Your Brain is a Time Machine with Dean Buonomano

Might the human mind be the only place in the universe where time travel is allowed? Coming up on StarTalk. Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk Special Edition. Today we're talking about the time machine of the mind. What does that mean? Well, let's go to my co-host here. Gary, Gary, how you doing, man? I'm good, Neil. We're all back in our man caves remotely, so it's a bit strange for being in your office again. I miss my office. Yeah. At Chuck, Chuck, actor, comedian. Yes, I am. I'm actually not here, guys. I'm in the future. You're in the future of the time machine. I'm in the time machine of my mind. Talking to you from there. Well, you and your producers cooked up this episode and, you know, it needs good ingredients to do the right things for you. So tell me you're thinking. All right, let's put it this way, shall we? Is time an illusion? All right, hold on to that sort for a moment. And from moment to moment, we transport ourselves backwards and forwards in time in our own brains, remembering the past, projecting to the future. But how does that all work? In today's episode, we are going to wrap our heads around time. Well, we're going to try to wrap our heads around time. And time as we know it in physics and how we experience it in our own brains. How do we tell time? Why do we tell time? And finally, is time traveled possible? But only in our minds. Okay, that's the tease. That's a very rich topic that's even been addressed in many a film. And so I'm curious to see how much of that is plausible or just fantasy. So we introduce, oh yes, you know, we're growing our list, our stable of neuroscientists because that's the coolest frontier science out there right now. Oh, yeah. Dean Warnomano, professor of neurobiology and psychology at UCLA, Aklah, as the non-informed folks might call it. Your author of your brain is a time machine, the neuroscience and physics of time. That's what really got us interested in your work. So this, we are delighted to know this. Oh, by the way, Warnomano, we were speaking offline. I would have guessed that meant good hands in Italian that you come from a long line of surgeons and other people who do good things for people. But you disavowed me of this. Yes, we're more on the sketchy side of that. So I think we're mostly on pick pockets. Listen, you got to have some really good hands to be a good pick. Yeah, I mean, I think it's underappreciated exactly. You have never heard a pick pocket saying, oh, I'm off thumbs today. It just doesn't happen. And maybe, maybe Neal's correct, and that there's a connection there that the original pick pockets became surgeons. Yeah, it could make sense. So tell us how, you know, I could talk the physics of time all day, but that's not why we're here. We want to know the neuroscience of time. So tell me how the brain tells time. I wish I knew Neal. No. Why do we have you? Your guess is good as mine. I have a... Give me your graduate student. Give me somebody who knows something. So I think to answer that question, it's helpful to think about man-made clocks. And I think man-made clocks are a bit underappreciated, right? And that through history of civilization, we've been on a quest to make ever better clocks, right, from sundials to water clocks and eventually pendulum clocks and quartz watches to atomic clocks. And today we measure time better than we measure anything else. So even a meter is defined by how far light travels in some specific fraction of a second. So we wouldn't have a good definition of a meter without really good clocks. Now, all these clocks, they can be sophisticated mechanisms, but they rely on a very trivial principle, which is sort of just counting the oscillations of a time base. That time base could be just the swing of a pendulum, the physical vibration of quartz crystals. Something that repeats. Just anything. And repeats. That's all you need for a time base. Something that repeats in a highly regular manner. And we had that in astrophysics because Earth rotates, that repeats. Earth goes around the sun, that repeats. You know, the moon goes around the Earth, that repeats. So we had some built-in repeating things in the universe to start us. And that was the original clock. The sun's going to say that that had to be the original clock. It's like, you know, sun goes up, sun goes down. And then of course, without an understanding of that, you're like, oh, the sun is losing tonight. Night is going to take away the sun. Let's sacrifice some kids. God is tucking in the sun. But the truth is, the sun comes back. Yeah. It's sacrifice something. Yeah. But the principle is very simple, right? Just counting the ticks of some sort of time base. The brain does not work like that. So the brain, unlike these clocks on our wrists, which are amazing devices, right? Because the same device can tell nanoseconds, milliseconds, seconds, minutes, hours, days, and beyond. When I'm snapping my fingers to the right, it takes a certain amount of time to arrive in the right ear and the left ear. It takes approximately a few hundred microseconds more to arrive at the left ear from the right ear. And that's how we use the information, auditor information, to determine the location of objects in three-dimensional space. But you can also tell time, of course, on the circadian time of many of hours and a day. But they're totally different clocks. So the clocks in our brain that are responsible for seconds, they don't have an hour hand. And the circadian clock doesn't have a second hand. So