1 00:00:08,480 --> 00:00:12,680 Speaker 1: Hey, Daniel, what's the fastest a person has ever run? Well, 2 00:00:12,840 --> 00:00:16,200 Speaker 1: Hussain Bolt, the fastest person in history, actually only runs 3 00:00:16,239 --> 00:00:20,560 Speaker 1: about twenty miles per hour. But what's the fastest anything 4 00:00:20,600 --> 00:00:23,680 Speaker 1: has ever gone on Earth? That's about seven hundred and 5 00:00:23,720 --> 00:00:27,680 Speaker 1: sixty three miles per hour in a crazy rocket powered car. 6 00:00:28,200 --> 00:00:31,840 Speaker 1: That sounds like a good idea. But what about in space? 7 00:00:31,920 --> 00:00:34,519 Speaker 1: What's the fastest a spaceship has ever gone? There's the 8 00:00:34,560 --> 00:00:37,920 Speaker 1: Parker Solar Probe, which is whizzed around the Sun, and 9 00:00:37,960 --> 00:00:40,720 Speaker 1: it reached about five percent of the speed of light. 10 00:00:40,880 --> 00:00:43,960 Speaker 1: All right, so then technically nothing humans have ever made 11 00:00:44,400 --> 00:00:47,080 Speaker 1: has ever approached the speed of flight except for actual 12 00:00:47,159 --> 00:00:50,479 Speaker 1: light from flashlights. Oh well, but technically we made the flashlight, 13 00:00:50,479 --> 00:00:52,159 Speaker 1: but then the flashlight made the light. We want our 14 00:00:52,280 --> 00:00:54,560 Speaker 1: names on the pack as well? Yeah, can we label 15 00:00:54,560 --> 00:01:13,479 Speaker 1: each photon made by Jorge hi am or? Hey, I'm 16 00:01:13,480 --> 00:01:16,959 Speaker 1: a cartoonist and the creator of PhD comics. Hi, I'm Daniel. 17 00:01:17,000 --> 00:01:20,039 Speaker 1: I'm a particle physicist and the creator of many photons. 18 00:01:20,240 --> 00:01:22,400 Speaker 1: Oh really, you have a certain glow about you. Is 19 00:01:22,440 --> 00:01:24,560 Speaker 1: that what you're saying to all physicists? Glow? I think 20 00:01:24,680 --> 00:01:26,320 Speaker 1: usually it's not a good idea. If you're working with 21 00:01:26,560 --> 00:01:29,760 Speaker 1: radioactive things, especially if you come from Los Almos, then 22 00:01:29,800 --> 00:01:32,240 Speaker 1: you do tend to glow in the dark. But now 23 00:01:32,360 --> 00:01:34,760 Speaker 1: every single one of us gives up a unique pattern 24 00:01:34,880 --> 00:01:39,399 Speaker 1: of photons that we personally have crafted. My photons are artisanal. 25 00:01:39,560 --> 00:01:43,920 Speaker 1: Oh yeah, like you indivigitally craft each one. Yeah, they're 26 00:01:43,959 --> 00:01:46,120 Speaker 1: not very good. Isn't that what artisanal means? Yeah, I 27 00:01:46,120 --> 00:01:47,760 Speaker 1: guess what you mean is that you glow like in 28 00:01:47,760 --> 00:01:50,240 Speaker 1: the infrared, like from our body heat. Yeah, I definitely 29 00:01:50,280 --> 00:01:53,080 Speaker 1: do give off photons like every object in the universe, 30 00:01:53,160 --> 00:01:55,800 Speaker 1: if you have a temperature and then you glow. Sometimes 31 00:01:55,840 --> 00:01:57,800 Speaker 1: it's not in the visible light, but you definitely are 32 00:01:57,920 --> 00:02:00,560 Speaker 1: pumping out photons into the universe. Even if you are 33 00:02:00,600 --> 00:02:03,000 Speaker 1: a black hole, well then you are a shining example 34 00:02:03,040 --> 00:02:05,360 Speaker 1: I think for all of us. Welcome for our podcast, 35 00:02:05,480 --> 00:02:08,080 Speaker 1: Daniel and Jorge Explained the Universe, a production of I 36 00:02:08,200 --> 00:02:10,359 Speaker 1: Heart Radio in which we try to shine the light 37 00:02:10,400 --> 00:02:13,560 Speaker 1: of knowledge into your mind, pushing back on the forefront 38 00:02:13,560 --> 00:02:16,440 Speaker 1: of ignorance and talking about all of the biggest questions 39 00:02:16,520 --> 00:02:20,280 Speaker 1: in the universe, questions about the universe, questions around the universe, 40 00:02:20,360 --> 00:02:24,160 Speaker 1: questions in the universe, and questions from the universe, and 41 00:02:24,240 --> 00:02:25,720 Speaker 1: we talk about all of it and try to make 42 00:02:25,800 --> 00:02:28,440 Speaker 1: jokes to entertain you. Yeah, because there is a lot 43 00:02:28,480 --> 00:02:30,800 Speaker 1: in the universe out there that is bright and interesting 44 00:02:30,840 --> 00:02:34,040 Speaker 1: and powerful and curious and exciting, and there are also 45 00:02:34,240 --> 00:02:37,239 Speaker 1: dark things out there that are just escaped our site. 46 00:02:37,320 --> 00:02:39,520 Speaker 1: That's right. We can only see a little fraction of 47 00:02:39,560 --> 00:02:43,720 Speaker 1: the universe, an unknown fraction of the universe, because information 48 00:02:43,760 --> 00:02:46,399 Speaker 1: comes to us usually via light, and that light travels 49 00:02:46,440 --> 00:02:49,560 Speaker 1: at a very very fast but not infinite speed, and 50 00:02:49,600 --> 00:02:52,200 Speaker 1: we have learned all sorts of crazy things about how 51 00:02:52,240 --> 00:02:55,679 Speaker 1: information travels through the universe. Yeah, because the universe is 52 00:02:55,680 --> 00:02:58,480 Speaker 1: not just filled with mysterious things, it's also sort of 53 00:02:58,480 --> 00:03:02,800 Speaker 1: filled with mysterious rules. The rules of the universe are 54 00:03:02,919 --> 00:03:05,920 Speaker 1: not quite what we experience in an everyday basis, and 55 00:03:05,960 --> 00:03:08,640 Speaker 1: some of them kind of go against our intuition about 56 00:03:08,680 --> 00:03:11,320 Speaker 1: how things actually work. And thank God for that, or 57 00:03:11,400 --> 00:03:14,079 Speaker 1: my job would be boring. I think about science is 58 00:03:14,120 --> 00:03:16,959 Speaker 1: like a grand mystery novel. We're trying to figure out 59 00:03:17,000 --> 00:03:19,480 Speaker 1: how things work and deduce what the rules are from 60 00:03:19,520 --> 00:03:22,359 Speaker 1: the little clues left here and there. And you're absolutely 61 00:03:22,480 --> 00:03:24,079 Speaker 1: right that along the way we have figured out that 62 00:03:24,080 --> 00:03:26,480 Speaker 1: the universe is not the one we thought we were 63 00:03:26,480 --> 00:03:28,880 Speaker 1: living in, that the rules are weird, that the rules 64 00:03:28,880 --> 00:03:32,560 Speaker 1: are strange, that they require real creativity to on earth 65 00:03:32,600 --> 00:03:34,920 Speaker 1: how things actually work. Are you saying the universe is 66 00:03:34,920 --> 00:03:38,240 Speaker 1: not cliche? Thankfully, It's got it's twists and turns. I've 67 00:03:38,240 --> 00:03:41,600 Speaker 1: seen this universe so many times before. Oh my gosh, 68 00:03:42,200 --> 00:03:44,520 Speaker 1: bang crunch, bang, crunch, bang crunch. Hey do you think 69 00:03:44,520 --> 00:03:46,160 Speaker 1: every time there's a big bang and a big crunch 70 00:03:46,200 --> 00:03:48,360 Speaker 1: and we come back with the same universe that would 71 00:03:48,400 --> 00:03:50,760 Speaker 1: be boring? Yeah, obviously it was made by committee the 72 00:03:50,800 --> 00:03:55,000 Speaker 1: big bang. Let's just reboot the last universe that's sold 73 00:03:55,000 --> 00:03:59,320 Speaker 1: pretty well. Yeah right. Audiences don't want anything new. People 74 00:03:59,320 --> 00:04:01,440 Speaker 1: don't want to exist in the in a new universe. 75 00:04:01,720 --> 00:04:04,160 Speaker 1: This is the new J. J Abrams Big Bang theory. 76 00:04:04,360 --> 00:04:06,840 Speaker 1: Oh a dig on J. J Abrams. I feel like 77 00:04:06,960 --> 00:04:09,280 Speaker 1: you're always looking for an excuse there. Hey man, he 78 00:04:09,400 --> 00:04:11,920 Speaker 1: created the whole universe. You know, I got notes, but 79 00:04:12,000 --> 00:04:15,880 Speaker 1: it's pretty impressive. Wait. JJ Abrams created the whole universe 80 00:04:15,960 --> 00:04:18,760 Speaker 1: this theory. Yes, there's a J. J Abrams equivalent, you know, 81 00:04:18,880 --> 00:04:21,720 Speaker 1: writing the simulation or guiding the direction of the universe 82 00:04:22,040 --> 00:04:24,719 Speaker 1: that would explain all the lens flares, and I see 83 00:04:24,760 --> 00:04:26,600 Speaker 1: all the time when I look at the universe. But yeah, 84 00:04:26,640 --> 00:04:29,680 Speaker 1: it is a weird universe with weird rules, and there 85 00:04:29,760 --> 00:04:33,479 Speaker 1: is none weirder than special relativity, which is kind of 86 00:04:33,480 --> 00:04:36,400 Speaker 1: one of our main theories about the universe. That's right. 87 00:04:36,440 --> 00:04:38,880 Speaker 1: It turns out that when you start going really really quickly, 88 00:04:39,080 --> 00:04:42,000 Speaker 1: the rules that work at slow speeds down here on 89 00:04:42,040 --> 00:04:45,760 Speaker 1: Earth no longer apply. The rules are actually quite different, 90 00:04:45,800 --> 00:04:48,360 Speaker 1: and for hundreds and thousands of years we have been 91 00:04:48,440 --> 00:04:52,320 Speaker 1: learning rules that only work under special conditions, very very 92 00:04:52,400 --> 00:04:55,320 Speaker 1: slow movement. If you actually push the boundaries and start 93 00:04:55,320 --> 00:04:58,120 Speaker 1: going fast, the universe reveals that things we thought were 94 00:04:58,160 --> 00:05:01,200 Speaker 1: true are not actually true, leadings all sorts of weird 95 00:05:01,279 --> 00:05:04,960 Speaker 1: consequences that really violate our intuition. They break our notion 96 00:05:05,040 --> 00:05:09,279 Speaker 1: of like simultaneity and the idea of time being universal. Right. Yeah, 97 00:05:09,279 --> 00:05:11,240 Speaker 1: do you think like if we were all moving faster, 98 00:05:11,400 --> 00:05:14,520 Speaker 1: we would be used to these strange special rules, and 99 00:05:14,600 --> 00:05:17,120 Speaker 1: like our current rules would team we would have to 100 00:05:17,120 --> 00:05:19,920 Speaker 1: be moving really really fast. But I think in that 101 00:05:19,960 --> 00:05:23,240 Speaker 1: scenario our current rules would just be a natural extension 102 00:05:23,279 --> 00:05:26,080 Speaker 1: of what we already understood. But it's hard to imagine 103 00:05:26,120 --> 00:05:29,839 Speaker 1: growing up in a universe where special relativity feels intuitive, 104 00:05:30,000 --> 00:05:32,840 Speaker 1: where it makes sense to you, where our conclusions about 105 00:05:32,839 --> 00:05:35,760 Speaker 1: the universe would seem strange. But I'm sure somebody's written 106 00:05:35,760 --> 00:05:38,800 Speaker 1: that science fiction story, or maybe not. It's all there 107 00:05:38,800 --> 00:05:41,240 Speaker 1: for you, Daniel, somebody out there right it. But it's 108 00:05:41,279 --> 00:05:45,440 Speaker 1: called special relativity because it sort of applies to special situations. 