1 00:00:05,160 --> 00:00:10,600 Speaker 1: Do we experience gaps in time? Is your consciousness like 2 00:00:10,760 --> 00:00:14,880 Speaker 1: a flame that continually goes out and then gets reignited. 3 00:00:15,600 --> 00:00:19,119 Speaker 1: Why can you see someone else's eyes move but you 4 00:00:19,200 --> 00:00:22,720 Speaker 1: can never see your own eyes move in the mirror? 5 00:00:23,360 --> 00:00:26,200 Speaker 1: The answer is some freaky stuff that's going to shift 6 00:00:26,239 --> 00:00:29,160 Speaker 1: your view of reality. And what does any of this 7 00:00:29,240 --> 00:00:33,360 Speaker 1: have to do with deep sleep or anesthesia or comas 8 00:00:33,600 --> 00:00:38,239 Speaker 1: or amnesia, empires of soft bodied creatures that might have 9 00:00:38,360 --> 00:00:42,400 Speaker 1: come before us, and what you do or don't remember 10 00:00:42,600 --> 00:00:49,839 Speaker 1: about your life. Welcome to Inner Cosmos with me David Eagleman. 11 00:00:50,000 --> 00:00:52,879 Speaker 1: I'm a neuroscientist and author at Stanford and in these 12 00:00:52,920 --> 00:00:57,080 Speaker 1: episodes we sail deeply into our three pound universe to 13 00:00:57,200 --> 00:01:00,840 Speaker 1: understand why and how our lives look the way they do. 14 00:01:17,200 --> 00:01:22,319 Speaker 1: Today's episode is about gaps in time. It's about the 15 00:01:22,600 --> 00:01:26,640 Speaker 1: narrative that we have about what just happened in the world, 16 00:01:27,120 --> 00:01:31,679 Speaker 1: and what happens when chunks of time disappear. When do 17 00:01:31,760 --> 00:01:34,880 Speaker 1: we notice, when do we care? And what does this 18 00:01:34,959 --> 00:01:37,360 Speaker 1: mean at a very deep level in terms of what 19 00:01:37,560 --> 00:01:41,720 Speaker 1: time is for us. I'm going to unpack this mystery 20 00:01:41,760 --> 00:01:46,039 Speaker 1: today by telling the story in six chapters. Gaps in 21 00:01:46,120 --> 00:01:52,720 Speaker 1: Time on the scale of milliseconds, then hours, then weeks, years, millennia, 22 00:01:53,160 --> 00:01:56,520 Speaker 1: and eons. And if this doesn't get you feeling messed 23 00:01:56,560 --> 00:02:00,360 Speaker 1: up about our view of reality, I don't know what. Well, 24 00:02:00,440 --> 00:02:03,720 Speaker 1: So let's start with milliseconds. You are standing in your 25 00:02:03,800 --> 00:02:07,400 Speaker 1: kitchen and looking over at the salt shaker on the table, 26 00:02:07,440 --> 00:02:10,680 Speaker 1: and you think, where's the pepper shaker? And you glance 27 00:02:10,760 --> 00:02:13,040 Speaker 1: over let's say twelve inches to the left of that, 28 00:02:13,200 --> 00:02:17,400 Speaker 1: and there's the pepper shaker. But something strange has just 29 00:02:17,600 --> 00:02:21,840 Speaker 1: happened and you didn't notice it. Your eyes didn't smoothly 30 00:02:22,000 --> 00:02:26,040 Speaker 1: move across the table. Instead between the salt and the pepper, 31 00:02:26,120 --> 00:02:30,440 Speaker 1: your eyes took a ballistic leap. Ballistic just means that 32 00:02:30,520 --> 00:02:33,880 Speaker 1: the movement is launched and can't be changed along the way. 33 00:02:34,400 --> 00:02:37,680 Speaker 1: So there's a sharp movement of your eyes. And these 34 00:02:37,800 --> 00:02:41,320 Speaker 1: jumps are called cecads, and you make three to four 35 00:02:41,360 --> 00:02:45,160 Speaker 1: of these every second while you're looking around the world. Now, 36 00:02:45,560 --> 00:02:49,680 Speaker 1: if you're around anyone else right now, take a careful 37 00:02:49,720 --> 00:02:52,880 Speaker 1: look at their eyes and you will see this. Their 38 00:02:52,919 --> 00:02:57,400 Speaker 1: eyes are jiggling around multiple times a second, fixating on 39 00:02:57,400 --> 00:03:00,840 Speaker 1: one spot, and then a few hundred milliseconds later, jumping 40 00:03:00,880 --> 00:03:03,799 Speaker 1: to the next spot and fixating there. But here's this 41 00:03:04,000 --> 00:03:09,679 Speaker 1: super weird part. Your experience from the inside behind your 42 00:03:09,800 --> 00:03:15,959 Speaker 1: eyes is totally unaware of these secads. You don't notice them. 43 00:03:16,000 --> 00:03:20,120 Speaker 1: You don't feel like the world is jumping around. But 44 00:03:20,200 --> 00:03:23,840 Speaker 1: why not? What does your visual system do while your 45 00:03:23,880 --> 00:03:27,840 Speaker 1: eyes are in motion between the fixations. Why doesn't your 46 00:03:27,840 --> 00:03:30,919 Speaker 1: brain say, oh my god, the world just screamed past. 47 00:03:31,320 --> 00:03:34,280 Speaker 1: Oh no, there it goes again, and so on. Well 48 00:03:34,320 --> 00:03:36,680 Speaker 1: to answer that, I'm going to give you something that 49 00:03:36,800 --> 00:03:38,560 Speaker 1: you can try, and I really want you to do this. 50 00:03:38,680 --> 00:03:41,280 Speaker 1: Take out your cell phone and hit the button to 51 00:03:41,320 --> 00:03:45,160 Speaker 1: record a video. Now, point your camera at something and 52 00:03:45,200 --> 00:03:49,080 Speaker 1: then jerk it over to a nearby position, then jerk 53 00:03:49,120 --> 00:03:52,040 Speaker 1: it to a point at something else, then jerk it again, 54 00:03:52,120 --> 00:03:55,560 Speaker 1: and so on. Now watch the video, and what you'll 55 00:03:55,560 --> 00:03:59,440 Speaker 1: see is that this video is totally nauseating. So here's 56 00:03:59,440 --> 00:04:04,040 Speaker 1: the question. Why isn't it nauseating when your eyes are 57 00:04:04,120 --> 00:04:07,680 Speaker 1: doing exactly what you just did with your cell phone camera. 58 00:04:08,480 --> 00:04:13,480 Speaker 1: The answer is that your vision is not like a camera. 59 00:04:14,200 --> 00:04:20,000 Speaker 1: What you see is your internal model of the world 60 00:04:20,040 --> 00:04:23,599 Speaker 1: out there. Every time you move your eyes, you're just 61 00:04:23,760 --> 00:04:28,360 Speaker 1: gathering more data to add to your internal model of 62 00:04:28,440 --> 00:04:31,840 Speaker 1: the world. So your eyes are jumping around the scene 63 00:04:31,920 --> 00:04:35,280 Speaker 1: like special ops on a secret mission, and they're adding 64 00:04:35,320 --> 00:04:39,200 Speaker 1: little bits of data to your model with each movement. 65 00:04:40,120 --> 00:04:43,160 Speaker 1: And during the periods when your eyes are in motion, 66 00:04:43,279 --> 00:04:49,120 Speaker 1: your visual system essentially shuts down. It says, okay, eyes, 67 00:04:49,320 --> 00:04:51,520 Speaker 1: I want you to take a jump to the next site, 68 00:04:52,000 --> 00:04:54,599 Speaker 1: and while you're in motion, I'm just going to shut 69 00:04:54,640 --> 00:04:58,200 Speaker 1: down information processing until you get there. And that's why 70 00:04:58,240 --> 00:05:01,640 Speaker 1: you don't see the world screaming past. Okay. So that's 71 00:05:01,680 --> 00:05:05,600 Speaker 1: totally amazing, But that's just the beginning of the weirdness 72 00:05:05,640 --> 00:05:08,800 Speaker 1: for today, because the question I want to ask is this. 73 00:05:09,680 --> 00:05:13,200 Speaker 1: It takes time for your eyes to move to make 74 00:05:13,240 --> 00:05:17,400 Speaker 1: that jump. For a small secada, it takes about thirty milliseconds, 75 00:05:17,400 --> 00:05:20,799 Speaker 1: and for large ones they can take over one hundred 76 00:05:20,800 --> 00:05:23,919 Speaker 1: milliseconds a tenth of a second. And as I said, 77 00:05:24,120 --> 00:05:28,760 Speaker 1: you're doing multiple of these jumps