String Theory and the End of Space and Time with Robbert Dijkgraaf

thank you a warm welcome to this to this talk actually with 500 string theories we have been here for a week studying the latest development and you can imagine we really are looking forward to a drink and so this is a very special audience because I would say like one in four among you are real specialists so for the others the trick is to find the string theorists and in the break or over drinks ask them anything you want them to know so the topic tonight will be about a very odd and all an object and subject that's just around us space and time now if you think about space actually the stage here is a good metaphor for many many centuries people thought space is just out there it's flat it's rigid it's forever as it is it's just the background the decor in which natural phenomena happen and time similary was just a big clock that directed all the phenomena that happen in nature Ernest Newton famously said it's an absolute and time that kind of goes on forever and ever it flows without regard to anything now all of this changed dramatically with the next character Albert Einstein Albert Einstein famously said time is the fourth dimension and we'll be talking tonight about extra dimensions and this might be something a little bit dizzy in for you so let's start slowly so let's start with two dimensions now we can all imagine this is square it's actually nice two dimensional let's go to three dimensions oops this is three dimensions actually this hope you appreciate my PowerPoint presentations here they're homemade so this is a cube but actually you're not watching something three-dimensional of course this is a two-dimensional screen but even if I would have brought a real cube right at this moment you're looking at your retina the backside of your eyes and so if you think you see the third dimension actually it's an illusion your mind sees the third dimension so why not go one step further for instance try to see four dimensions this is a four dimensional object not a colleague who looked at these objects for a full year manipulate them in the computer hope that something would say click in his mind and it would see the fourth dimension didn't happen so I'm always looking for a volunteer that spends a little bit more than one year trying to do this these exercises but actually this is not if and what we're trying to do I want to actually explain this with another example this is a little movie so you see two little balls moving but actually you're not looking at the movie what you're looking at as in any movie is a sequence of images so think of the individual images of this movie as individual pictures and stack them up in a high stack like this you see if you go up in the stack you're later in time time is flowing upwards so with two space dimensions and one time dimension well Einstein said is let's glue all these little things together and make one big thing call it space-time it's the one on the right and you see the little balls are now these kind of spaghetti strands that go up so while we are sitting here in the stage we are moving in space-time we're moving in time all of us go like one second per second flowing up in the fourth dimension now of course whenever we talk about physics I'm of you lying because the real thing is showing the equations now I know if I'm showing equations is very dangerous but you know you shouldn't be afraid of equation so a typical equation looks like this a equals B and the most important part of that equation is actually right in the middle it's an equal sign good equations connect two worlds a and B that you might not have thought are connected at all and so for instance Einstein was brilliant in writing these kind of equations for instance the most famous equations I think in the world is the equation equals MC squared so if you think about that equation let's try to see whether I can produce it yes there it is why is it such an important equation because it connects two different concepts energy and mass in a way that you might not think are connected with tremendous consequences it means you can take mass and produce energy out of it as it happens in nuclear processes and atom bombs or you can take energy pure energy and create particles out of it that's actually what happens in the big colliders now there's a similar equation that is even more powerful which is the equation Einstein used to describe gravity general relativity now unfortunately this equation is not as famous as equals mc-squared a little bit more complicated but it has the same kind of beautiful flavor that it connects two worlds that you wouldn't expect to be connected on the left-hand side is a mathematical symbol that captures space space and time on the right-hand side is something that captures mass and energy so in words or in images what this equation is doing it's telling basically mass tell space how to curve if you put something in space like I'm standing here on the stage actually it's like the stage is made out of rubber it will Bend space can curve space and time can curve that's one part of the equation and in equation the other way round it says space-time tells mass how to move because if you have a curved space what do you mean even by going straight so for instance if you think about the moon orbiting the Earth actually it's the Earth's gravitational field curves the space around it and the moon tries to go as straight as possible in that curve space and has this beautiful circular motion well this inside of Einstein was absolutely brilliant and he realized that if this is the case everything should actually curve what happens yes everything should be curved in particular also light and so he proposed an experiment to measure the deflection of light of stars close to the Sun and this could only be done after World War one in 1919 effects last may be celebrated exactly 100 years ago at the eclipse of May 29 1919 that this particular experiment was done by the British astronomer Sir Arthur Eddington and he actually measured this and created this wonderful picture here you see it you see it the solar eclipse this actually a copy of that picture that we have actually in Princeton it's belonged to Einstein so this actually showed him he was right but this was just after the war he couldn't directly communicate with the British and affect the communication went through the link between Einstein and Lawrence Lawrence