1 00:00:20,280 --> 00:00:23,535 Jane: This is But Why: a Podcast for Curious Kids from Vermont 2 00:00:23,535 --> 00:00:27,705 Public. On this program, we take questions from curious kids just 3 00:00:27,705 --> 00:00:30,615 like you, and we find interesting people who can offer 4 00:00:30,615 --> 00:00:35,025 some answers. In this episode, we're going to look far, far 5 00:00:35,025 --> 00:00:40,005 beyond our field of vision and think about our solar system. 6 00:00:40,005 --> 00:00:43,485 There's so much out there to explore and learn more about, 7 00:00:43,485 --> 00:00:46,155 and scientists are still discovering new things all the 8 00:00:46,155 --> 00:00:51,450 time. So get ready for some virtual space exploration. While 9 00:00:51,450 --> 00:00:54,540 it might be more fun to actually be an astronaut who gets to 10 00:00:54,540 --> 00:00:59,130 explore space in person, this way we all get to participate. 11 00:00:59,130 --> 00:01:02,580 And actually, we're going to go farther out in the universe than 12 00:01:02,580 --> 00:01:08,220 any humans have ever been, so strap in. To orient ourselves, 13 00:01:08,220 --> 00:01:13,305 our solar system is anchored by the sun. The sun is the star at 14 00:01:13,305 --> 00:01:16,905 the center of our solar system. It's the gravitational force 15 00:01:16,905 --> 00:01:21,405 that pulls planets toward it. The eight planets in our system 16 00:01:21,405 --> 00:01:25,575 orbit or travel around the sun. We're going to explore those 17 00:01:25,575 --> 00:01:29,655 eight planets today, and we have a special guide for our journey. 18 00:01:29,600 --> 00:01:33,950 John: My name is John O'Meara, and I am the chief scientist at 19 00:01:33,950 --> 00:01:40,940 the W.M. Keck Observatory on the island of Hawaii. I am part of 20 00:01:40,940 --> 00:01:44,810 the team that helps run one of the biggest telescopes on the 21 00:01:44,810 --> 00:01:51,200 planet, the mirror itself is about 10 meters across, so about 22 00:01:51,200 --> 00:01:55,385 you know almost 40 feet across, and and then the dome that it 23 00:01:55,385 --> 00:01:58,175 sits in this giant structure that keeps it safe. 24 00:01:58,540 --> 00:02:01,630 Jane: Can you see some of the planets through the telescope? 25 00:02:01,740 --> 00:02:04,830 John: Oh, totally. We we look at the planets in our solar system 26 00:02:05,310 --> 00:02:10,980 a lot because because they're so close by, relatively speaking. I 27 00:02:11,010 --> 00:02:14,100 mean, they're very far in terms of how long it would take to fly 28 00:02:14,250 --> 00:02:17,070 there in an airplane if that worked. But because they're 29 00:02:17,160 --> 00:02:21,260 close by, we can watch them change over time. We like to 30 00:02:21,350 --> 00:02:25,910 look at Jupiter a lot. We like to look at Saturn a lot, and 31 00:02:25,970 --> 00:02:31,160 Uranus and Neptune a lot. The planets which are closer to the 32 00:02:31,160 --> 00:02:34,190 sun than us are hard for us to look at because the sun is so 33 00:02:34,310 --> 00:02:37,400 bright and because we don't want to damage the telescope. So we 34 00:02:37,460 --> 00:02:40,720 don't look at Mercury and Venus very often, but most of the 35 00:02:40,840 --> 00:02:44,140 time, it's it's the planets farther away, and their moons. 36 00:02:44,290 --> 00:02:45,940 We really like to look at their moons. 37 00:02:46,270 --> 00:02:49,270 Jane: I am glad that you can see the planets from the telescope 38 00:02:49,330 --> 00:02:53,110 because we called you up to talk about planets today, because 39 00:02:53,200 --> 00:02:56,080 kids have a ton of questions about planets. So we're gonna 40 00:02:56,290 --> 00:03:00,070 see how many we can get to, because we have so many. I don't 41 00:03:00,070 --> 00:03:03,060 know if we can fit it all in, so we're gonna yeah we're gonna 42 00:03:03,120 --> 00:03:06,750 make you go rapid fire, John, but we're gonna make you, we're 43 00:03:06,810 --> 00:03:10,890 gonna make you work here. So the first question we have is from 44 00:03:11,040 --> 00:03:11,400 Chandler. 45 00:03:11,910 --> 00:03:15,360 Chandler: How did the planets in our solar system get made? 46 00:03:15,810 --> 00:03:23,880 Rey: My name is Rey. I'm from Encinitasts, California. and I'm 47 00:03:23,880 --> 00:03:28,080 six years old. How do planets form? 48 00:03:28,080 --> 00:03:33,720 Maren: Hi, my name is Maren. I'm nine years old. I'm from 49 00:03:33,720 --> 00:03:37,650 Westfield, Massachusetts. Where do planets come from? 50 00:03:37,600 --> 00:03:41,290 John: Yeah, Chandler asks, and and and the other folks are 51 00:03:41,290 --> 00:03:45,370 asking a really, really fun, fantastic question, and part of 52 00:03:45,370 --> 00:03:48,850 the reason why it's fun and fantastic is we kind of know the 53 00:03:48,850 --> 00:03:52,030 answer, but we don't completely know the answer. And part of the 54 00:03:52,030 --> 00:03:54,730 reason why we don't completely know the answer is because this 55 00:03:54,730 --> 00:03:59,140 happened billions of years ago when the solar system formed. So 56 00:03:59,140 --> 00:04:03,565 the the best model that we have, the best theory that we have is 57 00:04:03,565 --> 00:04:07,765 that the sun and the planets formed out of what we call a 58 00:04:07,765 --> 00:04:11,935 nebula. A nebula is just a term for a bunch of gas and stuff. 59 00:04:11,935 --> 00:04:16,285 And about 5 billion years ago, that nebula, for some reason, 60 00:04:16,285 --> 00:04:19,915 started to collapse. It was just kind of sitting there, and then 61 00:04:19,915 --> 00:04:23,005 parts of it started to collapse, and then gravity started to take 62 00:04:23,050 --> 00:04:26,920 over, and stuff got closer and closer and closer. And most of 63 00:04:26,920 --> 00:04:32,770 the stuff became the sun. About 99% of the stuff became the sun, 64 00:04:32,770 --> 00:04:37,240 but some of the other stuff formed a disk around the sun, 65 00:04:37,240 --> 00:04:43,330 mostly of rock and ice and dust and gas, and that stuff started 66 00:04:43,330 --> 00:04:47,545 to form into the planets a few 100 million years after the sun 67 00:04:47,545 --> 00:04:51,415 started to form. And that disk of stuff, which had millions and 68 00:04:51,415 --> 00:04:56,035 millions and millions of chunks in it, billions, 10s of billions 69 00:04:56,035 --> 00:04:59,575 of chunks, eventually gravity started to pull those pieces 70 00:04:59,575 --> 00:05:02,725 together. Stuff started banging into each other, and over 71 00:05:02,725 --> 00:05:06,415 hundreds of millions of years, the planets in our solar system 72 00:05:06,415 --> 00:05:11,380 formed. But we didn't see this happen. We weren't there yet, 73 00:05:11,380 --> 00:05:16,540 but we've used big telescopes on the ground and in space to see 74 00:05:16,540 --> 00:05:21,160 this process happening in other solar systems as they're being 75 00:05:21,160 --> 00:05:25,840 born, and we can see this disk of stuff, and we can see it 76 00:05:25,840 --> 00:05:30,790 start to clump up, and so that helps reinforce this idea that's 77 00:05:30,790 --> 00:05:34,495 that's how our solar system formed. But it's still, you 78 00:05:34,495 --> 00:05:37,645 know, it's it's still just you know something that we have to 79 00:05:37,645 --> 00:05:40,765 keep testing, we have to keep looking, we have to pick up as 80 00:05:40,765 --> 00:05:43,285 much material as we can throughout the solar system, 81 00:05:43,285 --> 00:05:46,645 whether or not it's a rock on Mars or it's a chunk of a comet 82 00:05:46,645 --> 00:05:49,855 or an asteroid. We need to go out there, look at that 83 00:05:49,855 --> 00:05:53,245 material, and see if it matches this idea for how the solar 84 00:05:53,245 --> 00:05:53,965 system formed. 