every second. So here's 78 00:05:28,960 --> 00:05:34,200 Speaker 1: the mystery. What happens to the gaps in time while 79 00:05:34,240 --> 00:05:37,560 Speaker 1: your eyes are moving. Why don't you notice the small 80 00:05:37,960 --> 00:05:42,120 Speaker 1: absences of visual input? Okay, So the first thing you 81 00:05:42,200 --> 00:05:45,080 Speaker 1: might say is, well, I don't know how long thirty 82 00:05:45,120 --> 00:05:48,440 Speaker 1: milliseconds is maybe that's too short to notice, but it's not. 83 00:05:49,000 --> 00:05:51,800 Speaker 1: If I came into your room right now and flicked 84 00:05:51,800 --> 00:05:55,039 Speaker 1: the lights off and then back on, even for thirty milliseconds, 85 00:05:55,360 --> 00:05:58,080 Speaker 1: you would detect that, and one hundred milliseconds would be 86 00:05:58,160 --> 00:06:02,400 Speaker 1: super obvious. So why don't you notice the little gaps 87 00:06:02,760 --> 00:06:07,680 Speaker 1: while your visual system is on holiday. Well, your brain 88 00:06:07,800 --> 00:06:11,640 Speaker 1: is doing movie editing and it just gets rid of 89 00:06:11,680 --> 00:06:15,520 Speaker 1: those little gaps in time. Now, this might all sound 90 00:06:15,600 --> 00:06:18,160 Speaker 1: a little unbelievable, so I want to give you a 91 00:06:18,279 --> 00:06:24,080 Speaker 1: very easy way to demonstrate this to yourself. First, stare 92 00:06:24,320 --> 00:06:27,800 Speaker 1: up close at your friend's face and ask kim or 93 00:06:27,880 --> 00:06:31,320 Speaker 1: her to look at your left eye, then your right eye, 94 00:06:31,560 --> 00:06:34,720 Speaker 1: then your left eye, then your right eye. And what 95 00:06:34,720 --> 00:06:37,320 Speaker 1: you'll find is that it's very easy to see your 96 00:06:37,520 --> 00:06:41,640 Speaker 1: friend's eyes move. Their eyes make big jumps from one 97 00:06:41,680 --> 00:06:44,760 Speaker 1: position to the other, and you can watch that transition. 98 00:06:45,240 --> 00:06:48,039 Speaker 1: But now what I want you to do is get 99 00:06:48,120 --> 00:06:53,279 Speaker 1: up close to a mirror and stare at your own face. Now, 100 00:06:53,760 --> 00:06:57,240 Speaker 1: look at your own left eye, then your right eye, 101 00:06:57,360 --> 00:07:01,200 Speaker 1: then your left eye, and what you'll see is bizarre. 102 00:07:01,760 --> 00:07:07,560 Speaker 1: You can never see your own eyes move. Your experience 103 00:07:07,800 --> 00:07:10,560 Speaker 1: is that you are fixated on your left eye, and 104 00:07:10,600 --> 00:07:13,440 Speaker 1: then you are suddenly fixated on your right eye, and 105 00:07:13,480 --> 00:07:16,200 Speaker 1: then you are suddenly fixated on your left eye again, 106 00:07:16,440 --> 00:07:20,360 Speaker 1: But you don't see any movement. And the deep, deep 107 00:07:20,400 --> 00:07:22,840 Speaker 1: thing that I want to address today is that there's 108 00:07:23,000 --> 00:07:27,760 Speaker 1: no gap in time. It seems like you're on one 109 00:07:27,920 --> 00:07:33,000 Speaker 1: eye and then you're immediately on the other. You can't 110 00:07:33,040 --> 00:07:37,000 Speaker 1: see the gap in time at all. No, how could 111 00:07:37,040 --> 00:07:39,480 Speaker 1: this possibly be. It's for the same reason that you 112 00:07:39,480 --> 00:07:42,240 Speaker 1: don't see the world screen past you when you move 113 00:07:42,280 --> 00:07:45,960 Speaker 1: your eyes. All you see is your internal model. And 114 00:07:46,160 --> 00:07:49,920 Speaker 1: just like your internal model constructs space for you, it 115 00:07:50,000 --> 00:07:53,520 Speaker 1: constructs time for you also, and if it doesn't want 116 00:07:53,600 --> 00:07:56,360 Speaker 1: to include something in there, like the gap in time, 117 00:07:56,680 --> 00:08:00,000 Speaker 1: then you simply don't experience it. Now, as our store 118 00:08:00,000 --> 00:08:02,760 Speaker 1: already proceeds today, we're going to get a deeper understanding 119 00:08:02,840 --> 00:08:04,880 Speaker 1: of why this is. But for now, let me just 120 00:08:04,920 --> 00:08:08,880 Speaker 1: say that I've been publishing papers on time perception for 121 00:08:09,040 --> 00:08:11,920 Speaker 1: my whole career in journals like Science and Nature and 122 00:08:11,960 --> 00:08:15,920 Speaker 1: so on, because this is such a weird and under 123 00:08:16,000 --> 00:08:18,720 Speaker 1: explored field. The main thing I want to establish for 124 00:08:18,800 --> 00:08:22,640 Speaker 1: now is that our sense of time, how much time 125 00:08:22,760 --> 00:08:26,600 Speaker 1: passed and what happened when is constructed by our brain. 126 00:08:26,800 --> 00:08:31,040 Speaker 1: It's not an accurate barometer of what's happening out there. 127 00:08:31,360 --> 00:08:33,840 Speaker 1: And for today's episode, the issue we're zooming in on 128 00:08:34,000 --> 00:08:39,160 Speaker 1: is what happens when time disappears. Okay, so during eye 129 00:08:39,160 --> 00:08:42,400 Speaker 1: movements we lose little gaps, and now we're ready to 130 00:08:42,440 --> 00:08:46,360 Speaker 1: move to the next chapter of this story of disappearing time. 131 00:08:46,960 --> 00:08:49,160 Speaker 1: If we can lose fractions of a second and never 132 00:08:49,240 --> 00:08:53,760 Speaker 1: know it, what happens when we lose hours. There are 133 00:08:53,760 --> 00:08:56,880 Speaker 1: many hours in your life when you are alive, but 134 00:08:56,960 --> 00:09:01,480 Speaker 1: you have no sense of the passage of time. In total, 135 00:09:01,679 --> 00:09:05,160 Speaker 1: like thirty years worth of hours in a long life 136 00:09:05,520 --> 00:09:09,760 Speaker 1: are gone. And this is because of sleep. You spend 137 00:09:09,840 --> 00:09:12,360 Speaker 1: a third of your life asleep. And what's fascinating for 138 00:09:12,520 --> 00:09:15,000 Speaker 1: today is not simply that you sleep. It's that you 139 00:09:15,120 --> 00:09:20,800 Speaker 1: don't notice time passing. While you do, you close your eyes, 140 00:09:21,320 --> 00:09:24,360 Speaker 1: your thoughts begin to drift, and then what feels like 141 00:09:24,520 --> 00:09:28,360 Speaker 1: an instant later, your alarm is going off. Seven or 142 00:09:28,400 --> 00:09:36,320 Speaker 1: eight hours are gone. Where exactly did that time go? Well, 143 00:09:36,320 --> 00:09:39,120 Speaker 1: here's the trick. The passage of time from the brain's 144 00:09:39,160 --> 00:09:44,120 Speaker 1: point of view is stitched together from memory. If you 145 00:09:44,480 --> 00:09:46,920 Speaker 1: happen to have heard the very first episode of this 146 00:09:47,000 --> 00:09:50,240 Speaker 1: podcast from some years ago. I explained how my students 147 00:09:50,280 --> 00:09:53,640 Speaker 1: and I dropped volunteers from a one hundred and fifty 148 00:09:53,640 --> 00:09:57,280 Speaker 1: foot tall tower in free fall and measured their time 149 00:09:57,360 --> 00:10:00,680 Speaker 1: perception on the way down. And what we covered is 150 00:10:00,720 --> 00:10:04,280 Speaker 1: that time doesn't actually move in slow motion when you're 151 00:10:04,320 --> 00:10:08,560 Speaker 1: in a scary situation. Instead, it's that you lay down 152 00:10:08,760 --> 00:10:12,600 Speaker 1: more memory when you're scared, and so when your brain 153 00:10:12,640 --> 00:10:15,520 Speaker 1: says what just happened, what just happened, it has all 154 00:10:15,559 --> 00:10:20,239 Speaker 1: this detailed footage to draw on, and so it assumes 155 00:10:20,360 --> 00:10:24,360 Speaker 1: that more time has just passed. In other words, we 156 00:10:24,600 --> 00:10:29,360 Speaker 1: estimate duration retrospectively, and we do it by looking at 157 00:10:29,360 --> 00:10:32,440 Speaker 1: how much footage we can pull up. Now, what we're 158 00:10:32,440 --> 00:10:34,800 Speaker 1: talking about here is the flip side. If there's no 159 00:10:34,960 --> 00:10:39,000 Speaker 1: footage at all, then your brain concludes that no time passed. 