WEBVTT - Where do comets come from? 0:00:08.440 --> 0:00:12.640 Hey, Jorgey, what's your favorite Solar System object? I'm gonna 0:00:12.680 --> 0:00:14.960 have to go with the Earth because you know, it's 0:00:14.960 --> 0:00:17.360 the only one I've been to, so you're not a 0:00:17.440 --> 0:00:20.520 gas giant kind of person. Depends how many tacas I 0:00:20.560 --> 0:00:22.599 had for munch. But what if I do? You do 0:00:22.640 --> 0:00:24.480 you have a favorite? I'm a big fan of the 0:00:24.520 --> 0:00:27.280 Sun and everything it does for us here on Earth, 0:00:27.440 --> 0:00:31.040 But my favorite thing in the Solar System is actually comets. 0:00:31.160 --> 0:00:34.239 Comments what have commets done for us? Well, they're like 0:00:34.400 --> 0:00:38.480 cosmic snowballs, and actually most of Earth's water turns out 0:00:38.479 --> 0:00:41.960 to be melted comets. I guess water is pretty useful 0:00:42.080 --> 0:00:44.479 to have. But wait, are you saying the Solar System 0:00:44.520 --> 0:00:48.280 is having a snowball fight. Yeah, it's more like deadly 0:00:48.520 --> 0:01:07.640 planetary dodgeball. Hi am more Hammon, cartoonists and the creator 0:01:07.720 --> 0:01:11.400 of PhD Comics. Hi. I'm Daniel. I'm a particle physicist, 0:01:11.440 --> 0:01:15.120 but I have strong opinions about various Solar System objects. 0:01:15.120 --> 0:01:18.160 And Welcome to our podcast, Daniel and Jorge Explain the Universe, 0:01:18.240 --> 0:01:20.479 a production of I Heart Radio in which we talk 0:01:20.520 --> 0:01:23.160 about everything that we know about the universe and everything 0:01:23.160 --> 0:01:25.559 that we don't know about the universe, everything that makes 0:01:25.640 --> 0:01:28.759 us wonder and everything that makes us go huh. And 0:01:28.800 --> 0:01:31.480 we explain all of it to you because we think 0:01:31.520 --> 0:01:35.200 that your curiosity is as valuable as the curiosity of 0:01:35.240 --> 0:01:38.120 scientists working on the front line. Yeah, and there's a 0:01:38.120 --> 0:01:41.040 lot to be curious about. The universe is full of 0:01:41.080 --> 0:01:44.680 amazing and incredible things and a lot of mysteries, a 0:01:44.680 --> 0:01:48.240 lot of things that we don't know where they come from, 0:01:48.320 --> 0:01:51.800 or what makes them what they are, or why they're there. Yeah, 0:01:51.840 --> 0:01:55.200 And a lot of great scientific discoveries begin with pretty 0:01:55.240 --> 0:01:58.280 simple questions, you know, like why is that thing there? 0:01:58.680 --> 0:02:01.040 Or why are those common? It's flying through space and 0:02:01.040 --> 0:02:03.120 where do they come from? Is one of them going 0:02:03.160 --> 0:02:06.480 to hit us and wipe us out? Great scientific discoveries 0:02:06.560 --> 0:02:09.640 come from really simple questions that everybody wants to know 0:02:09.720 --> 0:02:12.280 the answers to. Yeah, because we have questions even about 0:02:12.280 --> 0:02:16.679 our own backyard. Our solar system is still full of 0:02:16.720 --> 0:02:20.560 things that we don't quite fully understand. People like to 0:02:20.600 --> 0:02:23.120 talk about things in the distant universe that are still 0:02:23.160 --> 0:02:25.000 a mystery. We don't know how big it is or 0:02:25.040 --> 0:02:27.720 what's going on out there in the depths of the universe. 0:02:28.080 --> 0:02:30.600 But you're absolutely right, there's still a lot to be 0:02:30.680 --> 0:02:34.919 discovered right in our own neighborhood, big questions about what's 0:02:34.919 --> 0:02:38.120 going on in our own household that we still don't 0:02:38.160 --> 0:02:39.840 know the answers to. So they know you have a 0:02:39.960 --> 0:02:42.760 strong opinions about things in our Solar System? Are they 0:02:42.800 --> 0:02:45.840 all positive or are some of them negative? Is there 0:02:45.840 --> 0:02:49.440 someone you don't like here in system? Now? They're all positive. 