WEBVTT - The Silurian Hypothesis 0:00:03.040 --> 0:00:05.280 Welcome to Stuff to Blow Your Mind, the production of 0:00:05.360 --> 0:00:14.800 My Heart Radio. Hey, welcome to Stuff to Blow Your Mind. 0:00:14.960 --> 0:00:18.439 My name is Robert Lamb, and I'm Joe McCormick. And 0:00:18.520 --> 0:00:21.800 today we're going to be talking about a subject that 0:00:21.840 --> 0:00:24.000 I've actually had on the radar for a while. This 0:00:24.079 --> 0:00:27.639 is something that was making the rounds on science blogs 0:00:27.680 --> 0:00:30.720 a few years back, and it has been suggested by 0:00:30.760 --> 0:00:33.159 a number of different listeners. So I'm glad we're finally 0:00:33.159 --> 0:00:35.760 coming around to it. I think I had some hesitation 0:00:35.840 --> 0:00:37.879 for a while that I want to briefly explain right 0:00:37.920 --> 0:00:40.920 at the beginning here. But today we're gonna be talking 0:00:40.960 --> 0:00:46.239 about an idea known as the Silurian hypothesis. Uh. And 0:00:46.360 --> 0:00:49.280 just to give you a little bit of background knowledge, 0:00:49.280 --> 0:00:52.560 we spent several minutes before recording today trying to look 0:00:52.640 --> 0:00:56.280 up how they pronounced Silurian on Doctor Who, because I 0:00:56.360 --> 0:00:58.680 was like, sure they might use some kind of British 0:00:58.720 --> 0:01:03.720 English variation where they a Silurian, but but a last 0:01:03.800 --> 0:01:06.280 we could not ever get the doctor to say it right. 0:01:06.319 --> 0:01:08.959 I watched I think an entire scene where one of 0:01:08.959 --> 0:01:12.640 the more recent doctors was chatting with us Silurian or 0:01:12.800 --> 0:01:16.280 Silurian out out of your will, and they they it 0:01:16.360 --> 0:01:17.800 was like they were trying not to say it, like 0:01:17.840 --> 0:01:20.559 if they said it, one would would pop up and 0:01:20.560 --> 0:01:23.080 and crawl out of the screen or something they used 0:01:23.120 --> 0:01:25.800 they referred to another alien race. There wasn't even in 0:01:25.840 --> 0:01:27.760 the scene, and I don't even think was part of 0:01:27.760 --> 0:01:31.400 that episode. And then in all these other terms. But yeah, 0:01:31.400 --> 0:01:33.760 they were just trying to mess with me. So this 0:01:33.840 --> 0:01:36.800 is a topic that I have been interested in covering 0:01:37.000 --> 0:01:39.760 for quite a while. It's it's been a few years now, 0:01:40.120 --> 0:01:43.520 But Rob, when you suggested it, I realized that I'd 0:01:43.560 --> 0:01:46.679 always been hesitating and not wanting to quite go ahead 0:01:46.720 --> 0:01:49.240 with it. And I think I realized the reason for that, 0:01:49.320 --> 0:01:52.640 which is that when I saw people mentioning this paper 0:01:52.760 --> 0:01:55.480 on the internet, it was clear to me that a 0:01:55.520 --> 0:01:59.400 lot of them were getting exactly the wrong takeaway from it, 0:01:59.440 --> 0:02:02.560 Like they were matching onto a very shallow understanding of 0:02:02.600 --> 0:02:06.080 the concept and and running off in a in a 0:02:06.200 --> 0:02:09.480 very different direction than the authors intended. Not only a 0:02:09.480 --> 0:02:13.000 different direction than they intend, but a direction they specifically 0:02:13.080 --> 0:02:16.040 say do not go in, and specifically say that they 0:02:16.040 --> 0:02:19.720 are not trying to to make Yeah. Uh, so to 0:02:19.720 --> 0:02:23.120 to clarify what we're talking about here. The Silurian Hypothesis 0:02:23.120 --> 0:02:27.080 paper begins with a fascinating question, in the words of 0:02:27.120 --> 0:02:31.520 the author's quote, if an industrial civilization had existed on 0:02:31.639 --> 0:02:35.480 Earth many millions of years prior to our own era, 0:02:36.080 --> 0:02:38.840 what traces would it have left and would they be 0:02:39.000 --> 0:02:42.440 detectable today? That that's the question at the heart of 0:02:42.480 --> 0:02:46.480 this paper. And obviously this is a tantalizing premise. You know, 0:02:46.480 --> 0:02:50.799 it sets your mind racing with images of impossibly weird organisms, 0:02:50.800 --> 0:02:54.639 you know, like land dwelling octopi and stuff in the 0:02:54.760 --> 0:02:57.160 in their own weird cities, and and what kind of 0:02:57.160 --> 0:02:59.880 technology would they have? Things that are as alien as 0:02:59.880 --> 0:03:03.760 anything you could imagine on another planet, except they would 0:03:03.760 --> 0:03:07.960 have all been from here, native to planet Earth, dating 0:03:08.000 --> 0:03:12.080 back millions of years into prehistory. But while this is 0:03:12.120 --> 0:03:16.959 a really attractive imaginative exercise, I think the first order 0:03:17.000 --> 0:03:19.200 of business when talking about this subject is to be 0:03:19.240 --> 0:03:23.440 clear that the Silurian Hypothesis paper is about coming up 0:03:23.480 --> 0:03:29.240 with a framework for detecting physical traces of industrial civilizations 0:03:29.280 --> 0:03:33.160 and understanding how long those traces last. So it's about 0:03:33.480 --> 0:03:36.000 trying to say, what are the right questions to ask 0:03:36.080 --> 0:03:38.200 when you're when you're looking at a planet and saying, 0:03:38.240 --> 0:03:40.680 how could we tell if there had been a civilization 0:03:40.720 --> 0:03:43.040 on this planet a long time ago? It is not 0:03:43.320 --> 0:03:46.760 a paper arguing that there was in fact a lost 0:03:46.800 --> 0:03:51.080 civilization deep in Earth's past. So it's not evidence for 0:03:51.160 --> 0:03:56.120 lizard men, ancient aliens, Graham Hancock, junk Atlantis, or any 0:03:56.160 --> 0:03:59.120 of that stuff. But I would say in its true form, 0:03:59.280 --> 0:04:04.040 it is a really interesting question. Yeah, And at heart 0:04:04.120 --> 0:04:06.800 this episode is is not going to be about scientific 0:04:06.840 --> 0:04:09.360 evidence for lizard men civilizations in the Hollow Earth. So 0:04:09.400 --> 0:04:11.200 if you're looking for that, this is this is not 0:04:11.240 --> 0:04:13.600 the episode for you. But yeah, what I love about 0:04:13.640 --> 0:04:15.600 it is that it takes this sort of fantastic idea 0:04:15.640 --> 0:04:19.560 and then examines it reasonably, and that examination eliminates some 0:04:19.720 --> 0:04:25.919 very interesting geologic, climatic, and astrophysical considerations, So you know, 0:04:25.960 --> 0:04:30.279 setting aside pseudoscience and pseudo archaeology here. But on the 0:04:30.279 --> 0:04:32.960 other hand, I think if you if you're looking for 0:04:33.000 --> 0:04:35.840 some sci fi fund this topic in this episode will 0:04:35.880 --> 0:04:40.239 also still engage you. Um, but it is interesting how 0:04:40.960 --> 0:04:43.320 from a certain perspective you can imagine people being drawn 0:04:43.360 --> 0:04:45.640 into it by just sort of this sci fi idea, 0:04:46.120 --> 0:04:49.440 this idea that does lean lend itself well to sort 0:04:49.440 --> 0:04:53.800 of conspiracy theorist mindsets, and then realizing, actually, this paper 0:04:54.000 --> 0:04:58.440 is about geology and UH and U and the last 0:04:58.520 --> 0:05:01.560 year of our planet and also, oh, I guess kind 0:05:01.560 --> 0:05:03.560 of you know, in many cases, kind of a downbeat 0:05:03.920 --> 0:05:09.760 message about the lasting impact of human technology on our planet. 0:05:10.240 --> 0:05:13.039 And on the other hand, too, how forgettable we may 0:05:13.040 --> 0:05:17.840 be from the standpoint of geological history. Yeah, so if 0:05:17.839 --> 0:05:19.919 you're on board for all of that, you've come to 0:05:19.960 --> 0:05:23.200 the right place. So real quick, I do want to 0:05:23.240 --> 0:05:27.960 just discuss the Doctor Who reference here, since since uh, 0:05:28.080 --> 0:05:31.280 the authors Schmidt and Frank took the name for the 0:05:31.360 --> 0:05:35.360 hypothesis from the Doctor Who species the Silurians, who first 0:05:35.400 --> 0:05:39.120 popped up in the nineteen seventies series Doctor Who. And 0:05:39.279 --> 0:05:42.479 these Silurians, I think, now you've got me saying silurians, 0:05:43.400 --> 0:05:47.200 I probably probably stuff this way. Well, it gets even 0:05:47.240 --> 0:05:50.520 worse because so they take the name of the hypothesis 0:05:50.560 --> 0:05:53.680 from this Doctor Who series where these creatures show up. 0:05:54.080 --> 0:05:56.200 But then they say explicitly in the paper, you know, 0:05:56.279 --> 0:05:58.880 the range we would really be looking at would actually 0:05:58.880 --> 0:06:03.400 be after the Lurian geologic period, the Silurian period is 0:06:03.440 --> 0:06:07.240 something that's like a roughly twenty million year period that's 0:06:07.279 --> 0:06:09.440 more than four hundred million years ago. I don't remember. 0:06:09.440 --> 0:06:12.080 It's like four hundred and forty something to four hundred 0:06:12.080 --> 0:06:15.200 and twenty something, I think roughly. But if you were 0:06:15.240 --> 0:06:19.520 seriously looking for evidence of lost civilizations in Earth's ancient past, 0:06:20.000 --> 0:06:22.840 you'd probably be looking for things like after about four 0:06:22.920 --> 0:06:25.560 hundred million years ago, coming you know, forward in time 0:06:25.600 --> 0:06:29.240 from the Devonian period, when you could have the reasonable 0:06:29.240 --> 0:06:32.599 biological basis for land dwelling animals that might have evolved 0:06:32.640 --> 0:06:38.520 complex technological intelligence. Yes, but any rate. In Doctor Who, 0:06:39.279 --> 0:06:44.520 especially in that original nineteen seventy uh appearance, the Silurians 0:06:44.560 --> 0:06:47.640 are these kind of lizard men um. They factor into 0:06:47.680 --> 0:06:50.599 this plot with the third Doctor played by John part 0:06:50.680 --> 0:06:53.840 Way Who nineteen nine, nine ninety six, and then they 0:06:53.880 --> 0:06:57.360 subsequently pop up again with the fifth Doctor played by 0:06:57.360 --> 0:07:00.400 Peter Davison and the eleventh Doctor played by Matt Smith, 0:07:00.839 --> 0:07:03.520 and then more recently the third teenth Doctor played by 0:07:03.600 --> 0:07:06.240 Jody Whittaker. So this is just the TV show. I 0:07:06.240 --> 0:07:08.520 can't speak to the various books and audio dramas that 0:07:08.560 --> 0:07:12.040 have come out, and their look has changed throughout the film. Um, 0:07:12.120 --> 0:07:15.120 you know, they are, in essence, this cold blooded, prehistoric 0:07:15.200 --> 0:07:20.280 reptile like species with significant technological advancement that they they 0:07:20.320 --> 0:07:22.920 I think they end up entering various states of suspended 0:07:22.960 --> 0:07:26.280 animation to avoid uh you know, major changes on Earth, 0:07:26.360 --> 0:07:29.560 changes to the climate, etcetera. Um, and then they re 0:07:29.680 --> 0:07:34.840 emerge and encounter the Doctor. Um. So yeah, they're They're 0:07:34.880 --> 0:07:39.480 one of the many interesting alien and otherworldly species that 0:07:39.600 --> 0:07:42.960 pop up. Uh. Though, I guess with the Silurians, one 0:07:42.960 --> 0:07:46.000 of the key things is that they're they're not pure aliens. 