WEBVTT - Does the Moon have an atmosphere? 0:00:08.440 --> 0:00:11.600 A Kelly, how was your family trip? Oh? It was 0:00:11.680 --> 0:00:13.920 so much fun. Did you guys get to break out 0:00:13.920 --> 0:00:17.439 of your usual routines experience something different? Yeah, And something 0:00:17.480 --> 0:00:20.400 that was unusual for our kids was eating at restaurants. 0:00:20.800 --> 0:00:22.800 We don't do a lot of that when we're at home, 0:00:22.880 --> 0:00:24.040 and you know, we didn't do a lot of it 0:00:24.040 --> 0:00:26.840 because of COVID and stuff. So that was new. And though, 0:00:26.880 --> 0:00:29.120 what is it that your kids like about eating out 0:00:29.160 --> 0:00:32.200 at restaurants? Aren't you guys like super good cooks at home? Well, 0:00:32.479 --> 0:00:34.680 we keep me out of the kitchen for everyone's sake, 0:00:34.760 --> 0:00:37.120 but that is a really good cook, so that's good. 0:00:37.560 --> 0:00:39.720 But I think for the kids, they mostly like the 0:00:39.760 --> 0:00:43.400 novelty of it, you know, the atmosphere. M Well, that's exciting, 0:00:43.400 --> 0:00:45.680 but it doesn't actually bode very well for them as 0:00:45.840 --> 0:00:49.680 future space colonists. No, I'm not following. What do you mean, Well, 0:00:49.720 --> 0:01:10.840 I hear that restaurants on the moon have no atmosphere. Oh. Hi, 0:01:11.040 --> 0:01:14.399 I'm Daniel. I'm a particle physicist and a professor at 0:01:14.480 --> 0:01:17.240 U C Irvine, and I'm always in the mood for 0:01:17.280 --> 0:01:20.840 a good space pun. I'm Kelly Weener Smith. I'm an 0:01:20.840 --> 0:01:24.040 adjunct assistant professor at Grace University, and I am also 0:01:24.080 --> 0:01:26.800 a fan of the puns, especially the moon based ones. 0:01:27.000 --> 0:01:29.399 There's a lot of inappropriate moon based puns that we 0:01:29.400 --> 0:01:31.080 can make right now. Yeah, sure, no, you and I 0:01:31.160 --> 0:01:32.760 are pretty good at that. But what we're going to 0:01:32.880 --> 0:01:35.440 keep it clean. We are definitely gonna keep it clean 0:01:35.560 --> 0:01:39.440 as we examine the deep dark mysteries of the universe. 0:01:39.800 --> 0:01:43.520 And welcome to the podcast. Daniel and Jorge explain the 0:01:43.640 --> 0:01:47.560 universe in which we do exactly that, ask the biggest, darkest, 0:01:47.560 --> 0:01:50.760 deepest questions about everything that's out there in the universe. 0:01:50.880 --> 0:01:53.000 We don't want to sweep anything under the rug. We 0:01:53.040 --> 0:01:55.960 want to expose it all to the blinding glare of 0:01:56.120 --> 0:01:59.280 sunlight and make it all makes sense to you. My 0:01:59.480 --> 0:02:02.520 usual host, Orgy can't be here today, so we are 0:02:02.640 --> 0:02:05.560 delighted to have one of our regular co hosts, Kelly. Kelly. 0:02:05.560 --> 0:02:08.240 Thank you very much for joining us today. I'm delighted 0:02:08.280 --> 0:02:10.400 to be back, Okelly. When you're on the podcast, we're 0:02:10.440 --> 0:02:13.520 often talking about space and about the wonders of the 0:02:13.639 --> 0:02:17.240 night sky, putting people out there mentally sort of at night, 0:02:17.400 --> 0:02:20.560 staring up in the stars, being amazed at everything that 0:02:20.600 --> 0:02:23.080 we are seeing that's right, and then you turn it 0:02:23.120 --> 0:02:25.760 into something about how we're all going to die. But yes, 0:02:25.960 --> 0:02:28.680 we are usually looking up at the night sky and 0:02:28.720 --> 0:02:31.160 having a sense of all about it all because one 0:02:31.200 --> 0:02:32.960 of the things that I love about science is that 0:02:33.000 --> 0:02:35.760 it lifts us up away from our everyday lives. It 0:02:35.800 --> 0:02:40.080 forces us to turn our eyes skywords and think about 0:02:40.080 --> 0:02:43.360 what's out there in the universe. Usually that's something we 0:02:43.520 --> 0:02:46.160 do at night because during the day the sun is 0:02:46.200 --> 0:02:49.639 so bright it keeps us from seeing everything that's out there. 