1 00:00:05,760 --> 00:00:07,680 Speaker 1: Hey, you, welcome to Stuff to Blow your Mind. My 2 00:00:07,760 --> 00:00:11,200 Speaker 1: name is Robert Lamb and I'm Joe McCormick. And, uh, 3 00:00:11,240 --> 00:00:13,000 Speaker 1: this week, Rob and I are out on breaks, so 4 00:00:13,039 --> 00:00:16,080 Speaker 1: we've got some great Vault episodes for you. This one 5 00:00:16,160 --> 00:00:20,840 Speaker 1: originally aired December ninth, and it's our interview with Daniel 6 00:00:20,880 --> 00:00:25,079 Speaker 1: Whitson from the podcast Daniel and Jorge Explain the Universe. 7 00:00:25,320 --> 00:00:27,560 Speaker 1: I think we talk all kinds of time travel and 8 00:00:27,600 --> 00:00:33,040 Speaker 1: stuff like that. Welcome to Stuff to Blow your Mind, 9 00:00:33,320 --> 00:00:42,520 Speaker 1: production of My Heart Radio. Hey, you, welcome to Stuff 10 00:00:42,560 --> 00:00:45,280 Speaker 1: to Blow your Mind. My name is Robert Lamb and 11 00:00:45,320 --> 00:00:48,600 Speaker 1: I'm Joe McCormick. And for today's episode, we're going to 12 00:00:48,640 --> 00:00:52,800 Speaker 1: be chatting with Daniel Whitson, who is a particle physicist 13 00:00:52,880 --> 00:00:56,120 Speaker 1: and science communicator and one of the hosts of the 14 00:00:56,160 --> 00:01:00,480 Speaker 1: podcast Daniel and Jorge Explain the Universe. This is Enniel's 15 00:01:00,600 --> 00:01:03,360 Speaker 1: third time hopping on the show with us. The previous 16 00:01:03,440 --> 00:01:07,640 Speaker 1: episodes were in September of twenty nineteen and April of 17 00:01:08,880 --> 00:01:11,200 Speaker 1: And for this episode, we're gonna be talking about a book. 18 00:01:11,520 --> 00:01:14,600 Speaker 1: Daniel and his co host and co author Jorge him 19 00:01:14,840 --> 00:01:18,720 Speaker 1: have a new book called Frequently Asked Questions About the universe. 20 00:01:19,400 --> 00:01:21,280 Speaker 1: So it was a real pleasure to have Daniel on 21 00:01:21,319 --> 00:01:23,720 Speaker 1: the show for the hat trick, and I guess without 22 00:01:23,760 --> 00:01:29,560 Speaker 1: any further delay, we will go right into the interview. Daniel, 23 00:01:29,640 --> 00:01:31,440 Speaker 1: welcome back to the show. We're so glad you're here. 24 00:01:31,760 --> 00:01:33,720 Speaker 1: Thanks very much for having me back. I always fun 25 00:01:33,720 --> 00:01:37,320 Speaker 1: to talk to you guys about things that blew my mind. Awesome. So, 26 00:01:37,480 --> 00:01:41,240 Speaker 1: um the podcast Daniel and Jorge explain the Universe still 27 00:01:41,280 --> 00:01:45,119 Speaker 1: going strong? Um, how how far are you into explaining 28 00:01:45,280 --> 00:01:49,160 Speaker 1: the universe in its entirely. We have explained zero point 29 00:01:49,320 --> 00:01:52,600 Speaker 1: zero zero zero zero zer zero zero zero one percent 30 00:01:52,720 --> 00:01:55,920 Speaker 1: of the universe so far. Nice. I uh, actually I 31 00:01:55,960 --> 00:01:58,000 Speaker 1: was looking at your recent episodes and I saw did 32 00:01:58,040 --> 00:02:00,240 Speaker 1: you recently do one that was an interview with Shawn 33 00:02:00,320 --> 00:02:04,400 Speaker 1: Carroll about the uh, the many world's interpretation of quantum mechanics. 34 00:02:04,440 --> 00:02:07,440 Speaker 1: I know, I know he favors that, right. Yeah. We 35 00:02:07,480 --> 00:02:10,160 Speaker 1: actually have a series where I interview an expert on 36 00:02:10,280 --> 00:02:13,680 Speaker 1: each of the interpretations of quantum mechanics. We did one 37 00:02:13,680 --> 00:02:17,120 Speaker 1: on Copenhagen interpretation with Anna Becker, we did one on 38 00:02:17,600 --> 00:02:21,800 Speaker 1: the relational interpretation of quantum mechanics with Carlo Rovelli, and 39 00:02:21,840 --> 00:02:24,840 Speaker 1: then we talked to Sean about many world's interpretation, and 40 00:02:24,960 --> 00:02:26,799 Speaker 1: just a couple of weeks ago we did one about 41 00:02:26,800 --> 00:02:30,920 Speaker 1: the pilot wave theory of quantum mechanics, which totally blew 42 00:02:31,000 --> 00:02:36,280 Speaker 1: my mind. Really much overlooked and unnecessarily maligned interpretation of 43 00:02:36,360 --> 00:02:40,359 Speaker 1: quantum mechanics, in my opinion, malign, like people are being 44 00:02:40,400 --> 00:02:44,280 Speaker 1: mean to it. Well, there's this famous proof by John 45 00:02:44,360 --> 00:02:48,320 Speaker 1: von Neumann like seventy years ago demonstrating that it was 46 00:02:48,400 --> 00:02:51,680 Speaker 1: essentially impossible, and because von Neuman is such a giant 47 00:02:51,720 --> 00:02:54,679 Speaker 1: of the field, everybody thought, well, that's that. Turns out 48 00:02:54,720 --> 00:02:58,800 Speaker 1: he was wrong, though, and it took people years to 49 00:02:58,840 --> 00:03:00,919 Speaker 1: figure it out. It was Belle actually who figured out 50 00:03:00,919 --> 00:03:03,960 Speaker 1: that Nouman was wrong, and that it's possible to have 51 00:03:04,240 --> 00:03:08,960 Speaker 1: a theory of quantum mechanics with hidden variables that's deterministic, 52 00:03:09,000 --> 00:03:12,840 Speaker 1: that's not random at all um. But still to this day, 53 00:03:12,919 --> 00:03:17,239 Speaker 1: nobody really takes pilot wave theory seriously, to Bell's great restoration, 54 00:03:17,320 --> 00:03:20,560 Speaker 1: and I think it's because Neuman sort of through shade 55 00:03:20,600 --> 00:03:23,239 Speaker 1: on it decades ago and it never really recovered. I 56 00:03:23,280 --> 00:03:26,079 Speaker 1: guess that's always dangerous when there's like a famously smart 57 00:03:26,120 --> 00:03:28,840 Speaker 1: person who has an opinion, absolutely, And I find that 58 00:03:28,919 --> 00:03:33,000 Speaker 1: physics Nobel Prize winners are especially guilty of this imagining 59 00:03:33,120 --> 00:03:36,000 Speaker 1: that they are experts in every corner of everything and 60 00:03:36,040 --> 00:03:40,760 Speaker 1: opining on economics or you know, social politics or whatever. 61 00:03:41,160 --> 00:03:43,040 Speaker 1: If you have Nobel Prize winner in front of your name, 62 00:03:43,080 --> 00:03:46,160 Speaker 1: you're an expert. Uh So, today we wanted to talk 63 00:03:46,200 --> 00:03:49,119 Speaker 1: about a couple of chapters that are in a book 64 00:03:49,120 --> 00:03:51,480 Speaker 1: of yours. Did that come out earlier this year? Tell 65 00:03:51,520 --> 00:03:53,640 Speaker 1: us a bit about the book. Yeah. So the book 66 00:03:53,720 --> 00:03:56,720 Speaker 1: is called Frequently Asked Questions about the Universe that I 67 00:03:56,760 --> 00:03:59,200 Speaker 1: wrote together with my co host on the podcast and 68 00:03:59,240 --> 00:04:03,040 Speaker 1: longtime collibrator Orge h. Cham who's also famous for being 69 00:04:03,080 --> 00:04:07,600 Speaker 1: the genius behind PhD Comics. And the book comes from 70 00:04:07,640 --> 00:04:11,880 Speaker 1: noticing that people who write into our podcast often ask 71 00:04:12,000 --> 00:04:14,520 Speaker 1: similar types of questions. There are a few things that 72 00:04:14,600 --> 00:04:18,400 Speaker 1: seems like everybody just wants to know about or understand, 73 00:04:18,880 --> 00:04:21,200 Speaker 1: or the things that people grapple with. You know, I'm 74 00:04:21,200 --> 00:04:24,520 Speaker 1: a professional particle physicist in my day job, um, and 75 00:04:24,560 --> 00:04:27,040 Speaker 1: so I like asking questions about, you know, the deep 76 00:04:27,160 --> 00:04:30,120 Speaker 1: nature of the universe and how our space and time 77 00:04:30,160 --> 00:04:33,040 Speaker 1: really related. But you don't have to be a professor 78 00:04:33,120 --> 00:04:36,680 Speaker 1: of physics to find these things interesting. And we feel like, 79 00:04:36,960 --> 00:04:41,680 Speaker 1: in a sense, you know, curiosity is democratic. Everybody wonders 80 00:04:41,720 --> 00:04:44,640 Speaker 1: about these things, so we wanted to try to attack 81 00:04:44,720 --> 00:04:47,679 Speaker 1: some of these really big questions that everybody wonders about 82 00:04:48,200 --> 00:04:50,720 Speaker 1: in an approachable way, in the way that doesn't require 83 00:04:50,720 --> 00:04:55,200 Speaker 1: you to really have any knowledge of modern physics at all. Yeah. 84 00:04:55,040 --> 00:04:57,720 Speaker 1: I've really been enjoying the chapter as I was reading. 85 00:04:57,960 --> 00:05:00,800 Speaker 1: One thing I like that you do in this book, um, 86 00:05:01,200 --> 00:05:04,120 Speaker 1: is that you know, it's not like a continuous narrative 87 00:05:04,240 --> 00:05:06,640 Speaker 1: that has to you have to have read everything that 88 00:05:06,720 --> 00:05:09,520 Speaker 1: came before in order to understand. Like, the chapters can 89 00:05:09,520 --> 00:05:12,799 Speaker 1: be consumed pretty much on their own, right. Yeah, we figured, 90 00:05:12,839 --> 00:05:16,159 Speaker 1: you know, each chapter should be like one long bathroom break. 91 00:05:16,240 --> 00:05:18,120 Speaker 1: So I mean, I'm not telling you where to read it, 92 00:05:18,160 --> 00:05:21,400 Speaker 1: but looking you're reading while you're busy sitting down doing 93 00:05:21,440 --> 00:05:24,919 Speaker 1: something else. Each chapter, you know, should entertain you while 94 00:05:24,960 --> 00:05:27,359 Speaker 1: you're doing your business, just you know, don't get so 95 00:05:27,400 --> 00:05:30,800 Speaker 1: distracted that you forget to flush right now. Obviously this 96 00:05:31,200 --> 00:05:34,640 Speaker 1: edition would lack the wonderful illustrations that are in the 97 00:05:34,960 --> 00:05:37,680 Speaker 1: print and the Kindle version, but um, but you guys 98 00:05:37,800 --> 00:05:40,760 Speaker 1: put together an audio version as well. Right, yes we did. 99 00:05:40,800 --> 00:05:43,040 Speaker 1: We got to record the audio version of the book, 100 00:05:43,080 --> 00:05:45,880 Speaker 1: which is out now also, and the chapters are read 101 00:05:45,920 --> 00:05:49,040 Speaker 1: by me and by Jorge alternating, which is a lot 102 00:05:49,040 --> 00:05:52,159 Speaker 1: of fun just sort of hear your words come to life. 103 00:05:52,680 --> 00:05:55,080 Speaker 1: But yes, the audio book does miss some other the 104 00:05:55,120 --> 00:05:58,599 Speaker 1: real genius of Jorge's drawings, Um. Jorge and I started 105 00:05:58,600 --> 00:06:01,080 Speaker 1: working together on science communication and more than ten years 106 00:06:01,080 --> 00:06:03,159 Speaker 1: ago when I reached out to him because I thought 107 00:06:03,480 --> 00:06:08,120 Speaker 1: that cartoons would be a really great medium for communicating science, 108 00:06:08,480 --> 00:06:11,600 Speaker 1: because they don't take themselves seriously, you know, They're a cartoon. 109 00:06:11,720 --> 00:06:14,960 Speaker 1: Is different from like a figure into science paper, you know, 110 00:06:15,000 --> 00:06:17,680 Speaker 1: which is very official and formal. A cartoon like makes 111 00:06:17,680 --> 00:06:20,000 Speaker 1: fun of itself and is easy to you know, hang 112 00:06:20,040 --> 00:06:23,080 Speaker 1: out with and accessible. And Jorge was great at that 113 00:06:23,160 --> 00:06:25,760 Speaker 1: kind of stuff. So he and I started working together 114 00:06:26,000 --> 00:06:30,119 Speaker 1: on explaining science using cartoons a long time ago. Um, 115 00:06:30,200 --> 00:06:33,000 Speaker 1: And one thing I really value about his cartoons is 116 00:06:33,440 --> 00:06:36,640 Speaker 1: not just that they are good visual explainers. He has 117 00:06:36,680 --> 00:06:40,600 Speaker 1: a real visual skill for explaining something simply on the page, 118 00:06:40,839 --> 00:06:42,840 Speaker 1: but also that there's sort of a second voice there 119 00:06:42,920 --> 00:06:44,880 Speaker 1: you can hear, like in the text, is the voice 120 00:06:44,880 --> 00:06:47,360 Speaker 1: of me as a physicist, and then in the cartoons 121 00:06:47,400 --> 00:06:49,440 Speaker 1: you can hear sort of his response to some of 122 00:06:49,440 --> 00:06:52,360 Speaker 1: the crazy ideas um and that sort of mirrors the 123 00:06:52,400 --> 00:06:55,240 Speaker 1: way the podcast works. On the podcast, I'm talking about 124 00:06:55,240 --> 00:06:57,600 Speaker 1: physics and Jorges you know something like that doesn't make 125 00:06:57,640 --> 00:06:59,720 Speaker 1: any sense, or how could that possibly be? Or what 126 00:07:00,120 --> 00:07:02,400 Speaker 1: you got to explain that again, So it sort of 127 00:07:02,400 --> 00:07:05,320 Speaker 1: tries to capture those two voices. Yeah, I really liked 128 00:07:05,360 --> 00:07:08,080 Speaker 1: that the illustrations almost seem kind of riffing on the 129 00:07:08,080 --> 00:07:11,880 Speaker 1: written contents of the book. Well, so the parts of 130 00:07:11,880 --> 00:07:13,600 Speaker 1: the book that we wanted to focus on today, I 131 00:07:13,600 --> 00:07:17,760 Speaker 1: think we're mostly centered around the idea of time and 132 00:07:17,800 --> 00:07:20,320 Speaker 1: so maybe maybe a good place to start is you 133 00:07:20,360 --> 00:07:22,040 Speaker 1: have a chapter in the book where you talk about 134 00:07:22,120 --> 00:07:26,600 Speaker 1: time travel and you make some arguments about which types 135 00:07:26,640 --> 00:07:30,000 Speaker 1: of time travel are plausible from a physics perspective and 136 00:07:30,040 --> 00:07:32,400 Speaker 1: which are not. So maybe that would be a good 137 00:07:32,400 --> 00:07:34,240 Speaker 1: place to start. Give us the way of the land, 138 00:07:34,280 --> 00:07:37,120 Speaker 1: like what types of time travel are the least consistent 139 00:07:37,200 --> 00:07:39,720 Speaker 1: with the known laws of physics and which are the 140 00:07:39,720 --> 00:07:44,560 Speaker 1: most consistent. Yeah. Sure, so for those of your listeners 141 00:07:44,600 --> 