WEBVTT - From the Vault: The Silurian Hypothesis 0:00:05.840 --> 0:00:08.399 Hey, welcome to Stuff to Blow Your Mind. My name 0:00:08.400 --> 0:00:11.479 is Robert Lamb and I'm Joe McCormick, and it's Saturday. 0:00:11.560 --> 0:00:13.920 Time to dig into the vault for an older episode 0:00:13.920 --> 0:00:18.720 of the show. This is our episode on the Silurian hypothesis, 0:00:18.760 --> 0:00:28.040 originally published January. I hope you enjoy Welcome to Stuff 0:00:28.080 --> 0:00:37.360 to Blow Your Mind production of My Heart Radio. Hey, 0:00:37.479 --> 0:00:39.600 welcome to Stuff to Blow Your Mind. My name is 0:00:39.680 --> 0:00:43.920 Robert Lamb and I'm Joe McCormick, and today we're going 0:00:43.960 --> 0:00:46.720 to be talking about a subject that I've actually had 0:00:46.760 --> 0:00:48.960 on the radar for a while. This is something that 0:00:49.120 --> 0:00:52.800 was making the rounds on science blogs a few years back, 0:00:53.280 --> 0:00:56.360 and it has been suggested by a number of different listeners. 0:00:56.360 --> 0:00:58.760 So I'm glad we're finally coming around to it. I 0:00:58.800 --> 0:01:00.800 think I had some hesitation for a while that I 0:01:00.800 --> 0:01:03.800 want to briefly explain right at the beginning here. But 0:01:03.880 --> 0:01:07.600 today we're gonna be talking about an idea known as 0:01:07.680 --> 0:01:11.840 the Silurian hypothesis. Uh. And just to give you a 0:01:11.880 --> 0:01:15.280 little bit of background knowledge, we spent several minutes before 0:01:15.319 --> 0:01:18.760 recording today trying to look up how they pronounced silurian 0:01:19.000 --> 0:01:21.560 on Doctor Who because I was like, sure they might 0:01:21.640 --> 0:01:25.280 use some kind of British English variation where they say Silurian, 0:01:26.280 --> 0:01:29.200 but but a last we could not ever get the 0:01:29.240 --> 0:01:31.480 doctor to say it right. I watched I think, an 0:01:31.640 --> 0:01:34.520 entire scene where one of the more recent doctors was 0:01:34.640 --> 0:01:38.800 chatting with a Silurian or Silurian out out of your Will, 0:01:39.040 --> 0:01:41.440 and they they it was like they were trying not 0:01:41.480 --> 0:01:43.520 to say it, like if they said it, one would 0:01:43.680 --> 0:01:45.800 would pop up and and crawl out of the screen 0:01:45.920 --> 0:01:49.280 or something. Uh they used they referred to another alien race. 0:01:49.320 --> 0:01:51.400 There wasn't even in the scene, and I don't even 0:01:51.400 --> 0:01:54.240 think was part of that episode. And then in all 0:01:54.240 --> 0:01:56.520 these other terms, but yeah, they were just trying to 0:01:56.520 --> 0:01:59.280 mess with me. So this is a topic that I 0:01:59.400 --> 0:02:02.600 have been interested in covering for quite a while. It's 0:02:02.720 --> 0:02:05.080 it's been a few years now, but Rob, when you 0:02:05.160 --> 0:02:09.280 suggested it, I realized that I'd always been hesitating and 0:02:09.600 --> 0:02:11.680 not wanting to quite go ahead with it. And I 0:02:11.720 --> 0:02:14.080 think I realized the reason for that, which is that 0:02:14.160 --> 0:02:17.960 when I saw people mentioning this paper on the internet, 0:02:18.480 --> 0:02:20.320 it was clear to me that a lot of them 0:02:20.400 --> 0:02:23.960 were getting exactly the wrong takeaway from it, Like they 0:02:23.960 --> 0:02:27.560 were latching onto a very shallow understanding of the concept 0:02:28.120 --> 0:02:30.919 and and running off in a in a very different 0:02:30.919 --> 0:02:34.520 direction than the authors intended. Not only a different direction 0:02:34.560 --> 0:02:37.680 than they intend, but a direction they specifically say do 0:02:37.760 --> 0:02:40.600 not go in, and specifically say that they are not 0:02:40.720 --> 0:02:44.520 trying to to make yeah. Uh So, to to clarify 0:02:44.560 --> 0:02:48.760 what we're talking about here, the Silurian hypothesis paper begins 0:02:48.800 --> 0:02:52.440 with a fascinating question, in the words of the author's quote, 0:02:52.960 --> 0:02:57.480 if an industrial civilization had existed on Earth many millions 0:02:57.480 --> 0:03:01.480 of years prior to our own era, what traces would 0:03:01.480 --> 