0:02:49.639 --> 0:02:52.320 That makes us wonder, that makes us as deep questions 0:02:52.360 --> 0:02:55.040 about the very nature of the universe. But you know, 0:02:55.200 --> 0:02:58.440 everything that's out there is also out there during the daytime, 0:02:58.680 --> 0:03:00.320 and I remember that blew my mind when I was 0:03:00.360 --> 0:03:02.200 a kid and I first learned that. But yeah, it's 0:03:02.240 --> 0:03:04.120 all still out there, and sometimes you can see the 0:03:04.160 --> 0:03:06.799 moon during the day. It always feels sort of inappropriate, though. 0:03:06.840 --> 0:03:08.760 When you see the moon during the day, it feels 0:03:08.800 --> 0:03:11.560 like you know you've caught somebody, like they're not supposed 0:03:11.560 --> 0:03:13.480 to be there, Like they're tiptoeing to the fridge in 0:03:13.520 --> 0:03:15.519 the middle of the night and you spotted them, or 0:03:15.560 --> 0:03:17.560 like they don't know their place you know, like moon, 0:03:18.040 --> 0:03:21.280 your place is at night, you're stepping on the Sun's toes, 0:03:21.600 --> 0:03:24.160 and you know, it's not only the nighttime sky. That's 0:03:24.200 --> 0:03:27.400 really fascinating, that's really amazing. That has a lot of 0:03:27.400 --> 0:03:29.280 physics in it is what we can learn about the 0:03:29.360 --> 0:03:31.799 nature of the universe and what's out there just by 0:03:31.840 --> 0:03:34.880 looking up at the daytime sky. Oh well, what can 0:03:34.920 --> 0:03:37.600 we learn? Well, one common question from kids, of course, 0:03:37.760 --> 0:03:41.000 is why is the sky blue? You know, if the 0:03:41.040 --> 0:03:44.320 Sun is just shining through space at us, what is 0:03:44.360 --> 0:03:47.480 it that makes the sky blue? And so we've talked 0:03:47.480 --> 0:03:50.000 about on the podcast a few times. It's a fascinating 0:03:50.040 --> 0:03:53.760 interaction between the Sun's gas and the atmospheric gases. The 0:03:53.880 --> 0:03:56.400 light that comes directly from the Sun is white light. 0:03:56.440 --> 0:03:58.760 If you were out in space looking at the Sun, 0:03:58.800 --> 0:04:01.480 it would mostly look why it maybe a little bit yellow, 0:04:01.560 --> 0:04:04.800 but not all of that light passes through our atmosphere 0:04:04.880 --> 0:04:08.040 equally well, when light hits gases in the atmosphere tends 0:04:08.080 --> 0:04:10.920 to scatter, and it scatters more for the very high 0:04:11.000 --> 0:04:13.720 frequency light, the blue or light, and that might make 0:04:13.760 --> 0:04:15.960 you think, oh, well, we should see everything, but the 0:04:15.960 --> 0:04:18.800 blue light like the blue should get reflected back into space, 0:04:19.200 --> 0:04:21.359 and it does get reflected back into space, but it 0:04:21.480 --> 0:04:24.520 also gets reflected down to the ground. So when you're 0:04:24.520 --> 0:04:26.400 standing on the surface of the Earth and you're looking 0:04:26.560 --> 0:04:29.560 up at the sky, you're seeing light that doesn't come 0:04:29.600 --> 0:04:31.520 directly from the sun and sort of hid an atom 0:04:31.560 --> 0:04:34.760 and bounce down to your eyeballs. So the reason that 0:04:34.839 --> 0:04:38.400 our daytime sky is blue is because those gases bounce 0:04:38.480 --> 0:04:41.160 the blue light down to our eyeballs. And can we 0:04:41.279 --> 0:04:43.520 use this to figure out what the atmospheres of other 0:04:43.600 --> 0:04:45.839 planets are made up just by looking at the color 0:04:45.920 --> 0:04:47.920 that we see when we shine a telescope about them. 0:04:48.120 --> 0:04:51.440 We totally can and we do exactly that. When exo 0:04:51.520 --> 0:04:54.960 planets pass in front of their stars, the light goes 0:04:55.000 --> 0:04:57.479 through their atmosphere and some of it bounces off and 0:04:57.520 --> 0:04:59.880 some of it passes through, and some of it is absorbed. 