WEBVTT - Why Is the Moon So Big? 0:00:00.200 --> 0:00:02.400 Hey, please take a second and leave us a review 0:00:02.480 --> 0:00:06.279 on Apple Podcasts, Spotify, or wherever you listen to the podcast. 0:00:06.960 --> 0:00:11.040 Thanks a lot. Hey, Welcome to Science Stuff, the production 0:00:11.160 --> 0:00:14.440 of iHeartRadio. I'm poor, Hey Champ, and today we are 0:00:14.560 --> 0:00:22.040 going to the Moon. You might think you know the moon, 0:00:22.360 --> 0:00:26.480 but actually it is full of scientific mysteries. We're going 0:00:26.480 --> 0:00:28.920 to be talking about where the moon came from, what 0:00:29.080 --> 0:00:31.720 it's made out of, and what it can tell us 0:00:31.760 --> 0:00:35.519 about how life started on Earth. So get ready to 0:00:35.560 --> 0:00:39.320 go over the moon as we tackle the unanswered questions 0:00:39.440 --> 0:00:49.320 about our mysterious moon enjoying. Hey everyone, Today we're talking 0:00:49.320 --> 0:00:53.640 to doctor Matt Siegler. Doctor Ziegler is a planetary scientist 0:00:53.640 --> 0:00:56.760 at the University of Hawaii who works on several missions 0:00:56.800 --> 0:01:00.680 for NASA and the European Space Agency, including did You 0:01:00.840 --> 0:01:04.120 Are the miss mission to put astronauts back on the Moon. 0:01:04.560 --> 0:01:07.600 He's going to answer three questions for us. Number one, 0:01:07.920 --> 0:01:10.520 where did the moon come from? As it turns out, 0:01:10.680 --> 0:01:13.840 it's really unusual for us to have such a big moon. 0:01:14.480 --> 0:01:18.640 Number two, why does the moon always faces the same way? 0:01:19.400 --> 0:01:23.160 Wasn't always the case? And number three, why are we 0:01:23.240 --> 0:01:26.080 going back to the moon? It turns out scientists have 0:01:26.160 --> 0:01:29.640 identified a deep mystery about the Moon that might have 0:01:29.800 --> 0:01:34.560 huge implications for space travel and our search for extraterrest 0:01:34.600 --> 0:01:40.280 deal life. So here's my conversation with doctor Matt Siegler. Well, 0:01:40.280 --> 0:01:42.160 thank you doctor Siegler for joining us again. 0:01:42.400 --> 0:01:43.399 Okay, welcome. 0:01:44.040 --> 0:01:46.200 The last time we talked it was New Year's and 0:01:46.240 --> 0:01:48.280 we talked about how the Earth goes around the Sun. 0:01:48.640 --> 0:01:50.840 And now we're getting close to the lunar New Year, 0:01:51.200 --> 0:01:53.520 so I thought it would be interesting to talk about 0:01:53.520 --> 0:01:53.920 the moon. 0:01:54.200 --> 0:01:58.440 Okay, that's actually my specialties. That's great to talk about 0:01:58.480 --> 0:01:59.760 something that I know. 0:02:01.640 --> 0:02:02.800 Are you saying you're a lunatic? 0:02:03.280 --> 0:02:06.760 Yes, yeah, we're proud to call ourselves lunatics. 0:02:08.200 --> 0:02:11.600 Well, in what ways is our moon unusual in the 0:02:11.720 --> 0:02:12.400 Solar System? 0:02:12.720 --> 0:02:17.000 Okay? Well, the weirdest thing about our moon is how 0:02:17.040 --> 0:02:20.920 big it is compared to Earth. There are a couple 0:02:20.960 --> 0:02:24.120 of moons out there, some of Saturn's moons and a 0:02:24.120 --> 0:02:26.720 couple of Jupiter's moons that are about the size of 0:02:26.760 --> 0:02:29.800 our moon or even a little bigger. But those planets 0:02:29.840 --> 0:02:32.480 are huge, right, you could fit I think it's thirteen 0:02:32.560 --> 0:02:35.760 hundred earths inside of Jupiter, right, Wow, huh. And so 0:02:36.000 --> 0:02:39.320 their biggest moon is a very small moon compared to 0:02:39.360 --> 0:02:41.200 the size of its body, meaning. 0:02:41.040 --> 0:02:43.839 Like if Jupiter had a moon that's proportionately the same 0:02:43.880 --> 0:02:46.400 size as our moon, it would be like the size 0:02:46.400 --> 0:02:47.400 of Saturn or something. 