0:03:05.240 it have left and would they be detectable today? That 0:03:05.240 --> 0:03:07.360 that's the question at the heart of this paper. And 0:03:07.440 --> 0:03:11.120 obviously this is a tantalizing premise. You know, it sets 0:03:11.160 --> 0:03:15.200 your mind racing with images of impossibly weird organisms, you know, 0:03:15.560 --> 0:03:19.240 like land dwelling octopi and stuff in the in their 0:03:19.240 --> 0:03:22.280 own weird cities, and and what kind of technology would 0:03:22.280 --> 0:03:24.560 they have? Things that are as alien as anything you 0:03:24.560 --> 0:03:28.280 could imagine on another planet, except they would have all 0:03:28.360 --> 0:03:33.040 been from here, native to planet Earth, dating back millions 0:03:33.080 --> 0:03:36.880 of years into prehistory. But while this is a really 0:03:36.920 --> 0:03:41.680 attractive imaginative exercise, I think the first order of business 0:03:41.720 --> 0:03:43.920 when talking about this subject is to be clear that 0:03:44.000 --> 0:03:48.000 the Silurian hypothesis paper is about coming up with a 0:03:48.120 --> 0:03:54.480 framework for detecting physical traces of industrial civilizations and understanding 0:03:54.560 --> 0:03:58.120 how long those traces last. So it's about trying to 0:03:58.120 --> 0:04:00.720 say what are the right questions to ask when you're 0:04:00.840 --> 0:04:02.840 when you're looking at a planet and saying, how could 0:04:02.840 --> 0:04:05.160 we tell if there had been a civilization on this 0:04:05.240 --> 0:04:08.040 planet a long time ago. It is not a paper 0:04:08.200 --> 0:04:12.480 arguing that there was in fact a lost civilization deep 0:04:12.480 --> 0:04:17.200 in Earth's past. So it's not evidence for lizardman, ancient aliens, 0:04:17.600 --> 0:04:21.400 Graham Hancock, Junk Atlantis, or any of that stuff. But 0:04:21.839 --> 0:04:23.880 I would say in its true form, it is a 0:04:24.000 --> 0:04:29.600 really interesting question. Yeah, and at hard this episode is 0:04:29.600 --> 0:04:32.000 is not going to be about scientific evidence for lizardman 0:04:32.080 --> 0:04:34.480 civilizations in the Hollow Earth. So if you're looking for that, 0:04:34.560 --> 0:04:37.200 this is this is not the episode for you. But yeah, 0:04:37.240 --> 0:04:38.520 what I love about it is that it takes this 0:04:38.640 --> 0:04:42.120 sort of fantastic idea and then examines it reasonably, and 0:04:42.200 --> 0:04:49.600 that examination illuminates some very interesting geologic, climatic and astrophysical considerations. So, 0:04:49.960 --> 0:04:54.200 you know, setting aside pseudoscience and pseudo archaeology here. But 0:04:54.279 --> 0:04:56.800 on the other hand, I think if you if you're 0:04:56.800 --> 0:04:59.839 looking for some sci fi fund this topic in this episode, 0:04:59.839 --> 0:05:04.160 well also still engage you. Um. But it is interesting 0:05:04.200 --> 0:05:07.200 how from a certain perspective you can imagine people being 0:05:07.279 --> 0:05:09.880 drawn into it by just sort of this sci fi idea, 0:05:10.320 --> 0:05:13.640 this idea that does lean lend itself well to sort 0:05:13.680 --> 0:05:18.000 of conspiracy theorist mindsets, and then realizing actually, this paper 0:05:18.240 --> 0:05:22.400 is about geology and uh and uh and in the 0:05:22.480 --> 0:05:25.520 last year of our planet and also uh, I guess 0:05:25.600 --> 0:05:27.240 kind of you know, in many cases, kind of a 0:05:27.279 --> 0:05:33.320 downbeat message about the lasting impact of human technology on 0:05:33.360 --> 0:05:36.839 our planet. And on the other hand, too, how forgettable 0:05:36.880 --> 0:05:41.360 we may be from the standpoint of geological history. Yeah, 0:05:41.760 --> 0:05:43.880 so if you're on board for all of that, you've 0:05:43.920 --> 0:05:47.120 come to the right place. So real quick, I do 0:05:47.160 --> 0:05:50.800 want to just discuss the Doctor Who reference here, since 0:05:51.040 --> 0:05:55.200 since uh the author's Schmidt and Frank took the name 0:05:55.360 --> 0:05:58.960 for the hypothesis from the Doctor Who species the Silurians 0:05:59.000 --> 0:06:03.120 who first popped in the nineteen seventies series Doctor Who, 0:06:03.240 --> 