0:05:00.040 --> 0:05:03.080 It's a great way to understand what's in those exo 0:05:03.120 --> 0:05:05.760 planet atmospheres. And so it's sort of like X raying 0:05:05.800 --> 0:05:08.479 the atmosphere. Passing light through it is a great way 0:05:08.480 --> 0:05:10.839 to figure out like what's there as a glow, what 0:05:10.880 --> 0:05:13.320 does it absorbed, what does it reflect? I love the 0:05:13.360 --> 0:05:17.039 idea of seeing a sunrise on an exo planet and 0:05:17.200 --> 0:05:20.240 using that to figure out what's in the sky. And 0:05:20.240 --> 0:05:23.240 you know, sunrise is on different planets all look very 0:05:23.320 --> 0:05:27.000 different because the different planets have different atmospheres. And so 0:05:27.120 --> 0:05:30.160 when I am looking up in the night sky recently, 0:05:30.160 --> 0:05:33.080 I've been seeing a big red dot. Is that Mars 0:05:33.200 --> 0:05:35.520 or is it Venus? And also when I see those colors, 0:05:35.560 --> 0:05:37.599 is that the atmosphere I'm seeing or is that something 0:05:37.600 --> 0:05:39.760 else that I'm seeing entirely, So, if you look up 0:05:39.760 --> 0:05:41.640 in the night sky and you're seeing a red dot, 0:05:41.720 --> 0:05:44.680 that's probably Mars, and Mars is definitely red. If you 0:05:44.680 --> 0:05:47.040 were in a satellite orbiting Mars looking down, it would 0:05:47.040 --> 0:05:49.760 look red to your eyeballs. It's not just like a 0:05:49.760 --> 0:05:52.560 false color thing from satellite imagery that we take and 0:05:52.560 --> 0:05:55.720 then change the way like James web Space Telescope images 0:05:55.760 --> 0:05:58.479 are all false color. If your eyeballs were there where 0:05:58.560 --> 0:06:01.679 James Webb Space Telescope is, you wouldn't be seeing those 0:06:01.720 --> 0:06:05.479 images because those images are all infrared. They're all too deep, 0:06:05.560 --> 0:06:08.560 too long wavelengths for your eyeball to even register. But 0:06:08.680 --> 0:06:11.400 if your eyeballs were orbiting Mars, hopefully with the rest 0:06:11.400 --> 0:06:13.760 of your body, you would see it as red. And 0:06:13.800 --> 0:06:16.160 the reason there is not actually the atmosphere, because Mars 0:06:16.200 --> 0:06:20.520 has almost no atmosphere. It's very very thin atmosphere. It's 0:06:20.560 --> 0:06:23.920 because the surface of Mars itself is mostly red due 0:06:23.920 --> 0:06:26.440 to the iron and the oxidization of it, so it's 0:06:26.480 --> 0:06:29.280 covered in this red dust. And it's sort of amazing 0:06:29.320 --> 0:06:32.080 that you can see it from the Earth's surface, right, 0:06:32.120 --> 0:06:34.599 that this thing is so red that you can see 0:06:34.600 --> 0:06:37.679 it from your backyard. That's incredible. And then the fact 0:06:37.680 --> 0:06:40.599 that you so you said that it has very little atmosphere, 0:06:40.680 --> 0:06:43.200 that makes me I have a pop culture question to 0:06:43.240 --> 0:06:46.480 ask you. Someone told me that one of the things 0:06:46.480 --> 0:06:48.520 they didn't like about the Martian was that with a 0:06:48.640 --> 0:06:52.040 low atmosphere, if you had a big dust storm, it 0:06:52.040 --> 0:06:55.000 wouldn't be strong enough to like knock over a rocket, 0:06:55.040 --> 0:06:59.400 because low atmosphere means like far fewer molecules pushing against 0:06:59.480 --> 0:07:01.919 things even in a big windstorm. So is that not 0:07:02.040 --> 0:07:09.120 accurate about the Martian? This is this is absolutely vital stuff. Yeah, 0:07:09.160 --> 0:07:11.400 it's definitely true that the atmosphere on Mars is very 0:07:11.520 --> 0:07:14.680 very low, like less than one percent of the Earth's atmosphere, 0:07:14.760 --> 0:07:17.760 and that means that the wind don't apply as much pressure, 0:07:18.040 --> 0:07:20.800 so whin did the same velocity. For example, there just 0:07:20.840 --> 0:07:23.600 aren't as many molecules bouncing off of you. But the 0:07:23.680 --> 0:07:26.680 velocity can get very high, and there's also a lot 0:07:26.720 --> 0:07:29.360 of dust in the atmosphere on Mars. You definitely do 0:07:29.480 --> 0:07:32.720 have to worry about storms. Very high velocity windstorm on 0:07:32.880 --> 0:07:35.160 Mars can do a lot of damage because all the 0:07:35.240 --> 0:07:38.600 dust particles you can basically sand blast you. Right, I 0:07:38.600 --> 0:07:40.600 don't know if the velocity is actually get high enough 0:07:40.600 --> 0:07:43.000 to knock things over. We'll have to get Andy Weir 0:07:43.080 --> 0:07:45.160 on the podcast and ask him that question. Well, you know, 0:07:45.240 --> 0:07:47.240 I loved that book in that movie, and you're making 0:07:47.240 --> 0:07:50.800 me feel better knowing that maybe that opening scene was feasible, 0:07:50.800 --> 0:07:52.840 because I would hate to think it wasn't. But okay, 0:07:52.840 --> 0:07:55.200 all right, let's let's get back to the important stuff. 