85 00:05:53,995 --> 00:06:00,460 Gabby: Hi, my name is Gabby. I'm six years old. I live in 86 00:06:00,460 --> 00:06:08,050 Colorado, and my question is, why are some planets made of gas 87 00:06:08,050 --> 00:06:10,840 and some planets are not? 88 00:06:10,840 --> 00:06:13,780 John: If you look at the planets in the solar system, the ones 89 00:06:13,780 --> 00:06:18,475 that are closer to the sun are mostly made of rocks. So Mercury 90 00:06:18,475 --> 00:06:22,285 is made of rocks. Venus, we can't see the surface of from 91 00:06:22,285 --> 00:06:25,135 here because it has really, really thick clouds. But most of 92 00:06:25,135 --> 00:06:30,655 it is rocks. Most of the Earth is rocks. Mars is mostly rocky. 93 00:06:30,655 --> 00:06:33,415 But then, when you go farther out in the solar system, like 94 00:06:33,415 --> 00:06:37,225 Gabby says, there's there's these giant balls of gas, like 95 00:06:37,225 --> 00:06:40,735 Jupiter, the biggest planet in the solar system, Saturn, 96 00:06:40,975 --> 00:06:44,860 Uranus, Neptune-these are giant things of gas. Why is that so 97 00:06:44,860 --> 00:06:48,700 different? And it has to do with how close the things were to the 98 00:06:48,700 --> 00:06:53,500 Sun when they formed. When you're really close to the Sun, 99 00:06:53,500 --> 00:06:57,130 relatively speaking, it's hotter. The Sun is brighter when 100 00:06:57,130 --> 00:07:02,470 you're closer to it, and that energy doesn't let gas start to 101 00:07:02,470 --> 00:07:07,315 form into ice and ice to start capturing more gas. It only lets 102 00:07:07,315 --> 00:07:10,885 the rocks stick around, and so in the early parts of the solar 103 00:07:10,885 --> 00:07:16,045 system, that energy from the sun only let rocky things start to 104 00:07:16,045 --> 00:07:19,615 form close by. But when they were far enough away that they 105 00:07:19,615 --> 00:07:24,475 could that ice could form. Ice did form, and ice is really, 106 00:07:24,475 --> 00:07:28,000 really good at grabbing other stuff, grabbing other ice or 107 00:07:28,000 --> 00:07:33,310 other gas. And so, kind of like when you build a snowman, you 108 00:07:33,310 --> 00:07:37,900 start to push the snow, and it starts to glom onto it and get 109 00:07:37,900 --> 00:07:41,320 bigger and bigger and bigger. That snowball method is how the 110 00:07:41,320 --> 00:07:46,060 big gas giants formed out in the solar system, and they just 111 00:07:46,060 --> 00:07:50,635 captured all that gas. Now the other part of the question was 112 00:07:50,635 --> 00:07:54,295 why? Why does it even happen at all? And the answer there is 113 00:07:54,295 --> 00:07:58,405 gravity. The same thing that if you you know if you jump off of 114 00:07:58,405 --> 00:08:02,275 a step onto the ground, you know, gravity is pulling you 115 00:08:02,275 --> 00:08:05,305 down towards the the center of the Earth because the Earth has 116 00:08:05,305 --> 00:08:08,995 a lot of mass, and because you have mass. And whenever two 117 00:08:08,995 --> 00:08:11,815 things have mass, they get attracted to each other by 118 00:08:11,815 --> 00:08:16,240 gravity. And so, when stuff started to form, there was more 119 00:08:16,240 --> 00:08:19,420 and more and more mass, and the gravity nearby it got stronger 120 00:08:19,420 --> 00:08:22,660 and stronger, and all of that stuff held together to keep the 121 00:08:22,660 --> 00:08:26,140 planets held together. It's the same as true for the sun. The 122 00:08:26,140 --> 00:08:29,860 sun isn't rocky at all. It's mostly gas and very, very hot 123 00:08:29,860 --> 00:08:32,890 gas, depending on where you are in the sun. But gravity is 124 00:08:32,890 --> 00:08:34,510 what's holding it together. 125 00:08:34,670 --> 00:08:37,130 Jane: So the planets and the sun are being held together by 126 00:08:37,250 --> 00:08:41,920 gravity, but they are also moving in space. Planets orbit 127 00:08:42,010 --> 00:08:45,850 or travel around the sun in a kind of oval or elliptical 128 00:08:45,970 --> 00:08:50,470 pattern. Some orbits are almost circular, but most are kind of 129 00:08:50,650 --> 00:08:54,430 stretched-out ovals. The size of the orbit depends on the 130 00:08:54,520 --> 00:08:59,110 distance from the planet to the sun. But Why and how do they do 131 00:08:59,200 --> 00:08:59,350 that? 132 00:08:59,720 --> 00:09:03,770 Penny: This is Penny from Chappaqua, New York. My question 133 00:09:03,800 --> 00:09:08,060 is: How do planets float in space? 134 00:09:09,090 --> 00:09:13,140 Malcolm: Hello, my name is Malcolm. I live in Seattle, 135 00:09:13,200 --> 00:09:17,340 Washington. My age is seven. My question is: How do planets stay 136 00:09:17,460 --> 00:09:17,760 in place? 137 00:09:18,900 --> 00:09:23,240 Ruby: My name is Ruby, and I'm four years old, and I live in 138 00:09:23,540 --> 00:09:29,000 Seattle, Washington. And my question is, how do the planets 139 00:09:29,450 --> 00:09:30,770 get out of the spot? 140 00:09:31,790 --> 00:09:34,880 Oliver: Hello, my name is Oliver. I'm seven years old, and 141 00:09:35,060 --> 00:09:38,600 I'm from Wellington, New Zealand. And my question is, why 142 00:09:38,690 --> 00:09:39,620 do planets spin? 143 00:09:40,310 --> 00:09:48,340 Larry: My name is Larry, and I am five years old. I'm from Los 144 00:09:49,150 --> 00:09:57,790 Angeles, California. Why do the planets rotate? 145 00:09:58,720 --> 00:10:02,485 John: It goes back to that model of how we think the solar system 146 00:10:02,549 --> 00:10:05,995 formed. So when the stuff started to collapse, it also 147 00:10:06,059 --> 00:10:10,015 started to rotate. It started to spin around a little bit. And 148 00:10:10,079 --> 00:10:13,908 when we look at the disks of those early solar systems going 149 00:10:13,972 --> 00:10:17,546 around stars, we see that they're moving around, kind of 150 00:10:17,610 --> 00:10:21,247 like a record on a record player. When you start spinning 151 00:10:21,311 --> 00:10:25,268 around, the universe likes to keep you spinning around. So all 152 00:10:25,331 --> 00:10:29,224 you have to do is start that rotation. People know this, like 153 00:10:29,288 --> 00:10:33,436 when they go out ice skating and and they they put their arms out 154 00:10:33,500 --> 00:10:37,648 really wide, and if you start to spin, you you will keep spinning 155 00:10:37,712 --> 00:10:41,605 because you know you don't have a lot of friction slowing you 156 00:10:41,669 --> 00:10:45,370 down on the ice. In space there's no none of that friction 157 00:10:45,434 --> 00:10:49,263 at all, so you keep spinning around and around. But one neat 158 00:10:49,327 --> 00:10:52,964 thing happens if you pull your arms in, you start to spin 159 00:10:53,028 --> 00:10:56,921 faster, and that has to do with something called momentum and 160 00:10:56,985 --> 00:11:00,814 and rotational momentum. It's the energy that's locked up in 161 00:11:00,878 --> 00:11:04,515 movement. We have movement in straight lines, which is is 162 00:11:04,579 --> 00:11:08,727 regular momentum, and rotational momentum is when you're spinning 163 00:11:08,791 --> 00:11:12,556 around. If you pull your arms and you spin faster, here's a 164 00:11:12,620 --> 00:11:16,577 neat thing: the planets closer to the sun orbit around the sun 165 00:11:16,641 --> 00:11:20,661 faster than the planets farther away from the sun. So the Earth 166 00:11:20,725 --> 00:11:24,299 takes about a year to go around the sun, but the planets 167 00:11:24,363 --> 00:11:28,192 outside, farther outside in the solar system, take 10s up to 168 00:11:28,256 --> 00:11:30,745 hundreds of years to go around the sun. 169 00:11:31,400 --> 00:11:33,650 Jane: I thought maybe they were just taking longer to go around 170 00:11:33,770 --> 00:11:36,170 the sun because they're so much farther away, but they're 171 00:11:36,350 --> 00:11:40,160 actually orbiting slower, so they have a longer path to 172 00:11:40,280 --> 00:11:43,360 travel to get around the sun, but they're doing it at a slower 173 00:11:43,540 --> 00:11:47,740 pace too. It's like the planets close to the sun are sprinting, 174 00:11:48,100 --> 00:11:51,490 and the ones farther out are just taking a nice leisurely 175 00:11:51,580 --> 00:11:51,880 stroll. 176 00:11:52,330 --> 00:11:58,390 Oliver: Hi, my name is Oliver. I'm almost five, and I live in 177 00:11:58,810 --> 00:12:02,610 St. Louis. And why does space have so many planets? 