1 00:00:08,600 --> 00:00:12,119 Speaker 1: Hey, Alry, when did you move to California? It was 2 00:00:12,320 --> 00:00:15,040 Speaker 1: a long time ago. So was it like before or 3 00:00:15,160 --> 00:00:17,759 Speaker 1: after the last ice age? How do you think, I 4 00:00:17,800 --> 00:00:20,759 Speaker 1: am Daniel? Or do you mean like the time that 5 00:00:20,840 --> 00:00:23,560 Speaker 1: the temperature drop below sixty degrees here in Los Angeles? 6 00:00:23,800 --> 00:00:26,480 Speaker 1: We call that the California ice Age? Well, I mean 7 00:00:26,480 --> 00:00:29,000 Speaker 1: that begs the question, did you move to California for 8 00:00:29,080 --> 00:00:32,800 Speaker 1: the weather? Kind of? I mean I moved here for 9 00:00:32,880 --> 00:00:35,280 Speaker 1: grad school and I actually had to choose between Stanford 10 00:00:35,280 --> 00:00:37,800 Speaker 1: and Berkeley. Is there much of a weather difference on 11 00:00:37,840 --> 00:00:40,760 Speaker 1: the other side of the Bay. There is, Actually there's 12 00:00:40,800 --> 00:00:42,560 Speaker 1: a big difference. At least on the day that I 13 00:00:42,640 --> 00:00:45,120 Speaker 1: made the decision, it was much sunnier at Stanford. I see. 14 00:00:45,120 --> 00:00:47,960 Speaker 1: So you're saying Berkeley is cooler. I'm saying Berkeley is 15 00:00:48,200 --> 00:00:51,919 Speaker 1: ice here and more frigid. Everybody who went to Stanford 16 00:00:52,000 --> 00:01:10,720 Speaker 1: is definitely hot. It's hot place. Hi am Orhamedy cartoonist 17 00:01:10,760 --> 00:01:13,440 Speaker 1: and the creator of PhD comics. Hi, I'm Daniel. I'm 18 00:01:13,480 --> 00:01:16,440 Speaker 1: a particle physicist and a professor at U SEE Irvine, 19 00:01:16,520 --> 00:01:19,800 Speaker 1: and I will always support Berkeley over Stanford. What about 20 00:01:19,800 --> 00:01:26,160 Speaker 1: Berkeley over Irvine? Don't make me go there, man, are 21 00:01:26,200 --> 00:01:29,080 Speaker 1: you pro where does it art varks or bears? Like? 22 00:01:29,080 --> 00:01:30,759 Speaker 1: Which one would win in a fight? Do you think 23 00:01:30,840 --> 00:01:34,240 Speaker 1: a bear or an art vark? Well, bear sleep a lot, 24 00:01:34,280 --> 00:01:36,080 Speaker 1: so I think you know, while there's snooze in the 25 00:01:36,160 --> 00:01:37,959 Speaker 1: art bark could just like slip in there and lick 26 00:01:38,040 --> 00:01:40,319 Speaker 1: their face with its long tongue. Anyway, it's an ant 27 00:01:40,360 --> 00:01:43,200 Speaker 1: eater and not an art bark. Is there a difference? 28 00:01:43,480 --> 00:01:47,160 Speaker 1: Is there a difference? O? Gosh? Welcome to Creature feature 29 00:01:47,200 --> 00:01:51,480 Speaker 1: the podcast about art varks and or college mascots one 30 00:01:51,520 --> 00:01:53,640 Speaker 1: of the two. But anyways, welcome to a podcast. Daniel 31 00:01:53,640 --> 00:01:56,000 Speaker 1: and Jorge Explain the Universe, a production of I Heart 32 00:01:56,080 --> 00:01:57,920 Speaker 1: Radio in which we take you on a tour of 33 00:01:57,960 --> 00:02:00,520 Speaker 1: the universe, regardless of where you went to college or 34 00:02:00,600 --> 00:02:03,320 Speaker 1: if you went to college. The goal of this podcast 35 00:02:03,480 --> 00:02:06,760 Speaker 1: is to get everybody on board with this journey of exploration, 36 00:02:07,000 --> 00:02:09,919 Speaker 1: to wonder how the universe works, how it might have been, 37 00:02:10,240 --> 00:02:12,679 Speaker 1: why it is the way that it is, and can 38 00:02:12,720 --> 00:02:15,160 Speaker 1: it make sense to all of us? It's right because 39 00:02:15,160 --> 00:02:18,280 Speaker 1: it is a pretty mysterious universe full of interesting phenomena 40 00:02:18,320 --> 00:02:20,480 Speaker 1: for us to look at and gepe that and wonder 41 00:02:20,520 --> 00:02:23,520 Speaker 1: about and there we importantly ask questions about I have 42 00:02:23,520 --> 00:02:25,880 Speaker 1: a question for you, which is, you know, if Berkeley 43 00:02:25,960 --> 00:02:28,720 Speaker 1: is the Golden Bear and Irvine is the ant eater, 44 00:02:29,040 --> 00:02:33,600 Speaker 1: what is Stanford's mascot? Is it a tree? It's Silicon Valley? Money, 45 00:02:33,919 --> 00:02:42,040 Speaker 1: piles of cash, piles of bitcoins probably these days. Yeah, well, 46 00:02:42,120 --> 00:02:44,519 Speaker 1: we're not gonna let this go. Are we the Stanford 47 00:02:44,520 --> 00:02:47,160 Speaker 1: Berkeley thing on this episode? Oh no, Man, Berkeley over 48 00:02:47,200 --> 00:02:51,680 Speaker 1: Stanford all day every day. Maybe should discuss our after 49 00:02:52,000 --> 00:02:54,960 Speaker 1: grad school school. So I went to Caltech and you 50 00:02:55,000 --> 00:02:57,440 Speaker 1: went to EC Irvine. After grad school, actually went to 51 00:02:57,440 --> 00:03:00,799 Speaker 1: the University of Pennsylvania, which is a private school. And yeah, 52 00:03:00,880 --> 00:03:03,040 Speaker 1: then I did go to UC Irvine. And I've bounced 53 00:03:03,040 --> 00:03:05,760 Speaker 1: back and forth between public and private institutions, but in 54 00:03:05,800 --> 00:03:09,080 Speaker 1: the end, my heart really is in public institutions because 55 00:03:09,160 --> 00:03:11,560 Speaker 1: they serve the public, and you know, to get off 56 00:03:11,560 --> 00:03:13,800 Speaker 1: the jokes for a moment, like, I really do believe 57 00:03:14,160 --> 00:03:16,919 Speaker 1: in the mission of educating the public and providing a 58 00:03:17,440 --> 00:03:21,320 Speaker 1: path of mobility for people. California public college system from 59 00:03:21,320 --> 00:03:23,000 Speaker 1: the cow States all the way up to the University 60 00:03:23,000 --> 00:03:25,800 Speaker 1: of California's that they do an incredible public service. And 61 00:03:25,840 --> 00:03:27,960 Speaker 1: I think that this podcast is part of that. We 62 00:03:28,000 --> 00:03:30,520 Speaker 1: want to reach out and educate everybody about the mysteries 63 00:03:30,560 --> 00:03:33,080 Speaker 1: of the universe, not just those that have piles of 64 00:03:33,120 --> 00:03:36,080 Speaker 1: cash or stacks of bitcoin. Yeah, and that's why you 65 00:03:36,120 --> 00:03:42,680 Speaker 1: renounced your undergraduate institution, right, no comment. I'm just kidding. 66 00:03:43,360 --> 00:03:45,800 Speaker 1: But it is a pretty amazing universe full of things 67 00:03:45,800 --> 00:03:48,600 Speaker 1: to discover that are there for everyone to wonder and 68 00:03:48,880 --> 00:03:51,720 Speaker 1: to look in and to have questions about. Because people 69 00:03:51,800 --> 00:03:54,400 Speaker 1: have questions. People do have questions, and they write to 70 00:03:54,520 --> 00:03:57,000 Speaker 1: us with their questions. And the cross section of folks 71 00:03:57,040 --> 00:03:59,800 Speaker 1: who write to us is just incredible. From seven year 72 00:03:59,840 --> 00:04:03,600 Speaker 1: old wondering about black holes, to night guards at hospitals 73 00:04:03,640 --> 00:04:05,960 Speaker 1: who listen to our podcast while they walk the halls, 74 00:04:06,320 --> 00:04:09,520 Speaker 1: to pro bono attorneys from Alabama who listened to our 75 00:04:09,560 --> 00:04:12,080 Speaker 1: podcast is a break from the craziness of their lives. 76 00:04:12,440 --> 00:04:15,440 Speaker 1: Everybody out there wonders about the nature of the universe 77 00:04:15,520 --> 00:04:18,080 Speaker 1: and how it works, and whether it's possible for it 78 00:04:18,120 --> 00:04:20,400 Speaker 1: all to make sense to them. Yeah, that is pretty 79 00:04:20,400 --> 00:04:23,039 Speaker 1: incredible to think that there are so many people listening 80 00:04:23,040 --> 00:04:25,440 Speaker 1: to this and kind of thinking about the same topics 81 00:04:25,440 --> 00:04:27,159 Speaker 1: at the same time. Makes us all sort of feel 82 00:04:27,200 --> 00:04:29,440 Speaker 1: connected in a way like we're all wondering about the 83 00:04:29,480 --> 00:04:32,000 Speaker 1: universe at the same time together. Yeah, we are all 84 00:04:32,000 --> 00:04:34,919 Speaker 1: wondering about the universe, and I hope that means that 85 00:04:34,960 --> 00:04:38,279 Speaker 1: we're also connected to like alien scientists who I think 86 00:04:38,279 --> 00:04:41,200 Speaker 1: are probably wondering about the same universe. I like to 87 00:04:41,240 --> 00:04:44,919 Speaker 1: fantasize about a whole galactic community of scientists wondering about 88 00:04:44,920 --> 00:04:47,680 Speaker 1: the nature of this crazy cosmos, and we're just a 89 00:04:47,720 --> 00:04:49,520 Speaker 1: tiny little piece of it. Well, I feel like you 90 00:04:49,640 --> 00:04:52,560 Speaker 1: just stepped it up a notch there. I was going 91 00:04:52,600 --> 00:04:54,680 Speaker 1: for some sort of human grandeur, but you took it 92 00:04:54,720 --> 00:04:57,280 Speaker 1: to the galactic level. That's what we do on this podcast, man, 93 00:04:57,480 --> 00:05:00,719 Speaker 1: take it to the galactic level every time. I don't 94 00:05:00,720 --> 00:05:03,400 Speaker 1: know if I want to mind meld with aliens necessarily, though. 95 00:05:03,520 --> 00:05:06,080 Speaker 1: Do you think we've enjoyed that experience? Well, you know, 96 00:05:06,120 --> 00:05:08,480 Speaker 1: that's sort of the Berkeley approach. You know, we're all 97 00:05:08,560 --> 00:05:12,920 Speaker 1: one with the universe. Man, I have to take any 98 00:05:13,000 --> 00:05:16,200 Speaker 1: particular substances to kind of reach that state that I 99 00:05:16,200 --> 00:05:19,840 Speaker 1: can approchase maybe at Berkeley Bananappeals for sure. Yeah. But yeah, 100 00:05:19,880 --> 00:05:22,760 Speaker 1: people definitely have questions, and sometimes we get those questions 101 00:05:22,800 --> 00:05:25,039 Speaker 1: here on the podcast. People send them to us over 102 00:05:25,120 --> 00:05:28,000 Speaker 1: email or through social media. That's right. So if you 103 00:05:28,160 --> 00:05:30,520 Speaker 1: have questions about the nature of the universe, or there's 104 00:05:30,520 --> 00:05:33,520 Speaker 1: something we said on the podcast that you didn't quite understand, 105 00:05:33,720 --> 00:05:36,039 Speaker 1: or there's just been something bugging you that you really 106 00:05:36,080 --> 00:05:38,760 Speaker 1: need to get explained, please don't be shy right to 107 00:05:38,839 --> 00:05:41,560 Speaker 1: us two questions at Daniel and Jorge dot com. We 108 00:05:41,680 --> 00:05:45,240 Speaker 1: answer every single question. We will answer your question. Yeah, 109 00:05:45,279 --> 00:05:48,200 Speaker 1: and sometimes the questions are so interesting that Daniel picks 110 00:05:48,279 --> 00:05:51,680 Speaker 1: them to answer on the podcast. Yeah. Sometimes the questions 111 00:05:51,760 --> 00:05:53,039 Speaker 1: make me go off and do a bit of a 112 00:05:53,080 --> 00:05:55,560 Speaker 1: dive or research to get a solid answer. And sometimes 113 00:05:55,600 --> 00:05:57,480 Speaker 1: I think it's a question that other people might want 114 00:05:57,520 --> 00:05:59,640 Speaker 1: to hear the answer to. And sometimes I think this 115 00:05:59,760 --> 00:06:02,600 Speaker 1: is be fun to laugh with Jorge about, make fun 116 00:06:02,600 --> 00:06:06,080 Speaker 1: of or to laugh about what are your plans here? Well, 117 00:06:06,120 --> 00:06:07,920 Speaker 1: you know, I try to be nice to Stanford grads 118 00:06:07,920 --> 00:06:09,920 Speaker 1: who you know, went to a junior college after all, 119 00:06:10,160 --> 00:06:15,160 Speaker 1: that's right, ideas who are are not physicists. So today 120 00:06:15,200 --> 00:06:23,440 Speaker 1: on the podcast will be tackling listener questions number twenty 121 00:06:23,480 --> 00:06:27,239 Speaker 1: five and also titled Jorhan Daniel keep Fighting about Berkeley 122 00:06:27,240 --> 00:06:30,640 Speaker 1: and Stanford. You see, you really you're the ones SEO 123 00:06:30,640 --> 00:06:32,839 Speaker 1: seems to be bringing it up more. No, I think 124 00:06:32,839 --> 00:06:35,279 Speaker 1: that's probably true. I think Berkeley folks probably feel the 125 00:06:35,279 --> 00:06:39,000 Speaker 1: Berkeley Stanford rivalry more than Stanford folks, who are like, what, 126 00:06:39,160 --> 00:06:42,279 Speaker 1: who cares academy chip on the shoulder? I think so 127 00:06:42,520 --> 00:06:46,680 Speaker 1: probably where the public university that could. I think the 128 00:06:46,760 --> 00:06:49,120 Speaker 1: more interesting question is an art park the same as 129 00:06:49,160 --> 00:06:52,520 Speaker 1: an an eater? I think the question is how did 130 00:06:52,560 --> 00:06:54,440 Speaker 1: you get a Stanford education? And not know the answer 131 00:06:54,440 --> 00:06:59,640 Speaker 1: to that? Well, I was in the engineering department. I 132 00:06:59,680 --> 00:07:02,200 Speaker 1: didn't zoology one on one, right, Yeah, don't you like 133 00:07:02,320 --> 00:07:07,120 Speaker 1: look to nature for inspiration? Well? I felt like the 134 00:07:07,200 --> 00:07:10,920 Speaker 1: straw was already invented, so I didn't need to copy 135 00:07:11,000 --> 00:07:13,560 Speaker 1: the ant eaters trunk. Oh, I see, all right, that's 136 00:07:13,560 --> 00:07:15,760 Speaker 1: true to invent something. Yeah, and well, there's not much 137 00:07:15,800 --> 00:07:18,880 Speaker 1: of a market for an ant eating robot anyway, or 138 00:07:19,000 --> 00:07:23,760 Speaker 1: ant eating straw. But anyways, we're here to answer questions 139 00:07:23,800 --> 00:07:26,520 Speaker 1: from listeners. And this is the twenty fifth episode that 140 00:07:26,640 --> 00:07:28,240 Speaker 1: we've done this, and I feel like we don't do 141 00:07:28,280 --> 00:07:31,000 Speaker 1: this enough. Daniel, I really like these episodes. Oh good, well, 142 00:07:31,160 --> 00:07:32,560 Speaker 1: let's do some more of them. I think these are 143 00:07:32,560 --> 00:07:34,320 Speaker 1: a lot of fun also, and today we have a 144 00:07:34,400 --> 00:07:37,840 Speaker 1: question inspired by one of our previous listener question episodes. 