0:07:46.040 --> 0:07:49.760 They're they're sort of the originals. There are their original terrans, 0:07:49.800 --> 0:07:54.360 original earthlings, uh, that are then encountered by these evolved 0:07:54.400 --> 0:07:57.200 apes that come much later. I mean to to them, 0:07:57.280 --> 0:08:02.320 we are the aliens. Yeah right, we're these weird future creatures. Uh. 0:08:02.480 --> 0:08:05.480 The image would tend And I gotta be honest, I'm 0:08:05.480 --> 0:08:08.680 not a hoovoid, so I don't know the lore. But 0:08:09.560 --> 0:08:12.160 the picture you're showing me of the Silurians, they look 0:08:12.240 --> 0:08:16.560 like they look like if the world was all creature 0:08:16.640 --> 0:08:20.240 from the Black Lagoon and there was a leather face 0:08:20.600 --> 0:08:24.960 of the creature from the Black Lagoon civilization. Yeah, I 0:08:24.960 --> 0:08:27.480 mean they're definitely Doctor Who creatures of this era, which 0:08:27.600 --> 0:08:30.040 which I tend to love these costumes. I know they 0:08:30.080 --> 0:08:34.360 were working with with with with budget limitations here, but yeah, 0:08:34.360 --> 0:08:37.400 the the aliens and robots of this era really really 0:08:37.440 --> 0:08:40.360 called me. Now you said you look kind of fish like. 0:08:40.559 --> 0:08:42.920 Bear in mind, and I'm sure some Doctor Who listeners 0:08:43.320 --> 0:08:45.720 Doctor Who viewers will will will chime in here, But 0:08:45.760 --> 0:08:49.040 I believe they are related to another species that pops 0:08:49.080 --> 0:08:50.760 up on the show that live in the water. I 0:08:50.760 --> 0:08:53.960 think they're like the sea devils or something. Um, but 0:08:54.200 --> 0:08:57.000 these guys are not aquatic in nature. I think I 0:08:57.040 --> 0:08:59.120 got that right. The seed of Oh wait, this is 0:08:59.160 --> 0:09:02.800 that like a a bunch of intelligent euryptorids or something 0:09:03.960 --> 0:09:06.880 something like that. Yeah, alright, So this is two thousand 0:09:06.960 --> 0:09:10.920 eighteen paper the Silurian hypothesis, Would it be possible to 0:09:10.960 --> 0:09:15.000 detect an industrial civilization in the Geological Record? This was 0:09:15.040 --> 0:09:20.080 published in the journal International Journal of Astrobiology. UH. It 0:09:20.160 --> 0:09:23.320 draws its name from that Doctor Who episode, and the 0:09:23.360 --> 0:09:25.319 authors here that they point out that they may be 0:09:25.440 --> 0:09:29.599 the first to seriously consider whether a technologically advanced civilization 0:09:29.679 --> 0:09:32.560 could have evolved prior to Homo sapiens on Earth, though 0:09:32.600 --> 0:09:35.320 the authors due stress that this is a to the 0:09:35.360 --> 0:09:38.320 best of their knowledge situation, so you know, it's entirely 0:09:38.320 --> 0:09:42.120 possible somebody was batting around the idea previously, but this 0:09:42.200 --> 0:09:44.120 may be the first, and certainly this was. This one 0:09:44.160 --> 0:09:46.320 really made a splash when it came out. Okay, So 0:09:46.440 --> 0:09:50.200 the two authors here would be Adam Frank and Givin A. 0:09:50.400 --> 0:09:54.280 Schmidt right and Frank is a is a physicist and astronomer, 0:09:54.320 --> 0:09:58.240 and Schmidt is a climate scientist right right. Schmidt is 0:09:58.280 --> 0:10:01.720 a climatologist, climate model and director of the NASA Gotted 0:10:01.800 --> 0:10:04.559 Institute for Space Studies in New York and co founder 0:10:04.559 --> 0:10:08.040 of the award winning climate science blog Real Climate. Frank 0:10:08.200 --> 0:10:11.160 is a physicist, astronomer, and writer whose work has appeared 0:10:11.200 --> 0:10:13.400 in such publications as The New York Times and NPR, 0:10:13.679 --> 0:10:15.520 and I believe we've actually referenced his work on the 0:10:15.559 --> 0:10:19.040 podcast before. Uh. He also has a book. He has 0:10:19.040 --> 0:10:21.960 a few books, including The Constant Fire, The End of 0:10:21.960 --> 0:10:24.880 the Beginning, and Light of the Stars. Those are all 0:10:25.000 --> 0:10:28.040 nonfiction science books, of course, So to be clear, we're 0:10:28.040 --> 0:10:32.160 talking about two very legitimate scientists and science communicators, not 0:10:32.679 --> 0:10:35.400 you know, not a couple of of quacks who were 0:10:35.440 --> 0:10:38.320 staring into the hollow Earth or anything. So the authors 0:10:38.360 --> 0:10:41.680 here begin with a very reasonable consideration of the search 0:10:41.720 --> 0:10:44.800 for intelligent life elsewhere in the universe. Uh. And then 0:10:44.840 --> 0:10:46.720 this is something we've we've touched on the show plenty 0:10:46.720 --> 0:10:49.480 of times before. Ours is the only model of life, 0:10:49.880 --> 0:10:53.160 but we generally consider technological advancement to be a hallmark 0:10:53.280 --> 0:10:55.600 of intelligent life. And more to the point, something we 0:10:55.640 --> 0:10:59.079 can search for signs of, uh concerning other worlds and 0:10:59.120 --> 0:11:02.280 other star systems. Uh. You know, and anytime you can, 0:11:02.360 --> 0:11:04.920 you can figure out how to look for signs of 0:11:04.920 --> 0:11:09.400 of advanced and expansive energy harvesting or consumption. Uh. That 0:11:09.520 --> 0:11:11.280 might be a way for us to tell if there's 0:11:11.320 --> 0:11:15.400 something else out there that is significantly advanced. Right, and 0:11:15.480 --> 0:11:20.880 it also might be a simple prerequisite for contact, because uh, 0:11:21.160 --> 0:11:24.040 they're talking about so that they started off by looking 0:11:24.080 --> 0:11:26.679 at this as an astrobiology question. You know, you're you're 0:11:26.720 --> 0:11:29.640 looking for signs of life elsewhere in the universe. And 0:11:29.679 --> 0:11:31.880 of course, the the search for intelligent life in the 0:11:31.960 --> 0:11:35.280 universe in practical terms, what's accessible to us really boils 0:11:35.320 --> 0:11:39.320 down to the search for life capable of Harvard harnessing 0:11:39.440 --> 0:11:42.360 radio technology within our galaxy. You know, you could probably 0:11:42.400 --> 0:11:48.000 find maybe chemical biosignatures in in the atmospheres of exoplanets 0:11:48.080 --> 0:11:50.360 that would give you an indication that there's some kind 0:11:50.360 --> 0:11:53.480 of life there, maybe bacterial in nature or whatever. But 0:11:53.520 --> 0:11:56.280 if you're looking for intelligent life, you're you're probably talking 0:11:56.280 --> 0:11:59.640 about radio of some kind, right, And so the kinds 0:11:59.679 --> 0:12:04.120 of civilizations that develop radio communication technology would fall under 0:12:04.160 --> 0:12:08.040 the classification of industrial civilizations. And these are what author 0:12:08.320 --> 0:12:11.520 the authors define as civilizations that have the ability to 0:12:11.640 --> 0:12:15.560 harness energy on a global scale. And they bring up 0:12:15.559 --> 0:12:18.760 how this actually feeds into one of the the recurring 0:12:19.440 --> 0:12:25.040 characters in in the astrobiology literature, the Drake equation. That's right, Yeah, 0:12:24.520 --> 0:12:27.800 they bust out the Drake equation, and of course consider 0:12:27.840 --> 0:12:30.360 how how some of the takeaways relate to Earth, especially 0:12:30.400 --> 0:12:33.000 the notion that over the course of a planet's existence, 0:12:33.440 --> 0:12:37.480 multiple industrial civilizations can theoretically arise over the span of 0:12:37.559 --> 0:12:40.840 time that life exists there. And then we have to 0:12:40.880 --> 0:12:43.400 factor in questions over you know, how many times life 0:12:43.440 --> 0:12:46.240 itself may have evolved or started out on Earth before 0:12:46.280 --> 0:12:50.000 our last universal common ancestors got going. The possibility of 0:12:50.000 --> 0:12:53.239 a shadow biosphere and the idea that species like dolphins 0:12:53.600 --> 0:12:57.600 may suggest independent evolutions of intelligence on Earth. Um, you know, 0:12:57.600 --> 0:13:00.480 so we're left with this idea that, yeah, the radically 0:13:00.720 --> 0:13:04.520 and given the footprint of life on Earth, you could 0:13:04.640 --> 0:13:08.760 have had multiple intelligences uh evolved and arise during that 0:13:08.840 --> 0:13:12.679 time period. Because that's certainly what the Drake equation seems 0:13:12.720 --> 0:13:15.600 to allow for concerning other worlds. Well, yeah, and I 0:13:15.840 --> 0:13:18.640 you know so I kind of love the Drake equation. 0:13:18.840 --> 0:13:20.880 You know, it's a famous tool that I really enjoy 0:13:21.000 --> 0:13:25.760 thinking about because because it does the job of taking 0:13:25.800 --> 0:13:29.240 a question that seems like we could not possibly answer. 0:13:29.360 --> 0:13:33.360 The question is how many active technological civilizations are there 0:13:33.360 --> 0:13:36.080 in the Milky Way galaxy? And you know, if you're 0:13:36.200 --> 0:13:38.720 being honest with yourself, the correct answer to that is 0:13:38.880 --> 0:13:41.240 how the hell should I know? Like, there's no way 0:13:41.280 --> 0:13:44.720 to answer that question at all. But what the Drake 0:13:44.760 --> 0:13:49.720 equation does is break that unanswerable question down into a 0:13:49.880 --> 0:13:53.800 number of other questions that you then multiplied together to 0:13:53.960 --> 0:13:58.040 get an estimated number. And many of those smaller questions 0:13:58.120 --> 0:14:01.280 themselves could perhaps be answered, and in fact, some of 0:14:01.320 --> 0:14:04.640 them have been answered since the Drake equation was first formulated. 0:14:05.240 --> 0:14:09.280 Uh so, So it decomposes an unsolvable problem of are 0:14:09.320 --> 0:14:11.880 there aliens out there? And if so, how many, into 0:14:11.920 --> 0:14:14.680 a series of smaller problems, at least some of which 0:14:14.720 --> 0:14:16.960 are solvable, maybe all of which are. You know, you 0:14:16.960 --> 0:14:19.200 could come up with some kind of reasonable gas about. 