0:07:55.280 --> 0:07:57.280 But it does bring us to a really fascinating fact 0:07:57.320 --> 0:07:59.640 about Mars, which is, if you're standing on the surface 0:07:59.640 --> 0:08:01.720 of Mars Mars and you look down, of course it 0:08:01.720 --> 0:08:04.720 looks red. But also if you look up, it looks red. 0:08:05.160 --> 0:08:08.160 That is, the sky on Mars doesn't look blue like 0:08:08.240 --> 0:08:11.560 it does on Earth. That's because Earth has this atmosphere 0:08:11.600 --> 0:08:14.080 which scatters the blue light down to your eyeballs. But 0:08:14.200 --> 0:08:16.920 Mars doesn't. This atmosphere is so thin that it doesn't 0:08:16.960 --> 0:08:19.400 effectively scatter that light. So then why is it red 0:08:19.440 --> 0:08:22.640 instead of like white from the sun. It's because of 0:08:22.640 --> 0:08:25.640 all of the dust. Right, Mars doesn't have much atmosphere, 0:08:25.640 --> 0:08:28.200 but the dust is up there, and that dust tends 0:08:28.240 --> 0:08:31.080 to absorb blue light. That's why it looks red. Remember, 0:08:31.160 --> 0:08:34.960 things that look a certain color, they're reflecting that color 0:08:35.120 --> 0:08:38.200 and they're absorbing everything else. So things that are yellow 0:08:38.240 --> 0:08:41.480 are things that reflect yellow because the yellow makes it 0:08:41.520 --> 0:08:44.520 to your eyeball and they absorb everything else. So it 0:08:44.559 --> 0:08:47.560 sounds weird to say that red dust absorbs blue light. 0:08:47.600 --> 0:08:50.360 You might think that makes it blue, right, but actually 0:08:50.400 --> 0:08:52.800 that's what makes it red. So when you look up 0:08:52.800 --> 0:08:55.600 in the sky during the daytime on Mars, you're seeing 0:08:55.640 --> 0:08:58.600 the red light reflected from that dust. I didn't realize 0:08:58.640 --> 0:09:00.920 that the dust never settled enough for the sky to 0:09:01.000 --> 0:09:03.720 not be red. That's incredible. It is incredible, And if 0:09:03.760 --> 0:09:07.120 you're lucky enough to observe a sunset on Mars, then 0:09:07.160 --> 0:09:11.000 you'll see an amazing blue sunset. Right. It's like totally 0:09:11.080 --> 0:09:14.720 reversed from Earth because this dust scatters the red light, 0:09:15.040 --> 0:09:17.960 and so if you're looking directly at the sun sort of, 0:09:18.080 --> 0:09:20.280 then most of the red light has been scattered away 0:09:20.280 --> 0:09:22.199 by the dust, and so the blue light is all 0:09:22.240 --> 0:09:25.600 that survives. So you see a blue sunset on Mars 0:09:25.679 --> 0:09:29.280 on a red sky. Oh, that's incredible. I hope within 0:09:29.320 --> 0:09:31.559 my lifetime we get photos of that taken by an 0:09:31.559 --> 0:09:36.240 astronaut that landed on the Martian surface. Blue sunset. Selfie, 0:09:36.720 --> 0:09:39.840 what an Instagram pick that will be in. And that 0:09:39.920 --> 0:09:41.760 makes you wonder, like what it would be like to 0:09:41.760 --> 0:09:44.400 be on other planets. Right, If the atmosphere of the 0:09:44.440 --> 0:09:47.400 planet is what determines what it looks like to be 0:09:47.480 --> 0:09:50.280 on the planet, the color of the daytime sky and 0:09:50.360 --> 0:09:53.360 atmospheres can be like, you know, anything that opens the 0:09:53.400 --> 0:09:57.160 door to like having all sorts of crazy daytime colors. 0:09:57.160 --> 0:09:58.959 You know, can you have like a yellow sky or 0:09:59.000 --> 0:10:03.320 a purple sky or something with crazy stripes from atmospheric bands? Right, 0:10:03.559 --> 0:10:05.360 I haven't yet seen that in a science fiction movie. 