David Eagleman - Is Time Real?

David one of my obsessions is to understand the nature of reality sounds crazy but time is one of the most fundamental aspects to understand and most of my physicists and philosopher friends are now saying that time is really not real that it's uh that it emerges from something more fundamental and it's a very interesting physics that that's behind it but I'm wondering if there is a different view that we can take from Neuroscience from psychophysics to understand the human perception so that we can understand what the physicists say their equations are saying but understand how we're experiencing it as well and see what kind of correlations make sense here's what Neuroscience tells us is that time isn't what we once thought it was so this much we know that we're not passively tracking the river of time but instead the brain is actively constructing it and here's how we know that so in my laboratory for example I can make you think that something lasted longer or shorter in duration than it actually did is measured by a clock or I can make you think that something came before something else even though it was the other way around or I can make you think that something is flickering at a very different rate than it actually is so I can do all these experiments in the laboratory and what that means is your brain and my brain might look at the same thing and just depending on how I set things up we can see completely different things so what does that mean it means time is is not Newton's time where it's the T in the equation that just moves forward and then everything else can be hung on that so Einstein of course came after Newton and said look depending on your frame of reference things can get stretched or squished depending on how fast you're going but it's a lot worse than that there's a neural relativity going on so what does it tell us about outside objective time well it's hard to say at minimum it means that it's it can run differently than subjective time at most it means that maybe the whole thing is illusory maybe the whole thing is a construction of the brain in the same way that colors don't actually exist in the outside world all you have is electromagnetic radiation of different wavelengths and your brain constructs color maybe the brain constructs time and there's no such thing as that now of course that's completely bizarre for us to try to wrap our heads around but this is the sense in which time might be one of the most stubborn psychological filters by which we're experiencing the world and and it's hard to reach behind that just just in the same way that it's hard to imagine that there's only electromagnetic radiation and not real light in the world right I mean you're just as a your brain is is locked in darkness inside your skull your brain doesn't see it doesn't experience light or photons itself it only gets conversions into electrical signals of photons and it literally lights up the world and you see this whole thing here okay so they're really two two issues here one is what happens in the outside world and one what happens in the inside world what you're saying for sure is that the inside world the subjective sense of time is flexible it's there's a lot of plasticity to it because of how other things happen in our in our heads right there's no doubt about that we may have doubts about what's happening in the outside world we have no doubt internally that that we will have different senses of time exactly okay so um does that though tell us anything about the outside world it tells us our position we have to be weary of our perceptions but but maybe we we then can accept equations but not worry and be just eliminate our own perception there there's no there's no sort of final killer thing that are our perception of time in the Neuroscience laboratory tells us about the physics it doesn't answer the question once and for all it does illustrate very deeply though that we have these psychological filters that we take as intuitive and we know that physicists being humans build their theories on top of our our intuitions right and so the whole notion of time this has been a debate for a very long time whether time actually exists or not and and this at least gives us the sense that we can't assume time is sort of a categorical fundamental thing in the outside world we can't make that assumption with the same um you know Freedom that we used to we know that there's something really strange going on physicists and philosophers talk in time in many different ways one of the ways they categorize in three ways one is that time has a uh has a a now and it has a now to us and nobody knows how long this now is because our memories retain what we had from a few seconds ago and we sort of know what we're going to see and I can't tell you whether my now with you is one second long or a hundredth or a thousandth of a second long because it's all when I look at it it's already gone and I'm on to the next one so there's the question of now there's the question of the flow of time that we sense we have this movement and then there's an arrow of time that sense that I'm going from the past and through this unusual now whatever that is and I'm going into the future so on these three dimensions uh what do we learn from Neuroscience about the arrow of time nothing but about the now there's some really extraordinary things that we've learned so here's what I've put together over the last 11 years um the challenge of the brain is that it's picking up information through very different senses so sight and hearing and touch all of these process information in very different ways with different architectures inside the brain and at different speeds and so what that means is when I knock on the table I see it and I feel it and I hear it all at the same time it seems but in fact those signals are going getting processed at totally different speeds in different parts of my brain and the challenge for the brain is it has to put those all together has to collect up all the signals compare those across the senses stitch them together figure out what happened in time and then serve up a conscious story about what happened by the time that happens I'm living in the past when I think the moment now occurs it's already happened a long time ago actually probably about half a second ago so one thing that's very clear is that even though we feel like we're experiencing things as they happen we're not and um uh I wrote a paper in science in the year 2000 that showed that if if an event happens in time what we think happened in that moment is actually influenced by information that happened after that things that happened in the future of the event influence what we think we saw at the time of the event and it's because information is still pouring in and getting congealed and new information manipulates that what uh how long in the future do you have it's about 100 milliseconds a tenth of a second so something happening within a tenth of a second after an event can make you change what you thought that event was precisely and you think you're seeing the event now but it's already happened a long time ago well one of the things that that really shocked me when you understand how the nervous system works and you think you understand it and then you learn that in terms of Senses coming into the brain that there's more brain of fibers going from the cerebral cortex down to lower centers relay stations for the centers then information coming up I mean that superficially seems bizarre that's right that's exactly right so if you take the visual system as an example you have cells from the red and then going to the what's called lateral geniculate nucleus and then that goes to visual cortex and so you've got a certain number of fibers running from algae and the cortex and 10 times more coming from the cortex to the LG times that's unbelievable here's here's the thing it's exactly what you would expect from a system that's actually all about internally generated activity that has expectations about what it's going to see next and all you're actually passing up the line is did I get my prediction right so it's all about saying okay I'm in a room I'm looking at Robert I think this is what's approximately happening and if suddenly you turn into a flower then I'd send up a big error signal to the rest of my visual system but as long as things are about what I thought they were I don't have to send up a lot of stuff yeah and that how does that affect our sense of time ah well the general story is you have to cross vast Landscapes of brain territory in order to get your story together or get stuff going and something I realized a while ago which really surprised me is if I touch your toe and your nose at the same time you'll feel those are simultaneous well that's bizarre because the signals from your nose reach your brain very quickly and from your toe it has to climb all the way up your spinal cord so somehow when your brain detects the signals from the nose it's as though it says okay well I'm not going to perceive this yet until I see what else is coming up the pipeline and it does it and what that means is that it might be that the that the amount you live in the past depends on how tall you are it depends on how long it takes for all your brain signals to come together

Channel: Closer To Truth

Views: 125,861

Keywords: closer to truth, robert lawrence kuhn, David Eagleman, Is Time Real, Why Anything, Space-time

Id: G4ihCsAPPXQ

Length: 9min 13sec (553 seconds)

Published: Sun Nov 20 2022