00:07:47,760 Speaker 1: who are busy building their time travel devices, of the 142 00:07:48,280 --> 00:07:51,520 Speaker 1: usable advice well, you know, the kind of time travel 143 00:07:51,640 --> 00:07:54,640 Speaker 1: that's most inconsistent with the law of physics is the 144 00:07:54,720 --> 00:07:56,960 Speaker 1: kind that most people want to do, you know. It 145 00:07:57,240 --> 00:08:00,000 Speaker 1: is I want to go back in time and change 146 00:08:00,000 --> 00:08:03,040 Speaker 1: age something. I want to not spill my coffee on 147 00:08:03,080 --> 00:08:05,720 Speaker 1: my lap, or I wanted to go, you know, not 148 00:08:06,480 --> 00:08:08,120 Speaker 1: make a mistake, or I want to go ask that 149 00:08:08,160 --> 00:08:10,560 Speaker 1: person out in high school, which I was too timid 150 00:08:10,640 --> 00:08:12,960 Speaker 1: to do, and now I realized I should have that 151 00:08:13,040 --> 00:08:15,360 Speaker 1: kind of thing. It's not just that it's ruled out 152 00:08:15,400 --> 00:08:17,880 Speaker 1: by the laws of physics. In my view, it's not 153 00:08:18,120 --> 00:08:23,200 Speaker 1: even sort of internally self consistent. What it means um, 154 00:08:23,240 --> 00:08:25,040 Speaker 1: you know, and and a lot of people think about 155 00:08:25,040 --> 00:08:28,400 Speaker 1: time travel is like I want to go back in time, 156 00:08:28,560 --> 00:08:31,280 Speaker 1: as if time was a place, like if it's a 157 00:08:31,520 --> 00:08:35,040 Speaker 1: somewhere you can go. It's just sort of like along 158 00:08:35,080 --> 00:08:38,199 Speaker 1: a different direction or something. And it's tempting to think 159 00:08:38,200 --> 00:08:40,600 Speaker 1: about it that way because we we hear a lot 160 00:08:40,640 --> 00:08:43,760 Speaker 1: about modern physics telling us that space and time are 161 00:08:43,800 --> 00:08:47,200 Speaker 1: related and time is like a fourth dimension of space, 162 00:08:47,200 --> 00:08:49,920 Speaker 1: and so it makes you want to think about time 163 00:08:49,960 --> 00:08:52,559 Speaker 1: as a direction in which you can move and maybe 164 00:08:52,559 --> 00:08:55,600 Speaker 1: you could just rewind it somehow, right, But the problem 165 00:08:55,679 --> 00:08:58,280 Speaker 1: is that time. You know, first of all, we don't 166 00:08:58,360 --> 00:09:00,680 Speaker 1: understand time like at all. You can dig into that 167 00:09:00,720 --> 00:09:03,000 Speaker 1: in a minute if you like. Um, but the problem 168 00:09:03,080 --> 00:09:06,080 Speaker 1: is that time sort of reflects how the universe changes, 169 00:09:06,720 --> 00:09:09,040 Speaker 1: and so you know, I think about time is like 170 00:09:09,320 --> 00:09:13,400 Speaker 1: you have a timeline. That timeline is the universe changing, 171 00:09:13,840 --> 00:09:15,880 Speaker 1: Like you have the universe at one moment, and you 172 00:09:15,880 --> 00:09:19,439 Speaker 1: have the universe at another moment. The next moment comes 173 00:09:19,520 --> 00:09:23,640 Speaker 1: later in time, and things can't change without time. Time 174 00:09:23,800 --> 00:09:28,160 Speaker 1: is that change. So the self consistency problem is that 175 00:09:28,360 --> 00:09:32,959 Speaker 1: going back in time to change it changes the timeline itself. 176 00:09:33,160 --> 00:09:36,960 Speaker 1: So like, how does the timeline change? If the timeline 177 00:09:37,280 --> 00:09:40,000 Speaker 1: is the change, how does the timeline itself change? It 178 00:09:40,000 --> 00:09:43,840 Speaker 1: would need like its own time, Like the timeline is 179 00:09:43,840 --> 00:09:46,960 Speaker 1: now moving through time because it was a time before 180 00:09:46,960 --> 00:09:49,760 Speaker 1: you changed in a time after you changed it, So 181 00:09:49,800 --> 00:09:52,559 Speaker 1: it needs like a second dimension of time. I mean, 182 00:09:52,600 --> 00:09:55,320 Speaker 1: it just sort of all becomes very complicated and falls 183 00:09:55,360 --> 00:09:57,720 Speaker 1: apart as soon as you start thinking about it carefully. 184 00:09:58,080 --> 00:10:01,360 Speaker 1: So going back and changing something in the past really 185 00:10:01,400 --> 00:10:04,360 Speaker 1: just makes no sense from a physics point of view. Yeah, 186 00:10:04,679 --> 00:10:08,520 Speaker 1: I love this because I have long kind of been 187 00:10:08,559 --> 00:10:11,160 Speaker 1: skeptical about the idea of time travel into the past. 188 00:10:11,240 --> 00:10:13,920 Speaker 1: And one of the reasons I had doubts about this 189 00:10:14,360 --> 00:10:17,160 Speaker 1: is that wouldn't we expect to have already encountered lots 190 00:10:17,160 --> 00:10:20,360 Speaker 1: of time travelers at some point in history, And there's 191 00:10:20,520 --> 00:10:23,160 Speaker 1: no unambiguous evidence of that. I mean, obviously some people, 192 00:10:23,240 --> 00:10:26,520 Speaker 1: you know, they're weird little things people think or time travel, 193 00:10:26,559 --> 00:10:29,360 Speaker 1: but nothing that looks really clear. So it kind of 194 00:10:29,400 --> 00:10:32,560 Speaker 1: makes me think that if if time travel into the 195 00:10:32,600 --> 00:10:36,040 Speaker 1: past ever happens in the future, it will be of 196 00:10:36,080 --> 00:10:39,280 Speaker 1: a very limited nature. Yeah, I love that as an 197 00:10:39,280 --> 00:10:43,440 Speaker 1: experimental proof, you know, like, if time travel exists any 198 00:10:43,440 --> 00:10:46,680 Speaker 1: time in the future, then you would expect to see it. Now. 199 00:10:46,720 --> 00:10:49,560 Speaker 1: I love that. It's just such a powerful argument. It 200 00:10:49,559 --> 00:10:52,720 Speaker 1: sort of reminds me of Stephen Hawking's famous invitation to 201 00:10:52,840 --> 00:10:56,120 Speaker 1: time travelers, where he threw a party and then he 202 00:10:56,200 --> 00:10:59,600 Speaker 1: posted the invitation later after the party. The idea of 203 00:10:59,640 --> 00:11:01,640 Speaker 1: being that time travelers, you know, they should be able 204 00:11:01,679 --> 00:11:04,240 Speaker 1: to get there anyway, but of course nobody should have 205 00:11:04,400 --> 00:11:08,520 Speaker 1: to his party, well that we know of. He might 206 00:11:08,520 --> 00:11:13,280 Speaker 1: have dispensed with them, or maybe he is a time traveler. 207 00:11:16,000 --> 00:11:18,319 Speaker 1: Oh that's a good premise. For a sci fi movie 208 00:11:18,360 --> 00:11:21,480 Speaker 1: like the Time Traveler Hunters trying to eliminate all evidence 209 00:11:21,520 --> 00:11:24,840 Speaker 1: of the time travelers. Well that that kind of plays 210 00:11:24,880 --> 00:11:27,840 Speaker 1: into um you know, some of what you're talking about 211 00:11:27,840 --> 00:11:29,640 Speaker 1: about it being if it if it does exist in 212 00:11:29,679 --> 00:11:32,040 Speaker 1: the future, then it must be limited in scope. And 213 00:11:32,160 --> 00:11:33,400 Speaker 1: I guess you could look at it a couple of 214 00:11:33,400 --> 00:11:35,400 Speaker 1: different We could basically just sci fi the hell out 215 00:11:35,400 --> 00:11:38,560 Speaker 1: of it in multiple directions. But you know, you could say, like, well, 216 00:11:38,559 --> 00:11:41,880 Speaker 1: maybe travel into the past. It has a range and 217 00:11:41,920 --> 00:11:44,599 Speaker 1: we haven't reached the point to where time machines of 218 00:11:44,640 --> 00:11:47,480 Speaker 1: the future can reach us, or it's just so tightly 219 00:11:47,480 --> 00:11:49,599 Speaker 1: policed that nobody can make it back. You know, we 220 00:11:49,679 --> 00:11:52,600 Speaker 1: have time cops or or something that are that are 221 00:11:52,679 --> 00:11:56,240 Speaker 1: keeping people from making too much of a show of 222 00:11:56,240 --> 00:11:58,760 Speaker 1: the whole thing. There's so many of those science fiction 223 00:11:58,760 --> 00:12:02,400 Speaker 1: depictions of like a b time bureaucracy, you know that's 224 00:12:02,440 --> 00:12:05,120 Speaker 1: managing the time flow, like you saw that in Loki 225 00:12:05,360 --> 00:12:09,280 Speaker 1: and in Umbrella Academy, and and and in um that 226 00:12:09,280 --> 00:12:11,839 Speaker 1: book recently, this is how you win the time war. 227 00:12:12,440 --> 00:12:14,200 Speaker 1: And those can be a lot of fun, but also 228 00:12:14,280 --> 00:12:17,640 Speaker 1: I feel like they're they just make no sense at all. 229 00:12:17,760 --> 00:12:20,600 Speaker 1: You know, how do you have this weird administration that's 230 00:12:20,840 --> 00:12:25,760 Speaker 1: separated from time and also weirdly frozen in like nineties bureaucracy. 231 00:12:26,400 --> 00:12:28,280 Speaker 1: It's you know, it's fun, but not not if you 232 00:12:28,280 --> 00:12:31,120 Speaker 1: think about it really at all. What also reminds me 233 00:12:31,200 --> 00:12:33,360 Speaker 1: a lot of something I was actually chatting with you 234 00:12:33,400 --> 00:12:36,160 Speaker 1: about a couple of weeks ago when I interviewed you 235 00:12:36,280 --> 00:12:38,800 Speaker 1: for a short freelance piece for how stuff works dot 236 00:12:38,840 --> 00:12:43,480 Speaker 1: com about UM about the zoo hypothesis. You you spoke 237 00:12:43,520 --> 00:12:47,800 Speaker 1: about about that for the interview, and uh, you mentioned 238 00:12:47,800 --> 00:12:49,960 Speaker 1: that one of the strong arguments against it is that 239 00:12:50,000 --> 00:12:53,719 Speaker 1: if there is actually this, um, this conspiracy of of 240 00:12:53,800 --> 00:12:57,520 Speaker 1: aliens to avoid contact with humans and and and keep 241 00:12:57,559 --> 00:12:59,640 Speaker 1: us in the dark about the uh you know, the 242 00:12:59,640 --> 00:13:04,440 Speaker 1: Galack tick, civilizations just outside of our view. UM, the 243 00:13:04,440 --> 00:13:08,440 Speaker 1: main argument against it is that that governments as we 244 00:13:08,520 --> 00:13:11,160 Speaker 1: know them, by the only model that we know the 245 00:13:10,960 --> 00:13:13,880 Speaker 1: the the human model, are not really good at keeping secrets. 246 00:13:13,920 --> 00:13:16,680 Speaker 1: They're not good at managing secrets. And it seems like 247 00:13:16,679 --> 00:13:19,719 Speaker 1: you could also apply that to the idea of intelligent 248 00:13:19,800 --> 00:13:22,880 Speaker 1: beings or humans and the future managing the timeline and 249 00:13:22,920 --> 00:13:26,319 Speaker 1: so forth. Exactly, you know, some version of Elon Musk 250 00:13:26,320 --> 00:13:28,120 Speaker 1: in the future is get to get his hands on it, 251 00:13:28,240 --> 00:13:29,920 Speaker 1: and then he's going to launch a bunch of crazy, 252 00:13:30,400 --> 00:13:33,560 Speaker 1: you know missions, and somebody's gonna mess something up. So 253 00:13:33,640 --> 00:13:35,800 Speaker 1: it's hard to imagine that people in the future having 254 00:13:35,840 --> 00:13:39,000 Speaker 1: time travel and somehow keeping it a secret or slipping 255 00:13:39,000 --> 00:13:42,720 Speaker 1: into the past unnoticed and nobody ever, you know, breaking 256 00:13:42,720 --> 00:13:46,120 Speaker 1: the protocol or something. It's it just becomes totally implausible 257 00:13:46,640 --> 00:13:48,720 Speaker 1: the more you think about it. Picking up off that, 258 00:13:48,760 --> 00:13:51,160 Speaker 1: I mean, this is another one of the weird things 259 00:13:51,200 --> 00:13:54,600 Speaker 1: about time is it seems like time is actually one 260 00:13:54,679 --> 00:13:59,720 Speaker 1: of the arguments against the idea of a coherent galactic civilization, 261 00:14:00,280 --> 00:14:02,760 Speaker 1: if this makes any sense, because like you think, a 262 00:14:02,800 --> 00:14:05,760 Speaker 1: civilization in order to organize itself has to have some 263 00:14:06,640 --> 00:14:11,080 Speaker 1: pretty close to synchronous, uh, you know, thing going on, 264 00:14:11,200 --> 00:14:14,440 Speaker 1: Like things have to be happening pretty close to around 265 00:14:14,480 --> 00:14:16,400 Speaker 1: the same time for them. But does it even make 266 00:14:16,440 --> 00:14:19,840 Speaker 1: sense for I don't know, one planet in a galactic 267 00:14:19,880 --> 00:14:22,920 Speaker 1: civilization to be part of a civilization with one on 268 00:14:22,960 --> 00:14:24,880 Speaker 1: the other side of the galaxy? I mean, is there 269 00:14:24,920 --> 00:14:28,360 Speaker 1: you know, can they say, uh, is there such a 270 00:14:28,400 --> 00:14:31,800 Speaker 1: thing as what's happening right now on a planet on 271 00:14:31,840 --> 00:14:34,080 Speaker 1: the other side of the galaxy. Yeah, you make a 272 00:14:34,120 --> 00:14:37,560 Speaker 1: great point, because there's a speed limit to information moving 273 00:14:37,600 --> 00:14:40,520 Speaker 1: through the universe, which puts an effective limit on like 274 00:14:40,600 --> 00:14:44,040 Speaker 1: how well you can coordinate and organize things. Makes you 275 00:14:44,080 --> 00:14:46,760 Speaker 1: think about this in cosmology all the time, because there's 276 00:14:46,800 --> 00:14:50,440 Speaker 1: a like the largest thing that can exist in the universe. 277 00:14:50,840 --> 00:14:53,440 Speaker 1: Just from very simple arguments like the aged the universe 278 00:14:53,640 --> 00:14:56,520 Speaker 1: and the speed of light. You can't have an object 279 00:14:56,600 --> 00:15:02,040 Speaker 1: that's like ten thousand billion light years wide that's like coordinated, 280 00:15:02,080 --> 00:15:04,920 Speaker 1: it has like a structure that's like gravitationally bound on 281 00:15:04,960 --> 00:15:07,960 Speaker 1: itself because there hasn't been time for like a photon 282 00:15:08,040 --> 00:15:11,800 Speaker 1: to even cross over the entire size of that object. 