145 00:07:38,040 --> 00:07:42,000 Speaker 1: WHOA what We're going inception? Here we are deep diving 146 00:07:42,240 --> 00:07:44,600 Speaker 1: like a question within a question episode. Yeah. Well, that's 147 00:07:44,600 --> 00:07:46,720 Speaker 1: the wonderful thing about questions is that the answer is 148 00:07:46,800 --> 00:07:49,040 Speaker 1: just raised more questions. They make people think in a 149 00:07:49,080 --> 00:07:51,400 Speaker 1: way they had them before. They make people's brains go 150 00:07:51,560 --> 00:07:54,440 Speaker 1: places they hadn't gone before without needing to buy anything 151 00:07:54,520 --> 00:08:01,000 Speaker 1: on Telegraph Avenue. Yeah, but that optional, I guess. I 152 00:08:01,040 --> 00:08:03,800 Speaker 1: mean it might make the podcast actually more interesting to 153 00:08:03,920 --> 00:08:06,440 Speaker 1: some people exactly. That's what we've been talking about bananas 154 00:08:06,480 --> 00:08:10,880 Speaker 1: the whole time. But we have three pretty awesome questions 155 00:08:10,880 --> 00:08:13,320 Speaker 1: here today from listeners, and they have to do with 156 00:08:13,480 --> 00:08:17,440 Speaker 1: the ice age here on planet Earth, about how photons 157 00:08:17,520 --> 00:08:20,720 Speaker 1: move near black holes, and also what would happen if 158 00:08:20,760 --> 00:08:23,800 Speaker 1: the speed of light changed. So thanks to those listeners 159 00:08:23,840 --> 00:08:26,080 Speaker 1: who sent in their questions, and also we're willing to 160 00:08:26,120 --> 00:08:28,760 Speaker 1: record their audio, and don't forget if you have a question, 161 00:08:28,800 --> 00:08:31,160 Speaker 1: you can also get an answer right to questions at 162 00:08:31,240 --> 00:08:34,240 Speaker 1: Daniel and Jorge dot com. Al Right, the first question 163 00:08:34,280 --> 00:08:37,360 Speaker 1: we have here is from Carson, who has a question 164 00:08:37,400 --> 00:08:40,760 Speaker 1: about the ice age. So I listened to the podcast 165 00:08:40,880 --> 00:08:45,560 Speaker 1: about the asteroid and the dinosaurs, and I was wondering, 166 00:08:46,320 --> 00:08:49,480 Speaker 1: what would happen if the ice age hadn't happened. Thanks 167 00:08:49,480 --> 00:08:52,840 Speaker 1: for answering all my questions. Pretty cool question, Thank you, Carson. 168 00:08:53,000 --> 00:08:54,920 Speaker 1: I guess Carson has a question is kind of like 169 00:08:55,400 --> 00:08:57,920 Speaker 1: what if question, Like how different would the Earth be 170 00:08:58,120 --> 00:09:01,520 Speaker 1: if certain things hadn't happened. It's a really fun question, 171 00:09:01,800 --> 00:09:04,720 Speaker 1: and it gets to the heart of how our entire 172 00:09:04,840 --> 00:09:09,480 Speaker 1: existence depends on so many tiny little factors, just like 173 00:09:09,520 --> 00:09:11,720 Speaker 1: if an asteroid hadn't hit the Earth, or if the 174 00:09:11,720 --> 00:09:15,160 Speaker 1: Earth hadn't warmed or cooled, so many chaotic events which 175 00:09:15,200 --> 00:09:18,240 Speaker 1: could have been different were crucial to us being here 176 00:09:18,360 --> 00:09:21,120 Speaker 1: right now, and so it's really fun to imagine alternative 177 00:09:21,200 --> 00:09:25,320 Speaker 1: Earth's different scenarios where things might have turned out very differently. Yeah, 178 00:09:25,320 --> 00:09:27,760 Speaker 1: I think Carson just wants us to talk about dinosaurs. 179 00:09:28,920 --> 00:09:30,680 Speaker 1: But you know, you can't blame them. You know what 180 00:09:30,880 --> 00:09:33,280 Speaker 1: young person doesn't want to talk about dinosaurs? Or maybe 181 00:09:33,280 --> 00:09:35,520 Speaker 1: Carson's thinking about where to go to college and is wondering, 182 00:09:35,559 --> 00:09:40,440 Speaker 1: you know, like Berkeley Stanford. You know, well, you're really 183 00:09:40,480 --> 00:09:43,160 Speaker 1: not dropping this. Well, well, Carson, I have to tell 184 00:09:43,160 --> 00:09:45,599 Speaker 1: you if there is another ice age, Berkeley's going to 185 00:09:45,679 --> 00:09:48,800 Speaker 1: freeze first before Stanford. Just letting you know that it 186 00:09:48,920 --> 00:09:50,880 Speaker 1: is a little bit more north and on the other 187 00:09:50,880 --> 00:09:52,959 Speaker 1: side of the Bay, which gets colder, and therefore it 188 00:09:52,960 --> 00:09:55,760 Speaker 1: will have a larger snowpack and better water reserves that 189 00:09:55,920 --> 00:10:01,440 Speaker 1: lasted through the summer. Because we're not nice to the 190 00:10:01,520 --> 00:10:05,800 Speaker 1: Bay area. I'm not sure where you're going directly thinking 191 00:10:05,800 --> 00:10:08,240 Speaker 1: to me, this question is really fascinating because there are 192 00:10:08,280 --> 00:10:11,800 Speaker 1: a lot of connections between ice ages and the physics 193 00:10:11,920 --> 00:10:14,200 Speaker 1: of the Solar system. That is, you know, how the 194 00:10:14,240 --> 00:10:16,800 Speaker 1: Earth goes around the Sun, and the variations in the 195 00:10:16,800 --> 00:10:19,719 Speaker 1: Earth's orbit really do have a strong impact on how 196 00:10:19,800 --> 00:10:22,600 Speaker 1: much sun we get and how much ice there is 197 00:10:22,679 --> 00:10:25,319 Speaker 1: on the Earth. Yeah, it's pretty interesting the connection there, 198 00:10:25,480 --> 00:10:28,480 Speaker 1: and it's amazing that Carson had been thinking about the 199 00:10:28,480 --> 00:10:31,120 Speaker 1: ice age. I guess we've had several ice ages throughout 200 00:10:31,160 --> 00:10:33,760 Speaker 1: the ages. We have had several ice ages, and if 201 00:10:33,800 --> 00:10:36,840 Speaker 1: you cast your mind back, like really deep far into 202 00:10:36,880 --> 00:10:40,040 Speaker 1: the history of the Earth, it's incredible how different the 203 00:10:40,040 --> 00:10:43,280 Speaker 1: Earth looked like around six fifty million years ago. We 204 00:10:43,280 --> 00:10:46,000 Speaker 1: were in the depths of an ice age, so cold 205 00:10:46,400 --> 00:10:48,760 Speaker 1: that they think that ice reached all the way down 206 00:10:48,800 --> 00:10:53,360 Speaker 1: to the equator, like it was basically a snowball Earth. Whoa, Yeah, 207 00:10:53,400 --> 00:10:54,880 Speaker 1: Like if you took a picture of it, you would 208 00:10:54,880 --> 00:10:57,000 Speaker 1: just see a big white ball, kind of like when 209 00:10:57,040 --> 00:10:58,800 Speaker 1: you look at you know, some of the ice planets. 210 00:10:59,280 --> 00:11:01,839 Speaker 1: So if you're an alien scientists visiting Earth for an 211 00:11:01,880 --> 00:11:05,560 Speaker 1: interstellar physics conference and you arrived, you know, six million 212 00:11:05,640 --> 00:11:08,280 Speaker 1: years too early, you wouldn't find anybody to talk to 213 00:11:08,440 --> 00:11:11,400 Speaker 1: and you think, oh, that's just a frozen wasteland, or 214 00:11:11,440 --> 00:11:14,400 Speaker 1: you might think, great ski here. Hello. Yeah, I hope 215 00:11:14,440 --> 00:11:17,320 Speaker 1: that one day we like unfaw some big block of 216 00:11:17,360 --> 00:11:19,640 Speaker 1: ice and find an alien skiing. That would be an 217 00:11:19,679 --> 00:11:25,560 Speaker 1: incredible discovery. But then, you know, wouldn't their snowboards hover? Also? 218 00:11:26,440 --> 00:11:27,800 Speaker 1: I mean, if they made it all the way here 219 00:11:27,800 --> 00:11:29,720 Speaker 1: for a ski vacation, I wonder what would be in 220 00:11:29,720 --> 00:11:35,120 Speaker 1: that flask. But anyways, ice ages are interesting, as you said, 221 00:11:35,120 --> 00:11:37,600 Speaker 1: because they are connected to kind of the physics of 222 00:11:37,800 --> 00:11:40,959 Speaker 1: our planet and the physics of our planet revolving around 223 00:11:40,960 --> 00:11:43,600 Speaker 1: the Sun, like it's it's heavily tied to the orbit 224 00:11:43,640 --> 00:11:45,880 Speaker 1: and the tilt of the planet. Right. There are a 225 00:11:45,880 --> 00:11:48,959 Speaker 1: lot of factors that affect ice ages, from climates to 226 00:11:49,280 --> 00:11:52,760 Speaker 1: continental drift, all sorts of things, and scientists don't have 227 00:11:52,800 --> 00:11:55,560 Speaker 1: a complete understanding of what causes these things. There are 228 00:11:55,600 --> 00:11:57,840 Speaker 1: still lots of big open questions. But one thing that 229 00:11:57,880 --> 00:12:00,760 Speaker 1: we do know is that changes in how the Earth 230 00:12:00,880 --> 00:12:03,440 Speaker 1: orbits the Sun, for example, whether the Earth's orbit is 231 00:12:03,480 --> 00:12:06,679 Speaker 1: circular or whether it's become more elliptical, and changes in 232 00:12:06,679 --> 00:12:10,000 Speaker 1: the earth tilt. These things can affect how much solar 233 00:12:10,080 --> 00:12:13,199 Speaker 1: radiation falls on the Earth, and that affects the temperature 234 00:12:13,240 --> 00:12:15,640 Speaker 1: for sure. Wow. Well, first of all, I guess maybe 235 00:12:15,679 --> 00:12:17,320 Speaker 1: this is something I hadn't thought about. Is is the 236 00:12:17,360 --> 00:12:20,680 Speaker 1: Earth's orbit not constant? Isn't it like a perfect circle 237 00:12:20,880 --> 00:12:24,520 Speaker 1: or slight oval? And are you saying there's some variations 238 00:12:24,520 --> 00:12:27,880 Speaker 1: in that trajectory. There are definitely variations in that trajectory. 239 00:12:28,080 --> 00:12:30,440 Speaker 1: And it goes from being like almost a perfect circle 240 00:12:30,640 --> 00:12:34,280 Speaker 1: to being more elliptical. And it becomes elliptical by having 241 00:12:34,360 --> 00:12:37,760 Speaker 1: the semi minor axis get a little shorter. So it's 242 00:12:37,760 --> 00:12:39,640 Speaker 1: not like the Earth gets further from the Sun but 243 00:12:39,720 --> 00:12:42,040 Speaker 1: during parts of its orbit and then gets closer to 244 00:12:42,080 --> 00:12:45,760 Speaker 1: the Sun. Wait, what so what determines these changes in 245 00:12:46,000 --> 00:12:48,280 Speaker 1: our orbit? So if the Earth was alone in the 246 00:12:48,320 --> 00:12:50,800 Speaker 1: Solar System, it would have a very simple, stable orbit 247 00:12:50,840 --> 00:12:53,240 Speaker 1: around the Sun. But it's not, and there are other 248 00:12:53,360 --> 00:12:57,079 Speaker 1: things in the Solar System, like Jupiter and other gravitational bodies. 249 00:12:57,360 --> 00:13:00,960 Speaker 1: These things have very gentle tugs on Earth's orbit. We're 250 00:13:00,960 --> 00:13:04,080 Speaker 1: into a whole episode soon about spin resonances and tidle 251 00:13:04,160 --> 00:13:07,439 Speaker 1: locking the whole Solar systems. That an incredibly complicated Swiss watch, 252 00:13:07,520 --> 00:13:10,000 Speaker 1: but it means that there are these cycles that change 253 00:13:10,000 --> 00:13:12,920 Speaker 1: how the Earth tilts and also how the Earth orbits 254 00:13:12,960 --> 00:13:15,400 Speaker 1: as it goes around the Sun based on these little 255 00:13:15,440 --> 00:13:19,080 Speaker 1: gentle tugs from things other than the Sun. Wow, I 256 00:13:19,080 --> 00:13:21,600 Speaker 1: guess there's still pretty small changes. Maybe, like if you 257 00:13:21,640 --> 00:13:23,920 Speaker 1: look at the picture of it, maybe you couldn't tell 258 00:13:23,920 --> 00:13:26,679 Speaker 1: the difference between the different orbits. Yeah, the orbital changes 259 00:13:26,720 --> 00:13:29,200 Speaker 1: are not huge, or if you're looking from a distance 260 00:13:29,240 --> 00:13:32,080 Speaker 1: you definitely could see anything. But you know, small changes 261 00:13:32,240 --> 00:13:35,080 Speaker 1: in how much the Earth tilts towards the Sun or 262 00:13:35,080 --> 00:13:37,200 Speaker 1: how far away it is from the Sun you really 263 00:13:37,240 --> 00:13:40,240 Speaker 1: can have a strong impact on the amount of solar radiation. 