WEBVTT - From the Vault: Jupiter’s Children 0:00:05.800 --> 0:00:07.640 Hey, you, Welcome to Stuff to Blow your mind. My 0:00:07.720 --> 0:00:10.799 name is Robert Lamb and I'm Joe McCormick. And it's Saturday. 0:00:10.920 --> 0:00:13.920 The vault hangs open. And of course today's Vault episode 0:00:14.360 --> 0:00:16.400 is more than a regular Vault episode. It is a 0:00:16.440 --> 0:00:20.599 cosmic odyssey. That's right. We are going to meet Jupiter's children, 0:00:20.880 --> 0:00:26.080 the Galileean moons, the Jovian offspring. I don't have another synonym, 0:00:26.320 --> 0:00:28.760 the moons of Jupiter. Yes, you will go there. Yeah, 0:00:28.800 --> 0:00:31.800 it's like its own Solar system. Uh and and each 0:00:31.840 --> 0:00:36.080 one is just a fascinating, literally otherworldly destination. We can't 0:00:36.080 --> 0:00:37.960 wait till you get to the end and experience the 0:00:38.000 --> 0:00:44.960 fiery planes of Io. Welcome to Stuff to Blow your mind. 0:00:45.200 --> 0:00:59.480 From how Stuff Works dot com. It really is darker 0:00:59.480 --> 0:01:03.320 out here in the outer Solar System. Your space freighter's 0:01:03.400 --> 0:01:08.320 one remaining forest dome struggles but barely scrapes along, surviving 0:01:09.680 --> 0:01:13.600 the plants still put out leaves. It seems only yesterday 0:01:13.640 --> 0:01:16.679 that you defied orders to jettison the dome and return 0:01:16.760 --> 0:01:22.360 to Earth immediately, but instead you absconded. You took the 0:01:22.400 --> 0:01:26.840 plant life capsule, and you flew away away from the Sun, 0:01:28.480 --> 0:01:31.600 out into the Outer Solar System. You have only the 0:01:31.640 --> 0:01:34.399 forest and a pair of robots now to accompany you 0:01:34.880 --> 0:01:39.520 through this long twilight. You'd hope to pass beyond Jupiter 0:01:39.600 --> 0:01:42.880 and find refuge within the rings of Saturn, but the 0:01:42.920 --> 0:01:46.600 great gas giant will not be defied. It's massive gravity 0:01:46.680 --> 0:01:49.680 tugs at your humble freighter. The red eye of its 0:01:49.720 --> 0:01:53.920 century spanning storm taunts you as Jupiter drags you into 0:01:53.920 --> 0:01:57.960 the orbital realm of its many moons. But still there's hope. 0:01:58.440 --> 0:02:01.800 Perhaps one of the four Eater moons the Galilean moons 0:02:01.880 --> 0:02:06.680 will offer some place of refuge. But which of these 0:02:06.720 --> 0:02:09.959 strange and hostile worlds might serve as a new home 0:02:10.080 --> 0:02:15.040 for you and this geodesic refugium from Old Earth's lost 0:02:15.120 --> 0:02:20.799 bio diversity. Hey, welcome to stuff to blow your mind. 0:02:20.800 --> 0:02:23.240 My name is Robert Lamb and I'm Joe McCormick, and 0:02:23.280 --> 0:02:26.120 you should imagine yourself in the scenario we just described. 0:02:26.639 --> 0:02:30.520 You're in some kind of spacecraft, hopefully one that has 0:02:30.600 --> 0:02:33.600 some some plants along with it to keep you sustained 0:02:33.639 --> 0:02:36.760 through the long Outer Solar System journey, and no hostiles 0:02:36.760 --> 0:02:40.560 you know, more th onboard exactly, and you are caught 0:02:41.639 --> 0:02:44.840 in the gravitational influence of the planet Jupiter. You didn't 0:02:44.840 --> 0:02:47.640 mean to end up this way, but hey, you know, 0:02:47.960 --> 0:02:51.519 Jupiter's gravity is something that's difficult to escape. And now 0:02:51.680 --> 0:02:57.240 now you're stuck spiraling in towards Jupiter, slowly decaying in 0:02:57.320 --> 0:03:01.040 your orbit, getting closer and closer all the time. But 0:03:01.240 --> 0:03:03.200 one thing you have noticed is that you will get 0:03:03.280 --> 0:03:06.519 to see a close up view and perhaps, if you're 0:03:06.760 --> 0:03:11.600 lucky enough, maybe land on Jupiter's four largest moons, known 0:03:11.680 --> 0:03:15.200 as the Galilean moons. This is the tour we want 0:03:15.200 --> 0:03:18.200 to take you on today. Indeed, these moons are of 0:03:18.240 --> 0:03:22.600 course of immense interest to science. Now, one analogy that 0:03:22.639 --> 0:03:25.760 I think is interesting to help us understand the way 0:03:25.840 --> 0:03:30.160 the Jupiter system and