0:14:20.040 --> 0:14:22.400 And so the classic formulation of the Drake equation is 0:14:22.440 --> 0:14:25.280 to get your number of civilizations in the milky way, 0:14:25.840 --> 0:14:28.360 you would multiply a bunch of different terms together. So 0:14:28.480 --> 0:14:31.680 one is the rate of average the average rate of 0:14:31.720 --> 0:14:34.440 star formation. You know, how much do you get stars 0:14:34.960 --> 0:14:39.400 times the fraction of stars that have planets times the 0:14:39.440 --> 0:14:43.520 average number of planets per star, times the fraction of 0:14:43.560 --> 0:14:47.720 planets that develop life times the portion of those life 0:14:47.760 --> 0:14:51.840 systems that gain intelligence, times the portion of those intelligent 0:14:51.920 --> 0:14:56.040 life systems that develop technological means to communicate times. And 0:14:56.080 --> 0:14:59.400 then here's a really interesting term, quote the length of 0:14:59.480 --> 0:15:04.200 time l over which such civilizations released detectable signals. And 0:15:04.240 --> 0:15:06.840 it's this very last term that I think very often 0:15:06.880 --> 0:15:09.440 gets overlooked by people who are thinking about, you know, 0:15:09.480 --> 0:15:12.080 are there aliens out there? And how could we know? 0:15:12.800 --> 0:15:14.880 I think we often tend to assume that, well, once 0:15:14.960 --> 0:15:18.600 there are aliens with technological means to communicate. That's just 0:15:18.640 --> 0:15:22.800 like a you know, progress only extends from their civilizations 0:15:22.880 --> 0:15:25.840 just continue to get bigger and their capabilities expand and 0:15:25.840 --> 0:15:28.320 they spread out from there. But I don't know that 0:15:28.720 --> 0:15:32.440 there could be severe limitations on the length of a 0:15:32.680 --> 0:15:37.720 radio receptive or radio broadcasting civilization. Maybe they only exist 0:15:37.760 --> 0:15:39.840 for a few hundred years. Because one thing we know 0:15:39.920 --> 0:15:45.480 is that our technological civilization is just a tiny blip 0:15:45.720 --> 0:15:48.280 on the history of planet Earth, even a tiny blip 0:15:48.360 --> 0:15:50.960 on the history of life on planet Earth. Earth is 0:15:51.280 --> 0:15:54.160 four point five billion years old. There's been life on 0:15:54.200 --> 0:15:57.160 Earth for most of that time. Uh. The authors here 0:15:57.240 --> 0:15:59.880 estimate that there has been complex life on Earth to 0:16:00.120 --> 0:16:04.320 land surface for only about four hundred million years. So 0:16:04.440 --> 0:16:06.960 that's only a fraction of the entire history of Earth. 0:16:07.200 --> 0:16:09.160 But that but four hundred million years is still a 0:16:09.160 --> 0:16:12.560 gargantuan amount of time compared to the length of human civilization. 0:16:13.040 --> 0:16:16.400 They say, industrial civilization, you know, by their metric, has 0:16:16.440 --> 0:16:19.360 probably existed for only about three hundred years. This is 0:16:19.560 --> 0:16:23.880 since roughly the beginning of mass production methods for for things, 0:16:24.320 --> 0:16:26.680 and so if humans were wiped out by a global 0:16:26.760 --> 0:16:29.680 mass extinction, of some kind in the near future. Our 0:16:29.720 --> 0:16:34.360 industrial civilization would just be this tiny little splinter, this 0:16:34.640 --> 0:16:38.240 blip of three hundred years on a history of a 0:16:38.320 --> 0:16:42.280 currently four point five billion year old planet. Yeah, and 0:16:42.360 --> 0:16:45.200 so from there we get into the question, Okay, if 0:16:45.240 --> 0:16:47.600 if you have an industrial civilization like this, it is 0:16:47.640 --> 0:16:50.880 just a blip, would we be able to see it? 0:16:51.280 --> 0:16:53.520 And if we could see it, what would we look for? 0:16:53.600 --> 0:16:55.000 And this is you know, this is pretty much the 0:16:55.320 --> 0:16:58.720 meat of the paper here analyzing this sort of question, 0:16:58.760 --> 0:17:00.800 which which is great because it it again it gets 0:17:00.800 --> 0:17:04.440 into sort of uh, you know, sci fi friendly concepts. 0:17:04.800 --> 0:17:08.359 It's a useful in considering the evolution of life and 0:17:08.400 --> 0:17:11.879 the existence of intelligent life on other worlds. And it 0:17:11.960 --> 0:17:15.440 also shines a light on what we're doing now and 0:17:15.520 --> 0:17:19.000 where we are. And and I think also, uh, you know, 0:17:19.080 --> 0:17:24.280 illustrates nicely illustrates this idea that um that that the 0:17:24.320 --> 0:17:27.679 technology is not just this um that this this this 0:17:27.840 --> 0:17:30.280 ramp to Star Trek, you know, or this ramp to 0:17:30.440 --> 0:17:32.960 the culture or any of our more optimistic sci fi 0:17:33.040 --> 0:17:36.639 dreams like there are there are severe challenges. Uh. And 0:17:36.680 --> 0:17:40.000 of course there's there's always the risk of extinction. That's 0:17:40.000 --> 0:17:43.600 exactly right. And one thing that's funny is we don't 0:17:43.800 --> 0:17:49.919 know whether the rise of technological civilization should generally be 0:17:50.000 --> 0:17:53.520 understood as, on average, a linear process where it just 0:17:53.560 --> 0:17:56.199 sort of goes in one direction and keeps going in 0:17:56.240 --> 0:17:59.240 that direction, or whether it should be understood as on 0:17:59.320 --> 0:18:02.440 average a sick clickal process where you get a rise 0:18:02.440 --> 0:18:05.840 in technological civilization, then then it disappears for some reason. 0:18:05.880 --> 0:18:08.760 You can imagine what some of those reasons might be. Um, 0:18:09.040 --> 0:18:11.679 and uh, and then maybe rises again out of the 0:18:11.720 --> 0:18:14.399 out of the same biosphere. I mean, either one I 0:18:14.440 --> 0:18:18.320 think is a perfectly plausible model to entertain is like 0:18:18.400 --> 0:18:22.199 what usually happens in the universe. Uh. And we just 0:18:22.240 --> 0:18:24.919 don't have the h we don't have the evidence to 0:18:24.960 --> 0:18:27.399 really have an opinion on that. Yeah, I mean a 0:18:27.440 --> 0:18:30.600 lot of it just comes back to the fact that, again, 0:18:30.680 --> 0:18:34.000 we are the only model of intelligent life, and certainly 0:18:34.040 --> 0:18:38.080 technologically advanced intelligent life that we have to look at, 0:18:38.480 --> 0:18:40.679 So we have nothing to compare us to. Yeah, and 0:18:40.720 --> 0:18:42.520 we don't know what's going to happen to us in 0:18:42.560 --> 0:18:47.240 the long run. Right. So uh, Well, let's get into 0:18:47.280 --> 0:18:48.760 the I guess the sort of the first part of 0:18:48.760 --> 0:18:50.520 the paper, and I do want to drive home that 0:18:50.560 --> 0:18:53.159 if you want to just go right to the paper 0:18:53.280 --> 0:18:56.119 yourself and dive in. Um, you just do a search 0:18:56.160 --> 0:18:59.000 for the title and you can find it hosted on NASA. 0:18:59.080 --> 0:19:01.840 They have as has a as a PDF of this 0:19:02.000 --> 0:19:05.439 that's very easily accessible. Uh. You can also read it 0:19:05.480 --> 0:19:08.040 in full on the Cambridge University Press website, which I 0:19:08.040 --> 0:19:11.240 think is the press behind the journal, the International Journal 0:19:11.359 --> 0:19:13.880 Journal of Astrobiology. And yeah, so it's all on their 0:19:13.960 --> 0:19:16.120 end with the references hyper linked and all that, which 0:19:16.160 --> 0:19:18.760 is nice. Yes, yeah, absolutely so if he hit a paywall, 0:19:18.880 --> 0:19:21.560 don't don't give up. It's out there. UM. And I 0:19:21.560 --> 0:19:23.560 believe Adam Frank also wrote a piece for What the 0:19:23.560 --> 0:19:26.880 Atlantic where he nicely summarizes some of the ideas here. 0:19:27.040 --> 0:19:29.240 Oh yeah, and he also tells a funny story about 0:19:29.240 --> 0:19:31.639 how they arrived at writing the paper, because I think 0:19:31.720 --> 0:19:35.080 he says, uh, he showed up in Gevin Schmidt's office 0:19:35.160 --> 0:19:39.240 to to talk about UM, to talk more about astrobiology 0:19:39.320 --> 0:19:42.480 like Drake equation type questions, and he's like, okay, so 0:19:42.600 --> 0:19:46.639 we we we know we've got one industrial civilization on Earth. 0:19:47.040 --> 0:19:49.359 And then Schmidt responded by saying, how do we know 0:19:49.400 --> 0:19:53.359 we're the only one just hitting that early like wall. 0:19:53.400 --> 0:19:56.400 They're like wow, And then that turned into the paper. Yeah, 0:19:56.440 --> 0:20:04.760 and it's it's it's quite a paper. So let's see, 0:20:04.880 --> 0:20:06.480 let's get into the first part of it, which I 0:20:06.560 --> 0:20:08.320 think you can loosely think of it's just sort of 0:20:08.320 --> 0:20:10.960 a look at the limits of our vision. So they 0:20:11.000 --> 0:20:15.200 point out that for the last two point five million years, uh, 0:20:15.240 --> 0:20:19.800 there's widespread physical evidence of things like climate change, soil 0:20:19.880 --> 0:20:23.240 horizons this is where one layer of soil differs from 0:20:23.280 --> 0:20:27.880 belower above, speaking to changes recorded in the soil, as 0:20:27.880 --> 0:20:32.800 well as archaeological evidence of non Homo sapiens cultures such 0:20:32.800 --> 0:20:36.400 as the Neanderthals. And this two point five million year 0:20:36.480 --> 0:20:39.760 period is known as the Quaternary. Now, going back before 0:20:39.800 --> 0:20:43.400 the Quaternary again more than two point five million years ago, 0:20:43.640 --> 0:20:46.159 the land evidence is harder to come by. You have 0:20:46.240 --> 0:20:50.639 to depend on drilling, mining, and occasional exposed sections of 0:20:50.720 --> 0:20:54.320 the earth. Even in the ocean, sentiment evidence apparently only 0:20:54.359 --> 0:20:57.840 goes back to around one seventy million years ago. Yeah, 0:20:57.920 --> 0:21:00.119 and I think for me this was actually one of 0:21:00.160 --> 0:21:04.040 the most interesting parts of the paper because I would say, 0:21:04.080 --> 0:21:07.880 if you just go by standard intuition. A person might think, uh, 0:21:07.960 --> 0:21:12.240 you know, if there had been a civilization on Earth, 0:21:12.520 --> 0:21:15.600 you know, a two million years ago or something like that. Uh, 0:21:15.760 --> 0:21:18.520 would wouldn't that just be completely obvious, Like we'd see 0:21:18.520 --> 0:21:21.000 evidence of it all around us? Would there be ruins 0:21:21.040 --> 0:21:23.399 and all that, you know, their their stone hinges, their 0:21:23.440 --> 0:21:28.400 skyscrapers and everything like that. Actually it's not. It might 0:21:28.440 --> 0:21:30.879 not be as obvious as you might think. In fact, 0:21:31.119 --> 0:21:34.359 the evidence of it could be rather scarce. And this 0:21:34.480 --> 0:21:38.399 runs counter to our sci fi imaginings, right, because you 0:21:38.480 --> 0:21:42.480 encounter elder civilizations and in other works like there's usually 0:21:42.480 --> 0:21:44.720 some sort of a ruin or a vault or some 0:21:44.800 --> 0:21:48.560 sort of mysterious monolith or something like the idea that 0:21:48.640 --> 0:21:52.080 the elders would just be gone entirely, like just erased, 0:21:52.359 --> 0:21:55.119 not by some sort of a conspiracy or by some 0:21:55.240 --> 0:21:58.200 sort of a you know, alien shenanigans, but just because 0:21:58.240 --> 0:22:01.200 things don't last that long. That's uh, it's an alien 0:22:01.240 --> 0:22:03.879 concept from too many of our again, too many of 0:22:03.880 --> 0:22:06.480 our creative visions of of what the future. In the past, 0:22:06.600 --> 0:22:09.159 maybe exactly so, we think, well, you know, there are 0:22:09.240 --> 0:22:12.160 ruins of civilizations from thousands of years ago, but that's 0:22:12.200 --> 0:22:15.800 thousands of years ago. That's nothing in geological time. The 0:22:15.880 --> 0:22:18.040 surface of the I mean, look a look at what 0:22:18.119 --> 0:22:21.800 a map of the land formations on Earth just you know, 0:22:22.160 --> 0:22:25.000 sixty million years ago looked like It's like, you know, 0:22:25.119 --> 0:22:28.600 the the surface of the Earth is not fixed and constant. 