283 00:15:12,320 --> 00:15:14,760 Speaker 1: So there's like a limit to how big the universe 284 00:15:14,800 --> 00:15:17,920 Speaker 1: can even build like a thing, not to mention like 285 00:15:17,960 --> 00:15:22,320 Speaker 1: the close coordination required like organize a galactic empire. And 286 00:15:22,360 --> 00:15:26,160 Speaker 1: so yeah, absolutely, Um, I think that the sheer size 287 00:15:26,200 --> 00:15:29,720 Speaker 1: of space definitely limits our ability to explore it unless 288 00:15:29,760 --> 00:15:34,600 Speaker 1: it breaks down into you know, lots of different unorganized entities, 289 00:15:34,640 --> 00:15:37,000 Speaker 1: like maybe we send humans in an arc off to 290 00:15:37,200 --> 00:15:40,000 Speaker 1: another star and they start their own human colony and 291 00:15:40,160 --> 00:15:41,720 Speaker 1: we're not in touch and we're not part of some 292 00:15:42,000 --> 00:15:44,240 Speaker 1: you know, political nation state. But at least we are 293 00:15:44,280 --> 00:15:47,200 Speaker 1: humans here and there are humans there. Yeah. I think 294 00:15:47,200 --> 00:15:56,160 Speaker 1: that's a great way to conceptualize it. So, I guess 295 00:15:56,160 --> 00:15:59,040 Speaker 1: coming back to time travel for a minute, I wanted 296 00:15:59,080 --> 00:16:01,400 Speaker 1: to talk about some of the specifics you offer about 297 00:16:01,720 --> 00:16:07,000 Speaker 1: physically plausible ways of traveling into the past. Uh. So 298 00:16:07,320 --> 00:16:09,160 Speaker 1: you mentioned a couple of things. You mentioned the idea 299 00:16:09,160 --> 00:16:11,640 Speaker 1: of wormholes, and then you also mentioned one that might 300 00:16:11,640 --> 00:16:15,120 Speaker 1: be less familiar to people, the idea of an infinitely 301 00:16:15,240 --> 00:16:19,800 Speaker 1: long cylinder of spinning dust, which could potentially, at least 302 00:16:20,040 --> 00:16:24,840 Speaker 1: maybe depending on something about whether something about relativity is 303 00:16:24,840 --> 00:16:28,000 Speaker 1: true or not, could potentially allow time travel into the 304 00:16:28,000 --> 00:16:31,240 Speaker 1: past through something called time loops. Could could you explain 305 00:16:31,280 --> 00:16:33,720 Speaker 1: how this would work? Like, what would this experience be 306 00:16:33,920 --> 00:16:37,440 Speaker 1: like for the time traveler? Yeah, Well, the short answer is, 307 00:16:37,480 --> 00:16:40,240 Speaker 1: we just don't know. Uh. This is a realm where 308 00:16:40,280 --> 00:16:44,240 Speaker 1: we are like on the cutting edge. Theoretically, people are 309 00:16:44,400 --> 00:16:47,960 Speaker 1: looking at the rules of how space and time bend 310 00:16:48,080 --> 00:16:51,160 Speaker 1: and twist because you know, the general relativity our theory 311 00:16:51,280 --> 00:16:55,520 Speaker 1: for space and time itself essentially tells us that space 312 00:16:55,560 --> 00:16:59,600 Speaker 1: and time bend in response to mass, and then tell 313 00:16:59,720 --> 00:17:02,320 Speaker 1: mass is how to move. So, for example, you have 314 00:17:02,360 --> 00:17:04,359 Speaker 1: an empty universe and you put a star in it, 315 00:17:04,640 --> 00:17:07,399 Speaker 1: it bends the space around the star, and then the 316 00:17:07,400 --> 00:17:09,879 Speaker 1: bending of that space tells things how to move, and 317 00:17:09,920 --> 00:17:13,399 Speaker 1: not just through space but also through time. So you 318 00:17:13,480 --> 00:17:16,800 Speaker 1: go near a black hole, for example, time is slowed down. 319 00:17:17,240 --> 00:17:19,920 Speaker 1: So there's definitely some deep connection there between space and time. 320 00:17:20,359 --> 00:17:22,920 Speaker 1: And what people have done is trying to explore extreme 321 00:17:23,000 --> 00:17:25,240 Speaker 1: scenarios of that what happens if you do this, what 322 00:17:25,359 --> 00:17:28,160 Speaker 1: happens if you do that? Is this allowed? Is that allowed? 323 00:17:28,560 --> 00:17:31,000 Speaker 1: And so it's sort of like exploring the universe, but 324 00:17:31,119 --> 00:17:34,639 Speaker 1: just inside our own heads. We can't necessarily yet go 325 00:17:34,800 --> 00:17:37,440 Speaker 1: out there and build these things in space and say, 326 00:17:37,560 --> 00:17:40,680 Speaker 1: let's see what happens experimentally, But we can do similar 327 00:17:40,800 --> 00:17:43,400 Speaker 1: like fought experiments, where we say, what would happen if 328 00:17:43,400 --> 00:17:46,639 Speaker 1: you did this, and let's just let's assume the equations 329 00:17:46,640 --> 00:17:49,600 Speaker 1: are correct and see what happens. And so there's a 330 00:17:49,600 --> 00:17:52,360 Speaker 1: couple of fund scenarios there. One, as you said, is wormholes. 331 00:17:52,960 --> 00:17:56,280 Speaker 1: These aren't really crazy because they are like connections between 332 00:17:56,600 --> 00:17:59,600 Speaker 1: different points in space, and when you think of space, 333 00:17:59,640 --> 00:18:02,280 Speaker 1: you probably think of like just sheer emptiness, you know, 334 00:18:02,320 --> 00:18:04,800 Speaker 1: the back drop the stage on which the universe happens. 335 00:18:05,200 --> 00:18:07,440 Speaker 1: But now we know that space is more complex. It 336 00:18:07,520 --> 00:18:10,359 Speaker 1: can bend and it can twist, and that might be 337 00:18:10,400 --> 00:18:11,879 Speaker 1: something that you can put in your head. You can 338 00:18:11,920 --> 00:18:15,399 Speaker 1: imagine like space bending around the Sun. But because space 339 00:18:15,560 --> 00:18:18,400 Speaker 1: is like a thing with an arrangement, it could also 340 00:18:18,440 --> 00:18:23,280 Speaker 1: do other really weird things, like be connected non trivially. 341 00:18:23,680 --> 00:18:25,440 Speaker 1: So you have like a chunk of space over here, 342 00:18:25,800 --> 00:18:28,480 Speaker 1: it can be directly connected to a chunk of space 343 00:18:28,560 --> 00:18:31,359 Speaker 1: over there. What does that mean. Well, you're used to 344 00:18:31,400 --> 00:18:34,720 Speaker 1: the space around you being connected to the space right 345 00:18:34,760 --> 00:18:36,440 Speaker 1: next to it. That's what it means to be right 346 00:18:36,520 --> 00:18:38,600 Speaker 1: next to it. Right, you take a step to the left, 347 00:18:38,640 --> 00:18:40,760 Speaker 1: you move to the next sort of piece of space. 348 00:18:41,240 --> 00:18:44,399 Speaker 1: Think of it sort of like pixels on a screen. Right, Well, 349 00:18:44,440 --> 00:18:47,399 Speaker 1: a wormhole is a connection between two points in space 350 00:18:47,440 --> 00:18:51,199 Speaker 1: that are otherwise really distant. And so you take a 351 00:18:51,200 --> 00:18:53,679 Speaker 1: step from a from one pixel and now you're in 352 00:18:53,680 --> 00:18:56,359 Speaker 1: a pixel on the other side of the screen. And 353 00:18:56,400 --> 00:18:59,840 Speaker 1: so that seems weird and impossible, but remember space can 354 00:18:59,880 --> 00:19:03,320 Speaker 1: have all sorts of strange connections, and according to the 355 00:19:03,359 --> 00:19:06,440 Speaker 1: equations of general relativity, the ones that define how space 356 00:19:06,520 --> 00:19:11,120 Speaker 1: is organized that is allowed, it is possible, and so 357 00:19:11,280 --> 00:19:13,520 Speaker 1: a couple of folks at cal Tech we're thinking about, well, 358 00:19:13,720 --> 00:19:16,680 Speaker 1: you know what about time? Is it possible for one 359 00:19:16,880 --> 00:19:18,840 Speaker 1: end of the wormhole to be in one place and 360 00:19:18,880 --> 00:19:23,080 Speaker 1: the other end to be in another time because, as 361 00:19:23,119 --> 00:19:26,320 Speaker 1: you were mentioning earlier, like the notion of simultaneity, like 362 00:19:26,800 --> 00:19:30,679 Speaker 1: when is now depends really on where you are. Also, 363 00:19:31,359 --> 00:19:33,200 Speaker 1: so they have this idea to take one end of 364 00:19:33,240 --> 00:19:36,000 Speaker 1: the wormhole and you accelerate it near the speed of light. 365 00:19:36,280 --> 00:19:38,880 Speaker 1: That effectively it can be sort of back in time. 366 00:19:39,560 --> 00:19:42,639 Speaker 1: And this all works theoretically, but it also sort of 367 00:19:42,680 --> 00:19:46,080 Speaker 1: contradicts other things we know, like if you go through 368 00:19:46,080 --> 00:19:49,159 Speaker 1: this wormhole and you come out in the past, you know, 369 00:19:49,400 --> 00:19:51,959 Speaker 1: doesn't that break things like causality? And you come out 370 00:19:51,960 --> 00:19:55,159 Speaker 1: in the past and kill yourself before you um do 371 00:19:55,320 --> 00:19:57,480 Speaker 1: the experiment, then you don't do the experiment, you don't 372 00:19:57,480 --> 00:20:00,720 Speaker 1: come out in the past. So it appears to create paradoxes, 373 00:20:01,160 --> 00:20:04,399 Speaker 1: and nobody knows like how to resolve that. Does that 374 00:20:04,440 --> 00:20:06,639 Speaker 1: mean that these things are impossible? Does that mean if 375 00:20:06,640 --> 00:20:09,119 Speaker 1: you did that the universe would like disappear in a 376 00:20:09,160 --> 00:20:12,159 Speaker 1: puff of logic? Nobody really knows what would happen, so 377 00:20:12,200 --> 00:20:14,320 Speaker 1: that it's a bit of a contradiction in the theory 378 00:20:14,400 --> 00:20:18,399 Speaker 1: itself that it predicts something which seems to be disallowed 379 00:20:18,400 --> 00:20:21,760 Speaker 1: by other parts of the theory. And it's a similar 380 00:20:21,800 --> 00:20:26,240 Speaker 1: idea for these closed timelike curves. People said, if you 381 00:20:26,680 --> 00:20:31,280 Speaker 1: create these infinitely long cylinders of spinning dust, which doesn't 382 00:20:31,320 --> 00:20:34,800 Speaker 1: sound easy to do, then it bends time in this 383 00:20:34,840 --> 00:20:38,080 Speaker 1: way that the time then as you move forward in time, 384 00:20:39,080 --> 00:20:42,600 Speaker 1: you're actually moving sort of like sideways through space time 385 00:20:43,000 --> 00:20:45,480 Speaker 1: in a way that's similar to the experience of going 386 00:20:45,520 --> 00:20:49,560 Speaker 1: into a black hole. Outside a black hole, time always 387 00:20:49,600 --> 00:20:53,440 Speaker 1: moves forwards. Inside a black hole, space has bent so 388 00:20:53,520 --> 00:20:56,480 Speaker 1: much that space only moves towards the center of the 389 00:20:56,520 --> 00:21:00,280 Speaker 1: black hole. It's like one direction to space. So if 390 00:21:00,280 --> 00:21:03,639 Speaker 1: you imagine space being distorted, not quite as much as 391 00:21:03,640 --> 00:21:05,920 Speaker 1: a black hole, but sort of in a similar direction 392 00:21:05,920 --> 00:21:09,680 Speaker 1: that it sort of bends space sideways, then you can 393 00:21:09,720 --> 00:21:12,240 Speaker 1: create these paths where something can move in a loop 394 00:21:12,320 --> 00:21:16,560 Speaker 1: through time. Um, but you would be trapped on that loop, 395 00:21:16,600 --> 00:21:18,720 Speaker 1: so you wouldn't be able to like change anything. It's 396 00:21:18,720 --> 00:21:21,280 Speaker 1: like a fixed loop, sort of like Harry Potter style 397 00:21:21,760 --> 00:21:23,720 Speaker 1: loop through time where every time you go through, it's 398 00:21:23,760 --> 00:21:26,640 Speaker 1: exactly the same thing happening. And these are really fun 399 00:21:26,680 --> 00:21:29,600 Speaker 1: because nobody knows like if these are actually possible, and 400 00:21:29,720 --> 00:21:32,560 Speaker 1: what would happen if you actually went through them. So 401 00:21:32,560 --> 00:21:35,920 Speaker 1: so we don't really know, for instance, like what conceivable 402 00:21:36,200 --> 00:21:41,359 Speaker 1: reason there would be for a civilization to conceivably construct 403 00:21:41,359 --> 00:21:44,480 Speaker 1: one of these, Yeah, because we don't know practically what 404 00:21:44,520 --> 00:21:47,879 Speaker 1: you could achieve. And also, an infinite cylinder spitting dust 405 00:21:47,960 --> 00:21:51,280 Speaker 1: sounds like an expensive project, you know, the word infinite 406 00:21:51,320 --> 00:21:55,040 Speaker 1: seems to raise some doubts. And when it comes to wormholes, 407 00:21:55,359 --> 00:21:58,800 Speaker 1: people know how to calculate whether a wormhole is allowed 408 00:21:58,840 --> 00:22:01,560 Speaker 1: by the theory of general activity. Nobody knows how to 409 00:22:01,640 --> 00:22:05,280 Speaker 1: build a wormhole. You know. It's sort of like saying, Okay, 410 00:22:05,320 --> 00:22:08,760 Speaker 1: it's possible to have an apple pie, but but we 411 00:22:08,920 --> 00:22:11,879 Speaker 1: don't have a recipe for making one. Right. It's a 412 00:22:12,000 --> 00:22:13,760 Speaker 1: different thing to say, like I know how to put 413 00:22:13,800 --> 00:22:16,960 Speaker 1: it together than to say it's technically allowed to exist 414 00:22:17,320 --> 00:22:19,800 Speaker 1: in the universe. You know, It's like if you say, well, 415 00:22:19,960 --> 00:22:22,720 Speaker 1: the sun is allowed by the laws of physics, but 416 00:22:22,800 --> 00:22:24,439 Speaker 1: I don't know how to make it happen. If I 417 00:22:24,520 --> 00:22:27,679 Speaker 1: just start from a cloud of gas, for example, and 418 00:22:27,720 --> 00:22:29,720 Speaker 1: so that's a big puzzle. Nobody really knows how to 419 00:22:29,760 --> 00:22:32,840 Speaker 1: build a wormhole or even keep one open. Um if 420 00:22:32,880 --> 00:22:36,000 Speaker 1: you did manage to build one, Are there any reasons 421 00:22:36,040 --> 00:22:40,440 Speaker 1: to suspect that wormholes exist naturally? Oh? Great question? Not 422 00:22:40,560 --> 00:22:44,520 Speaker 1: yet know. Um. Some people wonder if there are wormholes 423 00:22:44,520 --> 00:22:48,119 Speaker 1: that connect the super massive black holes at the hearts 424 00:22:48,160 --> 00:22:51,080 Speaker 1: of all of our galaxies, but there's not like any 425 00:22:51,160 --> 