0:02:49.480 --> 0:02:52.799 I love everything in the Solar System, from ice giants 0:02:52.840 --> 0:02:57.720 to planetism als, to space centaurs, to deadly comments to 0:02:57.880 --> 0:03:00.919 enormous burning balls of gas. I just think it's all 0:03:01.000 --> 0:03:04.560 pretty awesome. I can't imagine having a negative opinion about anything. 0:03:04.960 --> 0:03:09.679 Do you include in that all the people on Earth too? Yes? 0:03:09.919 --> 0:03:12.880 I love everybody. No, it's incredible when you look out 0:03:12.880 --> 0:03:16.280 there in space that you see so many beautiful, amazing things. 0:03:16.280 --> 0:03:18.040 Like when was the last time you looked at something 0:03:18.080 --> 0:03:20.040 out in space and you thought that's just kind of 0:03:21.000 --> 0:03:23.480 you know, it's all just sort of like incredible and beautiful. 0:03:23.560 --> 0:03:26.919 You know, whoever the universe's visual artist is, they're doing 0:03:26.919 --> 0:03:29.440 a good job. Although you know, we live in California, 0:03:29.480 --> 0:03:31.200 so right now, when I look up at the sky, 0:03:31.600 --> 0:03:34.080 it's mostly smoke. Well, then take a journey through the 0:03:34.080 --> 0:03:36.120 Solar System with your mind's eye. Yeah, there are a 0:03:36.160 --> 0:03:38.800 lot of big questions about the Solar System and how 0:03:38.840 --> 0:03:40.560 we got to where we are. And one of those 0:03:40.680 --> 0:03:44.640 big questions about our Solar system is where do comets 0:03:44.760 --> 0:03:48.080 come from? We don't know a comet factory here in 0:03:48.080 --> 0:03:49.920 our Solar system, do we We don't know of a 0:03:50.080 --> 0:03:52.720 comet factory. It could be that there are aliens out 0:03:52.720 --> 0:03:55.160 there in the outskirts of the Solar System packing up 0:03:55.200 --> 0:03:58.800 ice balls and shooting them at Earth. Or it could 0:03:58.800 --> 0:04:01.720 be that they come from something else, something deep out 0:04:01.720 --> 0:04:05.080 there in the Solar System. That's basically a huge reservoir 0:04:05.120 --> 0:04:08.800 of comets ready to fall in, screaming towards the Sun 0:04:09.040 --> 0:04:11.880 and boiling. And this is a big question because some 0:04:11.920 --> 0:04:14.560 people think that most of the water on Earth came 0:04:14.680 --> 0:04:18.320 from comets. That's right, Commets are mostly ice. You know, 0:04:18.400 --> 0:04:21.200 something a lot of people don't understand about the universe 0:04:21.600 --> 0:04:24.960 is that water is not rare. We talk about liquid 0:04:25.000 --> 0:04:27.200 water being something we're looking for in the surface of 0:04:27.240 --> 0:04:30.080 planets to see if there's alien life, but water as 0:04:30.080 --> 0:04:32.560 a chemical, there's tons of it out there. There's like 0:04:32.680 --> 0:04:37.039 planet size blobs of it. So most comets are icy 0:04:37.120 --> 0:04:40.360 planetism alls. They're just big balls of ice, and some 0:04:40.440 --> 0:04:43.200 of them fell towards the Earth in the early days 0:04:43.600 --> 0:04:47.600 and landed and melted and formed our oceans. Thank goodness, 0:04:47.600 --> 0:04:50.440 because that's where life came from. Right, we had them 0:04:50.440 --> 0:04:53.040 in for those snowballs, and we wouldn't be here, that's right. 0:04:53.279 --> 0:04:55.640 So next time you put your lips to a glass 0:04:55.680 --> 0:05:00.000 of melted comet, remember you're drinking. The outer Solar System 0:05:00.000 --> 0:05:04.320 are melted common Right, next time you go somewhere in 0:05:04.400 --> 0:05:06.960 order a drink, order sparkling melted comment and see what 0:05:07.000 --> 0:05:08.960 they do. Yeah, So a big question is where they 0:05:09.000 --> 0:05:12.479 come from, and so scientists have a potential answer to 0:05:12.560 --> 0:05:15.320 that question, right, Daniel, that's right. They don't know for sure. 0:05:15.440 --> 0:05:18.720 Nobody's ever actually seen it, but we've given it a name. 0:05:18.800 --> 0:05:21.160 So today on the podcast, we will be asking the question, 0:05:25.680 --> 0:05:28.919 what is now Daniel? Is that pronounced or or or 0:05:29.080 --> 0:05:32.679 because it's spelled O r T. It's a great question, 0:05:33.080 --> 0:05:35.719 and it's a Dutch name. It comes from a Dutch 0:05:35.720 --> 0:05:38.760 astronomer who first thought it up. And so I reached 0:05:38.760 --> 0:05:42.360 out to my Dutch speaking brother to ask him for 0:05:42.440 --> 0:05:45.200 his preferred pronunciation because I didn't know is it ort 0:05:45.440 --> 0:05:48.320 ort ort or something like weird Dutch vowel that we 0:05:48.320 --> 0:05:51.080 don't even have in English that can never be replicated? 