0:02:47.680 --> 0:02:50.079 Yeah, it would be like the size of Neptune at least. 0:02:50.200 --> 0:02:53.799 So yeah, And the only other planet that, if you 0:02:53.840 --> 0:02:55.880 want to call it a planet that has a similar 0:02:56.000 --> 0:02:56.480 is Pluto. 0:02:56.639 --> 0:02:56.880 Right. 0:02:56.960 --> 0:02:59.120 Oh, no, no, we don't talk about Pluto in this podcast. 0:02:59.280 --> 0:03:00.560 You don't talk about about plu. 0:03:00.720 --> 0:03:01.360 We don't know. 0:03:03.680 --> 0:03:06.880 Pluto has a moon that's about a tenth of its 0:03:06.880 --> 0:03:08.000 size or something like that. 0:03:08.120 --> 0:03:11.160 But plut itself is very small, smaller than us, right, 0:03:11.240 --> 0:03:12.520 smaller than our moon kind of. 0:03:12.880 --> 0:03:16.960 Yeah, Pluto is around it could fit inside the continental US. 0:03:17.120 --> 0:03:18.440 So it's a pretty small body. 0:03:18.600 --> 0:03:20.839 Okay, Oh, that's a very polite way to say it. 0:03:20.840 --> 0:03:23.440 It's a small body. Yes, yes, small body. 0:03:24.160 --> 0:03:27.480 So that's the weirdest thing about our moon is how 0:03:27.480 --> 0:03:29.040 big it is compared to us. 0:03:30.160 --> 0:03:33.639 So that's the first mystery about the moon. Why is 0:03:33.680 --> 0:03:36.600 it so big? None of the other planets have a 0:03:36.720 --> 0:03:37.760 moon this big. 0:03:38.200 --> 0:03:38.840 Why is that? 0:03:39.480 --> 0:03:43.520 Well, as it turns out, Charles Darwin's Sun George Darwin 0:03:43.880 --> 0:03:45.000 had a theory about that. 0:03:46.280 --> 0:03:48.680 So that's actually a funny part of the history is 0:03:48.840 --> 0:03:51.800 our moon is relatively large. It's about the size of 0:03:51.840 --> 0:03:55.920 the Pacific Ocean basin, and so Charles Darwin's son, I 0:03:55.960 --> 0:03:59.440 believe George Darwin first theorized that the Moon might have 0:03:59.600 --> 0:04:02.520 been created from the Earth by being spit out of 0:04:02.520 --> 0:04:05.040 the Pacific Ocean basin, and the Pacific Ocean was the 0:04:05.120 --> 0:04:09.360 hole left behind. So that's a good way to remember 0:04:09.400 --> 0:04:11.080 the size of the Moon is roughly the size of 0:04:11.080 --> 0:04:15.440 the Pacific Ocean, because that was one of the first thoughts, Well, well, 0:04:16.040 --> 0:04:17.960 we have a hole here on Earth that's about the 0:04:17.960 --> 0:04:18.720 size of the moon. 0:04:19.120 --> 0:04:21.839 Yeah, maybe that's came It was like a giant pimple 0:04:21.880 --> 0:04:24.800 that just popped off the Earth. That was the theory, yes, yes, 0:04:25.440 --> 0:04:31.760 or the Darwin giant pimple theory. Yeah, George Darwin didn't 0:04:31.839 --> 0:04:35.760 quite get thinks is right as this famous dad Charles Darwin, 0:04:36.800 --> 0:04:37.440 or did he? 0:04:39.040 --> 0:04:42.000 Now we kind of think it's crazy, but really how 0:04:42.040 --> 0:04:45.440 we think the moon formed now was not all that different. 0:04:45.560 --> 0:04:48.880 It's just that that spitting out happened in a big 0:04:48.920 --> 0:04:52.560 event when something the size of Mars or so collided 0:04:52.760 --> 0:04:57.520 into the early Earth and caused that event where material 0:04:57.600 --> 0:04:59.480 got spit out and formed the moon. 0:05:00.120 --> 0:05:03.039 That's a wild theory, Like we have a moon that's 0:05:03.240 --> 0:05:06.479 like gray white, but we think it happened because some 0:05:06.640 --> 0:05:09.960 giant mini planet crashed into the original Earth. 