109 00:05:45,480 --> 00:05:47,960 Speaker 1: Why does it have that special name? Special relativity is 110 00:05:47,960 --> 00:05:51,039 Speaker 1: called special because it's not general relativity. It applies to 111 00:05:51,120 --> 00:05:54,120 Speaker 1: scenarios where space is flat. We don't have to think 112 00:05:54,160 --> 00:05:57,440 Speaker 1: about space actually being curved and like changing the path 113 00:05:57,520 --> 00:06:00,920 Speaker 1: of photons or changing the motion of Earth around the star. 114 00:06:01,400 --> 00:06:03,200 Speaker 1: It has to do only with a sort of simpler 115 00:06:03,240 --> 00:06:06,280 Speaker 1: scenario where space is mostly empty and you're like shooting 116 00:06:06,360 --> 00:06:08,760 Speaker 1: laser pulses back and forth, or you have light bulbs 117 00:06:08,760 --> 00:06:11,520 Speaker 1: on trains. It has to do with relative velocities of 118 00:06:11,560 --> 00:06:14,640 Speaker 1: things and how information moves through the universe. It avoids 119 00:06:14,640 --> 00:06:18,240 Speaker 1: all complications from curved space. Oh really, wow, I never 120 00:06:18,320 --> 00:06:20,360 Speaker 1: knew that. I always thought that it was called special 121 00:06:20,400 --> 00:06:22,479 Speaker 1: relativity because it was special, But actually you're sort of 122 00:06:22,480 --> 00:06:25,360 Speaker 1: sitting the opposite. It's special because it only applies to 123 00:06:25,560 --> 00:06:28,880 Speaker 1: a boring universe. Yeah, it's a specialized condition. Right. He 124 00:06:29,000 --> 00:06:31,120 Speaker 1: came up with this first to understand this, and he thought, well, 125 00:06:31,120 --> 00:06:33,560 Speaker 1: you know, it's much trickier if space is actually curved, 126 00:06:33,920 --> 00:06:36,640 Speaker 1: and then he generalized it. He made it much more broad. 127 00:06:36,920 --> 00:06:40,479 Speaker 1: Special relativity is a subset of general relativity under the 128 00:06:40,480 --> 00:06:43,640 Speaker 1: conditions that basically the universe is mostly empty. You hadn't 129 00:06:43,640 --> 00:06:45,839 Speaker 1: figured that part out yet. So it's not like special 130 00:06:45,880 --> 00:06:48,800 Speaker 1: because people think it's like it ess special. It's just 131 00:06:48,839 --> 00:06:52,839 Speaker 1: special because actually it's like specially boring relativity that would 132 00:06:52,839 --> 00:06:56,200 Speaker 1: be technically more accurate. Right, Yeah, it's a special case. 133 00:06:56,240 --> 00:06:58,640 Speaker 1: It's not a better case. It's a simple case. But 134 00:06:58,680 --> 00:07:01,120 Speaker 1: we often do this in physics. We think about simple 135 00:07:01,200 --> 00:07:03,960 Speaker 1: scenarios to help us like distill what's going on and 136 00:07:04,000 --> 00:07:07,000 Speaker 1: get the clearest picture, so we can separate these ideas 137 00:07:07,040 --> 00:07:09,720 Speaker 1: because even in the scenario where you have no big 138 00:07:09,760 --> 00:07:12,520 Speaker 1: masses destroying the shape of space like black holes or 139 00:07:12,560 --> 00:07:14,720 Speaker 1: even just the sun, there are lots of weird things 140 00:07:14,720 --> 00:07:17,520 Speaker 1: that happened in special relativity. You know, clocks that don't 141 00:07:17,520 --> 00:07:20,080 Speaker 1: agree because you're moving at high speed. It's pretty weird 142 00:07:20,120 --> 00:07:22,360 Speaker 1: and hard to get your mind around. Even if there 143 00:07:22,440 --> 00:07:24,200 Speaker 1: is no curvature of space. So I think it was 144 00:07:24,240 --> 00:07:26,640 Speaker 1: sort of a good intellectual exercise. But even though it 145 00:07:26,640 --> 00:07:29,360 Speaker 1: applies to boring situations, it's still true, right, Like it's 146 00:07:29,400 --> 00:07:33,240 Speaker 1: still applies to the whole universe. It still applies to 147 00:07:33,280 --> 00:07:37,280 Speaker 1: the whole universe. The rules of special relativity do assume 148 00:07:37,640 --> 00:07:39,520 Speaker 1: that there are no heavy masses, and so if you 149 00:07:39,560 --> 00:07:43,120 Speaker 1: have big masses around curving space, you can't use calculations 150 00:07:43,120 --> 00:07:45,960 Speaker 1: from special relativity. You've got to use general relativity. But 151 00:07:46,000 --> 00:07:49,600 Speaker 1: I guess then the irony is that special relativity is 152 00:07:49,640 --> 00:07:53,520 Speaker 1: actually especially boring relativity. But it gives rise to these 153 00:07:53,560 --> 00:07:57,000 Speaker 1: really strange situations about the universe that don't seem to 154 00:07:57,040 --> 00:07:59,080 Speaker 1: make sense. And a lot of that has to do 155 00:07:59,280 --> 00:08:02,400 Speaker 1: with light experiments involving light. You know, there was this 156 00:08:02,480 --> 00:08:05,720 Speaker 1: famous experiment by Michaelson and Morley that showed that the 157 00:08:05,760 --> 00:08:08,320 Speaker 1: speed of light doesn't change no matter how fast the 158 00:08:08,360 --> 00:08:10,720 Speaker 1: Earth is moving through space. For example, that no matter 159 00:08:10,800 --> 00:08:14,000 Speaker 1: who measures a photon, they always measure it moving at 160 00:08:14,000 --> 00:08:16,680 Speaker 1: the speed of light, no matter how fast that person 161 00:08:16,800 --> 00:08:20,520 Speaker 1: is actually moving relative to anything else. It's pretty weird stuff. Yeah, 162 00:08:20,720 --> 00:08:24,120 Speaker 1: And so this weirdness is sort of a maybe especially 163 00:08:24,280 --> 00:08:27,360 Speaker 1: illustrated by asking a very simple question that you can 164 00:08:27,400 --> 00:08:29,320 Speaker 1: ask about the speed of light. So to be on 165 00:08:29,360 --> 00:08:37,079 Speaker 1: the podcast, we'll be asking the question is it possible 166 00:08:37,200 --> 00:08:41,679 Speaker 1: to outrun a flashlight? First of all, the flashlights run? 167 00:08:41,800 --> 00:08:43,720 Speaker 1: Do they have little legs that I don't know about? 168 00:08:43,880 --> 00:08:46,439 Speaker 1: Or that reminds me the old joke about refrigerators. Is 169 00:08:46,440 --> 00:08:49,000 Speaker 1: your refrigerator running? No, you better check the power. Your 170 00:08:49,040 --> 00:08:52,200 Speaker 1: flashlights don't actually run, of course, but the photons from 171 00:08:52,240 --> 00:08:56,040 Speaker 1: them come out at a blistering speed right of three 172 00:08:56,040 --> 00:08:58,880 Speaker 1: times tend the meters per second, So it's pretty hard 173 00:08:58,920 --> 00:09:01,640 Speaker 1: to imagine our pacing a flashlight. So it's more like, 174 00:09:01,800 --> 00:09:04,200 Speaker 1: is it possible to outrun a flash of light from 175 00:09:04,200 --> 00:09:07,120 Speaker 1: a flashlight? Yeah? I think the scenere I'm imagining is 176 00:09:07,320 --> 00:09:09,880 Speaker 1: you take off as your highest speed and I'm standing 177 00:09:09,880 --> 00:09:12,960 Speaker 1: behind you with a flashlight. Is it possible that once 178 00:09:13,040 --> 00:09:14,880 Speaker 1: I send off a flash of light, that you could 179 00:09:14,880 --> 00:09:17,560 Speaker 1: outpace it, that that flash of light would not catch you, 180 00:09:17,880 --> 00:09:19,880 Speaker 1: like it would not shine on me, like the photons 181 00:09:19,920 --> 00:09:23,080 Speaker 1: would never hit me. Yes, exactly. Or from your point 182 00:09:23,080 --> 00:09:25,400 Speaker 1: of view, is it possible you could run fast enough 183 00:09:25,440 --> 00:09:27,800 Speaker 1: that you could look backwards and you could not see 184 00:09:27,840 --> 00:09:29,920 Speaker 1: me right, that I would be passed some sort of 185 00:09:30,080 --> 00:09:33,440 Speaker 1: horizon beyond which you could not see. I see like 186 00:09:33,520 --> 00:09:35,839 Speaker 1: I would never know that you turned on the flashlight 187 00:09:36,000 --> 00:09:38,439 Speaker 1: because those photons would never reach me. Like I'll be 188 00:09:38,520 --> 00:09:43,800 Speaker 1: running and be like Daniel still hasn't but you did. 189 00:09:44,080 --> 00:09:46,120 Speaker 1: But it's the light would never reach me. And why 190 00:09:46,160 --> 00:09:48,000 Speaker 1: are you running away from me so quickly? What did 191 00:09:48,040 --> 00:09:51,120 Speaker 1: I don't know? Why are you shining a light on me? 192 00:09:51,920 --> 00:09:54,720 Speaker 1: What are you trying to do blind me? I'm just 193 00:09:54,720 --> 00:09:57,880 Speaker 1: playing flashlight tag? Man, chill out. So this applies to 194 00:09:58,080 --> 00:10:01,440 Speaker 1: that nineties toy laser tag, actually exactly. This helps you 195 00:10:01,480 --> 00:10:05,720 Speaker 1: strategize for laser tag. This is special relativity laser tag. Yeah, 196 00:10:05,720 --> 00:10:09,040 Speaker 1: physics is useful for all kinds of situations, even ones 197 00:10:09,080 --> 00:10:11,720 Speaker 1: that required to travel to the nineties and play laser tag. 198 00:10:11,880 --> 00:10:14,120 Speaker 1: I knew this degree would come in handy some day. Well, 199 00:10:14,120 --> 00:10:16,720 Speaker 1: at first, you have to solve time travel. I'm working 200 00:10:16,720 --> 00:10:18,839 Speaker 1: on it. I'm working on it, all right. So then 201 00:10:18,880 --> 00:10:21,240 Speaker 1: that's the scenario we're asking is if I take off 202 00:10:21,320 --> 00:10:23,800 Speaker 1: running and you shine a flashlight at me, is it 203 00:10:23,840 --> 00:10:26,439 Speaker 1: possible for me to outrun those photons or will they 204 00:10:26,480 --> 00:10:29,240 Speaker 1: inevitably hit me at some point in the future. So 205 00:10:29,280 --> 00:10:31,719 Speaker 1: that's a pretty interesting question, and so we thought we'd 206 00:10:31,800 --> 00:10:34,840 Speaker 1: post it to people on the internet and see what happens. 207 00:10:34,880 --> 00:10:37,400 Speaker 1: So usually Daniel went out there and ask listeners if 208 00:10:37,480 --> 00:10:41,440 Speaker 1: they thought that one could outrun a flash of light. 209 00:10:41,679 --> 00:10:44,440 Speaker 1: And so, as usual, I'm immensely grateful to all of 210 00:10:44,480 --> 00:10:47,079 Speaker 1: you who wanted to participate in the podcast and answer 211 00:10:47,160 --> 00:10:49,839 Speaker 1: these weird and random questions. If you're out there and 212 00:10:49,880 --> 00:10:52,000 Speaker 1: you're a listener to the podcast and you've been itching 213 00:10:52,040 --> 00:10:54,760 Speaker 1: to participate but you haven't quite yet, please send me 214 00:10:54,800 --> 00:10:57,600 Speaker 1: a message to questions at Daniel and Jorge dot com. 215 00:10:57,800 --> 00:10:59,200 Speaker 1: Think about it for a second. Do you think it 216 00:10:59,320 --> 00:11:03,080 Speaker 1: is possible to outrun a flashlight? Here's what people had 217 00:11:03,120 --> 00:11:08,520 Speaker 1: to say. Um, I don't think that I can. I'm 218 00:11:08,559 --> 00:11:10,640 Speaker 1: not faster than lights, so I don't think that I 219 00:11:10,679 --> 00:11:13,240 Speaker 1: could do that. I'd like to believe that you can 220 00:11:13,240 --> 00:11:16,440 Speaker 1: outrund a flashlight, but for that you have to be faster, 221 00:11:17,120 --> 00:11:19,760 Speaker 1: traveling faster than the speed of light, and as far 222 00:11:19,800 --> 00:11:22,280 Speaker 1: as I know, nothing in the universe can travel faster 223 00:11:22,360 --> 00:11:26,000 Speaker 1: than the speed of light. Yes, definitely, just don't throw 224 00:11:26,000 --> 00:11:28,920 Speaker 1: it too hard so you can, you know, run faster. 