 Hi, everyone. Hello. And welcome to this curious kids' live event on the solar system, which I'm sure, as you all know, is the sun and the planets and other bodies that orbit around it. I am Miriam Frankel, and I'm the science editor for The Conversation, a job that's really fun, because I get to learn loads about science. And I think in all of science, my favorite topic is space. So I'm very much looking forward to this. Curious Kids is a series of events and articles run by the Conversations. And in the articles, we normally get world experts to write answers to questions that children sent to us. And in my opinion, there are some of the best questions we get. But today, we are doing things a bit differently. So we've got experts here with us to answer your questions live. So thank you very much for joining us, and a special thank you if you have sent us a question. And if you haven't, but you think of one while we're talking, feel free to type it into the little chat box, or you can ask your parent or your teacher to type it for you. And we will do our best to answer it. So yeah, to kick off, I'm joined today with two experts on the solar system. That's Professor Monica Grady from the Open University and Dr. Jakob Van Loon from Keel University. And so to get going, I'm just going to ask them a little bit about what they know about the solar system. And then we'll start with the questions that you've got. So first of all, we've got you, Jakob. You are an expert on stars, like our sun. Is that correct? Yeah, so it's great the sun is shining, but actually it will come to an end. So I study what happens when stars die. And actually, we should be thankful that stars die, because the material that they produce then becomes available to make planets like the Earth. So the Earth could only form because stars died before. So I studied that process and what happens to the material when it enters space. Fascinating. And then we've got Monica, who is an expert on space rocks known as comets, asteroids. And am I correct in saying that you're so good at space rocks that you've actually had an asteroid named after you? Is that right? Yes, I have, which is really great fun. I study meteorites, which come from asteroids, which orbit the sun. And I take over, I take up where Jakob leaves off. So he's all about stars and how they throw material out when they die. And I look at how the solar system and other planetary systems form from that dust. When Jakob is quite right, the Earth wouldn't exist if stars hadn't died. And we wouldn't exist if stars hadn't have died. So it all adds up together. It's really, really exciting. So Monica, while I've got you then, the one question is actually about asteroids. So I thought it might be good to start with you. It's Jemima, who is in year three, and she wants to know how fast do asteroids travel? Oh, great question, Jemima. Well, they travel very fast, very fast indeed. Much faster than you can perhaps imagine. The fastest speeds we're supposed to go on our roads is 70 miles an hour. Asteroids can go 40,000 miles an hour. That's about 18 kilometers every second. So that is pretty fast. Amazing. Right, so if we move on to you, Jakob, we've got another question from Adi, who's nine, who wants to know what would Earth look like if it was moved to a different place in the solar system? Oh, well, that's another great question, Adi. So, well, it depends which way you want to go. Do you want to go towards the sun? Let's go there first. Obviously, it will get a lot hotter on Earth and, of course, brighter as well. If you move the other way, it gets a lot colder and darker. So that will change, of course, completely the Earth's atmosphere. If it gets too cold, the thing will freeze out. If it gets too hot, then, of course, we can't survive. And at what point? But also, one thing that will change is that when you go third out, it takes a lot longer to go around the sun. It also goes slower. So the year is just going to be much longer. And if you go inwards, it's going to be much shorter. So it's going to change the cycle of life on the Earth as well. And just to follow up, I mean, is there, if we had an enormous rocket, could we actually move the Earth? Yeah, well, if you've got a big enough one, but gravity is, we call it a weak force, but actually it's a really strong force. So it takes a lot to move against gravity, or it takes a rocket to leave the Earth. So you can imagine if you wanted to move the entire Earth, and not just a little piece on top of a rocket, it's going to mean many, many rockets or a very, very big one. So that's technically not feasible to do. So you want to try to do something smarter than just build a big rocket. And perhaps build something that can, say, harness the energy from the sun and then pull at the Earth, because there's much more energy in the sun. True. OK, we'll think about moving the Earth some other time. We've also got two questions about the moon. So I might go back to you, Monica. I'll tell you both of them. Miles, who's six, wants to know what would happen on Earth if the moon exploded? And Torben, who's 10, would like to ask what it's like to, what it would be like to skateboard on the moon. Ooh. Right, what would happen to the Earth if the moon exploded? Well, it's really strange. But probably life would die out on the Earth. Now, that might sound a bit odd, because we see the moon, we know there's nothing there. What the moon does, it helps control the wobble of the Earth. So the Earth is going around the sun like that, but it's not going around just like that. It sort of has an axis that