178 00:12:04,290 --> 00:12:11,790 Jeremiah: I'm Jeremiah. I'm six years old. I'm from Alexandria, 179 00:12:11,910 --> 00:12:17,850 Virginia, and my question is: Why does space have so many 180 00:12:18,000 --> 00:12:18,570 planets? 181 00:12:19,000 --> 00:12:22,900 John: That's a great question, and and if if I can I'll answer 182 00:12:22,900 --> 00:12:25,840 in two different parts because there's there's a there's a neat 183 00:12:25,840 --> 00:12:28,810 thing that we're starting to learn about in astronomy right 184 00:12:28,810 --> 00:12:32,020 now about planets around other stars but let me start with the 185 00:12:32,020 --> 00:12:36,370 solar system. When the solar system started off there were 186 00:12:36,370 --> 00:12:40,600 many many many more planets than there are today and that's 187 00:12:40,600 --> 00:12:44,395 because the stuff started falling in together and glomming 188 00:12:44,395 --> 00:12:48,475 together like snowballs forming a giant snowman, and some of 189 00:12:48,475 --> 00:12:51,355 them smacked into each other and got kicked out of the solar 190 00:12:51,355 --> 00:12:54,475 system entirely. But over hundreds of millions of years, 191 00:12:54,475 --> 00:12:58,255 these things formed into much, much bigger things, which we now 192 00:12:58,255 --> 00:13:03,595 call planets. One piece of the solar system that still kind of 193 00:13:03,595 --> 00:13:06,640 looks like that early part of the solar system is called the 194 00:13:06,640 --> 00:13:11,020 asteroid belt. It's a place between Mars and Jupiter. If 195 00:13:11,020 --> 00:13:14,470 you're going away from the sun, Jupiter's farther away than 196 00:13:14,470 --> 00:13:18,760 Mars. In between there, there's all these asteroids, millions of 197 00:13:18,760 --> 00:13:22,480 them, giant chunks of rock, and those are leftover material from 198 00:13:22,480 --> 00:13:26,410 the formation of the solar system. They didn't quite form 199 00:13:26,410 --> 00:13:30,205 into a planet, and they didn't quite get kicked out. And in a 200 00:13:30,205 --> 00:13:33,595 very, very long time from now, they'll slowly start getting 201 00:13:33,595 --> 00:13:36,445 thrown out of the solar system, or bounce into each other, or 202 00:13:36,445 --> 00:13:40,015 bounce into Jupiter, or bounce into Mars, bounce into other 203 00:13:40,015 --> 00:13:44,005 things. Most of them will get thrown out. But that process 204 00:13:44,005 --> 00:13:47,005 over billions of years took us from hundreds of millions of 205 00:13:47,005 --> 00:13:51,430 objects into the solar system into a few dozen that are that 206 00:13:51,430 --> 00:13:57,520 are now planets or dwarf planets. The other fun thing is 207 00:13:57,520 --> 00:14:02,890 that now that we've looked in detail at other stars, we think 208 00:14:02,890 --> 00:14:05,560 that almost every star in the universe has at least one 209 00:14:05,560 --> 00:14:09,700 planet, and that most stars in the universe have more than one 210 00:14:09,700 --> 00:14:12,940 planet. And that's probably a different discussion for a 211 00:14:12,940 --> 00:14:16,525 different time. But it's really neat to know that our solar 212 00:14:16,525 --> 00:14:19,465 system isn't alone in terms of having planets. 213 00:14:19,690 --> 00:14:23,260 Jane: So we don't even know how many planets there are if we're 214 00:14:23,260 --> 00:14:25,750 thinking outside our solar system. 215 00:14:25,750 --> 00:14:28,420 John: We don't know. That's one of the things we like to do a 216 00:14:28,420 --> 00:14:31,900 lot with the telescope here in Hawaii is is to look for planets 217 00:14:31,900 --> 00:14:35,020 around other stars and find more of them and more of them and 218 00:14:35,020 --> 00:14:35,470 more of them. 219 00:14:35,840 --> 00:14:36,680 Jane: Do you have a guess? 220 00:14:37,420 --> 00:14:41,260 John: I have a rough guess, and the rough guess is that if I if 221 00:14:41,260 --> 00:14:46,420 I use a trick and say every star has at least one planet, and if 222 00:14:46,420 --> 00:14:50,560 I think I know how many stars there are in our galaxy, which 223 00:14:50,560 --> 00:14:55,120 is about 200 billion stars, but notice I said about we don't 224 00:14:55,120 --> 00:14:59,620 really know we can't count them one by one we use we use little 225 00:14:59,620 --> 00:15:03,985 tricks in math to do that, but that means there are at least 226 00:15:03,985 --> 00:15:11,065 200 billion planets in the Milky Way, and we think in the in the 227 00:15:11,065 --> 00:15:17,335 universe that we can see, we can see at least a few 100 billion 228 00:15:17,335 --> 00:15:20,935 galaxies. So now you need to get out your your your your 229 00:15:20,935 --> 00:15:23,665 calculator or a piece of paper and start writing a lot of 230 00:15:23,710 --> 00:15:28,210 zeros, because if every galaxy has a couple 100 billion stars, 231 00:15:28,210 --> 00:15:31,210 and all of those stars have at least one planet, then we're 232 00:15:31,210 --> 00:15:34,780 we're we're talking about 200 billion times 200 billion times 233 00:15:34,780 --> 00:15:37,660 a lot, and so that's a lot a lot of planets in the in the 234 00:15:37,660 --> 00:15:38,350 universe. 235 00:15:38,510 --> 00:15:42,640 Isaac: My name is Isaac from Saskatchewan, Canada, and I'm 10 236 00:15:42,730 --> 00:15:45,430 years old. How did humans figure out about planets? 237 00:15:45,550 --> 00:15:48,100 Jane: How did humans even figure out about planets to begin with? 238 00:15:48,580 --> 00:15:53,050 John: So, planet is that the word planet in English is 239 00:15:53,140 --> 00:15:58,420 derived from the Greek language, but from from way back when. 240 00:15:58,630 --> 00:16:03,450 That is is is a word that means wanderer, and when we look up at 241 00:16:03,450 --> 00:16:06,780 the night sky, and and and and humans have been really good at 242 00:16:06,840 --> 00:16:09,450 looking at the night sky since since there have been humans 243 00:16:09,630 --> 00:16:13,380 because it's always there, always there to to see the stars 244 00:16:13,680 --> 00:16:16,740 and and to look up and and and and be really interested and 245 00:16:16,740 --> 00:16:20,570 excited about that. But when you look up at the stars and you 246 00:16:20,690 --> 00:16:23,900 look long enough, you'll see that most of them are stuck in 247 00:16:23,930 --> 00:16:26,600 the exact same spot they were the night before, or the week 248 00:16:26,690 --> 00:16:31,220 before, or the month before. But you will see some bright things 249 00:16:31,640 --> 00:16:38,030 move; they wander on the sky, and so we we call those things 250 00:16:38,180 --> 00:16:43,360 planets. And human beings, for for most of history that that 251 00:16:43,450 --> 00:16:49,420 that that's been recorded, could only see some of the planets in 252 00:16:49,480 --> 00:16:52,510 our solar system. Uranus and Neptune are so far away that we 253 00:16:52,660 --> 00:16:55,210 can't see them with our eyes and know that they are planets. 254 00:16:57,340 --> 00:17:01,710 Then, in about the 1600s, in the early 1600s, we started to build 255 00:17:01,740 --> 00:17:05,790 telescopes, and when you build telescopes, you can look in more 256 00:17:05,880 --> 00:17:08,880 detail and you can see fainter things. And that's when we 257 00:17:09,060 --> 00:17:12,420 really started to study planets well and understand that some of 258 00:17:12,480 --> 00:17:15,510 them were made of gas and some of them were made of rocks. 259 00:17:16,050 --> 00:17:19,350 Because at the same time as we were developing telescopes, we 260 00:17:19,470 --> 00:17:23,000 were developing new types of physics and chemistry, and all 261 00:17:23,180 --> 00:17:25,700 the things that you need to tell the difference between a rock 262 00:17:26,390 --> 00:17:31,430 and a bunch of gas that's hundreds of 1000s of millions of 263 00:17:31,760 --> 00:17:35,600 miles away-stuff that you can't reach out and touch yet-and then 264 00:17:36,770 --> 00:17:40,550 we started to build rockets, and we put robots on rockets, and we 265 00:17:40,730 --> 00:17:43,540 landed them in places in the solar system and grabbed that 266 00:17:43,660 --> 00:17:45,220 stuff and tested those theories. 