the famous Dutch scientists here they are together and so Lawrence had the honor of informing Einstein that he basically made the biggest discovery in science and here is the telegram and it's kind of funny because it writes Lawrence is very Dutch so he writes ok editing found 2 star shifts at the SolarEdge preliminary sites between point 9 seconds and double Lawrence so nothing like congratulations you just made the biggest discovery in the world probably you have to pay for every every word but of course this was not the reaction of the press when it finally no appeared there was this wonderful headline in the New York Times saying that stars were not where they were calculated to be nobody needs to worry also this book of 12 wise men which is really I think ridiculous and in the German press he immediately was celebrated as a new giant of world history so instantaneously Einstein became world-famous he traveled all over the world including to the new tune to the United States to New York [Music] I'm delighted what do you wonder for clip and he would definitely not enjoy the cocktails so of course as I said I'm Stan was done in a wonderful position and he could do for the first time a calculation people already dreamt about he could actually put the whole universe in his equations he could calculate what happens to our universe and he made that tremendous discovery he found that actually the universe wanted to expand and this was really shocking because he immediately realized if it's expanding in the future then in the past it must have become smaller and it must have been a point what we now call the Big Bang where the universe was created and this was so strange the fact that everything would be created at the single moment that he did something very bizarre he changed his equations he actually added an extra term to his equation we call it now the cosmological constant a mysterious force he presumed that's an empty space that is kind of helping the universe to stay in place afterwards and now we all know that the universe does expand he must have said that this is his biggest blunder but because he was in a position to predict perhaps the greatest prediction ever that we live an expanding universe and that there is a moment where the universe was created that moment actually came later and in fact it was the Belgian physicist George Lemaitre who actually made that discovery he made this prediction in 1927 he's a unique figure he was also a priest so he was the one person Einstein and popper one handshake away and that was actually shores limit who was the in-between the only thing it wasn't successful is in naming the Big Bang it rides primeval atom cosmic egg and these names haven't stuck I think they're quite beautiful in the end it was Big Bang they actually Astrophysical detection of the expanding universe was two years later by the American astronomer Edwin Hubble who actually noticed that the galaxies and were kind of floating away we're moving away from our Milky Way now this is you know something that we're now familiar with an expanding universe is like the universes big balloon that's being blown up but you must realize took a long time for people to accept this idea and the crucial moment was a measurement made by two radio astronomers Penzias and Wilson who they were actually just engineers that had that word for 18t labs and were working on this microwave satellites reception dish that had an annoying noise and they couldn't remove the noise until astronomers told them you guys might have picked up the signal of the Big Bang and it's a very impressive signal so I think we should all listen for it to it for a moment this is the sound of the Big Bang but 14 billion years after it happened in fact you can observe it with your own old-fashioned television sets if you have a television set with an antenna then as little noise if you don't pick up a signal and apparently 1% of that noise is coming from these photon these light particles that had traveled all the way through the universe to arrive on your television screen and but in fact now we can measure this more carefully this is a beautiful picture this is not a Pont allistic painting this is a so-called baby photo of the universe as it was just after Big Bang roughly four hundred thousand years with cosmologists find just after in a split second after the creation and these little pixels actually these little changes are responsible for everything we see around us we have now a full understanding how from this initial conditions the universe was formed so if you now look at this little animation you see by zooming in that these little changes matter is being created actually it's through gravitational interaction it condenses the first elementary stars are being formed the first versions of galaxies these galaxies grow the stars grow through many generations planets are being formed in the end our Sun is being formed the planets around our Sun including our earth and life on Earth so we live remarkable times in the sense that we have a pretty complete understanding of 14 billion years 13.7 billion years of cosmic evolution a remarkable thing that whole story was figured out by us here on planet Earth in less than a century we have been able to capture that whole story so it's in terrible and terrific success on the other hand I often joke that cosmologists are special because they they know exactly what they do not understand and so many of you might ask what do I know I don't know and almost like these old maps the old maps were made by cartographers and of course there were empty spaces there were blank spots on the map but it didn't dare to leave them open and blank what they did they painted and drawn these awful sea monsters so in some sense we have still see monsters no longer in our oceans within our understanding of the universe and let me show you two of these sea monsters the first if you look at galaxies as the physicists have found that these galaxies are not just galaxies they're surrounded by huge clouds of matter matter that's invisible it's actually transparent we call a dark matter this dark matter is actually everywhere in the universe in fact the amount of dark matter in the universe is roughly five times more than the visible matter that are we are made out of so the X if you could see that dark matter the night sky would not look like this but you would see all this stuff so often like the example of a Christmas