0:05:10.120 --> 0:05:12.560 Yeah, so that's the idea is the original early Solar 0:05:12.600 --> 0:05:15.400 system was full of things that were flying all around, 0:05:15.600 --> 0:05:18.719 and some of them collided into each other, and the 0:05:18.800 --> 0:05:21.760 debris of that collision formed something kind of like a 0:05:21.880 --> 0:05:24.680 ring of Saturn around the Earth. Right, it was a ring, 0:05:24.920 --> 0:05:27.360 and then that coalesced together and became the Moon. 0:05:27.720 --> 0:05:29.520 So like our Earth is a mix of those two 0:05:29.560 --> 0:05:31.600 original planets, and the Moon is a mix of those 0:05:31.600 --> 0:05:32.600 two original planets. 0:05:32.640 --> 0:05:33.120 Exactly. 0:05:34.279 --> 0:05:37.640 Yes, scientists think the way the moon form was that 0:05:37.720 --> 0:05:41.000 a planet the size of Mars crashed into a pre 0:05:41.240 --> 0:05:44.920 Earth planet about four and a half billion years ago, 0:05:45.320 --> 0:05:48.200 and then the debris from that crash clumped together and 0:05:48.320 --> 0:05:51.960 formed the Moon. But here's a big question, how do 0:05:52.040 --> 0:05:55.360 we know that? What makes us think that's how the 0:05:55.400 --> 0:05:59.000 Moon formed. Well, it turns out this idea started when 0:05:59.000 --> 0:06:01.520 we first walked on the Moon. 0:06:02.520 --> 0:06:06.200 And this explains basically what we found when the Apollo 0:06:06.240 --> 0:06:09.720 samples were returned in the nineteen sixties and seventies. Huh, 0:06:10.240 --> 0:06:14.359 was that a lot of the isotopes of atoms were 0:06:14.600 --> 0:06:17.640 incredibly similar between the Earth and the Moon. 0:06:18.279 --> 0:06:19.360 What do you mean isotopes? 0:06:19.560 --> 0:06:22.479 So normally an atom will have the same number of 0:06:22.520 --> 0:06:26.000 protons and neutrons, and so an isotope is one that 0:06:26.080 --> 0:06:28.480 has different numbers of neutrons. 0:06:28.120 --> 0:06:30.840 Okay than the normal one I see. And so it's 0:06:30.920 --> 0:06:34.239 where for the isotopes on Earth to match the ones 0:06:34.279 --> 0:06:34.680 on the Moon. 0:06:35.160 --> 0:06:37.839 Yeah, So that turns out to be one of the 0:06:37.920 --> 0:06:42.080 key identifiers of where something formed in the early Solar 0:06:42.120 --> 0:06:46.280 System is it's the isotopes of its different atoms, and 0:06:46.400 --> 0:06:48.680 particularly good one is oxygen. 0:06:49.960 --> 0:06:52.560 It turns out you can tell exactly where in the 0:06:52.560 --> 0:06:56.240 Solar System a piece of rock comes from by its isotopes. 0:06:56.760 --> 0:06:59.320 Like a piece of rock has more of one kind 0:06:59.320 --> 0:07:02.360 of oxygen or carbon, you can tell it came from 0:07:02.360 --> 0:07:06.480 close to the Sun, or near Jupiter, or way out 0:07:06.640 --> 0:07:08.520 at the edges of the Solar system. 0:07:09.400 --> 0:07:12.760 So we think the whole Solar System essentially was a 0:07:12.760 --> 0:07:15.240 big cloud of gas and dust that was leftover from 0:07:15.400 --> 0:07:18.640 some other star that exploded, right, huh, And that cloud 0:07:18.800 --> 0:07:22.040 kind of collust around the early Sun, and then when 0:07:22.080 --> 0:07:24.640 that Sun turned on, you know, very early in the 0:07:24.680 --> 0:07:28.080 Solar system four point six billion years ago, it heated 0:07:28.160 --> 0:07:33.560 that cloud and basically boiled off different isotope ratios as 0:07:33.560 --> 0:07:36.760 you went different distance from the Sun. And then when 0:07:36.760 --> 0:07:40.480 the planets formed, out of those different isotopic ratios as 0:07:40.480 --> 0:07:42.920 a function of distance away from the Sun, they seem 0:07:42.960 --> 0:07:47.040 to have checked those isotopes permanently after that. 0:07:47.400 --> 0:07:51.440 Interesting, it's like the rocks have a tag that says 0:07:51.560 --> 0:07:53.560 where in the Solar System formed. 