160 00:10:39,000 --> 00:10:42,880 Speaker 1: And that's what happens to you in sleep. So when 161 00:10:42,920 --> 00:10:46,240 Speaker 1: you're awake, your brain uses all the data streaming in, 162 00:10:46,360 --> 00:10:48,640 Speaker 1: like what happened and who said what and where you were. 163 00:10:48,880 --> 00:10:53,679 Speaker 1: All these things get used as time landmarks. They're mile 164 00:10:53,800 --> 00:10:58,120 Speaker 1: markers in the road of experience. But during sleep, especially 165 00:10:58,240 --> 00:11:02,040 Speaker 1: during slow wave sleep, there's almost no information coming in. 166 00:11:02,559 --> 00:11:07,479 Speaker 1: The brain becomes decoupled from the external world. Now, interestingly, 167 00:11:07,600 --> 00:11:12,040 Speaker 1: during rem sleep, the brain reactivates in some ways that 168 00:11:12,200 --> 00:11:17,680 Speaker 1: look like waking life. There's intense cortical activity, there's vivid dreaming, 169 00:11:18,080 --> 00:11:21,520 Speaker 1: and you often have the sense of a passage of 170 00:11:21,640 --> 00:11:25,120 Speaker 1: time in a dream, sometimes the sense that a long 171 00:11:25,160 --> 00:11:29,080 Speaker 1: time is passed. But in non rem sleep stages, which 172 00:11:29,120 --> 00:11:32,520 Speaker 1: is the majority of the night, there's little dreaming. And 173 00:11:32,679 --> 00:11:36,080 Speaker 1: in the deepest stages of sleep, your neural firing patterns 174 00:11:36,120 --> 00:11:42,280 Speaker 1: become highly synchronized. Neurons fire and rhythmic bursts followed by silence. 175 00:11:42,320 --> 00:11:47,400 Speaker 1: You're not experiencing anything and you're not encoding memories, so 176 00:11:47,440 --> 00:11:52,559 Speaker 1: the result is no memory, no narrative, and no timestamps. 177 00:11:52,760 --> 00:11:56,640 Speaker 1: Nothing is written down in the internal log book. So 178 00:11:56,679 --> 00:12:01,360 Speaker 1: your subjective experience skips from point A falling asleep to 179 00:12:01,880 --> 00:12:06,960 Speaker 1: point B waking up, and you have no passage in between. Now, 180 00:12:07,000 --> 00:12:12,719 Speaker 1: equally weird but chemically induced is anesthesia. You'll sometimes hear 181 00:12:12,760 --> 00:12:16,839 Speaker 1: people describe general anesthesia as a deep sleep, but that's 182 00:12:16,880 --> 00:12:21,839 Speaker 1: a little bit misleading because anesthesia doesn't quite simulate sleep. Instead, 183 00:12:22,200 --> 00:12:26,800 Speaker 1: when you're under an anesthetic agent like propofol, or isofluorane, 184 00:12:26,880 --> 00:12:30,520 Speaker 1: or ketamine. Your brain is doing something different than just 185 00:12:30,600 --> 00:12:35,240 Speaker 1: moving into synchronized activity. Instead, it's more of a disconnection. 186 00:12:36,000 --> 00:12:41,560 Speaker 1: What brain imaging studies show is a breakdown of cortical connectivity, 187 00:12:41,800 --> 00:12:45,400 Speaker 1: especially between the thalamus and the cortex, and between key 188 00:12:45,480 --> 00:12:50,199 Speaker 1: regions that are needed for conscious awareness, like the posterior 189 00:12:50,200 --> 00:12:53,880 Speaker 1: singular cortex and the prefroneral cortex. So when you're anesthetized, 190 00:12:53,920 --> 00:12:57,600 Speaker 1: there's no dream, no floating sensation, no tunnel of light, 191 00:12:57,679 --> 00:13:02,360 Speaker 1: there is nothing. When you wake up, you don't feel 192 00:13:02,640 --> 00:13:07,160 Speaker 1: like time has passed because you was there to witness 193 00:13:07,240 --> 00:13:11,400 Speaker 1: it and write anything down. The brain can't register time 194 00:13:11,640 --> 00:13:17,680 Speaker 1: in the absence of self modeling processes, the default mode network, 195 00:13:18,000 --> 00:13:22,320 Speaker 1: which normally buzzes along constructing your sense of identity, that 196 00:13:22,600 --> 00:13:28,160 Speaker 1: is offline. So when consciousness returns, you emerge from a 197 00:13:28,800 --> 00:13:33,079 Speaker 1: silent void because you have no memory, you have no 198 00:13:33,440 --> 00:13:36,000 Speaker 1: sense of the passage of time. Now, one thing that's 199 00:13:36,040 --> 00:13:39,600 Speaker 1: always struck me is how untroubled we are by this. 200 00:13:39,760 --> 00:13:43,840 Speaker 1: You go under for surgery, you're counting backward from ten 201 00:13:43,920 --> 00:13:48,600 Speaker 1: to nine eight, and then you're blinking awake in recovery 202 00:13:49,120 --> 00:13:53,920 Speaker 1: three hours of past, no questions asked. The continuity of 203 00:13:53,960 --> 00:13:59,000 Speaker 1: your self just hops the gap. Now that should feel bizarre, 204 00:13:59,040 --> 00:14:02,400 Speaker 1: but it doesn't, because, as I said, continuity isn't measured 205 00:14:02,440 --> 00:14:06,000 Speaker 1: by what happens. It's only measured by what gets remembered. 206 00:14:06,120 --> 00:14:08,880 Speaker 1: And you didn't miss anything that you can recall, so 207 00:14:09,360 --> 00:14:12,320 Speaker 1: no time think about how weird that is. Your life 208 00:14:12,360 --> 00:14:16,480 Speaker 1: can be paused without your awareness. You disappear and the 209 00:14:16,480 --> 00:14:20,040 Speaker 1: world keeps starting, and when you return you feel whole 210 00:14:20,120 --> 00:14:22,560 Speaker 1: and intact, like you never left, but you did and 211 00:14:22,600 --> 00:14:27,160 Speaker 1: there was no you to notice. So if your conscious 212 00:14:27,200 --> 00:14:31,440 Speaker 1: self can go entirely offline for seven hours or for 213 00:14:31,480 --> 00:14:35,320 Speaker 1: the length of a surgery and reappear without damage or 214 00:14:35,360 --> 00:14:39,120 Speaker 1: awareness of the missing time, that means we should really 215 00:14:39,120 --> 00:14:41,520 Speaker 1: be thinking about this self not so much like a 216 00:14:41,960 --> 00:14:48,520 Speaker 1: continuous beam, but more like a flame that gets constantly reignited. 217 00:14:49,120 --> 00:14:52,320 Speaker 1: So what we've seen so far with psychotic eye movements 218 00:14:52,360 --> 00:14:55,160 Speaker 1: and sleep and anesthesia is that the movie of your 219 00:14:55,160 --> 00:14:58,880 Speaker 1: life is full of jump cuts, but your brain, the 220 00:14:58,920 --> 00:15:03,360 Speaker 1: great editor, doesn't show you the gaps. It stitches for 221 00:15:03,440 --> 00:15:08,040 Speaker 1: you a seamless illusion. You were here, now you're here, 222 00:15:08,840 --> 00:15:14,040 Speaker 1: You've always been even when you weren't. Now, maybe right 223 00:15:14,040 --> 00:15:16,680 Speaker 1: in the middle of my last sentence, the whole universe 224 00:15:17,160 --> 00:15:21,640 Speaker 1: froze for five hours. We were all completely frozen, no action, 225 00:15:22,240 --> 00:15:25,480 Speaker 1: no memories. And then just as suddenly as we froze, 226 00:15:25,680 --> 00:15:29,680 Speaker 1: the universe started up again. As far as we are concerned, 227 00:15:30,080 --> 00:15:33,160 Speaker 1: the sentence flowed smoothly. You got the meaning of it 228 00:15:33,200 --> 00:15:36,360 Speaker 1: as you continue to drive or walk or drink the coffee. 