its gravitational influence works, is to 0:03:30.200 --> 0:03:34.840 think of Jupiter kind of like a star within our 0:03:34.880 --> 0:03:38.920 solar system, like it's its own star, and the planet, 0:03:38.960 --> 0:03:41.280 the moons that are going around Jupiter a kind of 0:03:41.320 --> 0:03:46.240 like planets orbiting this solar system within a solar system. Indeed, 0:03:46.280 --> 0:03:50.560 because it is a massive planet, it's mass is three 0:03:50.600 --> 0:03:54.480 hundred and seventeen point eight to eight uh times that 0:03:54.640 --> 0:03:58.960 of Earth, and uh it's of course a gas giant 0:03:59.000 --> 0:04:01.880 it's mostly gas. It might have a solid core about 0:04:01.880 --> 0:04:05.480 the size of Earth at the center, possibly a rocky 0:04:05.560 --> 0:04:09.400 ice covered core with insane levels of atmospheric pressure and 0:04:09.480 --> 0:04:13.680 temperatures hotter than the surface of the Sun. And Jupiter 0:04:13.760 --> 0:04:18.840 features no fewer than sixty seven lunar objects. That includes 0:04:18.920 --> 0:04:24.240 fifty confirmed moons and seventeen unconfirmed or provisional moons. Yeah, 0:04:24.240 --> 0:04:26.520 and these are the ones we know about. Yeah, but yeah, 0:04:26.560 --> 0:04:30.719 and they've got cool names like Metis and and Drastia. 0:04:30.800 --> 0:04:33.240 And then of course there's also the There are also 0:04:33.360 --> 0:04:37.320 three faint gossamer rings around Jupiter as well, certainly not 0:04:37.400 --> 0:04:41.200 as robust as the Saturn's rings, but they're there nonetheless. 0:04:41.200 --> 0:04:43.120 So we should back up and start at the beginning, 0:04:43.240 --> 0:04:48.200 because we're learning a whole lot more about Jupiter's moons, 0:04:48.279 --> 0:04:51.360 especially Jupiter's Galilean moons, the ones we're going to focus 0:04:51.360 --> 0:04:55.440 on today, the four largest moons, But we were learning 0:04:55.480 --> 0:04:57.600 a lot more about that recently. But we've known about 0:04:57.640 --> 0:05:01.000 Jupiter since ancient times because you don't need a telescope 0:05:01.080 --> 0:05:03.880 to see Jupiter. That's right, it's visible from Earth, and 0:05:03.920 --> 0:05:07.200 so it factors into many ancient systems of astrology by 0:05:07.320 --> 0:05:11.520 virtue virtue of that cosmology. The Roman name Jupiter stems 0:05:11.520 --> 0:05:13.880 from the king of the gods, but the planet to 0:05:13.960 --> 0:05:17.000 plays a role in many cultural beliefs. In Chinese astrology, 0:05:17.040 --> 0:05:20.200 for instance, it's the character of Foo uh character of 0:05:20.200 --> 0:05:22.599 foods tied to Jupiter, and he's the embodiment who is Foo. 0:05:22.960 --> 0:05:26.359 He's the embodiment of good fortune uh, symbolized in a 0:05:26.480 --> 0:05:30.599 scholars dress, and he's cradling a child. The three stars 0:05:30.640 --> 0:05:33.480 that you'll often see. You often see these three statues 0:05:33.520 --> 0:05:37.320 of these men in Chinese households, Chinese businesses uh. And 0:05:37.360 --> 0:05:40.080 they each kind of they each represent a different form 0:05:40.200 --> 0:05:43.600 of of idealized to success. So one is old and 0:05:43.680 --> 0:05:46.479 wise one and one is a successful with his family, 0:05:46.600 --> 0:05:49.080 and the other one is successful with business. I always 0:05:49.120 --> 0:05:52.240 think it's interesting that we see this cross cultural phenomenon 0:05:52.279 --> 0:05:57.200 of associating planetary bodies or objects in the sky with gods. Yeah, 0:05:57.279 --> 0:06:00.640 it's fascinating because you see this in other systems as well. 0:06:00.680 --> 0:06:04.279 For instance, the Vedic astrology, Jupiter is everything from the 0:06:04.360 --> 0:06:08.920 dwarf incarnation of Vishnu to to Ganesha or sometimes Brahma. 0:06:09.080 --> 0:06:12.160 So it it varies with within that system. But yeah, 0:06:12.200 --> 0:06:15.000 that Jupiter always seems to have a pretty cushy role 0:06:15.560 --> 0:06:19.200 within a given a given cultures astrology. Yeah, so we 0:06:19.240 --> 0:06:22.120 mentioned that ancient cultures knew about Jupiter because you can 0:06:22.120 --> 0:06:23.960 see it with the naked eye, But one of the 0:06:23.960 --> 0:06:28.600 things they didn't know was much more about Jupiter other 0:06:28.640 --> 0:06:31.679 than it being a point of light. That's right. For instance, 0:06:31.720 --> 0:06:34.159 when we think of Jupiter, what what do we picture? 