0:07:53.800 --> 0:07:59.000 Yeah, so when we see a meteorite that we have 0:07:59.080 --> 0:08:03.640 identified has come from Mars or a meteorite from the 0:08:03.680 --> 0:08:08.280 Asteroid belt, these will have different oxygen isotope ratios than 0:08:08.560 --> 0:08:12.920 the Earth. But the Moon has almost the same as 0:08:12.960 --> 0:08:17.520 the Earth, like too incredible precision, such that the only 0:08:17.560 --> 0:08:20.280 way that we can explain it was that they essentially 0:08:20.320 --> 0:08:24.560 formed together as a single body. Okay, and so the 0:08:24.600 --> 0:08:27.559 Earth and the Moon are incredibly similar, and it could 0:08:27.560 --> 0:08:29.960 be that it's just kind of telling us they formed 0:08:29.960 --> 0:08:33.160 at the exact same distance from the Sun. But the 0:08:33.200 --> 0:08:36.720 precision in which they match seems to only be explained 0:08:36.720 --> 0:08:39.520 if they really formed together in this idea of the 0:08:39.559 --> 0:08:42.679 giant impact or simple. 0:08:44.080 --> 0:08:46.200 I see the match is too good. It's just too 0:08:46.240 --> 0:08:47.280 identical to the Earth. 0:08:47.360 --> 0:08:51.000 Yeah, Like these are identical twins, you know, they had 0:08:51.080 --> 0:08:52.280 to be born from the same mother. 0:08:53.040 --> 0:08:56.319 I see the DNA says their siblings, same mother, same father. 0:08:56.720 --> 0:09:00.760 Okay, And so there were lots of theory going around, 0:09:00.760 --> 0:09:02.920 and as far as I understand it, there was some 0:09:03.160 --> 0:09:07.320 international meeting about this in the early nineteen eighties and 0:09:07.360 --> 0:09:09.520 there was a lot of debate, and then out came 0:09:09.679 --> 0:09:12.200 the giant impact as the winner, and it's kind of 0:09:12.200 --> 0:09:13.440 been the standard since then. 0:09:13.920 --> 0:09:16.600 Interesting. So it's not like we have some smoking gun 0:09:16.640 --> 0:09:18.760 that says that this is what happened, or that there 0:09:18.760 --> 0:09:21.480 was a camera or somebody saw this happened. It's like, well, 0:09:21.559 --> 0:09:24.400 we can't think of anything else, and this is the 0:09:24.400 --> 0:09:25.680 only thing that we have left. 0:09:25.800 --> 0:09:28.960 Yeah, and everything that we find out knew about the 0:09:28.960 --> 0:09:32.840 Moon seems to fit with the theory of the giant impact. 0:09:33.120 --> 0:09:35.160 Like what like one of the things we found out 0:09:35.360 --> 0:09:37.960 was from seismometers on the Moon. We've been able to 0:09:37.960 --> 0:09:41.520 figure out that the Moon has a fairly small iron core, right, 0:09:42.000 --> 0:09:44.840 and the Earth actually has a really big iron core 0:09:45.679 --> 0:09:48.960 for its size. And so where did this extra iron 0:09:49.000 --> 0:09:52.160 on the Earth come from and the lack of iron 0:09:52.320 --> 0:09:54.920 on the Moon come from. Well, it may have been 0:09:54.960 --> 0:09:57.280 that you had this big impact and then more the 0:09:57.320 --> 0:10:00.400 iron went into the big object than into the small 0:10:00.440 --> 0:10:00.640 on it. 0:10:01.360 --> 0:10:01.640 Oh. 0:10:01.720 --> 0:10:05.240 I see, what do you think the junior Darwin would 0:10:05.280 --> 0:10:09.439 feel now that you've disproven his theory and not lived 0:10:09.520 --> 0:10:11.360 up to the greatness of the Darwin name. 0:10:12.840 --> 0:10:16.080 I don't know. I think scientists by nature like to 0:10:16.120 --> 0:10:19.520 know the truth or the facts about the matter, and 0:10:19.679 --> 0:10:22.040 if an idea that we clung to turns out to 0:10:22.080 --> 0:10:23.920 be wrong, we should kind of give it up. 0:10:24.080 --> 0:10:24.440 Yeah. 0:10:24.480 --> 0:10:27.360 So I think that was a strong philosophy of science 0:10:27.360 --> 0:10:28.720 then and it still is today. 