0:06:06.839 and these Silarians, I think now you've got me saying Silarians. Oh, 0:06:06.920 --> 0:06:12.240 I'm sorry, I'm probably well. It gets even worse because 0:06:12.400 --> 0:06:15.200 so they take the name of the hypothesis from this 0:06:15.320 --> 0:06:18.640 Doctor Who series where these creatures show up. But then 0:06:18.680 --> 0:06:21.080 they say explicitly in the paper, you know, the range 0:06:21.160 --> 0:06:23.720 we would really be looking at would actually be after 0:06:23.880 --> 0:06:28.320 the Silurian geologic periods. Silurian period is something that's like 0:06:28.360 --> 0:06:32.120 a roughly twenty million year period. That's more than four 0:06:32.200 --> 0:06:34.520 hundred million years ago. I don't know, it's like four 0:06:34.600 --> 0:06:37.200 hundred and forty something to four hundred and twenty something, 0:06:37.240 --> 0:06:40.640 I think roughly. But if you were seriously looking for 0:06:40.720 --> 0:06:44.719 evidence of lost civilizations in Earth's ancient past, you'd probably 0:06:44.760 --> 0:06:47.760 be looking for things like after about four hundred million 0:06:47.839 --> 0:06:50.080 years ago, coming you know, forward in time from the 0:06:50.080 --> 0:06:54.600 Devonian period, when you could have the reasonable biological basis 0:06:54.680 --> 0:07:00.719 for land dwelling animals that might have evolved complex technological intelligence. Yes, uh, 0:07:00.760 --> 0:07:04.080 but at any rate. In Doctor Who, especially in that 0:07:04.320 --> 0:07:09.600 original nineteen seventy uh appearance, the Silurians are these kind 0:07:09.600 --> 0:07:12.520 of lizard men um. They factor into this plot with 0:07:12.600 --> 0:07:15.800 the Third Doctor played by John Perkway who lived nineteen 0:07:15.840 --> 0:07:20.080 nine six, and then they subsequently pop up again with 0:07:20.200 --> 0:07:23.320 the fifth Doctor played by Peter Davison and the eleventh 0:07:23.320 --> 0:07:26.360 Doctor played by Matt Smith, and then more recently the 0:07:26.440 --> 0:07:29.560 third teenth Doctor played by Jody Whittaker. So this is 0:07:29.600 --> 0:07:31.440 just the TV show. I can't speak to the various 0:07:31.480 --> 0:07:33.920 books and audio dramas that have come out, and their 0:07:33.920 --> 0:07:36.920 look has changed throughout the film. Um. You know, they are, 0:07:37.000 --> 0:07:40.840 in essence, this cold blooded, prehistoric reptile like species with 0:07:40.960 --> 0:07:45.240 significant technological advancement that they I think they end up 0:07:45.360 --> 0:07:49.200 entering various states of suspended animation to avoid uh you know, 0:07:49.280 --> 0:07:52.880 major changes on Earth, changes to the climate, etcetera. Um, 0:07:53.000 --> 0:07:57.360 and then they re emerge and encounter the Doctor. Um. 0:07:57.480 --> 0:08:01.720 So yeah, they're They're one of the many interesting alien 0:08:01.880 --> 0:08:05.840 and otherworldly species that pop up. Uh. Though I guess 0:08:05.960 --> 0:08:08.240 with the Silurians one of the key things is that 0:08:08.320 --> 0:08:12.000 they're they're not pure aliens. They're they're sort of the originals. 0:08:12.280 --> 0:08:16.200 There are their original terrans, original earthlings, uh, that are 0:08:16.240 --> 0:08:20.000 then encountered by these evolved apes that come much later. 0:08:20.360 --> 0:08:23.520 I mean to to them, we are the aliens, yeah, right, 0:08:23.600 --> 0:08:27.360 were like these weird future creatures. Uh the image you 0:08:27.360 --> 0:08:30.480 would tell And I gotta be honest, I'm not a hoovoid, 0:08:30.600 --> 0:08:34.520 so I don't know the lore. But the picture you're 0:08:34.520 --> 0:08:37.800 showing me of the Silurians, they look like they look 0:08:37.920 --> 0:08:41.439 like if the world was all creature from the Black 0:08:41.520 --> 0:08:45.560 Lagoon and there was a leather face of the creature 0:08:45.600 --> 0:08:49.880 from the Black Lagoon civilization. Yeah. I mean, they're definitely 0:08:49.960 --> 0:08:52.920 Doctor Who creatures of this era, which which I tend 0:08:53.000 --> 0:08:55.240 to love these costumes. I know they were working with 0:08:55.240 --> 0:08:58.880 with with with budget limitations here, but