this is fundamentally different from how our man-made clocks are working. And they also, for the most part, don't rely on an oscillator. They rely on dynamics. So the better analogy would be an hourglass. So they're just falling. So you have the laws of physics governing the dynamics of a system. And the brain is the most complex dynamical system we know of. And it has these patterns of activity. And these patterns of activity are what we use to tell time on the time scale of seconds and sort of what you're doing right now, which during this conversation. So the circadian clock is based on the rotation of the Earth. Correct. Well, its goal is to match up with the rotation of the Earth. But it's, of course, based on a biomolecular mechanism. So it's actually has this very sophisticated name called the transcription translation, auto-regulatory feedback loop, which all that means is that DNA makes RNA, which makes proteins. And those proteins inhibit the further synthesis of the DNA. So you have this oscillation that matches the 20, approximately matches the 24-hour rotation of the Earth. And so why is it that site and circadian rhythms seem to be linked in some way? Because what you just said in that oscillation, it would seem like they would not. But we know that blind people sometimes have a drift in their circadian rhythm where there are circadian internal clock. It doesn't also happen when you isolate people away from the day and night cycle. And that their natural cycle is not exactly 24 hours. So that would drift. But basically the same thing is being blinded to a daytime rhythms. Right. Both of those things are true. And of course, so the major, the sort of the master circadian clock, and I want to make that clear, it's just the master circadian clock. Not for a music or anything else, is in the part of the brain called the super chiasmatic nucleus. Wow. The chiasm here refers to the optical nerves that are crossing over. And it's right above. So why is it associated with vision, Chuck? Well, it's because this goes to Gary's question. That's how it's entrained. So if you drift, if you're in a sensory isolation experiment, which people used to do, these people would spend two months in a cave away from light, then you drift little by little. But we use the circadian part, I mean, the visual part to entraine our circadian clock. Here, and to understand why that's important, one of my favorite experiments. A very simple experiment in biology is maybe you know some people who really almost always go to bed early and they have to get up early in the morning. There's something that's sort of this advanced sleep phase syndrome. And this is a mutation in the proteins that underlie the circadian clock. And the circadian clock can have a different period. So maybe it's 24 hours. And one of my favorite experiments, this is not in humans or anything. This is in cyanobacterium. So these are just single cell organisms that like us have a circadian clock. And you might be wondering, why do they need to tell the time? They don't they don't have a schedule to fix to meet, right? And the reason is because they need to know when the sun is going to rise, because they need to engage the protein machinery to start doing photosynthesis. So what they did in this experiment is they get some mutations that had a period, an abnormal period of 22 hours, and another set of cyanobacteria that had a period of 26 hours. So they're both off, but they put them in the incubator in the same p-tree dish. So they're competing with each other for nutrients. One incubator had a period of 22 hours. So it was lights on for 11, lights off for 11. And then the other one, it was 13 on, 13 off. And sure enough, in the 22 hour period incubator, only the cyanobacteria that had the 22 hour clock survive, and because they won out the competition. But when they were in the 26 hour incubator, it was the other mutation that survived. So we need to tell time in order to engage the body, the proteins, and the brain to anticipate changes in our environment. And that's extraordinary, and the valuable. Wow. Look at that. So for us on a biological level, time happens all the way down to a cellular, molecular level. Absolutely on the scale of circadian clocks. Okay. Not for seconds. You're not on the circadian level. You are not going to have cells playing music in, in a baguio or a gravee, right? But for the circadian clock, absolutely. I just, I gotta remind people, because cyanobacteria are very important in the history of life on Earth, because they were the first species to put oxygen into the air. And that enabled animal life to rise up and become everything that it is. What was it before that, Neil? Didn't they kill by putting all the oxygen in the air? Oh, no, yeah. So there are plenty of land life forms that where oxygen would be hostile to their survival. Right. They're all gone. Whatever they were, they're gone. So we owe a lot to cyanobacteria. So I'm delighted that there's this extra research going on. For our saviors. You're not there. I was thinking that's correct. You're a creator. There must be a reason why humankind has evolved to need to tell time. Yeah. And why we throughout history paid so much attention to telling time. Like, why did we spend so much time early on trying to develop clocks, right? And in many ways, as Neil certainly know, there's a very tight coupling between the early days of physics and astrophysics and astronomy and clocks, right? Yeah. I've got Galileo, my favorite Galileo stories. I mean, he basically first demonstrated that why a