Carlo Rovelli – The Illusion of Time – YPO EDGE 2019

we question is what is time and I guess you'll know what is time right time is the the thing that distinguish now from this morning these are now then wait a moment is another now there's this long sequence of incidents so we can figure out this long sequence this a long line which is time so I I have decided to to make a picture of time it's a long line it's very long so it goes so that's that's a metaphor of how to think about time which I'll use we're here this is a minute ago this morning yesterday here before and so on and so forth right this is the future which is not yet to come but smartly here we're here so actually we're not here anymore it's moved a little bit you keep moving and of course the the future is very different for the past the the past is something we have pictures about with memories we know what happened has happened the future we don't have pictures about it we don't have memories we don't know what happened we know a little bit we can compute compute some things but most of it is completely open the interval from one point of this line to another point of this line we can measure it with clocks the amount of time that passes and crocks advices which are meant to measure all the same interval so the interval between here and here say my talking will be over in 40 minutes or something like that so will be 40 minutes for all of us right all the clocks will go ahead 40 minutes that's a picture of time we have it's a common sequence of instance we are all together moved a little bit we're all together in the in the universe all together the entire universe is in this moment of time and then entire universe is the next moment of time and in some sense it flows it passes and we are passing from one things moving to the past we have memories of it and we go open to the future this is time almost everything I have said is wrong it's factually wrong okay it's wrong in the sense in which we say that to say that the earth is flat is wrong or to say that the earth is still let's move it's wrong we know the earth is not flat is round we know that this does not it's not still it moves it spins nevertheless we can usually think here that the earth is more or less flat if we build a house we don't have to care about the curvature of the earth of the earth and we don't have to care about the fact that the earth is spinning we can easily think the Sun is going up the Sun is going down we know it's not true Sun is staying there we are moving in the same sense everything I've said about time it's true for us in our daily life it's a good way of thinking about time but it's not true at all in the universe at large or if you just make things more precise so what I'm gonna do and these 40 minutes it's tell you exactly why it's wrong what is wrong in this picture of time what do we know about a better picture of time and what we don't yet know and what comes out from this discussion it will see that time is far from being this simple long line with a past different for the future of measure by Krakow together is much more complicated than that and in fact we understand some part of it but not all of it so let me start from I'll at least three completely clearly and this to the facts that show that this picture is wrong and then a couple of hours which we are not sure about but indicates more problem with this picture let me start for the first one in a sense that the easiest one but it's a more surprising one um let's take two two clocks and suppose these are very good clocks these aren't very good clocks this is my grandfather but suppose it were very good okay now they both indicate the same time okay the right time I move one up wait a little bit one two three four I come down if these will clocks good enough the one up stayed up we'll be ahead of the one down this is a fact you cannot check this with these clocks because they're not good enough but today we have in laboratory is very good clocks which are precise in one part in 10 to the 15 one part of 10 to 16 fantastically good clock and this can be measured at the difference of altitude of a few centimeters so 10 20 cent EMS today this experience is done in laboratories others to sort of move a clock up wait a little bit coming down and is ahead from the other one a little bit of course that's why we don't see it right we you go to the mountain you come back and your clock is still in kind with everybody else it isn't it's just it's the distinct distinction is so small that our clock miss it so the amount of time the pass from here to here depends on where you are join the mountains then both where the the earth is less what actually causes this is is it the earth this is a big mass and the the big mass literately slow down time in the sense that clock near it goes slower now just a clock our thinking go slower a flower blossom slower a pendulum as a slower oscillations and so on and so forth okay so time goes a different speed depending on where you are and if you go near a big mass that Jupiter the effect is bigger if you go near a black hole which is a very concentrated max the fact is even bigger so if if I go near if I could go near a black hole which is just issue of money money right so that yeah I mean I I'm a scientist I I don't understand anything about money but you do deal with money and the reason we don't go next to black holes we don't build starships it's not because it's impossible because it's too expensive black hole is coming on us well we don't want darkness we we won't light if we can so if you can keep no no no please okay whatever so now we're in the black hole so if I could go near a black hole okay and stay there ten minutes if I could clear close enough then I move away from the black hole I come back on earth and on earth a century has passed so I it's easy to go to the future you just go near something very heavy wait a little bit and and and you go to the future and you find the children of your children grown up say Oh granddaddy would you do it okay this is not science fiction it as it is in some Hollywood movies or something like that but it's not science fiction is realities we know that the earth is like that we know