0:06:34.200 --> 0:06:36.719 We picture that big, big gas giant with a big 0:06:36.720 --> 0:06:39.880 red eye, right, red spot, Yeah, the giant red hurricane 0:06:39.880 --> 0:06:43.720 on Jupiter's outer surface. Yeah, it's great to focus in 0:06:43.800 --> 0:06:46.080 on on the red storm because it helps us really 0:06:46.160 --> 0:06:50.000 understand Jupiter and our relationship to Jupiter. Because, for one, 0:06:50.000 --> 0:06:53.440 on one hand, that storm has not been there forever, uh, 0:06:53.480 --> 0:06:56.360 and it will not be there forever, but it spans centuries, 0:06:56.520 --> 0:06:58.200 it's been there as long as we've been able to 0:06:58.279 --> 0:07:00.919 see Jupiter in that kind of detail. Uh. And it 0:07:01.120 --> 0:07:03.520 in the storm itself is two to three times the 0:07:03.600 --> 0:07:07.640 size of Earth. Uh. So that helps put again the 0:07:07.680 --> 0:07:10.840 massive scale of Jupiter. Can you imagine in reference if 0:07:10.880 --> 0:07:14.640 on Earth we had storms that lasted for I don't know, 0:07:14.760 --> 0:07:17.800 hundreds of years. I've I've thought about it, like when 0:07:17.800 --> 0:07:20.480 you start teasing apart our weather system and you start 0:07:20.720 --> 0:07:24.440 looking at the different the different systems involved there, and 0:07:24.640 --> 0:07:28.640 the different factors that end up decreasing a hurricane's power. 0:07:28.760 --> 0:07:30.240 You know, what if those were not there? What if 0:07:30.240 --> 0:07:33.640 you had a scenario where the storm was essentially just 0:07:33.680 --> 0:07:37.640 a permanent part of the planet as a mortal individual 0:07:37.680 --> 0:07:40.280 would experience it. You know, that would be a great 0:07:40.320 --> 0:07:42.920 set up for like a sci fi thriller. Imagine the 0:07:42.960 --> 0:07:46.840 weather conditions on Earth change that such that tornadoes tend 0:07:46.920 --> 0:07:49.720 not to dissipate on their own unless you have to. 0:07:49.880 --> 0:07:52.880 You have to find a way to essentially dissipate tornadoes 0:07:52.880 --> 0:07:56.680 by force. Yeah, indeed, and that that red storm on 0:07:56.760 --> 0:08:02.520 Jupiter is dissipating slowly but still there as of this recording. Now, 0:08:02.560 --> 0:08:04.760 as far as how far away Jupiter is, it's fo 0:08:05.520 --> 0:08:09.640 four million miles seven million kilometers or five point two 0:08:09.640 --> 0:08:14.120 astronomical units uh from the planet Earth. Okay, so we 0:08:14.160 --> 0:08:17.800 know Jupiter is a gas giant, but you always wonder 0:08:17.920 --> 0:08:20.080 what's inside a gas giant. I mean, is it all 0:08:20.200 --> 0:08:24.080 just gas or is there something solid inside there? Well, 0:08:24.480 --> 0:08:28.240 we don't know for certain. We Uh, the atmosphere of 0:08:28.320 --> 0:08:31.240 Jupiter is mostly hydrogen and helium, but it might have 0:08:31.320 --> 0:08:34.800 a solid core about the size of Earth, and this 0:08:34.960 --> 0:08:38.400 might be an icy covered core with just really insane 0:08:38.480 --> 0:08:41.480 levels of atmospheric pressure and temperature is hotter than the 0:08:41.480 --> 0:08:44.280 surface of the Sun. So it's very much the core 0:08:44.320 --> 0:08:47.199 and not you know, not the surface of the planet. 0:08:47.720 --> 0:08:50.160 But but you know, you can't help it. Imagine, well, 0:08:50.200 --> 0:08:52.680 what if what if you could what if you could 0:08:52.720 --> 0:08:57.960 transport yourself down to the physical surface of this gas world. 