0:10:29.080 --> 0:10:32.439 Nice all right, when we come back, we're going to 0:10:32.480 --> 0:10:35.520 tackle the second big mystery about the moon, which is 0:10:35.960 --> 0:10:39.400 why is the Moon always facing us the same way? 0:10:39.840 --> 0:10:42.200 In case you haven't noticed, every time you look at 0:10:42.200 --> 0:10:44.640 the Moon, no matter where you are on the planet 0:10:44.880 --> 0:10:46.920 or what time of the month or year, it is, 0:10:47.480 --> 0:10:50.640 the features on the Moon always look the same, even 0:10:50.679 --> 0:10:53.280 though it's spinning around the Earth. How can it be 0:10:53.400 --> 0:10:56.160 that it's training at just the right rate for it 0:10:56.200 --> 0:10:58.439 to always look the same to us? 0:10:59.000 --> 0:10:59.719 We'll answer that. 0:10:59.720 --> 0:11:02.120 Question and more after the break. 0:11:02.559 --> 0:11:14.320 We'll be right back. Hey, we'll come back. 0:11:15.760 --> 0:11:19.320 We're answering questions about the moon, and so far we've 0:11:19.400 --> 0:11:21.599 talked about where the moon came from four and a 0:11:21.640 --> 0:11:25.520 half billion years ago and how scientists figured out what happened. 0:11:26.200 --> 0:11:28.720 Now we're going to answer another big question about the moon, 0:11:28.960 --> 0:11:32.400 which is why is the Moon always facing us the 0:11:32.480 --> 0:11:35.480 same way? If you think about it, the Earth is 0:11:35.520 --> 0:11:38.400 going around the Sun, but the Earth doesn't always face 0:11:38.480 --> 0:11:41.200 the same way to the Sun. If you were standing 0:11:41.200 --> 0:11:43.680 on the surface of the Sun, the Earth would look 0:11:43.720 --> 0:11:46.400 like it's spinning and it would look different every time 0:11:46.640 --> 0:11:50.040 you see it. But you can't say that about the Moon. 0:11:51.280 --> 0:11:54.199 The features of the Moon always look the same to us. 0:11:54.720 --> 0:11:56.920 The only people in history that have gotten in a 0:11:56.960 --> 0:12:00.200 different view of the Moon are the Apollo astronauts that 0:12:00.320 --> 0:12:04.079 went there back in the nineteen sixties. Well, the reason 0:12:04.280 --> 0:12:06.720 that the Moon always looks the same to us, according 0:12:06.720 --> 0:12:09.400 to Professor Matt Ziegler, has to do with the fact 0:12:09.480 --> 0:12:15.559 that the Moon isn't round. Okay, next question, Matt, why 0:12:15.679 --> 0:12:18.400 is the Moon always facing the same way to us? 0:12:18.720 --> 0:12:22.360 Okay, So the moon is what we call tidally locked 0:12:23.040 --> 0:12:26.200 which essentially means one side is always facing us. 0:12:26.280 --> 0:12:29.640 Right. Is that another characteristic of science. 0:12:30.960 --> 0:12:33.200 If you don't know, we give it a fancy name 0:12:33.280 --> 0:12:38.240 and basically says this is all we know about it. Yeah. 0:12:38.280 --> 0:12:40.600 So a lot of moons in the Solar System are 0:12:40.640 --> 0:12:42.040 also tidally. 0:12:41.600 --> 0:12:43.640 Locked, not just our moon. 0:12:43.760 --> 0:12:47.760 Like Jupiter's moons gets large. Four moons are all tidally locked. 0:12:48.000 --> 0:12:51.880 So one face of Io is always facing Jupiter, one 0:12:51.920 --> 0:12:54.120 face of Europa is always facing Jupiter. 0:12:54.360 --> 0:12:57.320 Whow, we're not alone. Our moon is not the only one. 0:13:00.040 --> 0:13:04.280 The moon is what scientists call tidally locked, which basically 0:13:04.320 --> 0:13:08.719 means it's always facing us the same way. But there 0:13:08.840 --> 0:13:11.480 is a reason why this happens, and it has to 0:13:11.520 --> 0:13:14.960 do with how gooey the Earth and the Moon are. 0:13:16.320 --> 0:13:21.120 This happens essentially because of how gooey an object is. 0:13:21.600 --> 0:13:22.040 Uh huh. 0:13:22.080 --> 0:13:25.800 So if something's spinning and it's gooey inside, it can 0:13:25.840 --> 0:13:27.000 dissipate energy. 