yeah, the the 0:08:58.920 --> 0:09:03.120 aliens and robot of this era really really called me. Now. 0:09:03.440 --> 0:09:05.439 You said they look kind of fish like. Bear in mind, 0:09:05.559 --> 0:09:08.400 and I'm sure some Doctor Who listeners Doctor Who viewers 0:09:08.400 --> 0:09:10.840 will will will chime in here. But I believe they 0:09:10.840 --> 0:09:13.559 are related to another species that pops up on the 0:09:13.600 --> 0:09:15.480 show that live in the water. I think they're like 0:09:15.520 --> 0:09:19.280 the sea devils or something. Um, but these guys are 0:09:19.320 --> 0:09:21.839 not aquatic in nature. I think I got that right. 0:09:22.120 --> 0:09:24.679 The seed of Oh wait, this is that like a 0:09:24.760 --> 0:09:30.200 bunch of intelligent euryptorids or something something like that. Yeah, alright, 0:09:30.240 --> 0:09:34.160 so this is two thousand eighteen paper, the Silurian hypothesis. 0:09:34.160 --> 0:09:37.400 Would it be possible to detect an industrial civilization in 0:09:37.440 --> 0:09:41.079 the Geological Record. This was published in the journal International 0:09:41.200 --> 0:09:45.840 Journal of Astrobiology. UH. It draws its name from that 0:09:46.080 --> 0:09:48.640 Doctor Who episode, and the authors here that they point 0:09:48.640 --> 0:09:51.280 out that they may be the first to seriously consider 0:09:51.520 --> 0:09:55.120 whether a technologically advanced civilization could have evolved prior to 0:09:55.160 --> 0:09:58.640 Homo sapiens on Earth, though the authors due stress that 0:09:58.679 --> 0:10:01.040 this is a to the best of the knowledge situation, 0:10:01.120 --> 0:10:04.160 So you know, it's entirely possible somebody was batting around 0:10:04.160 --> 0:10:07.079 the idea of previously, but this may be the first, 0:10:07.120 --> 0:10:09.200 and certainly this was this one really made a splash 0:10:09.240 --> 0:10:11.920 when it came out. Okay, So the two authors here 0:10:11.920 --> 0:10:15.560 would be Adam Frank and Gavin A. Schmidt right and 0:10:15.640 --> 0:10:19.160 Frank is a is a physicist and astronomer, and Schmidt 0:10:19.320 --> 0:10:23.479 is a climate scientist right right. Schmidt is a climatologist, 0:10:23.559 --> 0:10:26.520 climate model and director of the NASA Goddard Institute for 0:10:26.559 --> 0:10:28.920 Space Studies in New York and co founder of the 0:10:28.960 --> 0:10:34.000 award winning climate science blog Real Climate. Frank is a physicist, astronomer, 0:10:34.080 --> 0:10:36.320 and writer whose work has appeared in such publications as 0:10:36.360 --> 0:10:38.559 The New York Times and NPR. And I believe we've 0:10:38.559 --> 0:10:41.560 actually referenced his work on the podcast before. Uh. He 0:10:41.640 --> 0:10:44.400 also has a book. He has a few books, including 0:10:44.440 --> 0:10:47.680 The Constant Fire, The End of the Beginning, and Light 0:10:47.720 --> 0:10:50.839 of the Stars. Those are all nonfiction science books, of course. 0:10:51.320 --> 0:10:53.920 So to be clear, we're talking about two very legitimate 0:10:53.920 --> 0:10:57.720 scientists and science communicators, not you know, not a couple 0:10:57.760 --> 0:11:00.800 of of quacks who were staring into the hollow Earth 0:11:00.920 --> 0:11:03.720 or anything. So the authors here begin with a very 0:11:03.800 --> 0:11:07.640 reasonable consideration of the search for intelligent life elsewhere in 0:11:07.679 --> 0:11:09.960 the universe. Uh. And then this is something we've we've 0:11:09.960 --> 0:11:12.520 touched on the show plenty of times before. Ours is 0:11:12.559 --> 0:11:15.959 the only model of life, but we generally consider technological 0:11:16.040 --> 0:11:18.760 advancement to be a hallmark of intelligent life. And more 0:11:18.800 --> 0:11:21.960 to the point, something we can search for signs of, uh, 0:11:22.080 --> 0:11:25.400 concerning other worlds and other star systems. Uh. You know, 0:11:25.480 --> 0:11:27.880 and anytime you can you can figure out how to 0:11:27.920 --> 0:11:32.160 look for signs of of advanced and expansive energy harvesting 0:11:32.240 --> 0:11:34.760 or consumption. That might be a way for us to 0:11:34.800 --> 0:11:39.360 tell if there's something