225 00:11:29,360 --> 00:11:32,719 Speaker 1: I think light from a flashlight travels its speeds much 226 00:11:32,840 --> 00:11:35,840 Speaker 1: less than the speed of lights and a vacuum that's 227 00:11:35,840 --> 00:11:38,920 Speaker 1: slowed down by the materials in its way as it 228 00:11:38,960 --> 00:11:42,680 Speaker 1: moves from inside the flashlight outside of it. And then 229 00:11:42,760 --> 00:11:46,000 Speaker 1: there are many different materials in the way, so because 230 00:11:46,040 --> 00:11:49,840 Speaker 1: of each material's index of refraction, the speed will be 231 00:11:49,880 --> 00:11:52,600 Speaker 1: reduced by a number of factors. As for whether I 232 00:11:52,720 --> 00:11:55,000 Speaker 1: can outrun it, I don't think so. I think it 233 00:11:55,040 --> 00:11:58,760 Speaker 1: will still be faster than my running speed. I guess 234 00:11:58,760 --> 00:12:02,040 Speaker 1: it depends on how fast it's the out No, if 235 00:12:02,160 --> 00:12:04,840 Speaker 1: if you actually mean the light itself, then nothing can 236 00:12:04,880 --> 00:12:09,480 Speaker 1: trovel a fast light, so you cannot let it. Sure, Yeah, 237 00:12:09,679 --> 00:12:13,800 Speaker 1: the flashlight itself is just like the box that that 238 00:12:14,040 --> 00:12:16,720 Speaker 1: sends out the light, right, So you could just set 239 00:12:16,720 --> 00:12:19,080 Speaker 1: the flashlight on the table and then run past it. 240 00:12:19,240 --> 00:12:22,760 Speaker 1: Would would outrun a flashlight? No, because it would really 241 00:12:22,840 --> 00:12:28,440 Speaker 1: piss s Einstein and also added additivity, I think maybe 242 00:12:28,480 --> 00:12:32,520 Speaker 1: the only way to kind of out run a flash 243 00:12:32,640 --> 00:12:36,760 Speaker 1: the light coming out of a flashlight would be maybe 244 00:12:36,840 --> 00:12:40,480 Speaker 1: if you could go through a worm hole. So if 245 00:12:40,480 --> 00:12:44,720 Speaker 1: the light from a flashlight, let's say, is headed towards 246 00:12:44,840 --> 00:12:49,000 Speaker 1: Jupiter and there's a wormhole between Earth and Jupiter, and 247 00:12:49,040 --> 00:12:53,280 Speaker 1: you took that shortcut in your spaceship m you could 248 00:12:53,400 --> 00:12:59,040 Speaker 1: probably hopefully get to Jupiter faster than the light from 249 00:12:59,040 --> 00:13:03,440 Speaker 1: your flashlight quid Rich Jupiter. No, you cannot outrun a 250 00:13:03,480 --> 00:13:07,800 Speaker 1: flashlight because the light traveling from the torch you're holding 251 00:13:08,160 --> 00:13:11,320 Speaker 1: will always be traveling at the speed of light relative 252 00:13:11,440 --> 00:13:13,880 Speaker 1: to you, so will always be traveling away from you 253 00:13:14,840 --> 00:13:18,280 Speaker 1: speed a light. All right, some pretty good answers here. 254 00:13:18,360 --> 00:13:21,800 Speaker 1: Somebody said you can't outrun the flashlight itself. I feel 255 00:13:21,840 --> 00:13:24,800 Speaker 1: like that's a different philosophical question, like can I throw 256 00:13:24,840 --> 00:13:28,400 Speaker 1: something at you that will always hit you? Yeah? Or 257 00:13:28,679 --> 00:13:31,320 Speaker 1: is the light part of the flashlight? After all? Will 258 00:13:31,360 --> 00:13:34,040 Speaker 1: always be the flashlight of infinite extent because of the 259 00:13:34,040 --> 00:13:36,000 Speaker 1: photons that come out of it. It's like the photon 260 00:13:36,080 --> 00:13:40,720 Speaker 1: of theseus kind of maybe the flashlight of theseus. Yeah, 261 00:13:40,960 --> 00:13:43,720 Speaker 1: Like is the photon from a flashlight part of the flashlight? 262 00:13:44,559 --> 00:13:47,360 Speaker 1: Bump bump bump. That's if somebody's thesis right there in 263 00:13:47,559 --> 00:13:50,880 Speaker 1: philosophy of science done? All right, I'll take that degree. 264 00:13:51,120 --> 00:13:53,400 Speaker 1: But yeah, lots of interesting answers here. Most people that 265 00:13:53,480 --> 00:13:55,720 Speaker 1: say that maybe not because you can't go faster than 266 00:13:55,760 --> 00:13:58,480 Speaker 1: the speed of light. So if light always goes as 267 00:13:58,520 --> 00:14:01,280 Speaker 1: fast as anything can go into universe, it will eventually 268 00:14:01,480 --> 00:14:03,880 Speaker 1: catch you, right, Yeah, and it's a very reasonable answer 269 00:14:03,920 --> 00:14:07,360 Speaker 1: given most people's understanding of special relativity. So yeah, I 270 00:14:07,360 --> 00:14:09,440 Speaker 1: see some clever answers here too, like what if there's 271 00:14:09,480 --> 00:14:13,480 Speaker 1: a wormhole? Did you think about that one? Yeah? But 272 00:14:13,720 --> 00:14:16,079 Speaker 1: why can't the light go through the wormhole? Also? Right, 273 00:14:16,280 --> 00:14:19,600 Speaker 1: if you run through photons right behind, you can't go 274 00:14:19,680 --> 00:14:21,680 Speaker 1: through the wormhole. So I guess if you open and 275 00:14:21,720 --> 00:14:25,800 Speaker 1: close that stargate really quickly, right, Yeah, Yeah, a lot 276 00:14:25,840 --> 00:14:28,760 Speaker 1: of clever answers here, but let's jump into answering this question, 277 00:14:28,800 --> 00:14:31,800 Speaker 1: can you out run a flash of light? And so 278 00:14:31,880 --> 00:14:33,760 Speaker 1: I guess maybe we should talk about a little bit 279 00:14:33,800 --> 00:14:36,120 Speaker 1: about this idea of the speed of light and special 280 00:14:36,160 --> 00:14:40,200 Speaker 1: relativity and why exactly it is kind of weird or 281 00:14:40,280 --> 00:14:42,840 Speaker 1: why weird things might happen if you try to this 282 00:14:42,960 --> 00:14:46,080 Speaker 1: experiment in space. Yeah, And the basic thing that we 283 00:14:46,120 --> 00:14:50,160 Speaker 1: need to understand is how different people measure velocity. Like 284 00:14:50,200 --> 00:14:52,800 Speaker 1: the way to think about it intuitively is imagine like 285 00:14:52,880 --> 00:14:56,040 Speaker 1: somebody throwing a natural object like a ball, if they 286 00:14:56,040 --> 00:14:58,200 Speaker 1: are in a car and they throw a ball forward 287 00:14:58,240 --> 00:15:00,200 Speaker 1: at ten miles an hour and then it's being a 288 00:15:00,280 --> 00:15:02,920 Speaker 1: ten miles an hour relative to them. No big deal. 289 00:15:03,040 --> 00:15:05,480 Speaker 1: But if the car is also driving at ten miles 290 00:15:05,480 --> 00:15:08,240 Speaker 1: an hour relative to the ground, then you might ask, well, 291 00:15:08,280 --> 00:15:11,000 Speaker 1: how fast is the ball moving relative to the ground. Well, 292 00:15:11,040 --> 00:15:13,560 Speaker 1: it's ten miles an hour relative to the car, and 293 00:15:13,600 --> 00:15:15,760 Speaker 1: the car is moving ten miles an hour relative to 294 00:15:15,800 --> 00:15:18,680 Speaker 1: the ground, So obviously twenty miles per hour, right, And 295 00:15:18,720 --> 00:15:21,400 Speaker 1: you think that's obvious and it's intuitive. And what you're 296 00:15:21,400 --> 00:15:24,440 Speaker 1: doing there is you're applying a rule which you sort 297 00:15:24,440 --> 00:15:27,360 Speaker 1: of intuitely we have figured out and applied, and it's 298 00:15:27,400 --> 00:15:30,800 Speaker 1: a Galilean transformation. It says, the speed of the ball 299 00:15:30,800 --> 00:15:33,320 Speaker 1: relative to the ground is the speed of the ball 300 00:15:33,360 --> 00:15:35,440 Speaker 1: relative to the car plus the speed of the car 301 00:15:35,600 --> 00:15:38,440 Speaker 1: relative to the ground. And that mostly works. But what 302 00:15:38,480 --> 00:15:41,000 Speaker 1: we discovered is that it's not true at very very 303 00:15:41,120 --> 00:15:45,160 Speaker 1: high speeds, and most specifically, it's not true for light. 304 00:15:45,440 --> 00:15:47,480 Speaker 1: So if I'm standing in a car and I shine 305 00:15:47,520 --> 00:15:51,520 Speaker 1: a flashlight, how fast is the light leaving my flashlight? Well, 306 00:15:51,760 --> 00:15:54,000 Speaker 1: the speed of light right now, the car is moving 307 00:15:54,000 --> 00:15:56,600 Speaker 1: in ten miles per hour. How fast is the light 308 00:15:56,640 --> 00:16:00,520 Speaker 1: traveling relative to the ground. Well, you're old rule would say, well, 309 00:16:00,560 --> 00:16:03,480 Speaker 1: if the speed of light plus ten miles per hour, right, 310 00:16:03,560 --> 00:16:06,440 Speaker 1: like faster than the speed of light. But that can't happen. 311 00:16:06,880 --> 00:16:09,400 Speaker 1: And so the light always travels at the speed of light, 312 00:16:09,440 --> 00:16:12,120 Speaker 1: no matter who's measuring it and how fast they are 313 00:16:12,160 --> 00:16:14,480 Speaker 1: going relative to the thing that made the light. So 314 00:16:14,560 --> 00:16:16,720 Speaker 1: the person in the car measures the photon is going 315 00:16:16,720 --> 00:16:18,560 Speaker 1: at the speed of light, and the person on the 316 00:16:18,600 --> 00:16:21,880 Speaker 1: ground measures the photon and going at the speed of light. Right, Yeah, 317 00:16:21,920 --> 00:16:25,000 Speaker 1: you had me on galilee and transformation. I think what 318 00:16:25,040 --> 00:16:26,720 Speaker 1: you're saying is that, you know, we're used in our 319 00:16:26,720 --> 00:16:30,600 Speaker 1: everyday lives this idea that velocities like add like they 320 00:16:30,720 --> 00:16:33,680 Speaker 1: add with simple like arithmetic, like you know one plus 321 00:16:33,680 --> 00:16:36,240 Speaker 1: one equals too, but that things get weird with the 322 00:16:36,240 --> 00:16:38,560 Speaker 1: speed of light because nothing can go faster than the 323 00:16:38,560 --> 00:16:41,400 Speaker 1: speed of light. So like you can't keep adding velocities 324 00:16:41,800 --> 00:16:44,480 Speaker 1: because that would eventually make them go faster than the 325 00:16:44,480 --> 00:16:47,560 Speaker 1: speed of light. Yeah, they add nonlinearly, right, so they 326 00:16:47,560 --> 00:16:49,640 Speaker 1: get closer and closer to the speed of light, but 327 00:16:49,640 --> 00:16:51,600 Speaker 1: they don't just stack up on top of each other 328 00:16:51,640 --> 00:16:53,880 Speaker 1: in a simple way. And so as you say things 329 00:16:53,920 --> 00:16:56,760 Speaker 1: with masking get faster and faster and approached the speed 330 00:16:56,800 --> 00:16:58,960 Speaker 1: of light. But nothing can go faster than the speed 331 00:16:59,000 --> 00:17:00,320 Speaker 1: of light, and so you have to have an new 332 00:17:00,360 --> 00:17:03,480 Speaker 1: addition rule. It doesn't just like A plus B. It's 333 00:17:03,480 --> 00:17:05,600 Speaker 1: some weird combination of A and B that helps you 334 00:17:05,640 --> 00:17:08,119 Speaker 1: approach the speed of light but never gets you past it. 335 00:17:08,200 --> 00:17:11,320 Speaker 1: And for light itself, it's always at the speed of light, 336 00:17:11,480 --> 00:17:15,240 Speaker 1: never slower, never faster, right, It's kind of this weird thing. 337 00:17:15,320 --> 00:17:18,119 Speaker 1: Like if you're a photon that's shooting out of a flashlight, 338 00:17:18,160 --> 00:17:20,240 Speaker 1: and so you're going at the speed of light, and 339 00:17:20,240 --> 00:17:22,920 Speaker 1: then somehow you as that photon shoot off another photon 340 00:17:23,280 --> 00:17:26,359 Speaker 1: in front of you, that photon is not gonna go 341 00:17:26,480 --> 00:17:28,040 Speaker 1: like a twice the speed of light. It's going to 342 00:17:28,160 --> 00:17:31,239 Speaker 1: go still at the speed of light. That's exactly right. 