pendulum would make a good time keeping device, because he was in church one day. And it must have been the summertime because windows were open and there was a breeze. And he was bored to Catholic ceremonies. No, that makes sense. So the breeze was coming in and the chandelier was swinging and not paying attention to the utterances of the priest. He's watching it. And he noted that when it was swinging wide or when it was swinging narrow, it took the same amount of time to complete a swing. And how did he know this? He checked it against his pulse. And so assuming he wasn't getting excited during this moment, that's as good a timekeeping thing as you could have on your own out there. And so he concluded that a pendulum within limits, if it's swinging slowly or swings a little bit or a lot, it's the same period. If that's the case, you can put pendulum in clocks. And that'll be a sort of a self-regulating mechanism. That's my favorite, just a curious scientist who's bored and just makes a discovery. That had to be the worst homily ever. My God, it was well timed. But to go back to Gary's question, imagine what life would be if we couldn't anticipate what was about to happen. How would you know be able to interact with each other? And how would you be able to catch a prey, catch a predator, avoid a prey or avoid a predator? But just to show you the importance of time in culture and society, we talk about the industrial revolution. And the steam engine was sort of the, if you will, the engine of that advance. But in many ways, other people have argued that the real engine of the industrial revolution were cheap clocks, because that's when we started having factories. You have a factory, you need to synchronize human behavior. You need to get everybody at the factory at the same time. I thought that's what coffee did for everyone. That helps. That's certainly not. But it doesn't, it gets people hyped up, but not necessarily in synchrony. So without that ability to synchronize things, then we wouldn't really have the industrial revolution, because you had to synchronize those factories, because we needed to work together. And we've always needed to work together. So cooperation in many ways requires timing. As you know, you might know from, here's another football or soccer analogy there, people synchronize their movements together. So if when people are clapping, whether it's at a sporting event or in a concert, we naturally synchronize our movements. So we're incredibly attuned to each other's actions, and we use our internal clocks in order to achieve that. And then of course, with Einstein, then of course, a lot of that initial goals in terms of synchronizing clocks was due to train schedules, right? They need to synchronize train schedules in different parts of Europe. And that was another fundamental breakthrough for the economy that couldn't happen without reliable clocks. Especially since train schedules are not every city at the top of the hour. It took 33 minutes to get between these two points. So you want to be on the track, 33 minutes after the hour. I want to just close the point on the pendulum clock. So Agalale noticed this about the pendulum, but he's not credited with inventing the pendulum clock. There would be Christian Huygens. Huygens. Huygens. Huygens. In fact, there's a probe named after him that landed on Saturn's moon, Titan, called the Huygens probe made by the Europeans. That's just an aside. Anyhow, he published a book called, Harvard Logium Oscillatorium, I think was the name of that. And in there is a full discussion of time keeping via pendulums. And so, yeah, things we just take for granted, or even discard, we're major advances in our attempt to keep time. And that's getting back to answering your question, Chuck. Humans figured out that this is a good thing to know how to do. And then you could do other things as a group, rather than being the lone wolf out there. So basically, HR is... HR. It's HR. Because we need to be able to write you up for being late. That's what this is about. Yeah, punch him a clock? Right. You, that's it. Right there. It's all about the punch clock. I'm Oleg Hanemaraj, and I support Star Talk on Patreon. This is Star Talk with Neil deGrasse Tyson. How thin were we sensing, feeling time without the addition of clocks? Because we're not perceiving it second by second, or are we? Does it flow? Is it something? Is it... And can I add to that, are we... Where are we? And we're talking about, of course, earlier man, because we know how we sense time now. We don't really need to sense it. We just look at our wrist or our phones or whatever. We don't give a damn. But back then, what Gary just said, were we really sensing it? Or were we looking for environmental tells to alert us? Oh, interesting. Yeah. From the outside or from within? Was it from within, or was it really our environment that was kind of saying? And then also just one last point to put on top of Gary's point, did the repetition of that environmental tell, then become inculcated or incorporated within our sensory perception? In evolutionarily. Of evolutionarily, yeah. And that might be a lot. Maybe I'm way off base here, but you know. So let me just be clear here. All mammals, so with a developed vertebra and nervous system, tell time. And it's absolutely important on the scale that we're talking about for interaction with each other. And then you think about something like language, right? So language is very temporal. And here's one of my favorite examples. I want to say two sentences. The order of the words