267 00:17:45,600 --> 00:17:47,640 Jane: All right, now that we have some understanding of our 268 00:17:47,640 --> 00:17:50,610 solar system and how it formed, we're going to go on that tour 269 00:17:50,610 --> 00:17:54,090 of all the planets. So get a drink of water, take a break 270 00:17:54,090 --> 00:17:56,490 because there's going to be a lot to get through when we come 271 00:17:56,490 --> 00:17:57,870 back. 272 00:17:57,960 --> 00:18:01,290 This is But Why. Today we're talking with astronomer John 273 00:18:01,350 --> 00:18:04,380 O'Meara, who helps run one of the biggest telescopes in the 274 00:18:04,380 --> 00:18:08,670 world at the Keck Observatory in Hawaii. All right, John, let's 275 00:18:08,670 --> 00:18:11,940 talk about specific planets, and we're going to start with the 276 00:18:11,940 --> 00:18:16,230 planets closest to the sun and move outwards. So the planet 277 00:18:16,230 --> 00:18:19,080 closest to the sun-I know some of the kids who are listening 278 00:18:19,080 --> 00:18:22,170 are like shouting it out already-is Mercury. 279 00:18:22,215 --> 00:18:23,505 John: Yeah. 280 00:18:23,505 --> 00:18:26,745 Jane: We don't have any questions about Mercury. Why do 281 00:18:26,745 --> 00:18:28,545 you think that is? We have questions about every other 282 00:18:28,545 --> 00:18:30,555 planet. Why isn't anybody sending us questions about 283 00:18:30,555 --> 00:18:33,105 Mercury? Is it really not very cool? 284 00:18:33,105 --> 00:18:36,975 John: Mercury's totally cool. I think part of the issue is we 285 00:18:36,975 --> 00:18:40,425 haven't sent many spacecraft to Mercury, so we don't have a lot 286 00:18:40,425 --> 00:18:44,280 of pictures of Mercury up close, like we do for Venus or Mars or 287 00:18:44,280 --> 00:18:50,550 the other planets in in close to us, or Jupiter, or or Saturn or 288 00:18:50,550 --> 00:18:56,220 Uranus or Neptune. And Mercury's really close to the Sun, which 289 00:18:56,220 --> 00:19:00,540 means it's kind of a nasty place to visit, and it's also hard to 290 00:19:00,540 --> 00:19:03,690 see with your eyes. There's only special times of year that you 291 00:19:03,690 --> 00:19:07,035 can see Mercury at all because it's so close to the sun, and 292 00:19:07,035 --> 00:19:10,605 sun the sun is really bright. So the sun has to set, and you have 293 00:19:10,605 --> 00:19:14,145 to have Mercury in special parts of its orbit to see it at all. 294 00:19:14,145 --> 00:19:18,345 So I think all those things put together make you know kind of 295 00:19:18,345 --> 00:19:23,445 stack the odds against Mercury. But we have spacecraft that are 296 00:19:23,445 --> 00:19:26,655 there now, looking, you know, starting to to orbit around 297 00:19:26,655 --> 00:19:30,060 Mercury and study it, and it's a really fascinating place because 298 00:19:30,060 --> 00:19:32,670 how do you have a planet that close to the sun and still have 299 00:19:32,670 --> 00:19:34,500 it around and all that stuff? It's kind of neat. 300 00:19:34,610 --> 00:19:36,710 Jane: All right, you sold me on Mercury. Maybe we'll get some 301 00:19:36,950 --> 00:19:40,450 Mercury questions and we'll have you back. Let's go next. Travel 302 00:19:40,570 --> 00:19:41,800 outwards to Venus. 303 00:19:42,000 --> 00:19:45,750 Rylo: Hi, my name is Rylo. I'm five years old. I live in 304 00:19:45,750 --> 00:19:51,480 Glendale. Why is Venus the hottest, but it's not closest to 305 00:19:51,480 --> 00:19:52,290 the sun? 306 00:19:52,330 --> 00:19:56,260 Jane: Why is Venus the hottest, but not closest to the sun? 307 00:19:56,320 --> 00:19:58,270 Because you just said Mercury was closest to the sun. 308 00:19:58,330 --> 00:20:02,650 John: Yeah, Mercury is really close to the sun, and it's not 309 00:20:02,650 --> 00:20:06,670 as hot. And part of the reason is that Mercury only has a very, 310 00:20:06,670 --> 00:20:12,280 very, very tiny atmosphere. Venus, on the other hand, has a 311 00:20:12,280 --> 00:20:17,230 very thick, heavy atmosphere. In fact, Venus is about the same 312 00:20:17,230 --> 00:20:24,145 size as the Earth, but it has an atmosphere which is 90 times as 313 00:20:24,145 --> 00:20:27,805 thick as our atmosphere, and what do I mean by thick? I mean 314 00:20:27,805 --> 00:20:27,925 there. 315 00:20:27,925 --> 00:20:29,635 Jane: And what do you mean by atmosphere? 316 00:20:29,540 --> 00:20:33,980 John: Yeah, what do I mean by atmosphere? So you and I are 317 00:20:33,980 --> 00:20:36,950 sitting here breathing air, and the air is mostly made of 318 00:20:36,950 --> 00:20:41,180 nitrogen and a little bit of oxygen, some carbon dioxide, and 319 00:20:41,180 --> 00:20:46,310 that air is for a few 100 miles above the Earth, and it gets 320 00:20:46,310 --> 00:20:49,040 less and less atmosphere as you get farther and farther away 321 00:20:49,040 --> 00:20:53,315 from the surface. But that air has a quantity called pressure, 322 00:20:52,025 --> 00:23:12,035 Jane: John, you and I have talked in previous episodes 323 00:20:53,315 --> 00:20:55,565 and we know we have pressure because if you take your hand 324 00:20:55,565 --> 00:20:57,785 and you swipe it through the air, you can actually feel the 325 00:20:57,785 --> 00:21:01,235 wind against your hand, and that's because there's enough 326 00:21:01,235 --> 00:21:06,095 air there to feel that that material. If you tried to do 327 00:21:06,095 --> 00:21:09,995 that on Venus, you would have to work a lot harder because the 328 00:21:09,995 --> 00:21:14,615 air is much more dense. It's almost like water. It's very, 329 00:21:14,615 --> 00:21:19,340 very, very dense, and most of the atmosphere on Venus is made 330 00:21:19,340 --> 00:21:24,560 out of carbon dioxide instead of nitrogen and and oxygen. Carbon 331 00:21:24,560 --> 00:21:29,780 dioxide is really good at grabbing heat and keeping it 332 00:21:29,780 --> 00:21:34,910 there. A long time ago, it used to have we we thought think it 333 00:21:34,910 --> 00:21:38,030 used to have oceans on its surface or at least some water, 334 00:21:38,645 --> 00:21:43,835 and then something happened to evaporate that water away and to 335 00:21:43,835 --> 00:21:47,255 change the atmosphere, and it had lots of volcanoes, dumped a 336 00:21:47,255 --> 00:21:50,585 lot of carbon dioxide into the atmosphere, and then that 337 00:21:50,585 --> 00:21:54,665 trapped the heat, and this is this ran away. This this didn't 338 00:21:54,665 --> 00:21:59,045 circulate. This kept getting more and more and more and more, 339 00:21:59,045 --> 00:22:02,960 and we call that the runaway greenhouse effect, and that 340 00:22:02,960 --> 00:22:09,980 makes the surface of Venus hundreds of degrees. It is very 341 00:22:09,980 --> 00:22:14,510 very hot. That pressure is very very high. We've landed a couple 342 00:22:14,510 --> 00:22:19,040 of spacecraft on Venus, and those spacecraft only survived a 343 00:22:19,040 --> 00:22:24,020 very short time because it was so hot and so dense that they 344 00:22:24,020 --> 00:22:27,065 kind of crushed the spacecraft after a bit of time, even though 345 00:22:27,065 --> 00:22:31,655 we built them to sort to to to really handle that environment. 