0:05:51.120 --> 0:05:54.080 Keep going, keep going? Well, you know there are vowels 0:05:54.080 --> 0:05:56.440 in Danish that you know you can only replicate. You 0:05:56.480 --> 0:05:58.880 get like punched in the gut in exactly the right way, 0:05:59.000 --> 0:06:03.599 like you Dango speakers out there know what I'm talking about. 0:06:04.160 --> 0:06:06.720 But it turns out that or its spelled o o 0:06:07.040 --> 0:06:11.240 rt is pronounced like port. All right, So it's a 0:06:11.320 --> 0:06:13.880 cloud apparently of some sort, and it's I'm guessing it's 0:06:13.920 --> 0:06:16.200 out in space, and so the big question is how 0:06:16.200 --> 0:06:18.359 many people out there know what it is and what 0:06:18.480 --> 0:06:22.880 its significance is. That's right? So I pulled our listeners 0:06:22.880 --> 0:06:26.600 who have volunteered to answer random questions over the Internet 0:06:26.680 --> 0:06:29.839 from a businessist they've never met. If you'd like to 0:06:29.839 --> 0:06:34.160 participate in such absurd commentary on our physical universe, please 0:06:34.240 --> 0:06:37.480 write to me two questions at Daniel and Jorge dot com. 0:06:37.600 --> 0:06:40.680 And thanks to everybody who shared your speculations. Think about 0:06:40.720 --> 0:06:42.599 it for a second. If someone asked you what the 0:06:42.720 --> 0:06:46.720 orc cloud is, what would you answer. Here's what people 0:06:46.760 --> 0:06:50.320 had to say, The or Cloud is one of the 0:06:50.400 --> 0:06:55.760 outermost regions of the Solar System, comprised of we think 0:06:55.760 --> 0:06:58.960 a bunch of remnants of the early Solar system. The 0:06:59.200 --> 0:07:04.880 Orc Cloud is a group of like dust and rocks 0:07:05.200 --> 0:07:11.440 and asteroids and just material that's way outside are encircles 0:07:11.680 --> 0:07:15.880 our whole Solar system. I think in a giant sphere, 0:07:16.160 --> 0:07:20.040 or maybe just a circle. The art Cloud is a 0:07:20.160 --> 0:07:25.640 vast array of comets and other such I see debris 0:07:26.000 --> 0:07:28.920 forwarding around the Sun, very far away from the rest 0:07:28.920 --> 0:07:33.240 of the planetary systems. I know that the Sun, it's 0:07:33.240 --> 0:07:38.000 the middle of it, and it passes our solar systems, 0:07:38.000 --> 0:07:41.040 so passes Pluto. Is it the big cloud of dust 0:07:41.160 --> 0:07:43.160 that I'm spewing out the top and the bottom of 0:07:43.200 --> 0:07:45.960 the Milky Way? I have anything to do with equippable? 0:07:46.640 --> 0:07:49.800 Probably close to the Solar system. I think the art 0:07:49.840 --> 0:07:53.480 Cloud is like an area outside the Solar system where 0:07:53.480 --> 0:07:58.280 there are some icy objects. I'm not sure what, probably 0:07:59.200 --> 0:08:02.440 comets and things like that. All right, some pretty good answers. 0:08:02.520 --> 0:08:05.240 Most people seem to know it's something related to our 0:08:05.280 --> 0:08:08.320 Solar system, and that it's a cloud, and that maybe 0:08:08.360 --> 0:08:12.320 there's ice involved. Yeah, exactly, it's something big and fuzzy 0:08:12.360 --> 0:08:16.080 and out there and cool. Cool. And my favorite thing 0:08:16.080 --> 0:08:18.160 about the Orc cloud is at the acronym the O 0:08:18.400 --> 0:08:23.000 C is the same as the place I live, Orange County, 0:08:23.600 --> 0:08:26.440 except it's a little warmer, I think, a little warmer, 0:08:26.600 --> 0:08:29.760 but it's also still very very cool. That's the first 0:08:29.760 --> 0:08:32.880 time I've heard you give a compliment to the Orange 0:08:32.880 --> 0:08:36.720 County there. I love Orange County. Best place in the 0:08:36.760 --> 