the realities like that the first to figure this out is of course Albert Einstein a century ago fact this is a completely contained in his theory that was written in 1915 a so same printer and 103 years ago four years ago but you know for longer it was a strange equation of this strange theory nowadays this is measured clearly and cleanly on the in the laboratories which means this lines it's much more complicated in a sense there is a there is a different amount of time from here to here going up or from here to here going down this is already shaking point number two it's a little bit more clear but it's a it's a number of facts we know well which is a following uh I said that the past is completely different from the future is no doubt about that we grow old we don't grow younger however it came as a surprise in the history of physics it started in the back in the eighteen Center in the seventeen eighteenth century but it came more and more clear as long as the basic equation of the Worlds were worked out that in the basic equations of physics there is no distinction between past and future the grammar of nature doesn't know about the past and future now this surprise how is it possible that out of fundamental equations which don't distinguish past future comes out of a reality which seems so different from past future well good thank you we're out of black oh the the key is the realization that is old is a sort of a 19th century realization that every time there is a distinction between past and future there is heat something thermal and what were you thinking about that is that suppose you suppose you have a let's say suppose you have a pendulum and and you look how it moves and you take a movie of it okay the pendulum you take a movie of it and then you project the movie backward you cannot distinguish the fall around the backward okay however if you wait enough after a while by friction it slows down and it stops now if you project the movie backward it doesn't make any sense because all alone is start moving which is absurd so friction breaks the difference between the past and future but friction is what is little heat the energy of the movement the mechanical energy is transformed into heat that's what friction is if you throw a ball it goes forever if you take a movie and and and present projected backwards it moves forever in the other directions but in in our real world there is always reaching and the ball slows down that's again presence of heat breaks the difference between past and future now the point is that the difference between the past and future exists only when there is heat in our brain our folks are entered in our brain there's heat production plants grow and they's Heat going on this heat that makes them grow and so on so unless this heat there's no difference from passive in future okay good so maybe there is something that breaks difference between past and future is just heat but what is heat heat is just the fast movement of the molecules of the atoms which move mechanically but in mechanics is not different to be in the past of the future so where does the difference from the past the future come from well it comes from the fact that when we think about heat we are not thinking about the individual movements of the molecules but we're sort of averaging out right if you the difference between a hot glass of water and a cold glass of water is only that in one case they're moving very fast the molecules and the other they are not and we don't you don't look at the single molecules we are sort of given an approximate a average measurement of the movement by saying it's hot and that's how things feel hot so the difference between the past and the future comes from the fact that we're not looking at the details but we're averaging out and that's quite shocking the deeper repeat the difference between the past of the future comes only from the fact that we're not looking at the tale but we're averaging out it is a fact it was slowly understood by Boltzmann by people like that in the 19th century it has become more and more clear because physicists expected well maybe we're going to discover something that breaks the different to be in the past of the future in the basic equation of physics there isn't so it's a statistical thing it's a perspectival thing is because we don't look at the detail that the past is different for the future but the past is a mostly default for the future right I mean we grow old again we have pictures of the past not to the future well because we do an enormous amount of averaging right in a single glass of water there are an avocado a number of molecules which is a huge number of wonders 10 to the 26 whatever molecules an enormous number of molecules so is in this lack of perception of the details that the difference between the past in the future come out is not a totally clear story if you don't find it clinically is because the scientists don't have it completely clear there is a lot of debate about that but it is a fact that the difference of the past in the future comes only when you zoom out and look at things in sort of a foggy way it depends on the ignorance that we have out the details so in a sense there is an aspect of time which is only due to our ignorance of the details that's point to the difference between that direction and that direction is only in the perspective we have about things 3 and that the third very solid piece of information we have about the world something we know for sure ok but the third one in my opinion is the most shocking discovery of modern physics it also goes back to Einstein but and also took a century for the scientists the community of scientists digested I said that the entire universe is in some point which now has moved here and that's the present and we all have a good idea about the present we are all in the same present right now right not ten minutes ago what that means in the future now now and now something is happening on a distant star now something is happening on a distant galaxy Andromeda or some other galaxy now what do we mean by now has Bettis eyes I see you now you see me now right do we no why no because we know that lights takes on time to travel okay