346 00:22:31,655 --> 00:22:38,375 So we don't completely understand why that started on 347 00:22:38,375 --> 00:22:43,985 Venus, but we understand the physics of atmospheres to 348 00:22:43,985 --> 00:22:48,455 understand once it kicked off why it it stayed that way, and 349 00:22:48,725 --> 00:22:52,010 what's really interesting about Venus is that the surface is 350 00:22:52,010 --> 00:22:55,940 nasty. It rains acid on Venus. You don't want to be there, I 351 00:22:55,940 --> 00:23:01,190 promise. But high up enough, the atmosphere starts to get thin 352 00:23:01,190 --> 00:23:07,310 again, and there's parts of up and above the clouds in Venus 353 00:23:07,310 --> 00:23:10,745 which are about the same temperature as the Earth, and 354 00:23:10,745 --> 00:23:14,405 you know kind of a nice place to be. And so we are we are 355 00:23:12,035 --> 00:23:37,730 about the Earth's moon and other things about Earth's atmosphere, 356 00:23:14,405 --> 00:23:19,295 building some spacecraft. NASA is working on two spacecraft 357 00:23:19,295 --> 00:23:23,255 that will be launched to Venus to study those clouds as well as 358 00:23:23,255 --> 00:23:27,125 the surface, which we've looked at before with radar and by 359 00:23:27,125 --> 00:23:29,795 landing some stuff on it. 360 00:23:37,730 --> 00:23:41,420 and we've done a lot of episodes that kids can listen to about 361 00:23:41,420 --> 00:23:43,940 Earth's atmosphere and our moon. So we're we're not going to 362 00:23:43,940 --> 00:23:48,290 focus a lot on Earth today, but I have one question from Eli 363 00:23:48,290 --> 00:23:51,830 that we want to share with you that will help tie us from Venus 364 00:23:51,830 --> 00:23:56,180 to Earth, which is the next one out, and then to Mars, which is 365 00:23:56,225 --> 00:23:58,295 the next planet out. 366 00:23:58,420 --> 00:24:03,300 Eli: My name is Eli. I'm seven years old. I live in Cleveland, 367 00:24:03,540 --> 00:24:10,260 Ohio. Why is Earth more like Mars than Venus, its sister 368 00:24:10,410 --> 00:24:10,860 planet? 369 00:24:11,540 --> 00:24:15,560 John: So the three planets are very, very different from each 370 00:24:15,560 --> 00:24:19,790 other. You're absolutely right, and part of that difference is 371 00:24:19,790 --> 00:24:22,700 what we were talking about with Venus before that it had this 372 00:24:22,700 --> 00:24:26,030 this very big change in its atmosphere that made it really 373 00:24:26,030 --> 00:24:29,960 dense and really hot. On the other hand, we have Earth, which 374 00:24:29,960 --> 00:24:34,895 we know pretty well, and then we have Mars, which is very cold 375 00:24:34,895 --> 00:24:38,315 relative to Earth, or certainly relative to Venus, and it 376 00:24:38,315 --> 00:24:41,525 doesn't have to do with their distance from the Sun very much 377 00:24:41,525 --> 00:24:45,335 because they're all kind of close to the sun, roughly the 378 00:24:45,335 --> 00:24:52,175 roughly about the same. The difference is that Mars had a 379 00:24:52,175 --> 00:24:56,555 different kind of event a long time ago, about a billion years 380 00:24:56,555 --> 00:25:00,920 ago, in which it lost its atmosphere. It didn't start 381 00:25:00,920 --> 00:25:05,360 rapidly gaining thickness in its atmosphere like Venus did. 382 00:25:05,360 --> 00:25:10,970 Something happened to strip away a lot of Mars's atmosphere, and 383 00:25:10,970 --> 00:25:17,240 that really changed Mars relative to Earth and Venus. 384 00:25:17,240 --> 00:25:20,675 Mars used to have oceans on it. We we believe this when you look 385 00:25:20,675 --> 00:25:23,975 at at the at the surface features of Mars, and we dug 386 00:25:23,975 --> 00:25:27,365 into a little bit of the surface of Mars with rovers and other 387 00:25:27,365 --> 00:25:32,435 things, we know that Mars probably had oceans on it and an 388 00:25:32,435 --> 00:25:36,605 atmosphere that kept those oceans from just boiling off and 389 00:25:36,605 --> 00:25:41,135 going off into space. But something took that atmosphere 390 00:25:41,135 --> 00:25:43,370 away, and this is why studying planets is so cool. Is because 391 00:25:43,370 --> 00:25:47,690 we don't know yet why these things happened, but when you 392 00:25:47,690 --> 00:25:51,290 stripped away that atmosphere and the oceans evaporated off of 393 00:25:51,290 --> 00:25:54,800 Mars, Mars still has an atmosphere, but it's only about 394 00:25:54,800 --> 00:25:59,720 1 percent as thick as the atmosphere on Earth. 395 00:25:59,720 --> 00:26:02,240 Jane: Ooh, hold up for a second. Let's squeeze in Jamison's 396 00:26:02,240 --> 00:26:03,320 question right here. 397 00:26:03,320 --> 00:26:06,530 Jameson: I live in the United States of America. I am 10 years 398 00:26:06,530 --> 00:26:10,115 old, and my question is: Why is Mars so cold? 399 00:26:10,115 --> 00:26:12,815 John: Because the atmosphere can't trap that heat in and keep 400 00:26:12,815 --> 00:26:13,775 things warm. 401 00:26:13,775 --> 00:26:19,055 Ilina: Hi, my name is Ilinaa. I'm six years old. I live in 402 00:26:19,715 --> 00:26:25,595 Newtown Square, Pennsylvania. and my question is why is Mars 403 00:26:25,595 --> 00:26:26,915 red? 404 00:26:27,080 --> 00:26:30,320 John: Mars has this this kind of eerie reddish color, and the 405 00:26:30,440 --> 00:26:34,430 main reason why it has that color is because a lot of the 406 00:26:34,520 --> 00:26:40,250 surface on Mars has iron in it, in the sands, in the rocks, and 407 00:26:40,370 --> 00:26:44,050 and all throughout the surface has iron in it. But you can say, 408 00:26:44,170 --> 00:26:47,620 well, wait, I have a I have a cast iron pan at home, and it's 409 00:26:47,800 --> 00:26:52,630 black. Well, it's black unless you just leave it in water or 410 00:26:52,720 --> 00:26:55,330 leave it out in the air for a long time, and then it starts to 411 00:26:55,540 --> 00:26:59,830 rust. This is what happens when oxygen interacts with iron over 412 00:26:59,890 --> 00:27:04,050 a long time: is it turns into rust, iron oxide, and so the 413 00:27:04,080 --> 00:27:08,220 surface of Mars is that color in part because the iron started 414 00:27:08,370 --> 00:27:11,940 rusting in the atmosphere of Mars, leaving it that weird 415 00:27:12,030 --> 00:27:12,540 reddish color. 416 00:27:13,890 --> 00:27:15,420 Jane: Okay, what about dust storms? 417 00:27:15,630 --> 00:27:22,800 Levin: My name is Levin, and I'm four years old and live in 418 00:27:22,800 --> 00:27:29,580 Boulder, Colorado. I want to know more about why dust storms 419 00:27:29,580 --> 00:27:32,040 happen on Mars. 420 00:27:32,150 --> 00:27:35,300 John: We get dust storms on Earth, like in this in the 421 00:27:35,300 --> 00:27:38,930 Sahara and other deserts. We see this a lot, where these these 422 00:27:39,050 --> 00:27:42,550 big winds will kick up the sand into the air, and lots of Mars 423 00:27:42,610 --> 00:27:48,250 is covered in in sand. And the there are winds on Mars, even 424 00:27:48,250 --> 00:27:51,670 though there's only about 1% the the atmospheric pressure. There 425 00:27:51,670 --> 00:27:55,750 are still winds there, and when sometimes the winds can get very 426 00:27:56,050 --> 00:28:00,600 very powerful relative to just a normal day on Mars, that kicks 427 00:28:00,780 --> 00:28:04,110 up the dust, and then these these massive dust storms go 428 00:28:04,350 --> 00:28:07,230 through. And so, when you look at the surface of Mars, you can 429 00:28:07,350 --> 00:28:10,140 see things which are basically sand dunes, and they were put 430 00:28:10,230 --> 00:28:14,370 there by these by these giant dust storms. Mars has seasons 431 00:28:14,490 --> 00:28:17,880 like Earth does. When the winds come, you know, and and you can 432 00:28:18,480 --> 00:28:20,700 pick up the sand, you get these massive dust storms. 433 00:28:20,880 --> 00:28:23,120 Jane: All right, so we're going to jump back in our futuristic 434 00:28:23,240 --> 00:28:26,750 spaceship now that can amazingly go to and from all the planets. 435 00:28:26,780 --> 00:28:29,960 We're going from Mars. How far do we have to go to get to the 436 00:28:30,020 --> 00:28:31,130 next planet, Jupiter? 