229 00:15:36,840 --> 00:15:40,000 Speaker 1: And none of us were the wiser for the universe 230 00:15:40,080 --> 00:15:45,800 Speaker 1: coming to a sudden stop and then restarting. And now 231 00:15:45,840 --> 00:15:49,640 Speaker 1: we're ready for chapter three. We've talked about millisecond gaps 232 00:15:49,720 --> 00:15:52,680 Speaker 1: due to eye movements and hours long gaps due to 233 00:15:52,880 --> 00:15:57,680 Speaker 1: sleep or anesthesia. Now let's stretch time even further to weeks. 234 00:15:58,360 --> 00:16:01,800 Speaker 1: What happens when there's no memory laid down for this 235 00:16:01,880 --> 00:16:05,240 Speaker 1: kind of period of time. One scenario where this happens 236 00:16:05,320 --> 00:16:08,600 Speaker 1: is when a person falls into a coma and they 237 00:16:08,640 --> 00:16:11,280 Speaker 1: wake up after a month of being in a coma, 238 00:16:11,320 --> 00:16:15,040 Speaker 1: and it feels like no time has passed at all. 239 00:16:15,760 --> 00:16:18,200 Speaker 1: There are countless stories like this in any hospital war 240 00:16:18,600 --> 00:16:21,880 Speaker 1: a man gets in a terrible motorcycle accident. He is 241 00:16:22,040 --> 00:16:26,440 Speaker 1: rushed to the ICU. He's intubated. He's stabilized, but he's 242 00:16:26,480 --> 00:16:31,200 Speaker 1: in a coma. His brain activity is minimal. There's no communication, 243 00:16:31,360 --> 00:16:35,920 Speaker 1: no awareness. Weeks pass, and then one day, without warning, 244 00:16:36,200 --> 00:16:39,120 Speaker 1: his eyes open. He turns his head, He looks at 245 00:16:39,120 --> 00:16:43,560 Speaker 1: his mother and says, I'm hungry. To the people around him, 246 00:16:44,080 --> 00:16:46,600 Speaker 1: this is a miracle. They've been counting the days. They've 247 00:16:46,640 --> 00:16:50,240 Speaker 1: been pacing the halls, they've been watching the clock. Time 248 00:16:50,320 --> 00:16:54,760 Speaker 1: has passed agonizingly for them, But for him, it's been nothing. 249 00:16:54,800 --> 00:16:59,160 Speaker 1: He reports no dreams, no thoughts, no sense that time 250 00:16:59,400 --> 00:17:02,880 Speaker 1: even moves. One moment, he was riding his motorcycle. The 251 00:17:02,960 --> 00:17:06,359 Speaker 1: next he was in a hospital bed, maybe a little thinner, 252 00:17:06,800 --> 00:17:10,320 Speaker 1: surrounded by unfamiliar machines and unfamiliar faces. It might have 253 00:17:10,400 --> 00:17:13,840 Speaker 1: been six minutes or six weeks. To him, it's the same. 254 00:17:14,520 --> 00:17:16,720 Speaker 1: So what's happening here? A lot of what we know 255 00:17:16,760 --> 00:17:21,400 Speaker 1: about coma comes from EEG readings and fMRI scans, which 256 00:17:21,440 --> 00:17:25,760 Speaker 1: show severely reduced metabolic activity, especially in the cortex, where 257 00:17:26,080 --> 00:17:30,560 Speaker 1: higher order processing lives. The reticular activating system in the 258 00:17:30,560 --> 00:17:34,719 Speaker 1: brain stem, which keeps you aroused, that goes quiet the thalamus, 259 00:17:34,720 --> 00:17:37,920 Speaker 1: which is sort of like a central switchboard. It fails 260 00:17:38,000 --> 00:17:42,360 Speaker 1: to distribute the sensory information and the default mode network, 261 00:17:42,400 --> 00:17:46,040 Speaker 1: which is that ever chattering backdrop of identity and self 262 00:17:46,080 --> 00:17:50,919 Speaker 1: awareness that goes dark. So, in effect, the machinery of 263 00:17:51,119 --> 00:17:58,000 Speaker 1: consciousness powers down, like a city experiencing a blackout. Your 264 00:17:58,119 --> 00:18:00,919 Speaker 1: lights might flicker a little in one nayemborhood, but the 265 00:18:01,000 --> 00:18:06,480 Speaker 1: downtown grid where memory and narrative and time perception live, 266 00:18:06,680 --> 00:18:11,160 Speaker 1: that downtown grid is silent. When someone wakes from a coma, 267 00:18:11,240 --> 00:18:12,879 Speaker 1: they have to figure out where they are and what 268 00:18:12,960 --> 00:18:16,640 Speaker 1: the heck happened. But what's striking is how little distress 269 00:18:16,720 --> 00:18:21,280 Speaker 1: they show over the lost time itself. They may be confused, 270 00:18:21,280 --> 00:18:25,560 Speaker 1: but they're not grieving the missing days. Why. It's because 271 00:18:25,640 --> 00:18:27,720 Speaker 1: you can only feel the passage of time when you 272 00:18:27,800 --> 00:18:32,480 Speaker 1: have been there to experience it. Duration of time is 273 00:18:32,520 --> 00:18:37,840 Speaker 1: something that you build neurally, without sensory input, without new memories. 274 00:18:38,280 --> 00:18:41,560 Speaker 1: There's no architecture of time. The period where one is 275 00:18:41,600 --> 00:18:43,880 Speaker 1: in a coma is not perceived as a gap. It's 276 00:18:44,119 --> 00:19:02,600 Speaker 1: just omitted. So what does this tell us? Consciousness is 277 00:19:02,760 --> 00:19:07,040 Speaker 1: an evolved interface that gives you the experience of being 278 00:19:07,400 --> 00:19:12,960 Speaker 1: a unified self moving through time. The interface can crash, 279 00:19:13,000 --> 00:19:16,480 Speaker 1: and when it does no internal witness remains to keep 280 00:19:16,480 --> 00:19:20,520 Speaker 1: the clock running. So this phrases deep questions about selfhood. 281 00:19:20,520 --> 00:19:23,040 Speaker 1: What does it mean to be you? If you can 282 00:19:23,119 --> 00:19:26,960 Speaker 1: vanish for months and reappear unchanged. If months of your 283 00:19:27,000 --> 00:19:30,560 Speaker 1: life can go unregistered, not as memory and therefore not 284 00:19:30,760 --> 00:19:33,679 Speaker 1: as a duration, then was it part of your life 285 00:19:33,760 --> 00:19:37,119 Speaker 1: at all? Your life is only what you write down 286 00:19:37,200 --> 00:19:40,320 Speaker 1: in your neural circuits. And when your consciousness vanishes, so 287 00:19:40,600 --> 00:19:44,600 Speaker 1: does the passage of time. So we just explored the 288 00:19:44,640 --> 00:19:49,239 Speaker 1: gaps caused by unconsciousness, sleep and anesthesia and coma. But 289 00:19:49,400 --> 00:19:53,400 Speaker 1: now we reach something stranger. When you're fully awake, your 290 00:19:53,400 --> 00:19:58,040 Speaker 1: eyes are open, your senses are functioning, and time still vanishes. 291 00:19:58,480 --> 00:20:03,760 Speaker 1: This is in particular let's talk about what's called antaro 292 00:20:03,880 --> 00:20:07,879 Speaker 1: grade amnesia, which is the inability to make new memories 293 00:20:08,359 --> 00:20:11,920 Speaker 1: after you get some brain damage. So your short term 294 00:20:12,000 --> 00:20:15,080 Speaker 1: working memory can remain fine, so you can carry on 295 00:20:15,119 --> 00:20:17,800 Speaker 1: a conversation, you can make a cup of coffee, but 296 00:20:17,840 --> 00:20:21,679 Speaker 1: you won't retain any of what just happened fifteen minutes later. 297 00:20:21,840 --> 00:20:25,359 Speaker 1: In other words, you've got short term memory, but you 298 00:20:25,440 --> 00:20:30,840 Speaker 1: are not converting it into long term memory. Experience evaporates 299 00:20:30,960 --> 00:20:33,800 Speaker 1: outside a fifteen minute window. The key player here is 300 00:20:33,840 --> 00:20:36,560 Speaker 1: a region of the brain called the medial temporal lobe, 301 00:20:36,640 --> 00:20:40,600 Speaker 1: and inside that the hippocampus and the surrounding cortex. These 302 00:20:40,680 --> 00:20:44,240 Speaker 1: regions act as a kind of staging ground where new 303 00:20:44,359 --> 00:20:49,840 Speaker 1: experiences are encoded and then gradually consolidated into long term 304 00:20:49,880 --> 00:20:52,920 Speaker 1: memory from interactions with the rest of the cortex. When 305 00:20:52,960 --> 00:20:56,600 Speaker 1: the hippocampus is damaged, which can happen for a lot 306 00:20:56,640 --> 00:21:00,000 Speaker 1: of reasons like stroke or trauma, or hypoxia or encephalitis. 