343 00:17:31,280 --> 00:17:34,320 Speaker 1: Although a photon itself can't have a frame of reference 344 00:17:34,520 --> 00:17:37,320 Speaker 1: because photon can't be at rest, so you can't measure 345 00:17:37,320 --> 00:17:40,120 Speaker 1: the speed of one photon relative to another one, which 346 00:17:40,160 --> 00:17:43,200 Speaker 1: is another for the tricky little wrinkle there. But exactly 347 00:17:43,280 --> 00:17:45,720 Speaker 1: if somebody's flying in a spaceship near the speed of 348 00:17:45,760 --> 00:17:48,240 Speaker 1: light relative to Earth and they turn on a flashlight, 349 00:17:48,320 --> 00:17:51,760 Speaker 1: that photon is not going at like one times the 350 00:17:51,800 --> 00:17:54,600 Speaker 1: speed of light relative to Earth. It's only moving at 351 00:17:54,640 --> 00:17:57,680 Speaker 1: the speed of light. And that's pretty weird, right, because 352 00:17:57,720 --> 00:17:59,960 Speaker 1: these things no longer add up. It's like the people 353 00:18:00,000 --> 00:18:02,800 Speaker 1: in the spaceship tell a different story about what happened 354 00:18:02,960 --> 00:18:05,200 Speaker 1: than the people on Earth. Because the people on Earth 355 00:18:05,240 --> 00:18:08,080 Speaker 1: see that floton as moving at near the speed of light, 356 00:18:08,400 --> 00:18:11,160 Speaker 1: it's relative speed to the ship is actually quite small, 357 00:18:11,480 --> 00:18:13,720 Speaker 1: whereas on the ship that people see the photon is 358 00:18:13,720 --> 00:18:16,119 Speaker 1: moving away from them at the speed of light. And 359 00:18:16,119 --> 00:18:18,440 Speaker 1: so you get like a different story about what happened. 360 00:18:18,640 --> 00:18:21,359 Speaker 1: And that's the mind bending thing about special relativities, that 361 00:18:21,640 --> 00:18:25,040 Speaker 1: different observers tell different stories about what happened, and they're 362 00:18:25,040 --> 00:18:29,120 Speaker 1: both accurate. They're both like honest observers telling conflicting stories 363 00:18:29,200 --> 00:18:31,719 Speaker 1: and both being correct. But I guess it's not about 364 00:18:32,000 --> 00:18:35,040 Speaker 1: different things happening. It's more about our perception of these 365 00:18:35,040 --> 00:18:37,879 Speaker 1: things happening, maybe because it's all related to how it 366 00:18:37,920 --> 00:18:42,040 Speaker 1: affects time, right, like time is sort of flexible, time 367 00:18:42,119 --> 00:18:45,680 Speaker 1: is not universal, and exactly we don't have a consistent 368 00:18:45,760 --> 00:18:48,720 Speaker 1: clock through the whole universe that says like what happened 369 00:18:48,760 --> 00:18:51,600 Speaker 1: at every moment, and then what happened at the next moment. 370 00:18:51,960 --> 00:18:54,920 Speaker 1: What happens depends on where you are and how fast 371 00:18:54,960 --> 00:18:58,159 Speaker 1: you are going relative to the events, and sometimes this 372 00:18:58,280 --> 00:19:01,159 Speaker 1: flexibility there. If there's no like causal connection where one 373 00:19:01,200 --> 00:19:03,639 Speaker 1: thing has to happen before another, then different people can 374 00:19:03,640 --> 00:19:06,960 Speaker 1: give different orders of events for what happened and both 375 00:19:06,960 --> 00:19:09,919 Speaker 1: be correct. It's not just an issue of perception. Although 376 00:19:09,960 --> 00:19:12,440 Speaker 1: you can, you know, use special relativity to say, well, 377 00:19:12,520 --> 00:19:15,040 Speaker 1: I understand why you are seeing the opposite thing that 378 00:19:15,080 --> 00:19:18,080 Speaker 1: I'm seeing. That's because of special relativity, but neither of 379 00:19:18,080 --> 00:19:20,240 Speaker 1: you can say like A happen before b or be 380 00:19:20,359 --> 00:19:23,359 Speaker 1: happen for a It depends on who you are and 381 00:19:23,400 --> 00:19:27,040 Speaker 1: how fast you're going. Right, It's like nobody's clock is official. 382 00:19:27,160 --> 00:19:29,640 Speaker 1: Everyone has a different clock, and so that you can't 383 00:19:29,640 --> 00:19:31,840 Speaker 1: sort of say, like who's right or who's wrong, because 384 00:19:31,840 --> 00:19:36,160 Speaker 1: in the end, everything is relative. Right, velocity itself is relative. 385 00:19:36,240 --> 00:19:38,320 Speaker 1: You can't have a velocity just on its own. You 386 00:19:38,359 --> 00:19:40,680 Speaker 1: can't say my spaceship is going at the speed of 387 00:19:40,800 --> 00:19:44,639 Speaker 1: light and say well relative to what right, As we 388 00:19:44,640 --> 00:19:47,359 Speaker 1: talked about once recently, like velocity doesn't even have a 389 00:19:47,480 --> 00:19:50,760 Speaker 1: meaning if you are in a universe all by yourself, like, 390 00:19:50,840 --> 00:19:53,080 Speaker 1: you can't have a speed if there's nothing else in 391 00:19:53,119 --> 00:19:55,480 Speaker 1: the universe. So it's a whole new way to think 392 00:19:55,520 --> 00:19:58,480 Speaker 1: about the nature of the universe and all these weird consequences, 393 00:19:58,520 --> 00:20:00,680 Speaker 1: a lot of which come from this idea that light 394 00:20:00,720 --> 00:20:03,280 Speaker 1: always travels at the speed of light. Yeah, So while 395 00:20:03,280 --> 00:20:05,800 Speaker 1: it may seem intuitive that if you shine a flashlight 396 00:20:05,840 --> 00:20:08,080 Speaker 1: at me, no matter how fast I'm going, that light 397 00:20:08,119 --> 00:20:10,119 Speaker 1: is going to catch up to me, that may not 398 00:20:10,240 --> 00:20:14,400 Speaker 1: actually be true depending on some of these weird consequences 399 00:20:14,400 --> 00:20:17,480 Speaker 1: of special relativity. That's right in a simple case where 400 00:20:17,520 --> 00:20:20,159 Speaker 1: you're like in a normal universe and space is flat 401 00:20:20,240 --> 00:20:22,919 Speaker 1: and it's obeying these rules, then if somebody shines a 402 00:20:22,960 --> 00:20:26,240 Speaker 1: flashlight in your direction, it doesn't matter how far away 403 00:20:26,280 --> 00:20:29,320 Speaker 1: they are. Eventually that light will reach you. There's no 404 00:20:29,440 --> 00:20:32,520 Speaker 1: like effective horizon, give an infinite time, that photon will 405 00:20:32,560 --> 00:20:35,520 Speaker 1: catch you. There's nothing you can do, right, and that's 406 00:20:35,560 --> 00:20:38,040 Speaker 1: because it's moving at the speed of light relative to you. 407 00:20:38,119 --> 00:20:40,560 Speaker 1: Because light always moves at the speed of light. So 408 00:20:40,640 --> 00:20:43,119 Speaker 1: in this sort of simple universe where space is not curved, 409 00:20:43,160 --> 00:20:45,800 Speaker 1: nothing weird is going on. That flash of light will 410 00:20:45,800 --> 00:20:49,000 Speaker 1: always catch you, right. But in our universe, the answer 411 00:20:49,200 --> 00:20:52,040 Speaker 1: might be different. But first, let's take a quick break. 412 00:21:04,520 --> 00:21:07,080 Speaker 1: All right, Daniel, you're trying to outrun a flashlight. I 413 00:21:07,119 --> 00:21:08,720 Speaker 1: don't know why. I guess you don't want people to 414 00:21:08,760 --> 00:21:11,159 Speaker 1: see you, or you want to remain sort of in 415 00:21:11,200 --> 00:21:13,639 Speaker 1: the dark and mysterious. But you're trying to outrun a 416 00:21:13,680 --> 00:21:16,639 Speaker 1: flashlight and somebody's shying a flashlight on you, and so 417 00:21:16,720 --> 00:21:19,080 Speaker 1: it seems like it would inevitably the light would reach 418 00:21:19,119 --> 00:21:21,679 Speaker 1: me because it's going faster than anything can go in 419 00:21:21,720 --> 00:21:24,639 Speaker 1: the universe. But you're saying there might be some instances 420 00:21:24,640 --> 00:21:28,320 Speaker 1: where I can actually outrun light. Mm hmmmm. And you 421 00:21:28,359 --> 00:21:30,920 Speaker 1: know this is not just a silly physics thought experiment. 422 00:21:30,960 --> 00:21:33,119 Speaker 1: This is really important. If you were playing laser tag 423 00:21:33,480 --> 00:21:35,480 Speaker 1: and you're cornered and they shoot that thing right at you, 424 00:21:35,560 --> 00:21:37,760 Speaker 1: you gotta find a way to escape. And so that's 425 00:21:37,760 --> 00:21:40,719 Speaker 1: where we come in, right. This is totally serious and 426 00:21:40,840 --> 00:21:44,280 Speaker 1: totally relevant to everyone's everyday lighte No, there are some 427 00:21:44,400 --> 00:21:47,320 Speaker 1: scenarios where somebody points a flashlight at you and it 428 00:21:47,400 --> 00:21:51,159 Speaker 1: doesn't ever hit you even an infinite time, even if 429 00:21:51,200 --> 00:21:53,600 Speaker 1: it's pointed right at you, and you don't actually even 430 00:21:53,640 --> 00:21:56,440 Speaker 1: have to be moving to avoid it. In some scenarios. 431 00:21:56,440 --> 00:21:58,919 Speaker 1: So you might have heard my sort of legalistic maneuver 432 00:21:59,000 --> 00:22:01,760 Speaker 1: there to avoid saying that the flashlight will always catch you. 433 00:22:02,119 --> 00:22:05,399 Speaker 1: The condition is that if you are operating in flat space, 434 00:22:05,480 --> 00:22:08,720 Speaker 1: in space, that's just where general relativity applies, and nothing 435 00:22:08,840 --> 00:22:11,760 Speaker 1: is growing or shrinking. Right, So that gives us one 436 00:22:11,840 --> 00:22:14,200 Speaker 1: that maybe the first instance in which you could maybe 437 00:22:14,200 --> 00:22:16,600 Speaker 1: outrun a flashlight. Right. It has to do with this 438 00:22:16,640 --> 00:22:20,280 Speaker 1: idea that space is not actually flat or constant or 439 00:22:20,640 --> 00:22:23,320 Speaker 1: kind of boring. Yeah, it turns out that our universe 440 00:22:23,520 --> 00:22:26,840 Speaker 1: is a lot more exciting than the special relativity universe, right. 441 00:22:26,960 --> 00:22:30,600 Speaker 1: Most importantly, our universe is expanding. Now, A lot of 442 00:22:30,600 --> 00:22:33,600 Speaker 1: people think that that means that galaxies are flying out 443 00:22:33,640 --> 00:22:36,399 Speaker 1: from some sort of central dot at a high speed, 444 00:22:36,400 --> 00:22:39,400 Speaker 1: that they're moving through space. But it's actually much weirder 445 00:22:39,440 --> 00:22:44,160 Speaker 1: and more amazing than that. It's the expansion of space itself. Right. 446 00:22:44,160 --> 00:22:46,440 Speaker 1: It's not the motion of things through space. I mean 447 00:22:46,440 --> 00:22:50,080 Speaker 1: that's also happening, but dark energy. There's accelerating expansion of 448 00:22:50,119 --> 00:22:54,280 Speaker 1: the universe. This is creating new space between our galaxy 449 00:22:54,320 --> 00:22:57,920 Speaker 1: and other galaxies. It's not just moving the galaxies through 450 00:22:58,000 --> 00:23:01,040 Speaker 1: the existing space. It's like stre watching the fabric of 451 00:23:01,040 --> 00:23:03,800 Speaker 1: the universe itself. Right, I think that you're saying sort 452 00:23:03,800 --> 00:23:06,600 Speaker 1: of like maybe I could outrun Hussein Bold if maybe 453 00:23:06,600 --> 00:23:08,840 Speaker 1: I play around with the track, or like how the 454 00:23:08,840 --> 00:23:12,919 Speaker 1: track is moving. Yeah, exactly. Put Usain Bolt on a 455 00:23:12,920 --> 00:23:14,960 Speaker 1: treadmill and stand in front of the treadmill. It doesn't 456 00:23:15,000 --> 00:23:18,640 Speaker 1: matter how fast he runs, That's what I mean. Yeah. Yeah, 457 00:23:18,680 --> 00:23:22,600 Speaker 1: And in the same way, the universe is laying new track, 458 00:23:22,800 --> 00:23:26,680 Speaker 1: new space between us and some really really distant photons, 459 00:23:26,960 --> 00:23:30,000 Speaker 1: photons which left their galaxy or their star billions of 460 00:23:30,080 --> 00:23:33,000 Speaker 1: years ago and they've been straining to reach us. Some 461 00:23:33,080 --> 00:23:35,440 Speaker 1: of them will never get to us, even though they're 462 00:23:35,560 --> 00:23:38,479 Speaker 1: pointed right at us, because the space between us and 463 00:23:38,480 --> 00:23:41,439 Speaker 1: them is expanding faster than light can go through it, 464 00:23:41,560 --> 00:23:44,160 Speaker 1: faster than the speed of light. Right. Well, it's it's 465 00:23:44,160 --> 00:23:46,960 Speaker 1: not that the space itself at any given point is 466 00:23:47,000 --> 00:23:49,200 Speaker 1: expanding faster than the speed of light. But it's more 467 00:23:49,280 --> 00:23:52,760 Speaker 1: like there's so much space in between, and it's growing 468 00:23:52,760 --> 00:23:56,000 Speaker 1: a little bit at each spot, so much that it 469 00:23:56,960 --> 00:23:59,960 Speaker 1: overall is expanding faster than the speed of light. Yes, 470 00:24:00,000 --> 00:24:02,600 Speaker 1: it's a very gentle effect on a local scale. Right, 471 00:24:02,760 --> 00:24:05,399 Speaker 1: It's not like the distance between you and your partner, 472 00:24:05,640 --> 00:24:08,320 Speaker 1: or between the Earth and the Sun is growing very 473 00:24:08,400 --> 00:24:11,920 Speaker 1: very rapidly. Right, It's a very gentle effect over small distances. 