so the time takes light for going for me to you it's short but this is nanosecond a few nanoseconds but it's not zero so you don't see me now you see me how I was few nanoseconds ago and I don't see you now I see you how you were 2 nanoseconds ago and you were far away there I see how you wear several nanoseconds ago and you see me how I was seven us so we don't see each other in the present we see each other a while to face all wrongly so to say so what do we mean we're in the same present okay now this is irrelevant for us because a nanosecond is far below what we perceive nanosecond is nothing right we our brain distinguish badly a few hundreds of seconds a good musician can nanosecond is nothing for us so we can say I see you now you see me now we are in the same now but it's only because of this approximation if I was in Andromeda the light the time lights take to go from Andromeda to here it's millions of years so I when we look at the stars and when we look at the galaxies we see them millions of years ago of course with time light so if I have a friend enough if I'm in Andromeda I call you hello okay a million of years later sort of you you say hello and and I wait to millions of years it's a very long conversation and the notion of now disappears doesn't make anything in fact if you go precisely I don't want to go into the questions in the detail if you want to go precising equations that describe this structure you realize that to define and now it's impossible makes no sense for what we know about the structure of the geometry of space and time which we know well and all the recent discoveries like the measurement of gravitational waves and so forth reinforced our understanding of that if you go into that into the mathematics you see very clearly that there's no sense whatsoever to say what's happening in Andromeda now doesn't mean anything there are in the history of Andromeda there are there is a time which is certainly past us because we can send a message and whatever happened after is past there is a time which is before in the past which is before the moment in which a message was sent which I receive it now here now here which is the past but in between there is a huge interval of time which is neither past nor future which is a sort of super extended present which in Andromeda last millions of years and between me and Eunice just a few nanoseconds travel time of light okay so now is not a good notion in the universe's large there is no point in which we can say the universe now is something now this is a fact it's something we haven't stood very clearly but this is astonishing fact because it means that how we put it what is real what is real what exists today okay the Roman Empire is not really existed in the past so it's real what is existing now but there is no now so what what is real what does it mean to be real well philosophers are discussing that theoretical physicists are discussing that but this has to do with what we mean by real what we mean by existing which becomes more confused so the fact is that the world as a whole is organized in a way such that our clearly intuitive notion of now it's only a little bubble around us which depend on how precise we perceive time if we perceive time up to a nanoseconds it's just a few meter if we perceive time like we do down right or no to a millisecond is the entire season is an in a common now okay but no more no bigger now it's a bubble around us these are the three strongest pieces of evidence very clear I'm talking about established physics not about speculations that indicate that this picture of time time is completely wrong there's more as I said because everything I've said so far disregards Ponte mechanics we know that the world is quantum mechanical and when you fold quantum mechanics in things become even more confusing because clocks in quantum mechanics can be in funny states which are sort of one - superposition of two different states so even locally you can say that between this event and this event the time is not unique the interval is not unique but it's a superposition of different intervals and my job I mean what I've done all my life is try to build a quantum theory of gravity quantum theory of space and time and if you try to do that you try to write equations you have to fold this in and the notion the usual notion of time disappears all together in fact in the equations that I write I a my colleagues right there is no time variable at all if you want to do quantum gravity you forget the notion of time what do you do you do your variables that describe the world the position of this the temperature the height the standard variables you describe the world and you describe how these variables vary with respect to one another and you forget time that's how do quantum gravity so the notion of time is just thrown away I hope I've confused you enough now let's come back okay we have gone deep into this into this disappearance of time now let me come back from this world without time at the quantum gravity level which we don't yet understand well to our usual notion of time because after all like the flat earth right to some approximation the earth is flat so what is approximation where we will cover this idea of time here well it's a it's a long story but to record our notion of time we have to take approximation step by step from fundamental physics to our common reality the first one is forget quantum mechanics quantum mechanical phenomena are small-scale we don't see small scales forget the quantum aspect okay and if you do that you go back to an Einstein picture of space-time which don't have the strange fuzziness but in which time is not a line it depends on where you are in some funny way that's the first approximation the second approximation is that all right time goes the different speed and so on and so forth but space-time where we are is pretty simple we are not near a black hole we are not near a very big mass so this phenomena are very small phenomena I talking about I forget about them good so now we have at least common intervals what about the present well to actually realize that there is not a common present all over the universe you have to be very far and