0:10:05.360 --> 0:10:07.480 You know, somebody living on Jupiter with the sky has 0:10:07.520 --> 0:10:11.040 like stripes of color. That would be really awesome. And 0:10:11.040 --> 0:10:13.440 there aren't many places in the solar system where we 0:10:13.520 --> 0:10:16.920 have had people take pictures, right. One of those, of course, 0:10:17.120 --> 0:10:19.920 is the moon. It's something that's striking about all of 0:10:19.960 --> 0:10:22.880 the pictures from the moon, is that the sky the 0:10:22.920 --> 0:10:26.280 backdrop or if you look above the moon, it's always black. 0:10:26.600 --> 0:10:29.480 And why is that right? Because you associated black with 0:10:29.520 --> 0:10:31.920 the color of the night sky, right, But even during 0:10:31.960 --> 0:10:34.880 the moon sort of daytime, when the sun is shining 0:10:35.000 --> 0:10:38.360 right at you, there's nothing there to scatter the light. 0:10:38.559 --> 0:10:40.560 So from the point of view of somebody on the moon, 0:10:40.720 --> 0:10:44.240 the sun is just another star. So it's sort of 0:10:44.280 --> 0:10:48.440 like a perpetual night sky with one huge, very bright 0:10:48.520 --> 0:10:52.760 star in it half the time. Also not very invited. 0:10:54.480 --> 0:10:56.760 You wouldn't want to have a picnic under a black sky. 0:10:57.080 --> 0:10:59.240 I feel like the regular would get in my sandwich 0:10:59.240 --> 0:11:01.640 and was sort of mess up the overall feeling. So 0:11:01.679 --> 0:11:04.040 the reason the night sky in the Moon is black 0:11:04.240 --> 0:11:06.960 is because there isn't a strong enough atmosphere there on 0:11:07.000 --> 0:11:09.160 the Moon to scatter it to make it blue or 0:11:09.200 --> 0:11:11.760 purple or yellow at pink polka dots. But it does 0:11:11.920 --> 0:11:15.720 raise an interesting question and the question of today's episode, 0:11:15.760 --> 0:11:24.640 which is does the moon have an atmosphere? So this 0:11:24.720 --> 0:11:26.880 is a fun question because it lets us dig into 0:11:26.960 --> 0:11:30.280 definitions and quibble about what it means to have an 0:11:30.280 --> 0:11:35.080 atmosphere for quibbling. Sometimes it feels to me like a 0:11:35.080 --> 0:11:37.280 big part of science is just like arguing about what 0:11:37.320 --> 0:11:40.440 a definition is, you know, like is this really a mammal? 0:11:40.520 --> 0:11:42.400 I don't know what lays egg? What does that mean? 0:11:42.559 --> 0:11:45.839 Whereas really that interesting questions are like the questions behind that, 0:11:45.920 --> 0:11:49.360 you know, like why does something with hair lay eggs? Anyway, Yeah, 0:11:49.440 --> 0:11:51.120 that was one of the most surprising things when I 0:11:51.120 --> 0:11:53.560 started college, was like, wait a minute, we don't even 0:11:53.679 --> 0:11:57.280 know how to define a species really and yeah, and 0:11:57.480 --> 0:12:00.680 of course huge arguments over that, but know it's because 0:12:00.920 --> 0:12:03.360 nature doesn't fit in the categories that humans would like 0:12:03.400 --> 0:12:06.280 it to. Yeah, And sometimes those arguments are just a 0:12:06.320 --> 0:12:08.920 waste of time, people splitting hairs where there's nothing really 0:12:08.920 --> 0:12:12.040 to be learned. But sometimes it really is illuminating because 0:12:12.080 --> 0:12:15.319 we do try to describe the universe in terms of categories. 0:12:15.480 --> 0:12:18.600 These ways that we like to think about things are 0:12:18.640 --> 0:12:21.160 sort of our familiar basis, and in the end, that's 0:12:21.160 --> 0:12:24.560 what science is, is explaining everything we'd see in terms 0:12:24.600 --> 0:12:28.360 of things we understand. Physics is describing the unfamiliar in 0:12:28.480 --> 0:12:31.079 terms of the familiar. So the words we're using are 0:12:31.120 --> 0:12:33.160 sort of important. If we're going to communicate with each 0:12:33.200 --> 0:12:35.400 other about these ideas, we better at least know what 0:12:35.520 --> 0:12:37.719 the words