437 00:28:31,450 --> 00:28:34,420 John: Well, we have to go pretty far. So let's use units that 438 00:28:34,420 --> 00:28:38,470 that I like to describe the solar system because because we 439 00:28:38,470 --> 00:28:43,030 live on Earth, we can say the Earth is one unit away from the 440 00:28:43,030 --> 00:28:49,000 Sun. Venus is about 0.7 units away from the Sun, about a 441 00:28:49,000 --> 00:28:53,440 little bit more than half a unit. Mars is 1.5 units away 442 00:28:53,440 --> 00:28:57,385 from the Sun. You have to go pretty far now. You have to go 443 00:28:57,385 --> 00:29:01,855 five units away from the Sun to get to Jupiter, and that's the 444 00:29:01,855 --> 00:29:06,085 big one in the solar system. That's the biggest planet there 445 00:29:06,085 --> 00:29:11,005 there is in the solar system. It has most of the material locked 446 00:29:11,005 --> 00:29:15,175 up in it relative to all the other planets, which is which is 447 00:29:15,175 --> 00:29:17,530 pretty amazing because you know we think oh Saturn's big yeah 448 00:29:17,530 --> 00:29:22,870 Saturn's big but Jupiter is big, and Jupiter is kind of was was 449 00:29:22,870 --> 00:29:26,440 very much along with the sun like a vacuum cleaner for the 450 00:29:26,440 --> 00:29:30,010 solar system. When there was all that material out in the disk, 451 00:29:30,010 --> 00:29:33,100 if that stuff didn't start to form into into their own 452 00:29:33,100 --> 00:29:36,940 planets, Jupiter's gravity, because it's so big and so 453 00:29:36,940 --> 00:29:40,030 massive, helped pick up that stuff, and that stuff got 454 00:29:40,075 --> 00:29:44,845 incorporated into Jupiter, so it is a big, giant gas planet. It's 455 00:29:44,845 --> 00:29:49,615 made out of hydrogen and helium, and we think it has a rocky core 456 00:29:49,615 --> 00:29:55,285 inside of it, but it's it's huge, and its mass has really 457 00:29:55,285 --> 00:29:59,215 impacted the whole shape of the rest of the the solar system. It 458 00:29:59,215 --> 00:30:01,675 and the sun are the two big bullies of the solar system 459 00:30:01,675 --> 00:30:02,935 pushing stuff around. 460 00:30:02,990 --> 00:30:07,730 Griffin: My name is Griffin, and why is the storm on Jupiter red? 461 00:30:07,730 --> 00:30:10,670 Jane: And maybe you can help explain for kids who don't know 462 00:30:10,670 --> 00:30:12,230 about Jupiter's storms. 463 00:30:12,780 --> 00:30:17,190 John: Jupiter is made out of a lot of gas, and Jupiter rotates 464 00:30:17,550 --> 00:30:23,360 pretty fast. So on Earth, we have these things called 465 00:30:23,420 --> 00:30:27,050 hurricanes or cyclones, and hurricanes have their shape, 466 00:30:27,170 --> 00:30:30,500 these spirally shapes that are spinning around because the 467 00:30:30,530 --> 00:30:33,020 Earth is spinning around. It's it's it's a thing called the 468 00:30:33,080 --> 00:30:37,520 Coriolis effect. Well, Jupiter is spinning around pretty fast, 469 00:30:38,450 --> 00:30:42,460 and it's a really really big planet, so it can have 470 00:30:42,610 --> 00:30:46,810 hurricanes. On Earth, our hurricanes usually only last a 471 00:30:46,900 --> 00:30:51,460 few weeks, maybe a month from start to finish. The Big Red 472 00:30:51,670 --> 00:30:56,260 Spot has been a hurricane in Jupiter's atmosphere that's been 473 00:30:56,350 --> 00:31:00,100 around for hundreds of years. What's really neat, though, is 474 00:31:00,250 --> 00:31:03,000 because we've now got telescopes that can look at Jupiter all the 475 00:31:03,120 --> 00:31:07,320 time and look at it at and watch the spot. It's changing its 476 00:31:07,440 --> 00:31:11,100 shape. In fact, it's starting to get smaller, and so maybe in a 477 00:31:11,160 --> 00:31:15,270 couple 100 years there won't be that big red spot. Part of the 478 00:31:15,330 --> 00:31:19,110 question was why is it red? The reason why it's red has to do 479 00:31:19,200 --> 00:31:23,090 with just slight differences in in the atoms that make up the 480 00:31:23,390 --> 00:31:25,850 atmosphere and slight differences in the temperature 481 00:31:25,970 --> 00:31:29,930 and the pressure of that, which can change the relative color of 482 00:31:30,140 --> 00:31:33,890 of that gas. But for me, it's it's kind of fun to know that 483 00:31:34,400 --> 00:31:36,710 you know for hundreds of years we've been watching a hurricane 484 00:31:36,800 --> 00:31:37,490 on another planet. 485 00:31:37,670 --> 00:31:38,450 Jane: That is pretty cool. 486 00:31:38,780 --> 00:31:40,690 John: And Jupiter has a couple of those. There's the big red 487 00:31:40,780 --> 00:31:44,080 spot, but there's a couple of smaller white spots, and and a 488 00:31:44,170 --> 00:31:47,620 and another smaller red spot. And then when you look at the 489 00:31:47,920 --> 00:31:50,950 poles of Jupiter, it's it's really weird because you start 490 00:31:51,010 --> 00:31:54,640 to see shape the shape around the poles that that look really 491 00:31:54,670 --> 00:31:57,640 neat. It's just Jupiter has all these storms in its atmosphere 492 00:31:57,700 --> 00:32:00,070 because it's so big and rotating so fast. 493 00:32:00,610 --> 00:32:04,860 Jane: Well, is its size also relevant when we think about 494 00:32:05,130 --> 00:32:06,270 Jupiter's moons? 495 00:32:06,510 --> 00:32:11,490 Brandon: Hi, my name is Brandon, and I'm 10 years old. I'm from 496 00:32:11,490 --> 00:32:15,600 Sydney, Australia. Why does Earth only have one moon, but 497 00:32:15,600 --> 00:32:18,120 Jupiter has 95 moons? 498 00:32:17,820 --> 00:32:21,582 John: This is a fantastic question, and and I want to zoom 499 00:32:21,654 --> 00:32:25,995 out and think about the solar system again for a little bit. 500 00:32:26,067 --> 00:32:30,480 Mercury doesn't have any moons. Venus doesn't have any moons. 501 00:32:30,553 --> 00:32:35,183 The Earth has one moon. Mars has two very tiny moons, Phobos and 502 00:32:35,255 --> 00:32:39,668 Deimos, which are kind of like asteroids. Then you get to the 503 00:32:39,741 --> 00:32:44,226 big giant gas ones, and those planets have dozens of moons. We 504 00:32:44,299 --> 00:32:48,784 keep finding new moons around Jupiter and Saturn every time we 505 00:32:48,856 --> 00:32:53,197 look harder. Uranus and Neptune also have a lot of moons, so 506 00:32:53,270 --> 00:32:57,538 there's something different just in general about the solar 507 00:32:57,611 --> 00:33:02,024 system, and it has to go back, it goes back to how that stuff 508 00:33:02,096 --> 00:33:05,713 formed. The rocky planets, the rocks came together 509 00:33:05,786 --> 00:33:10,127 gravitationally. Snowball effect made this this big this big 510 00:33:10,199 --> 00:33:14,757 planet. For the big gas giants, on the other hand, they started 511 00:33:14,829 --> 00:33:18,881 to build up stuff and then started capturing things into 512 00:33:18,953 --> 00:33:23,294 orbits around them. And those things, most of them got flung 513 00:33:23,366 --> 00:33:27,996 off, but some of them survived, and the planets were so big that 514 00:33:28,069 --> 00:33:32,337 the stuff orbiting it with it got pretty big, big enough to 515 00:33:32,410 --> 00:33:36,895 make moons. So it's kind of like Jupiter and Saturn and Uranus 516 00:33:36,967 --> 00:33:41,453 and Neptune are like their own little solar systems because if 517 00:33:41,525 --> 00:33:46,083 you look at the types of moons closest to Jupiter or closest to 518 00:33:46,156 --> 00:33:50,569 Saturn, they look different than the moons farthest away from 519 00:33:50,641 --> 00:33:54,982 Jupiter and farthest away from Saturn. So they're all acting 520 00:33:55,054 --> 00:33:58,744 almost like little solar systems, and that's just a 521 00:33:58,816 --> 00:34:03,374 that's a leftover feature of how the whole solar system formed, 522 00:34:03,447 --> 00:34:08,149 and again, we don't know exactly how this how this works. But the 523 00:34:08,221 --> 00:34:12,345 bigger the planet, the more stuff it's trying to pull in, 524 00:34:12,418 --> 00:34:16,903 and that's probably why Jupiter and Saturn have the most moons 525 00:34:16,976 --> 00:34:18,640 in in the solar system. 526 00:34:18,780 --> 00:34:20,810 Jane: All right. Well, since we're we're already talking 527 00:34:20,810 --> 00:34:24,590 about Jupiter and Saturn. Let's move from Jupiter to Saturn, the 528 00:34:24,740 --> 00:34:30,530 next one out. And a lot of kids and adults know one thing about 529 00:34:30,590 --> 00:34:30,950 Saturn. 530 00:34:31,129 --> 00:34:34,099 Christopher: My name is Christopher. I'm six years old. 531 00:34:34,489 --> 00:34:38,119 I'm from Buckeye, Arizona. Why does Saturn have rings? 