tree at night so we that is to say stars and planets and all of us are like the little lights in the Christmas tree but if you would be able to see dark matter we were able to see the branches and leaves of these Christmas trees if you actually could see dark matter the universe would very look very different now if you would fly through you would see these big strands of dark matter that somehow hold the whole universe together where our stars are just these little candles on the branches there is another sea monster that came as a big discovery when astronomers were measuring carefully the expansion of the universe they found it actually they might think it would slow down you have a big bang and then in the end gravity tries to pull things together but exactly the opposite seems to happen the universe is expanding faster and faster and faster it's like that space is like a sponge that has been compressed and wants to kind of expand in fact is the wonderful recurrence of einstein's idea of a cosmological constant so his blunder was brilliant the man is really very special however the effect is not what he was looking for something that would hold the universe together it's actually has the opposite sign it's making things worse empty space want to expand and create more empty space and this is one of the remarkable discoveries in fact if you look at the composition of the universe if you think of it as a cocktail to use to tonight's metaphor only five percent of the cocktail we understand that's made of the matter and gas and radiation that we all physics discoveries here the physics that we understand 95 percent is made out of these two mysterious ingredients dark matter and dark energy and so that's that's progress we at least we know what we do not know now there's another thing that we don't understand and these are black holes and black holes have been a physics for a long time early after the discovery for Einstein's theory physicists already realize that if you have a lot of matter put together then actually it can stars can collapse and creates not only a little little hill a little indentation in space but really it's like throwing a bowling ball on a rubber screen that kind of creates a real deep infinite deep hole now we again be living in remarkable time because all of us were around on April 10th of this year when the first black hole image went around the world I think literally every newspaper in the world must have had a picture of that famous black hole in fact it was a gigantic black hole it's a black hole that lives in a galaxy not our Milky Way but trying to get this yeah measured by the greatest telescope has we ever produced a telescope literally the size of the planets by connecting individual telescopes and it looks it looked at this this galaxy it's called m87 it's 55 million light years away it has a black hole we think we thought in the center that somehow swallowed more than six billion stars and just for comparison here you see on the bottom left our Milky Way so now even as a galaxy we are kind of average you know and what this telescope was able to do is create an image that is by the way the most magnified image they never ever we have created such a big telescope and never ever have you seen such a small detail on the night sky so it looked in this kind of galaxies it's closed in the in the in Virgo here we are zooming in you see this big thing flaring out and here's the image this kind of black hole absolutely markable and you indeed see a black thing in the middle that's very closely related to the hole that the black hole creates and I must say just a personal story a few years ago was asked to paint a mural for a black hole Center in Harvard so I painted the black hole and said well if it's actually ever been photographed I will repaint it but actually I think I was pretty pretty good if you look at the image I think I can even magnify it here it is so pretty good so [Applause] so but again black holes are astonishing objects to to understand because then one thing they do they have the issue say what are you what are you looking at in the middle this black hole effect it's called the horizon if a black holes formed by matter that falls in it creates it all gets squeezed into a point but inside around that same so called singularity there's a no-go zone a sphere surrounding this which we call the horizon and if you fall through the horizon you're doomed and in fact you're doomed in a very bizarre way literally time that usually in these pictures is flowing upwards inside the black hole it moves inside so the moment you step into this black hole that might be just like in this particular black hole that might be just like a few hours of time left so it's like you you're watching a movie and you know it's still ten minutes to go you know something dramatic has to happen because the movie has to come to an end this literally time stops and that's something that we're really worried about now I think of this if you think of the history of the universe we have this tremendous success but there are two things we really do not understand which is the beginning and the end how did the universe start at the Big Bang and how does it end as it does inside black holes so I think it's a little bit like one of these beautiful Flemish tapestries where at the very edge you see what the fabric of space and time is made of and there's a famous scientist John Wheeler who said you know how can this be these space-time singularities how can physics lead to a violation of itself to no physics as he said how could it be that Einstein predicts that this theory is unpredictable and so we love this now these are the kind of the open problems that we want to solve now I hope you're now thinking of space-time in a very different way it's no longer a rigid stage it's very flexible it's full of life it can curve it can begin that can end it's a very rich topic to study but to find really the solution to this we have to turn to the other not outwards but inwards and look at elementary particles that's the world of accelerators where these kind of a big mess is being created by colliding particles with zooming in to the smaller structures now for a long time people thought that but this was unsolvable particles were so difficult to understand it would have been a black box but then they discovered in the 1970s and later that actually not only the box could be opened but inside was a very tiny formula