264 00:13:40,679 --> 00:13:43,280 Speaker 1: For example, if you look back over the last twenty 265 00:13:43,400 --> 00:13:46,320 Speaker 1: or hundred thousand years, you see variations of up to 266 00:13:46,440 --> 00:13:49,600 Speaker 1: twenty percent in the amount of solar radiation that hits 267 00:13:49,640 --> 00:13:52,840 Speaker 1: the Earth based on these cycles. Wow. Yeah, I guess 268 00:13:52,880 --> 00:13:54,560 Speaker 1: you can sort of look at the record, right, Like 269 00:13:54,640 --> 00:13:56,720 Speaker 1: you can look at ice layers and rock layers and 270 00:13:56,760 --> 00:13:59,120 Speaker 1: you can see that it used to be sunnier before 271 00:13:59,520 --> 00:14:01,679 Speaker 1: or not. Yeah. They do these core samples where they 272 00:14:01,720 --> 00:14:04,400 Speaker 1: dig down and layers of ice in Greenland or in 273 00:14:04,440 --> 00:14:06,160 Speaker 1: other parts of the world, and they can see the 274 00:14:06,200 --> 00:14:09,600 Speaker 1: global temperatures and there really is variation. And they do 275 00:14:09,679 --> 00:14:12,960 Speaker 1: these calculations based on you know, solar system models and 276 00:14:13,040 --> 00:14:15,640 Speaker 1: to understand the variations in the Earth's tilt and orbit. 277 00:14:15,679 --> 00:14:18,920 Speaker 1: And there's a really nice alignment between these global temperatures 278 00:14:18,960 --> 00:14:22,640 Speaker 1: and these Earth's orbital changes. Wow. And it's crazy because 279 00:14:22,720 --> 00:14:26,720 Speaker 1: it's like small, even tiny, little changes can basically change 280 00:14:26,760 --> 00:14:29,600 Speaker 1: the weather. Like if the Earth tilled three degrees or 281 00:14:29,640 --> 00:14:31,840 Speaker 1: two degrees this way or that way a little bit more, 282 00:14:31,920 --> 00:14:35,160 Speaker 1: then suddenly we have an ice age. It really is incredible. 283 00:14:35,200 --> 00:14:37,520 Speaker 1: But this is just one effect. It's important to understand 284 00:14:37,800 --> 00:14:41,800 Speaker 1: other things, like atmospheric effects can drown them out. For example, 285 00:14:42,080 --> 00:14:45,320 Speaker 1: if we hadn't been pumping c O two into our atmosphere, 286 00:14:45,400 --> 00:14:48,240 Speaker 1: scientists predicted we'd be due for like a big glaciation 287 00:14:48,360 --> 00:14:51,440 Speaker 1: stage in about fifty thou years. Now that's sort of 288 00:14:51,440 --> 00:14:53,400 Speaker 1: off the table because the amount of C O two 289 00:14:53,400 --> 00:14:56,400 Speaker 1: that we pumped into the atmosphere, so we can override 290 00:14:56,440 --> 00:14:59,520 Speaker 1: these effects with larger effects like the Greenhouse effect. Well, 291 00:14:59,520 --> 00:15:02,080 Speaker 1: it's in doable. So we can actually like change the 292 00:15:02,120 --> 00:15:04,840 Speaker 1: destiny of the Earth, like we could totally ruin it 293 00:15:04,880 --> 00:15:08,800 Speaker 1: perhaps even yeah, exactly. And so I just don't want 294 00:15:08,800 --> 00:15:11,320 Speaker 1: anybody out there to think that all of the change 295 00:15:11,320 --> 00:15:14,080 Speaker 1: in the atmosphere is due to natural effects from the 296 00:15:14,080 --> 00:15:16,880 Speaker 1: Earth's orbit. This is an effect, and it has contributed 297 00:15:16,920 --> 00:15:20,600 Speaker 1: to glaciation into ice ages, but it's not the only effect, 298 00:15:20,720 --> 00:15:22,720 Speaker 1: and it doesn't even have to be the dominant effect. 299 00:15:22,800 --> 00:15:24,680 Speaker 1: And it also sort of impact as you said, how 300 00:15:24,760 --> 00:15:27,600 Speaker 1: much radiation we get. Like if if our orbit but 301 00:15:27,680 --> 00:15:29,520 Speaker 1: you know, flies a little bit closer to the Sun, 302 00:15:29,560 --> 00:15:32,000 Speaker 1: it's going to get a little harder on Earth too. Yeah, 303 00:15:32,040 --> 00:15:34,000 Speaker 1: And some of these things can be sort of dramatic, 304 00:15:34,240 --> 00:15:36,720 Speaker 1: like you have different cycles based on the orbit and 305 00:15:36,760 --> 00:15:38,760 Speaker 1: the tilt and all these things that are different cycles 306 00:15:38,760 --> 00:15:41,520 Speaker 1: there which have different periods like twenty or forty or 307 00:15:41,520 --> 00:15:44,920 Speaker 1: a hundred thousand years. Sometimes they all come together and 308 00:15:45,040 --> 00:15:47,160 Speaker 1: happen all at the same time. You can get pretty 309 00:15:47,240 --> 00:15:51,240 Speaker 1: dramatic shifts in temperature, like about thirteen thousand years ago 310 00:15:51,280 --> 00:15:54,800 Speaker 1: when temperatures dropped dramatically in just a few decades, and 311 00:15:54,840 --> 00:15:58,800 Speaker 1: then thirteen hundred years later, temperatures spiked like ten degrees 312 00:15:58,840 --> 00:16:01,880 Speaker 1: celsius within just a few years. As like all of 313 00:16:01,920 --> 00:16:04,480 Speaker 1: the effects swung one way and then swung the other way. 314 00:16:04,600 --> 00:16:07,400 Speaker 1: These things can have really big effects on the Earth's climate. 315 00:16:07,480 --> 00:16:11,640 Speaker 1: Ten degrees is huge. It seems like it's not totally unpredictable, right, Like, 316 00:16:11,680 --> 00:16:13,880 Speaker 1: we have a certain model of the Solar system and 317 00:16:13,920 --> 00:16:16,880 Speaker 1: our our atmosphere, and so you know, we should believe 318 00:16:16,920 --> 00:16:18,960 Speaker 1: the signists when they say what's going to happen next. Yeah, 319 00:16:19,000 --> 00:16:22,040 Speaker 1: this part is pretty predictable because we have good models 320 00:16:22,320 --> 00:16:25,120 Speaker 1: for how the Earth's orbit is affected by the tug 321 00:16:25,160 --> 00:16:28,640 Speaker 1: of Jupiter, etcetera, etcetera. The other parts, you know, climate 322 00:16:28,720 --> 00:16:32,160 Speaker 1: resonances and what happens with the greenhouse gases, that's something 323 00:16:32,200 --> 00:16:35,280 Speaker 1: we're working on, is not as well understood and can 324 00:16:35,360 --> 00:16:38,200 Speaker 1: be more dramatic. You know, something I didn't realize was 325 00:16:38,240 --> 00:16:40,800 Speaker 1: that the climate is even affected by the flow of 326 00:16:40,840 --> 00:16:44,080 Speaker 1: the continents. As the continents move over the surface of 327 00:16:44,120 --> 00:16:47,040 Speaker 1: the Earth, they change how water flows. Is there a 328 00:16:47,040 --> 00:16:49,960 Speaker 1: water channel between these two continents or not, for example, 329 00:16:49,960 --> 00:16:52,320 Speaker 1: And that affects how the atmosphere moves, and that can 330 00:16:52,360 --> 00:16:55,760 Speaker 1: have significant effects on the climate as well. There's a 331 00:16:55,800 --> 00:16:58,600 Speaker 1: lot going on. It's a big complicated system with a 332 00:16:58,720 --> 00:17:01,160 Speaker 1: huge number of feedback cycles, you know, so if you 333 00:17:01,160 --> 00:17:02,880 Speaker 1: get it a little bit wrong, then you can get 334 00:17:02,920 --> 00:17:05,280 Speaker 1: it a lot wrong. But you know, climate scientists are 335 00:17:05,320 --> 00:17:07,200 Speaker 1: doing a great job at modeling this stuff. Well, I 336 00:17:07,200 --> 00:17:10,199 Speaker 1: guess Carson's question is what would have happened if we 337 00:17:10,240 --> 00:17:13,800 Speaker 1: hadn't had the last ice age? And so let's talk 338 00:17:13,880 --> 00:17:17,560 Speaker 1: maybe about how an ice age impacts the Earth. Yeah, 339 00:17:17,600 --> 00:17:21,200 Speaker 1: so the most recent ice age, scientists say, lasted from 340 00:17:21,200 --> 00:17:23,320 Speaker 1: about two and a half million years ago till about 341 00:17:23,320 --> 00:17:27,040 Speaker 1: twelve thousand years ago, waited less than millions of years. Yeah, 342 00:17:27,080 --> 00:17:30,240 Speaker 1: these ice ages can last millions of years and sometimes 343 00:17:30,359 --> 00:17:33,159 Speaker 1: hundreds of millions of years. But within an ice age 344 00:17:33,240 --> 00:17:36,840 Speaker 1: there are more variations, and they call these glacial periods 345 00:17:37,000 --> 00:17:39,680 Speaker 1: where things can then the glaciers can retreat and come back. 346 00:17:39,800 --> 00:17:41,480 Speaker 1: And so the most dramatic and the one that really 347 00:17:41,520 --> 00:17:43,720 Speaker 1: affects sort of life on Earth and the way we live. 348 00:17:43,760 --> 00:17:46,600 Speaker 1: It is the last glacial period, which lasted from about 349 00:17:46,680 --> 00:17:50,120 Speaker 1: a hundred thousand years ago to about twelve thousand years ago. 350 00:17:50,560 --> 00:17:53,240 Speaker 1: That's the most recent impact on sort of like human 351 00:17:53,280 --> 00:17:57,960 Speaker 1: development and migration, because I guess the northern parts of 352 00:17:58,000 --> 00:18:00,920 Speaker 1: the and southernmost parts of the Earth more covered in 353 00:18:01,040 --> 00:18:03,720 Speaker 1: ice than usual, but not completely. You said that we 354 00:18:03,800 --> 00:18:06,840 Speaker 1: only got completely covered millions of years ago. That's right. 355 00:18:07,000 --> 00:18:09,760 Speaker 1: During this last glacial period, we had like Canada was 356 00:18:09,800 --> 00:18:12,439 Speaker 1: an ice sheet, most of the northern United States with 357 00:18:12,480 --> 00:18:14,720 Speaker 1: an ice sheet. There are lots of glaciers around the 358 00:18:14,760 --> 00:18:17,000 Speaker 1: world at high altitudes. But you know, it's not like 359 00:18:17,040 --> 00:18:19,159 Speaker 1: the whole Earth was an ice sheet. But you know 360 00:18:19,240 --> 00:18:22,479 Speaker 1: it affected the humanity. Humanity, for example, mostly lived at 361 00:18:22,560 --> 00:18:26,720 Speaker 1: lower latitudes during this stage until the ice retreated and 362 00:18:26,760 --> 00:18:30,120 Speaker 1: then they could migrate to Eurasia and more northern latitudes. 363 00:18:30,400 --> 00:18:32,480 Speaker 1: Like it was still sunny in the Equator. Yes, it 364 00:18:32,560 --> 00:18:34,800 Speaker 1: was still sunny in the Equator and hotter cool It 365 00:18:34,880 --> 00:18:36,960 Speaker 1: was cooler than it is today, but obviously it was 366 00:18:37,040 --> 00:18:39,280 Speaker 1: hotter at the equator than it was at the pole. Still, 367 00:18:40,280 --> 00:18:46,520 Speaker 1: what about Berkeley, Berkeley will always be cool man, very chill. 368 00:18:47,280 --> 00:18:49,280 Speaker 1: Not as chill as you see Santa Cruz. Right, there 369 00:18:49,440 --> 00:18:52,359 Speaker 1: are the chill ones. Yep, nobody can chill like bananas slugs. 370 00:18:53,000 --> 00:18:55,280 Speaker 1: All right, well, let's get a little bit more into 371 00:18:55,320 --> 00:18:57,639 Speaker 1: the impacts of the Ice Age on Earth and the 372 00:18:57,720 --> 00:19:00,600 Speaker 1: Last Ice Age on Earth and what would happen if 373 00:19:00,640 --> 00:19:02,800 Speaker 1: we hadn't had that ice age. First, let's take a 374 00:19:02,840 --> 00:19:18,400 Speaker 1: quick break. All right, we are answering questions from listeners, 375 00:19:18,520 --> 00:19:21,400 Speaker 1: and our first question was from Carson, who asked what 376 00:19:21,480 --> 00:19:24,080 Speaker 1: would have happened if we hadn't had the I guess 377 00:19:24,119 --> 00:19:26,639 Speaker 1: the Last Ice Age that's probably the one that Carson 378 00:19:26,720 --> 00:19:29,600 Speaker 1: is most wondering about. And you know, the Ice Age 379 00:19:29,640 --> 00:19:33,439 Speaker 1: has big impacts on geology because the glaciers can like 380 00:19:33,760 --> 00:19:37,320 Speaker 1: grind mountains and create valleys. It also has a big 381 00:19:37,320 --> 00:19:40,720 Speaker 1: impact on the flora and fauna that developed to adapt 382 00:19:40,760 --> 00:19:43,680 Speaker 1: to that climate, and specifically it had a pretty big 383 00:19:43,720 --> 00:19:47,880 Speaker 1: impact on where humans ended up and how we evolved. Yeah, 384 00:19:47,880 --> 00:19:50,000 Speaker 1: it's it's sort of an interesting effect that maybe when 385 00:19:50,000 --> 00:19:52,679 Speaker 1: I was younger, I hadn't thought about that, Like glaciers 386 00:19:52,720 --> 00:19:55,679 Speaker 1: can really kind of like smooth over a landscape. I 387 00:19:55,720 --> 00:19:57,840 Speaker 1: think a lot of the like the eastern United States 388 00:19:58,240 --> 00:20:01,560 Speaker 1: has you know, more rolling hills rather than dramatic mountains 389 00:20:01,600 --> 00:20:06,040 Speaker 1: because the glaciers basically like you know, crunched them all down. 390 00:20:06,480 --> 00:20:08,760 Speaker 1: I'm not actually sure about that. I think that smoother 391 00:20:08,880 --> 00:20:12,280 Speaker 1: mountains are just older mountains. They have been worn down 392 00:20:12,359 --> 00:20:15,520 Speaker 1: by wind and rain and cycles of weather. The Rockies, 393 00:20:15,560 --> 00:20:18,200 Speaker 1: for example, are sharper because they're younger. It's incredible in 394 00:20:18,240 --> 00:20:20,400 Speaker 1: the history of the science is really fascinating as people 395 00:20:20,480 --> 00:20:24,879 Speaker 1: realized that there was this incredible, powerful, dramatic force that 396 00:20:24,960 --> 00:20:27,880 Speaker 1: happened very very slowly on Earth. These moving of these 397 00:20:27,880 --> 00:20:31,480 Speaker 1: glaciers can really shape valleys and distribute boulders. It was 398 00:20:31,520 --> 00:20:34,080 Speaker 1: the presence of these boulders that tip people off. People 399 00:20:34,080 --> 00:20:36,200 Speaker 1: in the Alps were like, how did this rock get here? 400 00:20:36,200 --> 00:20:39,320 Speaker 1: It's for much more northern climates, and people were wondering, 401 00:20:39,359 --> 00:20:41,600 Speaker 1: like how to explain where all the rocks were, And 402 00:20:41,960 --> 00:20:45,560 Speaker 1: very slowly they put together this crazy story about sheets 403 00:20:45,600 --> 00:20:48,760 Speaker 1: of ice moving over the Earth and changing its shape. 