532 00:34:38,900 --> 00:34:43,670 Aaron: My name is Aaron. I live in Boston, and I'm five years 533 00:34:43,670 --> 00:34:48,710 old. And my question is, why does Saturn have wings? 534 00:34:48,710 --> 00:34:52,880 Amelia: My name is Amelia. I'm from Princeton, New Jersey. I'm 535 00:34:52,880 --> 00:35:01,250 six years old, and why does Saturn have a ring around it? 536 00:35:01,960 --> 00:35:06,730 Libby: Hi. My name is Libby and I'm nine years old. I live in 537 00:35:06,730 --> 00:35:13,090 Pearland, the United States of America. Why does Saturn have 538 00:35:13,090 --> 00:35:14,080 rings? 539 00:35:14,180 --> 00:35:18,620 Arjun: Hi, my name is Arjun and I'm five years old and I live in 540 00:35:19,250 --> 00:35:23,900 Maryland. Why do some planets have rings? 541 00:35:24,709 --> 00:35:27,769 John: It turns out that all of the gas giants in the solar 542 00:35:27,919 --> 00:35:33,469 system-Jupiter, Saturn, Uranus, and Neptune-have rings. Saturn's 543 00:35:33,589 --> 00:35:36,019 rings are big and beautiful and easy to see, but Jupiter has 544 00:35:36,139 --> 00:35:40,099 rings. Uranus and Neptune-they they have rings, and we think 545 00:35:40,249 --> 00:35:44,949 that the rings came about because in the formation of the 546 00:35:44,949 --> 00:35:47,619 solar system, or in the formation of the planets, or at 547 00:35:47,829 --> 00:35:51,819 some point in those planets' history, stuff smacked into each 548 00:35:51,939 --> 00:35:54,939 other and pulverized. It hit each other really hard. So two 549 00:35:55,119 --> 00:35:59,739 things like moons or or giant chunks of ice bashed right into 550 00:35:59,829 --> 00:36:03,629 each other, made a lot of debris, but that stuff was 551 00:36:03,809 --> 00:36:08,009 orbiting around the planet, and so that debris made a disc which 552 00:36:08,189 --> 00:36:11,579 looks like a ring around the planet. So if you if you got up 553 00:36:11,639 --> 00:36:14,219 really close to Saturn, you know its rings are made out of pretty 554 00:36:14,399 --> 00:36:19,199 small stuff. It's mostly rocks and ice, but it's it's small 555 00:36:19,319 --> 00:36:23,239 stuff, and that's because something pulverized, Saturn's 556 00:36:23,419 --> 00:36:27,769 rings very likely don't look the same as they did hundreds of 557 00:36:27,799 --> 00:36:31,999 millions of years ago, and they may eventually go away because 558 00:36:32,149 --> 00:36:34,969 this stuff will start to clump together again, or fall into 559 00:36:35,029 --> 00:36:38,389 Saturn, or get thrown out. So that's another neat thing about 560 00:36:38,509 --> 00:36:41,559 about ringed planets is because they don't always look the same 561 00:36:41,769 --> 00:36:44,739 over time, right? Jupiter has rings now. It may have had more 562 00:36:44,799 --> 00:36:49,449 impressive rings, or or maybe no rings at all early on. And it's 563 00:36:49,629 --> 00:36:53,649 it's it's fun to try to figure out what the history of those 564 00:36:53,799 --> 00:36:58,779 things might be. We don't watch over short times like a month or 565 00:36:58,869 --> 00:37:03,389 a year or 10 years the changes in those rings. We have to use 566 00:37:03,839 --> 00:37:08,849 computers to simulate what those rings look like. It's kind of 567 00:37:08,879 --> 00:37:12,599 like we're playing Minecraft with the planets, and we put the 568 00:37:12,749 --> 00:37:15,149 rings there, and we tell them, "Here's how we think gravity 569 00:37:15,269 --> 00:37:19,349 works, and what moons are there. And then we let a pretend clock 570 00:37:19,409 --> 00:37:23,479 go really fast, and let the the thing go much much faster than 571 00:37:23,629 --> 00:37:28,309 than it does in in normal time, and we can test models of of how 572 00:37:28,339 --> 00:37:31,099 the rings formed, what might happen to them. The same thing 573 00:37:31,099 --> 00:37:34,789 is what we do with the solar system. So, going back to the 574 00:37:34,909 --> 00:37:36,979 original question, the main reason why we have rings is 575 00:37:37,039 --> 00:37:39,619 because we believe that stuff collided with other stuff and 576 00:37:39,649 --> 00:37:41,349 just left a bunch of debris. 577 00:37:42,880 --> 00:37:45,400 Jane: All right, so we're going from Saturn. We're still 578 00:37:45,550 --> 00:37:50,560 traveling out away from the sun, and the next planet is Uranus. 579 00:37:51,490 --> 00:37:51,640 John: Yes. 580 00:37:52,570 --> 00:37:53,710 Jane: So we have a question for you. 581 00:37:54,130 --> 00:37:54,280 John: Okay. 582 00:37:55,089 --> 00:37:58,839 Jane: We're not sure if this question is an honest question 583 00:37:58,929 --> 00:38:00,099 or said in jest. 584 00:38:00,330 --> 00:38:05,040 Prayun: My name is Prayun, and my age is five, and I'm from New 585 00:38:05,040 --> 00:38:10,620 Mexico. And my question is, why is Uranus so gassy? 586 00:38:11,610 --> 00:38:12,240 Jane: What do you think, John? 587 00:38:12,510 --> 00:38:16,050 John: I will do the answer, assuming that this is this is a 588 00:38:16,050 --> 00:38:19,320 non-un jest question. 589 00:38:19,320 --> 00:38:24,480 Jane: And and I I think a lot of kids know what the the joke is, 590 00:38:24,480 --> 00:38:28,830 but just to be clear, sometimes people call when I was a kid. I 591 00:38:28,830 --> 00:38:33,180 think we always called this planet Uranus, which is another 592 00:38:33,180 --> 00:38:36,510 word for your butt. So why is your butt so gassy? 593 00:38:36,555 --> 00:38:37,875 John: Why is your butt so gassy? 594 00:38:37,875 --> 00:38:40,125 Jane: Uranus, the planet is gassy. 595 00:38:40,219 --> 00:38:43,539 John: It is. It's a giant ball of gas. I could make the jokes 596 00:38:43,599 --> 00:38:46,989 all day, and maybe that's a different. That's a. That's a 597 00:38:47,049 --> 00:38:50,529 different podcast. But Uranus is one of those planets that's 598 00:38:50,589 --> 00:38:54,099 really far away from the sun, and so it built itself up the 599 00:38:54,189 --> 00:38:57,789 same way that Jupiter and Saturn did, with slightly different 600 00:38:58,509 --> 00:39:01,649 material because it was farther away from the sun. So if we used 601 00:39:01,709 --> 00:39:04,769 our units, where the Earth is one unit away, Jupiter is five 602 00:39:04,799 --> 00:39:08,969 units away, Saturn is 10 units away, Uranus is 20 units away. 603 00:39:09,119 --> 00:39:11,219 So now we're starting to get really far away from the sun, 604 00:39:11,969 --> 00:39:16,169 and so it was slightly different gasses that could form ices out 605 00:39:16,199 --> 00:39:20,929 of at colder temperatures, but it's still the same process that 606 00:39:20,959 --> 00:39:23,059 that ice is really good at capturing gas. 607 00:39:23,570 --> 00:39:26,570 Jane: All right, thank you for that. Appreciate it. 608 00:39:26,570 --> 00:39:26,810 John: Sure. 609 00:39:26,810 --> 00:39:30,290 Jane: So after Uranus, we keep going out. How many units to get 610 00:39:30,290 --> 00:39:30,980 to Neptune? 611 00:39:30,980 --> 00:39:34,910 John: Neptune is another doubling, if I remember 612 00:39:34,910 --> 00:39:38,450 correctly. So the planets keep doubling. They're farther away. 613 00:39:38,450 --> 00:39:42,050 It's I think it's about twice as far away as Uranus is. 614 00:39:42,050 --> 00:39:44,930 Jane: What do we need to know about Neptune? 615 00:39:44,930 --> 00:39:48,305 John: We need to know that Neptune is again because it was 616 00:39:48,305 --> 00:39:52,685 so much farther away. We're now having other types of gasses 617 00:39:52,685 --> 00:39:58,835 form ice. So out there, you can have a gas which is called 618 00:39:58,835 --> 00:40:04,745 methane on Earth, and methane on Earth is made by cow farts and 619 00:40:04,745 --> 00:40:09,005 other things in biology, but methane can also be made 620 00:40:09,050 --> 00:40:12,950 astronomically and geologically. Methane, when you get it really, 621 00:40:12,950 --> 00:40:16,760 really cold, can form into ice as well. And so, that far away 622 00:40:16,760 --> 00:40:20,600 from the sun, you know, it's it's not just water ice; it's 623 00:40:20,600 --> 00:40:25,430 it's mostly nitrogen ice. Like nitrogen can make ice, methane 624 00:40:25,430 --> 00:40:31,520 can make ice, and it's those things are are are what might be 625 00:40:31,520 --> 00:40:36,935 the the the seed units that captured the gas on on to to 626 00:40:36,935 --> 00:40:41,345 Neptune. What's fun about Neptune and Uranus is they also 627 00:40:41,345 --> 00:40:45,095 have these giant storms, kind of like the red spot on Jupiter. 