474 00:24:12,160 --> 00:24:15,359 Speaker 1: But as you say, larger distances, it adds up, right, 475 00:24:15,440 --> 00:24:18,520 Speaker 1: And so between our star and the next star, the 476 00:24:18,600 --> 00:24:21,960 Speaker 1: acceleration is a larger number. Between our galaxy and the 477 00:24:21,960 --> 00:24:24,920 Speaker 1: next galaxy is an even bigger number between really really 478 00:24:25,000 --> 00:24:28,399 Speaker 1: distant objects. Then that speed is faster than the speed 479 00:24:28,400 --> 00:24:31,240 Speaker 1: of light. The space is being created faster than the 480 00:24:31,320 --> 00:24:33,639 Speaker 1: light can go through it. Right, So I guess maybe 481 00:24:33,640 --> 00:24:35,760 Speaker 1: paint the scenario out for us, Like if I wanted 482 00:24:35,800 --> 00:24:38,399 Speaker 1: to outrun a flash of light from a flashlight, how 483 00:24:38,440 --> 00:24:40,040 Speaker 1: would I do this? Like, we can't start in the 484 00:24:40,080 --> 00:24:41,879 Speaker 1: same spot. I would have to go away from you 485 00:24:42,000 --> 00:24:44,719 Speaker 1: for a while, right, or a certain amount of distance. 486 00:24:44,880 --> 00:24:46,520 Speaker 1: That's right, If you start from the same spot as 487 00:24:46,520 --> 00:24:48,760 Speaker 1: the photon, it's going to catch you instantly, Like you 488 00:24:48,800 --> 00:24:51,400 Speaker 1: know by definition. If I'm holding the flashlight to your 489 00:24:51,440 --> 00:24:53,520 Speaker 1: back and I press the button as soon as you 490 00:24:53,520 --> 00:24:56,399 Speaker 1: start running, I caught you before you've even gone anywhere, Right, 491 00:24:56,440 --> 00:24:59,040 Speaker 1: A T equal zero? Right if we're both like standing 492 00:24:59,119 --> 00:25:01,399 Speaker 1: next to each other. Yeah, But if I give you 493 00:25:01,400 --> 00:25:03,760 Speaker 1: a head start, and you start running, right, and you 494 00:25:03,800 --> 00:25:05,840 Speaker 1: get a little distance, you get ten ms or so, 495 00:25:06,080 --> 00:25:10,400 Speaker 1: or ten seconds before I shine the flashlight. Then if 496 00:25:10,480 --> 00:25:14,720 Speaker 1: space is expanding between the flashlight and how far you 497 00:25:14,840 --> 00:25:17,840 Speaker 1: got before I turned the flashlight on, then it might 498 00:25:17,880 --> 00:25:20,439 Speaker 1: be that that photon never makes it through that space 499 00:25:20,480 --> 00:25:22,720 Speaker 1: to catch you. Right. Well, let's take it one step 500 00:25:22,720 --> 00:25:24,919 Speaker 1: at a time. Let's say I fly to Jupiter, or 501 00:25:24,960 --> 00:25:26,760 Speaker 1: you let me run to Jupiter before you turn on 502 00:25:26,840 --> 00:25:29,000 Speaker 1: the flashlight. So now I mean, but in Jupiter and 503 00:25:29,000 --> 00:25:31,480 Speaker 1: I'm running somehow in space, and then you shine a 504 00:25:31,560 --> 00:25:33,720 Speaker 1: flashlight on me. It's going to take a while, but 505 00:25:33,840 --> 00:25:36,240 Speaker 1: it will catch me at that point, right, Eventually it 506 00:25:36,280 --> 00:25:38,760 Speaker 1: will catch you at that point, Yes, because the expansion 507 00:25:38,800 --> 00:25:41,400 Speaker 1: of space between here and Jupiter is not that impressive, 508 00:25:41,600 --> 00:25:45,080 Speaker 1: not enough to overcome the speed of the photon. Right, 509 00:25:45,160 --> 00:25:48,080 Speaker 1: It's like the space is growing a little bit, maybe 510 00:25:48,160 --> 00:25:52,040 Speaker 1: like what like a millimeter or something per year or something. Yeah, 511 00:25:52,080 --> 00:25:53,800 Speaker 1: And a lot of people ask this question, They say, 512 00:25:53,840 --> 00:25:55,959 Speaker 1: why can't we see the expansion of space and our 513 00:25:56,000 --> 00:25:58,560 Speaker 1: solar system? Why isn't it tearing things apart? Well, the 514 00:25:58,600 --> 00:26:02,719 Speaker 1: reason is that gravity is pretty strong on a local scale, right, 515 00:26:02,760 --> 00:26:04,960 Speaker 1: Remember it goes like one who were distant squared, and 516 00:26:05,000 --> 00:26:07,720 Speaker 1: so the distances are pretty small, like Earth to Jupiter. 517 00:26:08,080 --> 00:26:11,199 Speaker 1: Then gravity is more powerful than dark energy, so the 518 00:26:11,280 --> 00:26:14,399 Speaker 1: Solar system holds itself together. So the distance between the 519 00:26:14,400 --> 00:26:16,600 Speaker 1: Sun and Jupiter is not actually growing at all due 520 00:26:16,600 --> 00:26:19,240 Speaker 1: to the expansion of the universe, because they're holding tight 521 00:26:19,280 --> 00:26:21,040 Speaker 1: onto each other, the same way the Earth and the 522 00:26:21,040 --> 00:26:23,120 Speaker 1: Moon are, or the same way the atoms in your 523 00:26:23,119 --> 00:26:25,360 Speaker 1: body are holding on to each other. So that's why 524 00:26:25,359 --> 00:26:28,359 Speaker 1: we only really see this thing between galaxies or even 525 00:26:28,400 --> 00:26:32,840 Speaker 1: between galaxy clusters, because smaller than that, gravity sort of wins. 526 00:26:32,880 --> 00:26:36,200 Speaker 1: It's like tying everybody together. Imagine like a gentle breeze 527 00:26:36,240 --> 00:26:38,840 Speaker 1: is blowing out everywhere, but people are holding on to 528 00:26:38,920 --> 00:26:40,800 Speaker 1: each other and so they're able to resist it. But 529 00:26:41,040 --> 00:26:44,919 Speaker 1: over large distances, this breeze adds up and it becomes 530 00:26:44,920 --> 00:26:48,800 Speaker 1: a really powerful force. It's a breezy universe. Alright. Well, 531 00:26:48,880 --> 00:26:50,560 Speaker 1: let's say then that you give me a really big 532 00:26:50,560 --> 00:26:53,960 Speaker 1: head start and I start running at the nearest galaxy, 533 00:26:54,000 --> 00:26:58,520 Speaker 1: which I think is Andromeda. Andromeda. Yeah, I was about 534 00:26:58,560 --> 00:27:00,560 Speaker 1: to say that. So let's say you let me get 535 00:27:00,600 --> 00:27:02,679 Speaker 1: as far as in Drameda and then I start running, 536 00:27:02,680 --> 00:27:05,040 Speaker 1: and then you shine a flash light on me, It's 537 00:27:05,040 --> 00:27:07,120 Speaker 1: still gonna catch me. It's still gonna catch you because 538 00:27:07,119 --> 00:27:09,320 Speaker 1: the expansion of space between here and Andromeda is not 539 00:27:09,400 --> 00:27:13,000 Speaker 1: that impressive, right, So, like, I'll start running, and how 540 00:27:13,040 --> 00:27:16,160 Speaker 1: far is Andromeda? Like eight millions of light years? Will 541 00:27:16,200 --> 00:27:18,280 Speaker 1: take millions of light years for the light to sort 542 00:27:18,280 --> 00:27:21,399 Speaker 1: of get to where I'm running, And in those millions 543 00:27:21,440 --> 00:27:23,640 Speaker 1: of years, I will also have run a good bit. 544 00:27:23,800 --> 00:27:26,840 Speaker 1: But eventually those two things will catch up, right, Like 545 00:27:26,880 --> 00:27:29,439 Speaker 1: the light will eventually. It might take millions of years, 546 00:27:29,440 --> 00:27:31,640 Speaker 1: but it'll light will eventually hit me in the back. 547 00:27:31,760 --> 00:27:33,680 Speaker 1: That's right. If you are running a constant speed, like 548 00:27:33,760 --> 00:27:35,919 Speaker 1: let's say you were running at half the speed of 549 00:27:35,960 --> 00:27:38,639 Speaker 1: light because you're super impressive relative to the Earth, and 550 00:27:38,640 --> 00:27:41,200 Speaker 1: I shine that flashlight at the speed of light, then 551 00:27:41,200 --> 00:27:43,280 Speaker 1: it will eventually catch you. And you'll look back at 552 00:27:43,280 --> 00:27:45,040 Speaker 1: the flashlight and you'll say, oh, that light is moving 553 00:27:45,080 --> 00:27:47,159 Speaker 1: at the speed of light relative to me, and it 554 00:27:47,200 --> 00:27:49,960 Speaker 1: will catch up to you, you know, in several million years, 555 00:27:50,000 --> 00:27:53,520 Speaker 1: if you are several million light years ahead when it begins. 556 00:27:53,800 --> 00:27:56,080 Speaker 1: But I see, if you're moving at constant speed and 557 00:27:56,080 --> 00:27:58,919 Speaker 1: there's not that much expansion of the space between us 558 00:27:58,920 --> 00:28:01,600 Speaker 1: and between us and Drama. H it's not enough for 559 00:28:01,640 --> 00:28:04,240 Speaker 1: you to outrun the flashlight, right, Like the space between 560 00:28:04,280 --> 00:28:07,119 Speaker 1: here and Drama is is expanding, but it's maybe expanding 561 00:28:07,200 --> 00:28:10,320 Speaker 1: at I don't know, ten meters per second or something. 562 00:28:10,440 --> 00:28:12,960 Speaker 1: That's right, And you know there's a little wrinkled there 563 00:28:12,960 --> 00:28:15,800 Speaker 1: because in Drama actually happens to be moving towards us 564 00:28:15,920 --> 00:28:18,640 Speaker 1: even though the space is expanding between us, gravity there 565 00:28:18,720 --> 00:28:21,280 Speaker 1: is winning and it's pulling and Drameda towards us, and 566 00:28:21,359 --> 00:28:24,920 Speaker 1: you know their local deviations, Like space itself is expanding, 567 00:28:24,920 --> 00:28:27,399 Speaker 1: but things are still moving through that space as we 568 00:28:27,480 --> 00:28:30,240 Speaker 1: talked about, like driven by gravity and other forces. So 569 00:28:30,280 --> 00:28:33,359 Speaker 1: Andrameda is getting closer to us, even though the space 570 00:28:33,440 --> 00:28:36,439 Speaker 1: is expanding, sort of sort of like swimming upstream against 571 00:28:36,440 --> 00:28:39,480 Speaker 1: that expansion, right, I guess I'm just saying, like Andrama 572 00:28:39,560 --> 00:28:41,440 Speaker 1: is where I start running, not that I stay with 573 00:28:41,440 --> 00:28:43,680 Speaker 1: and Drameda, right, Right, even if you start running from 574 00:28:43,680 --> 00:28:46,280 Speaker 1: Andrameda and go past it, then that photon will still 575 00:28:46,320 --> 00:28:48,400 Speaker 1: catch you. The expansion of the universe not enough to 576 00:28:48,440 --> 00:28:51,200 Speaker 1: overcome that, right, Like it's expanding but only a little bit, 577 00:28:51,240 --> 00:28:53,560 Speaker 1: so light can still rip through it. So then kind 578 00:28:53,560 --> 00:28:57,000 Speaker 1: of like, at what point does the expansion of the 579 00:28:57,080 --> 00:28:59,520 Speaker 1: universe start to approach