404 00:20:48,760 --> 00:20:51,720 Speaker 1: It's kind of bonkers and like boulders hitching a ride 405 00:20:51,800 --> 00:20:56,400 Speaker 1: or like surfing the glacier wave. Yeah, glaciers break boulders 406 00:20:56,400 --> 00:20:59,320 Speaker 1: off the mountains and then can carry them for hundreds 407 00:20:59,359 --> 00:21:02,119 Speaker 1: of miles and deposit them somewhere else. Wow. Yeah, and 408 00:21:02,400 --> 00:21:06,159 Speaker 1: said how stone hands got a bill. I think that 409 00:21:06,280 --> 00:21:10,360 Speaker 1: was graffiti from the alien skiers. Actually the alien snowboarders 410 00:21:10,520 --> 00:21:14,239 Speaker 1: came to a snowboard and piles on rocks like like 411 00:21:14,520 --> 00:21:17,240 Speaker 1: the tourists usually do. I think that's another divide. We 412 00:21:17,240 --> 00:21:21,600 Speaker 1: don't want to get into skiers versus snowboarders. But yeah, 413 00:21:21,720 --> 00:21:24,240 Speaker 1: like you said, it really affects the trajectory not just 414 00:21:24,320 --> 00:21:26,760 Speaker 1: of the landscape but also life on earth. Like if 415 00:21:26,880 --> 00:21:29,040 Speaker 1: most of the Earth is covered in ice, it's gonna 416 00:21:29,480 --> 00:21:31,960 Speaker 1: you know, determine what kinds of animals survive and which 417 00:21:31,960 --> 00:21:34,520 Speaker 1: ones don't. And you know the kind of flora and 418 00:21:34,640 --> 00:21:36,760 Speaker 1: fauna that we have. You know, the fact that we 419 00:21:36,800 --> 00:21:39,000 Speaker 1: have like horses and cows, and a lot of the 420 00:21:39,040 --> 00:21:42,720 Speaker 1: grains we eat are basically evolved grasses. That's due to 421 00:21:42,880 --> 00:21:45,239 Speaker 1: the climate that we had. If we hadn't had an 422 00:21:45,240 --> 00:21:48,560 Speaker 1: ice age, for example, the whole earth might be wetter, 423 00:21:48,840 --> 00:21:50,879 Speaker 1: and it might be warmer, and it might be more 424 00:21:51,040 --> 00:21:56,320 Speaker 1: covered in jungles and rainforests than grassy plains. And so 425 00:21:56,440 --> 00:21:59,240 Speaker 1: the kind of farming practices we developed could have been 426 00:21:59,280 --> 00:22:02,760 Speaker 1: totally different. Oh. Interesting, So that's one way, one specific 427 00:22:02,800 --> 00:22:05,240 Speaker 1: way the Ice Age has you know, impacted us is 428 00:22:05,359 --> 00:22:09,600 Speaker 1: we would have less fewer horses and cows and grasses, grasslands, 429 00:22:10,080 --> 00:22:12,800 Speaker 1: and the whole concept of agriculture could be very different. 430 00:22:12,920 --> 00:22:15,240 Speaker 1: A farm could be basically a piece of forest. You know, 431 00:22:15,280 --> 00:22:18,080 Speaker 1: it's hard to imagine how civilization and how agriculture might 432 00:22:18,119 --> 00:22:20,800 Speaker 1: have developed in the context of basically everybody living in 433 00:22:20,800 --> 00:22:24,680 Speaker 1: the Amazon. Interesting. Yeah, because it might have also affected 434 00:22:24,760 --> 00:22:28,199 Speaker 1: human development, right, absolutely. There are some theories that the 435 00:22:28,280 --> 00:22:32,199 Speaker 1: harsh living conditions during the Ice Age basically forced humans 436 00:22:32,240 --> 00:22:35,120 Speaker 1: to develop cognition, to evolve bigger brains so we could 437 00:22:35,119 --> 00:22:38,400 Speaker 1: work together and develop tools, hunt willy mammoths, this kind 438 00:22:38,400 --> 00:22:41,359 Speaker 1: of stuff. It's certainly had an impact on humans, although 439 00:22:41,400 --> 00:22:45,320 Speaker 1: there's always the alternative reality game. They're like, sure that 440 00:22:45,400 --> 00:22:47,439 Speaker 1: might have played a role. We don't really know what 441 00:22:47,440 --> 00:22:50,000 Speaker 1: would have happened to humanity in other situations. Maybe we 442 00:22:50,040 --> 00:22:52,520 Speaker 1: would have been even smarter. I see. The theory is 443 00:22:52,520 --> 00:22:55,840 Speaker 1: sort of like, because it was we had these long winters, 444 00:22:56,080 --> 00:22:58,359 Speaker 1: it kind of forced humans to plan ahead and to 445 00:22:58,920 --> 00:23:02,200 Speaker 1: think about like crop since strategizing, which kind of pushed 446 00:23:02,200 --> 00:23:04,440 Speaker 1: this to be smarter and to be and to be 447 00:23:04,520 --> 00:23:09,479 Speaker 1: less procrastinators exactly. But these are always just explanatory stories, right, 448 00:23:09,480 --> 00:23:12,600 Speaker 1: There's aren't really testable theories. It's very easy to look 449 00:23:12,640 --> 00:23:14,920 Speaker 1: at the series events and say, oh, this makes sense, 450 00:23:14,960 --> 00:23:17,560 Speaker 1: and I think this is why it happened. To really know, 451 00:23:17,840 --> 00:23:20,399 Speaker 1: you'd have to run alternatives. You'd have to say, well, 452 00:23:20,440 --> 00:23:23,640 Speaker 1: let's see what happens if I change things? And that's 453 00:23:23,640 --> 00:23:25,919 Speaker 1: sort of a fascinating question. But one will never know 454 00:23:26,000 --> 00:23:28,440 Speaker 1: the answer too, because we only have this one universe 455 00:23:28,480 --> 00:23:31,960 Speaker 1: and we only see what happens to this Earth one time. Yeah, 456 00:23:31,960 --> 00:23:34,800 Speaker 1: we need like a control Earth for every single conceivable 457 00:23:34,800 --> 00:23:37,760 Speaker 1: experiment we do. We need the multiverse for that reason, 458 00:23:37,800 --> 00:23:39,560 Speaker 1: so you can see, you know, what would happen if 459 00:23:39,600 --> 00:23:41,960 Speaker 1: I had gone to Stanford? Would I be a different 460 00:23:42,000 --> 00:23:47,080 Speaker 1: person today? You'd definitely be much cooler. Maybe I had 461 00:23:47,200 --> 00:23:51,359 Speaker 1: or richer. Apparently, maybe you would have invented TikTok Daniel. 462 00:23:51,560 --> 00:23:52,760 Speaker 1: If I had, it would have been a lot more 463 00:23:52,800 --> 00:23:55,680 Speaker 1: boring than it is today. It would have been physics 464 00:23:55,680 --> 00:23:59,920 Speaker 1: though exactly all right, Well, I think that answers Carson's question. 465 00:24:00,160 --> 00:24:02,199 Speaker 1: If we hadn't had the ice age, things would be 466 00:24:02,240 --> 00:24:04,560 Speaker 1: really different. Well, first of all, it sort of depends 467 00:24:04,600 --> 00:24:07,640 Speaker 1: a lot on our trajectory in space and how close 468 00:24:07,680 --> 00:24:09,280 Speaker 1: we get to the Sun and how and how tilted 469 00:24:09,359 --> 00:24:10,880 Speaker 1: we are. But if we hadn't had the last one, 470 00:24:11,080 --> 00:24:14,120 Speaker 1: maybe we would be eating different kinds of plants and 471 00:24:14,400 --> 00:24:17,919 Speaker 1: fruits and animals and and or we might be a 472 00:24:17,920 --> 00:24:20,639 Speaker 1: little bit different ourselves. Yeah, we might all be roasting 473 00:24:20,640 --> 00:24:24,280 Speaker 1: banana slugs over the fire, and we might all be 474 00:24:24,320 --> 00:24:28,399 Speaker 1: procrastinators instead of just some of us being procrastinators. Speaking 475 00:24:28,400 --> 00:24:31,280 Speaker 1: of procrastination, let's get into our next question, and this 476 00:24:31,320 --> 00:24:35,000 Speaker 1: one comes from Chris, who has a question about photons 477 00:24:35,200 --> 00:24:38,639 Speaker 1: moving near black holes. Hi Danueine Horree, thank you so 478 00:24:38,720 --> 00:24:40,840 Speaker 1: much for your show. I look forward to it every week. 479 00:24:41,200 --> 00:24:45,000 Speaker 1: All right, here's my question about photons. So let's say 480 00:24:45,119 --> 00:24:49,280 Speaker 1: we are on Miller's planet, the like the one in Interstellar, 481 00:24:50,119 --> 00:24:52,080 Speaker 1: and we look up at the sky and we can 482 00:24:52,160 --> 00:24:55,840 Speaker 1: see a star. So the photons coming off that sun. 483 00:24:56,040 --> 00:24:58,960 Speaker 1: Let's say some of the photons missed the gravity of 484 00:24:59,000 --> 00:25:03,879 Speaker 1: the planet and continue on to their destination. But a 485 00:25:03,960 --> 00:25:07,840 Speaker 1: few of those photons get trapped or caught into the 486 00:25:07,880 --> 00:25:12,560 Speaker 1: gravity of the planet. So from the perspective of somebody 487 00:25:12,640 --> 00:25:15,320 Speaker 1: that's not in the gravity of the planet. Doesn't that 488 00:25:15,440 --> 00:25:21,119 Speaker 1: photon travel slower than the other photons that moved on 489 00:25:21,240 --> 00:25:23,160 Speaker 1: that didn't get caught in the gravity of the planet. 490 00:25:23,400 --> 00:25:27,440 Speaker 1: Kind of confusing, all right, thanks, kind of confusing for sure. 491 00:25:28,560 --> 00:25:31,800 Speaker 1: That's why we're here. I think there's a good summary 492 00:25:31,800 --> 00:25:34,840 Speaker 1: of general relativity right there. Kind of confusing, I guess 493 00:25:36,520 --> 00:25:40,879 Speaker 1: special realtivity. Chris, it's kind of confusing. But is there 494 00:25:41,000 --> 00:25:43,840 Speaker 1: really excellent question he's asking It really difficult and subtle 495 00:25:43,920 --> 00:25:46,560 Speaker 1: question about what it looks like to see a photon 496 00:25:46,960 --> 00:25:49,920 Speaker 1: go near a very massive object, to be sucked into 497 00:25:49,920 --> 00:25:52,080 Speaker 1: the gravity well of a black hole or a very 498 00:25:52,119 --> 00:25:55,240 Speaker 1: dense planet. Right, Because we've talked about on this podcast, 499 00:25:55,240 --> 00:25:57,200 Speaker 1: how when you have a lot of mass, like in 500 00:25:57,240 --> 00:25:59,720 Speaker 1: a black hole or just like a heavy planet, it 501 00:25:59,800 --> 00:26:02,760 Speaker 1: can bends the space time around it, and it actually 502 00:26:03,040 --> 00:26:06,000 Speaker 1: sort of slows down time. I think that's maybe what 503 00:26:06,080 --> 00:26:08,800 Speaker 1: he's trying to connect. Yeah, it can slow down time, 504 00:26:09,000 --> 00:26:10,920 Speaker 1: and also it changes the path of these particles. It 505 00:26:11,000 --> 00:26:14,760 Speaker 1: changes the fundamental geometry of space the way the particles move. 506 00:26:14,960 --> 00:26:18,360 Speaker 1: At least two really confusing and sort of paradoxical ideas, 507 00:26:18,480 --> 00:26:20,680 Speaker 1: Like one thing we say in the podcast a lot 508 00:26:20,720 --> 00:26:22,560 Speaker 1: and that people talk about in physics A lot is 509 00:26:22,880 --> 00:26:25,520 Speaker 1: light always moves at the speed of light, no matter 510 00:26:25,520 --> 00:26:27,800 Speaker 1: who's measuring it, right, We say that a lot. On 511 00:26:27,840 --> 00:26:30,439 Speaker 1: the other hand, we also say that like photons can't 512 00:26:30,560 --> 00:26:33,720 Speaker 1: escape a black hole, and people might be puzzling about that, 513 00:26:33,800 --> 00:26:36,360 Speaker 1: like what does that mean? How fast is a photon 514 00:26:36,680 --> 00:26:39,440 Speaker 1: moving when he's trying to climb out of that gravity? Well, 515 00:26:39,560 --> 00:26:42,520 Speaker 1: doesn't eventually get stopped by the gravity of the black hole. 516 00:26:42,680 --> 00:26:46,040 Speaker 1: Had he reconciled those two ideas, Yeah, it's kind of 517 00:26:46,080 --> 00:26:49,520 Speaker 1: confusing for sure, But I think maybe the scenario is 518 00:26:49,600 --> 00:26:51,359 Speaker 1: I think he was trying to paint, is that like, 519 00:26:51,440 --> 00:26:54,520 Speaker 1: let's say a star shoots off to photons and one 520 00:26:54,560 --> 00:26:58,240 Speaker 1: photonogy goes clear through space, no, no, nothing in its path, 521 00:26:58,600 --> 00:27:00,560 Speaker 1: But the other one flies like us, to a heavy 522 00:27:00,600 --> 00:27:02,679 Speaker 1: planet or close to a black hole. Like, if you 523 00:27:02,720 --> 00:27:05,199 Speaker 1: were looking at these two photons, but the one that 524 00:27:05,240 --> 00:27:07,480 Speaker 1: goes near the black hole, would that one go slower? Yeah? 525 00:27:07,520 --> 00:27:10,199 Speaker 1: Would you see a photon moving at less than the 526 00:27:10,240 --> 00:27:13,119 Speaker 1: speed of light? And your instinct, physics wise, is to 527 00:27:13,160 --> 00:27:16,000 Speaker 1: say no, absolutely, that can never happen. Problem is, that's 528 00:27:16,040 --> 00:27:20,359 Speaker 1: not exactly true. Because when we say photons always travel 529 00:27:20,400 --> 00:27:23,640 Speaker 1: at the speed of light, there's a qualifier there. There's 530 00:27:23,680 --> 00:27:26,640 Speaker 1: a caveat that we almost never mentioned that's important in 531 00:27:26,680 --> 00:27:30,280 Speaker 1: this particular case. And that caveat is that it's true 532 00:27:30,320 --> 00:27:33,080 Speaker 1: that photons always travel at the speed of light. But 533 00:27:33,200 --> 00:27:36,679 Speaker 1: that's only true if space is flat, that is, if 534 00:27:36,720 --> 00:27:42,480 Speaker 1: there's no curvature to space, and only true for nearby observers. 