0:08:59.360 --> 0:09:02.040 It would of course be just unimaginable with one of 0:09:02.080 --> 0:09:05.960 the most hostile environments you can even envision in the 0:09:06.040 --> 0:09:08.800 Solar System. Yeah, it's pretty rough. And one of the 0:09:08.800 --> 0:09:11.480 things that's going to come up repeatedly I think today 0:09:11.760 --> 0:09:16.240 is how Jupiter, though it may look very serene and 0:09:16.280 --> 0:09:20.640 beautiful to us, is it kind of meets that analogy 0:09:20.679 --> 0:09:22.600 I worked out at the beginning about it being like 0:09:22.679 --> 0:09:28.040 a star, because Jupiter is it has massive gravitational influence, 0:09:28.120 --> 0:09:32.679 it's very electrically active, and it's just it's just full 0:09:32.720 --> 0:09:38.640 of radiation. You don't want to go near Jupiter. Yeah, Yeah, 0:09:38.679 --> 0:09:41.320 to be sucked into Jupiter would be to be sucked 0:09:41.320 --> 0:09:43.760 into death, really, and that's one of the things we're 0:09:44.040 --> 0:09:46.600 out lying in the intra material. Yeah, so it's really 0:09:46.679 --> 0:09:50.720 unfortunate that we're slowly spiraling into Jupiter in today's thought experiment. 0:09:50.800 --> 0:09:53.520 But but we should at least take the time to 0:09:53.600 --> 0:09:56.560 appreciate the sites we'll see along the way. That's right. 0:09:56.640 --> 0:10:00.280 And uh and and maybe if we're lucky, grasp onto 0:10:00.320 --> 0:10:03.760 them and uh and seek refuge refuge upon them, because 0:10:03.760 --> 0:10:06.679 even though they are all very hostile worlds in their 0:10:06.679 --> 0:10:09.120 own right, uh, there's still a better bargain and they 0:10:09.160 --> 0:10:12.679 still present a better chance for not only the potential 0:10:12.760 --> 0:10:16.440 like the real life potential for for human visitation, but 0:10:16.640 --> 0:10:20.120 in some of these cases we'll discuss the possibility for 0:10:20.240 --> 0:10:25.680 extraterrestrial life. Yeah, Okay, Now, Jupiter is not entirely unexplored today. 0:10:25.760 --> 0:10:28.760 We've actually sent quite a few probes Jupiter's way that 0:10:28.800 --> 0:10:32.720 have that have orbited Jupiter and made various observations about 0:10:32.800 --> 0:10:35.800 it and it's major satellites, right, that's right. To date, 0:10:36.000 --> 0:10:39.520 NASA has sent nine space missions to or buy the 0:10:39.559 --> 0:10:43.480 gas giant. So we're talking to the the Pioneer Program seventy four, 0:10:43.640 --> 0:10:49.120 the Voyager Program seventy nine. Ulysses into Cassini in two 0:10:49.160 --> 0:10:54.280 thousand new horizons in two thousand seven. Also, Galileo is 0:10:54.280 --> 0:10:58.120 a big one, and that's a through two thousand three Juno. 0:10:59.000 --> 0:11:02.480 That one's of course a very current that's two thousands sixteen. 0:11:02.960 --> 0:11:07.920 And uh, there are various additional missions and schemes for 0:11:08.040 --> 0:11:09.920 missions in the works. Oh yeah, I know the e 0:11:10.120 --> 0:11:13.199 s A is working on the Juice Explorer, right, the 0:11:13.920 --> 0:11:18.320 Jupiter Icy Moon Explorer, which I don't know. I don't 0:11:18.360 --> 0:11:21.000 know if I agree with the wisdom of calling it Juice. 0:11:21.520 --> 0:11:25.560 It's it seems just a little too cool, like like 0:11:25.640 --> 0:11:27.800 it's like the name doesn't need to be that cool 0:11:28.040 --> 0:11:30.599 because it's going to Jupiter exactly know, it's going to 0:11:30.640 --> 0:11:34.120 the moons of Jupiter. That alone is is just mind bending. Yeah, 0:11:34.120 --> 0:11:36.800 and so hopefully it's going to explore three of the 0:11:36.840 --> 0:11:38.840 four main moons we're going to talk about today, the 0:11:39.000 --> 0:11:42.320 icy moons of the icy Galilean moons of Jupiter. And 0:11:42.400 --> 0:11:45.480 it's launching in two right, Yeah, I believe that's the 0:11:45.480 --> 0:11:49.440 current plant. And NASA is currently putting together the Europa 0:11:49.520 --> 0:11:52.880 Multiple flat by mission for the same time period. Alright, 0:11:52.920 --> 0:11:56.240 So I mentioned earlier thinking about the Jupiter system like 0:11:56.320 --> 0:11:58.960 a solar system within a solar system. And if you 0:11:59.040 --> 0:12:01.120 do that, of course you've lots of bodies out there. 0:12:01.120 --> 0:12:05.160 We mentioned the sixties seven known satellites of Jupiter, things 0:12:05.200 --> 0:12:07.360 that are orbiting, but a lot of them are very small. 