0:08:39.800 world to live. Seriously, what could you complain about? But 0:08:39.960 --> 0:08:42.319 that's not the topic of today's podcast. We're talking about 0:08:42.360 --> 0:08:46.160 the cosmic o C, the solar systems O C, not 0:08:46.240 --> 0:08:49.400 calibornias o C and to uh, it's apparently something out 0:08:49.400 --> 0:08:51.920 in space and so Daniel, let's step people through it. 0:08:52.240 --> 0:08:54.760 So what is the orc Cloud? The orc cloud is 0:08:54.800 --> 0:09:01.000 super awesome. It is a theoretical cloud of icy planetisml's 0:09:01.280 --> 0:09:04.480 or many planets planetismal. Did you just make that up 0:09:04.559 --> 0:09:07.040 or is that the actual science terms? Oh? Man, I 0:09:07.080 --> 0:09:08.840 wish I could have made that word of there's something 0:09:08.960 --> 0:09:13.120 wonderful about just saying that word planetismal. Right, but no, 0:09:13.240 --> 0:09:16.400 planetismal is a mini planet and it's smaller than a 0:09:16.520 --> 0:09:19.160 dwarf planet. Right, You've got planet dwarf planet, and then 0:09:19.280 --> 0:09:23.480 planet Tismal. They couldn't just say mini planet. Well it's 0:09:23.480 --> 0:09:25.920 sort of like Planetino, you know, that's what you do 0:09:25.960 --> 0:09:28.800 with English planet Tito. And so it's a bunch of 0:09:28.840 --> 0:09:33.240 these and they're really really far out there. Like if 0:09:33.240 --> 0:09:35.240 you have the Solar system, you know, the Earth is 0:09:35.240 --> 0:09:38.800 at one AU call an astronomical unit, and you go 0:09:38.960 --> 0:09:41.480 really far out you get out to like Neptune and Pluto. 0:09:42.040 --> 0:09:45.240 You have to go much, much, much further before you 0:09:45.240 --> 0:09:48.280 get to the arch cloud. Is it even considered our 0:09:48.320 --> 0:09:51.360 Solar system or is it technically outside of our Solar system? Yeah, 0:09:51.360 --> 0:09:54.560 it's a great question. Most people consider the end of 0:09:54.559 --> 0:09:57.800 our Solar system to be just under about a hundred 0:09:57.880 --> 0:10:02.120 a U, where the sun radiation becomes dominated by the 0:10:02.160 --> 0:10:04.960 galactic radiation. How you think of space is sort of 0:10:05.000 --> 0:10:08.559 like empty, right, but actually it's filled with streaming particles. 0:10:08.559 --> 0:10:11.600 The Sun is pumping out particles, not just photons, but 0:10:11.679 --> 0:10:14.680 protons and electrons and all sorts of crazy stuff, and 0:10:14.760 --> 0:10:17.079 it dominates the region around it with all of its 0:10:17.080 --> 0:10:20.760 pulsating radiation. But the rest of the galaxy also has 0:10:20.760 --> 0:10:23.599 a wind that's coming from all the other stars in 0:10:23.640 --> 0:10:26.280 the central black hole. And all that crazy stuff. So 0:10:26.320 --> 0:10:28.960 we define the edge of the Solar system it's called 0:10:28.960 --> 0:10:32.839 the helio pause, as the place where the Sun's radiation 0:10:33.320 --> 0:10:36.440 stops dominating the local environment and you're taken over by 0:10:36.440 --> 0:10:39.960 the galactic wind. And that's like a hundred or so A. 0:10:40.440 --> 0:10:42.840 It's like when our Sun becomes just another star kind 0:10:42.840 --> 0:10:45.760 of yeah, exactly, and the wind from the rest of 0:10:45.760 --> 0:10:49.280 the galaxy takes over the Sun's wind. And here again 0:10:49.400 --> 0:10:51.719 wind we don't mean air, We just mean the particles 0:10:51.720 --> 0:10:54.520 that it's shooting out. But the rac cloud starts like 0:10:54.640 --> 0:10:58.760 ten times further out than that, like at a thousand 0:10:58.960 --> 0:11:02.520 a U. Now it's just still sort of like bound 0:11:02.559 --> 0:11:04.920 by the gravity of the Sun, or is it pretty 0:11:05.000 --> 0:11:08.520 much like an independent thing from our solar system. It's 0:11:08.520 --> 0:11:11.120 definitely bound by the gravity of the Sun. So if 0:11:11.120 --> 0:11:13.920 you define the edge of the Solar system by the radiation, 0:11:14.200 --> 0:11:17.040 it's like a hundred a U. But stuff that's further 0:11:17.120 --> 0:11:20.319 out