mean. And I guess, to be fair, I'm 0:12:37.720 --> 0:12:40.760 thinking that I don't exactly know what an atmosphere starts 0:12:40.760 --> 0:12:42.840 and stops, because it seems like sort of a gradient, 0:12:43.080 --> 0:12:45.319 like is you know at what point do you call 0:12:45.360 --> 0:12:48.040 it an atmosphere versus something else? And so I'm not 0:12:48.080 --> 0:12:50.120 sure that I know the answer. So let's let's see 0:12:50.160 --> 0:12:53.400 what your listeners think. Great idea, And so as usual, 0:12:53.440 --> 0:12:55.840 I went out there into the internet to ask people 0:12:55.960 --> 0:12:59.040 if they thought that the moon had an atmosphere. If 0:12:59.120 --> 0:13:02.319 you like the artists made for future episodes of the podcast, 0:13:02.400 --> 0:13:05.080 please don't be shy. Right to me two questions at 0:13:05.240 --> 0:13:07.880 Daniel I and Jorge dot com, and I will set 0:13:07.920 --> 0:13:10.120 you up. Is free. It's fun. Your friends can hear 0:13:10.160 --> 0:13:13.640 your voice on the podcast. So before you hear these answers, 0:13:13.679 --> 0:13:17.280 think to yourself, do you think the moon has an atmosphere? 0:13:18.400 --> 0:13:20.800 Here's what people had to say. All right, so I 0:13:20.840 --> 0:13:23.200 don't think that our moon has an atmosphere at least 0:13:23.240 --> 0:13:26.840 anything substantial enough to call it an atmosphere. UM. I 0:13:26.840 --> 0:13:28.800 did have a physics professor my first year of college 0:13:28.840 --> 0:13:31.000 who claimed to have a plan to give the Moon 0:13:31.000 --> 0:13:34.360 atmosphere for two hundred years by basically creating an orbital 0:13:34.480 --> 0:13:38.240 cannon that could help a smaller Moon from either Jupiter Titan. 0:13:38.320 --> 0:13:40.160 I have like an escape glossy of seventeen miles an 0:13:40.160 --> 0:13:44.160 hour UH to slingshot that into ours vaporize and create 0:13:44.160 --> 0:13:46.880 an atmosphere. But it wasn't only for two years, so 0:13:47.000 --> 0:13:50.080 I can get implaced temporary and nothing substantial enough. I 0:13:50.120 --> 0:13:52.199 don't think the Moon has an atmosphere. I mean there 0:13:52.320 --> 0:13:55.840 might be some like low density hydrogen or something floating around, 0:13:55.960 --> 0:13:59.400 but not enough to call it an atmosphere. I think 0:14:00.080 --> 0:14:07.160 has some atmosphere UM only because I'm thinking that Moon 0:14:07.320 --> 0:14:11.560 has a weak magnetic field that might be able to 0:14:11.840 --> 0:14:17.680 contain some kind of atmosphere. There are so not what 0:14:17.960 --> 0:14:21.760 Earth has, but still something. UM. I would guess it 0:14:21.800 --> 0:14:25.040 probably does. I doubt it looks anything like ours does 0:14:25.080 --> 0:14:26.840 on Earth, but I would guess that if you're a 0:14:27.600 --> 0:14:30.240 body or an object in the sky, and you're large 0:14:30.320 --> 0:14:32.640 enough or dense enough that you probably attract some kind 0:14:32.640 --> 0:14:36.360 of atmosphere. The Moon doesn't have an atmosphere. I think 0:14:36.400 --> 0:14:42.440 it's because it's gravitational attraction is too weak to um 0:14:43.640 --> 0:14:46.360 sort of hold the guesses around it to form an atmosphere. 0:14:46.720 --> 0:14:48.360 So what do you think of these answers? Kelly? A 0:14:48.360 --> 0:14:50.600 lot of skepticism here, a lot of folks feeling like 0:14:50.640 --> 0:14:53.200 the Moon can't really have much of an atmosphere. Yeah, 0:14:53.440 --> 0:14:55.280 but a lot of critical thinking also, a lot of 0:14:55.280 --> 0:14:57.960 folks trying to think through like, well, you know, I 0:14:58.000 --> 0:15:00.320 think the moon has a weak magnetic field old, so 0:15:00.360 --> 0:15:04.000 that wouldn't contain it. And yeah, so lots of good 0:15:04.040 --> 0:15:07.000 thinking through the problem. Absolutely, And I love seeing people 0:15:07.000 --> 0:15:09.800 apply their knowledge of physics to this question to come 0:15:09.880 --> 0:15:12.200 up with an answer that they think makes sense, because 0:15:12.200 --> 0:15:14.240 if the answer is not the one that you expect, 0:15:14.280 --> 0:15:17.000 then there better to be an explanation for it. Right, That, 0:15:17.160 --> 0:15:20.280 in the end, is what physics is all about. That's right. 