307 00:21:00,600 --> 00:21:06,640 Speaker 1: When the hippocampus is damaged, the encoding of memories gets disrupted. 308 00:21:06,880 --> 00:21:09,600 Speaker 1: You still got sensory input getting to the brain, Your 309 00:21:09,680 --> 00:21:12,920 Speaker 1: emotions are still functioning. You still have your motor skills 310 00:21:12,960 --> 00:21:17,199 Speaker 1: like walking and eating. But the narrative thread of life 311 00:21:18,040 --> 00:21:21,480 Speaker 1: I was here and then I was there, that part 312 00:21:21,560 --> 00:21:26,040 Speaker 1: is severed. So consider this case of Henry Meliason. It's 313 00:21:26,080 --> 00:21:29,000 Speaker 1: a pretty well known case. He had epilepsy, and so 314 00:21:29,119 --> 00:21:32,480 Speaker 1: the surgeons removed a lot of his medial temporal lobe, 315 00:21:32,480 --> 00:21:35,760 Speaker 1: including the hippocampus on both sides of his brain, and 316 00:21:35,800 --> 00:21:37,600 Speaker 1: when he woke up from the surgery, it was found 317 00:21:37,640 --> 00:21:41,400 Speaker 1: that had indeed cured the epilepsy and everything seemed perfectly 318 00:21:41,480 --> 00:21:46,640 Speaker 1: fine until his clinical team realized that something wasn't quite right, 319 00:21:47,119 --> 00:21:50,119 Speaker 1: and it became clear that his short term memory was 320 00:21:50,200 --> 00:21:52,919 Speaker 1: fine and his long term memory was fine, but he 321 00:21:52,960 --> 00:21:56,880 Speaker 1: could no longer make the new long term memories. In 322 00:21:56,920 --> 00:22:01,560 Speaker 1: other words, he could carry on conversationations for ten minutes, 323 00:22:01,600 --> 00:22:06,000 Speaker 1: but afterward it was as if nothing had ever occurred, 324 00:22:06,760 --> 00:22:11,760 Speaker 1: no learning, no narrative, no accumulation of time. His consciousness 325 00:22:12,080 --> 00:22:15,919 Speaker 1: would reset with each passing moment. So even though the 326 00:22:16,000 --> 00:22:19,159 Speaker 1: surgery took place in nineteen fifty three when he was 327 00:22:19,200 --> 00:22:23,400 Speaker 1: twenty seven years old, he lived for fifty five more 328 00:22:23,600 --> 00:22:27,239 Speaker 1: years after his surgery, and during that time he was 329 00:22:27,440 --> 00:22:31,119 Speaker 1: stuck in what one of his researchers, Suzanne Corkin, called 330 00:22:31,560 --> 00:22:36,800 Speaker 1: a permanent present tense. For example, he could remember living 331 00:22:36,800 --> 00:22:39,720 Speaker 1: with his parents and playing with his cousin's neighbors. His 332 00:22:39,760 --> 00:22:44,000 Speaker 1: relationship with his mother remained a touchstone even after her death. 333 00:22:44,240 --> 00:22:48,359 Speaker 1: He thought she was still alive because his stable memories 334 00:22:48,440 --> 00:22:50,960 Speaker 1: were from when he lived at home with her in 335 00:22:51,000 --> 00:22:55,120 Speaker 1: the nineteen forties nineteen fifties. Henry was a teenager during 336 00:22:55,119 --> 00:22:58,040 Speaker 1: World War Two, and he retained knowledge from that period 337 00:22:58,520 --> 00:23:02,280 Speaker 1: to him even from the late nineteen forties felt just 338 00:23:02,320 --> 00:23:05,280 Speaker 1: as near to him in time as they did when 339 00:23:05,280 --> 00:23:09,480 Speaker 1: he first underwent the surgery. When asked about his employment, 340 00:23:09,560 --> 00:23:12,720 Speaker 1: he sometimes mentioned working at a typewriter factory in the 341 00:23:12,800 --> 00:23:16,160 Speaker 1: nineteen forties, as though that were his current or most 342 00:23:16,200 --> 00:23:20,600 Speaker 1: recent job. His cultural knowledge was frozen in the early 343 00:23:20,680 --> 00:23:23,639 Speaker 1: nineteen fifties, so people said that meeting him was like 344 00:23:24,040 --> 00:23:29,280 Speaker 1: speaking to someone displaced from the Eisenhower era, with none 345 00:23:29,359 --> 00:23:34,200 Speaker 1: of the intervening decades having registered. So his body aged, 346 00:23:34,240 --> 00:23:39,560 Speaker 1: but his personal timeline didn't. Events didn't accumulate into a 347 00:23:39,600 --> 00:23:44,760 Speaker 1: personal timeline, so decades really did vanish for him. It 348 00:23:44,840 --> 00:23:49,160 Speaker 1: was as though those years had simply never been lived. 349 00:23:49,840 --> 00:23:53,920 Speaker 1: Neurosurgeons stopped doing those medial temporal lobe surgeries as soon 350 00:23:53,960 --> 00:23:57,399 Speaker 1: as they saw what had happened with Henry, But you 351 00:23:57,480 --> 00:24:01,160 Speaker 1: can still see this condition of antaro g amnesia all 352 00:24:01,200 --> 00:24:05,120 Speaker 1: the time. For example, it happens in Corsicov's syndrome, which 353 00:24:05,200 --> 00:24:09,359 Speaker 1: is caused by chronic alcohol abuse leading to thiamine deficiency. 354 00:24:10,000 --> 00:24:14,280 Speaker 1: The damage affects a circuit that's critical for laying down memories, 355 00:24:14,320 --> 00:24:18,640 Speaker 1: and the result is patients who are alert and socially 356 00:24:18,680 --> 00:24:22,520 Speaker 1: interactive but just like Henry, they live in a kind 357 00:24:22,560 --> 00:24:27,520 Speaker 1: of temporal groundhog day because they are not laying down 358 00:24:28,119 --> 00:24:31,320 Speaker 1: long term memory, and so when they say how much 359 00:24:31,440 --> 00:24:34,960 Speaker 1: time passed since I was last year, there's no memory 360 00:24:35,000 --> 00:24:39,600 Speaker 1: footage to draw on, and so the answer is no time. Now. 361 00:24:39,680 --> 00:24:42,520 Speaker 1: Shift a bit to imagine not just losing the ability 362 00:24:42,560 --> 00:24:48,480 Speaker 1: to build new memories, but also retrograde amnesia, losing memories 363 00:24:48,520 --> 00:24:51,720 Speaker 1: that had already been encoded. And this can happen after, 364 00:24:51,960 --> 00:24:56,080 Speaker 1: for example, a major brain injury. Here the damage tends 365 00:24:56,119 --> 00:24:59,560 Speaker 1: to affect the areas where memory has previously laid down, 366 00:24:59,680 --> 00:25:02,399 Speaker 1: like the the temporal in the frontal lobes. Depending on 367 00:25:02,440 --> 00:25:05,399 Speaker 1: the severity, you can wipe out months or years or 368 00:25:05,440 --> 00:25:09,320 Speaker 1: even decades. Now. One of the oldest rules in neurology 369 00:25:09,440 --> 00:25:13,639 Speaker 1: is called ribos law, and this is that older memories 370 00:25:13,840 --> 00:25:17,600 Speaker 1: are more stable than newer memories. I wrote about this 371 00:25:17,640 --> 00:25:19,679 Speaker 1: at length in my book Live Wire. But the bottom 372 00:25:19,720 --> 00:25:24,080 Speaker 1: line is that older memories get burned more into the 373 00:25:24,119 --> 00:25:27,679 Speaker 1: circuitry of the brain with time. So in these medical 374 00:25:27,720 --> 00:25:31,560 Speaker 1: cases of retrograde amnesia, a person wakes up after head 375 00:25:31,600 --> 00:25:34,760 Speaker 1: injury and they still know how to speak, how to walk, 376 00:25:34,800 --> 00:25:36,760 Speaker 1: how to solve a math problem, but they have no 377 00:25:37,080 --> 00:25:41,440 Speaker 1: memory of their spouse, their job, maybe their own name. 378 00:25:42,080 --> 00:25:44,760 Speaker 1: Procedural memory, which is how to do things like ead 379 00:25:44,880 --> 00:25:50,639 Speaker 1: or walk or talk that remains. But autobiographical continuity, the 380 00:25:50,680 --> 00:25:54,800 Speaker 1: sense of being a single person through time that breaks 381 00:25:55,760 --> 00:25:58,800 Speaker 1: from the outside. Their life has gone on, but from 382 00:25:58,880 --> 00:26:04,360 Speaker 1: the inside, their personal timeline has been redacted. The calendar 383 00:26:04,440 --> 00:26:09,960 Speaker 1: has skipped, and they have no internal record of the passage. 