0:22:28.640 --> 0:22:31.800 This is a geologically active planet. So would there be 0:22:31.920 --> 0:22:35.159 ruins all around us? Would evidence of a civilization from 0:22:35.280 --> 0:22:37.880 hundreds of millions of years ago just be totally obvious? 0:22:38.560 --> 0:22:41.479 I think I probably by the answer that the authors 0:22:41.520 --> 0:22:43.640 give here, which is that no, it would probably not 0:22:43.720 --> 0:22:46.720 be totally obvious. In fact, it might be incredibly difficult 0:22:46.760 --> 0:22:50.320 to find evidence of at all. Uh. And so one 0:22:50.359 --> 0:22:52.760 of the the interesting points the authors make here is 0:22:52.800 --> 0:22:55.880 that the the exposed land surface of Earth, of course, 0:22:55.960 --> 0:22:59.280 is geologically very young on average. They cite evidence from 0:22:59.280 --> 0:23:01.000 a study by ma at mon at All in two 0:23:01.040 --> 0:23:04.360 thousand nine that the oldest large patch of land surface 0:23:04.440 --> 0:23:08.000 on Earth is probably in the Negev Desert, and that's 0:23:08.000 --> 0:23:10.600 only about one point eight million years old. One point 0:23:10.680 --> 0:23:12.639 eight million years, I mean, compared to the history of 0:23:12.680 --> 0:23:16.480 civilization is a long time. But that's again, it's like 0:23:16.560 --> 0:23:19.560 nothing in geological time. It's a tiny fraction of of 0:23:19.640 --> 0:23:23.040 earth history. So if we wanted to find remnants of 0:23:23.040 --> 0:23:26.920 a civilization from say, hundreds of millions of years ago, 0:23:27.359 --> 0:23:29.240 you probably would not find that on the surface of 0:23:29.240 --> 0:23:31.320 the Earth. You'd have to look for it in in 0:23:31.480 --> 0:23:36.560 exposed geological strata from from previous eras. And even then 0:23:36.680 --> 0:23:38.520 you can't just count on the fact that you would 0:23:38.520 --> 0:23:43.000 be finding fossils of that civilization all over the place. Yeah, exactly. 0:23:43.440 --> 0:23:45.840 That They that they hit on something we we've discussed 0:23:45.840 --> 0:23:47.400 on the show before, which is, of course that the 0:23:47.440 --> 0:23:52.480 fossil record is inherently incomplete, because fossilization only occurs when 0:23:52.520 --> 0:23:56.800 conditions are just right. Um. They point out that that 0:23:56.880 --> 0:24:00.200 of all the dinosaurs that ever lived, and there were 0:24:00.240 --> 0:24:03.280 a ton of you know, uh, you know, they're the 0:24:03.680 --> 0:24:07.400 era of the dinosaurs taken as as one gigantic, gigantic 0:24:07.440 --> 0:24:11.879 monolith just dwarfs anything that that that that humanity has 0:24:11.920 --> 0:24:14.520 ever occupied. Uh. You know, it is a it is 0:24:14.520 --> 0:24:17.920 a cathedral, and and we're we're not even like a 0:24:18.000 --> 0:24:23.400 child's dollhouse, uh sort of situation here. Um. So uh, 0:24:23.440 --> 0:24:25.760 you know, out of out of all of those dinosaurs 0:24:25.760 --> 0:24:27.800 that ever lived, there are only a few thousand near 0:24:27.840 --> 0:24:30.960 complete specimens. And so the authors here contend that given 0:24:31.000 --> 0:24:34.199 the rarity of fossilization, a species is short lived, as 0:24:34.240 --> 0:24:37.520 Homo sapiens might not make it into the fossil record 0:24:37.640 --> 0:24:40.920 at all. And of course, for fossilization to mean anything 0:24:41.160 --> 0:24:44.440 to us, or to you know, anybody who's doing a 0:24:44.640 --> 0:24:46.720 uh doing you know, some sort of an investigation of 0:24:46.760 --> 0:24:50.040 a planet or our planet, those fossilizations would have to 0:24:50.080 --> 0:24:53.400 survive and then they would have to be found. Yeah, exactly. 0:24:53.480 --> 0:24:56.520 And and so again this might be pushing against your intuition. 0:24:56.560 --> 0:24:58.480 You would say, like, wait a minute, there's there's there's 0:24:58.520 --> 0:25:01.480 there's signs of human life all over the surface of Earth. 0:25:01.520 --> 0:25:03.640 And and we have, you know, at least a few 0:25:03.680 --> 0:25:07.800 thousand uh complete dinosaur fossils, enough to have museums of 0:25:07.880 --> 0:25:11.560 natural history with dinosaur fossils in places all over the world. Uh, 0:25:11.720 --> 0:25:15.480 surely you'd expect more. But dinosaurs existed for almost two 0:25:15.600 --> 0:25:20.800 hundred million years. Human civilization again is like it's a 0:25:20.840 --> 0:25:25.000 few thousand years at this point. Yeah. So the problem 0:25:25.040 --> 0:25:28.359 here is like we have trouble comparing the odds because 0:25:28.880 --> 0:25:32.800 you're not realizing how many millions of times more the 0:25:32.960 --> 0:25:38.320 dinosaur bodies got to roll the dice than ours would. Yeah. Absolutely. 0:25:38.840 --> 0:25:41.320 Another thing they touch on is that is the example 0:25:41.320 --> 0:25:44.600 of technology. Uh, and they point out how rarely complex 0:25:44.680 --> 0:25:48.119 early examples of human technology are ever found. So if 0:25:48.160 --> 0:25:50.920 you're thinking, well, surely we would find one of these 0:25:50.960 --> 0:25:53.880 factories or something that was made by one of these 0:25:53.920 --> 0:25:59.040 factories that a previous civilization might have had, well not necessarily. Yeah, 0:25:59.080 --> 0:26:02.199 sure surely my rice cooker would be found hundreds of 0:26:02.200 --> 0:26:04.919 millions of years in the future. But yeah, that they 0:26:05.440 --> 0:26:09.040 mentioned several reasons why that's maybe not as clear as 0:26:09.040 --> 0:26:13.160 you might assume. So they say urbanization that currently represents 0:26:13.200 --> 0:26:16.520 less than one percent of the Earth's surface, So that's 0:26:16.520 --> 0:26:19.679 a limitation on the deposition side of of creating a 0:26:19.680 --> 0:26:23.119 fossil record of our current civilization. Only small parts of 0:26:23.160 --> 0:26:27.280 Earth's surface are actually inhabited by humans. That that sounds counterintuitive, 0:26:27.320 --> 0:26:31.080 but it's true. And then they point out that quote 0:26:31.119 --> 0:26:35.400 exposed sections and drilling sites for pre quaternary surfaces are 0:26:35.520 --> 0:26:39.520 orders of magnitude less as fractions of the original surface. 0:26:39.840 --> 0:26:43.639 So human civilization currently only feels a small portion of 0:26:43.680 --> 0:26:49.040 Earth's surface right now, and we only access tiny fractions 0:26:49.080 --> 0:26:52.440 of Earth's previous surface through through various kinds of drilling 0:26:52.520 --> 0:26:56.359 and you know, access through exposure to rock strata. So 0:26:56.400 --> 0:27:00.919 there's just like extreme selection filters on both sides, on 0:27:00.960 --> 0:27:04.280 the deposition and on the excavation side. Yeah, it would 0:27:04.280 --> 0:27:07.600 be kind of like even if you you knew somehow, 0:27:07.640 --> 0:27:10.800 with some certainty that there was that that there was 0:27:10.800 --> 0:27:15.520 a technological civilization during this time in the ancient ancient past. Uh, yeah, 0:27:15.600 --> 0:27:17.560 you would. You would have to you have to really 0:27:17.600 --> 0:27:19.879 know exactly where to drill down to hit them. You 0:27:19.920 --> 0:27:22.760 couldn't just expect to randomly do it unless you did 0:27:23.160 --> 0:27:27.320 a lot of drilling and digging and and excavation. Um. 0:27:28.040 --> 0:27:30.680 But but but so what we've been talking about here 0:27:30.840 --> 0:27:34.560 is challenging the the intuition that you would just be 0:27:34.680 --> 0:27:39.959 finding physical fossil remnants and artifacts of this civilization from 0:27:40.040 --> 0:27:42.680 hundreds of millions of years ago all over the place. 0:27:42.720 --> 0:27:44.520 And I think they do a very good job of 0:27:44.600 --> 0:27:47.720 knocking that down. But of course it is not hopeless 0:27:47.720 --> 0:27:49.800 because they say, while our chance of finding the physical 0:27:49.840 --> 0:27:53.920 remains of a hypothetical Silarian civilization might be very low, 0:27:54.359 --> 0:27:56.679 there would be other traces of the existence of that 0:27:56.720 --> 0:28:00.520 civilization that would be preserved in the geologic record, and 0:28:00.960 --> 0:28:03.080 you you would have a very good chance of finding 0:28:03.119 --> 0:28:06.480 those traces. Yeah, and that's that's what most of the 0:28:06.560 --> 0:28:08.040 rest of the paper deals with. I do want to 0:28:08.040 --> 0:28:10.080 point out one of the things that they bring up 0:28:10.080 --> 0:28:12.640 in passing that I thought was interesting. They point out 0:28:12.680 --> 0:28:15.520 that that you could certainly make an argument for or 0:28:15.560 --> 0:28:18.560 against the evolution of intelligent life in a world based 0:28:18.600 --> 0:28:21.480 on the probable evolution of species that are in the 0:28:21.520 --> 0:28:26.800 fossil record, but that they would be focusing on physiochemical 0:28:27.280 --> 0:28:30.840 tracers for previous industrial civilization. So I hadn't really thought 0:28:30.840 --> 0:28:33.800 about this, but like the idea of like looking at say, 0:28:34.080 --> 0:28:38.720 dinosaur fossils and saying, well, we don't have evidence that 0:28:38.800 --> 0:28:43.000 they evolved in into an intelligent technological species, but if 0:28:43.040 --> 0:28:45.400 we but we can make an argument based on this 0:28:45.480 --> 0:28:47.760 fossil and this fosil fossil that they were headed in 0:28:47.800 --> 0:28:50.240 that direction. I feel like even that's the kind of 0:28:50.240 --> 0:28:53.000 thing that probably wouldn't be quite as clear as your 0:28:53.040 --> 0:28:55.680 intuition might lead you to assign them, because I mean, 0:28:55.760 --> 0:29:01.960 like intelligence in mammals arose very rapidly in geologic time. Yeah, 0:29:02.040 --> 0:29:05.320 So again it reached this situation where the fossil record 0:29:05.720 --> 0:29:09.200 could just be missing that snapshot entirely. So this all 0:29:09.280 --> 0:29:11.320 leads you the next to the next major question. Given 0:29:11.360 --> 0:29:14.320 the limits of what we can dettacked in the geochemical record, 0:29:14.640 --> 0:29:17.360 what exactly could we look for on a planet to 0:29:17.400 --> 0:29:21.480 see if an industrial society ever existed there? And yeah, 0:29:21.520 --> 0:29:23.600 that's what the bulk of the paper focuses on. So 0:29:23.640 --> 0:29:27.280 in the case of Earth, if an organized, intelligent society 0:29:27.320 --> 0:29:32.520 evolved during the pre Quaternary time but they didn't reach 0:29:32.600 --> 0:29:35.360 the level of an industrial society, there simply would be 0:29:35.400 --> 0:29:38.080 no record of them as far as this paper is concerned. 