is the same, but the meaning is different. So they gave her cat food or they gave her... Wait, you guys anticipate. You guys are well ahead of the thing. You guys are way ahead of the game. That's because we're smart. We've got everything. We've got everything. They gave her cat food or they gave her cat food. So there, it's you're naturally paying attention to the timing and the intervals. And that's altering your communication. And it's totally unconscious, right? You're not thinking, oh, the pause was different. So that timing is always going on. Now Gary's original question was perception of time. That often means the conscious perception of the flow of time, which is a very deep philosophical question. That implies consciousness. So one of the most salient percepts that we have is that time is always flowing. And this reaches at the core of something that has tension with physics and neuroscience that I've written about. And I sure, sure, you have talked about. So the flow of time implies some self-awareness of an arrow of time, correct? Yes, generally the case because it's generally flying forwards. Yeah, I would say that's correct. From the past to the future. But in there, if I see someone in my family and I see them get old and die, does my self-awareness that maybe I'll get old and die too is that part of my sense of the flow of time? Yeah, that's a great question. I want to come back to that specific point about death. But first, in terms of the perception of time, so many physicists would argue that the perception of time, the flow of time, that the past is no longer real. The present is real and the future is not yet real, is an illusion or a mental construct or something imposed by the brain. And this is the debate between what we call it, journalism or the block universe and presentism. So under journalism, the past, present, future are equally real. And under presentism only the present is real. And that's how we perceive. And this is the fundamental debate about what's the nature of time. And there's this ongoing debate where the physicists say, hey, you neuroscientists figure this out because obviously time is not flowing. Why does it feel like it's flowing? And then the neuroscientists say, well, you physicists figure this out because time is flowing. But the point's linked physics. And then the physics, and it will be interesting to hear all of your opinions. But the physics is really most of the interpretation in which, because of relativity, because the physics doesn't have a specific point. You are here, doesn't say there's anything special over here. The equations of physics are time symmetric or time reversible. So that leads to one interpretation that the past, present, and future are equally real, much like space. Can you can be anywhere in space? You can be any moment in time. But I've argued and that I think the brain is telling us something true about the physical universe that it is because we evolved, survive in a universe governed by the laws of physics, in a mezoscopic part of that universe. Not at the micro, not at the cosmobot at the mezoscopic level, to survive in this world governed by the laws of physics. So I think and have argued that it is really flowing. And our brain creates this conscious perception of the flow because it's a real part of what we experience, and of the universe. That's a cool new word for me, mezoscopic. Yeah, we would say macroscopic, microscope. You don't need a microscope to see it. But mezoscopic is, seems, feels a little more authentic, like mezzo being middle. Yeah, yeah. Dean, we've created memories, right? So that's our understanding, some timing. And I can travel backwards in my mind and revisit memories. I am present in the now, but I can throw myself forward with an imagination of what might be in next time going forward. So as the physics of that, as opposed to the neuroscience of that, how do we interpret and are we actually time traveling? Because we experience time dilation when we dream. I mean, your dream will last 30 seconds, and it will feel like you've been in there for half an hour. That's the whole plot line of the movie inception. Oh, I never saw that. Was it dead? Yeah, yeah. You go, I think that was the movie where everyone, you can go inside of someone else's dream. And but the timing of it, the dream is way longer than the actual time frame. If you do this a few times in, then, you know, it's a fraction of a second equals days or something. And you have to budget for that as they go in and out of each other's dream. So what? I only saw the spoof one, Rick and Morty. Okay. Fair enough. So are we now, if we're in the physics looking at this, is this a quantum state, or and then how does the neuroscience figure this out from their angle of approach? So I think it would be best to start that by looking at the neuroscience before we get to the physics. Okay. So one of the unique things about human cognition, one thing that distinguishes us from most other animals is our ability to do it exactly what you're saying, and Gary, which is engage in what we'll call mental time travel, mental time travel, which is, you know, you think of something as fundamental as the invention of agriculture, right? For some, it's not that complicated, right? Planticide, reap the benefits later. But evaded, evades most other animals, and it evades the ability for of humans to figure that out for many years. And it involves mental time travelers. Says, yeah, I have to do something now that will only give me benefits months or years into the future. And that's, that