you have to consider the fact that things move one velocity hive a lot possibly high velocity one respect one another if we are close enough and we're not moving zipping around too fast we are sort of all in a common bubble of present so we have our present is a bubble but is still our good present okay what about the direction of time as I said here things are not completely clear I'm a philosopher so discussing physicists are discussing but if you're folding the fact that we don't see the details that the world is made by aliens and zillions and zillions of little teeny things molecules atoms quanta of space photons all these teeny things and we don't see the details from this ignorance come a particular perspective such as the future is different from the past all right it's not totally clear but that's where the origin of the distinction between the past and the present comes from so we sort of understand with some holes how from a fundamentally time the reality we get back to this picture of time but does it really because time it's more than a line time passes what is this flow of time it cannot be in physics because physics doesn't have time fundamental equation physics don't have time where it comes from the time of our experience exponential time as the philosophers call it it's not really the time of physics this is a gap in between where does it come from well it comes from our experience and our experience come from the way we are done from the brain we have we have a complicated brain and we relate to the rest of the world via the the census and the complicated calculation that happen in our brain and what does our brain does well it brings in the information it keeps elaborating it is predicting the future on the basis of the past and anticipate what happened and this is the machine that creates our illusion that is time for us the amount of study today in neuroscience that try to figure out how our brain work is in large quantity focused on this process of sort of producing the future computing the future on the basis of memories if you think for a moment and this is an old observation first of all made by philosophers who certainly has written pages and pages of that but in fact goes back to st. Augustine it's a remarkable observation we know that time flows we know that there is donation how do we know given that in any moment we only have experience of the present how do we know about the past in the future st. Augustine writes when you listen to music suppose you listen to music you hear this the melody how can you hear them elodie given that in any moment you only see one sound one note well the answer is clear because you remember the previous ones not only you remember the previous one but you sort of that's how music work you can anticipate what comes sometimes you're surprised but sometimes you're not surprised and memory music is the core of time right music is the art of is an art that lives on in time it's made by time so it could exist only because there's memory memory and anticipation and our brain is essentially a memory machine memory used to anticipate the future there is a book by a neuroscientist at American ever scientists the title is your brain is a time machine so this means that this image we have of a present a past a future it's not really about how nature is but it's about how our brain works we remember something about the past not much in fact in the past there who knows what's happened we have studied maybe there is a dinosaurs than there there's a big bang there who knows what's there in the future boom knows maybe an atomic war maybe maybe not so it's our memories anticipation what we really mean when we talk about time which is somehow connected to physical time but loosely what we talk when we are talking about time is the product of the activity of our brain made the memory anticipations which add adds to the physical time a lot last point it's still not enough is more in time and I think this is a to me the most interesting aspect of of this story um why did you come listening a lecture of a physicist on the nature of time I mean if it was on the nature of I don't know some chemical interacting with you nobody would come here but time interests us times touches us times is not neutral for us in fact is dramatically not neutral for us first of all because we live in time we can even think about ourself outside time right we could think of ourselves outside space some religions do right you die you're outside space but you still exist but could you think yourself outside time how could you think in not in time so time is structure to the way we are made we are time things end time is attached to our sort of deepest emotion because we lose things because of time passes in fact we lose everything because of time passes in Buddhism in the pillars of Buddhas they said life is sufferance but life is sufferance because of the impound impermanence of things because you're attached to things and thinking things you lose things because time passes so in a sense time is the source of our suffering also our joy times is what bring us things which give us joy the word before so x is not emotionally neutral for us it's very talking to our emotions we know we're gonna die that's quintessential emotion human emotion with respect to time now philosophers who have discussed time from the most extremely different perspective have both made this this observation of how much time is emotionally charged for us you find this observation in Heidegger and you find this service efficient writing back which were philosopher of the most extreme philosophical position of the possible and I think that this is a key observation because the census of passage of time which is created by our brain in this game of memory and expectation is not just a computing machine that does its own is something which is motivate has motives and struggle with the loss that comes with time so I think that the emotional aspect of time is not sort of fog like scientists usually think right forget emotions so you understand it better but if you forget emotions you don't understand time better because this emotional aspect of time is a key aspect of what time is for us