0:15:20.640 --> 0:15:24.400 So how about we start by talking about where atmosphere 0:15:24.400 --> 0:15:26.920 has come from? How do you get an atmosphere? Well, 0:15:26.960 --> 0:15:29.360 you go to Amazon dot com and you just type 0:15:29.360 --> 0:15:31.800 in whatever you'd like, and you know, they deliver it. 0:15:32.000 --> 0:15:34.960 I know so many space space element advocates who are 0:15:34.960 --> 0:15:36.480 going to be so excited to know it's going to 0:15:36.560 --> 0:15:39.880 be so easy on the Moon or Mars. It's surprising, Bezos, 0:15:39.920 --> 0:15:42.520 isn't saying more about this on Mars. Isn't the plans 0:15:42.640 --> 0:15:44.920 just like nuke the polar ice caps? Isn't that like 0:15:45.000 --> 0:15:47.640 step one in getting a Martian atmosphere? You know that 0:15:47.640 --> 0:15:50.800 that has been proposed, but I'm fairly certain the international 0:15:50.840 --> 0:15:53.760 community has mixed feelings about that proposal, so I'm not 0:15:53.840 --> 0:15:55.760 holding my breath. And also I think it makes it 0:15:55.840 --> 0:15:58.520 uninhabitable for quite a while. But you know, if we've 0:15:58.520 --> 0:16:00.840 got our great grandkids in mind, maybe it's maybe it's 0:16:00.840 --> 0:16:02.880 a good plan. Yeah, we have a whole episode on 0:16:03.120 --> 0:16:06.360 terra forming Mars and why that plan will not work. 0:16:06.520 --> 0:16:09.280 So we're lucky we have such a nice atmosphere here 0:16:09.320 --> 0:16:10.720 on Earth. And I think you're right. It's a good 0:16:10.720 --> 0:16:13.200 idea to think about why Earth has an atmosphere and 0:16:13.240 --> 0:16:16.480 why the Moon doesn't have at least the same atmosphere 0:16:16.560 --> 0:16:19.000 as we do. And the interesting thing is that the 0:16:19.040 --> 0:16:22.200 Earth sort of has had a few different atmospheres. The 0:16:22.240 --> 0:16:24.840 Earth got its first atmosphere when it was just forming. 0:16:24.880 --> 0:16:27.000 Remember that the whole Solar system just comes from a 0:16:27.040 --> 0:16:30.360 big cloud of gas and dust and rock and little 0:16:30.360 --> 0:16:33.440 bits from other solar systems and stars that died. Most 0:16:33.480 --> 0:16:36.200 of it's just hydrogen left over from the Big Bang. 0:16:36.360 --> 0:16:38.120 But you have this big cloud of gas and dust 0:16:38.200 --> 0:16:40.520 in space, you have some blobs in it that are 0:16:40.520 --> 0:16:43.280 a little denser than others, so they have stronger gravity. 0:16:43.480 --> 0:16:46.520 They are pulling everything together, and that's the formation of 0:16:46.560 --> 0:16:49.040 the Solar system. Of course, in the very center is 0:16:49.080 --> 0:16:51.520 the Sun, which gathers in most of the gas and 0:16:51.560 --> 0:16:54.400 the dust. But you also have other little blobs which 0:16:54.400 --> 0:16:57.320 eventually formed planets, and they try to gather as much 0:16:57.320 --> 0:16:59.880 stuff as they can before the Sun gobbles it all up. 0:17:00.000 --> 0:17:02.920 You know. It's funny my intuition, and this is why 0:17:02.920 --> 0:17:05.679 I didn't become a physicist. My intuition, Like, it feels 0:17:05.680 --> 0:17:09.240 to me like gases shouldn't get pulled in by gravity, 0:17:09.280 --> 0:17:12.280 but of course they are, and they should. But the 0:17:12.320 --> 0:17:15.919 idea that gravity is holding our atmosphere on, I don't know. 0:17:15.960 --> 0:17:17.760 It feels like the little molecule should be able to 0:17:17.800 --> 0:17:20.200 just pop out in escape. But I'm glad that I'm 0:17:20.200 --> 0:17:22.280 wrong about it. You're not actually wrong A lot of 0:17:22.320 --> 0:17:25.200 them do escape, and the Earth is constantly boiling off 0:17:25.280 --> 0:17:28.840 its atmosphere into space. It's a tenuous balance, right, The 0:17:28.880 --> 0:17:30.760 Earth is pulling on those little guys, but they are 0:17:30.800 --> 