was a very hard step for us to connect to the temporal dots between things that are cause and effect over weeks, months, and years. As an immediate cause and effect would be obvious. Absolutely. You punch somebody in the face and they, they're hurting and they punch you back. That's an immediate response. They know who to blame. They know who to blame. Seed in the ground. Oh my gosh. This ability to jump, make these cognitive leaps across time is an incredibly sophisticated thing we do. But we're still not very good at it. And that's a problem, right? Because, you know, climate change, you know, we're not acting, right? We're saving for our time. But I go back and I think about the first ancestors that had that ability to look into the future. And this goes back to what Neil said. Can you imagine what it was like for the first human to make this cognitive leap and say, oh, shit, I'm going to die, right? Because it's this ability to engage in mental time travel that we became aware of death. And many people have argued that there was a co-evolution between our ability to engage in mental time travel and religion. Because religion was the antidote to this vision that we saw that we were going to die. So it said, well, don't worry. There's another life after this. And there's a great quote by Jorge Luis Borges that says, except for man, all animals are immortal for their ignorant of death. I don't know if that's true, but it has to go. That's a great quote. And it is not fully true. Yeah. Yeah. Yeah. So with respect to looking into the future, though, I look in my backyard and I see squirrels going, frickin' nuts. No pun intended. In the fall, hiding food. Because they know that food won't be there. Is that not also a form of looking into the future? Okay. Or is it blind instinct? Yes. So that's probably the answer, Neil, is that they're programmed to do that. So a squirrel that never experienced a winter will still do the same thing. But not only that, Chuck. Interesting. Let's get to this, Chuck. Humans have been known to engage in future oriented activities without necessarily thinking what will happen in nine months into the future. Yeah, that's called screwing. That's right. Why would they do that? You left that for our imagination, Chuck. Oh, I'm sorry. He was standing up so he didn't, no one had to say that. Well, I said it for the kids. Thank you, Chuck. But the point is, is that the squirrels are probably engaging in that activity because it brings them pleasure at that moment in time. So we've been talking about memory, like it's just a thing, like memory on your computer. But our brains are of course organic tissue with chemicals and electrical synapses. And so how is a memory actually stored? Can we just lay some foundation there? Yeah. So one of the most fundamental tenets in neuroscience and one that has been borrowed by artificial intelligence, by the way, is that information and memory is stored by changes in the coefficient or the weight or the strength of the connection between neurons or artificial units. So, you know, we use these large language models and how they store information is by just tuning billions and billions and billions of weights. And all those weights are, is how much each neuron influences the other. So if I'm one neuron and Chuck is another neuron, we can change the strength of the connection between those. And then it will behave differently and learn. And this is very fundamentally different from what Neil referred to in terms of a computer memory. So in a computer memory, there's a very clear dichotomy between the memory and the computations being performed. So there's the CPU and there's the RAM. And this is the standard volume and so-called volume and architecture. In the brain, that distinction doesn't make as much sense, because it's the activity flowing through these networks that is both the computation and the memory. So it's extraordinarily hard to separate those two things in the case of human memory. Ooh, wow. That's really, that's, that's very cool. So I've read some connections between this discussion and Morse code. How do they relate at all? Well, so there's two aspects to Morse code, right? One is understanding code and one is the timing. So they're both valid questions. But the memory part is sort of not that different, whether you're doing Morse code or you're doing normal language or you're reading, you have to store information. But the timing is unique in Morse code, right? Because there in Morse code, everything's the duration of the dot or the dash and the interval between them. So how does the brain do that? So this gets to Gary's original question is how the brain tells time on this scale. And that's been a mystery. It used to be thought it was due to oscillations, but our work and other people's work has shown that that's probably not the case. As more to do with neural dynamics. So imagine, you know, we're a bunch of neurons and I'm neuron that activates chalk and chalk activates Gary and Gary activates Neil. So that forms a dynamical system. It forms a trajectory in neural space and that you could use that to tell time. So depending on who's active, so Neil might be the last one to be active. So if we know if he's active, he's firing, that means that one second has passed. And if chalk, maybe that's 500 milliseconds. So the brain is this dynamical system and these patterns of activity can become a clock, if you will. Holy moly. That is fascinating. So these now, there's a saying, neurons that fire together, wire together. That's what's saying. Would you get