535 00:27:42,520 --> 00:27:45,680 Speaker 1: So the full statement is that photons only travel at 536 00:27:45,720 --> 00:27:50,000 Speaker 1: the speed of light as measured locally by people nearby. 537 00:27:50,040 --> 00:27:53,600 Speaker 1: In flat space, space is curved and you're far away 538 00:27:53,640 --> 00:27:56,440 Speaker 1: from an object, the rule that photons have to travel 539 00:27:56,440 --> 00:27:59,879 Speaker 1: at the speed of light no longer holds interesting. I 540 00:28:00,040 --> 00:28:02,240 Speaker 1: think what you're saying is that, like, photons have to 541 00:28:02,280 --> 00:28:05,840 Speaker 1: travel the speed of light in space right like to 542 00:28:05,920 --> 00:28:08,080 Speaker 1: the photon, it's always going at the same speed. But 543 00:28:08,520 --> 00:28:12,040 Speaker 1: you're saying you can't sort of squish and bend space itself, 544 00:28:12,240 --> 00:28:15,159 Speaker 1: which might to a someone who's looking from far away, 545 00:28:15,480 --> 00:28:17,520 Speaker 1: might make it actually go faster and slower than the 546 00:28:17,520 --> 00:28:19,639 Speaker 1: speed of light. Yeah, and it goes one step deeper 547 00:28:19,640 --> 00:28:22,320 Speaker 1: than that. And remember that you can't talk about velocity 548 00:28:22,320 --> 00:28:25,119 Speaker 1: without talking about pairs of objects. Velocity is not a 549 00:28:25,200 --> 00:28:28,240 Speaker 1: property of an object. Of ball flying through space doesn't 550 00:28:28,280 --> 00:28:31,960 Speaker 1: have a speed. It only has a speed relative to observers. 551 00:28:32,200 --> 00:28:34,320 Speaker 1: So whenever you talk about velocity, you can't think about 552 00:28:34,440 --> 00:28:36,600 Speaker 1: a ship traveling near the speed of light. You always 553 00:28:36,640 --> 00:28:39,560 Speaker 1: have to say a ship traveling at whatever speed relative 554 00:28:39,600 --> 00:28:42,160 Speaker 1: to Earth, for example. So in this case, we're talking 555 00:28:42,160 --> 00:28:46,160 Speaker 1: about photons relative to an observer nearby versus photons relative 556 00:28:46,200 --> 00:28:48,560 Speaker 1: to an observer far away. The problem is that, in 557 00:28:48,680 --> 00:28:51,680 Speaker 1: general relativity, that is the theory that tells us how 558 00:28:51,720 --> 00:28:54,600 Speaker 1: to think about the universe as it curves and bends 559 00:28:54,640 --> 00:28:58,920 Speaker 1: in response to mass, there is no well defined definition 560 00:28:59,320 --> 00:29:02,520 Speaker 1: of velocity for something that's far away. It's like you 561 00:29:02,560 --> 00:29:05,800 Speaker 1: can't even really sensibly talk about the speed of a 562 00:29:05,880 --> 00:29:08,760 Speaker 1: photon that is very far away from you. Wait, what 563 00:29:08,760 --> 00:29:10,880 Speaker 1: what do you mean? Like? I can see it, you know, 564 00:29:11,280 --> 00:29:13,480 Speaker 1: one spot from from a distance, and then I see 565 00:29:13,480 --> 00:29:17,640 Speaker 1: it in another spot from a distance a short time later. 566 00:29:17,760 --> 00:29:19,920 Speaker 1: I can you know, measure with the distance between those 567 00:29:19,960 --> 00:29:21,840 Speaker 1: two things and divide by the time. That would give 568 00:29:21,840 --> 00:29:24,160 Speaker 1: me the its speed. Yeah, that sounds straightforward, but the 569 00:29:24,200 --> 00:29:27,760 Speaker 1: problem is that you were using your local inertial reference 570 00:29:27,760 --> 00:29:30,760 Speaker 1: frame to measure the path of something that's moving through 571 00:29:31,000 --> 00:29:34,720 Speaker 1: curved space far away. So you're assuming that space is 572 00:29:34,760 --> 00:29:37,760 Speaker 1: flat between here and there, and if it isn't, if 573 00:29:37,760 --> 00:29:40,880 Speaker 1: space is curved, then the reference frame of someone else 574 00:29:41,000 --> 00:29:44,560 Speaker 1: nearby those photons would be very different, and your measurement 575 00:29:44,560 --> 00:29:48,000 Speaker 1: and velocity and there's won't agree. For example, a distant 576 00:29:48,000 --> 00:29:51,320 Speaker 1: observer will see light near a black hole travel at 577 00:29:51,320 --> 00:29:54,240 Speaker 1: all sorts of crazy speeds from less than the speed 578 00:29:54,280 --> 00:29:56,320 Speaker 1: of light all the way down to zero, but a 579 00:29:56,320 --> 00:29:58,960 Speaker 1: local observer near the black hole and near that photon 580 00:29:59,040 --> 00:30:02,120 Speaker 1: will always measure that light moving at the speed of light. 581 00:30:02,560 --> 00:30:05,400 Speaker 1: But this is more than just different reference frames having 582 00:30:05,440 --> 00:30:08,680 Speaker 1: different values. We have that in special relativity and we 583 00:30:08,720 --> 00:30:12,960 Speaker 1: know how to translate and compare, but because space is curved, 584 00:30:13,400 --> 00:30:17,240 Speaker 1: there are many different ways to compare those measurements velocities 585 00:30:17,240 --> 00:30:21,280 Speaker 1: in general relativity, So to translate between two different reference 586 00:30:21,320 --> 00:30:24,800 Speaker 1: frames and curved space, now why is that? What you 587 00:30:24,840 --> 00:30:27,720 Speaker 1: need to do in that case is compare its velocity 588 00:30:27,760 --> 00:30:30,959 Speaker 1: to your own, right, you need relative velocity, and so 589 00:30:31,040 --> 00:30:33,640 Speaker 1: you're making those measurements and so really what you're doing 590 00:30:33,720 --> 00:30:37,440 Speaker 1: is you're comparing two different vectors there, like your velocity 591 00:30:37,480 --> 00:30:40,640 Speaker 1: and its velocity, and that's something you can do if 592 00:30:40,680 --> 00:30:43,160 Speaker 1: space is flat, but it's not something that we know 593 00:30:43,200 --> 00:30:46,080 Speaker 1: how to do if space is curved. And it's useful 594 00:30:46,120 --> 00:30:48,800 Speaker 1: to think about an analogy like making a measurement on 595 00:30:48,840 --> 00:30:51,560 Speaker 1: the surface of the Earth. Say, for example, you have 596 00:30:51,680 --> 00:30:54,560 Speaker 1: two runners and they're running a race. If they're next 597 00:30:54,560 --> 00:30:56,800 Speaker 1: to each other, it's very simple to see who's faster. 598 00:30:56,920 --> 00:30:59,400 Speaker 1: They're literally next to each other. Now, imagine you take 599 00:30:59,440 --> 00:31:01,600 Speaker 1: one of the runs and one of them is in 600 00:31:01,680 --> 00:31:03,840 Speaker 1: Paris and the other one is in Cape Town, South 601 00:31:03,880 --> 00:31:06,360 Speaker 1: Africa or something. So they're like on different places in 602 00:31:06,360 --> 00:31:09,000 Speaker 1: the Earth. Now they're not really running in the same direction, right, 603 00:31:09,040 --> 00:31:11,920 Speaker 1: because the Earth is curved. One is running in one direction, 604 00:31:11,960 --> 00:31:14,040 Speaker 1: the other one is running sort of in a different direction. 605 00:31:14,280 --> 00:31:17,480 Speaker 1: So how do you compare their velocities? Right? Well, one 606 00:31:17,520 --> 00:31:19,440 Speaker 1: thing you can do is to say, well, I'm gonna 607 00:31:19,480 --> 00:31:22,600 Speaker 1: take the velocity vector of the Cape Town runner. I'm 608 00:31:22,600 --> 00:31:25,240 Speaker 1: gonna bring it over to Paris and sort of like 609 00:31:25,280 --> 00:31:27,480 Speaker 1: transported over to Paris, and then I'm going to compare 610 00:31:27,520 --> 00:31:29,640 Speaker 1: the two velocities. I mean, like, if I'm floating in 611 00:31:29,680 --> 00:31:32,320 Speaker 1: a space station looking at these two runners from space, 612 00:31:32,920 --> 00:31:35,080 Speaker 1: you just want to compare these two, right, it doesn't 613 00:31:35,080 --> 00:31:37,920 Speaker 1: matter really where you are from that perspective, You've got 614 00:31:37,920 --> 00:31:40,160 Speaker 1: to bring those vectors close to each other. But why 615 00:31:40,200 --> 00:31:41,640 Speaker 1: do I have to do that? I guess can I? 616 00:31:41,720 --> 00:31:44,880 Speaker 1: I just, for example, from space in my space station, 617 00:31:45,200 --> 00:31:48,160 Speaker 1: measure the length of the track that the American runner 618 00:31:48,200 --> 00:31:50,880 Speaker 1: is in, and then measure from space the length of 619 00:31:50,960 --> 00:31:53,400 Speaker 1: the track that the South African runners in. And then 620 00:31:53,760 --> 00:31:55,840 Speaker 1: you know, as I see that, I start the clock 621 00:31:55,880 --> 00:31:57,959 Speaker 1: when they both started running, and then I measure how 622 00:31:58,000 --> 00:32:00,960 Speaker 1: long it took to get to the side of the track. Yeah, 623 00:32:00,960 --> 00:32:03,200 Speaker 1: you could do that. You could ignore the curvage of 624 00:32:03,240 --> 00:32:05,800 Speaker 1: the Earth and just measure their velocity relative to somebody 625 00:32:05,800 --> 00:32:09,480 Speaker 1: in space. That's like, again, assuming everyone is in your 626 00:32:09,600 --> 00:32:13,280 Speaker 1: local inertial frame and that space is flat. But we 627 00:32:13,360 --> 00:32:16,680 Speaker 1: put people in this example on a curved surface as 628 00:32:16,720 --> 00:32:19,560 Speaker 1: an analogy for what happens when space is curved. But 629 00:32:19,640 --> 00:32:21,800 Speaker 1: when you're running a race, we really want the velocity 630 00:32:21,840 --> 00:32:25,520 Speaker 1: along the Earth, right, not the velocity through space, which 631 00:32:25,520 --> 00:32:27,920 Speaker 1: you one is the answer of if I brought the 632 00:32:27,920 --> 00:32:31,640 Speaker 1: Cape Town runner to Paris, who would win this race? Right? 633 00:32:31,720 --> 00:32:33,680 Speaker 1: And so the curvage of the Earth makes a difference 634 00:32:33,720 --> 00:32:37,040 Speaker 1: there you can't just ignore it, alright, So you're saying 635 00:32:37,040 --> 00:32:39,800 Speaker 1: that that it's hard to measure or compare velocities in 636 00:32:39,960 --> 00:32:43,000 Speaker 1: curve space because things kind of get kind of wonky 637 00:32:43,120 --> 00:32:45,960 Speaker 1: because spacetime is being curved. That's right, And the problem 638 00:32:46,160 --> 00:32:49,680 Speaker 1: is that how you compare those two vectors depends on 639 00:32:49,960 --> 00:32:52,880 Speaker 1: how you bring one vector close to the other vectors. 640 00:32:52,920 --> 00:32:55,120 Speaker 1: This is called parallel transport in geometry. You want to 641 00:32:55,160 --> 00:32:57,440 Speaker 1: compare two vectors, you've got to bring them near each other. 