is still gravitationally bound to the Sun, but it's 0:11:20.360 --> 0:11:23.280 a little bit loose. It's like a little fuzzy. It's 0:11:23.360 --> 0:11:25.880 so far out from the Sun that it's not that 0:11:26.040 --> 0:11:29.240 hard to knock something off and have an escape into 0:11:29.240 --> 0:11:33.960 interstellar space, so it's not orbiting around us. It's sort 0:11:33.960 --> 0:11:36.439 of like we're tugging them and it's tugging us. It's 0:11:36.480 --> 0:11:39.040 definitely orbiting around us. Think of it like a huge 0:11:39.320 --> 0:11:42.600 shell surrounding the Solar System. The other fascinating thing about 0:11:42.640 --> 0:11:45.120 it is that it's not a disk, right, Most of 0:11:45.160 --> 0:11:47.400 the stuff in the Solar System is a big disc, 0:11:47.480 --> 0:11:50.360 it's flat. But the Orc Cloud, we think, is a sphere. 0:11:50.440 --> 0:11:53.480 It's like totally surrounding the Solar System, and it goes 0:11:53.520 --> 0:11:56.040 out really really far out to like a light year 0:11:56.120 --> 0:11:59.800 maybe two light years of just this like cloud of 0:12:00.040 --> 0:12:03.520 little frozen objects, and there could be like trillions of 0:12:03.559 --> 0:12:08.040 the planetismal, trillions of planetism many planets I'm sorry, yeah, 0:12:08.200 --> 0:12:10.600 planet titos. And it's sort of like calculus. You know, 0:12:10.600 --> 0:12:13.520 in calculus, you sum over infinitismals and you get like 0:12:13.520 --> 0:12:16.160 an actual quantity. In the same way, if you sum 0:12:16.200 --> 0:12:19.439 over all the planetism als in the ord cloud, you 0:12:19.520 --> 0:12:22.319 get a combined mass of stuff that's like five times 0:12:22.400 --> 0:12:25.280 the mass of the Earth, but then again spread out 0:12:25.320 --> 0:12:27.920 into like trillions of objects. It spread out not just 0:12:28.000 --> 0:12:31.120 like wide but tall to like it's it's pretty diffuse 0:12:31.280 --> 0:12:34.360 it's very diffuse, Like it's not like flying the millennium 0:12:34.400 --> 0:12:36.840 falcon through an asteroid field. You gonna like dodge and 0:12:36.880 --> 0:12:39.880 weave right, it's like, could we see something, like is 0:12:39.920 --> 0:12:43.720 there one there? It's so far out there, it's mostly empty. 0:12:43.920 --> 0:12:46.600 But again, they are gravitationally bound to the Sun and 0:12:46.640 --> 0:12:48.640 they are orbiting the Sun. That's why they are in 0:12:48.679 --> 0:12:51.480 a cloud around the Sun. It's not like just the 0:12:51.520 --> 0:12:54.160 whole interstellar medium is filled with these objects. It's a 0:12:54.200 --> 0:12:56.680 cloud of them. We think. Again, we think we don't 0:12:56.679 --> 0:12:58.840 know for sure. We haven't seen them because they're so 0:12:58.880 --> 0:13:01.960 small and far away, but we think that they're there 0:13:02.200 --> 0:13:04.319 in this big blob around the size see, and it's 0:13:04.360 --> 0:13:07.520 made up of like giant literally like giant balls of ice, 0:13:07.800 --> 0:13:11.280 basically snowballs. How big, Well, each one could be like 0:13:11.360 --> 0:13:14.120 bigger than a kilometer in size, So we think that 0:13:14.200 --> 0:13:16.200 they're like trillions of them that are more than a 0:13:16.240 --> 0:13:20.080 kilometer and maybe only billions that are twenty kilometers are larger. 0:13:20.480 --> 0:13:23.040 But if you wanted to have a cosmic snowball fight, 0:13:23.120 --> 0:13:25.640 that's like where your arsenal is, that's the best place 0:13:25.679 --> 0:13:28.200 to go for the stockpile. Wow, So that's like, let 0:13:28.200 --> 0:13:30.679 me see, that's like a snowball about the size of 0:13:30.920 --> 0:13:35.520 Los Angeles right kilometers. Yeah, there are billions of frozen 0:13:35.559 --> 0:13:39.640 Los Angeles is out there in the o C because 0:13:39.679 --> 0:13:42.959 they are pretty cool, icy cool. They are pretty cool, 0:13:43.320 --> 0:13:45.800 and if they weren't gravitationally bound to the Sun, they 0:13:45.800 --> 0:13:49.120 would just sort of float away into space. But they 0:13:49.160 --> 0:13:51.800 are bound