the saying in the hood? What the hell? This is not in the hood, man. This is not in the hood, man. Yeah, you've been hanging out, Chuck. That's what's saying. That's hilarious. So what I'm wondering is when you think about this dynamic grouping, could you then change, could your brain either falter and fail with these groupings because of misfiring or could you change it in some way purposely because you get these neural pathways to kind of line up and fire together? So that's a really great question, Chuck. And it relates to what you just described. Neurons that fired wire together is called the form of hebbian plasticity. It's a cost of associative plasticity named after a famous Canadian psychologist, Donald Hebb. And that was sort of the original algorithm that how do neurons figure out who to wire together? And it's a very powerful algorithm. And it says that if I see your face, my visual neurons are firing at the same time, my auditory neurons might be hearing your name. So maybe it's a good idea that those auditory neurons and visual neurons hook up with each other because then I can now see your face and then recall your name. So it's a very, very powerful, simple algorithm, they call the associative synaptic plasticity. But back to the timing, you also have this ability to generate sequences. So if I say A, B, C, D, you predict what's going to happen. Or in music, if I go, t t t t t t t t t t t t t t t you can also fill that in. So there you need to not only just fill what's happening together, but what's about to happen. So that requires another rule on top of this idea that associative, that neurons that wire together, fire together might be that neurons that fire first, wire to the neurons that fire second. So there's all these levels of different algorithms on top of each other, but you're exactly right. So this brings a question because so much of when any of us learned about the brain, it was, well, this section of the brain is language and this is facial recognition. So this is a very spatially mapped. And most of this conversation just now is a temporal mapping of the brain, which is a whole other dimension here. The space time of the brain, this time thing all feels very fresh and new to me. Yeah, I agree. The new in your field. It absolutely is, Neil. And I'll make the point that I think time is at the center of a perfect storm of scientific problems from free will, consciousness, determinism, how the brain works, even AI, and the more fundamental question of the nature of time. So I think time is complicated, more complicated than space. What do I mean by that? That's a bit hand-wavy, right? But what was probably the first field of modern science? I would argue that the first field of modern science was probably geometry, right? There's not many things discovered 3,000 years ago that we still teach in school, like Pythagoras theorem. So why was geometry the first field of modern science? It has no time. Geometry, as originally developed, was timeless. It's static. It's not changing. It really took 2,000 years and the likes of Galileo, Galileo, Newton, and Lidnitz to really bring in time and dynamics and add space, and sorry, add time to space. So, and I think neuroscience is in many ways at that same stage where they've we've ignored time and we're just maturing enough to start addressing these complex questions, pertaining to time. You know, I can add to that that the syllabus sequence in physics matches closely how this actually got discovered. So simple, like you said, geometry, there's no time to mention in any geometric calculation at all, right? And so you move forward, there's not in trigonometry either or in algebra that physics has to come in. And early physics, time was kind of simple. You know, you go, you move this far for three seconds and then you turn left and you go another 10 seconds later on. And this, I remembered this like it's yesterday. When we finally had these functions that changed over time. So it wasn't just a force pushing, it was a force that changed over time. We had to track that. And this involved differential equations. A whole other layer of math had to go on top of the math we were previously using. And that's really what separated, you know, if you were going to drop out of physics, that's when it was going to happen, typically. And without calculus, we wouldn't really be able to deal with time to the degree that we need to. And that's the foundation of modern science of the economy and technology and so forth. And there you go with Leedon and Newton, the two. So I was going to call them fathers of time, but their parents have time. So, D, we have something called a temporal window of integration. Now, correct me if I'm wrong here. So if I'm talking to you personally, face to face, I will see your lips move before I hear the sound that you make, right? Yeah. And the brain fixes it. Yeah. So is this now on the illusion of time? Wait, and is that because the light signals to your brain are processed faster than the auditory signals? So there's two things there. So let me just to make sure we don't confuse them. So obviously, because light travels faster, a lot faster than sound, I see the your lips moving, reach my retina more rapidly than the sound reaches my ear. But, and this is the tricky part, the sound processing is actually much quicker. So if I, if you see me clap and I ask you to react to the sound or to the spit or to the site, your reaction time is actually quicker to the sound. So they say ping pong players, I'm not sure this is true. So I'll, they say ping