642 00:32:57,840 --> 00:32:59,880 Speaker 1: In flat space, that's not a big deal because if 643 00:33:00,080 --> 00:33:02,160 Speaker 1: move the vector from there it here doesn't change. In 644 00:33:02,240 --> 00:33:05,080 Speaker 1: curved space, the vector changes as it moves through that 645 00:33:05,120 --> 00:33:07,760 Speaker 1: curved space, and so there's an infinite number of different 646 00:33:07,760 --> 00:33:09,600 Speaker 1: ways you can do it, and the answer you get 647 00:33:09,640 --> 00:33:12,360 Speaker 1: depends on the path. So if you bring the Cape 648 00:33:12,360 --> 00:33:15,520 Speaker 1: Town Guide to Paris along one path, is vector will 649 00:33:15,560 --> 00:33:17,760 Speaker 1: be in one direction. If you do it along another path, 650 00:33:18,000 --> 00:33:20,040 Speaker 1: IS vector will be in a different direction. And so 651 00:33:20,160 --> 00:33:22,240 Speaker 1: this is all really important because it means that you 652 00:33:22,320 --> 00:33:26,920 Speaker 1: can't define the difference between those two velocity vectors across 653 00:33:27,040 --> 00:33:30,200 Speaker 1: curved space, and so that means that you can't talk 654 00:33:30,240 --> 00:33:32,600 Speaker 1: about the relative velocity of things that are really really 655 00:33:32,600 --> 00:33:36,080 Speaker 1: far apart, you can't define what happens to a photon, 656 00:33:36,280 --> 00:33:38,080 Speaker 1: and that means that the rules of special relativity and 657 00:33:38,160 --> 00:33:41,120 Speaker 1: no longer apply. So a photon moving around a black 658 00:33:41,120 --> 00:33:43,320 Speaker 1: hole could appear to have a velocity not the speed 659 00:33:43,360 --> 00:33:46,000 Speaker 1: of light, all the way down to apparently zero velocity 660 00:33:46,040 --> 00:33:48,520 Speaker 1: as it tries to climb out of that gravity. Well, right, 661 00:33:48,600 --> 00:33:50,480 Speaker 1: I think what you're saying is that if we were 662 00:33:50,560 --> 00:33:52,760 Speaker 1: to run the experiment that Crisp wants us to run, 663 00:33:52,800 --> 00:33:55,200 Speaker 1: which is like, shoot two photons and have one go 664 00:33:55,320 --> 00:33:57,680 Speaker 1: into a black hole, like, we would see one of 665 00:33:57,720 --> 00:34:01,120 Speaker 1: them just fly through space away and the other one 666 00:34:01,160 --> 00:34:03,520 Speaker 1: we would see actually like kind of stop at the 667 00:34:03,560 --> 00:34:05,440 Speaker 1: black hole, kind of like right, like it would just 668 00:34:05,600 --> 00:34:08,439 Speaker 1: stop from our point of view. From our point of view, 669 00:34:08,480 --> 00:34:12,360 Speaker 1: and according to our decision about how to measure that velocity, 670 00:34:12,719 --> 00:34:15,600 Speaker 1: somebody else looking from another perspective might have a different 671 00:34:15,640 --> 00:34:17,319 Speaker 1: definition of like, well, here's how I'm going to bring 672 00:34:17,360 --> 00:34:20,239 Speaker 1: those velocity vectors together to compare them. They might get 673 00:34:20,239 --> 00:34:22,640 Speaker 1: a different answer. What do you mean, Like if I'm 674 00:34:22,680 --> 00:34:24,600 Speaker 1: moving maybe at a different speed, but if I just 675 00:34:24,640 --> 00:34:26,120 Speaker 1: stand on the other side of the black hole, I'm 676 00:34:26,120 --> 00:34:27,560 Speaker 1: probably going to see the same thing. Right, I'm going 677 00:34:27,560 --> 00:34:29,920 Speaker 1: to see one photon keep flying off and the other 678 00:34:29,920 --> 00:34:32,200 Speaker 1: one stop at the black hole. Right, But in order 679 00:34:32,239 --> 00:34:35,200 Speaker 1: to measure the velocity of that photon, you need to 680 00:34:35,239 --> 00:34:38,600 Speaker 1: talk about how to bring its velocity vector into your 681 00:34:38,760 --> 00:34:41,200 Speaker 1: local space, and there's an infinite number of ways to 682 00:34:41,239 --> 00:34:43,319 Speaker 1: do that, and the choice you make about how to 683 00:34:43,360 --> 00:34:46,719 Speaker 1: transport that vector changes the answer. So you and I 684 00:34:46,719 --> 00:34:48,360 Speaker 1: could be right next to each other looking at the 685 00:34:48,400 --> 00:34:50,960 Speaker 1: same photon. But if you have a different definition of 686 00:34:51,000 --> 00:34:54,279 Speaker 1: basically velocity in general relativity than I do, we could 687 00:34:54,280 --> 00:34:56,799 Speaker 1: get different answers. So that's why people say it's not 688 00:34:56,920 --> 00:35:00,480 Speaker 1: well defined, because there's an infinite number of arbitrar choices 689 00:35:00,520 --> 00:35:03,000 Speaker 1: you can make that do affect your answer? All right, Well, 690 00:35:03,040 --> 00:35:05,440 Speaker 1: then what would be the answer for Chris? So you 691 00:35:05,600 --> 00:35:08,120 Speaker 1: would you see that photon move slower, the one that 692 00:35:08,160 --> 00:35:10,440 Speaker 1: goes near the heavy mass. You would see it move 693 00:35:10,520 --> 00:35:13,000 Speaker 1: slower exactly no matter where you are. You would see 694 00:35:13,000 --> 00:35:15,000 Speaker 1: it move slower than the speed of light, almost no 695 00:35:15,000 --> 00:35:17,000 Speaker 1: matter where you are. And you know, this might be 696 00:35:17,040 --> 00:35:18,880 Speaker 1: confusing to people if they think, well, how can we 697 00:35:18,960 --> 00:35:21,880 Speaker 1: not define the velocity of objects that are far away? 698 00:35:21,960 --> 00:35:25,400 Speaker 1: Like we talk about galaxies moving really really fast away 699 00:35:25,400 --> 00:35:28,080 Speaker 1: from us, and the galaxies are very far away. That's 700 00:35:28,160 --> 00:35:30,400 Speaker 1: one reason we can talk about galaxies moving away from 701 00:35:30,480 --> 00:35:33,200 Speaker 1: us faster than the speed of light. One way to 702 00:35:33,239 --> 00:35:35,799 Speaker 1: think about it is that space is expanding between us 703 00:35:35,800 --> 00:35:38,560 Speaker 1: and those galaxies. Another totally reasonable way to think about 704 00:35:38,560 --> 00:35:41,640 Speaker 1: that is to attribute that velocity actually to the objects 705 00:35:41,680 --> 00:35:44,480 Speaker 1: and not to the motion of space itself. Those are 706 00:35:44,520 --> 00:35:47,960 Speaker 1: both arbitrary but reasonable choices. And that's why we say, 707 00:35:47,960 --> 00:35:51,240 Speaker 1: like the velocity of objects isn't well defined in gr 708 00:35:51,320 --> 00:35:54,040 Speaker 1: because it requires an arbitrary choice. It's kind of like 709 00:35:54,080 --> 00:35:57,040 Speaker 1: how we've always said or set often on this podcast 710 00:35:57,040 --> 00:35:59,440 Speaker 1: and in our books. It's like if Hussain Bold can 711 00:35:59,480 --> 00:36:02,120 Speaker 1: only run so fast on land, but if there's like 712 00:36:02,280 --> 00:36:04,719 Speaker 1: new land being made between us and him, he's gonna 713 00:36:04,760 --> 00:36:07,560 Speaker 1: look like he's going faster than what he can actually run. 714 00:36:07,760 --> 00:36:10,360 Speaker 1: Or if there's if like the continent he's on is 715 00:36:10,360 --> 00:36:13,439 Speaker 1: actually moving towards us, he might appear to be moving 716 00:36:13,480 --> 00:36:17,040 Speaker 1: slower exactly. And that's the standard choice and cosmology to 717 00:36:17,120 --> 00:36:19,720 Speaker 1: think of the universe as expanding in a certain way 718 00:36:19,960 --> 00:36:22,960 Speaker 1: and to think of motion relative to that expanding space, 719 00:36:23,000 --> 00:36:25,480 Speaker 1: And that's a totally reasonable choice, and that's what we 720 00:36:25,560 --> 00:36:27,480 Speaker 1: usually do when we talk about the expansion of the 721 00:36:27,560 --> 00:36:30,360 Speaker 1: universe and the velocity of really distant objects. But you 722 00:36:30,400 --> 00:36:33,360 Speaker 1: could make other choices. As an arbitrary choice, it is 723 00:36:33,400 --> 00:36:35,279 Speaker 1: just sort of the one people typically make. You could 724 00:36:35,360 --> 00:36:38,080 Speaker 1: make other choices, which is why these velocities of very 725 00:36:38,080 --> 00:36:40,960 Speaker 1: distant objects technically not well defined. And that's why you 726 00:36:41,000 --> 00:36:43,279 Speaker 1: can end up in situations where you say things like, oh, 727 00:36:43,560 --> 00:36:46,040 Speaker 1: light is moving slower than the speed of light. It's 728 00:36:46,080 --> 00:36:49,320 Speaker 1: because velocity of far away objects is not really well defined. 729 00:36:49,440 --> 00:36:52,280 Speaker 1: If you're near a photon, it will always be moving 730 00:36:52,320 --> 00:36:55,239 Speaker 1: at the speed of light relative to you, right right, Yeah, 731 00:36:55,239 --> 00:36:57,440 Speaker 1: Like if you're falling into the black hole with the photon, 732 00:36:57,560 --> 00:36:59,839 Speaker 1: the photon would just look like it's it's moving at 733 00:36:59,840 --> 00:37:02,279 Speaker 1: the speed of light. But that's because also your time 734 00:37:02,320 --> 00:37:05,640 Speaker 1: frame is also being slowed down right exactly it's near you, 735 00:37:05,719 --> 00:37:08,960 Speaker 1: and so locally space is always flattened near you, and 736 00:37:09,040 --> 00:37:11,160 Speaker 1: so if you're with the photon, it's moving through flat 737 00:37:11,160 --> 00:37:13,719 Speaker 1: space at the speed of light. A distant observer, that's 738 00:37:13,760 --> 00:37:16,719 Speaker 1: where the problem comes in because the definition of velocity 739 00:37:16,760 --> 00:37:20,000 Speaker 1: for distant objects is bunky in general relativity, where its 740 00:37:20,040 --> 00:37:22,319 Speaker 1: Chris says, kind of confusing. I think that's the real 741 00:37:22,360 --> 00:37:25,719 Speaker 1: answer for Chris here to this question. It's kind not confusing. 742 00:37:26,560 --> 00:37:28,880 Speaker 1: All right, Well, let's get into our last question, and 743 00:37:28,960 --> 00:37:31,520 Speaker 1: this one is a little bit related. It's another question 744 00:37:31,520 --> 00:37:34,040 Speaker 1: about light and it's speed, So let's get into that. 745 00:37:34,080 --> 00:37:49,120 Speaker 1: But first let's take another quick break. All right, we 746 00:37:49,160 --> 00:37:53,600 Speaker 1: are answering listener questions and also debating UM Berkeley versus Stanford. 747 00:37:53,640 --> 00:37:56,520 Speaker 1: Apparently there's no debate, man, I mean, it's just talking 748 00:37:56,520 --> 00:38:00,840 Speaker 1: about it. But I see, well, I think there's a 749 00:38:00,880 --> 00:38:04,680 Speaker 1: debate about whether there is a debate. I think it's 750 00:38:04,719 --> 00:38:08,640 Speaker 1: only really one side of that debate. Now we we're 751 00:38:08,640 --> 00:38:11,720 Speaker 1: answering listener questions and our last question here comes from Dennis, 752 00:38:11,760 --> 00:38:14,560 Speaker 1: who has a question about the speed of light. Hello 753 00:38:14,640 --> 00:38:17,839 Speaker 1: Daniel Kay, First of all, I love your podcast. I 754 00:38:17,920 --> 00:38:21,880 Speaker 1: was wondering what is the minimal speed of light to 755 00:38:22,080 --> 00:38:26,160 Speaker 1: sort of hold a universe together? And what would happen 756 00:38:26,200 --> 00:38:30,439 Speaker 1: if a light would only have a thousand kilometers per 757 00:38:30,719 --> 00:38:35,400 Speaker 1: per second of speed? What was happened? Then? Okay, thank you? Alright, 758 00:38:35,440 --> 00:38:38,040 Speaker 1: awesome question from Dennis here about the speed of light, 759 00:38:38,440 --> 00:38:40,600 Speaker 1: and I guess this question is sort of like, because 760 00:38:41,239 --> 00:38:43,400 Speaker 1: we've talked about on this podcast before and in our 761 00:38:43,400 --> 00:38:45,520 Speaker 1: book also about the speed of light is a little 762 00:38:45,520 --> 00:38:48,000 Speaker 1: bit arbitrary, Like you can it could have it's it's 763 00:38:48,040 --> 00:38:50,879 Speaker 1: like three millions per second, but it could have been 764 00:38:50,880 --> 00:38:53,040 Speaker 1: something different. It could have been three per second or 765 00:38:53,160 --> 00:38:55,760 Speaker 1: three billion meters per second, and you could maybe still 766 00:38:55,800 --> 00:38:58,560 Speaker 1: have like a functioning universe. Yeah, we don't really know 767 00:38:58,640 --> 00:39:00,560 Speaker 1: if it could have been something else, but we don't 768 00:39:00,560 --> 00:39:03,080 Speaker 1: know why it is what it is. We have no 769 00:39:03,160 --> 00:39:06,759 Speaker 1: explanation for it being that number in particular, and that 770 00:39:06,880 --> 00:39:09,920 Speaker 1: suggests that maybe it could have been something else. And 771 00:39:09,960 --> 00:39:12,480 Speaker 1: there's lots of really interesting philosophical wrinkles there, like are 772 00:39:12,520 --> 00:39:15,000 Speaker 1: there other versions of the universe out there in the 773 00:39:15,080 --> 00:39:18,879 Speaker 1: multiverse with different speeds of light? Etcetera, etcetera. And it's 774 00:39:18,880 --> 00:39:22,360 Speaker 1: a really great question to ask, like what speeds are allowed? 