else out there that is significantly advanced, right, 0:11:39.480 --> 0:11:43.840 and it also might be a simple prerequisite for contact 0:11:44.000 --> 0:11:47.800 because uh, they're talking about so that They started off 0:11:47.840 --> 0:11:50.480 by looking at this as an astrobiology question. You know, 0:11:50.520 --> 0:11:53.400 you're you're looking for signs of life elsewhere in the universe, 0:11:53.720 --> 0:11:56.040 and of course, the the search for intelligent life in 0:11:56.040 --> 0:11:59.079 the universe, in practical terms, what's accessible to us, really 0:11:59.080 --> 0:12:02.920 boils down to the search for life capable of Harvard 0:12:03.040 --> 0:12:06.160 harnessing radio technology within our galaxy. You know, you could 0:12:06.160 --> 0:12:11.319 probably find maybe chemical biosignatures in in the atmospheres of 0:12:11.400 --> 0:12:14.280 exoplanets that would give you an indication that there's some 0:12:14.400 --> 0:12:17.040 kind of life there, maybe bacterial in nature or whatever. 0:12:17.600 --> 0:12:20.120 But if you're looking for intelligent life, you're you're probably 0:12:20.160 --> 0:12:23.559 talking about radio of some kind, right, And so the 0:12:23.640 --> 0:12:28.040 kinds of civilizations that develop radio communication technology would fall 0:12:28.120 --> 0:12:31.800 under the classification of industrial civilizations. And these are what 0:12:31.920 --> 0:12:35.600 author the authors define as civilizations that have the ability 0:12:35.679 --> 0:12:39.600 to harness energy on a global scale. And they bring 0:12:39.640 --> 0:12:42.360 up how this actually feeds into one of the the 0:12:42.440 --> 0:12:47.319 recurring characters in in the astrobiology literature, the Drake equation. 0:12:47.679 --> 0:12:51.040 That's right, Yeah, they bust out the Drake equation, and 0:12:51.240 --> 0:12:53.640 of course consider how how some of the takeaways relate 0:12:53.720 --> 0:12:56.120 to Earth, especially the notion that over the course of 0:12:56.120 --> 0:13:00.920 a planet's existence, multiple industrial civilizations can fear radically arise 0:13:01.000 --> 0:13:04.439 over the span of time that life exists there, And 0:13:04.480 --> 0:13:06.720 then we have to factor in questions over you know, 0:13:06.720 --> 0:13:09.440 how many times life itself may have evolved or started 0:13:09.480 --> 0:13:13.000 out on Earth before our last universal common ancestors got going, 0:13:13.480 --> 0:13:16.080 the possibility of a shadow biosphere, and the idea that 0:13:16.120 --> 0:13:21.559 species like dolphins may suggest independent evolutions of intelligence on Earth. Um, 0:13:21.640 --> 0:13:24.679 you know, so we're left with this idea that, yeah, theoretically, 0:13:26.000 --> 0:13:28.960 given the footprint of life on Earth, you could have 0:13:29.120 --> 0:13:33.640 had multiple intelligences uh evolved and arise during that time period. 0:13:33.679 --> 0:13:37.000 Because that's certainly what the Drake equation UH seems to 0:13:37.040 --> 0:13:40.320 allow for concerning other worlds. Well, yeah, and I you know, 0:13:40.840 --> 0:13:43.240 so I kind of love the Drake equation. You know, 0:13:43.280 --> 0:13:45.839 it's a famous tool that I really enjoy thinking about 0:13:46.040 --> 0:13:50.640 because because it does the job of taking a question 0:13:50.760 --> 0:13:53.640 that seems like we could not possibly answer it. The 0:13:53.720 --> 0:13:57.680 question is how many active technological civilizations are there in 0:13:57.679 --> 0:14:00.640 the Milky Way galaxy? And you know, if you're being 0:14:00.679 --> 0:14:03.360 honest with yourself, the correct answer to that is how 0:14:03.400 --> 0:14:05.560 the hell should I know? Like, there's no way to 0:14:05.600 --> 0:14:09.440 answer that question at all. But what the Drake equation 0:14:09.520 --> 0:14:14.560 does is break that unanswerable question down into a number 0:14:14.600 --> 0:14:18.440 of other questions that you then multiplied together to get 0:14:18.480 --> 0:14:22.960 an estimated number. And many of those smaller questions themselves 0:14:23.160 --> 0:14:25.720 could perhaps be answered, and in fact, some of them 0:14:25.760 --> 0:14:28.840 have been answered since the Drake equation was first formulated. 