384 00:26:10,840 --> 00:26:13,040 Speaker 1: So that brings us back to the central lesson that 385 00:26:13,119 --> 00:26:19,000 Speaker 1: the experience of duration has everything to do with episodic memory. 386 00:26:19,200 --> 00:26:22,000 Speaker 1: We crank up a network called the default mode network. 387 00:26:22,040 --> 00:26:24,280 Speaker 1: This includes a number of regions, but the key is 388 00:26:24,320 --> 00:26:28,720 Speaker 1: that this network is active during introspection and daydreaming and 389 00:26:28,760 --> 00:26:33,960 Speaker 1: imagining the future. It's how we mentally time travel, reliving 390 00:26:34,000 --> 00:26:40,240 Speaker 1: the past, simulating possible futures, placing ourselves in a temporal context. 391 00:26:40,800 --> 00:26:45,440 Speaker 1: When episodic memory fails, when nothing gets written down, the 392 00:26:45,480 --> 00:26:49,800 Speaker 1: internal model of the passage of time collapses. There may 393 00:26:49,800 --> 00:26:56,199 Speaker 1: be sensory continuity, but there's no narrative continuity. Just like 394 00:26:56,320 --> 00:27:00,560 Speaker 1: coma patients, the people with amnesia often don't feel distress 395 00:27:00,600 --> 00:27:03,840 Speaker 1: about the missing time because they don't experience it. Is missing. 396 00:27:03,920 --> 00:27:07,640 Speaker 1: The brain doesn't alert you to what it failed to store. 397 00:27:08,200 --> 00:27:11,240 Speaker 1: If no memory was written, the time doesn't register as empty. 398 00:27:11,280 --> 00:27:14,520 Speaker 1: It just is non existent. Again, this is just like 399 00:27:14,560 --> 00:27:17,760 Speaker 1: your deep sleep at night. You don't lay down memories 400 00:27:17,800 --> 00:27:21,480 Speaker 1: and the time just poof disappears. In this sense, we're 401 00:27:21,560 --> 00:27:25,960 Speaker 1: all like Henry. Eight hours just passed, but we splice 402 00:27:26,000 --> 00:27:29,879 Speaker 1: the film together, just like Henry between his twenty seventh 403 00:27:29,920 --> 00:27:33,960 Speaker 1: birthday and sixty seventh birthday. Okay, so we've talked about 404 00:27:33,960 --> 00:27:38,080 Speaker 1: missing milliseconds and hours and even years. But there's another 405 00:27:38,160 --> 00:27:41,120 Speaker 1: kind of time distortion, one that doesn't happen in your 406 00:27:41,200 --> 00:27:46,439 Speaker 1: direct experience, but instead inside your imagination. And that happens 407 00:27:46,440 --> 00:27:50,160 Speaker 1: when we try to think about centuries or about millennia, 408 00:27:50,520 --> 00:27:54,920 Speaker 1: about things way older than our own lives or our parents' 409 00:27:54,920 --> 00:27:58,600 Speaker 1: lives or the oldest thing we've ever touched personally, were 410 00:27:58,760 --> 00:28:03,560 Speaker 1: really bad at long time. So ask a group of 411 00:28:03,640 --> 00:28:07,200 Speaker 1: sixth graders what happened one hundred years ago, and they'll 412 00:28:07,200 --> 00:28:11,679 Speaker 1: say the olden days or maybe before the Internet. But 413 00:28:11,720 --> 00:28:14,439 Speaker 1: one hundred years ago was nineteen twenty five, when the 414 00:28:14,480 --> 00:28:17,040 Speaker 1: Model t Ford was rolling off assembly lines and the 415 00:28:17,040 --> 00:28:21,520 Speaker 1: Great War was over, and quantum mechanics was controversial. Asked 416 00:28:21,560 --> 00:28:24,720 Speaker 1: them about five hundred years ago, and you might as 417 00:28:24,720 --> 00:28:29,840 Speaker 1: well be describing mythology. The timeline collapses into a soup 418 00:28:29,960 --> 00:28:34,760 Speaker 1: of olden stuff, where Genghis Khan and Cleopatra and Abraham 419 00:28:34,840 --> 00:28:38,280 Speaker 1: Lincoln all might live at the same time. Now, as 420 00:28:38,320 --> 00:28:42,200 Speaker 1: you grow older, you get better at understanding time, in 421 00:28:42,240 --> 00:28:46,000 Speaker 1: part because you have more practice at it. You get 422 00:28:46,040 --> 00:28:50,040 Speaker 1: to know what longer and longer periods feel like. In 423 00:28:50,080 --> 00:28:54,560 Speaker 1: other words, the ability to judge historical time requires a 424 00:28:54,800 --> 00:28:59,760 Speaker 1: cognitive map of scale, and that map has to be built. 425 00:29:00,160 --> 00:29:05,280 Speaker 1: Children's brains are still developing ways of representing duration and 426 00:29:05,400 --> 00:29:08,920 Speaker 1: sequence and castality over large time scales. What it has 427 00:29:09,000 --> 00:29:14,480 Speaker 1: to do with is the gradual accumulation of memory across years. 428 00:29:14,960 --> 00:29:17,640 Speaker 1: In other words, you get better at representing long time 429 00:29:17,680 --> 00:29:22,000 Speaker 1: scals because you've lived more time. To a six year old, 430 00:29:22,480 --> 00:29:26,040 Speaker 1: one year is a sixth of their entire life, it's massive. 431 00:29:26,160 --> 00:29:29,600 Speaker 1: But to a sixty year old, one year is a blip. 432 00:29:29,800 --> 00:29:33,280 Speaker 1: It's a small ripple in the pool of memory. So 433 00:29:33,440 --> 00:29:39,240 Speaker 1: our internal yardstick for time stretches. As we age, we 434 00:29:39,320 --> 00:29:41,880 Speaker 1: got a better sense of proportion. We begin to feel 435 00:29:41,920 --> 00:29:47,440 Speaker 1: what a century might mean not because we remember it directly, 436 00:29:47,480 --> 00:29:51,760 Speaker 1: but because we've had enough decades to simulate it with 437 00:29:51,960 --> 00:29:57,080 Speaker 1: some emotional weight. But go further back, like ten thousand 438 00:29:57,120 --> 00:29:59,840 Speaker 1: years or one hundred thousand, and your mental simulation is 439 00:30:00,120 --> 00:30:05,080 Speaker 1: not particularly good. You've got evolutionary time, in geological time, 440 00:30:05,120 --> 00:30:11,480 Speaker 1: and cosmological time. These scales are too vast to inhabit intuitively. 