0:12:08.160 --> 0:12:10.840 If we do think about Jupiter like a solar system, 0:12:10.880 --> 0:12:14.800 it has four main planets. That's right, they stand out 0:12:14.840 --> 0:12:17.280 and the most due they're just their sheer size. And 0:12:17.320 --> 0:12:23.800 these are Calisto, Ganymede, Europa, and Io. So you can 0:12:23.800 --> 0:12:26.520 think of them as it's four scoops on a on 0:12:26.559 --> 0:12:30.160 a Jovian ice cream cone, and you get the following 0:12:30.160 --> 0:12:35.560 flavors of scoops. You'll get salty craters, magnets, ice, and 0:12:35.640 --> 0:12:39.000 of course lava lava. That's a good flavor. Now, Robert, 0:12:39.000 --> 0:12:40.560 did you know that you seem to be you're a 0:12:40.600 --> 0:12:44.079 fan of ice cream metaphors? I did. I use them 0:12:44.080 --> 0:12:46.680 when thinking about planets. I use them when thinking about 0:12:46.960 --> 0:12:49.360 the brains. Though. Is this a good way of explaining 0:12:49.360 --> 0:12:51.840 things to children? Did they just really grasp onto ice 0:12:51.840 --> 0:12:55.000 cream metaphors? You know? I don't know. I guess it's 0:12:55.000 --> 0:12:58.440 a good way to explain it to the child within Um, yeah, 0:12:58.520 --> 0:13:00.079 I mean maybe it comes back to sort of like 0:13:00.120 --> 0:13:03.120 a Sesame Street mentality. You know, like I grew up 0:13:03.160 --> 0:13:06.520 watching these visual representations, and it seems like it seems 0:13:06.520 --> 0:13:08.320 like there were more than one Sesame Street skit that 0:13:08.320 --> 0:13:10.920 had ice cream in them, So maybe that that ended 0:13:10.960 --> 0:13:13.080 up sticking. I guess that does make sense. But it 0:13:13.200 --> 0:13:15.320 is interesting to think about the flavors of each of 0:13:15.320 --> 0:13:17.199 these moons because they kind of do each have their 0:13:17.200 --> 0:13:20.560 own flavor, especially the inner two I think, yes, yeah, 0:13:20.600 --> 0:13:24.079 each one is is its own weird world with its 0:13:24.080 --> 0:13:28.240 own properties, its own unique landscape, and that's why we 0:13:28.280 --> 0:13:32.040 wanted to take our listeners on a journey through each one. Now, 0:13:32.040 --> 0:13:34.160 one thing we should mention about all of these worlds 0:13:34.200 --> 0:13:36.360 that's kind of different than most of the inner planets 0:13:36.360 --> 0:13:38.040 of the Solar system that we think about that have 0:13:38.160 --> 0:13:41.679 like a soul, uh you know, a solar rotational day, 0:13:42.040 --> 0:13:45.199 is that all of these moons are tidally locked with Jupiter. 0:13:45.800 --> 0:13:50.079 The same side of the Moon always faces in towards Jupiter. Yes, 0:13:50.160 --> 0:13:53.280 almost like they're completely obedient. They dare not look away 0:13:53.280 --> 0:13:56.319 from their their master, right yeah. Or or it's kind 0:13:56.320 --> 0:13:58.520 of like in in Mario, you know, they're afraid to 0:13:58.520 --> 0:14:00.560 turn their back on the ghosts because when the ghost 0:14:00.640 --> 0:14:03.559 comes to get you. So we mentioned that these are 0:14:03.559 --> 0:14:07.160 referred to as the Galilean moons, and we should probably 0:14:07.200 --> 0:14:10.280 explain first how they were discovered and why they're called 0:14:10.280 --> 0:14:14.760 the Galilean moons. Today. The obvious conclusion you might reaches 0:14:14.880 --> 0:14:18.040 that they're named after Galileo. You know, he's an astronomer, 0:14:18.520 --> 0:14:20.760 and if you assume to that, you'd be right. That's 0:14:20.760 --> 0:14:23.480 where the name comes from. That's right. And I think 0:14:23.640 --> 0:14:25.400 most of you are probably familiar at least a little 0:14:25.440 --> 0:14:31.400 bit with Italian astronomer slash heretic Galileo galile He who 0:14:31.600 --> 0:14:34.520 was born in fifteen sixty four died in sixteen forty two, 0:14:34.520 --> 0:14:38.200 and he was a true renaissance man, uh in the Renaissance. 