pong players sometimes react to the sound of the ball before they see the ball because the brain processes auditory information. And that's because the retina is incredibly slow. The retina is relies on biochemical reactions. And so, but we do have a window of integration. So whether you're sitting in the cheap seats in a soccer stadium or the expensive seats, we can adjust this window of integration. So it's adaptive. We can tune it so that we're, if you're watching a movie of close or far, it seems everything's integrated. As long as it's in a window of two or three or four hundred milliseconds, your brain can fix it. So in that sense, it's just your brain being flexible and sort of trying to align time and space. And this is something, I don't know if you know what the McGurk illusion is. The McGurk illusion is if I say, ba, ba, ba, ba, but you see a video of me saying, gaga, gaga, gaga, your brain mixes those things and you might hear something like, da, da, da, da, da, because you're mixing audio and visual in your brain all the time, whether that's time or space. So yes, this window of integration is extremely important, but adaptive. The brain fixes it for you like magic. It's like like the editing programs you guys will use for this podcast. So actually we're all in one big kung fu theater movie from all schools Saturday afternoon. Just like, so you kill my master. So that was great example, Chuck, because those are so bad, it's unfixable. I mean, the bringing can't deal with that degree of messing up in the kung fu movies. That's exactly right. I like the imitation though. How about Einstein's general relativity? Where time slows down depending on the proximity of objects? Yeah, but it's, it's, it's, it's never slows down for you. You just always have your time. And it's all happening to everybody else. And you only know it's happening to everybody else because you're measuring it. So that's not a neuroscience. So I don't, you guys might think about that team, but I don't care. However slow you think I'm moving, my pulse is still doing 70 beats a second. And I'm listening to my music. So you're the one with the problem. So the time is different for us. Well, different places, different. Yeah, for gravity, for speed. All matter of things can, can famously shown in that scene in the movie interstellar, where the astronauts go down to the gargantuan planet. Yeah. You're a black hole. And the black hole slows down the time, but you're there with them. And they're just living there 15 minutes of time. And they get back to the spaceship. And the guys got gray hair. Yeah, of course, it's the black dude they left up there to get all old. They get back. He's just like, oh my god. Where you pan? It was the black guy. Sync that with the hour of time. If there's this distortion going on and it's a flow forward. Well, both would be flowing forward. But as Neil said, you would never know that time is slow for you. You're incapable of knowing if it's faster. So only when you, the problem is is when you try to sync between two people and different, these different frames of references, that becomes a problem and raises paradox. But this relativity brings this question that we started off to is, is the past, present and future equally real, a term, journalism or not? And this has extremely important consequences for Hollywood. Because, you know, we, as I think Neil said, you know, we, is this, is that pure fiction that you could time travel in real physical space or not? And a presentist like myself would argue, no, it's absolutely impossible. And an eternalist would argue, it's at least theoretically possible. Well, okay. But then you have cause and effect issues with that. So Dean, famously in the film Total Recall, and Chuck, who is in Total Recall? That is, that is. I think he's a little more literate than that. That's what I do it. But having trouble recalling. In the film Total Recall, which is surely on every neuroscientist bucket list, to watch, they just implant your vacation in your head. And it's a memory that you never experienced. And of course, this also hints at everything that happened in the matrix, where everything is just implanted. And so many episodes of the Brilliant Hit series on Netflix called Black Mirror involve people uploading their memories, downloading them, replaying them. And so, where do you think the future of this is? And how real are those portrayals of your field? Yeah. I think that's a great question. And I think a lot of that relies on sort of a simplistic understanding of the brain as a computer that you can somehow hook it up to an external device. And you know, this is a very topical issue, right? Because companies that use brain machine interfaces, most famously neural links, the musk company are attempting to do this. And I think some people have the idea that, yes, if we have all these wires into my brain and they're hooked up to a computer that we will be able to, I'll all of a sudden be able to speak, Mandarin, or I'll be able to fly a plane. I don't think I know kung fu. Or no kung fu. Or importantly. And then I'm very skeptical of those notions because I think they don't really capture how the brain actually works. Because as I was saying before, the brain is not like a volume in computer, which has a memory module and it has a CPU module and it has a bus module that you can upload things. There's no clear separation between the memory and the computation. So I think you'd have to really modify how our brains work to upload things. So somebody might say, well, all you're doing is