441 00:30:12,160 --> 00:30:15,280 Speaker 1: You can say the invention of writing is six thousand 442 00:30:15,360 --> 00:30:19,440 Speaker 1: years old, but does that number feel real? Can you 443 00:30:19,760 --> 00:30:25,920 Speaker 1: feel the difference between six thousand and sixty thousand? For example, 444 00:30:26,280 --> 00:30:31,320 Speaker 1: there's an internet meme that asks did Cleopatra live closer 445 00:30:31,360 --> 00:30:34,880 Speaker 1: in time to the building of the Great Pyramid at 446 00:30:34,920 --> 00:30:39,040 Speaker 1: Giza or to the lunar landing. Now you'll remember that 447 00:30:39,040 --> 00:30:42,640 Speaker 1: Cleopatra was the Greek queen of Egypt from fifty one 448 00:30:42,720 --> 00:30:46,360 Speaker 1: to thirty BC. So what comes as a great surprise 449 00:30:46,440 --> 00:30:49,680 Speaker 1: to a lot of people was that she was actually 450 00:30:49,840 --> 00:30:53,720 Speaker 1: closer in time to the moon landing. Why because she 451 00:30:53,880 --> 00:30:58,120 Speaker 1: was born about two thousand, five hundred years after the 452 00:30:58,160 --> 00:31:01,400 Speaker 1: Great Pyramid at Giza was built, and only about two 453 00:31:01,440 --> 00:31:04,920 Speaker 1: thousand years before the first lunar landing, So she was 454 00:31:05,000 --> 00:31:09,360 Speaker 1: five hundred years closer to moon landings. And iPhones and 455 00:31:09,440 --> 00:31:14,880 Speaker 1: chat GPT than to the Great Pyramid. It's surprising, right, 456 00:31:15,120 --> 00:31:17,760 Speaker 1: And what it demonstrates is that none of us have 457 00:31:17,920 --> 00:31:38,600 Speaker 1: particularly good intuitions about deep time. Now, if you are 458 00:31:38,640 --> 00:31:43,640 Speaker 1: an evolutionary biologist or a geologist or an astrophysicist, you 459 00:31:43,680 --> 00:31:47,600 Speaker 1: can learn how to do temporal sequencing, like that event 460 00:31:47,720 --> 00:31:50,640 Speaker 1: happened a billion years before that other event, But you 461 00:31:50,720 --> 00:31:54,840 Speaker 1: may as well be memorizing the order of exits on 462 00:31:54,920 --> 00:31:58,560 Speaker 1: the highway in the sense that you're not feeling or 463 00:31:58,680 --> 00:32:03,880 Speaker 1: simulating a billion year. You're mostly just memorizing that road sign. 464 00:32:04,200 --> 00:32:06,120 Speaker 1: So what seems clear is that as soon as we 465 00:32:06,200 --> 00:32:11,120 Speaker 1: start talking really long timescales, our brains just weren't built 466 00:32:11,120 --> 00:32:13,840 Speaker 1: for that. Really, think about this, what's the longest period 467 00:32:13,880 --> 00:32:18,000 Speaker 1: of time that you can realistically simulate emotionally? You can 468 00:32:18,080 --> 00:32:21,200 Speaker 1: sort of feel what a day feels like, probably a week, 469 00:32:21,320 --> 00:32:24,360 Speaker 1: a month, and you may even have enough experience in 470 00:32:24,360 --> 00:32:27,000 Speaker 1: the world that you can really feel the weight of 471 00:32:27,040 --> 00:32:30,200 Speaker 1: a year or maybe even a decade. But can you 472 00:32:30,240 --> 00:32:33,400 Speaker 1: really simulate what it would be like to spend a 473 00:32:33,520 --> 00:32:37,160 Speaker 1: century of time hanging out and doom scrolling and cooking 474 00:32:37,200 --> 00:32:39,760 Speaker 1: meals and taking your dog for a walk for a 475 00:32:39,880 --> 00:32:44,280 Speaker 1: thousand years. Just try to imagine ten thousand years since 476 00:32:44,320 --> 00:32:48,840 Speaker 1: the invention of agriculture. Try to feel ten thousand years. 477 00:32:49,280 --> 00:32:53,160 Speaker 1: Your brain might conjure up some images like cave paintings 478 00:32:53,160 --> 00:32:57,560 Speaker 1: and mammoths and spears, but can you actually understand the 479 00:32:57,600 --> 00:33:01,920 Speaker 1: sheer stretch of a time period like that. Presumably not, 480 00:33:02,080 --> 00:33:06,240 Speaker 1: We're just not wired for it. Our temporal reasoning evolved 481 00:33:06,360 --> 00:33:10,320 Speaker 1: in the service of short term prediction, hunting and gathering, 482 00:33:10,680 --> 00:33:15,560 Speaker 1: planning social exchanges, maybe tracking seasons, but that's it. The 483 00:33:15,600 --> 00:33:19,440 Speaker 1: oldest parts of the brain work in rhythms of hours 484 00:33:19,440 --> 00:33:23,320 Speaker 1: and days, or sometimes weeks. This is why we struggle 485 00:33:23,840 --> 00:33:29,240 Speaker 1: to grasp timelines like civilizational collapse, or for younger people, 486 00:33:29,320 --> 00:33:35,520 Speaker 1: even something like retirement planning. Our cognitive system compresses distant 487 00:33:35,640 --> 00:33:39,440 Speaker 1: time the way it compresses vision, blurring the edges to 488 00:33:39,480 --> 00:33:42,560 Speaker 1: focus on what's close. Just like we have a phobia 489 00:33:42,760 --> 00:33:46,160 Speaker 1: in the eye, a center of sharp focus, we have 490 00:33:46,240 --> 00:33:49,240 Speaker 1: what you can think of as a temporal phobia, which 491 00:33:49,520 --> 00:33:54,720 Speaker 1: sharpens the present and blurs the deep past and distant future. 492 00:33:55,080 --> 00:33:58,320 Speaker 1: The truth is it's sort of a biological miracle that 493 00:33:58,360 --> 00:34:01,200 Speaker 1: we can contemplate large time scales at all. We can 494 00:34:01,480 --> 00:34:05,120 Speaker 1: look at a fossil and say this was alive three 495 00:34:05,240 --> 00:34:09,280 Speaker 1: hundred million years ago, and feel even the faintest flicker 496 00:34:09,400 --> 00:34:12,920 Speaker 1: of what that means. It's surprising that our brains can 497 00:34:12,960 --> 00:34:18,040 Speaker 1: even attempt to model epics that no organism ever lived 498 00:34:18,200 --> 00:34:22,960 Speaker 1: to see. We've talked about missing time, milliseconds loss to 499 00:34:23,000 --> 00:34:27,640 Speaker 1: eye movements, hours lost to sleep, years vanished to amnesia, 500 00:34:27,840 --> 00:34:32,000 Speaker 1: centuries gone because we can't understand deep time. We've seen 501 00:34:32,040 --> 00:34:35,320 Speaker 1: how the brain edits the story and patches the gaps. 502 00:34:35,880 --> 00:34:41,320 Speaker 1: But what if entire chapters of Earth's history are missing, 503 00:34:41,400 --> 00:34:44,799 Speaker 1: not from your memory, but from the planet's memory. Here's 504 00:34:44,840 --> 00:34:47,360 Speaker 1: what I mean. It seems clear enough that we humans 505 00:34:47,400 --> 00:34:51,520 Speaker 1: are the first intelligent civilization. We're the only creatures to 506 00:34:51,600 --> 00:34:56,839 Speaker 1: build cities, to form empires, to write literature about ourselves. 507 00:34:57,480 --> 00:35:00,880 Speaker 1: But we've only been here for the last last blink 508 00:35:00,960 --> 00:35:05,160 Speaker 1: of evolutionary time. We invented agriculture only ten thousand years ago, 509 00:35:05,239 --> 00:35:09,160 Speaker 1: in something like a big urban center with laws and organization. 510 00:35:09,520 --> 00:35:13,840 Speaker 1: It's all unbelievably new. But the Earth is four point 511 00:35:13,920 --> 00:35:18,000 Speaker 1: five billion years old, and complex life has been around 512 00:35:18,280 --> 00:35:23,520 Speaker 1: for hundreds of millions of years. So here's a speculation 513 00:35:23,640 --> 00:35:26,680 Speaker 1: that Some thinkers have chewed on what if we are 514 00:35:26,719 --> 00:35:32,440 Speaker 1: not the first? What if something like a civilization had arisen, 515 00:35:32,880 --> 00:35:37,680 Speaker 1: say six hundred million years ago, way before Homo sapiens, 516 00:35:37,960 --> 00:35:42,719 Speaker 1: like a full civilization with philosophies and literature and politics 517 00:35:42,760 --> 00:35:47,640 Speaker 1: and music and wars, And maybe the civilization lasted for 518 00:35:47,840 --> 00:35:52,319 Speaker 1: twenty million years, and we would have no idea it 519 00:35:52,320 --> 00:35:55,400 Speaker 1: had ever been here. Now, how could that possibly be? 520 00:35:55,480 --> 00:36:00,800 Speaker 1: Wouldn't we find fossil evidence of them? Well, under certain circumstances, 521 00:36:00,800 --> 00:36:04,399 Speaker 1: we might, But let's say they were soft bodied organisms, 522 00:36:04,680 --> 00:36:09,840 Speaker 1: we would almost certainly never know. Soft tissues decay quickly. 