0:14:38.560 --> 0:14:42.400 He was also a physicist and engineer, a philosopher, a mathematician, 0:14:42.760 --> 0:14:45.360 a true superstar in the history of science and really 0:14:45.400 --> 0:14:48.880 in the history of human civilization in general. It's really 0:14:49.200 --> 0:14:52.400 it's really difficult to to overstate the importance the importance 0:14:52.400 --> 0:14:56.120 of Galileo. Yeah, I mean often today scientific struggles against 0:14:56.240 --> 0:15:00.280 ingrained orthodoxy are framed in terms of Galileo's struggle against 0:15:00.360 --> 0:15:03.840 the the scientific and religious orthodoxy of the day. Both 0:15:03.880 --> 0:15:06.920 of which opposed him. Yeah, well, our listeners a little 0:15:06.960 --> 0:15:10.440 more about the controversy surrounding helio centritism. All right, yeah, well, 0:15:10.440 --> 0:15:14.160 so you'll probably associate Galileo with helio centrism. The idea 0:15:14.320 --> 0:15:16.760 that the planets in the Solar System go around the 0:15:16.800 --> 0:15:19.880 Sun could have also the day in the at the 0:15:19.920 --> 0:15:22.760 time meant that everything in the universe goes around the Sun. 0:15:22.800 --> 0:15:25.240 Of course, now we know that's not correct, but we 0:15:25.240 --> 0:15:28.080 were still very much working our way outward and our 0:15:28.160 --> 0:15:31.400 understanding of the universe. But it was certainly onto something 0:15:31.440 --> 0:15:33.480 in the idea that the Earth goes around the Sun 0:15:33.560 --> 0:15:35.600 and not the other way around the Earth end all 0:15:35.640 --> 0:15:38.560 the other bodies in the Solar System. And so Galileo 0:15:38.680 --> 0:15:41.800 did not come up with the idea of heliocentrism. He 0:15:41.840 --> 0:15:44.520 didn't invent this. This was a Copernican idea. It was 0:15:44.560 --> 0:15:47.640 already in circulation, and Galileo was one of the Copernican 0:15:47.680 --> 0:15:52.480 astronomers of the seventeenth century. However, a version of the 0:15:52.560 --> 0:15:57.720 geocentric Aristotelian Ptolemaic model was what was dominant in the day, 0:15:57.840 --> 0:16:00.920 was what most people believed. And in this model, the 0:16:01.040 --> 0:16:04.480 Earth is It's not just that the Sun goes around 0:16:04.480 --> 0:16:07.160 the Earth, and the Moon goes around the Earth and 0:16:07.200 --> 0:16:10.040 all that. It's that the Earth is literally the center 0:16:10.080 --> 0:16:14.120 of motion in the universe. So by by a principle 0:16:14.200 --> 0:16:18.040 that centers on the Earth, the whole universe just goes 0:16:18.120 --> 0:16:21.200 all goes around us. So we're what everything else is 0:16:21.240 --> 0:16:25.280 focused on. And the role of Galileo's discovery is that 0:16:25.400 --> 0:16:29.400 in observing the sphere of Jupiter's gravitational influence, Galileo provided 0:16:29.440 --> 0:16:33.520 new evidence against that type of geocentrism that dominated in 0:16:33.600 --> 0:16:37.720 his day, and one one piece of evidence became apparent 0:16:37.840 --> 0:16:42.200 in January six when Galileo made his first round of 0:16:42.400 --> 0:16:47.560 observations through a telescope looking at Jupiter. So Galileo also, 0:16:47.840 --> 0:16:51.440 like not inventing helio centrism, did not invent the telescope, 0:16:51.560 --> 0:16:54.240 but what he did do was improved it. He made 0:16:54.240 --> 0:16:56.720 a series of improvements to a design of the telescope 0:16:56.720 --> 0:17:00.160 that allowed him to resolve farther objects than ever before, 0:17:00.560 --> 0:17:03.640 and by the time Galileo got the magnification power of 0:17:03.680 --> 0:17:07.080 his telescope cranked up to twenty times, he aimed at 0:17:07.119 --> 0:17:10.560 the planet Jupiter and he saw something really weird. As 0:17:10.560 --> 0:17:14.920 we mentioned earlier, you can see Jupiter with the naked eye, right, yes, yeah, 0:17:14.920 --> 0:17:18.359 And so ancient astronomers had been seeing Jupiter for a 0:17:18.400 --> 0:17:20.680 long time. They're already aware of its existence. But what 0:17:20.720 --> 0:17:25.159 Galileo saw when he focused on Jupiter was interesting. He 0:17:25.240 --> 0:17:30.359 saw stars. He saw three stars lined up right next 0:17:30.400 --> 0:17:34.679 to Jupiter, almost as if strung along a spear extending 0:17:34.680 --> 0:17:39.360 out through Jupiter's equator. So Galileo made a note of this, 0:17:39.560 --> 0:17:42.440 and he decided to check back on it later. Now, 0:17:42.480 --> 0:17:45.440 if those had been stars that were just in the background, 0:17:45.560 --> 0:17:47.240 you know, if they just happened to line up with 0:17:47.359 --> 0:17:50.760 Jupiter from the star field beyond the next time you 0:17:50.840 --> 0:17:53.320 looked at Jupiter, they shouldn't be there, right, because Jupiter 0:17:53.359 --> 0:17:56.639 should have moved on relative to the background starfield. Right. 