775 00:39:22,440 --> 00:39:25,959 Speaker 1: Could the universe work if the speed of light was different? Yeah? 776 00:39:26,080 --> 00:39:29,520 Speaker 1: Pretty cool And something I think we discussed recently in 777 00:39:29,520 --> 00:39:31,840 Speaker 1: an podcast episode that was a little mind blowing for 778 00:39:31,880 --> 00:39:33,600 Speaker 1: me was that you told me that a light the 779 00:39:33,600 --> 00:39:36,919 Speaker 1: speed of light is not actually a fundamental like unit 780 00:39:37,040 --> 00:39:39,319 Speaker 1: or value of the universe. That's right, The speed of 781 00:39:39,400 --> 00:39:42,920 Speaker 1: light has units to it, right, meters per second, and 782 00:39:42,960 --> 00:39:46,160 Speaker 1: so the actual number is really arbitrary because it depends 783 00:39:46,200 --> 00:39:48,960 Speaker 1: on the units. So when we talk about the construction 784 00:39:49,040 --> 00:39:52,280 Speaker 1: of the universe and the parameters that influence the way 785 00:39:52,280 --> 00:39:54,960 Speaker 1: that it is, we try to focus on numbers that 786 00:39:55,040 --> 00:39:59,000 Speaker 1: don't have units to them, dimensionless numbers, numbers like the 787 00:39:59,000 --> 00:40:03,040 Speaker 1: cosmological constant which affects the expansion of the universe, or 788 00:40:03,080 --> 00:40:06,080 Speaker 1: the ratio of masses of the electron to the muan, 789 00:40:06,239 --> 00:40:08,600 Speaker 1: for example. And the speed of light does factor in 790 00:40:08,840 --> 00:40:11,680 Speaker 1: because it's part of what we call the fine structure constant, 791 00:40:11,920 --> 00:40:14,880 Speaker 1: which combines a bunch of these different constants blanks constant, 792 00:40:14,880 --> 00:40:18,160 Speaker 1: the speed of light, strength of the electromagnetic force. Yeah, 793 00:40:18,239 --> 00:40:20,200 Speaker 1: like this like like a ratio, right, like the speed 794 00:40:20,239 --> 00:40:24,960 Speaker 1: of light divided by how quickly Berkeley students think two 795 00:40:25,000 --> 00:40:30,359 Speaker 1: really big numbers. But I think the idea is that 796 00:40:30,440 --> 00:40:33,520 Speaker 1: generally speaking, like you know, how fast light travels through 797 00:40:33,520 --> 00:40:35,560 Speaker 1: space is sort of like a fundamental property of the 798 00:40:35,640 --> 00:40:39,600 Speaker 1: universe that we currently can't really explain. Like it seems arbitrary, yeah, 799 00:40:39,640 --> 00:40:41,759 Speaker 1: and it might be that it bubbles up from a 800 00:40:41,800 --> 00:40:44,640 Speaker 1: deeper understanding of the nature of space time. You know 801 00:40:44,760 --> 00:40:47,600 Speaker 1: if space, for example, is a quantum foam of little 802 00:40:47,640 --> 00:40:50,759 Speaker 1: space pixels linked together by tiny wormholes. It could be 803 00:40:50,800 --> 00:40:55,480 Speaker 1: that some property of those wormholes influences how information propagates 804 00:40:55,480 --> 00:40:57,880 Speaker 1: from one space pixel to the other, and that determines 805 00:40:57,920 --> 00:41:00,520 Speaker 1: the speed of light. We just don't know the sketch 806 00:41:00,560 --> 00:41:02,840 Speaker 1: from maybe how you could get an answer to what 807 00:41:02,880 --> 00:41:04,759 Speaker 1: the speed of light is, or it could just be 808 00:41:04,960 --> 00:41:07,840 Speaker 1: a totally arbitrary It could be that as universes are created, 809 00:41:07,880 --> 00:41:10,719 Speaker 1: to some random process that sets these parameters, and this 810 00:41:10,760 --> 00:41:13,120 Speaker 1: is the one that we got, Like you get three 811 00:41:13,160 --> 00:41:19,359 Speaker 1: hund a million per second, you get second exactly. And 812 00:41:19,440 --> 00:41:21,840 Speaker 1: it's fun to think about what the universe would look like. 813 00:41:21,880 --> 00:41:24,319 Speaker 1: And I love the way Dennis posed this question, which 814 00:41:24,360 --> 00:41:27,280 Speaker 1: is like could the universe come together with the minimum 815 00:41:27,280 --> 00:41:29,840 Speaker 1: speed of light for a universe to function? Yeah, it 816 00:41:29,840 --> 00:41:32,160 Speaker 1: seems like he has he has a two part question. Actually, 817 00:41:32,160 --> 00:41:34,680 Speaker 1: the first part is like, could we have a universe 818 00:41:34,680 --> 00:41:37,120 Speaker 1: with a slower speed of light? And what would be 819 00:41:37,160 --> 00:41:39,919 Speaker 1: the slowest speed of light that a universe would still 820 00:41:40,000 --> 00:41:42,560 Speaker 1: hold together? Which is sort of an interesting way to 821 00:41:42,560 --> 00:41:44,719 Speaker 1: put it, like could with the universe fall apart if 822 00:41:44,880 --> 00:41:46,840 Speaker 1: the speed of light was slower. Well, you know, the 823 00:41:46,880 --> 00:41:49,400 Speaker 1: way I think about this is in terms of light cones, 824 00:41:49,760 --> 00:41:52,240 Speaker 1: something we talked about in the podcast once, which tells 825 00:41:52,280 --> 00:41:55,719 Speaker 1: you what portion of the future of the universe you 826 00:41:55,719 --> 00:41:58,520 Speaker 1: can influence and which portion of the past of the 827 00:41:58,600 --> 00:42:03,360 Speaker 1: universe influences you. Because we have this maximum speed of information, 828 00:42:03,480 --> 00:42:06,480 Speaker 1: it means that, for example, you can't affect things in 829 00:42:06,480 --> 00:42:09,359 Speaker 1: a neighboring galaxy that are happening right now. You made 830 00:42:09,360 --> 00:42:12,120 Speaker 1: a decision about something you wanted to happen in Andromeda, 831 00:42:12,200 --> 00:42:14,880 Speaker 1: it would take millions of years for that decision to 832 00:42:14,920 --> 00:42:18,360 Speaker 1: have any effect. That your light cone fraction of the 833 00:42:18,440 --> 00:42:21,239 Speaker 1: universe in the future that you can influence, and the 834 00:42:21,280 --> 00:42:23,680 Speaker 1: size of that cone, the slope of that cone is 835 00:42:23,719 --> 00:42:25,800 Speaker 1: determined by the speed of light. So the speed of 836 00:42:25,840 --> 00:42:28,840 Speaker 1: light was much much faster than you could influence Andromeda 837 00:42:28,880 --> 00:42:31,760 Speaker 1: maybe tomorrow. If the speed of light was much much slower, 838 00:42:31,840 --> 00:42:34,840 Speaker 1: that might take billions of years to affect Andromeda instead 839 00:42:34,880 --> 00:42:37,279 Speaker 1: of millions. And so the size of that cone, the 840 00:42:37,360 --> 00:42:40,359 Speaker 1: narrowness of that cone, is determined by the speed of light. Yeah, 841 00:42:40,400 --> 00:42:42,640 Speaker 1: I mean it definitely, it would change the universe. But 842 00:42:42,680 --> 00:42:44,960 Speaker 1: I think his maybe question was more like, is there 843 00:42:45,040 --> 00:42:47,200 Speaker 1: something in the equations of the universe that we know 844 00:42:47,239 --> 00:42:50,280 Speaker 1: about right now that if I, you know, start dialing 845 00:42:50,320 --> 00:42:52,920 Speaker 1: the speed of light down, would at some point equations 846 00:42:53,000 --> 00:42:57,479 Speaker 1: fail or become incoherent or illogical. Or is it really 847 00:42:57,520 --> 00:42:59,439 Speaker 1: the fact that, you know, the speed of light could 848 00:42:59,440 --> 00:43:02,120 Speaker 1: be one centimeter per second and you could still have 849 00:43:02,239 --> 00:43:04,719 Speaker 1: a functioning universe. Yeah, as far as I know, there 850 00:43:04,880 --> 00:43:08,080 Speaker 1: is no minimum speed. You would have completely different kind 851 00:43:08,120 --> 00:43:10,920 Speaker 1: of universe. It would feel very, very different, and it 852 00:43:11,000 --> 00:43:14,240 Speaker 1: might affect the structure of matter. You know, the orbits 853 00:43:14,239 --> 00:43:16,840 Speaker 1: of the electrons, for example, are affected by the speed 854 00:43:16,880 --> 00:43:18,960 Speaker 1: of light, and so you might not get hydrogen, you 855 00:43:19,040 --> 00:43:22,000 Speaker 1: might get weird other forms of matter. But you would 856 00:43:22,040 --> 00:43:24,480 Speaker 1: still have a universe even with a much slower or 857 00:43:24,600 --> 00:43:27,279 Speaker 1: much faster speed of light. I see, like if you 858 00:43:27,360 --> 00:43:29,960 Speaker 1: change the rules, the atoms and the corks and all 859 00:43:29,960 --> 00:43:34,040 Speaker 1: that would just played played differently, but they could still play, 860 00:43:34,160 --> 00:43:37,280 Speaker 1: They could still play exactly, and they would play differently, 861 00:43:37,360 --> 00:43:39,760 Speaker 1: And the consequences of that are really hard to imagine 862 00:43:39,800 --> 00:43:42,439 Speaker 1: and difficult to calculate. Also, you know, we don't really 863 00:43:42,440 --> 00:43:44,680 Speaker 1: even have a great theory for like how corks come 864 00:43:44,719 --> 00:43:47,920 Speaker 1: together to make protons and neutrons because it involves the 865 00:43:47,960 --> 00:43:50,360 Speaker 1: strong force, which is a real pain to calculate. And 866 00:43:50,360 --> 00:43:53,160 Speaker 1: so if the balance of all those forces changes, then 867 00:43:53,200 --> 00:43:56,120 Speaker 1: a lot of things that are difficult to calculate would 868 00:43:56,160 --> 00:43:58,480 Speaker 1: be different. So the whole universe could be very different. 869 00:43:58,520 --> 00:44:00,399 Speaker 1: But you know, if the universe doesn't change that much, 870 00:44:00,480 --> 00:44:03,200 Speaker 1: if the speed of light goes down by fifty or something, 871 00:44:03,480 --> 00:44:06,360 Speaker 1: I think you'd largely get the same universe, but it 872 00:44:06,360 --> 00:44:09,160 Speaker 1: would feel different, like you could see less of the 873 00:44:09,280 --> 00:44:12,680 Speaker 1: universe out there, like our little bubble. The observable universe 874 00:44:12,960 --> 00:44:15,680 Speaker 1: also depends on the speed of light, right well, but 875 00:44:15,719 --> 00:44:18,200 Speaker 1: I think it's also maybe deeper, perhaps than just what 876 00:44:18,239 --> 00:44:20,239 Speaker 1: we can see, because the speed of light doesn't just 877 00:44:20,320 --> 00:44:23,200 Speaker 1: affect light and photons. It also sort of the term 878 00:44:23,280 --> 00:44:26,040 Speaker 1: is how fast some of these fundamental particles can move, right, 879 00:44:26,440 --> 00:44:29,240 Speaker 1: and also kind of like the range of their effect, 880 00:44:29,360 --> 00:44:31,560 Speaker 1: right Like I'm thinking some of the force particles, if 881 00:44:31,560 --> 00:44:35,120 Speaker 1: they could move faster or slower than there there, it 882 00:44:35,160 --> 00:44:37,160 Speaker 1: wouldn't be a strong perhaps, that's certainly true. And the 883 00:44:37,160 --> 00:44:39,640 Speaker 1: speed of light I think most directly affects the strength 884 00:44:39,680 --> 00:44:43,040 Speaker 1: of the electromagnetic interaction because it goes directly into the 885 00:44:43,040 --> 00:44:46,880 Speaker 1: fine structure constant, which appears in the coupling of photons 886 00:44:46,880 --> 00:44:50,360 Speaker 1: to electrons and photons to other charge particles. So the 887 00:44:50,360 --> 00:44:52,759 Speaker 1: speed of light was different, it would change also sort 888 00:44:52,760 --> 00:44:57,120 Speaker 1: of the relative strength of electromagnetism to the other forces. 889 00:44:57,280 --> 00:44:59,560 Speaker 1: All right, so, um, you said it would be different. 890 00:44:59,719 --> 00:45:01,640 Speaker 1: So what are some of the ways that the universe 891 00:45:01,680 --> 00:45:04,080 Speaker 1: would be different if the speed of light was slower. Well, 892 00:45:04,080 --> 00:45:06,359 Speaker 1: if the universe was different, if the speed of light 893 00:45:06,440 --> 00:45:09,120 Speaker 1: was slower, we couldn't have as large as structure forming 894 00:45:09,200 --> 00:45:12,360 Speaker 1: in the universe. Like, in order to have a structure form, 895 00:45:12,719 --> 00:45:15,480 Speaker 1: you need to have information go back and forth across it. 896 00:45:15,800 --> 00:45:19,080 Speaker 1: You know, for a planet, for example, to coalesce gravitationally, 897 00:45:19,640 --> 00:45:21,759 Speaker 1: you need information to propagate from one side of the 898 00:45:21,800 --> 00:45:23,600 Speaker 1: planet to the other for it to be like a 899 00:45:23,719 --> 00:45:27,200 Speaker 1: single object. You mean, like gravity. Even the force of 900 00:45:27,239 --> 00:45:30,200 Speaker 1: gravity has a speed limit, and that speed limit is 901 00:45:30,200 --> 00:45:31,799 Speaker 1: the same as the speed of light. Yeah. So if 902 00:45:31,800 --> 00:45:34,760 Speaker 1: we're talking about like the speed of information through the universe, 903 00:45:35,080 --> 00:45:37,480 Speaker 1: then if you're cutting the speed of information down, then 904 00:45:37,520 --> 00:45:42,280 Speaker 1: gravity also transmits its information more slowly. Right, you would 905 00:45:42,320 --> 00:45:45,840 Speaker 1: be basically slowing down gravity too. Yeah, you would be 906 00:45:45,880 --> 00:45:48,520 Speaker 1: slowing down gravity and you would be limiting gravity in 907 00:45:48,560 --> 00:45:50,719 Speaker 1: the size of the thing that it can build. You know, 908 00:45:50,760 --> 00:45:53,239 Speaker 1: we think that there's like a biggest structure that can 909 00:45:53,280 --> 00:45:56,360 Speaker 1: exist in the universe because it takes time for gravity 910 00:45:56,400 --> 00:45:59,800 Speaker 1: to pull things together, and the universe hasn't existed for 911 00:45:59,840 --> 00:46:02,200 Speaker 1: that long, so you know, the universe has been around 912 00:46:02,239 --> 00:46:05,280 Speaker 1: fourteen billion years. That means you can't have a structure 913 00:46:05,440 --> 00:46:08,480 Speaker 1: that's like fifty billion light years wide because it just 914 00:46:08,560 --> 00:46:10,360 Speaker 1: hasn't been time for like one side of it to 915 00:46:10,400 --> 00:46:13,560 Speaker 1: coordinate with the other side and like come into equilibrium 916 00:46:13,560 --> 00:46:15,480 Speaker 1: with it. So there's a limit there on the biggest 917 00:46:15,480 --> 00:46:17,360 Speaker 1: thing you can make, and that depends on the speed 918 00:46:17,360 --> 00:46:19,760 Speaker 1: of light. Right, It's like trying to bring your kids together. 