00:22:55,000 Speaker 1: evidence out there anything that can't be explained without wormholes 426 00:22:55,000 --> 00:22:58,639 Speaker 1: that you would need wormholes to explain. Um, that would 427 00:22:58,640 --> 00:23:01,440 Speaker 1: be super cool, though, Um, I'm not aware of any 428 00:23:01,480 --> 00:23:04,520 Speaker 1: evidence like that. Well, Daniel, you also have a chapter 429 00:23:04,560 --> 00:23:06,760 Speaker 1: in the book that I really liked on the question 430 00:23:06,840 --> 00:23:10,320 Speaker 1: of will time ever stop? And I think this is 431 00:23:10,359 --> 00:23:13,000 Speaker 1: one of those great questions because it's a yes or 432 00:23:13,000 --> 00:23:18,000 Speaker 1: no question, and like many big questions in physical cosmology, 433 00:23:18,080 --> 00:23:20,600 Speaker 1: it's a binary. But no matter which answer it is, 434 00:23:20,680 --> 00:23:24,280 Speaker 1: it's mind boggling, like it is impossible to imagine time 435 00:23:24,440 --> 00:23:28,840 Speaker 1: either stopping or going on forever. Uh So, so, what 436 00:23:29,160 --> 00:23:32,000 Speaker 1: are your thoughts here about whether time will ever stop? 437 00:23:32,840 --> 00:23:35,000 Speaker 1: I go, you're feeling there. And I also think it's 438 00:23:35,000 --> 00:23:38,679 Speaker 1: really fascinating to go back through history and read about 439 00:23:38,880 --> 00:23:43,359 Speaker 1: which concept felt more natural to people. Initially, it felt 440 00:23:43,560 --> 00:23:47,000 Speaker 1: to people like time should go on forever. Obviously, that 441 00:23:47,080 --> 00:23:49,560 Speaker 1: was like a hundred fifty years ago, before we knew 442 00:23:49,600 --> 00:23:52,600 Speaker 1: that the universe was expanding. People looked out in the 443 00:23:52,640 --> 00:23:54,480 Speaker 1: stars and they looked like they were just sort of 444 00:23:54,520 --> 00:23:56,760 Speaker 1: hanging out, and they thought, maybe the universe is just 445 00:23:56,760 --> 00:24:00,239 Speaker 1: sort of there, and so obviously it's been there forever, right, 446 00:24:00,640 --> 00:24:03,480 Speaker 1: And that was like this, you know, de facto assumption 447 00:24:03,560 --> 00:24:07,920 Speaker 1: in science until Hubble discovered that the universe is expanding, 448 00:24:08,400 --> 00:24:11,080 Speaker 1: and that gave the universe sort of like a direction. 449 00:24:11,119 --> 00:24:14,240 Speaker 1: It's like things are changing, and as you look back 450 00:24:14,280 --> 00:24:17,400 Speaker 1: in time, that suggests, you know, something a moment when 451 00:24:17,440 --> 00:24:21,040 Speaker 1: the universe was like crazy infinitely dense. So it suggested 452 00:24:21,040 --> 00:24:24,040 Speaker 1: a beginning. And that must have been an incredible sort 453 00:24:24,040 --> 00:24:30,200 Speaker 1: of mind bending mental gymnastics to execute to go from thinking, oh, 454 00:24:30,240 --> 00:24:32,520 Speaker 1: it makes sense for the universe to be infinite in 455 00:24:32,600 --> 00:24:35,600 Speaker 1: time to going to like, oh, the universe had a beginning, 456 00:24:35,640 --> 00:24:38,000 Speaker 1: and now let's trying to figure out what that beginning was. 457 00:24:38,920 --> 00:24:41,800 Speaker 1: Um So, I think that's really interesting, And you know, 458 00:24:41,880 --> 00:24:44,479 Speaker 1: I think the thing that's really cool about this question 459 00:24:44,600 --> 00:24:46,800 Speaker 1: is not just that it's tangible because it makes you wonder, 460 00:24:46,840 --> 00:24:48,480 Speaker 1: like am I going to go on forever? As the 461 00:24:48,560 --> 00:24:51,320 Speaker 1: universe always going to be here? But because it really 462 00:24:51,320 --> 00:24:54,800 Speaker 1: gets at the heart of the deepest problem in physics 463 00:24:54,960 --> 00:24:59,159 Speaker 1: right now, the like the fundamental conflict we have between 464 00:24:59,240 --> 00:25:02,720 Speaker 1: two idea he is in physics, which are quantum mechanics 465 00:25:02,880 --> 00:25:06,240 Speaker 1: and general relativity. You know, we have a quantum mechanical 466 00:25:06,320 --> 00:25:08,879 Speaker 1: description of how like particles bounce off each other, and 467 00:25:08,880 --> 00:25:11,080 Speaker 1: we you know, have a lot of questions about how 468 00:25:11,080 --> 00:25:13,040 Speaker 1: that works, but we have a pretty good theory for 469 00:25:13,160 --> 00:25:16,560 Speaker 1: you know, understanding quantum particles, and we've been talking about 470 00:25:16,560 --> 00:25:19,679 Speaker 1: general relativity, you know, how space bends and how it 471 00:25:19,720 --> 00:25:22,320 Speaker 1: affects time and what happens in black holes and all 472 00:25:22,320 --> 00:25:25,560 Speaker 1: that stuff also very successful. The problem is that these 473 00:25:25,560 --> 00:25:29,520 Speaker 1: two theories nobody knows how to bring them together, and critically, 474 00:25:29,720 --> 00:25:33,479 Speaker 1: they have very different stories to tell about what time is. 475 00:25:34,080 --> 00:25:37,760 Speaker 1: They treat time totally differently with huge consequences for the 476 00:25:37,800 --> 00:25:41,439 Speaker 1: answer to this question will time ever stop? And so 477 00:25:41,520 --> 00:25:43,640 Speaker 1: to me, this is a fun question because it puts 478 00:25:43,640 --> 00:25:46,960 Speaker 1: its finger on right on that conflict. Yes, so there 479 00:25:47,119 --> 00:25:51,479 Speaker 1: is there's a concept that you introduce in this chapter 480 00:25:51,640 --> 00:25:55,960 Speaker 1: about uh sort of time as we experience it, being 481 00:25:56,000 --> 00:25:59,639 Speaker 1: a sort of special case or special circumstance of a 482 00:25:59,720 --> 00:26:04,040 Speaker 1: hypethetical substance you refer to as meta time. Can you 483 00:26:04,080 --> 00:26:07,360 Speaker 1: explain something, well, like what are you getting at here? Well, 484 00:26:07,359 --> 00:26:11,879 Speaker 1: one of the basic questions is is time fundamental or 485 00:26:12,000 --> 00:26:15,000 Speaker 1: is it emergent? You know, a deep question in modern 486 00:26:15,040 --> 00:26:18,480 Speaker 1: physics is like, what are the essential ingredients to the universe? 487 00:26:18,520 --> 00:26:21,080 Speaker 1: What did it start with? And then what sort of 488 00:26:21,119 --> 00:26:24,280 Speaker 1: arises out of that out of the complexity of the 489 00:26:24,320 --> 00:26:27,840 Speaker 1: possible interactions. You know, for example, if you're playing with legos, 490 00:26:28,080 --> 00:26:31,080 Speaker 1: the fundamental ingredients are the basic pieces, and from that 491 00:26:31,119 --> 00:26:34,639 Speaker 1: you can make complicated things dinosaurs or pirates or spaceships 492 00:26:34,720 --> 00:26:37,360 Speaker 1: or whatever. But those spaceships they're emergent, you know, They're 493 00:26:37,359 --> 00:26:39,439 Speaker 1: not necessary. They don't have to exist. You can take 494 00:26:39,480 --> 00:26:41,840 Speaker 1: it apart and just have the legos. In the same way, 495 00:26:41,840 --> 00:26:45,520 Speaker 1: in our universe there are complicated things like ice cream 496 00:26:45,760 --> 00:26:49,440 Speaker 1: and hurricanes, but those don't have to exist in the universe, 497 00:26:49,520 --> 00:26:52,880 Speaker 1: right You can imagine a universe without hurricanes or without 498 00:26:52,920 --> 00:26:55,080 Speaker 1: ice cream, as sad as that is. So, then the 499 00:26:55,160 --> 00:26:57,680 Speaker 1: question is what are the basic elements of the universe 500 00:26:57,800 --> 00:27:00,359 Speaker 1: and for a long time, you know, people like Newton 501 00:27:00,720 --> 00:27:03,680 Speaker 1: thought that, well, obviously space and time are fundamentals of 502 00:27:03,720 --> 00:27:06,400 Speaker 1: the universe. They're just like, you gotta have that, right, 503 00:27:06,920 --> 00:27:09,639 Speaker 1: And now people are wondering, like, well, is that really true? 504 00:27:10,160 --> 00:27:13,520 Speaker 1: Is it possible to have a universe without space or 505 00:27:13,560 --> 00:27:17,359 Speaker 1: without time? You know, we gotta when you're really digging 506 00:27:17,440 --> 00:27:19,480 Speaker 1: deep into the nature of the universe, you gotta push 507 00:27:19,560 --> 00:27:22,640 Speaker 1: hard on the fundamental assumptions. So there are a lot 508 00:27:22,680 --> 00:27:26,399 Speaker 1: of ideas now about how space could be emergent, you know, 509 00:27:26,440 --> 00:27:29,280 Speaker 1: how it could be that the universe itself, that space 510 00:27:29,320 --> 00:27:32,000 Speaker 1: is not a natural thing, that like ice cream, you 511 00:27:32,000 --> 00:27:34,840 Speaker 1: could have a time in the universe where there wasn't 512 00:27:34,880 --> 00:27:39,000 Speaker 1: any space. The space is like just briefly, the stitching 513 00:27:39,080 --> 00:27:44,000 Speaker 1: together of these um separated pixels of space using quantum 514 00:27:44,080 --> 00:27:47,399 Speaker 1: entanglement to sort of weave together this idea of space, 515 00:27:47,440 --> 00:27:51,800 Speaker 1: these relations between different locations that we experience, and we 516 00:27:51,800 --> 00:27:54,840 Speaker 1: could talk about that for an hour um. But even 517 00:27:54,880 --> 00:27:58,240 Speaker 1: moving beyond that, now folks are wondering, like, is time 518 00:27:58,520 --> 00:28:02,040 Speaker 1: also emergent? Is it possible that time is not a 519 00:28:02,080 --> 00:28:05,679 Speaker 1: fundamental property of the universe, but it just sort of 520 00:28:05,760 --> 00:28:09,800 Speaker 1: something that exists now and it's really hard to even 521 00:28:09,840 --> 00:28:12,040 Speaker 1: think or talk about it because, like I just said, 522 00:28:12,280 --> 00:28:15,560 Speaker 1: it exists. Now I'm using time to talk about when 523 00:28:15,680 --> 00:28:19,560 Speaker 1: time is. It's very complicated and confusing. But there are 524 00:28:19,600 --> 00:28:23,000 Speaker 1: some theories that tell us that time might be not 525 00:28:23,119 --> 00:28:25,960 Speaker 1: an illusion, right, not in the sense that it doesn't exist, 526 00:28:26,359 --> 00:28:29,000 Speaker 1: but it might not be fundamental, that it might arise 527 00:28:29,480 --> 00:28:34,679 Speaker 1: from complex interactions of smaller, more fundamental elements of the universe. 528 00:28:35,240 --> 00:28:37,919 Speaker 1: And so that's this idea of meta time. You have 529 00:28:37,960 --> 00:28:40,640 Speaker 1: to imagine some like deeper laws of physics that control 530 00:28:40,680 --> 00:28:44,000 Speaker 1: those fundamental bits that I'm being vague about because we 531 00:28:44,000 --> 00:28:46,040 Speaker 1: have no idea what they would be or what they are, 532 00:28:46,200 --> 00:28:49,320 Speaker 1: what the rules are. And And if this seems sort 533 00:28:49,320 --> 00:28:52,040 Speaker 1: of like frustrating, it's because we're at the very beginning 534 00:28:52,200 --> 00:28:55,520 Speaker 1: of even talking about the answers, because we're just formulating 535 00:28:55,560 --> 00:28:57,920 Speaker 1: the questions. You know, sometimes it takes like a hundred 536 00:28:58,000 --> 00:29:01,880 Speaker 1: years to figure out, Okay, the question to ask is 537 00:29:01,880 --> 00:29:04,520 Speaker 1: is there always time in the universe? What does that mean? 538 00:29:04,640 --> 00:29:07,720 Speaker 1: And how do you even think about a universe without time? 539 00:29:08,040 --> 00:29:10,080 Speaker 1: Then you can start to make progress on the crazy 540 00:29:10,160 --> 00:29:13,040 Speaker 1: ideas that might explain it. Uh, this may be kind 541 00:29:13,040 --> 00:29:15,000 Speaker 1: of a tangent. But this actually makes me wonder about 542 00:29:15,160 --> 00:29:18,160 Speaker 1: a question that's come up on the show before. Do 543 00:29:18,200 --> 00:29:22,280 Speaker 1: you have a view on what the present is, on 544 00:29:22,480 --> 00:29:27,719 Speaker 1: whether something special is actually happening in the present. Uh, Like, 545 00:29:27,800 --> 00:29:31,440 Speaker 1: does only the present exist? Or does all of time exist? 546 00:29:32,120 --> 00:29:35,520 Speaker 1: It's a really great question. We don't understand that at all. 547 00:29:35,680 --> 00:29:38,000 Speaker 1: I don't understand it. I don't even know if it's 548 00:29:38,000 --> 00:29:40,960 Speaker 1: a question of science or if it's a question of philosophy, 549 00:29:41,040 --> 00:29:44,080 Speaker 1: because it goes into the nature of consciousness. You know, 550 00:29:44,240 --> 00:29:47,160 Speaker 1: does the whole timeline exist and we only experience part 551 00:29:47,160 --> 00:29:50,720 Speaker 1: of it? Or you know, does only this moment exist? Um. 552 00:29:50,800 --> 00:29:53,440 Speaker 1: Physics doesn't have a great way to even define what 553 00:29:53,600 --> 00:29:57,520 Speaker 1: the present is um, and so it's it's pretty hard 554 00:29:57,560 --> 00:29:59,880 Speaker 1: to put your finger on it um. And I love 555 00:30:00,120 --> 00:30:02,280 Speaker 1: because these are questions that like, we don't even really 556 00:30:02,320 --> 00:30:06,120 Speaker 1: know how to attack these questions. And what that suggests 557 00:30:06,560 --> 00:30:09,000 Speaker 1: is that there's something wrong and the way we're organizing 558 00:30:09,000 --> 00:30:12,360 Speaker 1: our thinking. You know, it's like if you're asking a 559 00:30:12,480 --> 00:30:15,400 Speaker 1: question and you're just using the wrong language, we're using 560 00:30:15,400 --> 00:30:19,080 Speaker 1: the wrong notation, then your question seems really complicated and confusing. 