0:17:56.640 --> 0:17:59.080 They shouldn't be following the planet because there would be 0:17:59.160 --> 0:18:02.840 distant opjecs ex on the planet exactly. But instead the 0:18:02.920 --> 0:18:07.399 stars followed Jupiter. Where Jupiter went, the spear of stars 0:18:07.440 --> 0:18:13.119 followed and they change their positions relative to Jupiter. And 0:18:13.200 --> 0:18:16.000 so after some observation, Scalio realized that there are actually 0:18:16.040 --> 0:18:19.639 four stars on this spear, not just three. And the 0:18:19.680 --> 0:18:23.960 conclusion he realized was that these weren't stars. The star 0:18:24.000 --> 0:18:26.679 spear was not a star spear, it was a moon spear. 0:18:26.800 --> 0:18:30.160 These are moons that are orbiting Jupiter the same way 0:18:30.240 --> 0:18:34.840 Earth's moon orbits the Earth. And so, okay, well, so 0:18:35.000 --> 0:18:37.879 Jupiter has moons. What does that mean for the cosmological 0:18:37.920 --> 0:18:41.480 debate of the day. Well, if there are moons orbiting Jupiter, 0:18:42.240 --> 0:18:46.320 it disproves the Aristotelian principle that Earth is the universal 0:18:46.520 --> 0:18:50.639 hub of motion of planetary bodies. Those moons don't orbit 0:18:50.680 --> 0:18:53.840 the Earth, they orbit something else. And so this gives 0:18:53.840 --> 0:18:57.440 you a kind of general principle of things orbiting things 0:18:57.560 --> 0:19:01.639 rather than everything orbiting Earth. And it's clear that there's 0:19:01.720 --> 0:19:04.840 more than one center of motion possible. There at least 0:19:04.840 --> 0:19:07.439 two that now that we know of Jupiter and Earth. 0:19:07.920 --> 0:19:10.080 And if there are two, you can assume they're probably 0:19:10.119 --> 0:19:12.440 more than two. And this eventually led to the type 0:19:12.440 --> 0:19:15.200 of thinking that showed us what was really out there 0:19:15.200 --> 0:19:18.240 in terms of heliocentrism in the way gravity works. Now, 0:19:18.240 --> 0:19:21.840 I should also add that the discovery of Jupiter's moons 0:19:22.000 --> 0:19:25.720 wasn't unique to Galileo, and he wasn't even necessarily the 0:19:25.760 --> 0:19:27.920 only or first person to have discovered them. I found 0:19:27.920 --> 0:19:30.639 accounts that at least one other guy, a German astronomer 0:19:30.720 --> 0:19:34.880 named Simon Marius, discovered them independently at around the same time. 0:19:34.920 --> 0:19:38.800 And it's also been suggested that an ancient Chinese astronomer 0:19:38.880 --> 0:19:41.560 named Gone Day might have discovered one of the moons 0:19:41.560 --> 0:19:44.920 of Jupiter in the fourth century b c e. When 0:19:44.960 --> 0:19:50.040 he said that he saw around Jupiter a small red star. Now, technically, 0:19:50.119 --> 0:19:53.000 under the right circumstances, the moons of Jupiter should be 0:19:53.119 --> 0:19:56.200 visible to the naked eye from Earth, and the only 0:19:56.240 --> 0:19:58.760 thing that really prevents it is that Jupiter is too bright. 0:19:59.040 --> 0:20:01.560 You look up at Jupiter and it's it's so bright 0:20:01.640 --> 0:20:04.320 that it drowns out other tiny points of light that 0:20:04.359 --> 0:20:06.600 are close to it, so you can't usually see them. 0:20:06.600 --> 0:20:09.040 But if Jupiter weren't there, you should be able to 0:20:09.080 --> 0:20:12.000 see these objects. Oh but you know what, I think 0:20:12.080 --> 0:20:15.720 that sound means that we're coming up on Jupiter's first 0:20:15.800 --> 0:20:18.720 gal and moon spiraling in from the outside, and that's 0:20:18.720 --> 0:20:21.800 going to be the moon Callisto. Yes, and I think 0:20:21.800 --> 0:20:24.400 this is this is a pretty good pit stop to consider. 0:20:24.880 --> 0:20:28.640 So Callisto is about the size of the planet Mercury. 0:20:29.160 --> 0:20:33.400 It's the third largest moon in the entire Solar System, 0:20:33.680 --> 0:20:36.680 and it's the outermost of the four Galileean moons. As 0:20:36.680 --> 0:20:41.479 we've discussed, uh, it orbits beyond Jupiter's main radiation belts. 