I don't want you to understand that formula but you must appreciate the power that the single line is describing actually all the physics that you see around you here the particles that you are made of that everything is made of and how to interact now if you actually go and take a physics course you get something like this which is the real thing but I would like to say you can also put the whole thing on the t-shirt effect now with the Higgs particle as you say the brow Don Blair makes particle added to it 17 particles they're describing all of physics as we understand it it's a tremendous success tremendous success now how is this theory kind of constructed and we have to actually go into the world of quantum mechanics now quantum theory is very dizzying it's very bizarre but I want to explain it a little bit with one what one of my favorites kind of metaphors and that was a metaphor it was created by again by John Wheeler when he was a professor in Princeton talking to his graduate student at the time Richard Feynman famous physicist and wheeler asked Feynman how come that all particles like all electrons are exactly the same or they have the same charge the same mass it's like there's a factory that produces these particles with perfect size and perfection he says I know the solution because there's only one particle in the whole universe so what did he try to understand and there's all the same electron so he's lost his image here is the particle now usually this particle has to go up in time like everything else but suppose that we could be more liberal and particles could also backwards in time so it would be like there is a time machine here I could step in a time machine go back an hour walk inside the lecture hall and stand here next to me would be perfect copy of me right I could do it three times four times I could make identical clones of myself so realist said suppose that this particle is able to throw through space up and down and up and down and creates a big knot that will be terrific because if you think of this as a movie sequence you would have a single particle in the beginning but in the middle he would cut it you would see many particles and antiparticles that the particles going down and of course they are the same have the same properties it's the same particle well there are lots of problems with this and you know the war intervened and Fineman forgot this whole discussion but then in the 1940s you start thinking about again and I love this image this is an image of his notebooks where he's very very carefully tries to push these particles backwards in time and see how does that work and it works beautifully he's able to reproduce with these diagrams all physics and now of course they're called Fineman diagrams in fact there's a nice anecdote a few decades ago there was a young physics student and he saw this van driving in Los Angeles and there was a woman driving the van and he stopped her at the intersection said madam you know do you know these these diagrams these these these this graphics on your van these are called Feynman diagrams we used them every time and we just used them to describe the world and she said yes I know I'm mrs. Fineman and here's the family with the van and the fact the van was is celebrated that actually was recently you could you could buy it so somebody bought it and I hope it's will end up in a museum in fact you know there are many more things here to be sad folk can wake up my computer because if you look at the standard model there's one thing it says which is this particle so what a beautiful Theory this is amazing powerful but another part of our brain says why this no why is every particle come in like a small medium large now why three colors - there is a lot of things that doesn't we do not really make sense so we try to make more sense of it we play with these models we try to combine them in different patterns say perhaps there's a grander theory that that kind of unites all of this and we notice that the forces in nature are four fundamental forces they are very different in ordinary life but if you go to higher and higher energy skills this seemed to be getting closer in character so we think that nature has a bigger story to tell and it might be connected to all the other things that we do not understand the 95 percent that is missing in fact quantum mechanics is a bizarre theory not only can you go backwards in time but for instance this can happen a particle for brief moments can split in two particles and then reunite again I like to say you know if you do it fast enough before it's detected it's okay which actually fits very well by the way with the Dutch attitude towards life I think many of our laws are based on that in fact you can have something like wheeler proposed you can have this you have two particles a particle antiparticle being created out of nothing or if you wish a particle going up and down in time forever and ever and ever so these things happen actually right as we talk in empty space in fact this is my visualization of empty space empty space and time is filled with these little bubbles of nothing particles that live for very brief time like little fireflies for brief moments in fact there's a wonderful saying that like in quantum mechanics everything that's allowed is obligatory everything that can possibly happen happens in empty space and we think this has a tremendous consequence because this punch the fact that space itself has its own pressure it has its own force its own energy must be reflection of all these quantum process in fact we think that if you look close into space the analog of response might be right because of his jus main zoom in zoom in at some point like in an ordinary sponge there must be little pixels it must be little atoms of space itself and we somehow know how small they are they're remarkably small 10 to the minus 35 meters called the Planck length but we do think that in the end space disappears in fact one thing I find absolutely amazing that we now have an understanding of both the smallest and largest distances in our world the smallest distance is this Planck length it's the it's the scale in which space itself no longer makes sense if you zoom further in you don't see anything there's also a largest scale which is the scale of the universe that we can see it's the so-called visible universe it's the hubble scale and there are 16 stab 60 steps of 10 powers of 10 to go from the