0:29:38.640 --> 0:29:42.720 Right there, they're looking for the kinds of chemical, material 0:29:42.880 --> 0:29:45.520 and climate type changes that would leave a trace in 0:29:45.560 --> 0:29:48.520 the geologic record, and that would primarily be a function 0:29:48.880 --> 0:29:54.480 of of industry, basically of energy, production of of material 0:29:54.560 --> 0:29:58.640 working things like metals and plastics, and the uh and 0:29:58.760 --> 0:30:02.600 the methods of harn using energy for industrial use. I 0:30:02.680 --> 0:30:08.160 was reminded of our episodes on fire technology because if 0:30:08.240 --> 0:30:11.160 listeners may remember, we discussed, well, could something that evolved 0:30:11.200 --> 0:30:13.760 in the water or or on a water world, could 0:30:13.800 --> 0:30:16.800 they ever really get any kind of advanced technology going 0:30:17.160 --> 0:30:19.840 if they didn't have access to the surface, and that 0:30:19.880 --> 0:30:21.600 seems to be a factor here as well, as they're 0:30:21.600 --> 0:30:24.600 only looking at the period during which something could have 0:30:24.720 --> 0:30:28.160 evolved on land. Yeah, so you could maybe have advanced 0:30:28.200 --> 0:30:31.840 intelligence in the water. But it's maybe this is just 0:30:31.880 --> 0:30:33.680 a lack of imagination on our part. You know, you 0:30:33.720 --> 0:30:36.480 always need to be aware of the limitations of your vision. 0:30:36.600 --> 0:30:40.200 But it does seem hard to imagine advanced technology under 0:30:40.200 --> 0:30:43.000 the water, because like if you don't have fire, you 0:30:43.040 --> 0:30:45.880 can't do metal working, or metal working is very difficult. 0:30:45.960 --> 0:30:47.600 I don't I don't know. It just seems harder to 0:30:47.640 --> 0:30:50.880 imagine how technology like we understand it could come about 0:30:50.960 --> 0:30:54.240 in the water. But again, you know, limits of our vision. Yeah, 0:30:54.320 --> 0:30:56.240 so they say, quote, the focus is thus on the 0:30:56.240 --> 0:30:59.120 period between the emergence of complex life on land in 0:30:59.360 --> 0:31:02.960 the Devonian four million years ago in the Paleozoic era 0:31:03.360 --> 0:31:06.480 and the mid appli A scene. Uh, and that's around 0:31:06.560 --> 0:31:09.560 four million years ago, Yeah, because if it was much 0:31:09.600 --> 0:31:12.560 more recent, you'd you'd probably get into the area where 0:31:12.560 --> 0:31:15.040 you'd start to expect to actually see those kinds of 0:31:15.520 --> 0:31:18.600 remnants and artifacts that that we were talking about. Right, 0:31:19.280 --> 0:31:21.760 So they get into the discussion of what we might 0:31:21.880 --> 0:31:25.120 look for, and they haven't nicely divided up. The first 0:31:25.120 --> 0:31:29.000 one is, uh, well, they basically have two broad categories 0:31:29.000 --> 0:31:32.880 and then some some details on that category. The first 0:31:32.920 --> 0:31:36.360 big one though, would be looking at the geological footprint 0:31:36.520 --> 0:31:39.280 of the anthroposcene. So, as we've discussed in the show before, 0:31:39.320 --> 0:31:41.320 there's an argument to be made that the impact of 0:31:41.400 --> 0:31:44.719 human civilization on the environment and the geologic record constitutes 0:31:44.760 --> 0:31:49.280 its own geologic era, the Anthropocene. So not all the 0:31:49.360 --> 0:31:52.080 changes would be recognizable millions of years later, but some 0:31:52.160 --> 0:31:56.720 would be. Right. So, human activity at this point is 0:31:56.720 --> 0:32:00.240 is large scale enough that we are making change is 0:32:00.280 --> 0:32:04.480 to the earth that that are that are widespread or 0:32:04.600 --> 0:32:07.760 you could even say global, And I was gonna say permanent, 0:32:07.800 --> 0:32:10.480 not permanent, but extremely long lived. You know, going way 0:32:10.560 --> 0:32:13.840 into the future, you will be able to find signs 0:32:13.880 --> 0:32:16.440 in the rocks and the ice and the setiment, you know, 0:32:16.560 --> 0:32:19.000 the things on Earth that persists over long periods of 0:32:19.000 --> 0:32:22.000 time that will leave records of what we did to 0:32:22.080 --> 0:32:25.480 the earth in just the past three years or so. Right, 0:32:26.040 --> 0:32:29.560 And uh, And as we've probably mentioned before, the anthropasyn 0:32:29.680 --> 0:32:33.959 is not a an official geological era as much as 0:32:34.000 --> 0:32:36.160 any of these things can be, you know, official if 0:32:36.360 --> 0:32:38.440 it seems like when you're talking about geologic terms, it's 0:32:38.480 --> 0:32:42.040 even more ridiculous. We can consider such a small part 0:32:42.080 --> 0:32:45.560 of geologic history that we occupy, but there's a lot 0:32:45.600 --> 0:32:48.240 of compelling evidence for it, and you often see it discussed, 0:32:48.320 --> 0:32:52.040 especially when we're talking about the changes that that humans 0:32:52.040 --> 0:32:54.400 have made to the planet and are still making to 0:32:54.440 --> 0:32:56.920 the planet and how they may show up in the 0:32:56.960 --> 0:32:59.959 geologic record. And just to be super clear, the majority 0:33:00.000 --> 0:33:01.880 any of the changes we're talking about of this kind 0:33:02.200 --> 0:33:06.160 would not be changes like physical alterations of the Earth's surface. 0:33:06.400 --> 0:33:09.480 We're not talking about like records of people digging holes 0:33:09.560 --> 0:33:13.360 and building stuff. We're talking about records of like changes 0:33:13.480 --> 0:33:18.080 to the to the level of different carbon isotopes in 0:33:18.080 --> 0:33:21.840 in geological strata and things like that. Right now, they 0:33:21.880 --> 0:33:23.960 also hit upon something that that I thought was really 0:33:24.000 --> 0:33:27.480 interesting and in a way almost almost encouraging, uh, the 0:33:27.520 --> 0:33:31.040 sustainability paradox. So the idea here is that of course 0:33:31.040 --> 0:33:36.440 the longer human civilization lasts, especially technological civilization, the greater 0:33:36.520 --> 0:33:40.920 the geologic signal of its impact. Again, that that lasting 0:33:41.000 --> 0:33:44.080 those lasting signs in the environment, not the faces they 0:33:44.080 --> 0:33:49.280 carved into the mountains but impacts again on their their 0:33:49.320 --> 0:33:54.240 geochemical and nature. Um, so that signal increases. But the 0:33:54.360 --> 0:33:59.160 longer human civilization lasts, the more sustainable it must become 0:33:59.200 --> 0:34:01.880 in order to revive. And this is of course the 0:34:01.920 --> 0:34:05.520 reality we're living in right now. If a civilization survives 0:34:05.560 --> 0:34:10.480 this test and becomes more sustainable, then that signal grows weaker. Right. 0:34:10.520 --> 0:34:12.960 So it's almost like the strength of the signal left 0:34:13.000 --> 0:34:17.000 for future people to discover is directly proportional to how 0:34:17.040 --> 0:34:21.920 suicidal that civilization is, right Like, the more it is 0:34:21.960 --> 0:34:25.439 just burning through fossil fuel resources and the rate of that, 0:34:25.840 --> 0:34:28.480 the stronger the signal will be. And so a civilization 0:34:28.520 --> 0:34:32.160 at some point, they say, well, will naturally tend to 0:34:32.200 --> 0:34:36.120 attenuate for a couple of reasons. Either it realizes it 0:34:36.160 --> 0:34:38.239 can't keep going at that rate, or it's going to 0:34:38.440 --> 0:34:42.000 cause climate damage to itself, so it will naturally switch 0:34:42.040 --> 0:34:45.560 to more sustainable uh energy sources that are harder to 0:34:45.640 --> 0:34:48.239 detect in the future, or it of course does so 0:34:48.320 --> 0:34:51.440 much damage to itself that it's signal naturally is reduced, 0:34:52.040 --> 0:34:54.640 right right. So, so basically coming back to what you 0:34:54.640 --> 0:34:56.600 said earlier, it's not just that there there's gonna be 0:34:56.640 --> 0:34:59.320 a sign. There's gonna be the signal, uh, this footprint 0:34:59.360 --> 0:35:02.120 of a civilized ation, uh in the in the you know, 0:35:02.160 --> 0:35:04.840 the geochemical record. It's it's also that it may just 0:35:04.920 --> 0:35:07.279 be very short. It may be a little it's not 0:35:07.320 --> 0:35:09.880 going to be this. Uh, it's not gonna be a symphony. 0:35:09.960 --> 0:35:12.720 It's going to maybe be a note or two. So basically, 0:35:12.719 --> 0:35:16.319 the idea being that that that a real strong, much 0:35:16.360 --> 0:35:21.000 stronger argument for aliens existing and having some sort of 0:35:21.080 --> 0:35:23.160 role or some sort of advanced technology having some sort 0:35:23.200 --> 0:35:26.400 of role on Earth in the in the ancient history 0:35:26.880 --> 0:35:29.880 would not be look at the pyramids, I think aliens 0:35:29.920 --> 0:35:32.920 did this, or I think, you know, ancient scientists did this. 0:35:33.360 --> 0:35:36.200 It would be pointing at say a blip in uh, 0:35:36.280 --> 0:35:38.960 you know, or an increase in global temperatures during a 0:35:38.960 --> 0:35:41.760 certain period of time and saying, I think the aliens 0:35:41.760 --> 0:35:45.000 did this, or I think the advanced technology in question 0:35:45.040 --> 0:35:47.520 did this. I mean, even then, I think that would 0:35:47.560 --> 0:35:51.040 be a very speculative and and difficult to prove hypothesis. 