919 00:46:19,920 --> 00:46:22,920 Speaker 1: If you're really slow person, you can't like if you 920 00:46:22,960 --> 00:46:26,160 Speaker 1: slow down gravity, Like gravity would be trying to pull 921 00:46:26,239 --> 00:46:29,720 Speaker 1: all those distant galaxies together, but maybe by the time 922 00:46:29,760 --> 00:46:33,000 Speaker 1: it acts that the galaxies are long gone. Yeah. Or say, 923 00:46:33,040 --> 00:46:35,719 Speaker 1: for example, you're trying to organize a family reunion. You 924 00:46:35,719 --> 00:46:37,759 Speaker 1: can get in touch with much more distant relatives if 925 00:46:37,800 --> 00:46:40,360 Speaker 1: you can email them rather than having to send snail 926 00:46:40,400 --> 00:46:42,480 Speaker 1: mail or send a pony. Right, if you can only 927 00:46:42,480 --> 00:46:44,560 Speaker 1: send a pony and you can organize a much more 928 00:46:44,600 --> 00:46:47,640 Speaker 1: local family reunion, whereas if you can email people, you 929 00:46:47,640 --> 00:46:50,440 Speaker 1: can get people from Singapore and people from Australia to 930 00:46:50,560 --> 00:46:53,480 Speaker 1: come to your party. And so in that way, the 931 00:46:53,640 --> 00:46:56,080 Speaker 1: universe would be sort of more local if the speed 932 00:46:56,080 --> 00:46:58,680 Speaker 1: of light was smaller, right, Although I do know you, Daniel, 933 00:46:58,719 --> 00:47:01,120 Speaker 1: and I know that a family union it would be 934 00:47:01,320 --> 00:47:03,920 Speaker 1: you would organize it with ponies so that it maybe 935 00:47:05,719 --> 00:47:07,680 Speaker 1: together as well. Like I put it on the back 936 00:47:07,719 --> 00:47:10,000 Speaker 1: of an anteater. What's the problem you didn't get the invitation? 937 00:47:12,480 --> 00:47:14,080 Speaker 1: Should have put it on the back of the tree. 938 00:47:14,239 --> 00:47:17,680 Speaker 1: Banana's slug. But it's not just that it doesn't just 939 00:47:17,760 --> 00:47:20,640 Speaker 1: affect the structure of the universe, right, Like if you 940 00:47:20,640 --> 00:47:24,080 Speaker 1: slow down, gravity would also affect relativity to right, Yeah, 941 00:47:24,120 --> 00:47:27,400 Speaker 1: a lot of the really weird effects from relativity times 942 00:47:27,440 --> 00:47:30,840 Speaker 1: slowing down and things getting contracted, all that kind of stuff. 943 00:47:31,160 --> 00:47:34,120 Speaker 1: We never see those effects because they only happen when 944 00:47:34,160 --> 00:47:37,279 Speaker 1: you're going at very very high speeds relative to something else. 945 00:47:37,640 --> 00:47:39,239 Speaker 1: So that's why it took us a long time to 946 00:47:39,239 --> 00:47:42,000 Speaker 1: even discover that it's part of reality. But if the 947 00:47:42,040 --> 00:47:44,560 Speaker 1: speed of light was slower, if it was like closer 948 00:47:44,640 --> 00:47:47,680 Speaker 1: to human speeds, or speeds we could achieve on Earth, 949 00:47:47,920 --> 00:47:49,959 Speaker 1: then we might have noticed these things because you would 950 00:47:49,960 --> 00:47:51,560 Speaker 1: be able to see them, and we might have like 951 00:47:52,000 --> 00:47:55,920 Speaker 1: intuition for relativity would like make sense to us in 952 00:47:55,920 --> 00:47:58,439 Speaker 1: a way that right now it doesn't. Well, I wonder though, 953 00:47:58,800 --> 00:48:02,400 Speaker 1: like if you slow down gravity and lights and basically 954 00:48:02,440 --> 00:48:05,239 Speaker 1: how everything can propagate in the universe, wouldn't sort of 955 00:48:05,239 --> 00:48:08,560 Speaker 1: time also slow down or wouldn't it feel slower as well, 956 00:48:09,560 --> 00:48:11,560 Speaker 1: to the point where you know it's almost like if 957 00:48:11,600 --> 00:48:13,440 Speaker 1: you're near a black hole, you know your time is 958 00:48:13,480 --> 00:48:15,760 Speaker 1: moving slower, but you don't notice it. It's a great question, 959 00:48:15,800 --> 00:48:17,160 Speaker 1: and this sort of goes to the heart of why 960 00:48:17,200 --> 00:48:21,280 Speaker 1: we talk about dimensionless constants instead of dimension full constants 961 00:48:21,360 --> 00:48:23,960 Speaker 1: like the speed of light, because for example, you could 962 00:48:24,040 --> 00:48:25,960 Speaker 1: change the speed of light, but then if you tweaked 963 00:48:26,000 --> 00:48:28,520 Speaker 1: a bunch of other numbers at the same time, nothing 964 00:48:28,600 --> 00:48:31,440 Speaker 1: effectively would change in the universe. I think that's what 965 00:48:31,480 --> 00:48:33,520 Speaker 1: you're talking about, if you tweaked a bunch of these 966 00:48:33,600 --> 00:48:35,800 Speaker 1: numbers in such a way that none of the dimension 967 00:48:35,920 --> 00:48:38,680 Speaker 1: list constants change. For example, if you change the speed 968 00:48:38,719 --> 00:48:41,440 Speaker 1: of light, but you also change planks constant, and you 969 00:48:41,600 --> 00:48:44,480 Speaker 1: change the strength of the electromagnetic force, and you wouldn't 970 00:48:44,480 --> 00:48:47,200 Speaker 1: notice anything because you have look no absolute ruler to 971 00:48:47,239 --> 00:48:49,160 Speaker 1: compare it to. It's sort of like if you got 972 00:48:49,200 --> 00:48:52,879 Speaker 1: bigger and your ruler got bigger, you wouldn't notice any difference, right, Yeah, 973 00:48:52,880 --> 00:48:54,080 Speaker 1: I think you know what I mean. It's like if 974 00:48:54,120 --> 00:48:55,879 Speaker 1: you slow down the speed of light and slow down 975 00:48:55,920 --> 00:48:59,279 Speaker 1: gravity put in that also maybe affect how fast you 976 00:48:59,280 --> 00:49:02,920 Speaker 1: can think. Would you technically be thinking slower? Oh? Your 977 00:49:02,960 --> 00:49:06,239 Speaker 1: perception of time? Oh that's fascinating from a neurobiological point 978 00:49:06,280 --> 00:49:08,640 Speaker 1: of view, that's a great question. I don't know that 979 00:49:08,680 --> 00:49:10,920 Speaker 1: our thinking, though, is limited by the speed of light. 980 00:49:10,960 --> 00:49:13,200 Speaker 1: I think it's more affected by whether you went to 981 00:49:13,200 --> 00:49:18,560 Speaker 1: Berkeley or Stanford. No, that's a great question. I don't 982 00:49:18,560 --> 00:49:20,719 Speaker 1: know the answer to that. Whether the speed of your 983 00:49:20,760 --> 00:49:23,560 Speaker 1: brain is actually affected by the speed of light, and 984 00:49:23,560 --> 00:49:26,960 Speaker 1: whether I like our internal sense of time is affected 985 00:49:26,960 --> 00:49:28,799 Speaker 1: by the speed of light. I suspect that it isn't 986 00:49:28,840 --> 00:49:32,160 Speaker 1: that they're biological processes are very very slow. But I'm 987 00:49:32,160 --> 00:49:34,840 Speaker 1: really just speculating there. Well, but I mean chemical reactions 988 00:49:34,840 --> 00:49:37,879 Speaker 1: in your brain depend on the electromagnetic force, right, which 989 00:49:37,880 --> 00:49:40,319 Speaker 1: would be slower as well. Yeah, that's true. Those bonds 990 00:49:40,360 --> 00:49:42,560 Speaker 1: would have a different strength. We'll ask Katie Golden next 991 00:49:42,560 --> 00:49:46,120 Speaker 1: time she's on, since she's an expert. She went to 992 00:49:46,239 --> 00:49:54,400 Speaker 1: Harvard East Coast. West Coast just got complicated, all right, Well, 993 00:49:54,440 --> 00:49:57,680 Speaker 1: at least team West Coast is representing today. That's right. 994 00:49:57,920 --> 00:50:02,320 Speaker 1: We should unite against the true enemy, Annual the East Coast. 995 00:50:02,920 --> 00:50:05,560 Speaker 1: All right, Well, it also might have a very direct 996 00:50:05,600 --> 00:50:08,480 Speaker 1: impact on our everyday lives if the speed of light 997 00:50:08,560 --> 00:50:12,359 Speaker 1: was slower, as specifically as you're listening to this podcast, right, Yeah, 998 00:50:12,440 --> 00:50:14,839 Speaker 1: the Internet would be slower if the speed of light 999 00:50:14,920 --> 00:50:17,239 Speaker 1: was slower. We relied these days on being able to 1000 00:50:17,239 --> 00:50:22,040 Speaker 1: like stream HD videos from around the world, downloading gigabyte 1001 00:50:22,040 --> 00:50:25,680 Speaker 1: files from Australia, etcetera. But the Internet moves at the 1002 00:50:25,719 --> 00:50:28,360 Speaker 1: speed of light and so like the bandwidth would be 1003 00:50:28,360 --> 00:50:31,080 Speaker 1: the same, but the latency would be longer. Like if 1004 00:50:31,120 --> 00:50:33,640 Speaker 1: you wanted to pin a computer in Australia and the 1005 00:50:33,680 --> 00:50:36,480 Speaker 1: speed of light was a thousand kilometers per second instead 1006 00:50:36,480 --> 00:50:38,879 Speaker 1: of three hundred million meters per second, then you would 1007 00:50:38,880 --> 00:50:42,040 Speaker 1: notice the different About half of our listeners are going 1008 00:50:42,160 --> 00:50:43,880 Speaker 1: and that's not a universe I want to live in. 1009 00:50:44,960 --> 00:50:47,839 Speaker 1: Forget it. Let's not even dwell on that everybody wants 1010 00:50:47,880 --> 00:50:49,239 Speaker 1: to live in the universe where the speed of light 1011 00:50:49,320 --> 00:50:51,960 Speaker 1: is faster and they get their downloads more quickly. Yeah, 1012 00:50:52,000 --> 00:50:56,120 Speaker 1: we all want optical fiber at the current speed. All right, Well, 1013 00:50:56,120 --> 00:50:58,920 Speaker 1: I think that answers the question for Dennis. There is 1014 00:50:59,000 --> 00:51:02,040 Speaker 1: no minimum speed of light that would hold the universe together. 1015 00:51:02,200 --> 00:51:04,719 Speaker 1: We could literally be like point zero zero zero zero, 1016 00:51:04,840 --> 00:51:07,000 Speaker 1: there is zero one per second, and you could still 1017 00:51:07,000 --> 00:51:10,080 Speaker 1: have a universe. It just would be super duper different. Yes, 1018 00:51:10,160 --> 00:51:12,799 Speaker 1: in ways that are probably impossible to predict. So hey, 1019 00:51:12,880 --> 00:51:15,719 Speaker 1: let's give it a try and find out. No, I 1020 00:51:15,760 --> 00:51:19,600 Speaker 1: want my fast internet, Daniel, I want my family reunions tomorrow. 1021 00:51:20,280 --> 00:51:22,880 Speaker 1: All right, Well, thank you to all of our question askers. 1022 00:51:23,080 --> 00:51:25,320 Speaker 1: We hope that was interesting for all of us. I 1023 00:51:25,360 --> 00:51:28,080 Speaker 1: think it was interestingful. It makes you kind of think about, 1024 00:51:28,400 --> 00:51:30,279 Speaker 1: you know, how the universe could have been different, in 1025 00:51:30,360 --> 00:51:32,600 Speaker 1: the Earth could have been different, all these interesting what 1026 00:51:32,680 --> 00:51:35,640 Speaker 1: if questions, And sometimes the hardest question is the deepest ones, 1027 00:51:35,680 --> 00:51:38,400 Speaker 1: the most insightful ones are the ones that everybody asks. 1028 00:51:38,440 --> 00:51:40,839 Speaker 1: You don't have to be an academic physicist or a 1029 00:51:40,840 --> 00:51:44,040 Speaker 1: working cartoonist to think deeply about the universe and ask 1030 00:51:44,239 --> 00:51:47,959 Speaker 1: fascinating questions, So please engage your brain and think about 1031 00:51:47,960 --> 00:51:49,799 Speaker 1: the universe. And if you have a question you don't 1032 00:51:49,800 --> 00:51:51,520 Speaker 1: know the answer to, don't be shy to write to 1033 00:51:51,640 --> 00:51:54,239 Speaker 1: us two questions at Daniel and Jorge dot com. Yes, 1034 00:51:54,280 --> 00:51:57,600 Speaker 1: and there's your questions, even if they are a little confusing. 1035 00:52:00,040 --> 00:52:02,400 Speaker 1: Hope you enjoyed that. Thanks for joining us, See you 1036 00:52:02,440 --> 00:52:12,880 Speaker 1: next time. Thanks for listening, and remember that Daniel and 1037 00:52:12,960 --> 00:52:16,240 Speaker 1: Jorge explained The Universe is a production of I Heart Radio. 1038 00:52:16,640 --> 00:52:19,239 Speaker 1: Or more podcast from my heart Radio visit the I 1039 00:52:19,440 --> 00:52:23,080 Speaker 1: heart Radio app, Apple Podcasts, or wherever you listen to 1040 00:52:23,160 --> 00:52:24,160 Speaker 1: your favorite shows.