left to the right right in the middle I find this very kind of metaphorically pleasing it's the scale of life the scale say of a bacteria or human cell and if you go one step to the right you actually at the level where the moon is the distance to the moon that's as far as we have traveled as human beings and if you take a step to the left you a bit roughly at the scale where the experiments in CERN the most smallest elementary particles that we have detected are though that's why we traveled in terms of the microscopic world so this is a pretty amazing picture that we actually have created this picture and understand this picture now there's one question of a thing that you was already raised in that you know everybody asked you know what what happened before the Big Bang and I give you little anecdotes because I was with my son it was eight year at a time in a beautiful exposition in New York which was you know a simulation of the Big Bang so we're standing in this dark room and certainly a big flash and then we soul stars and galaxies it was amazing and afterwards he said daddy that's what it was a remarkable but no what we were waiting for the Big Bang what was this and say well that's the question what's there before the Big Bang that's exactly what daddy and his friends are thinking about every day yes it's true Wow cool so I felt so great with this episode and so that day you know you go to the office with a little bounce you know this is terrific you know eight-year-olds understand what we're doing and afterward so I came back home and he looked at me say and so for a day but there's a beautiful thought the beautiful thought is that at the Big Bang there was a period of rapid expansion recall inflation were these small Wiggles that are always part of quantum theory have been magnified in a tremendous way blown up literally to cosmological proportions creating this pond holistic painting that the Big Bang started with so there's a beautiful idea here that you know if you want to understand why the universe is as it is which is understanding the world at the largest scales we actually have to understand it at the smaller scales and there's a connection between the smallest and the largest which is somehow very satisfying in fact there are other things that we think we can understand by marrying these two theories of Einstein's theory in quantum mechanics famous result is due to Stephen Hawking remember I told you that like in empty space they're continuously particles and antiparticles being created but who can ask the question what happens if these particles just live on the very boundary of the horizon of a black hole then the Fallen thing might happen one particles outside the other one is inside the particle that's inside is doomed it's being pulled into the black hole and the other one has to escape and through this idea black holes can at least on paper that can radiate they can they again kind of emit particles it's not a literally a black hole it's a slowly glowing black hole that gives back the information now to understand all of this you need proper physics and this is exactly the topic of string theory so in these string theory is something you know quite simple to explain the in the audience let's see what happened it's a generalization where instead of thinking of particles little points we literally think in terms of vibrating strings like here we have in the pianos or in the violins and if you have a string it can kind of resonate at many frequencies it can have many tones the harmonics of a musical string and in physics the different harmonics constitute different particles so it's one way to unify all particles and remarkably one of those particles describes gravity now it has many many advantages like for instance you have these famous Feynman diagrams which describe the standard model that has many questions for why this in string theory they are described by two-dimensional surfaces and the interactions with between these strings are purely geometric that actually something we like very much there are many other kind of advantages and in fact there are not only closed strings there are also so-called open strings and open strings are strings that have two end points and it can be attached to objects brains and if you want to study strength you have to study all of them together and it's a magical mix it all hangs together and you can find remarkable results I want to present a few of these just to get you a taste of what string theory can do for instance this is the way in which string theory understands black holes so here's a black hole the horizon of the black hole that's the area I shouldn't fall in and outside our de so-called closed strings what they do actually they describe the gravitational field so they describe space-time at the elementary level and then there are also kind of these open strings that are kind of attached to the horizon and we think actually these are the ways to describe quantum black holes and for instance one thing that the string theories have done is this to calculate what happens if you look under the microscope in fact what you see is that some of these open strings can attach and fly off and that's a calculation that repres Hawking's results so in strength u we have a full understanding of certain classes of quantum black holes there's a tremendous advantage in fact our other crazy ideas for instance is the idea of holography that in some sense it's good enough to only understand that surface of the black hole that basically just has to have a hologram which looks like three dimensions but it's only two dimensional and if you move you see the illusion of a third dimension actually string theories that see think that even the dimensions that we are experiencing every day might have that illusionary elements they might be part of a kind of cosmic hologram and in fact that's why we're so excited about black holes because you know if you want to see one place where quantum theory in Einstein are really clashing it's in black holes I like to say there are like the atoms of the 21st century on the one hand from a gravitational perspective a black hole is just a hole in space the simplest possible object you can have but from a quantum perspective it's the most effective way to store information it's like the the most compressed hard disk that Nature has built and so we love these kind of paradoxes if something is well from one point of view the