0:14:29.480 --> 0:14:33.520 Uh So, So it decomposes an unsolvable problem of are 0:14:33.560 --> 0:14:36.120 there aliens out there? And if so, how many, into 0:14:36.160 --> 0:14:38.920 a series of smaller problems, at least some of which 0:14:38.920 --> 0:14:41.160 are solvable, maybe all of which are. You know, you 0:14:41.200 --> 0:14:43.440 could come up with some kind of reasonable guess about. 0:14:44.240 --> 0:14:46.640 And so the classic formulation of the Drake equation is 0:14:46.680 --> 0:14:49.520 to get your number of civilizations in in the Milky way, 0:14:50.080 --> 0:14:52.560 you would multiply a bunch of different terms together. So 0:14:52.720 --> 0:14:55.920 one is the rate of average the average rate of 0:14:55.960 --> 0:14:58.640 star formation. You know, how much do you get stars 0:14:59.200 --> 0:15:03.600 times the fraction of stars that have planets times the 0:15:03.680 --> 0:15:07.720 average number of planets per star times the fraction of 0:15:07.800 --> 0:15:11.960 planets that develop life times the portion of those life 0:15:12.000 --> 0:15:16.080 systems that gain intelligence, times the portion of those intelligent 0:15:16.120 --> 0:15:20.280 life systems that develop technological means to communicate times And 0:15:20.320 --> 0:15:23.600 then here's a really interesting term, quote the length of 0:15:23.720 --> 0:15:28.440 time l over which such civilizations released detectable signals. And 0:15:28.480 --> 0:15:31.080 it's this very last term that I think very often 0:15:31.080 --> 0:15:33.680 gets overlooked by people who are thinking about, you know, 0:15:33.720 --> 0:15:36.280 are there aliens out there, and how could we know? 0:15:37.040 --> 0:15:39.120 I think we often tend to assume that, well, once 0:15:39.200 --> 0:15:42.800 there are aliens with technological means to communicate, that's just 0:15:42.880 --> 0:15:47.040 like a you know, progress only extends from their civilizations 0:15:47.080 --> 0:15:50.040 just continue to get bigger and their capabilities expand, and 0:15:50.080 --> 0:15:52.560 they spread out from there. But I don't know that 0:15:52.760 --> 0:15:56.480 there could be severe limitations on the length of a 0:15:56.920 --> 0:16:01.520 radio receptive or radio broadcasting civilist nation. Maybe they only 0:16:01.560 --> 0:16:03.920 exist for a few hundred years. Because one thing we 0:16:03.960 --> 0:16:09.080 know is that our technological civilization is just a tiny 0:16:09.320 --> 0:16:12.160 blip on the history of planet Earth, even a tiny 0:16:12.200 --> 0:16:15.040 blip on the history of life on planet Earth. Earth 0:16:15.120 --> 0:16:18.240 is four point five billion years old. There's been life 0:16:18.320 --> 0:16:21.200 on Earth for most of that time. Uh. The authors 0:16:21.200 --> 0:16:24.160 here estimate that there has been complex life on Earth's 0:16:24.320 --> 0:16:28.600 land surface for only about four hundred million years, So 0:16:28.640 --> 0:16:31.200 that's only a fraction of the entire history of Earth. 0:16:31.440 --> 0:16:33.360 But that but four hundred million years is still a 0:16:33.360 --> 0:16:36.760 gargantuan amount of time compared to the length of human civilization. 0:16:37.280 --> 0:16:40.640 They say, industrial civilization, you know, by their metric, has 0:16:40.640 --> 0:16:43.600 probably existed for only about three hundred years. This is 0:16:43.760 --> 0:16:48.120 since roughly the beginning of mass production methods for for things. 0:16:48.560 --> 0:16:50.920 And so if humans were wiped out by a global 0:16:50.960 --> 0:16:53.880 mass extinction of some kind in the near future, our 0:16:53.920 --> 0:16:58.600 industrial civilization would just be this tiny little splinter, this 0:16:58.880 --> 0:17:02.480 blip of three hundred years on a history of a 0:17:02.560 --> 0:17:06.520 currently four point five billion year old planet. Yeah, and 0:17:06.600 --> 0:17:09.400 so from there we get into the question, Okay, if 0:17:09.480 --> 0:17:11.840 if you have an industrial civilization like this it is 0:17:11.880 --> 0:17:15.080 just a blip, would we be able to see it? 0:17:15.480 --> 