there. They're floating around, but you know, it's 0:13:51.840 --> 0:13:55.720 sort of loose, and so sometimes the thought is sometimes 0:13:55.800 --> 0:13:58.839 something perturbs them and then they can get knocked out 0:13:58.840 --> 0:14:01.520 of their very loose orbit and plummet towards the inner 0:14:01.520 --> 0:14:04.120 Solar System because they're in a stable orbit. Is that 0:14:04.160 --> 0:14:07.160 the idea is that they're like happily going around our 0:14:07.200 --> 0:14:11.640 Sun in this huge, wide orbit, but sometimes they can 0:14:11.720 --> 0:14:14.160 fall in. Yeah, we think it's probably stable and if 0:14:14.200 --> 0:14:17.040 nothing perturbed them, they would just happily hang out there 0:14:17.080 --> 0:14:21.040 really far away, staying frozen. But you know, we are 0:14:21.160 --> 0:14:24.320 in a little neighborhood, and since it's sort of loosely 0:14:24.400 --> 0:14:27.240 held by the Sun, it's not that hard to perturb them. 0:14:27.440 --> 0:14:31.280 And you can have things like galactic tides that squeeze 0:14:31.320 --> 0:14:33.440 the orac cloud and knock some of them out of orbit. 0:14:33.960 --> 0:14:35.880 You mean from the center of the galaxy. Yeah, just 0:14:35.920 --> 0:14:38.760 the way the Moon has a gravitational effect on the 0:14:38.800 --> 0:14:41.040 water of the Earth. So as the Moon goes around 0:14:41.080 --> 0:14:43.640 the Earth, it tugs on the oceans and causes tides. 0:14:44.040 --> 0:14:46.880 We have a gravitational pull towards the center of the galaxy, 0:14:47.240 --> 0:14:49.240 and that tends to tug on one part of the 0:14:49.320 --> 0:14:52.040 Orc Cloud that's closer to it more than the rest 0:14:52.040 --> 0:14:54.360 of the Orc clouds, so sort of extends it. And 0:14:54.360 --> 0:14:57.240 then as we move around the center of the galaxy 0:14:57.360 --> 0:15:00.520 very slowly, you know, hundreds of millions of years, the 0:15:00.560 --> 0:15:04.160 direction of that tug changes, so it's a dynamic. So 0:15:04.200 --> 0:15:06.160 as we move around the center of the galaxy, the 0:15:06.200 --> 0:15:09.280 tides change, the galactic tides change. So are we right 0:15:09.320 --> 0:15:17.800 now and high tide or lord tide. Well, we're at 0:15:17.840 --> 0:15:20.080 the center of it right so we wouldn't feel it 0:15:20.080 --> 0:15:22.160 at all. But there's a blob of the Orc cloud 0:15:22.200 --> 0:15:25.320 that's always pointed towards the center of the galaxy that 0:15:25.360 --> 0:15:27.720 would be at high tide. There's more objects in that 0:15:27.880 --> 0:15:30.240 part of it, so we're sort of at the very 0:15:30.240 --> 0:15:33.040 center of it, so we can't tell, but it can 0:15:33.120 --> 0:15:36.320 be galactic tides. It can also be like nearby stars. 0:15:36.760 --> 0:15:39.720 If a nearby star happens to come somewhere close to 0:15:39.840 --> 0:15:42.440 us as we all swish around the Milky Way, it 0:15:42.480 --> 0:15:45.640 can perturb the orc cloud and send comets falling in 0:15:45.680 --> 0:15:47.960 towards the center of the Solar system, right or steal them, 0:15:48.400 --> 0:15:51.960 possibly steal them, or steal them absolutely, and we'll talk 0:15:51.960 --> 0:15:53.960 about where these came from. It's not clear that all 0:15:53.960 --> 0:15:57.720 of them actually came from our Solar system. And I 0:15:57.720 --> 0:16:00.880 guess the thing is that we've never actually seen the cloud, right, Like, 0:16:00.920 --> 0:16:03.320 we don't have pictures of it or even like radar 0:16:03.360 --> 0:16:05.960 of it or evidence of it. That's right. It's so 0:16:06.080 --> 0:16:08.880 far out there that it's still theoretical. There have been 0:16:08.960 --> 0:16:11.720 some glimpses of one or two objects that people debate 0:16:12.040 --> 0:16:15.520 might be like part of the Inner Inner Inner or cloud. 