simplest objects from another point of view the most complex objects and yet these things exist we have seen pictures of them in the newspaper that actually means that there is this homework assignment we have to figure it out but Nature has we know that Nature has found a way to marry these two concepts so we think that you know you you have this dizzying display of skills we think that there might be even something more fundamental than quantum space-time that perhaps now pure information 0 and 1 or more precisely quantum information might be something that's underlying all of reality and people have scientists we might be a little bit like living in the matrix something might be all kind of a big simulation or in the end perhaps there are just bits and that's it there's one final thing I want to bring to your attention now in string theory there is need for extra dimensions and this is actually very old idea Einstein himself was very puzzled by this and fascinated very soon after his discovery of his theory of gravity the three space and one time dimension people figured out if you have one extra space dimension so if if you have little circle at every point in space that it will have tremendous consequences because first of all you get electromagnetism and particles cannot go straight but it can go a little circles in this extra dimension and depending on the speed in which they go around the circle they have a certain electric charge so it's in a beautiful example how you could take two forces in nature electromagnetism and gravity and unify them using an external dimension now in string theory we need not one but six of these extra dimensions and sometimes we have even models where there are seven and they can be two curled up in much more complicated ways than just a circle and so we studied these theories there are kind of these beautiful images here of these manifolds very intricate ways in which nature would be hiding these extra dimensions in fact there's a dictionary there's a dictionary that tells you that the shape of that space isn't one-to-one correspondence with the phenomena that we see in our four-dimensional world like the things that were on the t-shirt the particles and the forces and in some sense that is realizing Einsteins dream Einstein always wanted to produce everything out of geometry and so string theories are in some sense trying to realize this using in the same time also quantum theory now this has tremendous consequences because if the physics as we realize is produced by the way in which these internal dimensions are called up and this cannot be done in a unique way there many choices there are there's something the whole landscape of possibilities and perhaps now our world our laws of nature what we think is something you know that's unique and picked out know by whatever by God's by nature to describe the world might be just a choice there might be other alternative universes and if you're taking this serious you have to start thinking about what we call the multiverse of all possible universes and it's not a thought experiment because we think under the laws of quantum mechanics it's very well possible that you know one universe can create so to say an other universe a baby universe which has no a complete heart reset with different laws of nature's a different set of particles and perhaps completely different kind of cosmology so this is absolutely dizzying and so if you think about I had a even bigger picture but they say yet even bigger picture where at the other ends at where at some point if you thought well the natural endpoint of our thinking is the whole universe that might not be the end you might go even bigger we might be living and have to study all these possible universes so I think this is an absolutely remarkable picture and I would like to say this is the moment when you arrived what I'd like to say at a higher level of confusion it's just the thing that we are struggling with and often they're the one thing that physics does is not so much provide all the answers science does but provide these wonderful questions we somehow start to get to know what we do not know and I want to kind of finish by two quotes the first actually is by Einstein and now when he was a young boy the story has been telling for very often I was five years old and he was sick and he was given a magnet a compass and he noticed that the compass needle was always pointing in the north but then he actually started walking around through the house with the compass and he realized there was a force pushing guiding the needle and that there was something he couldn't see that filled all of the room of course he discovered as a five-year-old the magnetic field I think it's a beautiful metaphor because Einstein in his world is life as a scientist discovered that indeed space is filled with all this magic can be curved that candle can expand it can begin that can ant it's full of these quantum particles it's a beautiful metaphor the quote I want to give you is this one that is setting in the ends imagination is more important than knowledge knowledge is limited to all we know and understand while imagination embraces the entire world and all they ever will be to know and understand the blank spots on the map the place where perhaps you know sea monsters live but you know we are so excited to discover I think the some sense scientists are the equivalents of the explorers of the old days that sailed into the great unknown the final quote I want to give you is from Stephen Hawking so as you know Hawking passed away last year he passed actually way on March 14th which is Einstein's birthday in fact I think Hawking was born on the death the day of that Galileo died so there's a lot of cosmic coincidences here and when he passed away there was a message from him that was beamed into space using a big radio telescope in fact it was beamed in the direction of the nearest by black hole so it's under way you know it's it says now travel for one light year we'll have a few more days to go the years to go to arrive there but I think it's a wonderful idea that this message is still floating around and I want to play a small clip of the message in that in in Hawking's very characteristic voice we are all time travelers turning together into the future but let us work together to make that future a place we want to visit be brave be determined overcome the odds it can be done thank you very much [Applause]