0:17:17.760 And if we could see it, what would we look for? 0:17:17.840 --> 0:17:19.240 And this is you know, this is pretty much the 0:17:19.560 --> 0:17:22.919 meat of the paper here analyzing this sort of question, 0:17:22.960 --> 0:17:25.240 which which is great because it again it gets into 0:17:25.320 --> 0:17:29.240 sort of uh, you know, sci fi friendly concepts. It's 0:17:29.280 --> 0:17:32.680 a useful in considering the evolution of life and the 0:17:32.880 --> 0:17:36.440 existence of intelligent life on other worlds. And it also 0:17:36.520 --> 0:17:40.040 shines a light on what we're doing now and where 0:17:40.040 --> 0:17:43.240 we are and and I think also, uh, you know, 0:17:43.320 --> 0:17:48.480 illustrates nicely illustrates this idea that um that that the 0:17:48.520 --> 0:17:51.919 technology is not just this um that this this this 0:17:52.080 --> 0:17:54.520 ramp to Star Trek, you know, or this ramp to 0:17:54.680 --> 0:17:57.200 the culture or any of our more optimistic sci fi 0:17:57.280 --> 0:18:00.879 dreams like there are there are severe challenges. Uh. And 0:18:00.920 --> 0:18:04.200 of course there's there's always the risk of extinction. That's 0:18:04.200 --> 0:18:07.800 exactly right. And one thing that's funny is we don't 0:18:08.040 --> 0:18:14.119 know whether the rise of technological civilization should generally be 0:18:14.240 --> 0:18:17.760 understood as, on average, a linear process where it just 0:18:17.800 --> 0:18:20.439 sort of goes in one direction and keeps going in 0:18:20.440 --> 0:18:23.439 that direction, or whether it should be understood as, on 0:18:23.560 --> 0:18:26.760 average a cyclical process where you get a rise in 0:18:26.800 --> 0:18:30.159 technological civilization and then it disappears for some reason. You 0:18:30.200 --> 0:18:33.000 can imagine what some of those reasons might be, um, 0:18:33.280 --> 0:18:35.879 and uh, and then maybe rises again out of the 0:18:35.920 --> 0:18:38.639 out of the same biosphere. I mean. Either one I 0:18:38.680 --> 0:18:42.240 think is is a perfectly plausible model to entertain is 0:18:42.440 --> 0:18:46.199 like what usually happens in the universe. Uh. And we 0:18:46.280 --> 0:18:49.040 just don't have the Uh, we don't have the evidence 0:18:49.040 --> 0:18:51.560 to really have an opinion on that. Yeah, I mean 0:18:51.560 --> 0:18:54.320 a lot of it just comes back to the fact 0:18:54.400 --> 0:18:57.480 that again we are the only model of intelligent life 0:18:57.760 --> 0:19:01.560 and certainly technologically advanced tech, um, intelligent life that we 0:19:01.600 --> 0:19:03.840 have to look at. So we have nothing to compare 0:19:03.880 --> 0:19:05.919 us to. Yeah, and we don't know what's going to 0:19:05.960 --> 0:19:10.800 happen to us in the long run, right, So, uh, well, 0:19:10.880 --> 0:19:12.439 let's get into the I guess the sort of the 0:19:12.480 --> 0:19:14.240 first part of the paper. And I do want to 0:19:14.280 --> 0:19:16.800 drive home that if you want to just go right 0:19:16.880 --> 0:19:19.840 to the paper yourself and dive in. Um, you just 0:19:19.880 --> 0:19:22.200 do a search for the title and you can find 0:19:22.200 --> 0:19:25.000 it hosted on NASA. They have a NASA has a 0:19:25.000 --> 0:19:28.760 has a PDF of this that's very easily accessible. Uh. 0:19:28.800 --> 0:19:30.720 You can also read it in full on the Cambridge 0:19:30.760 --> 0:19:33.320 University Press website, which I think is the press behind 0:19:33.400 --> 0:19:37.200 the journal, the International Journal Journal of Vester Biology. And yeah, 0:19:37.320 --> 0:19:39.720 so it's all on their end with the references hyperlinked 0:19:39.720 --> 0:19:42.119 and all that, which is nice. Yes, yeah, absolutely so 0:19:42.160 --> 0:19:44.080 if you hit a paywall, don't don't give up. It's 0:19:44.080 --> 0:19:47.080 out there. Um. And I believe Adam Frank also wrote 0:19:47.119 --> 0:19:50.159 a piece for What the Atlantic where he nicely summarizes 0:19:50.200 --> 0:19:52.160 some of the ideas here. Oh yeah, and he also 0:19:52.160 --> 0:19:54.880 tells a funny story about how they arrived at writing 0:19:54.920 --> 0:19:57.840 the paper because I think he says, uh, he