and as the universe gets smaller, the temperature starts to turn down because of the very symmetry you're talking about. it never spiked to infinity. never a time when the density. there are other things it doesn't describe yet,so much word needed to be done to take it fully seriously. but as a test case of a cosmology. it's one of the most potent ones to come out of string theory. >> another question? >> i just want to point out if you're taking that kind of a mold -- model seriously, we would be represented be all of the possibles in the many worlds that could have happened to t