0:20:42.160 --> 0:20:45.840 So Jupiter is highly radioactive, it's putting out a lot 0:20:45.920 --> 0:20:49.199 of scary stuff, but Callisto is far enough away that 0:20:49.400 --> 0:20:53.239 it's relatively safe. That's right. Yeah, we're we're outside of 0:20:53.280 --> 0:20:57.960 that that death lea, the death zone. Yeah. It's also 0:20:58.040 --> 0:21:01.600 the most heavily cratered o chick in the Solar system. 0:21:01.720 --> 0:21:04.840 So that's interesting. Yeah, this is this is really fascinating. 0:21:04.920 --> 0:21:07.680 So as we as we as we we get closer 0:21:07.680 --> 0:21:10.000 and closer, as we're able to observe the surface of 0:21:10.040 --> 0:21:13.760 Callisto and maybe i know, hopefully even get out even 0:21:13.880 --> 0:21:18.120 land our vessel and find a semi permanent home on 0:21:18.240 --> 0:21:21.320 this uh this this strange moon. You would find that 0:21:21.520 --> 0:21:24.000 the surface, to to walk the surface of Callisto would 0:21:24.000 --> 0:21:27.879 be to walk a dead landscape of craters and occasional 0:21:28.280 --> 0:21:32.280 small icy peaks. And this surface, this landscape has not 0:21:32.480 --> 0:21:36.439 changed in four billion years. Yeah, that's one of the 0:21:36.480 --> 0:21:40.520 things that we often associate having heavy cratering with, right, 0:21:40.640 --> 0:21:44.199 like more cratering. You see the older the surfaces, because 0:21:44.560 --> 0:21:46.760 what does cratering mean? It's been like that a long 0:21:46.800 --> 0:21:49.480 time without any kind of repaving. That's right. This is 0:21:49.680 --> 0:21:54.760 the last time Callisto suffered any extensive resurfacing was four 0:21:54.760 --> 0:21:58.719 billion years ago. And there are no plate tectonics, there 0:21:58.720 --> 0:22:03.680 are no volcanoes, a no active geology to alter the landscape. 0:22:03.920 --> 0:22:08.640 So it seems like a kind of quiet, serene, dead Yeah. 0:22:08.680 --> 0:22:10.919 I mean it's like a dinosaur world. Right. It's like 0:22:10.960 --> 0:22:13.760 the moon itself is only four point five billion years old, 0:22:13.800 --> 0:22:17.520 and again it hasn't changed in four billion um. It's 0:22:17.520 --> 0:22:20.400 also the darkest of the four moons that we're discussing here, 0:22:20.600 --> 0:22:24.240 in the least dents. So Callisto's composition is about half 0:22:24.280 --> 0:22:28.080 water ice and half rocky material, and the mean surface 0:22:28.080 --> 0:22:31.919 temperature of Callisto is negative two and eighteen point forty 0:22:31.960 --> 0:22:36.000 seven degrees fahrenheit, and the thin atmosphere consists of mostly 0:22:36.200 --> 0:22:39.959 carbon dioxide. Okay, so it may be very quiet and 0:22:40.040 --> 0:22:43.399 serene on this on this seemingly dead rock. But should 0:22:43.400 --> 0:22:46.240 we take away from that that Callisto is definitely not 0:22:46.359 --> 0:22:49.520 a place to look for signs of life. Well, I 0:22:49.560 --> 0:22:52.000 think we've both watched enough science fiction to know that 0:22:52.000 --> 0:22:55.320 that world that you land on it seems dead is 0:22:55.359 --> 0:22:59.080 never It's not always really that dead. I have a 0:22:59.119 --> 0:23:02.160 sidetrack to take here. Do you notice how in science fiction, 0:23:02.200 --> 0:23:05.240 whenever you land on a planet that does turn out 0:23:05.240 --> 0:23:08.240 to have hostile aliens on it, you never land where 0:23:08.280 --> 0:23:11.960 the aliens are doing something. Right, then you always land 0:23:12.000 --> 0:23:14.240 in somewhere where there's no sign of them, and it's 0:23:14.240 --> 0:23:17.880 only after exploring for a while that you run into them. Yeah, 0:23:17.920 --> 0:23:19.919 it would be it would be interesting to have that 0:23:20.200 --> 0:23:23.960 story where the ship touches down and all the hideous 0:23:24.080 --> 0:23:28.000 night creatures are already out, you know, viciously killing the 0:23:28.080 --> 0:23:30.280 eight creatures that lived there during the day. I like 0:23:30.359 --> 0:23:33.320 how the the viciously killing motion you made was like 0:23:33.440 --> 0:23:36.040