561 00:30:19,080 --> 00:30:21,480 Speaker 1: And if you learn a new perspective and then suddenly 562 00:30:21,520 --> 00:30:24,320 Speaker 1: would make sense. You know, I'm reminded of that Far 563 00:30:24,400 --> 00:30:28,080 Speaker 1: Side cartoon where the scientists are trying to understand dolphins 564 00:30:28,560 --> 00:30:31,440 Speaker 1: and they're writing down phonetically what the dolphins are saying, 565 00:30:31,480 --> 00:30:34,960 Speaker 1: and they're saying things like you know, obla Espanol and 566 00:30:35,000 --> 00:30:37,040 Speaker 1: the you know, the scientists don't speak Spanish, so tho 567 00:30:37,120 --> 00:30:39,360 Speaker 1: to them, it's just nonsense. My bodies if they if 568 00:30:39,360 --> 00:30:41,440 Speaker 1: they knew the language, it would all click together. And 569 00:30:41,480 --> 00:30:43,760 Speaker 1: I feel like that's the problem we have sometimes that 570 00:30:43,920 --> 00:30:46,400 Speaker 1: was just not speaking the right language at the universe yet, 571 00:30:46,880 --> 00:30:48,959 Speaker 1: and that's why some of these questions are awkward and 572 00:30:49,080 --> 00:30:51,760 Speaker 1: really hard to grapple with. I thought you were gonna 573 00:30:51,760 --> 00:30:58,360 Speaker 1: say today's physicists are only equipped with cow tools only 574 00:30:58,400 --> 00:31:03,000 Speaker 1: for spherical cows. You know, all of this um also, 575 00:31:03,120 --> 00:31:07,080 Speaker 1: it reminds me a bit of the Copernican principle to UM. 576 00:31:07,120 --> 00:31:09,360 Speaker 1: But but going beyond just the idea of like, you know, 577 00:31:10,640 --> 00:31:13,960 Speaker 1: there being some uh I we should not not see 578 00:31:14,000 --> 00:31:17,680 Speaker 1: that there's something privileged about about our planet or about humans. 579 00:31:17,720 --> 00:31:20,640 Speaker 1: But but could you could you even apply that based 580 00:31:20,640 --> 00:31:22,720 Speaker 1: on what you're saying to to the present moment, to 581 00:31:22,800 --> 00:31:26,080 Speaker 1: this time that in which from which we are viewing 582 00:31:26,240 --> 00:31:29,560 Speaker 1: the universe. Yeah. Probably, And I think that's why a 583 00:31:29,640 --> 00:31:32,440 Speaker 1: lot of progress could be made if we ever did 584 00:31:33,040 --> 00:31:36,400 Speaker 1: get to talk to alien scientists, because I think we 585 00:31:36,400 --> 00:31:39,920 Speaker 1: would learn a lot about, um, you know, the biases 586 00:31:39,920 --> 00:31:43,400 Speaker 1: that creep into our questions and our reference frame for 587 00:31:43,480 --> 00:31:47,720 Speaker 1: answering those questions because of our human experience, and alien 588 00:31:47,760 --> 00:31:50,440 Speaker 1: intelligence that might have a very different relationship with the 589 00:31:50,560 --> 00:31:53,640 Speaker 1: concept of time, might have a very different treatment of 590 00:31:53,680 --> 00:31:57,360 Speaker 1: it mathematically and physically, and might make a lot more sense. 591 00:31:57,720 --> 00:32:01,680 Speaker 1: You know. The problem with alien intelligence, of course, is 592 00:32:01,760 --> 00:32:05,240 Speaker 1: you know, finding them, talking to them, decoding their language, 593 00:32:05,800 --> 00:32:09,360 Speaker 1: and then if they are so fundamentally different that they've 594 00:32:09,440 --> 00:32:12,360 Speaker 1: made that they avoid human biases, they might be impossible 595 00:32:12,360 --> 00:32:16,840 Speaker 1: to understand. And so while it's tantalizing to imagine that 596 00:32:16,880 --> 00:32:19,000 Speaker 1: like aliens are out there with the answers the deep 597 00:32:19,080 --> 00:32:21,800 Speaker 1: questions about the universe, it might also be that, uh 598 00:32:22,320 --> 00:32:24,880 Speaker 1: that we could never understand what they have to say. 599 00:32:24,920 --> 00:32:27,000 Speaker 1: I have long thought we should outsource all of our 600 00:32:27,000 --> 00:32:33,240 Speaker 1: physics research to like a seventeen dimensional octopus. Um, if 601 00:32:33,280 --> 00:32:34,760 Speaker 1: you know one, I'd like to meet it, because I 602 00:32:34,880 --> 00:32:44,280 Speaker 1: got questions than uh so, but to come back to 603 00:32:44,320 --> 00:32:47,720 Speaker 1: the idea of will time ever stop? You talk about 604 00:32:47,760 --> 00:32:50,959 Speaker 1: a couple of possibilities for what that would look like. 605 00:32:51,000 --> 00:32:53,440 Speaker 1: Say that you know the far future of our own universe, 606 00:32:53,480 --> 00:32:56,040 Speaker 1: at least at least what we can reason from what 607 00:32:56,120 --> 00:32:58,200 Speaker 1: we know today, and and a couple of these options 608 00:32:58,240 --> 00:33:00,600 Speaker 1: are are the Big Crunch and the heat death of 609 00:33:00,600 --> 00:33:02,200 Speaker 1: the universe. Do you do you want to talk about 610 00:33:02,240 --> 00:33:06,080 Speaker 1: what those would means as best we can guess for 611 00:33:06,200 --> 00:33:10,880 Speaker 1: time itself. Yes, So remember that there are two paths 612 00:33:10,880 --> 00:33:12,960 Speaker 1: to go down if you're asking questions about the deep 613 00:33:13,000 --> 00:33:15,440 Speaker 1: future of the universe, and one is quantum mechanical and 614 00:33:15,480 --> 00:33:18,480 Speaker 1: the other one is general relativity. And quantum mechanics is 615 00:33:18,520 --> 00:33:22,360 Speaker 1: pretty straightforward about this. It says that, look, time always 616 00:33:22,360 --> 00:33:25,800 Speaker 1: existed and time will always exist. And there's a pretty 617 00:33:25,840 --> 00:33:30,360 Speaker 1: simple argument there because according to quantum mechanics, quantum information 618 00:33:30,640 --> 00:33:35,000 Speaker 1: can't be destroyed, like when something happens um, you know, 619 00:33:35,080 --> 00:33:38,080 Speaker 1: the information about what used to happen is encoded into 620 00:33:38,160 --> 00:33:41,920 Speaker 1: the future, and so it suggests that time has always existed. 621 00:33:41,920 --> 00:33:45,760 Speaker 1: There's no mechanism in quantum mechanics for time to start. 622 00:33:46,040 --> 00:33:48,360 Speaker 1: It should always have existed, and you flip it around 623 00:33:48,360 --> 00:33:51,280 Speaker 1: the other direction, it should always exist, so they should 624 00:33:51,320 --> 00:33:54,880 Speaker 1: always be a universe, and clocks should always tick forwards 625 00:33:54,920 --> 00:33:58,440 Speaker 1: according to quantum mechanics. But that assumes you know that 626 00:33:58,560 --> 00:34:02,360 Speaker 1: space is flat, and bole and general relativity, the other 627 00:34:02,440 --> 00:34:05,560 Speaker 1: pillar of modern physics, tells us that space is not simple. 628 00:34:05,680 --> 00:34:09,759 Speaker 1: It's not flat, it's complicated. It's expanding, and you know, 629 00:34:10,120 --> 00:34:13,800 Speaker 1: the mechanism by which space is expanding is not something 630 00:34:13,840 --> 00:34:16,879 Speaker 1: that we understand. Hub will discover a hundreds something years 631 00:34:16,880 --> 00:34:19,080 Speaker 1: ago that the universe is expanding and things are moving 632 00:34:19,120 --> 00:34:21,719 Speaker 1: away from us, And then twenty something years ago we 633 00:34:21,840 --> 00:34:26,680 Speaker 1: discovered even more mind boggling lee that that expansion is accelerating. Right, 634 00:34:26,800 --> 00:34:29,680 Speaker 1: It's not like stuff is moving through space and gradually 635 00:34:29,680 --> 00:34:33,920 Speaker 1: slowing down and maybe eventually gonna stop and turn around 636 00:34:33,920 --> 00:34:37,560 Speaker 1: and come back um and collapse, but that it's speeding up, 637 00:34:37,719 --> 00:34:41,279 Speaker 1: which means that there's some massive, incredibly powerful force in 638 00:34:41,320 --> 00:34:45,560 Speaker 1: the universe that's literally tearing it apart. Because we don't 639 00:34:45,600 --> 00:34:47,880 Speaker 1: know the mechanism for it, though, we can't predict what 640 00:34:47,920 --> 00:34:50,480 Speaker 1: it's gonna do, Like it turned on about five billion 641 00:34:50,560 --> 00:34:53,239 Speaker 1: years ago, started tearing the universe apart. Will it do 642 00:34:53,320 --> 00:34:55,920 Speaker 1: that forever? If so, you end up with like a 643 00:34:56,040 --> 00:34:59,080 Speaker 1: universe with everything is super far apart. It's just like 644 00:34:59,160 --> 00:35:02,880 Speaker 1: a bunch of black hole holes from collapsed galaxies, separated 645 00:35:02,920 --> 00:35:07,480 Speaker 1: by you know, unthinkably vast distances. Even compared to the 646 00:35:07,560 --> 00:35:11,399 Speaker 1: distances we see between our galaxy and other galaxies today, 647 00:35:11,520 --> 00:35:13,600 Speaker 1: you know, these galaxies would be so far apart that 648 00:35:13,640 --> 00:35:15,920 Speaker 1: they could never even see each other. You know, light 649 00:35:16,160 --> 00:35:19,840 Speaker 1: would never reach one from the other. On the other hand, 650 00:35:20,000 --> 00:35:22,840 Speaker 1: dark energy could change its direction, it could stop, it 651 00:35:22,840 --> 00:35:25,920 Speaker 1: could turn around, it could cause the universe to collapse 652 00:35:26,239 --> 00:35:30,200 Speaker 1: back down into an incredible moment of singularity at the 653 00:35:30,320 --> 00:35:33,440 Speaker 1: end of the universe um, and then we can ask 654 00:35:33,520 --> 00:35:36,359 Speaker 1: questions like, well, what happens then, you know, does the 655 00:35:36,480 --> 00:35:41,719 Speaker 1: universe stop when you reach another singularity, another moment of 656 00:35:41,760 --> 00:35:46,880 Speaker 1: incredible density. We just don't know because general relativity describes 657 00:35:46,960 --> 00:35:49,879 Speaker 1: that process. But when you actually get to the singularity, 658 00:35:50,040 --> 00:35:53,320 Speaker 1: people think of singularities is like a feature of general relativity. 659 00:35:53,520 --> 00:35:56,800 Speaker 1: Really they're like a failure of general relativity. It can't 660 00:35:56,840 --> 00:35:59,279 Speaker 1: predict anything that happens there. Doesn't know what to do. 661 00:36:00,000 --> 00:36:02,279 Speaker 1: It's like, well, that's the direction you're going, but once 662 00:36:02,320 --> 00:36:03,880 Speaker 1: you get there, I can't tell you what's going to 663 00:36:03,960 --> 00:36:07,120 Speaker 1: happen next. So if that happens, we just really don't 664 00:36:07,120 --> 00:36:09,160 Speaker 1: know what the fate of the universe would be in 665 00:36:09,200 --> 00:36:11,560 Speaker 1: that scenario, but you know, it wouldn't be pleasant for 666 00:36:11,680 --> 00:36:15,680 Speaker 1: humans or for seventeen seventeen dimensional octopi. But I guess 667 00:36:15,680 --> 00:36:17,480 Speaker 1: with with the other option, with like you know, the 668 00:36:17,800 --> 00:36:21,160 Speaker 1: heat death of the universe, everything just expanding and cooling 669 00:36:21,239 --> 00:36:25,200 Speaker 1: and reaching some kind of equilibrium where um, where there's 670 00:36:25,200 --> 00:36:29,640 Speaker 1: no there's no imbalance to distribute any further. I think 671 00:36:29,640 --> 00:36:31,719 Speaker 1: in the book you raised the idea that this could 672 00:36:31,880 --> 00:36:34,800 Speaker 1: in a way represent a threat to to our concept 673 00:36:34,800 --> 00:36:38,640 Speaker 1: of time because time would maybe in itself, time has 674 00:36:38,719 --> 00:36:40,799 Speaker 1: something to do with entropy, and this would be a 675 00:36:40,840 --> 00:36:45,800 Speaker 1: state of maximum entropy. Yeah, we see the universe proceeding 676 00:36:45,840 --> 00:36:50,040 Speaker 1: through time and we see entropy increasing, and entropy is 677 00:36:50,040 --> 00:36:52,279 Speaker 1: a really tricky topic. You hear people talk about it 678 00:36:52,280 --> 00:36:54,160 Speaker 1: a lot, but it's really hard to sort of grapple 679 00:36:54,200 --> 00:36:57,319 Speaker 1: with intellectually, and people try to think about it in 680 00:36:57,400 --> 00:37:00,400 Speaker 1: terms of like amount of disorder in the universe, but 681 00:37:00,440 --> 00:37:04,719 Speaker 1: that can be pretty misleading. Technically, it's really relates to 682 00:37:04,760 --> 00:37:08,880 Speaker 1: the number of different ways you can arrange the microscopic 683 00:37:09,160 --> 00:37:12,640 Speaker 1: nature of the universe to be consistent with the macroscopic 684 00:37:12,719 --> 00:37:15,520 Speaker 1: nature that you observe. That's a little bit more subtle, 685 00:37:15,560 --> 00:37:18,680 Speaker 1: but it's actually a more accurate guide to what entropy is. 686 00:37:19,000 --> 00:37:20,920 Speaker 1: And what we notice is that entropy seems to be 687 00:37:20,960 --> 00:37:24,959 Speaker 1: increasing through the universe, like there's something we've observed, and 688 00:37:25,320 --> 00:37:27,640 Speaker 1: a lot of places in physics seem to be sort 689 00:37:27,640 --> 00:37:30,960 Speaker 1: of like ambivalent about time. The laws will run the 690 00:37:31,000 --> 00:37:34,319 Speaker 1: same forward or backwards. It doesn't really matter, if you know, 691 00:37:34,400 --> 00:37:37,080 Speaker 1: without friction or air resistance. For example, you can throw 692 00:37:37,120 --> 00:37:39,239 Speaker 1: a ball up in the air and it lands back 693 00:37:39,280 --> 00:37:41,880 Speaker 1: in your hands. If you played a movie of that backwards, 694 00:37:41,920 --> 00:37:44,680 Speaker 1: it would look exactly the same again without air resistance, 695 00:37:44,680 --> 00:37:48,239 Speaker 1: because that increases entropy. Um. But entropy is the one 696 00:37:48,280 --> 00:37:50,520 Speaker 1: place where in the laws of physics there seems to 697 00:37:50,520 --> 00:37:53,680 Speaker 1: be a preference for things moving forwards. So it's often 698 00:37:53,719 --> 00:37:58,040 Speaker 1: claimed that entropy might be the reason time moves forwards, 699 00:37:58,440 --> 00:38:00,520 Speaker 1: and I think that's a bit of a step too far. 700 00:38:01,120 --> 00:38:04,920 Speaker 1: You know, we see that entropy increases as time moves forward, 701 00:38:05,000 --> 00:38:08,240 Speaker 1: so there's a connection between them. That doesn't mean necessarily 702 00:38:08,280 --> 00:38:11,320 Speaker 1: the time has to move forward. I mean, if time 703 00:38:11,360 --> 00:38:14,320 Speaker 1: moved backwards. It just means that maybe entropy would decrease, 704 00:38:14,520 --> 00:38:18,279 Speaker 1: right It um creates this connection between entropy and time. 705 00:38:18,280 --> 00:38:23,240 Speaker 1: It doesn't necessarily imply a direction, but some people wonder 706 00:38:23,560 --> 00:38:26,759 Speaker 1: what would happen when you reach a state of maximum entropy, 707 00:38:26,840 --> 00:38:30,239 Speaker 1: and maximum entropy would be as you say, everything progresses 708 00:38:30,280 --> 00:38:32,840 Speaker 1: forward and the universe so of spreads out and it 709 00:38:32,960 --> 00:38:37,120 Speaker 1: becomes maximumly even there's no like hot spots and cold spots, 710 00:38:37,160 --> 00:38:39,960 Speaker 1: because that allows you to rearrange the microscopic state as 711 00:38:40,000 --> 00:38:42,920 Speaker 1: many ways as possible, so the most freedom to rearrange 712 00:38:42,960 --> 00:38:46,719 Speaker 1: the microscopic state and so the most entropy. And in 713 00:38:46,760 --> 00:38:48,960 Speaker 1: that state, it's called the heat death of the universe 714 00:38:49,000 --> 00:38:51,160 Speaker 1: because you have no hot spots and no cold spots, 715 00:38:51,360 --> 00:38:54,440 Speaker 1: so no way for like energy to flow. Nobody do anything. 