523 00:36:10,239 --> 00:36:13,320 Speaker 1: Fossilization is very rare, and if things aren't buried in 524 00:36:13,360 --> 00:36:17,080 Speaker 1: the right sediment, they can vanish without a trace. So 525 00:36:17,200 --> 00:36:21,320 Speaker 1: our fossil record as it stands is a shattered mosaic. 526 00:36:21,360 --> 00:36:26,080 Speaker 1: It's a few lucky remnants scattered across eons of erosion. 527 00:36:26,239 --> 00:36:29,560 Speaker 1: So think about the Ediacaran period, about six hundred million 528 00:36:29,600 --> 00:36:34,440 Speaker 1: years ago. That's before trilobytes, before shells, before vertebrates. We 529 00:36:34,560 --> 00:36:39,800 Speaker 1: have impressions in sandstone of strange, soft bodied life forms, 530 00:36:40,239 --> 00:36:45,239 Speaker 1: organisms with no clear ancestors or descendants. Their biology is strange, 531 00:36:45,280 --> 00:36:50,400 Speaker 1: Their symmetry is unfamiliar. Could some of them have evolved intelligence? 532 00:36:50,840 --> 00:36:53,880 Speaker 1: Could they have had cognition, maybe not quite like ours, 533 00:36:53,880 --> 00:36:57,720 Speaker 1: but in some way parallel. Could they have built societies 534 00:36:57,840 --> 00:37:02,040 Speaker 1: and languages and structure that we can't even imagine. If 535 00:37:02,080 --> 00:37:05,560 Speaker 1: they did, and if they were made of soft flesh, 536 00:37:05,640 --> 00:37:10,520 Speaker 1: glatinous matter, fragile compounds, and they built their civilizations with 537 00:37:10,920 --> 00:37:15,839 Speaker 1: adobe homes, the odds are that none of the appropriate 538 00:37:15,880 --> 00:37:19,680 Speaker 1: evidence would exist anymore for us to find. No bones, 539 00:37:19,719 --> 00:37:23,719 Speaker 1: no ruins, just a story that played out hundreds of 540 00:37:23,920 --> 00:37:28,680 Speaker 1: millions of years before us and was completely erased. So 541 00:37:29,560 --> 00:37:32,719 Speaker 1: we assume we're the first ones to tell a story. 542 00:37:32,760 --> 00:37:35,759 Speaker 1: But maybe we're just the ones holding the pen at 543 00:37:35,760 --> 00:37:40,520 Speaker 1: the moment, totally unaware of how many other pens were 544 00:37:40,600 --> 00:37:45,680 Speaker 1: lifted and scratched across time and then lost. Here's the 545 00:37:45,719 --> 00:37:47,959 Speaker 1: link to what I've been talking about. The Earth has 546 00:37:48,080 --> 00:37:52,840 Speaker 1: no central memory or backup drive. If there are no 547 00:37:53,040 --> 00:37:56,960 Speaker 1: records that survive, no fossils, no scars on the crust 548 00:37:57,000 --> 00:38:00,359 Speaker 1: that lasted this long, then that time is gone and 549 00:38:00,400 --> 00:38:05,439 Speaker 1: it's therefore forgotten and unrecoverable. Just like you falling into 550 00:38:05,480 --> 00:38:10,240 Speaker 1: a deep sleep or having amnesia. It's another gap in time. 551 00:38:11,200 --> 00:38:13,600 Speaker 1: We like to believe that history is cumulative, that it 552 00:38:13,640 --> 00:38:16,719 Speaker 1: adds up in layers like strata in a canyon wall. 553 00:38:16,840 --> 00:38:19,319 Speaker 1: But as we saw in the neuroscience of the first 554 00:38:19,400 --> 00:38:24,759 Speaker 1: four chapters of today's podcast, history can be fragile and erasable. 555 00:38:25,000 --> 00:38:30,400 Speaker 1: Any story from milliseconds to eons can pass, and if 556 00:38:30,480 --> 00:38:36,640 Speaker 1: there's no record, then there's no memory. What we've seen 557 00:38:36,680 --> 00:38:40,800 Speaker 1: today is that time is a narrative medium, and narratives 558 00:38:40,840 --> 00:38:44,200 Speaker 1: can fail, They can go unrecorded, they can be lost. 559 00:38:44,640 --> 00:38:49,400 Speaker 1: We began with milliseconds lost to eye movements called secods, 560 00:38:49,600 --> 00:38:53,640 Speaker 1: where the brain quietly deletes motion, blur and pastes your 561 00:38:53,680 --> 00:38:57,280 Speaker 1: world back together as if nothing ever vanished. We moved 562 00:38:57,400 --> 00:39:02,240 Speaker 1: to hours lost to sleep, where consciousness dissolves and time 563 00:39:02,400 --> 00:39:06,680 Speaker 1: drops out unnoticed. We looked into anesthesia, where the self 564 00:39:06,680 --> 00:39:10,880 Speaker 1: disappears completely, no memory, no mind, no time, and then 565 00:39:11,160 --> 00:39:15,279 Speaker 1: returns like a light flicked back on. We stretched to 566 00:39:15,760 --> 00:39:19,600 Speaker 1: weeks and months and years. Time scale is lost not 567 00:39:19,640 --> 00:39:24,239 Speaker 1: to unconsciousness, but to amnesia, where the person continues but 568 00:39:24,320 --> 00:39:28,480 Speaker 1: the story does not, a life lived but not remembered 569 00:39:28,520 --> 00:39:31,839 Speaker 1: because the timeline never makes it to the page. Then 570 00:39:31,880 --> 00:39:35,399 Speaker 1: we pushed it further to centuries and millennia, where even 571 00:39:35,440 --> 00:39:39,799 Speaker 1: our best efforts at understanding falter, where time becomes too 572 00:39:40,000 --> 00:39:45,120 Speaker 1: vast to meaningfully simulate it anymore. And finally, we looked 573 00:39:45,160 --> 00:39:48,560 Speaker 1: back into deep time, hundreds of millions of years, where 574 00:39:48,760 --> 00:39:53,239 Speaker 1: entire histories may have unfolded before us, only to be 575 00:39:53,320 --> 00:39:58,000 Speaker 1: erased by geology, by the quiet forgetting of a planet 576 00:39:58,160 --> 00:40:01,680 Speaker 1: with no memory. The wild part is that in all 577 00:40:01,680 --> 00:40:07,759 Speaker 1: these cases, we move forward, stitching together a story from fragments, 578 00:40:07,840 --> 00:40:10,800 Speaker 1: believing it to be complete. But it's important to remember 579 00:40:10,880 --> 00:40:13,680 Speaker 1: that we are the inheritors of a story that is 580 00:40:13,800 --> 00:40:16,920 Speaker 1: largely erased, and if you ask me, it's a story 581 00:40:16,920 --> 00:40:21,000 Speaker 1: that we do not fully understand, a story whose missing 582 00:40:21,080 --> 00:40:25,680 Speaker 1: pages occasionally outnumber the ones that we have. And yet 583 00:40:25,840 --> 00:40:28,560 Speaker 1: we keep telling our stories because that's all we've got. 584 00:40:29,000 --> 00:40:33,000 Speaker 1: So across all these scales milliseconds to eons, we see 585 00:40:33,040 --> 00:40:37,040 Speaker 1: a common thread. If events are not remembered, they might 586 00:40:37,080 --> 00:40:40,040 Speaker 1: as well not have happened. Our sense of time is 587 00:40:40,080 --> 00:40:44,759 Speaker 1: simply what gets recorded by anything from neurons to fossils. 588 00:40:45,120 --> 00:40:49,400 Speaker 1: When the record fails, the time disappears. So we assemble 589 00:40:49,520 --> 00:40:54,560 Speaker 1: our narrative from scraps moments we notice, memories, we hold, traces, 590 00:40:54,560 --> 00:40:59,120 Speaker 1: we dig from the earth, and what we call reality 591 00:40:59,320 --> 00:41:03,200 Speaker 1: is just the part that we managed to write down. 592 00:41:07,360 --> 00:41:10,360 Speaker 1: Go to eagleman dot com slash podcast more information and 593 00:41:10,360 --> 00:41:14,080 Speaker 1: to find further reading. Join the weekly discussions on my substack, 594 00:41:14,400 --> 00:41:17,000 Speaker 1: and check out and subscribe to Inner Cosmos on YouTube 595 00:41:17,000 --> 00:41:20,439 Speaker 1: for videos of each episode and to leave comments until 596 00:41:20,520 --> 00:41:23,920 Speaker 1: next time. I'm David Eagleman, and this is Inner Cosmos.