in our daily life for us time is yes the time of Einstein yes the time of Newton yes the time of thermodynamics but it's also the time our brain is also the time of our emotions so is this layers this all these layers that makes the complex structure of what we call time and unless we look at all of them we just don't understand what we talk about when we talk about time so time at the end I think the the emotion of time is not the fog that prevents us to understand what time is it's actually to a large extent what time is for us thank ladies and gentlemen we have a few nanoseconds for in the front of here will will bring you a microphone let's the stay apps always longer use mine thank you very much professor rovelli my question is very simple you said that as we go up or down there are there's a difference in time so we have spaceships that don't go to black holes but they do go to Mars they've gone even to the outer solar system and there is communication between the earth and those spaceships my question is is there a difference in time oh yeah definitely is it different than its measured he's absolutely measured yes not only that but you know the the satellites of the GPS the thing we have in our cars to tell us how to drive the machine it works with communication with satellites when the Americans put up the satellite the first the first set of satellites the the the the physicists told engineering of the Pentagon was an army thing careful because time up there goes faster and this the system worked with satellites with clocks in that sort of broadcast the time and them so the fizzy said careful because the clocks they are gonna faster than what you expect here on earth and the engineering said of course so we're gonna keep this in account but since it was an army project the generals of the army the American army when they saw the record said come on time passes I don't believe that so the first system was built this is the 80s was built without keeping this difference of passage of time and it didn't work so the GPS of your car works by taking account the fact that time passes faster there than here thank you very much quick two questions two very quick ones the first one is is time travel possible if so how to achieve that and a second one in the geometry of the universe is there some sort of super position where I as a human could see past present and and future at the same now if that makes sense Star Trek inspired of course um the fifth question is is time travel possible well I mean a cheap answer is our life is a traveling time isn't it yeah I think you wanna know is can we try to travel faster or we come back to the future now to time travel to the future is certainly possible as I said it's just an issue of money it's your business not my business I mean then the questions are clear you want to go to the future you'll build a starship fast enough make a long run come back you'll be in the future coming to the pasture is much harder it's not impossible but it's extremely harder precisely because of this thermodynamics this you have to fight against probability in a sense against a more dynamical probability and let's make it very harder so at present if you ask me and we're gonna be able to travel to the past I would say probably not not because it's intrinsically possible but it goes because we have to work against the the number of molecules which are too many the second question was much more vague we are studying quantum gravity so yes in principle that might be quantum superposition of different timings what this produces in our experience it's not much I think because in our experience quantum phenomena are rapidly washed out because they they in the macroscopic things were sharp quantum phenomena that's why we don't see quantum phenomena in our macroscopic life so um I think they're going to be effect that you can't pick up with very precise measurements and not with with bigger so the microscopic experiential facts take the gentleman in the front row and then the gentleman three seats you're right please yes professor in in quantum physics we go further very large the very very small so and there is a tsunami about entanglement where two particles or two something communicate do they communicate at the speed of light do they communicate in now are they in the same moment of time those two entangled particles there is a lot of confusion about the actual sense in which to entangle particle communicate they don't communicate they definitely don't communicate it's a theorem in in in in quantum theory you cannot use one of the two to send a signal to the other is this equal to no signal is theorem in quantum mechanics they communicate in the sense if you measure something here and measure something here there are some correlations but the only way to check these correlations is to look at both of them so you have to wait for information to come back together so there's no direct communication between the two so the answer is no I mean the the entanglement does not break in any sense the idea that communication cannot go faster the light in fact a lot of current research came out from the effort when entangle was figure out first the scientists are all great let's use it to make faster-than-light communication they were project to the Pentagon and then it became clear that this is impossible it's very subtle the sense in which entanglement it's it's an entanglement between two different systems it's a it's not just that they are connected I had a statement in that a question the statement was right here in the front okay sorry say was I found it ironic as you were saying that there's really no such thing as time that you kept looking at your watch but the question is can you think of a practical application where the the dissociation between our physiological perception of time and the reality of time is there a way of harnessing that into the real world it's it's a very good question let me first mm-hm comment on your observation we that's up okay and that's down and it's very convenient to talk about up and down we know that in the universe of lodged is no up and down okay we understand perfectly well what's happening we sit on a rock there is