716 00:38:54,880 --> 00:38:57,160 Speaker 1: The way that you operate as a human being is 717 00:38:57,160 --> 00:39:00,160 Speaker 1: through energy flows, and the way that computation happens this 718 00:39:00,239 --> 00:39:03,680 Speaker 1: through energy transfers, and so you can't really do anything 719 00:39:03,719 --> 00:39:06,880 Speaker 1: if there's no energy ingredients. So that's why it's referred 720 00:39:06,880 --> 00:39:10,120 Speaker 1: to as the heat death of the universe. And people 721 00:39:10,160 --> 00:39:13,280 Speaker 1: who think of that time is deeply connected to entropy 722 00:39:13,320 --> 00:39:17,640 Speaker 1: wonder if when entropy reaches its maximum point, if time 723 00:39:17,800 --> 00:39:22,000 Speaker 1: then somehow stops, or maybe time stops and then turns around, 724 00:39:22,040 --> 00:39:25,680 Speaker 1: and entropy starts to decrease like a bounce in time. 725 00:39:26,400 --> 00:39:29,000 Speaker 1: And nobody knows the answer to these questions. Nobody's gonna 726 00:39:29,000 --> 00:39:32,040 Speaker 1: be around to know the answer to these questions, even 727 00:39:32,040 --> 00:39:34,960 Speaker 1: if you're optimistic about the length of human civilization. But 728 00:39:35,000 --> 00:39:36,960 Speaker 1: they're really fun to think about because they make you 729 00:39:37,000 --> 00:39:39,600 Speaker 1: think about what time is and you know, and how 730 00:39:39,640 --> 00:39:43,600 Speaker 1: it relates to the whole universe. Well, though, on the 731 00:39:43,719 --> 00:39:46,719 Speaker 1: question of nobody being around this this may also be 732 00:39:46,760 --> 00:39:49,239 Speaker 1: a tangent. But this makes me wonder do you have 733 00:39:49,320 --> 00:39:53,000 Speaker 1: opinions on the alleged Boltzman brain problem. I know we 734 00:39:53,080 --> 00:39:55,080 Speaker 1: talked about this on an episode a few years back, 735 00:39:55,160 --> 00:39:58,200 Speaker 1: and um so maybe kind of fuzzy on the details, 736 00:39:58,239 --> 00:40:01,480 Speaker 1: but if I recall, it has been used to argue 737 00:40:01,560 --> 00:40:06,440 Speaker 1: against some types of future eternity ees. But basically the 738 00:40:06,760 --> 00:40:10,200 Speaker 1: the argument is, if the universe were to go on 739 00:40:10,400 --> 00:40:14,759 Speaker 1: existing literally forever, with certain types of properties in play, 740 00:40:14,840 --> 00:40:19,440 Speaker 1: eventually people whose brains randomly formed from fluctuations in space 741 00:40:19,480 --> 00:40:23,200 Speaker 1: would outnumber people who exist through biological evolution on a 742 00:40:23,239 --> 00:40:25,880 Speaker 1: rocky planet, and thus we would expect to be those 743 00:40:25,920 --> 00:40:30,719 Speaker 1: brains instead of these biological brains. Is that roughly right? Yeah. 744 00:40:31,000 --> 00:40:35,160 Speaker 1: Essentially it's arguing that if the universe reaches heat death 745 00:40:35,840 --> 00:40:39,320 Speaker 1: and then goes on forever, that most of the time 746 00:40:39,360 --> 00:40:41,880 Speaker 1: in the universe is in during heat death, right, that 747 00:40:42,239 --> 00:40:46,000 Speaker 1: really basically randomly sampled moment in universe should be when 748 00:40:46,000 --> 00:40:49,000 Speaker 1: the universe is spread out and boring and gray. So 749 00:40:49,080 --> 00:40:50,880 Speaker 1: then Boltman said, well, what if you just had a 750 00:40:50,960 --> 00:40:53,640 Speaker 1: quantum fluctuation while aims before quantum mechanics, but what if 751 00:40:53,640 --> 00:40:56,000 Speaker 1: you had a random fluctuation? Because you know, the law 752 00:40:56,040 --> 00:41:00,400 Speaker 1: of entropy statistical it's not exact, allows for fluctuations. And 753 00:41:00,440 --> 00:41:02,800 Speaker 1: so he said, well, what's the chances of the whole 754 00:41:02,960 --> 00:41:07,279 Speaker 1: universe then being like a fluctuation in some vast or 755 00:41:07,400 --> 00:41:11,920 Speaker 1: heat dead universe that already has existed for unknown millions 756 00:41:11,920 --> 00:41:14,400 Speaker 1: of years. So he was trying to fluctuate an entire 757 00:41:14,600 --> 00:41:18,800 Speaker 1: universe out of basically nothing. And so as a counterpoint, 758 00:41:18,840 --> 00:41:21,520 Speaker 1: people are like, well, you know, there are smaller but 759 00:41:21,680 --> 00:41:25,320 Speaker 1: more ridiculous things that you could fluctuate out of the universe, 760 00:41:25,360 --> 00:41:28,680 Speaker 1: like a galaxy or even just like one brain. And 761 00:41:28,719 --> 00:41:31,319 Speaker 1: so at the point was made actually to criticize those 762 00:41:31,400 --> 00:41:36,160 Speaker 1: kinds of cosmological models, because if your cosmological model seems 763 00:41:36,239 --> 00:41:40,200 Speaker 1: less likely than you know, brains forming spontaneously in space 764 00:41:40,320 --> 00:41:44,640 Speaker 1: and thinking that they're people, then it seems pretty unlikely. Um. 765 00:41:44,680 --> 00:41:46,800 Speaker 1: And so I don't think anybody really takes it seriously. 766 00:41:46,920 --> 00:41:49,360 Speaker 1: Is like a theory of the universe. It's sort of 767 00:41:49,400 --> 00:41:52,640 Speaker 1: just more like a mental exercise to wonder, like, how 768 00:41:52,719 --> 00:41:56,040 Speaker 1: likely is your theory of the universe? Um, you know, 769 00:41:56,160 --> 00:41:59,680 Speaker 1: is it less likely than this absurd scenario. So there's 770 00:41:59,719 --> 00:42:02,240 Speaker 1: another thing you bring up in your chapter. Will time 771 00:42:02,239 --> 00:42:05,880 Speaker 1: ever stopped? Is an idea I was instantly captivated by, 772 00:42:06,440 --> 00:42:11,080 Speaker 1: which is you point out that technically, um, time could 773 00:42:11,080 --> 00:42:14,640 Speaker 1: be stopping and restarting all the time, frequently without us 774 00:42:14,640 --> 00:42:17,520 Speaker 1: ever realizing it, because how would we know, right, Like, 775 00:42:17,560 --> 00:42:20,600 Speaker 1: our consciousness, our experience of the world is through time, 776 00:42:21,040 --> 00:42:24,320 Speaker 1: So if time were to stop, uh and then restart, 777 00:42:24,560 --> 00:42:27,080 Speaker 1: that might just be invisible to us. So you know, 778 00:42:27,120 --> 00:42:31,160 Speaker 1: maybe there are just uh, these huge gaps in our life. Though. 779 00:42:31,280 --> 00:42:35,520 Speaker 1: That makes me wonder if time we're stopping, would it 780 00:42:35,520 --> 00:42:38,919 Speaker 1: be possible to measure how long it stopped for? Oh, 781 00:42:39,040 --> 00:42:43,200 Speaker 1: that's really interesting. You know, this sort of presupposes some 782 00:42:43,280 --> 00:42:47,680 Speaker 1: sort of like meta time, some you know, other rules 783 00:42:47,840 --> 00:42:52,600 Speaker 1: of the universe that's controlling our time. And because time 784 00:42:52,760 --> 00:42:57,920 Speaker 1: itself controls how our universe changes, then strictly speaking, if 785 00:42:57,960 --> 00:43:00,960 Speaker 1: time does pause you know, core to this meta time 786 00:43:01,160 --> 00:43:03,840 Speaker 1: and then pick up again, nothing should change because that 787 00:43:03,840 --> 00:43:08,120 Speaker 1: would require our time to tick forward. Like no particles 788 00:43:08,120 --> 00:43:12,080 Speaker 1: can move, no galaxies, no space can be created. You know, 789 00:43:12,160 --> 00:43:15,840 Speaker 1: no expansion can happen without time our time ticking forward, 790 00:43:16,440 --> 00:43:18,680 Speaker 1: and that means that there's nothing in our universe that 791 00:43:18,760 --> 00:43:21,440 Speaker 1: should change if time doesn't take forward, which means that 792 00:43:21,480 --> 00:43:24,120 Speaker 1: there should be no way to tell. So it could 793 00:43:24,120 --> 00:43:27,640 Speaker 1: be like a near infinite amount of time between every 794 00:43:27,680 --> 00:43:30,920 Speaker 1: tick of our universe could be passing in sort of 795 00:43:30,920 --> 00:43:33,279 Speaker 1: like the meta universe. I think the easiest way to 796 00:43:33,320 --> 00:43:37,080 Speaker 1: imagine this is in the simulation hypothesis, the idea that 797 00:43:37,080 --> 00:43:40,440 Speaker 1: the universe is like a computer program running on some 798 00:43:40,600 --> 00:43:44,480 Speaker 1: mega computer. And you know, if the aliens or super 799 00:43:44,480 --> 00:43:47,799 Speaker 1: beings running that simulation pause the simulation to go to 800 00:43:47,840 --> 00:43:51,239 Speaker 1: the bathroom and come back, then we don't know that 801 00:43:51,280 --> 00:43:53,319 Speaker 1: they've paused it. Right. It's just like the characters in 802 00:43:53,360 --> 00:43:56,239 Speaker 1: your video game. They're not like, hey, buddy, that was 803 00:43:56,280 --> 00:43:59,360 Speaker 1: a long number two. You know what you're doing everything okay? 804 00:43:59,440 --> 00:44:01,799 Speaker 1: When you come, they have no idea, and to them, 805 00:44:01,920 --> 00:44:04,480 Speaker 1: you know, the experience is completely smooth. So I think, No, 806 00:44:04,600 --> 00:44:07,480 Speaker 1: there's no way to know how long time has been 807 00:44:07,480 --> 00:44:10,720 Speaker 1: paused for if it does get paused. I always wondered 808 00:44:10,760 --> 00:44:14,200 Speaker 1: with that hypothesis, would we notice if the resolution on 809 00:44:14,239 --> 00:44:19,759 Speaker 1: our simulation was downgraded, you mean, if they lost their 810 00:44:19,800 --> 00:44:22,239 Speaker 1: funding and had to had to go to a more 811 00:44:22,280 --> 00:44:27,000 Speaker 1: course resolution decreased render distance. Yeah, I don't know. Sometimes 812 00:44:27,000 --> 00:44:30,840 Speaker 1: it does feel like the resolution decreases or increases in 813 00:44:30,880 --> 00:44:34,120 Speaker 1: depending on what's going on. I'm gonna blame my failing 814 00:44:34,200 --> 00:44:36,600 Speaker 1: memory for that, Like, you know what the aliens have 815 00:44:36,719 --> 00:44:39,439 Speaker 1: just been like cleaning up the cash, and that's why 816 00:44:39,440 --> 00:44:42,000 Speaker 1: I can't remember, you know, what happened last week, or 817 00:44:42,000 --> 00:44:44,240 Speaker 1: when I agreed to clean to the garage or whatever. 818 00:44:45,320 --> 00:44:47,359 Speaker 1: But there are ways that we do think we might 819 00:44:47,400 --> 00:44:50,440 Speaker 1: be able to probe the resolution of the simulation of 820 00:44:50,480 --> 00:44:53,200 Speaker 1: the universe under the assumption that we live in that 821 00:44:53,239 --> 00:44:57,200 Speaker 1: crazy scenario. Because these simulations the way we do them, 822 00:44:57,200 --> 00:44:59,240 Speaker 1: at least as we tend to like divide the universe 823 00:44:59,280 --> 00:45:03,759 Speaker 1: into huge cubes and stimulate each cube separately, assuming that 824 00:45:03,800 --> 00:45:07,160 Speaker 1: like the interactions between cubes are pretty small, which works 825 00:45:07,200 --> 00:45:09,160 Speaker 1: pretty well. You know, if you're in your if you're 826 00:45:09,320 --> 00:45:12,000 Speaker 1: simulating like a single galaxy at the time, because mostly 827 00:45:12,040 --> 00:45:14,640 Speaker 1: you're dominated by what's going on inside the galaxy and 828 00:45:14,680 --> 00:45:18,040 Speaker 1: not stuff from other galaxies. But we have these particles, 829 00:45:18,120 --> 00:45:21,839 Speaker 1: these crazy high energy particles that whizz through space at 830 00:45:21,920 --> 00:45:25,520 Speaker 1: velocities nobody's ever seen before, or energies nobody's ever seen before, 831 00:45:26,040 --> 00:45:28,719 Speaker 1: much much higher energy than anything like created by our 832 00:45:28,719 --> 00:45:32,440 Speaker 1: particle accelerators. And they might be like tripping up that 833 00:45:32,480 --> 00:45:36,799 Speaker 1: simulation because they skip through several of these simulation pixels 834 00:45:36,840 --> 00:45:39,879 Speaker 1: faster than anything you should expect. And you know, there 835 00:45:39,880 --> 00:45:42,200 Speaker 1: are some things about those particles we see out there 836 00:45:42,200 --> 00:45:45,200 Speaker 1: in space that we don't understand, and so that opens 837 00:45:45,200 --> 00:45:48,320 Speaker 1: the door to like maybe you could explain those particles 838 00:45:48,680 --> 00:45:52,720 Speaker 1: as being like a glitch in the simulation. Now, speaking 839 00:45:52,719 --> 00:45:57,200 Speaker 1: of simulations and going back to time travel, does anyone 840 00:45:57,200 --> 00:46:01,440 Speaker 1: out there like make any out of an argument for 841 00:46:01,920 --> 00:46:05,319 Speaker 1: time travel into the past by saying, well, if we 842 00:46:05,400 --> 00:46:08,680 Speaker 1: are living within a simulation, then time travel into the 843 00:46:08,719 --> 00:46:11,759 Speaker 1: past and the ability to change the past would be 844 00:46:11,800 --> 00:46:14,920 Speaker 1: possible within the confines of that simulation. Yeah, you know, 845 00:46:15,120 --> 00:46:17,520 Speaker 1: if you're living in a simulation, then the rules are 846 00:46:17,560 --> 00:46:21,640 Speaker 1: essentially arbitrary, and then yeah, you could wind time backwards. 