0:13:27.160 --> 0:13:30.200 Okay, meaning like if you were spinning a water balloon. 0:13:30.640 --> 0:13:34.040 Yeah. Or a good analogy is if you're spinning a 0:13:34.400 --> 0:13:38.000 hard boiled egg versus a normal egg. Right, the hard 0:13:38.040 --> 0:13:40.480 boiled egg will spin and spin and spin, right, but 0:13:40.520 --> 0:13:43.640 the non heart boiled egg will slow itself down pretty 0:13:43.679 --> 0:13:47.559 quickly because that ah, yeah, that goo inside is kind 0:13:47.559 --> 0:13:50.679 of churning around and dissipating energy of that spin. 0:13:51.040 --> 0:13:53.040 I see, if I spin a raw egg in space, 0:13:53.280 --> 0:13:57.440 it'll eventually slow down because the liquid inside is losing energy. 0:13:57.600 --> 0:14:01.520 Yeah, And so something akin to this happens inside of 0:14:01.559 --> 0:14:04.520 a body like the Moon that initially early on at 0:14:04.559 --> 0:14:07.880 least had a large liquid inside of it, right. 0:14:07.880 --> 0:14:11.280 Oh. It initially the Moon was gooey, oh yeah, because 0:14:11.280 --> 0:14:14.320 it was formed from the giant impact right, which was 0:14:14.720 --> 0:14:19.000 really hot and made a lot of things melt. What 0:14:19.120 --> 0:14:21.960 doctor Ziegler is saying is that when the Moon formed, 0:14:22.120 --> 0:14:25.480 it was probably spinning really fast, but the inside of 0:14:25.480 --> 0:14:29.720 it was gooey. It was melted rock or lava. It 0:14:29.800 --> 0:14:32.520 was still hot from one the huge collision that formed 0:14:32.520 --> 0:14:36.160 the Moon happened, and that melted inside made the Moon 0:14:36.280 --> 0:14:37.200 stop spinning. 0:14:37.920 --> 0:14:38.640 It's sort of like. 0:14:38.600 --> 0:14:41.320 If you take a regular plastic water bottle and you 0:14:41.400 --> 0:14:43.320 try to toss it up into the air so that 0:14:43.400 --> 0:14:47.200 it spins, it'll eventually stop spinning in mid air, and 0:14:47.240 --> 0:14:49.040 that's because the water inside. 0:14:48.720 --> 0:14:50.120 Of it slashes around. 0:14:50.880 --> 0:14:54.200 Well, the same thing happened to the Moon, and actually 0:14:54.400 --> 0:14:56.720 it's also happening to the Earth. 0:14:57.920 --> 0:15:00.520 And the Moon is doing this today to the Earth. Actually, 0:15:01.400 --> 0:15:04.880 and so the Earth is actually slowing down. Right, Our 0:15:04.960 --> 0:15:07.920 day is twenty four hours now. It used to be 0:15:08.040 --> 0:15:11.120 twenty two hours, and earlier on in the Earth's history 0:15:11.200 --> 0:15:15.000 it was as short as four hours. So we think 0:15:15.040 --> 0:15:18.480 when the Earth and Moon formed that the Earth day 0:15:18.600 --> 0:15:19.880 was about four hours long. 0:15:20.280 --> 0:15:22.840 Really, yeah, we were spinning that fast. 0:15:23.080 --> 0:15:26.360 Yeah, and then the Moon has caused us to slow 0:15:26.360 --> 0:15:28.920 down that we're now at twenty four hours a day. 0:15:29.320 --> 0:15:32.680 What maybe in a billion years will be at twenty 0:15:32.720 --> 0:15:34.920 five hours a day or something like that. Right. 0:15:35.080 --> 0:15:38.640 Oh, so the reason the day feels this long is because. 0:15:38.400 --> 0:15:38.880 Of the moon. 0:15:39.280 --> 0:15:40.520 Yeah, it's the moon's fault. 0:15:40.880 --> 0:15:43.040 You had a long day, Blame the moon. Howl of 0:15:43.080 --> 0:15:43.400 the moon. 0:15:43.720 --> 0:15:46.640 Yeah, but if your day was too short, if it 0:15:46.800 --> 0:15:48.920 went by too fast, then think the moon. 0:15:49.000 --> 0:15:50.360 Right, Oh yeah, that's right, that's right. 