0:16:15.840 --> 0:16:19.280 But these things are really small and really really far away, 0:16:19.320 --> 0:16:22.560 Like it's hard to see Pluto, right, and Pluto is 0:16:22.640 --> 0:16:26.240 really close compared to these things, and nothing that we 0:16:26.360 --> 0:16:29.120 have out there in the Solar System has gotten anywhere 0:16:29.160 --> 0:16:31.400 close to them, Like the thing that we have sent 0:16:31.600 --> 0:16:34.760 out into space, that's the furthest object the humans have 0:16:34.920 --> 0:16:39.680 ever built, that's Voyager one. The fastest human spaceship ever. Right, 0:16:40.200 --> 0:16:42.160 that thing won't get to the beginning of the Orc 0:16:42.200 --> 0:16:46.160 Cloud for another three hundred years. Well, Daniel, I don't 0:16:46.160 --> 0:16:49.280 know if I believe in this thing or not, but 0:16:49.360 --> 0:16:51.800 let's get into how we know it's actually there and 0:16:52.080 --> 0:16:55.760 why we think it's important for our origin as a 0:16:55.960 --> 0:16:59.000 planet and as a human species. But first, let's take 0:16:59.000 --> 0:17:14.440 a quick break. All right, we're talking about the or Cloud, 0:17:14.880 --> 0:17:17.720 which is uh. I guess Daniel, you would describe it 0:17:17.760 --> 0:17:22.879 as like a giant shell of city size snowballs floating 0:17:22.920 --> 0:17:26.800 out hundreds of light years away from the Sun. That's right, 0:17:27.000 --> 0:17:30.359 And snowballs makes it sound quaint and fun and like 0:17:30.520 --> 0:17:32.199 if you get hit by one, you can just go 0:17:32.320 --> 0:17:34.800 inside and warm up with a cup of hot cocoa. Right, 0:17:35.119 --> 0:17:38.160 But these things are massive ice balls, and if one 0:17:38.160 --> 0:17:40.920 of them hit the Earth, we might be toasted. So 0:17:40.960 --> 0:17:43.320 we'll talk about the danger these things later on, but 0:17:43.480 --> 0:17:45.440 I want to make sure people are aware that these 0:17:45.440 --> 0:17:48.920 are basically massive space bullets waiting to hit the Earth. 0:17:48.960 --> 0:17:50.800 It's like a real snowball. If they pack enough ice 0:17:50.840 --> 0:17:53.160 into that slush ball, it can really hurt. Yeah, alright, 0:17:53.200 --> 0:17:55.240 so how do we know that it's actually there. Then 0:17:55.280 --> 0:17:57.560 what makes us think that there is this giant cloud 0:17:57.600 --> 0:18:00.520 of snowballs in space? Well, it comes um sort of 0:18:00.520 --> 0:18:03.320 a paradox. In the last hundred years, we've established that 0:18:03.359 --> 0:18:06.240 there are lots of comets, but the Solar system is 0:18:06.280 --> 0:18:08.840 not very young, and so people have been wondering, like, 0:18:08.960 --> 0:18:12.000 where do all these comets come from? Because comets are 0:18:12.000 --> 0:18:15.120 not stable. Like, once a comet starts falling in towards 0:18:15.119 --> 0:18:17.760 the Sun, it loses a lot of its mass as 0:18:17.760 --> 0:18:20.719 the Sun boils it away. So a comet can't like 0:18:21.080 --> 0:18:24.000 zip around the Sun for billions of years. It only 0:18:24.040 --> 0:18:26.880 gets like, you know, fifty or a hundred, maybe two 0:18:27.000 --> 0:18:30.320 hundred times around before it gets boiled away. Right, So 0:18:30.720 --> 0:18:33.040 if that's the case, if comets don't last very long, 0:18:33.280 --> 0:18:36.399 why are we still seeing commets? Like you lived in Arizona, 0:18:36.480 --> 0:18:38.360 and every once in a while somebody throws a snowball 0:18:38.400 --> 0:18:41.040 at your house, You're like, this is recent, Like somebody 0:18:41.119 --> 0:18:44.080 just made this. Yeah, Or you know, if you're walking 0:18:44.080 --> 0:18:46.399 around your neighborhood and everybody's eating ice cream, you're like, 0:18:46.520 --> 0:18:48.600 where's the ice cream? Chuck? It must have just come by. 0:18:49.240 --> 0:18:51.600 And so exactly, they thought there must be some sort 0:18:51.600 --> 0:18:55.120 of source of these things. The other clue was that 0:18:55.160 --> 0:18:58.480 there's sort of two types of comets. There are short 0:18:58.520 --> 0:19:01.240 period comets. Com is to have an orbit around the 0:19:01.240 --> 0:19:04.200 Sun that's like less than ten a U, and these 0:19:04.200 --> 0:19:06.439 are mostly aligned with the Solar System. It seems like 0:19:06.440 --> 0:19:09.600 they're like basically Solar