the speed of light so that 580 00:28:59,760 --> 00:29:02,680 Speaker 1: like can't rip through it. So it's something like sixty 581 00:29:02,800 --> 00:29:06,160 Speaker 1: billion light years away. If I gave you a head 582 00:29:06,200 --> 00:29:09,440 Speaker 1: start of sixty billion light years then and shine a 583 00:29:09,480 --> 00:29:13,800 Speaker 1: flashlight at you, that light would never catch you sixty 584 00:29:13,880 --> 00:29:16,240 Speaker 1: billion light years. Is there enough universe for me to 585 00:29:16,280 --> 00:29:18,960 Speaker 1: get that much of a head start. We just don't know, right, 586 00:29:19,280 --> 00:29:21,600 Speaker 1: We have no idea what's out beyond the edge of 587 00:29:21,600 --> 00:29:25,440 Speaker 1: the observable universe, And that's actually the threshold of the 588 00:29:25,480 --> 00:29:29,800 Speaker 1: observable universe. Like photons that were created at T equal zero, 589 00:29:29,880 --> 00:29:32,640 Speaker 1: the beginning of the universe sixty two billion light years 590 00:29:32,640 --> 00:29:36,240 Speaker 1: away will never reach us. Those photons, even if they're 591 00:29:36,240 --> 00:29:39,200 Speaker 1: pointed right at us, we'll never get here because the 592 00:29:39,240 --> 00:29:42,480 Speaker 1: expansion of the universe will create new space faster than 593 00:29:42,560 --> 00:29:45,720 Speaker 1: they can move it. So nothing that's beyond that we 594 00:29:45,840 --> 00:29:48,320 Speaker 1: will ever ever see. Right. It's kind of like the 595 00:29:48,400 --> 00:29:51,960 Speaker 1: resverse problem, right, Like there might be somebody sixty billion 596 00:29:52,040 --> 00:29:55,160 Speaker 1: light years away that shines a flashlight at us to 597 00:29:55,280 --> 00:29:57,800 Speaker 1: try to tag us, but that light will never catch 598 00:29:57,840 --> 00:30:01,320 Speaker 1: up to us because the space is expanding too fast, exactly, 599 00:30:01,560 --> 00:30:04,120 Speaker 1: and in the same way a flashlight we send from 600 00:30:04,120 --> 00:30:06,200 Speaker 1: here to there. If you start running there, then that 601 00:30:06,240 --> 00:30:08,360 Speaker 1: photon is never going to catch those people. No matter 602 00:30:08,440 --> 00:30:10,440 Speaker 1: how fast they're going or slow. They could just sit 603 00:30:10,560 --> 00:30:12,520 Speaker 1: on their butts and they will never be hit by 604 00:30:12,520 --> 00:30:16,040 Speaker 1: that photon. Right, And that's what you call the Hubble's law. Right, 605 00:30:16,080 --> 00:30:19,200 Speaker 1: Like the velocity of how space is growing is getting 606 00:30:19,200 --> 00:30:22,160 Speaker 1: bigger with distance, That's right. Hubble's law tells us about 607 00:30:22,200 --> 00:30:25,120 Speaker 1: the recession velocity, how fast something is moving away from us, 608 00:30:25,240 --> 00:30:27,320 Speaker 1: and how that's getting faster and faster as you go 609 00:30:27,440 --> 00:30:30,040 Speaker 1: further and further. So as you get further away from us, 610 00:30:30,040 --> 00:30:32,120 Speaker 1: things are moving away from us faster and faster. At 611 00:30:32,160 --> 00:30:34,960 Speaker 1: some point that speed exceeds the speed of light. And 612 00:30:35,000 --> 00:30:37,920 Speaker 1: that's called the Hubble volume. And the Hubble volume is 613 00:30:37,960 --> 00:30:41,560 Speaker 1: this spear that surrounds us. Right, And because the universe 614 00:30:41,800 --> 00:30:45,560 Speaker 1: is expanding and that expansion is accelerating, then that volume 615 00:30:45,600 --> 00:30:48,680 Speaker 1: is actually shrinking. Right. We can see a smaller and 616 00:30:48,760 --> 00:30:52,520 Speaker 1: smaller fraction of the universe as time goes on. As 617 00:30:52,560 --> 00:30:55,040 Speaker 1: time goes on, you can be closer and closer to us. 618 00:30:55,360 --> 00:30:57,840 Speaker 1: Shoot a flashlight at us, and it will never get 619 00:30:57,880 --> 00:31:02,000 Speaker 1: to us because this expansion is accelerating. Right, Yeah, that 620 00:31:02,080 --> 00:31:04,400 Speaker 1: whole part of the universe, maybe the rest of the 621 00:31:04,520 --> 00:31:08,120 Speaker 1: entire universe is basically dark to us, right, it's invisible, 622 00:31:08,240 --> 00:31:10,640 Speaker 1: like we can never see it. Yeah, and things that 623 00:31:10,680 --> 00:31:13,280 Speaker 1: we used to be able to see are disappearing. Right. 624 00:31:13,440 --> 00:31:15,720 Speaker 1: It might be that if you shine a flashlight at 625 00:31:15,840 --> 00:31:18,440 Speaker 1: us an early part of the universe, it would get here. 626 00:31:18,480 --> 00:31:20,360 Speaker 1: But then later on if you waited too long, if 627 00:31:20,360 --> 00:31:22,480 Speaker 1: you waited ten billion years and then showing your flashlight 628 00:31:22,520 --> 00:31:25,520 Speaker 1: at us, it wouldn't ever get here because the expansion 629 00:31:25,560 --> 00:31:28,320 Speaker 1: has increased and accelerated beyond that threshold. Well, if it 630 00:31:28,360 --> 00:31:31,240 Speaker 1: wants to move away that fast, away from us, you know, 631 00:31:31,320 --> 00:31:33,400 Speaker 1: maybe we don't want to see it. What have they 632 00:31:33,400 --> 00:31:36,000 Speaker 1: got to hide anyway? Yeah, what's wrong with us? What 633 00:31:36,040 --> 00:31:37,800 Speaker 1: do you mean? Why are they running away from us 634 00:31:38,000 --> 00:31:40,160 Speaker 1: that fast? So then what does that mean? What that 635 00:31:40,480 --> 00:31:42,960 Speaker 1: means that the furthest anything we'll ever see is about 636 00:31:42,960 --> 00:31:46,000 Speaker 1: sixty two billion years away, Yes, sixty two billion light 637 00:31:46,040 --> 00:31:49,480 Speaker 1: years away. If the expansion of the universe continues accelerating 638 00:31:49,520 --> 00:31:51,720 Speaker 1: the way that it has, then we will never see 639 00:31:51,760 --> 00:31:55,160 Speaker 1: anything further away. Than sixty two billion light years. There's 640 00:31:55,160 --> 00:31:59,400 Speaker 1: a caveat. There's always a caveat, a fine print, meaning 641 00:31:59,480 --> 00:32:02,000 Speaker 1: like of the space will stop expanding, right, Like, we 642 00:32:02,000 --> 00:32:05,080 Speaker 1: don't know, well, we don't understand why that expansion is 643 00:32:05,080 --> 00:32:07,280 Speaker 1: accelerating and what's doing it. All we see is that 644 00:32:07,320 --> 00:32:09,480 Speaker 1: it's happening. And since we don't understand why, we have 645 00:32:09,520 --> 00:32:12,200 Speaker 1: no idea what the mechanism is, we can't predict its future. 646 00:32:12,240 --> 00:32:14,280 Speaker 1: We don't know what's driving it. We know that it 647 00:32:14,360 --> 00:32:16,760 Speaker 1: turned on a few billion years ago, so we don't 648 00:32:16,840 --> 00:32:18,720 Speaker 1: understand any of that. And so we could stop, and 649 00:32:18,720 --> 00:32:21,040 Speaker 1: it could turn around. It could shrink the universe so 650 00:32:21,120 --> 00:32:23,440 Speaker 1: that the things that we're always invisible to us now 651 00:32:23,520 --> 00:32:26,360 Speaker 1: become visible. The simplest thing to do is to extrapolate 652 00:32:26,360 --> 00:32:28,760 Speaker 1: that nothing's going to change. But you know, we've been 653 00:32:28,800 --> 00:32:31,280 Speaker 1: wrong before, right And like you said, like you have 654 00:32:31,400 --> 00:32:33,840 Speaker 1: been sort of wrong before, Like this expansion of the 655 00:32:33,880 --> 00:32:36,560 Speaker 1: universe wasn't always there, like it seems to have turned 656 00:32:36,560 --> 00:32:39,400 Speaker 1: on at some point. Yeah, exactly. It's not something we 657 00:32:39,680 --> 00:32:42,200 Speaker 1: understand very well. We talked about this on the podcast 658 00:32:42,200 --> 00:32:44,840 Speaker 1: actually once about the history of dark energy. We think 659 00:32:44,880 --> 00:32:47,200 Speaker 1: that maybe the amount of dark energy is constant, but 660 00:32:47,320 --> 00:32:50,479 Speaker 1: dark energy doesn't get deluded as the universe grows, like 661 00:32:50,600 --> 00:32:54,400 Speaker 1: as more spaces created, every unit of space also has 662 00:32:54,480 --> 00:32:57,520 Speaker 1: more dark energy, and so over time it comes to 663 00:32:57,560 --> 00:33:00,200 Speaker 1: sort of dominate what's happening in the universe. And that's 664 00:33:00,200 --> 00:33:02,720 Speaker 1: why we think maybe it sort of took over about 665 00:33:02,760 --> 00:33:05,440 Speaker 1: five billion years ago and became the thing that drove 666 00:33:05,480 --> 00:33:07,680 Speaker 1: the whole universe. All right, So that's one way to 667 00:33:07,720 --> 00:33:10,880 Speaker 1: answer the question can you outrun a flashlight? And the 668 00:33:10,960 --> 00:33:15,040 Speaker 1: answer is yes, you know, because of expanding space. If 669 00:33:15,520 --> 00:33:18,800 Speaker 1: the space between you and the person shooting the flashlight 670 00:33:18,840 --> 00:33:21,440 Speaker 1: at you is big enough and that space is expanding 671 00:33:21,480 --> 00:33:25,040 Speaker 1: fast enough, then you can't outrun light. Amazingly, I guess 672 00:33:25,040 --> 00:33:28,800 Speaker 1: you can avoid it. What if I just moved sideways, 673 00:33:28,880 --> 00:33:32,000 Speaker 1: Daniel would save us all a lot of trouble. Wow 674 00:33:32,240 --> 00:33:35,080 Speaker 1: podcast simplified. So right now, the way to outrun a 675 00:33:35,080 --> 00:33:38,240 Speaker 1: flashlight is just travel sixty two billion light years away 676 00:33:38,280 --> 00:33:40,560 Speaker 1: and then nobody will ever be able to laser tag 677 00:33:40,600 --> 00:33:43,680 Speaker 1: you or invent a dark energy machine that can stretch 678 00:33:43,720 --> 00:33:47,240 Speaker 1: space between you and that photon arbitrarily quickly, and then hey, 679 00:33:47,640 --> 00:33:49,600 Speaker 1: you can just do it yourself. Wow. That would be 680 00:33:49,680 --> 00:33:52,480 Speaker 1: like dark energy tag that would be a totally different product. 681 00:33:52,760 --> 00:33:54,520 Speaker 1: All right, Well, it turns out that that's not the 682 00:33:54,600 --> 00:33:57,680 Speaker 1: only way that you can outrun a flashlight. There is 683 00:33:57,720 --> 00:33:59,960 Speaker 1: another way that you can do it within the rule 684 00:34:00,080 --> 00:34:03,200 Speaker 1: of the universe, and it doesn't require you to go 685 00:34:03,320 --> 00:34:06,160 Speaker 1: out that far. So let's get into it. But first, 686 00:34:06,360 --> 00:34:21,600 Speaker 1: let's take another quick break, right, Daniel, Can you outrun 687 00:34:21,600 --> 00:34:24,160 Speaker 1: a flashlight? And we figured out one way to do 688 00:34:24,200 --> 00:34:26,680 Speaker 1: that that if you go out far enough, the space 689 00:34:26,760 --> 00:34:29,759 Speaker 1: is expanding fast enough that light will never catch up 690 00:34:29,760 --> 00:34:32,400 Speaker 1: to you. But apparently there is another way that you 691 00:34:32,400 --> 00:34:37,080 Speaker 1: can outrun light without having to depend on the you know, 692 00:34:37,239 --> 00:34:40,360 Speaker 1: the diet of space. That's right, And this is a 693 00:34:40,400 --> 00:34:42,719 Speaker 1: real mind bender. This one took me a while to 694 00:34:42,800 --> 00:34:45,880 Speaker 1: figure out. It feels like it really contradicts everything you 695 00:34:45,960 --> 00:34:48,480 Speaker 1: know about special relativity. If you spent a lot of 696 00:34:48,480 --> 00:34:52,040 Speaker 1: time thinking about special relativity and adjusting to the idea 697 00:34:52,120 --> 00:34:55,080 Speaker 1: that light always moves at the speed of light relative 698 00:34:55,120 --> 00:34:57,960 Speaker 1: to everybody else, this one's gonna feel like it breaks 699 00:34:58,000 --> 00:35:01,319 Speaker 1: that rule. But it actually is a natural consequence of 700 00:35:01,360 --> 00:35:04,240 Speaker 1: special relativity, and it breaks that rule because it breaks 701 00:35:04,360 --> 00:35:08,560 Speaker 1: one of the assumptions of special relativity, which is about acceleration. 