0:15:50.440 --> 0:15:53.200 So the same way that the Earth day is slowly 0:15:53.200 --> 0:15:56.600 getting longer because the Earth is slowing its spin, the 0:15:56.600 --> 0:15:59.440 Moon went through something similar. It's just because the Moon 0:15:59.520 --> 0:16:03.000 is a lot smaller, it happened a lot faster. Basically. 0:16:03.160 --> 0:16:06.840 Okay, maybe take me back, So we had this big crash, 0:16:07.040 --> 0:16:09.320 A lot of stuff went out there into space eventually 0:16:09.320 --> 0:16:12.760 formed the moon. The moon had a squishy inside, meaning 0:16:12.800 --> 0:16:14.359 like it was lava inside. 0:16:14.000 --> 0:16:17.440 Right basically, right, Yeah, basically it's magma if it's not erupted. 0:16:19.000 --> 0:16:21.920 Not the whole other episode. It was magma or lava 0:16:22.360 --> 0:16:25.280 melted rock. It was melted rock, and it was spinning 0:16:25.440 --> 0:16:26.120 super fast. 0:16:26.400 --> 0:16:26.720 Yeah. 0:16:26.760 --> 0:16:29.400 So we had a fast spinning Earth and a fast 0:16:29.400 --> 0:16:33.240 spinning Moon, and basically them tugging on each other slowed 0:16:33.240 --> 0:16:35.800 each other down. Okay, So if I was a live 0:16:35.920 --> 0:16:38.360 bike there and on Earth, I would die because I 0:16:38.360 --> 0:16:41.360 couldn't breathe and standing on lava. But if I could 0:16:41.360 --> 0:16:44.240 somehow be there, my day would be four hours long, 0:16:44.600 --> 0:16:47.560 and I would see the moon like basically spinning in place. 0:16:47.800 --> 0:16:50.040 The Moon would look different every time I looked at it. Yeah, 0:16:50.080 --> 0:16:52.840 you would see the far side of the moon back then. 0:16:53.160 --> 0:16:56.840 Oh okay, And over time we slowed down and the 0:16:56.880 --> 0:17:00.119 moon slowed down to the point where now it's always 0:17:00.160 --> 0:17:02.960 looking at us the same way. Yes, So is it 0:17:03.160 --> 0:17:05.679 just luck that we just happened to be alive at 0:17:05.680 --> 0:17:07.640 a time when it's spinning. It just the right time 0:17:07.640 --> 0:17:09.720 for it to be always looking at it, or is 0:17:09.760 --> 0:17:10.520 it stuck there? 0:17:10.960 --> 0:17:13.640 I wouldn't say it's that lucky, because we think it's 0:17:13.760 --> 0:17:17.840 stuck very quickly, like in potentially a few thousand years 0:17:17.880 --> 0:17:20.919 to less than a million years, Like the moon slowed 0:17:20.960 --> 0:17:24.840 itself down very quickly. So the moon'spent tidally locked for 0:17:24.960 --> 0:17:28.920 most of Earth's history, really, and then it got stuck there. Yeah, 0:17:28.960 --> 0:17:32.320 and then it's been stuck there. And it's a little 0:17:32.440 --> 0:17:36.240 arbitrary which side ended up stuck facing the Earth. And 0:17:36.280 --> 0:17:39.240 that's still a debate of why the near side of 0:17:39.280 --> 0:17:40.480 the Moon is the near side. 0:17:41.520 --> 0:17:43.800 Okay, you might be wondering, if the Moon went from 0:17:43.840 --> 0:17:47.639 spinning really fast to slowing down, why did it stop. 0:17:48.359 --> 0:17:50.840 It's still going around to Earth, so why didn't the 0:17:50.880 --> 0:17:55.359 Moon suddenly start spinning in place the other way? Well, 0:17:55.359 --> 0:17:57.840 according to doctor Siegler, it all has to do with 0:17:57.920 --> 0:17:59.639 the shape of the moon. 0:18:00.960 --> 0:18:03.840 The Moon isn't a perfect sphere. It's kind of egg 0:18:03.920 --> 0:18:07.000 shaped itself or what rugby ball shaped or whatever you 0:18:07.080 --> 0:18:09.280 want to call it. Yeah, just slightly. 