0:17:33.879 moving quickly, and the ones that have higher velocity and 0:17:34.040 --> 0:17:37.639 higher altitudes definitely do escape. And in the very early 0:17:37.720 --> 0:17:40.160 days of the Solar System, the Earth had an atmosphere 0:17:40.200 --> 0:17:43.560 which came from these primordial gases, the hydrogen helium that 0:17:43.640 --> 0:17:46.080 was just sort of like around, but it didn't last 0:17:46.119 --> 0:17:48.159 for very long. It's not a very good atmosphere for 0:17:48.200 --> 0:17:51.000 having an atmosphere, I guess you could say, because first 0:17:51.000 --> 0:17:52.800 of all, the Sun was gobbling up most of the 0:17:52.880 --> 0:17:55.560 hydrogen and the helium, and then once the Sun formed, 0:17:55.640 --> 0:17:58.639 it was producing a lot of radiation which stripped the 0:17:58.640 --> 0:18:02.119 inner planets of theirmosphere. So like solar wind and heat 0:18:02.400 --> 0:18:06.239 from the Sun basically blasted the Earth's atmosphere away. So 0:18:06.240 --> 0:18:09.160 it started off having a scoop of hygen and helium 0:18:09.160 --> 0:18:11.160 and stuff that could have made an atmosphere, but then 0:18:11.160 --> 0:18:14.439 it got blasted dry basically by the early Sun. So 0:18:14.680 --> 0:18:18.639 is solar wind well named? Is it like the sun 0:18:18.920 --> 0:18:22.320 is like and the stuff just sort of blows away? 0:18:22.480 --> 0:18:25.240 Or is it more like the photons that come out 0:18:25.280 --> 0:18:27.679 from the Sun. It's like a billiard table, and it 0:18:27.800 --> 0:18:30.159 like knocks the hydrogen in the helium out of our 0:18:30.200 --> 0:18:32.800 atmosphere when they like bounce into each other. I think 0:18:32.800 --> 0:18:36.960 it's pretty well named because it's not just photons. It's protons, 0:18:37.040 --> 0:18:40.000 it's electrons, it's actual particles. So if you think about 0:18:40.000 --> 0:18:43.480 wind on Earth, it's like high moving particles that carry 0:18:43.520 --> 0:18:46.000 momentum and it can push stuff over, and the solar 0:18:46.040 --> 0:18:49.000 wind is really the same thing. It's stuff, it's matter 0:18:49.080 --> 0:18:52.119 particles carrying momentum, and it could like push a solar sail, 0:18:52.480 --> 0:18:55.399 and it definitely blasts things off of the Moon and 0:18:55.560 --> 0:18:58.240 Mars and early Earth. Way to go, phus. This good 0:18:58.280 --> 0:19:01.000 job name in that thing. And that's one reason why 0:19:01.040 --> 0:19:03.679 you have, for example, rocky planets in the interior of 0:19:03.680 --> 0:19:06.000 the Solar system, because that's the kind of stuff the 0:19:06.040 --> 0:19:09.800 Sun couldn't blast off and like formed dense or blobs. 0:19:10.080 --> 0:19:11.919 And in the outer part of the Solar system you 0:19:11.960 --> 0:19:14.520 have the gas giants because they were far enough away 0:19:14.520 --> 0:19:16.560 from the Sun to get to gobble up some of 0:19:16.560 --> 0:19:19.120 their own gas and to hold onto it out there 0:19:19.119 --> 0:19:22.040 where the solar radiation is weaker, So we got amosphere 0:19:22.119 --> 0:19:24.480 very early on, and so did the Moon. As the 0:19:24.520 --> 0:19:28.119 moon form from whatever primordial blobs made it. It also 0:19:28.200 --> 0:19:31.280 must have had some helium and some hydrogen, but that 0:19:31.359 --> 0:19:34.240 also was blasted clean by the Sun. So we both 0:19:34.280 --> 0:19:37.520 started with an atmosphere and both lost our atmosphere very quickly, 0:19:37.640 --> 0:19:40.119 and we both both of them lost it entirely or 0:19:40.119 --> 0:19:42.840 did Earth retain some of it almost entirely, I mean 0:19:43.119 --> 0:19:45.880 never completely dry. There must have been a little bit 0:19:45.880 --> 0:19:48.399 of hydrogen floating around, but compared to the densities we 0:19:48.400 --> 0:19:51.800 have today basically zero. Okay, Well, before we get into 0:19:51.840 --> 0:20:08.080 what our second atmosphere was, like, let's take a break. Okay, 0:20:08.119 --> 0:20:12.639 So the first atmosphere we had and we lost, but 0:20:12.760 --> 0:20:15.240