702 00:35:08,719 --> 00:35:11,040 Speaker 1: So the idea is that you can out run a 703 00:35:11,320 --> 00:35:14,360 Speaker 1: flash of light if you're moving in a rocket ship 704 00:35:14,400 --> 00:35:19,160 Speaker 1: with constant acceleration, if you're always always speeding up, then 705 00:35:19,200 --> 00:35:22,080 Speaker 1: that photon will never catch you. And the way that 706 00:35:22,120 --> 00:35:24,879 Speaker 1: it avoids the rules of special relativity is that one 707 00:35:24,920 --> 00:35:29,040 Speaker 1: word acceleration. Most of the rules of special relativity require 708 00:35:29,080 --> 00:35:34,120 Speaker 1: you to not be accelerating to have constant relative velocity. Interesting, 709 00:35:34,239 --> 00:35:36,239 Speaker 1: I see, so like, if I'm trying to outrun a 710 00:35:36,280 --> 00:35:39,080 Speaker 1: flashlight and I start running, it's not just about never 711 00:35:39,120 --> 00:35:42,960 Speaker 1: stopping or always running or always you know, moving, It's 712 00:35:42,960 --> 00:35:45,799 Speaker 1: about like each second you have to go a little 713 00:35:45,800 --> 00:35:48,320 Speaker 1: bit faster than you were before. That's what acceleration means. 714 00:35:48,440 --> 00:35:50,800 Speaker 1: That's right, when Usain Bolt comes out of the blocks, 715 00:35:50,920 --> 00:35:54,120 Speaker 1: he goes from zero meters per second to ten per 716 00:35:54,160 --> 00:35:58,000 Speaker 1: second pretty quickly. He's accelerating, he's changing his speed, but 717 00:35:58,040 --> 00:36:00,480 Speaker 1: then at some point he stays at ten ms or second, 718 00:36:00,560 --> 00:36:05,200 Speaker 1: right Like, even losing Bold can't accelerate forever on the ground, 719 00:36:05,320 --> 00:36:08,520 Speaker 1: right Like, somehow there's something about his body and air 720 00:36:08,760 --> 00:36:11,719 Speaker 1: resistance and his muscles that just prevent them from going 721 00:36:11,760 --> 00:36:14,120 Speaker 1: faster and faster and faster and faster. That's right. So 722 00:36:14,160 --> 00:36:16,880 Speaker 1: you need constant acceleration to make this work, and you 723 00:36:16,920 --> 00:36:19,440 Speaker 1: don't need to be able to go faster than the 724 00:36:19,520 --> 00:36:21,799 Speaker 1: speed of light. Is not some trick where you're like 725 00:36:22,040 --> 00:36:25,520 Speaker 1: always adding the same amount of speed per second. You 726 00:36:25,560 --> 00:36:29,040 Speaker 1: can be constantly accelerating and asthemptotically approaching the speed of light, 727 00:36:29,200 --> 00:36:32,440 Speaker 1: never even actually reaching the speed of light. But if 728 00:36:32,480 --> 00:36:35,600 Speaker 1: you're getting faster and faster every second, then you can 729 00:36:35,600 --> 00:36:38,879 Speaker 1: avoid that photon ever hitting your back. Right, Because even 730 00:36:39,040 --> 00:36:42,799 Speaker 1: you are always accelerating, always gaining speed, you're still never 731 00:36:42,800 --> 00:36:45,400 Speaker 1: going to go faster than the speed of light. Like somehow, 732 00:36:45,440 --> 00:36:47,880 Speaker 1: the way special relativity works, it's like you're just gonna 733 00:36:47,960 --> 00:36:50,600 Speaker 1: be trying and trying, but you'll never actually go faster 734 00:36:50,640 --> 00:36:52,320 Speaker 1: than the speed of light. You can never reach the 735 00:36:52,320 --> 00:36:54,839 Speaker 1: speed of light because you have mass things with mask 736 00:36:54,880 --> 00:36:57,000 Speaker 1: and never reach the speed of light. What you can 737 00:36:57,000 --> 00:36:59,720 Speaker 1: do is add more energy, right, You can get more energy. 738 00:36:59,800 --> 00:37:03,239 Speaker 1: You're energy can increase the arbitrary infinite amounts, but your 739 00:37:03,320 --> 00:37:07,000 Speaker 1: velocity doesn't track it approaches the speed of light, never 740 00:37:07,120 --> 00:37:09,279 Speaker 1: actually gets there, right, And this is where it gets 741 00:37:09,360 --> 00:37:12,960 Speaker 1: kind of counterintuitive, because you know, I mean, I'm accelerating, 742 00:37:13,120 --> 00:37:15,600 Speaker 1: going faster and faster, but I'll never actually reach the 743 00:37:15,600 --> 00:37:19,919 Speaker 1: speed of light. And so you're saying that even if 744 00:37:19,960 --> 00:37:22,200 Speaker 1: somebody shoots his light at me that is going at 745 00:37:22,200 --> 00:37:24,120 Speaker 1: the speed of light, even though it will always be 746 00:37:24,120 --> 00:37:27,160 Speaker 1: going faster than me, you're saying, there's a possibility that 747 00:37:27,239 --> 00:37:30,440 Speaker 1: it might not catch me. Yeah, it will not catch you. 748 00:37:30,440 --> 00:37:32,680 Speaker 1: You know. The scenario I'm imagining is that you're like, 749 00:37:32,760 --> 00:37:34,600 Speaker 1: you start out ahead of me, maybe I'll give you 750 00:37:34,640 --> 00:37:37,000 Speaker 1: a ten meter head start, and you start accelerating, and 751 00:37:37,000 --> 00:37:38,920 Speaker 1: then I turned on this flash of light. Then you 752 00:37:38,920 --> 00:37:40,720 Speaker 1: know you are going to be going a certain speed, 753 00:37:40,800 --> 00:37:43,640 Speaker 1: going faster and faster and faster, approaching the speed of light. 754 00:37:43,800 --> 00:37:47,279 Speaker 1: I'm shooting this flashlight that's moving at the speed of light, 755 00:37:47,320 --> 00:37:49,800 Speaker 1: and so you might think, well, I'm pretty good special relativity. 756 00:37:49,960 --> 00:37:53,200 Speaker 1: If Jorge looks back and asks how fast is that 757 00:37:53,280 --> 00:37:56,840 Speaker 1: photon traveling relative to me, he should give the answer 758 00:37:56,880 --> 00:37:58,880 Speaker 1: of the speed of light, because, as we said before, 759 00:37:59,120 --> 00:38:01,360 Speaker 1: photons travel at the speed of light no matter who's 760 00:38:01,360 --> 00:38:03,720 Speaker 1: measuring them, right, And so then it feels pretty simple. 761 00:38:03,719 --> 00:38:05,920 Speaker 1: You're like, well, if the photon is moving relative to 762 00:38:05,920 --> 00:38:08,719 Speaker 1: me at the speed of light, it will eventually catch me. 763 00:38:09,239 --> 00:38:12,960 Speaker 1: And that seems pretty solid. But all those calculations you 764 00:38:13,040 --> 00:38:17,040 Speaker 1: just did in your head assume no acceleration. Those calculations 765 00:38:17,040 --> 00:38:21,040 Speaker 1: are only true in inertial frames, where there's no acceleration, 766 00:38:21,040 --> 00:38:24,720 Speaker 1: there's only relative constant velocity. It's a little bit different. 767 00:38:24,719 --> 00:38:27,800 Speaker 1: When you add acceleration. You have to go to general 768 00:38:27,880 --> 00:38:32,360 Speaker 1: relativity because acceleration, it turns out, is equivalent to gravity 769 00:38:32,520 --> 00:38:35,560 Speaker 1: a right. That's one of Einstein's big discoveries is that 770 00:38:35,600 --> 00:38:39,640 Speaker 1: you can't tell the difference, for example, between gravity and acceleration. 771 00:38:39,920 --> 00:38:42,839 Speaker 1: If you're like in an elevator in space, you can't 772 00:38:42,840 --> 00:38:45,799 Speaker 1: tell is that elevator accelerating or am I near some 773 00:38:45,960 --> 00:38:49,239 Speaker 1: planet that's creating gravity. It's the same thing, and so 774 00:38:49,320 --> 00:38:52,400 Speaker 1: you have to account for the effective curvature of space 775 00:38:52,600 --> 00:38:56,040 Speaker 1: that you're creating for yourself when you're accelerating. Right. But 776 00:38:56,120 --> 00:38:58,520 Speaker 1: I guess, maybe let's be clear, like, there are situations 777 00:38:58,520 --> 00:39:01,080 Speaker 1: where it will catch you. Right. If I'm standing next 778 00:39:01,080 --> 00:39:04,000 Speaker 1: to using bold and he starts running and he's accelerating, 779 00:39:04,239 --> 00:39:07,080 Speaker 1: he might be accelerating getting up to his ten per second, 780 00:39:07,120 --> 00:39:09,800 Speaker 1: But if I shine a flashlight on him right away, 781 00:39:09,920 --> 00:39:11,560 Speaker 1: it's going to catch him, right, if you shine a 782 00:39:11,560 --> 00:39:14,880 Speaker 1: flashlight on him soon enough. Absolutely, But if his acceleration 783 00:39:15,040 --> 00:39:17,799 Speaker 1: is high enough, right, and he started out with enough 784 00:39:17,840 --> 00:39:20,359 Speaker 1: of a head start, then it will never catch him. 785 00:39:20,520 --> 00:39:23,960 Speaker 1: If he has constant acceleration. So those are two special things, right, 786 00:39:24,000 --> 00:39:26,440 Speaker 1: Like he needs a head start, yes, and I also 787 00:39:26,440 --> 00:39:28,279 Speaker 1: have to wait a certain amount of time before I 788 00:39:28,320 --> 00:39:30,760 Speaker 1: turn on my flashlight. You can turn on your flashlight 789 00:39:30,760 --> 00:39:32,279 Speaker 1: at the same moment as long as he has a 790 00:39:32,280 --> 00:39:34,239 Speaker 1: physical head start. He either needs a head start in 791 00:39:34,360 --> 00:39:37,120 Speaker 1: time so he can get some distance gap, or he 792 00:39:37,160 --> 00:39:39,360 Speaker 1: needs to start like ten ms away from you. But 793 00:39:39,400 --> 00:39:41,239 Speaker 1: he can start running at the same moment as you 794 00:39:41,280 --> 00:39:44,160 Speaker 1: turn on that flashlight, and the flashlight will never catch 795 00:39:44,239 --> 00:39:47,560 Speaker 1: him if he continues to accelerate forever till the end 796 00:39:47,600 --> 00:39:50,840 Speaker 1: of which is pretty tough. Yeah, I don't know if 797 00:39:50,840 --> 00:39:53,600 Speaker 1: he signed up for that. He might have other things 798 00:39:53,640 --> 00:39:55,440 Speaker 1: he wants to do. I mean, somebody give that guy 799 00:39:55,480 --> 00:39:57,319 Speaker 1: a power bar or something. I mean in a number 800 00:39:57,360 --> 00:39:59,200 Speaker 1: of power bars, right, Because you can look at it 801 00:39:59,280 --> 00:40:01,400 Speaker 1: the other way and say, well, the photon will catch 802 00:40:01,400 --> 00:40:05,440 Speaker 1: you at time equals infinity because your speed is approaching 803 00:40:05,440 --> 00:40:07,480 Speaker 1: the speed of life but never catching it. So at 804 00:40:07,520 --> 00:40:09,600 Speaker 1: time equals infinity, the photon will get to you. But 805 00:40:09,880 --> 00:40:13,640 Speaker 1: time equals infinity isn't a real time, right, the universe 806 00:40:13,680 --> 00:40:16,280 Speaker 1: could go on forever, will never get there. I see. 807 00:40:16,280 --> 00:40:18,400 Speaker 1: But there are two ingredients of this, right, Like you 808 00:40:18,440 --> 00:40:21,040 Speaker 1: need a head start, and you need to be always 809 00:40:21,040 --> 00:40:24,520 Speaker 1: accelerating at a certain rate, right, And I imagine that 810 