showed 0:19:57.920 --> 0:20:01.800 up in Gevin Schmidt's office to talk about UM, to 0:20:01.880 --> 0:20:05.560 talk more about astrobiology, like Drake equation type questions, and 0:20:05.600 --> 0:20:07.920 he's like, okay, so we we we know we've got 0:20:07.960 --> 0:20:13.080 one industrial civilization on Earth. And then Schmidt responded by saying, 0:20:13.080 --> 0:20:15.840 how do we know we're the only one? I think 0:20:16.040 --> 0:20:18.520 just hitting that early like wall, They're like wow, And 0:20:18.600 --> 0:20:21.200 then that turned into the paper, Yeah, and it's it's 0:20:21.280 --> 0:20:29.399 it's quite a paper. Thank So let's see, let's get 0:20:29.400 --> 0:20:31.000 into the first part of it, which I think you 0:20:31.000 --> 0:20:32.840 can loosely think of it's just sort of a look 0:20:32.840 --> 0:20:35.640 at the limits of our vision. So they point out 0:20:35.680 --> 0:20:39.359 that for the last two point five million years, uh, 0:20:39.440 --> 0:20:44.800 there's widespread physical evidence of things like climate change, soil horizons, 0:20:44.880 --> 0:20:48.280 this is where one layer of soil differs from Belower above, 0:20:48.400 --> 0:20:52.480 speaking to changes recorded in the soil, as well as 0:20:52.560 --> 0:20:58.439 archaeological evidence of non Homo sapiens cultures such as the Neanderthals. 0:20:59.000 --> 0:21:01.480 And this two point five million year period is known 0:21:01.560 --> 0:21:05.080 as the Quaternary. Now, going back before the Quaternary again 0:21:05.760 --> 0:21:08.320 more than two point five million years ago, the land 0:21:08.359 --> 0:21:10.879 evidence is harder to come by. You have to depend 0:21:10.920 --> 0:21:15.399 on drilling, mining, and occasional exposed sections of the earth. 0:21:15.920 --> 0:21:19.040 Even in the ocean sentiment evidence apparently only goes back 0:21:19.080 --> 0:21:22.560 to around one seventy million years ago. Yeah, And I 0:21:22.600 --> 0:21:24.720 think for me this was actually one of the most 0:21:24.800 --> 0:21:28.399 interesting parts of the paper because I would say, if 0:21:28.440 --> 0:21:32.119 you just go by standard intuition, a person might think, uh, 0:21:32.160 --> 0:21:36.480 you know, if there had been a civilization on Earth, 0:21:36.720 --> 0:21:39.840 you know, a two million years ago or something like that. Uh, 0:21:40.000 --> 0:21:42.720 would wouldn't that just be completely obvious, Like we'd see 0:21:42.720 --> 0:21:45.240 evidence of it all around us. Would there be ruins 0:21:45.280 --> 0:21:47.640 and all that, you know, their their stone hinges, their 0:21:47.640 --> 0:21:52.640 skyscrapers and everything like that. Actually it's not. It might 0:21:52.680 --> 0:21:55.040 not be as obvious as you might think. In fact, 0:21:55.359 --> 0:21:58.600 the evidence of it could be rather scarce. And this 0:21:58.680 --> 0:22:02.520 runs counter to our side five imaginings, right, because when 0:22:02.560 --> 0:22:06.240 you encounter elder civilizations and in other works like there's 0:22:06.320 --> 0:22:08.840 usually some sort of a ruin or a vault or 0:22:08.880 --> 0:22:12.280 some sort of mysterious monolith or something like the idea 0:22:12.680 --> 0:22:16.320 that the elders would just be gone entirely, like just erased, 0:22:16.600 --> 0:22:19.359 not by some sort of a conspiracy or by some 0:22:19.440 --> 0:22:22.399 sort of a you know, alien shenanigans. But just because 0:22:22.480 --> 0:22:25.439 things don't last that long, that's a it's an alien 0:22:25.480 --> 0:22:28.080 concept from too many of our again, too many of 0:22:28.119 --> 0:22:30.720 our creative visions of of what the future in the past, 0:22:30.800 --> 0:22:33.359 maybe exactly so we think, well, you know, there are 0:22:33.440 --> 0:22:36.360 ruins of civilizations from thousands of years ago, but that's 0:22:36.400 --> 0:22:40.000 thousands of years ago. That's nothing in geological time. The 0:22:40.119 --> 0:22:42.240 surface of the I mean, look a look at what 0:22:42.359 --> 0:22:46.040 a map of the land formations on Earth just you know, 0:22:46.400 --> 0:22:49.239 sixty million years ago looked like it's like, you know, 0:22:49.359 --> 0:22:52.800