Channel: Science & Cocktails

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Keywords: science and cocktails, science communication, popular science, science lectures, Science & Cocktails, science talks, Brussels, Flagey, Robbert Dijkgraaf, String theory, Black holes, Quantum gravity, Cosmology, Spacetime, Physics, space, time, dijkgraaf, Strings, theoretical physics, mathematical physics, string, theory, spacetime, SCSTRD26082019ams4WDDqPkfe44Kj7rjjuRNxjzz

Id: 0T--WC4D1C0

Length: 46min 9sec (2769 seconds)

Published: Mon Aug 26 2019

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In the framework of the largest string theory conference in the world, Strings 2019, Science and Cocktails organized a special event at Flagey in Brussels. We were sipping cocktails in the art-deco building with string theorist and science superstar Robbert Dijkgraaf as he told us all about the fundamental laws of Nature. Afterwards, cellist and composer Benjamin Glorieux performed a musical piece together with invited guests especially commissioned for the occasion, while live-video artist Klaas Verpoest accompanied them with his visual magic.

What is string theory? What happens to stuff that falls inside a black hole? What are the fundamental building blocks of space and time? Did Nature have any choice in picking the fundamental laws of physics? What is the role of mathematics in physics?

This talk by professor Robbert Dijkgraaf was recorded on 13 July 2019 at Flagey in Brussels.

[u/laspero]

As an astronomy researcher, string theory is an occupational hazard. As in, people who've watched a few too many discovery channels shows and lectures like this are liable to come up to me and start asking me about that as if it has anything to do with my specific field of research. Then, if I don't have too many thoughts on it beyond "it's all pretty much philosophy at that point", they get kind of pissy about it.

[u/grapesinajar]

Isn't string theory an outlier in physics? I was under the impression it's not doing very well and not widely accepted.

[u/Eastmont]

The first part of the lecture about space-time equaling mass, was excellent. Fascinating. He builds up to the focus on string theory toward the end BUT he really doesn’t go into it with much detail other than to describe what happens when strings approach black holes. Kind of disappointing at the end. Anyhow...Is there mathematical support for String Theory? I mean if there were proofs for it, it sure would dispel all doubt, no? I’m guessing there’s not the mathematical support like there should be. But I don’t know.

[u/Massive-Gas]

TKU for the wonderful presentation

[u/[deleted]]

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