00:40:24,560 --> 00:40:27,320 Speaker 1: if I'm only accelerating a little bit at a time, 811 00:40:27,440 --> 00:40:29,799 Speaker 1: that I need a really big head start. But if 812 00:40:29,880 --> 00:40:32,719 Speaker 1: I accelerate really fast, if I have like a constant 813 00:40:32,800 --> 00:40:35,360 Speaker 1: rocket pushing me, then I don't need that big of 814 00:40:35,400 --> 00:40:37,520 Speaker 1: a head start exactly. And you can calculate it by 815 00:40:37,560 --> 00:40:39,120 Speaker 1: looking at it from the other point of view, like 816 00:40:39,160 --> 00:40:41,360 Speaker 1: from us sain Bolt point of view, What is this 817 00:40:41,520 --> 00:40:43,600 Speaker 1: Like if you're riding on his shoulder, for example, and 818 00:40:43,600 --> 00:40:46,600 Speaker 1: you're looking back as he's accelerating, then you might think, well, 819 00:40:46,600 --> 00:40:49,000 Speaker 1: then what this means is that there's a distance beyond 820 00:40:49,200 --> 00:40:52,239 Speaker 1: which you cannot see, Like somebody who shines a flashlight 821 00:40:52,280 --> 00:40:54,080 Speaker 1: at you from there tries to send you a message 822 00:40:54,239 --> 00:40:57,719 Speaker 1: that information will never reach you. So there's like this horizon, 823 00:40:57,800 --> 00:41:01,160 Speaker 1: this wall beyond which it's just lack and the distance 824 00:41:01,200 --> 00:41:04,440 Speaker 1: to that wall depends on his acceleration. So if he's 825 00:41:04,440 --> 00:41:07,520 Speaker 1: accelerating really really fast, then that horizon is closer. If 826 00:41:07,520 --> 00:41:10,239 Speaker 1: he's accelerating really really slowly, the horizon needs to be 827 00:41:10,320 --> 00:41:13,120 Speaker 1: further further away, So as the acceleration goes to zero, 828 00:41:13,360 --> 00:41:16,080 Speaker 1: that horizon is infinitely far away. But the distance to 829 00:41:16,120 --> 00:41:18,920 Speaker 1: that horizon is the speed of light squared divided by 830 00:41:18,960 --> 00:41:22,480 Speaker 1: your acceleration. But I guess it still feels counterintuitive, right 831 00:41:22,520 --> 00:41:24,640 Speaker 1: because the light is going at the speed of light, 832 00:41:24,840 --> 00:41:27,279 Speaker 1: but Hussein Bulb will never reach the speed of light. 833 00:41:27,719 --> 00:41:30,279 Speaker 1: So how is it the light will never reach him? Right, Like, 834 00:41:30,760 --> 00:41:33,640 Speaker 1: wouldn't it eventually make up ground? Yeah, you would think so, 835 00:41:33,840 --> 00:41:36,000 Speaker 1: and that would be true if there was no acceleration. 836 00:41:36,000 --> 00:41:38,880 Speaker 1: But remember, acceleration means all these rules get bent a 837 00:41:38,960 --> 00:41:41,440 Speaker 1: little bit, the same way like space gets bent. And 838 00:41:41,440 --> 00:41:43,520 Speaker 1: so the way that sort of incorporated into your brain 839 00:41:43,600 --> 00:41:46,879 Speaker 1: is to think about how acceleration is like an effective 840 00:41:46,920 --> 00:41:49,960 Speaker 1: bending of space, and when space gets bent, all of 841 00:41:49,960 --> 00:41:52,920 Speaker 1: your intuition about who catches what go out the window. 842 00:41:53,320 --> 00:41:56,160 Speaker 1: You know, for example, like if somebody's inside a black 843 00:41:56,200 --> 00:41:58,880 Speaker 1: hole and they shine a flashlight at you, that photon 844 00:41:59,080 --> 00:42:01,080 Speaker 1: is never getting to you. It doesn't matter how much 845 00:42:01,120 --> 00:42:04,160 Speaker 1: time it takes. Why because space is bent, right, and 846 00:42:04,200 --> 00:42:07,520 Speaker 1: those photons follow that bent space. So if you are 847 00:42:07,680 --> 00:42:11,040 Speaker 1: doing constant acceleration, then it's sort of equivalent to gravity. 848 00:42:11,080 --> 00:42:13,880 Speaker 1: It's sort of like bending space. And so that's what 849 00:42:14,000 --> 00:42:16,840 Speaker 1: creates this horizon. It's not an event horizon. It's not 850 00:42:16,880 --> 00:42:19,680 Speaker 1: like a real physical horizon, but for you, it creates 851 00:42:19,680 --> 00:42:24,239 Speaker 1: like an information horizon. Accelerating objects have an information horizon, 852 00:42:24,280 --> 00:42:27,680 Speaker 1: which is pretty weird interesting, sort of like a content acceleration. 853 00:42:27,800 --> 00:42:30,799 Speaker 1: It's almost like the space between us is expanding, that's 854 00:42:30,800 --> 00:42:33,120 Speaker 1: what you're saying. It's like somehow if I accelerate fast 855 00:42:33,239 --> 00:42:37,080 Speaker 1: enough and I'm further enough away, then that expansion of space, 856 00:42:37,160 --> 00:42:39,600 Speaker 1: which is really just my acceleration, is going to prevent 857 00:42:39,640 --> 00:42:42,480 Speaker 1: the light from reaching me. Yeah, exactly. But it's not 858 00:42:42,520 --> 00:42:45,000 Speaker 1: like a real physical horizon, right, It's only it's from 859 00:42:45,040 --> 00:42:48,040 Speaker 1: your point of view. And again, different people have different 860 00:42:48,040 --> 00:42:50,600 Speaker 1: points of view, and those things can conflict. If I'm 861 00:42:50,640 --> 00:42:54,359 Speaker 1: watching this whole series of events from a spaceship floating nearby, 862 00:42:54,480 --> 00:42:57,480 Speaker 1: I might see the photon catching Usain bolt, right, and 863 00:42:57,520 --> 00:43:00,319 Speaker 1: so I can see a different series of events. It's 864 00:43:00,360 --> 00:43:03,440 Speaker 1: just like with a black hole, right, if I'm watching 865 00:43:03,480 --> 00:43:06,560 Speaker 1: you fall into a black hole from the outside, I 866 00:43:06,719 --> 00:43:08,719 Speaker 1: never see you following a black hole. You never get in. 867 00:43:08,880 --> 00:43:12,320 Speaker 1: You smeared across the event horizon forever. Oh wait a minute, 868 00:43:12,480 --> 00:43:14,799 Speaker 1: for you, you fall right through that event horizon. You're 869 00:43:14,840 --> 00:43:18,120 Speaker 1: inside the black hole. In the same way. These different 870 00:43:18,120 --> 00:43:21,240 Speaker 1: accounts can conflict. Uh Now I feel a little cheated, Daniel. 871 00:43:21,360 --> 00:43:23,480 Speaker 1: I think what you're saying is that if I try 872 00:43:23,560 --> 00:43:27,399 Speaker 1: to Lusain Bold, who's always accelerating, Hussein Bold will think 873 00:43:27,440 --> 00:43:30,960 Speaker 1: that he ut ran the flash of light, but we 874 00:43:31,080 --> 00:43:33,360 Speaker 1: are going to see him lose. The person sending the 875 00:43:33,440 --> 00:43:35,960 Speaker 1: light won't see it hit him, because he's accelerating relative 876 00:43:36,000 --> 00:43:38,720 Speaker 1: to them, he won't see it hitting them. But another 877 00:43:38,760 --> 00:43:41,680 Speaker 1: observer moving in a different direction it's possible for them 878 00:43:41,719 --> 00:43:44,560 Speaker 1: to see the light hitting him. The story depends on 879 00:43:44,680 --> 00:43:48,239 Speaker 1: exactly the location and velocity of everybody involved. It gets 880 00:43:48,239 --> 00:43:50,880 Speaker 1: pretty hairy with general relativity. Man, right, I guess that 881 00:43:51,000 --> 00:43:53,680 Speaker 1: you're saying that to us Saint's Bold kind of frame 882 00:43:53,719 --> 00:43:56,919 Speaker 1: of reference, his experience of things, that light will reach 883 00:43:56,960 --> 00:44:00,239 Speaker 1: him but only in an infinity, like when time ends 884 00:44:00,280 --> 00:44:03,200 Speaker 1: for him. But for someone who's moving in another frame 885 00:44:03,320 --> 00:44:05,239 Speaker 1: or speed, there is a time at which the light 886 00:44:05,280 --> 00:44:09,000 Speaker 1: will hit him. Yes, exactly. There's almost always another velocity 887 00:44:09,120 --> 00:44:11,040 Speaker 1: or location you can get to to tell a different 888 00:44:11,080 --> 00:44:14,120 Speaker 1: story about the same series of events. That's the lesson 889 00:44:14,120 --> 00:44:16,760 Speaker 1: of the universe is that there is no universal history. 890 00:44:16,800 --> 00:44:20,160 Speaker 1: There's no true single account of what happens in this universe. 891 00:44:20,280 --> 00:44:22,799 Speaker 1: Well there is. I mean, the light does catch up 892 00:44:22,800 --> 00:44:24,880 Speaker 1: to him, it's just that for him it happens at infinity, 893 00:44:24,920 --> 00:44:27,960 Speaker 1: and for us it happens non infinity. Yeah, if happening 894 00:44:28,000 --> 00:44:30,399 Speaker 1: in infinity accounts is happening, then you know, I'll pay 895 00:44:30,440 --> 00:44:35,040 Speaker 1: you that twenty infinity. Yeah, let's keep talking here until 896 00:44:35,080 --> 00:44:37,760 Speaker 1: infinity and see if that's the same thing for everyone. 897 00:44:38,080 --> 00:44:39,480 Speaker 1: But that's kind of what you mean, is like, it 898 00:44:39,560 --> 00:44:42,799 Speaker 1: does happen, but at infinity. But that's only from his 899 00:44:42,840 --> 00:44:45,840 Speaker 1: point of view. That's right, because relativity is weird in 900 00:44:45,880 --> 00:44:48,279 Speaker 1: that way. It's pretty weird stuff, all right. Well, then 901 00:44:48,360 --> 00:44:51,080 Speaker 1: that's the answer to the question is can you running flashlight? 902 00:44:51,080 --> 00:44:53,400 Speaker 1: The answer is yes if you got far enough and 903 00:44:53,560 --> 00:44:56,840 Speaker 1: space is expanding fast enough. And also yes if you 904 00:44:56,920 --> 00:44:59,879 Speaker 1: are bold, I guess and you you can't wait till 905 00:44:59,880 --> 00:45:04,399 Speaker 1: an infinity or you only consider it infinity as never, 906 00:45:04,680 --> 00:45:06,480 Speaker 1: or if you have an infinite number of power bars 907 00:45:06,520 --> 00:45:10,240 Speaker 1: and you can accelerate forever into the future. Right to you, 908 00:45:10,239 --> 00:45:12,880 Speaker 1: you will always win. But maybe to somebody else the 909 00:45:12,920 --> 00:45:14,920 Speaker 1: answer will be different. But you'll never have to talk 910 00:45:14,960 --> 00:45:18,239 Speaker 1: to them because you're accelerating away from them forever. That's 911 00:45:18,320 --> 00:45:21,560 Speaker 1: the true benefit here is never haven't you talked to 912 00:45:21,760 --> 00:45:24,840 Speaker 1: or see anyone? Ever? Again? All right, that's a pretty 913 00:45:24,880 --> 00:45:27,120 Speaker 1: mind bending question, and again just a reminder of how 914 00:45:27,160 --> 00:45:29,520 Speaker 1: weird this universe is and how weird the rules of 915 00:45:29,560 --> 00:45:31,320 Speaker 1: it are. Right, it's not just that there are weird 916 00:45:31,360 --> 00:45:33,279 Speaker 1: things in it. It's just that it is a weird 917 00:45:33,360 --> 00:45:36,279 Speaker 1: universe in itself. It certainly is. But we love it. 918 00:45:36,480 --> 00:45:39,680 Speaker 1: We love the weirdness. Stay weird universe. All right, Well, 919 00:45:39,719 --> 00:45:42,480 Speaker 1: we hope you enjoyed that. Thanks for joining us, See 920 00:45:42,520 --> 00:45:52,840 Speaker 1: you next time. Thanks for listening, and remember that Daniel 921 00:45:52,880 --> 00:45:55,400 Speaker 1: and Jorge explain the Universe is a production of I 922 00:45:55,640 --> 00:45:59,040 Speaker 1: Heart Radio or more podcast from my Heart Radio. Visit 923 00:45:59,080 --> 00:46:02,560 Speaker 1: the I Heart Radio, Apple Apple Podcasts, or wherever you 924 00:46:02,680 --> 00:46:06,120 Speaker 1: listen to your favorite shows. H