0:35:51.080 --> 0:35:54.400 It would be kind of just like unfalsifiable speculation, but 0:35:55.120 --> 0:35:59.120 that that would perhaps be the more likely type of 0:35:59.200 --> 0:36:02.640 signal you would find if there had been alien intervention, 0:36:02.760 --> 0:36:12.640 then you know specific artifacts than all right, well, let's 0:36:12.640 --> 0:36:14.560 get into some of the specifics of the footprint that 0:36:14.640 --> 0:36:17.360 the authors lay out here. The first one is a 0:36:17.480 --> 0:36:22.319 stable isotope anomalies of carbon, oxygen, hydrogen, and nitrogen. And 0:36:22.480 --> 0:36:24.720 this is one of the big ones, an estimated point 0:36:24.760 --> 0:36:28.160 five trillion tons of fossil carbon via the burning of 0:36:28.160 --> 0:36:32.360 fossil fuels and warming of the planet. Um they quote, 0:36:32.400 --> 0:36:35.480 we we expect this temperature rise to be detectable and 0:36:35.600 --> 0:36:40.520 surface ocean uh carbonates, notably for Manifera. This is a 0:36:40.600 --> 0:36:44.799 single celled organism with with with a chalky shell. UM. 0:36:44.960 --> 0:36:52.000 Organic biomarkers cave records, such such as stalactites, lake ostracods. 0:36:52.080 --> 0:36:56.760 These are minute aquatic crustaceans and high latitude ice cores, 0:36:57.040 --> 0:36:59.279 though only the first two of these will be a 0:36:59.360 --> 0:37:03.759 retrievable in the time scales considered here. Right, So this 0:37:03.840 --> 0:37:07.360 thing about the the isotope anomalies of of carbon and 0:37:07.440 --> 0:37:09.840 these other elements is very interesting. So they say, you know, 0:37:09.880 --> 0:37:12.920 there are natural distributions that you would find records of 0:37:13.200 --> 0:37:16.359 in the different isotopes of carbon that are that are 0:37:16.480 --> 0:37:20.640 moving around in Earth's atmosphere. But when people suddenly start 0:37:20.680 --> 0:37:25.560 pulling huge amounts of fossil carbon, carbon of a biological 0:37:25.600 --> 0:37:28.640 origin out of the ground and burning it, you suddenly 0:37:28.680 --> 0:37:31.960 start throwing those isotopes out of whack, and that will 0:37:32.000 --> 0:37:35.040 be something that will leave records for millions of years 0:37:35.080 --> 0:37:38.000 to come. So you you can look in the geological records, 0:37:38.040 --> 0:37:40.680 you know, the record of of strata from previous eras, 0:37:40.680 --> 0:37:43.920 and say, huh, for some reason, in this one period 0:37:44.000 --> 0:37:47.359 deep in history, suddenly the carbon isotopes got way out 0:37:47.400 --> 0:37:51.160 of whack, as if suddenly a bunch of fossil carbon 0:37:51.239 --> 0:37:54.000 like coal or oil or whatever had been burned at 0:37:54.000 --> 0:37:57.040 a at a hideous rate into the atmosphere. Right. And 0:37:57.080 --> 0:38:00.080 so you know, looking at our our time now of 0:38:00.080 --> 0:38:02.759 of of modern human civilization, you know this that we 0:38:02.800 --> 0:38:05.719 have this fossil fuel consumption, and we have the invention 0:38:05.800 --> 0:38:09.080 of the haber Bosch process and the large scale use 0:38:09.120 --> 0:38:13.880 of of nitrogenous fertilizers and agriculture, which will also heavily 0:38:13.920 --> 0:38:18.120 impact the planet's nitrogen cycling. Yeah, the haber Bosch process. Yeah, 0:38:18.120 --> 0:38:20.960 as part of the changes in the nitrogen cycle that 0:38:21.000 --> 0:38:24.600 have come about as a result of of industrial civilization 0:38:24.640 --> 0:38:28.600 as well, they also touched on sediment to logical records. 0:38:29.080 --> 0:38:32.400 The key causes here would be major soil erosion brought 0:38:32.440 --> 0:38:38.160 on by agriculture, but also by agriculture related deforestation. Um. Now, 0:38:38.160 --> 0:38:41.359 this would be partially mitigated by dams, they point out, 0:38:41.560 --> 0:38:45.160 but erosion is also heightened by climate changes and thawing 0:38:45.280 --> 0:38:50.320 perma frost. Also sediment content changes due to just industrialization 0:38:50.360 --> 0:38:53.440 in general. Uh. Now, here's a Here's another big one 0:38:53.480 --> 0:38:58.560 that I think will be pretty obvious. Faunnel radiation and extinctions. Um. Basically, 0:38:58.640 --> 0:39:01.040 humans have brought about many extinct actions already, and we're 0:39:01.080 --> 0:39:04.480 living in the midst of an extinction event. Uh. This 0:39:04.520 --> 0:39:08.520 will likely register in the fossil record. Yeah. Now, of course, 0:39:08.840 --> 0:39:13.120 previous major extinction events have usually been chalked up to 0:39:13.480 --> 0:39:17.520 two natural things like uh oh, we can track massive 0:39:17.600 --> 0:39:20.600 vulcanism as as the cause of this one, or say 0:39:20.640 --> 0:39:25.160 a large space impact like the Kti extinction event. But 0:39:25.239 --> 0:39:28.000 there are other extinction events in Earth's history where the 0:39:28.080 --> 0:39:31.680 cause is not totally clear. You know, there are some speculations, 0:39:31.680 --> 0:39:34.120 but we don't know exactly why. Suddenly, it seemed like 0:39:34.160 --> 0:39:37.480 there was a great reduction in marine biodiversity at this 0:39:37.560 --> 0:39:40.200 point in history. All right. The next area is non 0:39:40.320 --> 0:39:44.520 naturally occurring synthetics, so non naturally occurring chemicals generated by 0:39:44.560 --> 0:39:49.719 industrial activity that persists in the environment. Things persistent organic pollutants, 0:39:50.040 --> 0:39:54.160 chlorofluoral carbons, in related compounds. And they also point out 0:39:54.160 --> 0:39:58.840 that steroids, leaf waxes, alkanones, and lipids can be preserved 0:39:58.840 --> 0:40:01.719 in sediment for many millions of years. Now, that one 0:40:01.800 --> 0:40:05.200 naturally makes me think of King plastic baby. Yeah, yeah, 0:40:05.200 --> 0:40:07.920 And that's that's the next thing that they mentioned. And 0:40:07.960 --> 0:40:11.480 this one's you know, this one's disheartening but obvious. We've 0:40:11.520 --> 0:40:15.640 created tons of plastics, tons upon tons upon tons of plastics, 0:40:15.719 --> 0:40:19.120 and they sadly persist not only in heaps and floating masses, 0:40:19.160 --> 0:40:23.959 but inside the bodies of organisms, including ourselves, uh so quote. 0:40:24.000 --> 0:40:29.040 The potential for very long term persistence and detectability is high. Now, 0:40:29.080 --> 0:40:31.040 one of the things they point out about plastic that's 0:40:31.080 --> 0:40:34.759 interesting is that plastics may well prove to be a 0:40:34.880 --> 0:40:38.520 very long term signature of human civilization and the geologic 0:40:38.600 --> 0:40:41.279 record for you know, millions and millions of years to come. 0:40:41.400 --> 0:40:43.839 But the development of plastic is also something they would 0:40:43.880 --> 0:40:46.080 class under the I don't remember the umbrella term they 0:40:46.160 --> 0:40:50.560 use for this sort of chemical contingencies. A technological civilization 0:40:50.640 --> 0:40:54.320 does not have to use plastics. Plastics are just something 0:40:54.400 --> 0:40:57.799 that humans happen to use. There are other things that 0:40:57.880 --> 0:41:03.279 seem probably more universal, like almost any industrial civilization you 0:41:03.280 --> 0:41:07.719 would expect to burn lots of fossil fuels. But plastics, 0:41:07.719 --> 0:41:10.359 that's more of a question mark. Is that unusual that 0:41:10.400 --> 0:41:12.399 we did it, or is that a very common thing 0:41:12.520 --> 0:41:15.800 that the civilizations would do all right. The next area 0:41:15.840 --> 0:41:21.480 that they highlight transuranic elements. These are elements having a 0:41:21.560 --> 0:41:26.160 higher atomic number than uranium, which is ninety two. Most 0:41:26.239 --> 0:41:30.560 radioactive isotopes created via nuclear energy or weaponry have long 0:41:31.000 --> 0:41:33.680 half lives, but not long enough to be a factor 0:41:33.760 --> 0:41:35.960 on the time scale that they're talking about here. But 0:41:36.040 --> 0:41:40.640 the exceptions are plutonium to forty four and M curium 0:41:40.719 --> 0:41:43.880 two forty seven, So plutonium has a half life of 0:41:44.120 --> 0:41:48.120 eight point eight million years, and curium in this case, 0:41:48.200 --> 0:41:50.839 we're talking about a half life of fifteen million years. 0:41:50.880 --> 0:41:54.360 So in sufficient quantities of disposal, these would these would 0:41:54.480 --> 0:41:59.120 pop up. And plutonium has no known natural causes outside 0:41:59.120 --> 0:42:02.400 of an actual bernova or something like that. This isotope 0:42:02.440 --> 0:42:05.560 of plutonium. Yes, this particular yea plutonium two forty four 0:42:05.640 --> 0:42:08.759 so um. So yeah, if you found enough of this 0:42:09.200 --> 0:42:11.840 uh in the geologic record, that would be a sign 0:42:11.920 --> 0:42:14.239 that's that something was at work, there was some sort 0:42:14.280 --> 0:42:20.440 of technological atomic uh enterprise that was in place. Now, 0:42:20.440 --> 0:42:24.160 I guess we've already mentioned earlier that the authors are 0:42:24.200 --> 0:42:27.640 not going to claim that there was in fact a 0:42:27.640 --> 0:42:30.919 a long lost civilization hundreds of millions of years ago. 0:42:31.360 --> 0:42:34.719 But they do actually look at the geologic record to say, 0:42:35.360 --> 0:42:39.319 are there anythings that that match these criteria we've been 0:42:39.320 --> 0:42:42.640 looking at, And they do find some interesting partial matches 0:42:42.719 --> 0:42:45.640 that though of course nothing really comes close to evidence 0:42:45.680 --> 0:42:48.319 that would be conclusive that there actually was a civilization, 0:42:48.360 --> 0:42:52.160 but some of these matches raise interesting questions of their own. Yeah, 0:42:52.400 --> 0:42:54.440 they don't look at everything, and they point out that 0:42:54.480 --> 0:42:56.960 things like the KT extinction event, we know that that 0:42:57.040 --> 0:43:01.440 was not an industrial accident or anything, um and uh. 0:43:01.480 --> 0:43:03.880 And and again they're not arguing that these are evidence 0:43:03.880 --> 0:43:06.680 of past pre human industrial civilizations on Earth, but merely 0:43:06.719 --> 0:43:09.000 point to them as the sources of events we might 0:43:09.080 --> 0:43:12.080 look at. Yeah, and I would say the biggest one 0:43:12.239 --> 0:43:14.840 that they focus on in the paper is the event 0:43:14.920 --> 0:43:18.640 known as the Paleocene Eocene Thermal Maximum or p E 0:43:18.680 --> 0:43:21.880 