gravity so up and down are just here relative this does not mean talking about up and down wrong it just warns us that talk about up and down it it's good here and not all over it same with time now your question is very good in fact with a group of medicine psychologists philosophers physicists we put out a big request of money to the European Union to be grant to study exactly this question and we did not get the grant there was a lot of very good people in the requester but I think the referee had a point namely a great idea but yes anything concrete in mind and wouldn't vague ideas but too vague it's like the the gentleman back there this is work oh yeah it does look at that well I've never taken physics I skipped it and I'm not an astrophysicist but you talked about emotional time time may not exist and I'm just wondering how perception fits into that because you know when you're in certain places if it's opera if it's a theoretical then sometimes you're in one place and time goes by really really quick and another time oh my gosh you're in science class but the question is where does that fit into the world because if time is all a theory in your mind then in reality is time actually moving quick when you're really interested in something or is it just you know how do you how does perception fit into that and I don't even know if that's a physicist term or not I'm not sure yes look it in a strange funny way right because in a sense we all know that time goes a different speed that you just gave example so sometimes one hour is fast sometimes when hours is sometimes I will feel shorter than it feels long now however so now we went to school and we were talked all right this is part of your psychology but behind that there is a clear physical structure of time which is measured by clock and is the same for everybody so in a sense what I'm telling you is that yeah that's right but only partially right that clear common structure of time itself is a far from uniquely defined is much more more rich and full of variety so in a sense that the psychological perspective the time flow it's more close to the nature of time than the simple measurement of a clock when we talk about time it's not just as a single single mate it's a single position of the of the hand of a clock and therefore those that seemed funny phenomena to be discarded are more relevant to understanding the nature of time than what seemed the 50 years ago 100 years ago thank you a couple of questions one is does physics explain how you're able to sort of look in your past there are people who can do that and people who have sort of foresight or what's coming up and can tell pretty exactly what's going to happen and then secondly I understand that going back in time may not be physically possible because of chemical reactions and everything else but what about if you could just go back a day and you could sort of correct a mistake that you have made and not not you would like we all would like that so much not sure what what exact which exactly phenomena are you referring to but I think a lot of phenomena like predictions about the future are have been shown totally convincing in my opinion or very largely convincing that they're illusions they're not true you can't predict the future of course theoretical physics is about prediction the future right I can predict the position of Venus tomorrow in the sky very very large in a reliable way but that's not what what you're talking about so I think no I mean the the strange phenomena that we didn't understand are nothing to do with this flexibility of time that physics is making emerge we have one final question over there the gentleman so my my question might be related to the concept of flow which the gentleman back there talked about it it time tends to move differently based on the activity that you're in but it has to do with personality types and how we experience loss of time in terms of longing for time and whether that relates to sort of the impatient personality does that make sense well I'm not a psychologist at all so but I definitely there are individual differences the perception of time I I cannot say more than than that there is an interesting amount of research on different of time the perception of time in different animals right so an animal that has a much faster perception of facts than a second process things much faster than us like a bat that that flies in in fly or an animal or a plant and assuming that the plant has a perception I don't know maybe maybe they don't but imagine an animal that to receive information about the world once every second instead of one every hundreds of seconds as we do would have a completely different sense of the flow of time right if you think we have a very clear idea of how fast time goes right but it doesn't make any sense how fast time goes fine our first respect to what so what when wait what you talk about when we are talking about the speed of the flow of time is our own is the rapidity at which our brain works and the amount of memory that our brain can hold and end and end process so you it depends on the brain it depends on the speeches and presumably depending on the difference experience the different personal psychology Carla we were over here on the right we have one final question request from Carlos yes as a scientist are you an optimist about humanity or not much so I wish it was an optimist but I am NOT I think that humanity is making big mistakes right now because it's increasingly aggressive toward itself it's destroying the planet for real I think that the structure of the planet is more real than what we are told there is a distractor of species as global warming of course and there is belligerence between nations and it seems to me that instead of collaborating we are working against one another and that's unfortunately the direction which our species is going we are too many I am pessimist and I very much hope to be wrong

Channel: YPO

Views: 27,142

Rating: 4.88551 out of 5

Keywords: Carlo Rovelli, YPO EDGE, iot, future, Young Presidents' Organization, Cape Town, technology, artificial intelligence

Id: AumrYDQIuEc

Length: 46min 37sec (2797 seconds)

Published: Fri Mar 08 2019