628 00:40:45,095 --> 00:40:48,455 When we take very powerful telescopes, we can see these 629 00:40:48,455 --> 00:40:52,475 storms in the upper atmosphere of Uranus and Neptune. the The 630 00:40:52,475 --> 00:40:59,420 other interesting thing about Neptune is that it is one of the 631 00:40:59,420 --> 00:41:04,880 most common sized planets around other stars. We have things at 632 00:41:04,880 --> 00:41:09,350 around a Neptune size, and so it's kind of interesting because 633 00:41:09,350 --> 00:41:12,260 it's it's an interesting representative of of what other 634 00:41:12,260 --> 00:41:15,890 planets around other stars might, in general, look like if 635 00:41:15,890 --> 00:41:18,665 they were that distance from their from their star. But we're 636 00:41:18,665 --> 00:41:21,695 getting pretty cold out there. We've still got a lot of moons. 637 00:41:21,695 --> 00:41:26,645 We've got some rings, but you know the sun appears much much 638 00:41:26,645 --> 00:41:30,395 fainter. If you were if you were in orbit around Neptune and you 639 00:41:30,395 --> 00:41:32,945 looked at the sun, you wouldn't need to put on sunglasses or 640 00:41:32,945 --> 00:41:36,245 squint your eyes. It's now getting pretty faint, and so 641 00:41:36,245 --> 00:41:38,615 that gives you a sense of how cold it is out there. 642 00:41:38,869 --> 00:41:42,939 Jane: So Willow has a question about Neptune that we may need 643 00:41:42,999 --> 00:41:44,439 to do some redirecting around. 644 00:41:44,500 --> 00:41:50,740 Willow: My name is Willow. I live in Boone, North Carolina, 645 00:41:51,190 --> 00:41:58,510 and I'm five and a half years old. Why is Neptune too small to 646 00:41:58,630 --> 00:41:59,560 be a planet? 647 00:42:00,520 --> 00:42:04,200 John: Um. So Neptune is a planet. It's it's too small to 648 00:42:04,500 --> 00:42:09,330 be a gas giant. It's kind of in this this this transition space, 649 00:42:09,480 --> 00:42:13,020 but it's definitely a planet. It's just the smallest of the 650 00:42:13,200 --> 00:42:15,600 gas planets in our outer solar system. 651 00:42:16,110 --> 00:42:18,480 Jane: Well, I was wondering if Willow was actually thinking 652 00:42:18,660 --> 00:42:23,540 about another object that if we kept going past Neptune, we 653 00:42:23,720 --> 00:42:30,620 would get to, that was a planet, and is pretty small, and that's 654 00:42:31,070 --> 00:42:31,550 Pluto. 655 00:42:31,780 --> 00:42:37,210 Hazel: I'm Hazel. I'm five years old, and I live in Burlington, 656 00:42:37,210 --> 00:42:40,960 Massachusetts. Why isn't Pluto a planet anymore? 657 00:42:40,960 --> 00:42:46,120 Jasper: My name's Jasper, and I'm from Lanzhou, China. And I'm 658 00:42:46,120 --> 00:42:53,110 11 years old. My question is, why isn't Pluto a planet? 659 00:42:53,140 --> 00:42:58,000 John: The only reason that I think is a good reason to say 660 00:42:58,000 --> 00:43:01,270 Pluto isn't a planet anymore is because we have to come up with 661 00:43:01,270 --> 00:43:07,600 a definition that is consistent for what we say a planet is, and 662 00:43:07,600 --> 00:43:12,400 our definition for a planet has a lot to do with its size, but 663 00:43:12,400 --> 00:43:19,165 also to do with its environment. And Pluto doesn't quite match 664 00:43:19,165 --> 00:43:22,285 those conditions for any of the other planets in the solar 665 00:43:22,285 --> 00:43:26,575 system, Pluto is is very small compared to any of the other 666 00:43:26,575 --> 00:43:32,035 planets. It has a moon Charon, which is almost as big as it is. 667 00:43:32,035 --> 00:43:35,335 A while back, astronomers were struggling with the definition 668 00:43:35,335 --> 00:43:37,975 of a planet because if they allowed Pluto to remain a 669 00:43:37,975 --> 00:43:41,080 planet, then all of these other things that we were starting to 670 00:43:41,080 --> 00:43:46,570 discover in the solar system, like Ceres or Makemake, or you 671 00:43:46,570 --> 00:43:48,700 know, there's there are these things which we call dwarf 672 00:43:48,700 --> 00:43:53,500 planets, which are big relative to an asteroid, but small 673 00:43:53,500 --> 00:43:58,720 relative to other planets. Pluto was a lot more like those than a 674 00:43:58,720 --> 00:44:01,360 planet that we would traditionally call planets. So 675 00:44:01,360 --> 00:44:03,895 we changed the name. We we said Pluto is no longer a planet; 676 00:44:03,895 --> 00:44:06,895 it's a dwarf planet, and we have hundreds of dwarf planets in the 677 00:44:06,895 --> 00:44:08,035 solar system. 678 00:44:08,040 --> 00:44:11,340 Jane: John mentioned Ceres and Makemake, but the other 679 00:44:11,490 --> 00:44:14,280 officially recognized dwarf planets, other than Pluto, are 680 00:44:14,490 --> 00:44:19,710 Haumea and Eris. So, if there are five official ones, then why 681 00:44:19,860 --> 00:44:23,660 did John say there are hundreds in our solar system. Well, he 682 00:44:23,900 --> 00:44:26,570 and many other astronomers believe there could be hundreds 683 00:44:26,660 --> 00:44:31,610 or even 1000s of dwarf planets yet to be discovered. Full 684 00:44:31,700 --> 00:44:34,610 planet or dwarf planet? John says the real question about 685 00:44:34,670 --> 00:44:36,650 Pluto is: Is it awesome? 686 00:44:36,960 --> 00:44:39,330 John: It's totally awesome and interesting, and we flew a 687 00:44:39,330 --> 00:44:43,740 spacecraft past it called the New Horizons spacecraft, that 688 00:44:43,740 --> 00:44:48,420 saw things we just never seen before. We saw mountains of 689 00:44:48,420 --> 00:44:52,080 frozen nitrogen, right? A mountain range of frozen 690 00:44:52,080 --> 00:44:57,480 nitrogen on its surface. We saw this giant heart-shaped thing of 691 00:44:57,480 --> 00:45:01,125 ice on its surface, and so is it a planet or not, I don't care. 692 00:45:01,125 --> 00:45:03,945 It's still awesome, and it's and it's worth studying. 693 00:45:04,360 --> 00:45:06,490 Jane: All right. Well, we're pretty far out in our solar 694 00:45:06,490 --> 00:45:09,430 system now, and we've talked about all the planets and the 695 00:45:09,430 --> 00:45:13,450 dwarf planets. So I think we'd better end it here. But first, 696 00:45:13,450 --> 00:45:16,090 let's turn our imaginary super fast spaceship back toward 697 00:45:16,090 --> 00:45:20,830 Earth. As always, if you have a question about anything, have an 698 00:45:20,830 --> 00:45:23,770 adult record you asking it on a smartphone using an app like 699 00:45:23,770 --> 00:45:26,980 Voice Memos, then have them email the file to 700 00:45:27,325 --> 00:45:31,315 questions@butwhykids.org. But Why is produced by Sarah Baik, 701 00:45:31,315 --> 00:45:34,345 Melody Bodette, and me, Jane Lindholm at Vermont Public, and 702 00:45:34,345 --> 00:45:38,575 distributed by PRX. Our video producer is Joey Palumbo, and 703 00:45:38,575 --> 00:45:41,695 our theme music is by Luke Reynolds. If you like our show, 704 00:45:41,695 --> 00:45:44,335 please have your adults help you give us a thumbs up or leave a 705 00:45:44,335 --> 00:45:47,335 comment on whatever podcast platform you like to use to 706 00:45:47,335 --> 00:45:51,655 listen to us. It helps other kids and families find us. Okay, 707 00:45:51,655 --> 00:45:54,310 time to disembark. We're back at Earth. Thank you for listening 708 00:45:54,310 --> 00:45:57,310 to our tour of the planets. We'll be back in two weeks with 709 00:45:57,310 --> 00:46:01,420 an all-new episode. Until then, stay curious.