t M. Yeah. This is an abrupt spike in carbon 0:43:21.960 --> 0:43:27.840 and oxygen isotopes near the Paleocene Eocene transition uh fifty 0:43:27.920 --> 0:43:30.760 six million years ago, resulting in a five to eight 0:43:31.400 --> 0:43:35.439 degree celsius global average temperature rise. This is widely thought 0:43:35.520 --> 0:43:37.640 to be due to well, I think they're there are 0:43:37.640 --> 0:43:41.480 different theories of One is that it's volcanic activity, um. 0:43:41.640 --> 0:43:44.759 But there have also been hypotheses put forth that it 0:43:44.760 --> 0:43:47.200 could have been a common impact. It could be due 0:43:47.200 --> 0:43:52.400 to burning pete methane being released, and a few other candidates. Um. 0:43:52.400 --> 0:43:55.160 It's also used as a means of of understanding and 0:43:55.239 --> 0:43:57.319 kind of like kind of modeling out the effects of 0:43:57.360 --> 0:44:01.080 climate change during our own era. Yeah. And and one 0:44:01.120 --> 0:44:03.520 of the reasons this one gets singled out is, uh 0:44:03.960 --> 0:44:06.520 so it really looks like, Okay, here we're seeing, for example, 0:44:06.560 --> 0:44:10.879 these carbon isotope signature changes that would signal that huge 0:44:10.920 --> 0:44:15.440 amounts of biogenic carbon carbon that originally came from life forms, 0:44:15.480 --> 0:44:17.840 like the stuff you would find in fossil fuels, is 0:44:17.880 --> 0:44:20.879 being burned and released into the atmosphere. Now, how would 0:44:20.960 --> 0:44:24.160 that happen if if if it wasn't creatures from the 0:44:24.160 --> 0:44:27.759 Black Lagoon with leather face masks digging up a bunch 0:44:27.840 --> 0:44:31.040 of fossil fuels and burning them for their civilization. Well, no, 0:44:31.239 --> 0:44:33.880 you probably don't need to jump to that conclusion, because 0:44:33.880 --> 0:44:37.120 there are other solutions on offer, like, for example, there 0:44:37.200 --> 0:44:41.080 might have somehow been lots of access of volcanic magma 0:44:41.320 --> 0:44:45.600 two beds of fossil fuels. Maybe certain types of volcanic 0:44:45.640 --> 0:44:48.960 activity tended to set a light to a lot of 0:44:49.440 --> 0:44:52.719 natural reserves of fossil fuels and shale beds and things 0:44:52.800 --> 0:44:56.200 like that. And this almost acted as if the Earth itself, 0:44:56.280 --> 0:44:58.920 we're we're setting off an industrial revolution, but it was 0:44:59.000 --> 0:45:03.200 just volcano interacting with with these reservoirs of carbon in 0:45:03.239 --> 0:45:06.360 the ground. Yeah, all you need is geologic upheaval and 0:45:06.440 --> 0:45:10.000 volcanic activity. And again um our our planet has a 0:45:10.160 --> 0:45:14.160 as a as a very active geological life, so there's 0:45:14.160 --> 0:45:16.759 plenty of opportunity for this sort of thing to potentially 0:45:16.760 --> 0:45:19.000 have taken place. So it kind of comes back to 0:45:19.000 --> 0:45:21.359 a problem with the signal here, the signal you would 0:45:21.360 --> 0:45:24.120 be looking for in the geochemical record, in many cases, 0:45:24.719 --> 0:45:27.520 the very sort of signal we're looking for especially concerning 0:45:27.560 --> 0:45:30.080 carbon and warming, could have also been caused by these 0:45:30.160 --> 0:45:33.640 naturally occurring causes, and so strong signals might be coming 0:45:33.680 --> 0:45:36.719 from something else, and more specific signals that we might 0:45:36.760 --> 0:45:39.759 look to just might be too weak to to ever 0:45:39.880 --> 0:45:42.600 possibly observe or to really make much out of. Oh yeah, 0:45:42.800 --> 0:45:44.960 this is an interesting paradox they talk about in their 0:45:44.960 --> 0:45:47.200 conclusion of all of the criteria they're able to come 0:45:47.280 --> 0:45:50.000 up with in this framework for for looking for past 0:45:50.080 --> 0:45:55.239 industrial civilizations, the stuff that you would expect any industrial 0:45:55.320 --> 0:46:00.680 civilization to do also has other explanations, and so so 0:46:00.719 --> 0:46:04.040 it's not conclusive that it was an industrial civilization that 0:46:04.160 --> 0:46:07.200 this would be things like, you know, the carbon stuff. Meanwhile, 0:46:07.360 --> 0:46:10.720 the stuff that would be really strong evidence of of 0:46:11.080 --> 0:46:16.279 an intelligent civilization origin, that stuff that civilizations might not do. 0:46:16.480 --> 0:46:19.200 It's more contingent things like plastics and stuff. You know, 0:46:19.480 --> 0:46:22.200 you could have a civilization without plastics. That's not a 0:46:22.320 --> 0:46:26.680 necessary milestone in the in the progress of energy harnessing, 0:46:27.080 --> 0:46:29.160 and maybe it's even the sort of thing, uh, an 0:46:29.200 --> 0:46:31.799 advance civilization would move away from. Coming back to that 0:46:32.080 --> 0:46:36.200 the sustainability paradox, when one could hope, I imagine now 0:46:36.400 --> 0:46:39.839 the authors again they're very clear about just how far 0:46:39.880 --> 0:46:43.920 you should take this hypothesis, stating that quote the Silarian 0:46:44.000 --> 0:46:48.319 hypothesis cannot be regarded as likely merely because no other 0:46:48.440 --> 0:46:53.000 valid idea presents itself. Uh So they admit that this 0:46:53.000 --> 0:46:54.560 this sort of thing could easily get out of hand 0:46:54.560 --> 0:46:57.000 with folks pointing to any sort of signal in the 0:46:57.040 --> 0:47:01.560 geochemical record as being possible proof of human technological societies. 0:47:02.040 --> 0:47:04.600 If you're doing that, you're you're really taking it and 0:47:04.640 --> 0:47:07.560 running with in the wrong direction. Yeah, I guess that's 0:47:07.600 --> 0:47:10.920 one of the frustrating things about about interesting work of 0:47:10.920 --> 0:47:12.880 this kind is so you can point out a lot 0:47:12.920 --> 0:47:18.120 of the ways that it's difficult to rule out past civilizations. 0:47:18.239 --> 0:47:20.560 But then for a lot of people who just want 0:47:20.680 --> 0:47:24.160 to have a theory that changes everything, you know, for 0:47:24.200 --> 0:47:26.600 a lot it's just like it's fun to believe that. 0:47:26.960 --> 0:47:28.840 So a lot of people just want to believe it. 0:47:28.880 --> 0:47:30.880 I want to believe, you know, that there was an 0:47:30.920 --> 0:47:34.320 Atlantis mother civilization that birthed everything, or I want to 0:47:34.360 --> 0:47:37.480 believe that there were aliens on Earth before humans or 0:47:37.520 --> 0:47:40.359 anything like that, because that would change everything, and it 0:47:40.400 --> 0:47:44.920 feels so cool to believe it. Therefore, becomes your default belief, 0:47:45.080 --> 0:47:47.920 and so thus a paper that says, well, it's more 0:47:47.960 --> 0:47:50.560 difficult to rule out that kind of thing than you 0:47:50.640 --> 0:47:55.160 might think. Uh, some people can erroneously conclude that that 0:47:55.280 --> 0:47:57.560 is in fact evidence for the thing they want to 0:47:57.600 --> 0:48:03.359 believe because it feels cool. It's not positive evidence for it, yes, yeah, absolutely, 0:48:03.840 --> 0:48:06.360 um yes, So so you know, they argue that that 0:48:06.440 --> 0:48:09.720 we need to to further research you know, the likely 0:48:09.800 --> 0:48:14.439 signature uh left by our own um Anthropocene era, as 0:48:14.440 --> 0:48:18.319 well as a deeper exploration of the elemental and um 0:48:18.480 --> 0:48:23.680 compositional anomalies that we find in extant sediments. Basically, we 0:48:23.760 --> 0:48:27.040 look at past events mainly with stuff like impacts in mind, 0:48:27.719 --> 0:48:31.200 but perhaps the Silarian hypothesis needs to be at least 0:48:31.200 --> 0:48:34.239 on the table as well. Not because again we think 0:48:34.320 --> 0:48:37.799 it is, you know, actually a valid explanation for what 0:48:37.880 --> 0:48:41.480 has happened. Um, you know, ultimately it's an outside possibility, 0:48:41.920 --> 0:48:44.600 not a conclusion we should jump to, but perhaps it 0:48:44.600 --> 0:48:46.719 should just be part of sort of the spectrum of 0:48:46.760 --> 0:48:51.680 possibilities there again, not because we think it happened, but because, uh, 0:48:51.800 --> 0:48:53.160 it gives us a little more of a sort of 0:48:53.160 --> 0:48:57.359 a robust spectrum. And how to interpret these things and 0:48:57.360 --> 0:48:59.799 and then moving forward to you know, potentially considering other worlds, 0:48:59.840 --> 0:49:02.960 looking at other planets like even Mars. Uh. It gives 0:49:03.040 --> 0:49:06.520 us one more tool, one more UH way to look 0:49:06.560 --> 0:49:10.080 at the evidence. Yeah, exactly. They're not arguing this because 0:49:10.120 --> 0:49:13.520 they think there was a civilization. It's that we should 0:49:13.600 --> 0:49:17.399 consider these possibilities when looking at planets, even including our own, 0:49:17.680 --> 0:49:19.960 and know what we would look for if we wanted 0:49:20.000 --> 0:49:23.040 to consider that possibility, right, Because ultimately this is not 0:49:23.080 --> 0:49:28.960 a supernatural explanation. This is ultimately, you know, a natural hypothesis. 