System objects, just blobs of ice 0:19:09.960 --> 0:19:12.399 somewhere in the outer reaches of the Solar System. But 0:19:12.480 --> 0:19:14.920 then there's a second group of commets. They're called long 0:19:15.119 --> 0:19:18.040 period comets. These are ones that have an orbit that's 0:19:18.080 --> 0:19:21.000 like a thousand a U or more, and they take 0:19:21.040 --> 0:19:23.480 a long time to go around the Sun, and they 0:19:23.600 --> 0:19:26.800 don't follow the plane of the Solar system. So these 0:19:26.840 --> 0:19:28.960 were really the mystery. They're like, where are these long 0:19:29.080 --> 0:19:32.520 period comets coming from? They couldn't explain it. They shouldn't 0:19:32.560 --> 0:19:36.120 stick around. And so to explain where the new ones 0:19:36.200 --> 0:19:38.919 were coming from, they said, maybe there's a huge blob 0:19:38.960 --> 0:19:41.760 of them somewhere out there beyond where we can see. Oh, 0:19:41.800 --> 0:19:44.600 I see, you're saying these long period comments. They're sort 0:19:44.600 --> 0:19:46.960 of coming out of left field. Doesn't look like they're 0:19:46.960 --> 0:19:48.879 hanging out with us, or have been hanging out with 0:19:48.920 --> 0:19:52.000 us for a long time. It's like they're coming from 0:19:52.080 --> 0:19:55.280 somewhere else. Yeah, because they can't last for very long. Like, 0:19:55.359 --> 0:19:57.760 once you see a comet, you're seeing it in the 0:19:57.880 --> 0:20:00.360 end of its life cycle. It could have been out 0:20:00.400 --> 0:20:02.760 happily for billions of years deep out there in the 0:20:02.760 --> 0:20:05.080 Solar System. But once you see it, that means it's 0:20:05.119 --> 0:20:07.800 falling towards the Sun and it's going to get boiled 0:20:07.840 --> 0:20:10.160 away as it goes around the Sun, and it can't 0:20:10.160 --> 0:20:13.240 survive for very long. And even if it does make 0:20:13.280 --> 0:20:15.560 it a hundred or two hundred orbits, it's got a 0:20:15.640 --> 0:20:18.399 high chance of getting kicked out of the Solar System 0:20:18.440 --> 0:20:21.560 being perturbed by the gravity of one of the outer planets. 0:20:21.600 --> 0:20:24.040 So once you see a comet, it means it's in 0:20:24.119 --> 0:20:26.639 its last chapter of its life in the Solar System. 0:20:26.760 --> 0:20:29.320 So we're still seeing comets four and a half billion 0:20:29.440 --> 0:20:31.679 years into the story of the Solar System. There has 0:20:31.760 --> 0:20:34.320 to be some fresh resupply every once in a while. 0:20:34.520 --> 0:20:36.440 I guess if you're seeing a comment, that means it's 0:20:36.440 --> 0:20:38.920 getting hit by the rays of the Sun, which is 0:20:38.960 --> 0:20:42.440 probably melting it. It's definitely melting it, and that's where 0:20:42.440 --> 0:20:44.720 the comets tail is. Right. People like to imagine the 0:20:44.720 --> 0:20:47.920 commets tails like little action lines in a cartoon that 0:20:48.000 --> 0:20:50.680 show you where it's moving. But the commets tail is 0:20:50.720 --> 0:20:54.080 not actually pointed away from the direction of the comets motion. 0:20:54.560 --> 0:20:57.480 It's pointed away from the sun because the tail comes 0:20:57.520 --> 0:21:01.840 from the sun boiling away all the stuff on the comet. Yeah, 0:21:02.000 --> 0:21:04.720 that's the signature tale of of comets. That's what it is. 0:21:04.880 --> 0:21:07.320 It's not really a tail. It's more like a haircut. 0:21:07.480 --> 0:21:12.159 Is that what you're saying, Yeah, precisely. And comets can 0:21:12.160 --> 0:21:15.080 actually have multiple tales. They can have tales going in 0:21:15.119 --> 0:21:18.080 different directions based on like the stuff that's in there 0:21:18.119 --> 0:21:21.160 that's good and getting boiled away different compositions. So it's 0:21:21.160 --> 0:21:24.399 pretty fascinating look at the tales of comets. It's pretty awesome. Okay. 0:21:24.400 --> 0:21:28.000 So then someone named Yon Ord in the fifties said, hey, 0:21:28.000 --> 0:21:31.760 maybe all of these weird long period comets are coming 0:21:32.000 --> 0:21:35.080