847 00:46:22,160 --> 00:46:24,040 Speaker 1: I think this goes to the heart of, like, I think, 848 00:46:24,040 --> 00:46:27,680 Speaker 1: a basic confusion about time travel, because people imagine, like 849 00:46:27,760 --> 00:46:30,160 Speaker 1: you get in a time machine and you and the 850 00:46:30,200 --> 00:46:32,839 Speaker 1: time machine does something to you, and then you end 851 00:46:32,880 --> 00:46:35,000 Speaker 1: up back in the past. I don't really see how 852 00:46:35,040 --> 00:46:37,959 Speaker 1: that could possibly work. What you really want in time 853 00:46:37,960 --> 00:46:41,279 Speaker 1: travel is for the whole universe to travel back in 854 00:46:41,320 --> 00:46:43,879 Speaker 1: the past and for you to not. So you gotta 855 00:46:43,920 --> 00:46:45,560 Speaker 1: like get in the time machine and it's got to 856 00:46:45,600 --> 00:46:49,160 Speaker 1: like rewind the clocks of the rest of the universe, right, 857 00:46:49,200 --> 00:46:51,760 Speaker 1: You don't want to be like, Okay, it's still today, 858 00:46:51,840 --> 00:46:53,880 Speaker 1: but now I'm ten years younger. I mean maybe some 859 00:46:53,920 --> 00:46:56,560 Speaker 1: people want that. That's a whole different thing to look for. 860 00:46:57,040 --> 00:46:59,520 Speaker 1: If you want to like unspill your coffee, but you 861 00:46:59,520 --> 00:47:02,200 Speaker 1: still want like the ideas you want to remember having 862 00:47:02,239 --> 00:47:04,640 Speaker 1: spilled it on yourself so you cannot just repeat it. 863 00:47:04,840 --> 00:47:06,520 Speaker 1: Then you need to rewind the whole rest of the 864 00:47:06,640 --> 00:47:10,279 Speaker 1: universe somehow, which seems like a much bigger job that. Yeah, 865 00:47:10,320 --> 00:47:12,440 Speaker 1: that's a great point. Yeah, that so the time machine 866 00:47:12,480 --> 00:47:14,880 Speaker 1: would have to change the universe, not you. Yeah, I 867 00:47:15,000 --> 00:47:17,040 Speaker 1: never thought of it that way. Yeah. And a lot 868 00:47:17,080 --> 00:47:19,120 Speaker 1: of our listeners right in when we talk about time 869 00:47:19,160 --> 00:47:21,719 Speaker 1: travel and raise a similar point and a criticism of 870 00:47:21,719 --> 00:47:25,080 Speaker 1: science fiction levels, which is that, you know, if you 871 00:47:25,160 --> 00:47:27,560 Speaker 1: do go back in time somehow, how do you know 872 00:47:27,600 --> 00:47:30,480 Speaker 1: where you're going to be? You know, because the Earth 873 00:47:30,640 --> 00:47:33,960 Speaker 1: and the Sun and the Milky Way they're all moving, Um, 874 00:47:34,000 --> 00:47:36,000 Speaker 1: so how do you know where you're going to end up? 875 00:47:36,120 --> 00:47:39,239 Speaker 1: And it's a fun question. Um though, I think if 876 00:47:39,239 --> 00:47:41,880 Speaker 1: you're gonna posit like, okay, you can travel through time, 877 00:47:41,960 --> 00:47:45,160 Speaker 1: then ostensibly probably you can travel travel through space time, 878 00:47:45,200 --> 00:47:48,640 Speaker 1: so you can appear wherever you want. But the problem is, like, 879 00:47:48,760 --> 00:47:52,719 Speaker 1: as I'm not even really necessarily well defined, because what 880 00:47:52,760 --> 00:47:55,040 Speaker 1: does it mean to be here at a point in 881 00:47:55,080 --> 00:47:56,960 Speaker 1: space or there at a point in space right now? 882 00:47:57,160 --> 00:47:59,799 Speaker 1: This point in space? Now where is that point in 883 00:47:59,840 --> 00:48:03,360 Speaker 1: the future, Because there is no like marker to space. 884 00:48:03,400 --> 00:48:06,160 Speaker 1: Space is all relative. It's not absolutely you can't like 885 00:48:06,520 --> 00:48:08,520 Speaker 1: grasp this point of space and give it a name 886 00:48:08,560 --> 00:48:11,000 Speaker 1: and say where does this bit go? There's only stuff 887 00:48:11,040 --> 00:48:14,439 Speaker 1: moving through space relative to each other, so it turns 888 00:48:14,440 --> 00:48:17,840 Speaker 1: out that's not even really well to find, Like, where 889 00:48:18,040 --> 00:48:20,600 Speaker 1: was the Earth, you know, a million years ago in 890 00:48:20,680 --> 00:48:24,040 Speaker 1: our space doesn't actually have a meaning? That is when 891 00:48:24,040 --> 00:48:36,160 Speaker 1: I had thought of before that always seemed an insurmountable problem. Yeah, 892 00:48:36,640 --> 00:48:38,520 Speaker 1: but this, this actually reminds me of another thing I 893 00:48:38,520 --> 00:48:43,319 Speaker 1: wanted to talk about briefly, which is relating time to 894 00:48:44,120 --> 00:48:47,160 Speaker 1: the history of the universe and the Big Bang, a 895 00:48:47,280 --> 00:48:50,920 Speaker 1: thing people often ask, and I know there are theories 896 00:48:50,920 --> 00:48:55,480 Speaker 1: to address this is is what happened before the Big Bang, 897 00:48:56,440 --> 00:48:58,640 Speaker 1: But if you have an understanding that, you know, you 898 00:48:58,680 --> 00:49:01,040 Speaker 1: have a singularity at the origin of the Big Bang, 899 00:49:01,120 --> 00:49:04,080 Speaker 1: that was the beginning of time itself as we know it. 900 00:49:04,640 --> 00:49:07,560 Speaker 1: What are physicists talking about exactly when they try to 901 00:49:07,680 --> 00:49:12,120 Speaker 1: envision causes leading to the first instant of the Big Bang? 902 00:49:12,680 --> 00:49:16,399 Speaker 1: Mostly they're trying to avoid that singularity because that singularity 903 00:49:16,440 --> 00:49:19,239 Speaker 1: is a problem. You know, we don't see things like 904 00:49:19,280 --> 00:49:22,759 Speaker 1: singularities in the universe. We don't see infinities, we don't 905 00:49:22,760 --> 00:49:25,360 Speaker 1: see things with infinite density, we don't see things of 906 00:49:25,400 --> 00:49:28,520 Speaker 1: infinite size. I mean, maybe the universe is itself infinite, 907 00:49:28,840 --> 00:49:31,920 Speaker 1: but there's nothing that's like infinitely smooth or perfectly circular. 908 00:49:32,200 --> 00:49:35,160 Speaker 1: These are sort of abstractions in our mind, and so 909 00:49:35,480 --> 00:49:38,000 Speaker 1: most physicists who are working on the very early universe 910 00:49:38,239 --> 00:49:41,520 Speaker 1: are trying to avoid that singularity because, as I said earlier, 911 00:49:41,600 --> 00:49:44,319 Speaker 1: general relativity breaks down. That's what it means like, if 912 00:49:44,360 --> 00:49:46,960 Speaker 1: your theory predicts something infinite, it doesn't know how to 913 00:49:46,960 --> 00:49:50,600 Speaker 1: do any calculations beyond that. So instead of having like 914 00:49:50,760 --> 00:49:53,400 Speaker 1: a moment of singularity, which is sort of like the 915 00:49:53,520 --> 00:49:58,600 Speaker 1: naive general relativistic prediction of increasing density, instead they're going 916 00:49:58,640 --> 00:50:01,160 Speaker 1: back and saying, well, maybe big Bang was just like 917 00:50:01,200 --> 00:50:06,319 Speaker 1: a rapid expansion of space from a previously dense kind 918 00:50:06,360 --> 00:50:09,080 Speaker 1: of universe that we don't understand at all. So the 919 00:50:09,120 --> 00:50:12,040 Speaker 1: basic sketches, like you have some kind of weird state 920 00:50:12,280 --> 00:50:15,800 Speaker 1: the universe is filled with like inflotons, some particle we 921 00:50:15,800 --> 00:50:18,239 Speaker 1: don't know if it existed, but maybe it did. And 922 00:50:18,239 --> 00:50:22,040 Speaker 1: then those inflotons they are causing me rapid expansion of 923 00:50:22,080 --> 00:50:26,000 Speaker 1: space and decay then into normal matter. So that so 924 00:50:26,080 --> 00:50:28,640 Speaker 1: now the Big Bang is that moment when the in 925 00:50:28,719 --> 00:50:32,640 Speaker 1: photons are expanding and then decay into like our universe. 926 00:50:32,680 --> 00:50:35,120 Speaker 1: That's how our universe is sort of created out of 927 00:50:35,160 --> 00:50:38,560 Speaker 1: these in photons, and that avoids this moment of singularity. 928 00:50:38,600 --> 00:50:41,200 Speaker 1: It's never like a moment when the universe is infinitely dense. 929 00:50:41,719 --> 00:50:44,680 Speaker 1: But you know, again, this is very speculative stuff. We 930 00:50:44,760 --> 00:50:49,440 Speaker 1: think inflation happened this crazy expansion in the very beginning, um, 931 00:50:49,480 --> 00:50:52,040 Speaker 1: and this is like a way to avoid having to 932 00:50:52,320 --> 00:50:55,759 Speaker 1: put before that this dot, this singularity that breaks all 933 00:50:55,800 --> 00:50:58,560 Speaker 1: of the mathematics, instead of replacing it with like some 934 00:50:58,640 --> 00:51:01,080 Speaker 1: other weird kind of sub So we don't even really 935 00:51:01,120 --> 00:51:03,719 Speaker 1: know what it's like or what it's about. Um, we're 936 00:51:03,760 --> 00:51:06,719 Speaker 1: just really beginning to know how to ask questions about it. 937 00:51:07,400 --> 00:51:10,560 Speaker 1: And you know, that suggests a really interesting question, which 938 00:51:10,600 --> 00:51:13,360 Speaker 1: is like, if there is something before the Big Bang, 939 00:51:13,480 --> 00:51:16,120 Speaker 1: what was it? And was there something before that? It 940 00:51:16,200 --> 00:51:19,160 Speaker 1: seems like, in one hand, super frustrating because you're just 941 00:51:19,239 --> 00:51:21,839 Speaker 1: kicking the can down the road, Like, all right, so 942 00:51:22,120 --> 00:51:24,560 Speaker 1: the early universe was this expansion, and before that came 943 00:51:24,600 --> 00:51:26,799 Speaker 1: something which caused the expansion, and before that came something 944 00:51:26,840 --> 00:51:29,680 Speaker 1: which caused that, which caused the expansion. But is there 945 00:51:29,880 --> 00:51:34,080 Speaker 1: in the end something original which caused it. We don't know. 946 00:51:34,160 --> 00:51:37,200 Speaker 1: And there's two possibilities. One is that we just keep 947 00:51:37,239 --> 00:51:39,920 Speaker 1: digging forever and dig further and further and further and 948 00:51:39,920 --> 00:51:43,319 Speaker 1: further back and never get to anything which seems like 949 00:51:43,640 --> 00:51:46,480 Speaker 1: could have caused itself. Or it could be that we 950 00:51:46,480 --> 00:51:48,640 Speaker 1: get to some state where we're like, hmm, this makes 951 00:51:48,680 --> 00:51:51,239 Speaker 1: sense to have to be a beginning. It's like it's 952 00:51:51,239 --> 00:51:54,719 Speaker 1: sort of the only way things could have happened to me. 953 00:51:54,960 --> 00:51:56,960 Speaker 1: It's it's hard to grapple with this idea, so it's 954 00:51:57,000 --> 00:51:59,120 Speaker 1: easier to think about it sort of in a parallel way, 955 00:51:59,120 --> 00:52:02,120 Speaker 1: which is like, what is the smallest thing in the universe. 956 00:52:02,600 --> 00:52:05,680 Speaker 1: We don't know if as we tear apart, particles will 957 00:52:05,760 --> 00:52:07,840 Speaker 1: keep finding things that are smaller and smaller and smaller 958 00:52:07,840 --> 00:52:10,239 Speaker 1: and smaller, or if eventually we'll get to one where, like, 959 00:52:10,280 --> 00:52:12,840 Speaker 1: you know, what, this one it makes sense to be 960 00:52:12,880 --> 00:52:15,759 Speaker 1: a fundamental ingredient to the universe. We can just start 961 00:52:15,800 --> 00:52:18,000 Speaker 1: from here and build up. You know, maybe it's like 962 00:52:18,040 --> 00:52:20,760 Speaker 1: the smallest fundamental thing. It's at the plank length or something. 