0:49:29.440 --> 0:49:33.719 But but it is admittedly an outside possibility. Now, of 0:49:33.719 --> 0:49:36.200 course we're here talking about reasons why you shouldn't just 0:49:36.320 --> 0:49:40.520 jump to the conclusion of a Salurian civilization. But but 0:49:40.560 --> 0:49:43.160 there are also some arguments against it in some of 0:49:43.160 --> 0:49:46.560 the specific events that they look at. For example, if 0:49:46.640 --> 0:49:50.759 you know, maybe the best possibility is this interesting event 0:49:50.840 --> 0:49:54.160 in Earth history, the Paleocene Eocene thermal maximum. More suddenly 0:49:54.200 --> 0:49:57.560 there was there was rapid global warming and UH and 0:49:58.000 --> 0:50:01.239 these in these chemical changes like with carbon isotopes. They 0:50:01.560 --> 0:50:07.080 even put some arguments back against considering UH civilization as 0:50:07.239 --> 0:50:10.840 a cause of this global warming in Earth's history. Because 0:50:10.880 --> 0:50:14.400 they say, look, the kind of global warming caused by 0:50:14.400 --> 0:50:18.600 our civilization is happening in an incredibly rapid fashion over 0:50:18.719 --> 0:50:22.359 just a few hundred years. This actually, though it's it's 0:50:22.560 --> 0:50:26.800 relatively rapid in geologic terms. The the p et M 0:50:26.880 --> 0:50:31.359 actually happened probably over hundreds of thousands of years, which 0:50:31.520 --> 0:50:35.719 which is incredibly slow if you're imagining that civilization was 0:50:35.760 --> 0:50:38.320 the cause of it, right, if you're if you're comparing 0:50:38.320 --> 0:50:41.920 it to the model of of human industrial advancement, it's 0:50:41.920 --> 0:50:44.279 incredibly slow. So there's not only the point that you 0:50:44.320 --> 0:50:47.279 shouldn't just jump to the conclusion of there was a 0:50:47.360 --> 0:50:50.080 law civilization because it feels cool, but like in the 0:50:50.160 --> 0:50:52.960 specific instances they look at, there are some reasons for 0:50:53.200 --> 0:50:56.319 thinking that's probably not true. I don't know, I guess 0:50:56.400 --> 0:51:00.839 unless those civilizations were like just really lazy. I mean, 0:51:00.880 --> 0:51:02.959 you can sort of, you know, pull out your sci 0:51:03.000 --> 0:51:05.279 fi hat and and put it on and come up 0:51:05.320 --> 0:51:07.520 with various ideas of, you know, for why they might 0:51:07.560 --> 0:51:09.919 have been this way. Maybe they were super long lived. Yeah, 0:51:09.920 --> 0:51:12.239 they weren't very ambitious, and they're like this, note, this 0:51:12.320 --> 0:51:15.320 is the right level of industrialization, and we want to, uh, 0:51:15.440 --> 0:51:18.040 we need to keep going at this rate. I don't know, 0:51:18.480 --> 0:51:22.279 they didn't reproduce all that much. I don't know. I 0:51:22.320 --> 0:51:26.160 mean that that's ultimately one of the problems with with imagining, uh, 0:51:26.200 --> 0:51:30.400 you know, other life forms. It's like it's just you know, 0:51:30.440 --> 0:51:33.040 it's you can you can make a case for any 0:51:33.120 --> 0:51:37.080 number of things, um and and try and make it 0:51:37.120 --> 0:51:40.239 fit your your hypothesis. And of course that's not really 0:51:40.239 --> 0:51:41.880 the way to go about it, I mean, not in 0:51:42.000 --> 0:51:46.000 from a scientific perspective, from a sci fi dreaming creative perspective, yeah, 0:51:46.080 --> 0:51:50.680 go for it. Um So, though I guess it does 0:51:50.760 --> 0:51:52.320 kind of come down to the conundrum two at the 0:51:52.400 --> 0:51:55.040 end of the day, like like when does when does 0:51:55.040 --> 0:51:59.239 mere creativity and um and dream weaving become this kind 0:51:59.239 --> 0:52:02.080 of corrupt of our thought and uh and and a 0:52:02.120 --> 0:52:05.520 pollution of our ability to understand our place in the 0:52:05.560 --> 0:52:07.960 world and are where we're going in the future and 0:52:07.960 --> 0:52:10.000 where we were in the past. Well, you know, I 0:52:10.080 --> 0:52:13.520 feel like a thread without maybe intending intending to do so, 0:52:13.560 --> 0:52:15.640 that we've pursued a good bit on this podcast is 0:52:16.040 --> 0:52:21.080 understanding the ideally the difference between your sort of interest 0:52:21.120 --> 0:52:25.640 and imagination and your epistemology. That like that an idea. 0:52:25.800 --> 0:52:28.960 You can like an idea because it's interesting and cool, 0:52:29.480 --> 0:52:33.360 and that doesn't necessarily mean it's true. You know that, 0:52:33.600 --> 0:52:36.680 like that, your your epistemology is probably best to based 0:52:36.680 --> 0:52:39.719 on evidence, and you should be skeptical of things that 0:52:39.760 --> 0:52:42.840 you want to believe because you like them and so forth. 0:52:43.120 --> 0:52:45.920 But it's still totally valid to like, say, be interested 0:52:45.960 --> 0:52:49.000 in the bicameral mind or whatever because it's a fun idea, 0:52:49.520 --> 0:52:52.040 even if you know, you probably accepted as you know, 0:52:52.080 --> 0:52:54.759 there's not a lot of evidence for it, right right, 0:52:54.800 --> 0:52:56.400 You can you can alpoly engage in a number of 0:52:56.480 --> 0:52:59.440 these ideas as as more as art than science, and 0:52:59.520 --> 0:53:01.719 there there's nothing wrong with that. Is when you start 0:53:01.880 --> 0:53:04.680 arguing that your art is science, that's where you can 0:53:04.680 --> 0:53:07.719 get into into some trouble. Um. I was reminded in 0:53:07.760 --> 0:53:12.080 all of this of Carl Sagan's approach to ancient aliens 0:53:12.239 --> 0:53:15.200 and ancient astronauts, particularly in the book that he co 0:53:15.320 --> 0:53:20.279 authored with Joseph Shklovsky Intelligent Life in the Universe. Um. 0:53:20.719 --> 0:53:23.640 The in in this particular book, you know, the the 0:53:24.080 --> 0:53:26.720 examine this idea. They said, okay, here's the speculative idea, 0:53:26.800 --> 0:53:29.000 and we don't have evidence that had ever happened, But 0:53:29.040 --> 0:53:31.839 if it were to have happened, what sorts of specific 0:53:31.880 --> 0:53:34.560 evidence might we look for? And in this case, we're 0:53:34.560 --> 0:53:38.359 talking about signs that are evident in ancient religions and 0:53:38.520 --> 0:53:41.800 uh and so forth. Uh. And I thought that was 0:53:41.840 --> 0:53:45.400 a great treatment of that question. Uh and against Sagan's 0:53:45.400 --> 0:53:48.520 treatment reminds me of the treatment given in this paper 0:53:48.560 --> 0:53:51.239 by these authors. But of course Segand had to come 0:53:51.239 --> 0:53:54.760 back and continue to argue with the ancient alien people 0:53:55.320 --> 0:53:57.040 who were you know, very much going off in their 0:53:57.080 --> 0:54:00.960 own directions, yeah, and pushing pushing art as science, and 0:54:01.000 --> 0:54:03.440 Sagan having to remind them like, no, I love art 0:54:03.480 --> 0:54:06.000 as much as the next guy. But here's how we 0:54:06.000 --> 0:54:09.680 approach this from a scientific perspective. Well, I mean, I 0:54:09.680 --> 0:54:12.480 think the important thing about this stuff, like Sagan's work 0:54:12.520 --> 0:54:14.640 on that or or or the paper we're looking at here, 0:54:14.680 --> 0:54:17.360 is it's good too when you're when you're exploring it 0:54:17.440 --> 0:54:20.920 like a tantalizing and juicy idea. It's a good idea 0:54:21.000 --> 0:54:25.160 to have criteria for what would be good evidence of 0:54:25.360 --> 0:54:29.240 such a thing before you're actually looking at individual evidence 0:54:29.280 --> 0:54:31.480 in cases, because if you look at the evidence first 0:54:31.560 --> 0:54:33.920 and then you try to come up with criteria. You're 0:54:33.920 --> 0:54:36.440 gonna have a tendency to want to fit your criteria 0:54:36.480 --> 0:54:39.560 to whatever evidence you've already got. The cherry picking model 0:54:40.480 --> 0:54:43.440 or what is it the other name of the barn 0:54:43.520 --> 0:54:46.520 wall fallacy or something like that. Remember, the idea is like, 0:54:46.560 --> 0:54:48.840 you know, somebody says, you know, I'm a great shot, 0:54:48.880 --> 0:54:50.560 and so they shoot at the side of a barn 0:54:50.800 --> 0:54:52.719 and then they go up, they walk up to their 0:54:52.719 --> 0:54:54.880 bullet hole, and then they draw a bull's eye perfectly 0:54:54.920 --> 0:54:57.319 around it. That's that's a great point. That's that's a 0:54:57.320 --> 0:54:59.480 great way of looking at it. All Right, Well, I 0:54:59.520 --> 0:55:01.400 guess we're good and go ahead and wrap this episode up. 0:55:01.400 --> 0:55:03.400 But we'd love to hear from everyone out there. I 0:55:03.719 --> 0:55:06.000 love to hear from any doctor who fans who have 0:55:07.040 --> 0:55:11.280 some additional information they want to share about the Silurians 0:55:11.320 --> 0:55:15.040 and various related um species that have popped up in 0:55:15.120 --> 0:55:19.360 that show. And perhaps you have specific thoughts about about 0:55:19.600 --> 0:55:22.719 you know, just this this basic you know view uh 0:55:22.760 --> 0:55:27.319 and what it reveals about humanities uh place on Earth 0:55:27.440 --> 0:55:32.320 right now, and what technological civilization is doing to the planet, 0:55:32.680 --> 0:55:35.200 and just you know, ultimately what kind of a you know, 0:55:35.239 --> 0:55:37.880 a small blip a week signal we may be in 0:55:37.920 --> 0:55:41.160 the future, as opposed to this kind of lasting thing 0:55:41.320 --> 0:55:45.520 that we sometimes imagine that human civilization is. I'm going 0:55:45.560 --> 0:55:49.000 to say, I hope that I'll be optimistic, so I 0:55:49.000 --> 0:55:51.719 hope we do stick around. I hope we attenuate the 0:55:51.840 --> 0:55:55.240 kinds of geologic signal we leave due to climate change 0:55:55.239 --> 0:55:57.880 and chemical alteration of the atmosphere and all you know, 0:55:58.040 --> 0:56:01.560 stuff like that, uh, and heavy metal pollutions and things, 0:56:01.640 --> 0:56:04.720 and that we the signal of our civilization can always 0:56:04.760 --> 0:56:07.759 be charted against the geologic record because of the continuance 0:56:07.840 --> 0:56:11.000 of Doctor Who Seasons. So when we're on the like, 0:56:11.080 --> 0:56:13.759 you know, eventually we'll get into the exponential notation of 0:56:13.760 --> 0:56:17.799 the Doctor Who Seasons. Yeah, yeah, yeah. Well, one day 0:56:18.080 --> 0:56:21.360 some sort of ancient U, or rather some sort of 0:56:21.600 --> 0:56:24.640 far flung future civilization will look back and say, look, 0:56:25.320 --> 0:56:27.799 clearly they knew what they were doing. Uh, they were 0:56:27.840 --> 0:56:31.360 able to do you know, some three million years of 0:56:31.400 --> 0:56:34.200 Doctor Who. Though maybe at a certain point the doctor 0:56:34.200 --> 0:56:36.520 will be a robot and the enemies will be will 0:56:36.600 --> 0:56:40.719 be organics, and I don't know, Yeah, I wonder at 0:56:40.760 --> 0:56:42.759 what point do we get a robot doctor? I mean, 0:56:42.760 --> 0:56:46.400 they they're they've only recently really been been been mixing 0:56:46.480 --> 0:56:49.920 up the casting on that role. Al right, well, let 0:56:49.960 --> 0:56:51.799 us know in the meantime if you want to listen 0:56:51.800 --> 0:56:53.480 to other episodes of Stuff to Blow Your Mind, we 0:56:53.520 --> 0:56:55.800 have core episodes on Tuesdays and Thursdays and the Stuff 0:56:55.840 --> 0:56:59.080 to Blow your Mind podcast feed. On Monday's we do 0:56:59.120 --> 0:57:02.280 listener Mail, where we hear from from you, the listeners, 0:57:02.560 --> 0:57:05.520 and we read your various listener mails, always a good time. 0:57:05.840 --> 0:57:08.879 On Wednesday's we do a short form artifact or monster fact, 0:57:08.920 --> 0:57:11.200 and then on Friday's we do Weird How Cinema. That's 0:57:11.239 --> 0:57:14.839 our time to set aside most serious issues and just 0:57:14.880 --> 0:57:18.200 talk about a weird film. Huge thanks as always to 0:57:18.240 --> 0:57:21.520 our excellent audio producer Seth Nicholas Johnson. 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