just interfacing the brain directly with these external computers. So then I can fly, can fly a plane or do kung fu. But really, it's not me that's doing it. It's the computer that's doing it. So you're just changing the interface. And the brain already has some pretty nice interface, right? They're called eyes and ears and hands. And the brain is very slow bandwidth. So I don't think we can dramatically enhance the bandwidth by magically implanting a million electrodes in our brain. So I'm skeptical of this. And you're probably familiar with Ray Kurzweil's arguments too that will achieve the singularity by melding with an AI. I think that really misses our isn't consistent with our understanding of neuroscience at this point. In my opinion, Neil. That's insightful for you to mention that if you plug into all these wires and then you know kung fu, it's really the wires that new kung fu it's just feeding you that information. Is it really you at that point? It's no, it's the AI that's doing it. Yeah, but kind of sink your lips to your speech. That's what's really important. You should all suck on that. So Dean, before we wrap this up and I think we will be shortly, is it actually possible that the brain is the only time machine that physics will allow? So the answer to that question in my mind, the answer to that question is yes. Because as a presentist, I don't think time travel and physics is a possibility. So when people look at things like wormholes and from general relativity, what general relativity says is that wormholes are a theoretical possibility. They're not really a prediction of general relativity. It says, well, it could happen depending on the assumptions that go into the equations, the initial conditions and so forth. But I would argue that yes, the closest we'll ever get to a time machine is our mental time travel. And that in my opinion, actual time travel is a theoretical impossibility. I understand maybe Neil disagrees, maybe doesn't. I don't know. You're a good company with Stephen Hawking, who as much as he would have welcomed time travel. In fact, he hosted a party for future time travelers where it was... And nobody showed up. He chose a date, time and a date. Is it anyone from the future who can time travel show up now and then nobody showed up? So he advanced something called the time travel prevention conjecture. It sounds like that if it's not exactly that sequence of words, where he's suggesting that one day we will discover a formal law of physics that prevents the time travel, which then prevents the paradoxes that have been such fertile content for time travel movies. And my last question to you, sir, professor, is... I have my answer on this, but I want to hear it from like a real neuroscientist. Do you think the human brain is smart enough to figure out the universe? Or is the human brain smart enough to figure itself out? Okay. Bam! So first place, neuroscience is the most recursive field in science, right? Because it's the only field in which the thing being studied is doing the studying. So that's a problem. There's reasons to... It's a fear. It gives me job security. But put it this way, there may be reasons to believe that no system is capable of understanding itself. So I happen to think that we might be able to pull it off, but maybe with AI to answer Neil's question, we might be able to understand ourselves. But his first point was understand the universe. And I think this is a bit of a trick question that what does it mean by understand? But the answer to your question very informally, I would probably say no in one way, and that quantum mechanics is a good example. Do we understand quantum mechanics? I don't. You would just calculate. Yeah, that's exactly right. So... Shut up and calculate. So the brain has serious constraints. It has serious bugs, it has cognitive limitations. The greatest debugging device we ever invented is called mathematics. Because mathematics allows us to simulate, to model, to capture things we don't understand. So as Neil... Oh, I understand intuitively, right? Yes, exactly. Exactly, exactly. So if you mean understanding intuitively, I don't think, you know, most of the interpretations in quantum mechanics are... I do think are basically revolve around limitations of the human brain. Yeah. So I... I don't know. I think I was a little on the fence, but you pulled me back onto your side. I was always on your side, because I think we're stupid. I mean... Yeah, so I spoke Chuck to go along those lines, you know, there's this debate in AI, whether AI is as smart as human beings are, but human beings are pretty low bar. Exactly. I'm with you, 100%. Yeah. Like, right. So, listen, Professor, this is... I've enjoyed this conversation. You sound like you're like totally in it, and we might want to reach back to you to see what your next scores are on the human brain, and what we can accomplish with it. Oh, when did your book come out? This has been out a while. This came out in 2017. 2017. But I'm going to give you this little title again. Your brain is a time machine, the neuroscience and physics of time. Love it. Love it. It's been a great pleasure, so thank you, Neil Chuck and Gary. You're welcome. You've got it. Well, this has been yet another installment of StarTalk's Special Edition, and we love in these neuroscience interviews. Gary, Chuck, always good to have you. Pleasure, Professor. One no-man. You're on our roll of decks now, so don't be surprised if we call on you again. Neil, the grass Tyson, you're a personal astrophysicist. As always, keep looking.