0:18:09.880 --> 0:18:13.040 Yes, the Moon is not perfectly round. You might have 0:18:13.119 --> 0:18:16.400 heard that the Earth is not perfectly round either. It's 0:18:16.440 --> 0:18:19.520 a little wider around the middle or the equator. That's 0:18:19.600 --> 0:18:23.440 because the Earth is spinning, and so it bulges out, but. 0:18:23.400 --> 0:18:24.520 The Moon isn't round. 0:18:24.680 --> 0:18:28.399 In a different way and for a different reason, the 0:18:28.480 --> 0:18:32.400 Moon doesn't bulge out, it's actually stretched out. It looks 0:18:32.400 --> 0:18:35.880 slightly closer to a rugby ball or an American football 0:18:35.880 --> 0:18:39.359 ball with one of the pointy ends pointing at the Earth. 0:18:39.840 --> 0:18:42.480 And the reason it's that shape isn't because it's spinning, 0:18:42.880 --> 0:18:46.080 but because the Earth is pulling on it. As the 0:18:46.119 --> 0:18:49.200 Moon goes in orbit around the Earth, the Earth's gravity 0:18:49.359 --> 0:18:51.560 pulls on the Moon to keep it in that orbit, 0:18:51.920 --> 0:18:56.480 and that causes the Moon to get stretched. And I 0:18:56.480 --> 0:18:59.600 think I came up with a good analogy for tidal logging, 0:18:59.720 --> 0:19:01.240 which is that sort of like if you're in a 0:19:01.280 --> 0:19:04.440 merry go round and someone's at the edge and they're 0:19:04.560 --> 0:19:07.439 about to fall off, like you grabbed their hand to 0:19:07.520 --> 0:19:10.119 keep them in the merry go round, and so the 0:19:10.160 --> 0:19:13.000 centropgal force is pulling them out, but I'm holding their 0:19:13.040 --> 0:19:17.240 hand pulling them in, and so that causes them to stretch, right. 0:19:17.760 --> 0:19:20.679 Okay, Yeah, that would be a good description of it. 0:19:20.800 --> 0:19:23.560 Yeah, okay, And so that's what causes the Moon to 0:19:23.760 --> 0:19:25.800 look sort of like a football shape pointing at us. 0:19:26.160 --> 0:19:29.439 Yeah, and at some point in the Moon's history it 0:19:29.520 --> 0:19:33.280 became solid enough, it cooled off enough that it froze 0:19:33.320 --> 0:19:35.679 in a football shape at that time. 0:19:36.880 --> 0:19:40.679 Okay, so here's what scientists think happened. There was a 0:19:40.720 --> 0:19:43.879 pre Earth planet somewhere close to our current orbit. He 0:19:44.000 --> 0:19:46.639 got smashed by another planet about the size of Mars. 0:19:47.520 --> 0:19:50.000 Some of the debris stayed in place and became the Earth, 0:19:50.640 --> 0:19:53.119 and some of the debris floated out in space and 0:19:53.200 --> 0:19:57.040 became the Moon. This new Moon was an orbit around 0:19:57.080 --> 0:19:59.720 the new Earth, but it was gooey and melted on 0:19:59.760 --> 0:20:02.960 the inside. That made it stop spinning in place. And 0:20:03.119 --> 0:20:05.600 because it was being pulled around in an orbit around 0:20:05.600 --> 0:20:08.400 the Earth, it stretched out a little to be closer 0:20:08.440 --> 0:20:11.320 to the shape of a football pointed back at the Earth. 0:20:11.800 --> 0:20:14.600 Then it cooled off and it got stuck in that shape. 0:20:15.040 --> 0:20:17.280 And once it got stuck in that shape, it became 0:20:17.359 --> 0:20:21.040 tidally locked, with one end of the football always pointing. 0:20:20.920 --> 0:20:21.520 At the Earth. 0:20:22.960 --> 0:20:24.720 Wait, wait, wait, wait, I think what you're saying is 0:20:24.760 --> 0:20:27.199 that just because of the particular history of when the 0:20:27.240 --> 0:20:30.600 Moon cooled is the reason we're always seeing the same side. 0:20:30.640 --> 0:20:34.560 Because if it had stay squisher longer. Maybe the moon 0:20:34.560 --> 0:20:36.600 would be rounder now, less football. 0:20:36.240 --> 0:20:39.120 Shape, maybe, but I think it would still become tidally 0:20:39.160 --> 0:20:40.119 locked eventually. 0:20:40.280 --> 0:20:41.800 Yeah. Okay, that's good. 0:20:42.000 --> 0:20:44.119