963 00:52:21,160 --> 00:52:22,799 Speaker 1: We don't know if we'll ever get there, or if 964 00:52:22,800 --> 00:52:24,840 Speaker 1: it will be self evident, or if there will be 965 00:52:24,920 --> 00:52:27,680 Speaker 1: always people who say, like, I don't know, I want 966 00:52:27,680 --> 00:52:30,120 Speaker 1: to dig deeper. In the same way, it might be 967 00:52:30,160 --> 00:52:32,919 Speaker 1: that we're doomed to keep digging deeper and deeper back 968 00:52:32,960 --> 00:52:35,719 Speaker 1: into the history of the universe, never finding out if 969 00:52:35,760 --> 00:52:38,799 Speaker 1: there was an original cause. All right, so, I think 970 00:52:38,840 --> 00:52:40,719 Speaker 1: we're probably getting close to the end of our time. 971 00:52:40,760 --> 00:52:42,960 Speaker 1: But I gotta come back to time travel before we do, 972 00:52:43,000 --> 00:52:46,040 Speaker 1: because I'm wondering what what do you think You mentioned 973 00:52:46,160 --> 00:52:49,960 Speaker 1: Stephen Hawkings party where the invitations were sent out after 974 00:52:50,000 --> 00:52:52,880 Speaker 1: it happened. But what is your personal favorite way to 975 00:52:52,960 --> 00:52:54,879 Speaker 1: hunt for a time traveler? What would you do if 976 00:52:54,880 --> 00:52:58,560 Speaker 1: you wanted to find evidence of people from the future. Wow, 977 00:52:58,680 --> 00:53:02,480 Speaker 1: I've I've never given that any thought about evidence for 978 00:53:02,560 --> 00:53:05,640 Speaker 1: people from the future. Um. I try to think about 979 00:53:05,760 --> 00:53:08,600 Speaker 1: what people would want to do, Like if I were 980 00:53:08,640 --> 00:53:12,920 Speaker 1: a time traveler, why would I come to one? Uh? 981 00:53:12,960 --> 00:53:16,120 Speaker 1: You know the obvious answers of like change history. Uh, 982 00:53:16,200 --> 00:53:17,879 Speaker 1: in which case, you know, I guess you can blame 983 00:53:17,880 --> 00:53:20,759 Speaker 1: those time travelers for you know, the reason things have 984 00:53:20,840 --> 00:53:23,640 Speaker 1: gone the way they are. Maybe there because time travelers 985 00:53:23,640 --> 00:53:26,560 Speaker 1: have come back and tweaked election results or you know, 986 00:53:26,680 --> 00:53:30,120 Speaker 1: or something like that. Um. So, I guess the best 987 00:53:30,160 --> 00:53:32,600 Speaker 1: way to find time travelers with then to be present 988 00:53:32,840 --> 00:53:37,160 Speaker 1: at critical hinge moments in history and look around for 989 00:53:37,239 --> 00:53:40,840 Speaker 1: suspicious behavior. I suppose I don't really know. That's a 990 00:53:40,880 --> 00:53:43,799 Speaker 1: great question. Yeah, I was thinking about all this in 991 00:53:43,960 --> 00:53:48,239 Speaker 1: terms of of ancient aliens as well, because both you 992 00:53:48,239 --> 00:53:50,040 Speaker 1: have you have people of course who obsess about the 993 00:53:50,080 --> 00:53:53,200 Speaker 1: idea of of aliens having visited during ancient times and 994 00:53:53,239 --> 00:53:55,400 Speaker 1: so forth, and and you also have I guess, a 995 00:53:55,480 --> 00:53:59,280 Speaker 1: more recent phenomenon of people looking back at old pictures 996 00:53:59,320 --> 00:54:02,320 Speaker 1: and painting and you know, playing this game of basically 997 00:54:02,360 --> 00:54:06,200 Speaker 1: misinterpreting um things and paintings and photos, like looking back 998 00:54:06,200 --> 00:54:07,960 Speaker 1: in an old picture and saying, oh, well, that person, 999 00:54:08,480 --> 00:54:11,200 Speaker 1: their their style of dress does not look archaic enough. 1000 00:54:11,640 --> 00:54:14,800 Speaker 1: They must be traveler, yeah, or just painting. She's holding 1001 00:54:14,840 --> 00:54:17,560 Speaker 1: something that looks like an iPhone. Obviously this is a 1002 00:54:17,680 --> 00:54:23,040 Speaker 1: renaissance painting of a time travel No. I think that 1003 00:54:23,160 --> 00:54:25,000 Speaker 1: just says a lot about us, you know, and who 1004 00:54:25,040 --> 00:54:27,880 Speaker 1: we are, you know, the same way that like photos 1005 00:54:27,960 --> 00:54:32,960 Speaker 1: of UFOs seem to be constantly grainy. As you know, 1006 00:54:33,120 --> 00:54:36,560 Speaker 1: imaging technology improves, it's always on the edge of the 1007 00:54:36,600 --> 00:54:38,959 Speaker 1: our ability to capture it. So I think it says 1008 00:54:38,960 --> 00:54:42,920 Speaker 1: something about our desire to discover weird things and reveal 1009 00:54:43,000 --> 00:54:46,080 Speaker 1: the truth, which I'm totally sympathetic to I also want 1010 00:54:46,160 --> 00:54:48,120 Speaker 1: to peel back a layer of the universe and wake 1011 00:54:48,200 --> 00:54:51,880 Speaker 1: up to its true nature. I remember Carl Sagan, and 1012 00:54:51,920 --> 00:54:54,040 Speaker 1: I forget which which book this was, but it was 1013 00:54:54,080 --> 00:54:55,719 Speaker 1: in one of the books where he talks a little 1014 00:54:55,719 --> 00:54:58,640 Speaker 1: bit about the idea of ancient aliens, and I remember 1015 00:54:58,760 --> 00:55:04,480 Speaker 1: him him basically outlining the sort of ancient account, the 1016 00:55:04,520 --> 00:55:07,879 Speaker 1: sort of myth that one might look to as as 1017 00:55:07,920 --> 00:55:12,480 Speaker 1: the sort of ancient astronaut account that could exist, have 1018 00:55:12,600 --> 00:55:15,279 Speaker 1: such things were possible? And I wonder if anyone's ever 1019 00:55:15,320 --> 00:55:17,480 Speaker 1: taken a similar approach to the concept of time travel, 1020 00:55:17,520 --> 00:55:19,799 Speaker 1: like like basically like boiling it down, saying, okay, if 1021 00:55:19,800 --> 00:55:24,160 Speaker 1: there is actually evidence, say in you know, the historical 1022 00:55:24,520 --> 00:55:28,120 Speaker 1: record all of people having traveled back in time, you know, well, 1023 00:55:28,160 --> 00:55:30,600 Speaker 1: what exactly would we be looking for? What exactly would 1024 00:55:30,600 --> 00:55:34,239 Speaker 1: they would they have been doing? Um and uh and 1025 00:55:34,239 --> 00:55:36,400 Speaker 1: and and how would and I guess it would come 1026 00:55:36,400 --> 00:55:38,520 Speaker 1: down to, like you'd have to imagine, like how truthful 1027 00:55:38,560 --> 00:55:39,960 Speaker 1: are they going to be? Are they just gonna lie 1028 00:55:39,960 --> 00:55:43,359 Speaker 1: about themselves being time travels? Because that's then you can 1029 00:55:43,400 --> 00:55:47,360 Speaker 1: basically point to any pivotal individual or any person in 1030 00:55:47,360 --> 00:55:50,839 Speaker 1: a pivotal period of time, right, Yeah, and would they 1031 00:55:50,880 --> 00:55:54,200 Speaker 1: even be humans? Right, Like we fantasize about going back 1032 00:55:54,200 --> 00:55:57,640 Speaker 1: to see the dinosaurs. So if now we're putting ourselves 1033 00:55:57,640 --> 00:56:00,279 Speaker 1: back in the past and imagining time travelers, we might 1034 00:56:00,320 --> 00:56:04,160 Speaker 1: have to imagine some like post human apocalyptic, newly intelligent 1035 00:56:04,239 --> 00:56:07,719 Speaker 1: species of you know, who knows what, penguins or or 1036 00:56:07,760 --> 00:56:11,960 Speaker 1: something coming back in time to investigate humans, you know, 1037 00:56:12,080 --> 00:56:16,200 Speaker 1: to understand what happened before the apocalypse or whatever. Um. 1038 00:56:16,239 --> 00:56:19,799 Speaker 1: But I think machines, machines. Most of the most of 1039 00:56:19,800 --> 00:56:22,920 Speaker 1: our space exploration is uncrewed probes. Now you would have 1040 00:56:22,960 --> 00:56:25,760 Speaker 1: to imagine the same would hold true for time. Yeah, 1041 00:56:25,960 --> 00:56:28,799 Speaker 1: that's probably true, or you know, after the machines have 1042 00:56:28,880 --> 00:56:31,239 Speaker 1: killed us all and they just have myths about those 1043 00:56:31,320 --> 00:56:34,880 Speaker 1: weird meat creatures that used to uh roam the earth 1044 00:56:35,080 --> 00:56:38,280 Speaker 1: or something. Um. That's fun, but it's fundamentally is limited 1045 00:56:38,320 --> 00:56:41,280 Speaker 1: by our imagination. It's the same problem with trying to 1046 00:56:41,320 --> 00:56:44,479 Speaker 1: look for aliens. We look for aliens in the way 1047 00:56:44,480 --> 00:56:47,960 Speaker 1: we expect to see them, although we're pretty sure that 1048 00:56:48,040 --> 00:56:51,759 Speaker 1: if aliens exist, they're not anything that we expected. So 1049 00:56:51,800 --> 00:56:53,680 Speaker 1: we need to like push really hard on all the 1050 00:56:53,719 --> 00:56:56,480 Speaker 1: boundaries of our imagination. To make sure we're looking for 1051 00:56:56,520 --> 00:56:59,359 Speaker 1: aliens as broadly as possible so we don't miss them. 1052 00:56:59,640 --> 00:57:01,399 Speaker 1: We don't just like come by, We're like, oh, that's 1053 00:57:01,400 --> 00:57:04,520 Speaker 1: not aliens. So it's the same problem with imagining future 1054 00:57:04,560 --> 00:57:07,239 Speaker 1: time travelers, like who these these people or things or 1055 00:57:07,360 --> 00:57:10,759 Speaker 1: entities are are well beyond I think even our most 1056 00:57:10,800 --> 00:57:14,960 Speaker 1: creative science fiction UM writers, well, like you said, like 1057 00:57:15,000 --> 00:57:18,240 Speaker 1: what's interesting? What would be interesting about to someone from 1058 00:57:18,240 --> 00:57:20,880 Speaker 1: the future, And we instantly think, too, oh, well, the 1059 00:57:21,280 --> 00:57:26,040 Speaker 1: you know, the coronavirus or something going on in you know, geopolitics, 1060 00:57:26,160 --> 00:57:29,680 Speaker 1: or even in the environment. But it could be something 1061 00:57:29,760 --> 00:57:32,360 Speaker 1: entirely different. It could be you know, the very beginning 1062 00:57:32,360 --> 00:57:35,680 Speaker 1: of something um that doesn't matter at all today, right, 1063 00:57:35,720 --> 00:57:41,640 Speaker 1: but but matters say in exactly which we could never 1064 00:57:41,720 --> 00:57:44,680 Speaker 1: possibly imagine. I mean, think about people a thousand years 1065 00:57:44,720 --> 00:57:47,560 Speaker 1: ago trying to anticipate was important to us today. We 1066 00:57:47,560 --> 00:57:49,760 Speaker 1: couldn't even do that from twenty years ago, not to 1067 00:57:49,800 --> 00:57:53,000 Speaker 1: mention a thousand Okay, last question, Daniel, what's your favorite 1068 00:57:53,000 --> 00:57:55,960 Speaker 1: time travel movie? Oh, my favorite time travel movie has 1069 00:57:55,960 --> 00:57:59,720 Speaker 1: to be Primer So I think that most clearly sets 1070 00:57:59,720 --> 00:58:03,280 Speaker 1: out rules, rules that make sense, and then follows those 1071 00:58:03,920 --> 00:58:10,480 Speaker 1: really carefully with lots of fascinating and unexpected results. Good answers. Yeah, 1072 00:58:10,720 --> 00:58:13,200 Speaker 1: that's a good one. I often gravitate towards the ones 1073 00:58:13,240 --> 00:58:17,080 Speaker 1: that have really goofy time travel rules, but they but 1074 00:58:17,120 --> 00:58:20,760 Speaker 1: if they still stick to those rules, then I tend 1075 00:58:20,760 --> 00:58:25,400 Speaker 1: to forgive them. They're always boundary cases, though they're always cased. 1076 00:58:25,400 --> 00:58:26,840 Speaker 1: They were like I'm not sure what would happen in 1077 00:58:26,840 --> 00:58:30,040 Speaker 1: this scenario or that scenario. So I like Primary because 1078 00:58:30,520 --> 00:58:33,400 Speaker 1: it has really clear crisp rules and those and it 1079 00:58:33,440 --> 00:58:35,880 Speaker 1: has cost. You can't just like pop back in time. 1080 00:58:36,200 --> 00:58:40,000 Speaker 1: You have to like spend time going backwards um, which 1081 00:58:40,040 --> 00:58:42,400 Speaker 1: has really interesting consequences. So I found it to be 1082 00:58:42,400 --> 00:58:46,200 Speaker 1: really creative totally. All right, Well, thanks so much for 1083 00:58:46,240 --> 00:58:48,120 Speaker 1: joining us today, Daniel. This has been a lot of fun. 1084 00:58:48,640 --> 00:58:50,640 Speaker 1: Thank you very much. Always a pleasure to talk to 1085 00:58:50,640 --> 00:58:55,600 Speaker 1: you guys. All right, well, thanks once more to Daniel 1086 00:58:55,600 --> 00:58:59,960 Speaker 1: Watson for jumping on the old podcast machine and lead 1087 00:59:00,040 --> 00:59:03,840 Speaker 1: us uh Pokemon Produm with various questions about time travel 1088 00:59:03,960 --> 00:59:06,800 Speaker 1: and wormholes and what have you. Yeah, if you want 1089 00:59:06,840 --> 00:59:10,040 Speaker 1: to learn more, so if you're not subscribed to Daniel 1090 00:59:10,080 --> 00:59:12,840 Speaker 1: and Jorge Explain the Universe, you can find that wherever 1091 00:59:12,880 --> 00:59:14,600 Speaker 1: you get your podcast, but you can also go to 1092 00:59:14,840 --> 00:59:19,680 Speaker 1: www dot Daniel and Jorge dot com. And you can 1093 00:59:19,720 --> 00:59:22,320 Speaker 1: also find the website for their new book. Again. The 1094 00:59:22,360 --> 00:59:25,880 Speaker 1: book is called Frequently Asked Questions about the Universe, and 1095 00:59:26,080 --> 00:59:29,240 Speaker 1: the website for that is www dot Universe f a 1096 00:59:29,320 --> 00:59:31,760 Speaker 1: Q dot com. And if you'd like to check out 1097 00:59:31,760 --> 00:59:33,720 Speaker 1: other episodes of Stuff to Blow Your Mind, well you 1098 00:59:33,760 --> 00:59:36,480 Speaker 1: can find our show wherever you get your podcasts. Just 1099 00:59:36,560 --> 00:59:38,960 Speaker 1: look for the Stuff to Blow Your Mind podcast feed. 1100 00:59:39,560 --> 00:59:43,680 Speaker 1: We run multiple episodes per week, with core episodes dealing 1101 00:59:43,680 --> 00:59:48,120 Speaker 1: with science and culture on Tuesdays and Thursdays. On Monday's 1102 00:59:48,160 --> 00:59:50,160 Speaker 1: we do listener mail, on Wednesday's we do a short 1103 00:59:50,200 --> 00:59:54,160 Speaker 1: form artifact titled the Artifact, and on Friday's we do 1104 00:59:54,240 --> 00:59:56,760 Speaker 1: something called Weird House Cinema, which is our time to 1105 00:59:56,840 --> 01:00:01,360 Speaker 1: set aside most serious matters and just discuss aus strange film. So, 1106 01:00:01,400 --> 01:00:03,680 Speaker 1: of course thanks again to Daniel for joining us today, 1107 01:00:03,720 --> 01:00:06,520 Speaker 1: and as always, a big thank you to our excellent 1108 01:00:06,600 --> 01:00:09,680 Speaker 1: audio producer Seth Nicholas Johnson. If you would like to 1109 01:00:09,720 --> 01:00:12,720 Speaker 1: get in touch with us with feedback on this episode 1110 01:00:12,800 --> 01:00:15,160 Speaker 1: or any other, to suggest topic for the future, or 1111 01:00:15,240 --> 01:00:18,080 Speaker 1: just to say hi, you can email us at contact 1112 01:00:18,200 --> 01:00:28,440 Speaker 1: at stuff to Blow Your Mind dot com. Stuff to 1113 01:00:28,440 --> 01:00:30,960 Speaker 1: Blow Your Mind is production of I heart Radio. For 1114 01:00:31,080 --> 01:00:33,240 Speaker 1: more podcasts for my heart Radio, visit the i heart 1115 01:00:33,320 --> 01:00:36,040 Speaker 1: Radio app, Apple Podcasts, or wherever you're listening to your 1116 01:00:36,080 --> 01:00:45,280 Speaker 1: favorite shows.