wobbles. And the moon makes that so it doesn't wobble backwards and forwards like this, but it only wobbles a tiny little bit and you can't see the wobble. So without the moon, that wobble would be too much. It means our spring and our summer and our autumns and our winters would all sort of go absolutely crazy. And the tides, which is from the seas, the oceans, that the moon helps to control. They would be just like all over the place and we probably wouldn't be able to cope. So without the moon, there might be no life on Earth. Now, what would it be like to skateboard on the moon? Well, I think first of all, it might be a bit rough. I might be a bit difficult because the moon is covered in a surface of very fine dust. There's a lot of powdered moon rock there. And so first of all, you get your skateboard wheels jammed. The other thing, though, is if you actually could find a flat and smooth place to skateboard, because the gravity is much lower than on the Earth, you're not held so much. So you'd sort of go, woo, and you might sort of be able to do really great big wheelies and half-pipes or whatever the skateboard terms are. Yeah, but when you come down again, you might come down with a bit of a bang. So you'd be able to jump higher, but it might hurt a bit more when you land. Excellent. We have got some questions in, as we've been speaking. I'll get to them in a minute. I'll just have two questions about Jupiter. Maggie, in year three, wants to know whether Jupiter is made of rock. And Alexander, in year three, would like to know how far away Jupiter is. Jaco, would you be interested in answering that? Yeah, yeah, sure, I'll take that one. That's interesting, because Jupiter is enormous, and then the question is, why is it enormous that's so much bigger than the Earth? That's because the way it's formed, so it's got a lot of stuff on top, which the Earth didn't get. And then that makes it actually almost a star. It's just not big enough to become a star, but it's pretty similar in terms of the composition. So it's mostly hydrogen and helium on top. But what's in the very core, it's still a little bit of a puzzle, but the pressure is enormous there. So it is certainly something that's very solid, and we call it metallic. So it might have started off with a bit of rock early on, but at some point, so much stuff got dumped on top of it, and it became what it is now. The other question, how far is it from us? So it depends a little bit, of course, because we go around the Sun, it goes around the Sun. So sometimes you're on the same side of the Sun, and then it's a bit closer to us than when Jupiter is on the other side. But Jupiter goes around the Sun about five times further away from the Sun than we do. So it's quite a long way out, yeah. So we have sent probes there, but we haven't traveled there ourselves yet. Yeah, apparently it's about 800 million kilometers away. So that's really far. You get quite tired after just walking a few kilometers, isn't it? Right, so let's continue with one more question about comets. Well, first one about comets specifically. Where do you know, asks Charlotte, where comet ice comes from, or where do you think it comes from? Ooh, shall I answer that one? Yeah. Well, we think that the comet ice was always here when the solar system was made. So the solar system was made from one of these clouds of gas and dust that Jaco was saying has got bits of dying stars in. And when our solar system formed, that dust clumped together and the gas, which is mainly hydrogen, and made the Sun and the planets. And the further out you got from the Sun, the colder it was. So and the colder it still is. And so ice could form out there. So this is ice, which has come from the original cloud that made the solar system. And so that's where all the comets are. They're at the, most of them live at the outer edges of our solar system. And they come in to the center of the solar system occasionally and they orbit the Sun on really, really long elliptical orbits. And so the comet ice is associated with our solar system. But it actually is even more exciting than that really because if you go back to when everything was made, which is something called the Big Bang, and that's when all the atoms, the electrons, the protons, the atoms, everything eventually got made. And the first element to move aid was hydrogen. And of course, there's hydrogen in ice, in water. And that hydrogen has come all the way through time from the Big Bang, it gets changed, it gets moved into stars and outer stars and into stars and outer stars. But that hydrogen from the Big Bang is in comets. And it's also in the water that comes out of your tap. So when you have a drink of water, you're drinking hydrogen, which initially was formed in the Big Bang. Amazing. Going back to this sort of grander scale, we've got Nicola who wants to know, where is our nearest black hole? Now, is it in the solar system, Jaco? I hope not. The answer is, of course, that black holes are very difficult to spot because they're black, right? And if they're not very big, you wouldn't notice until you're quite close and you feel the pool from the gravity. But there have been several experiments trying to find many of these small black holes and that they haven't found any. So we're pretty sure black holes are pretty rare and it will be, unfortunately, accidentally run into one. So the nearest black holes we do know of, they are so far that the lights take thousands of years to get to us. And they formed as a result of the death of a massive star. And then there's an even bigger one, which is even further away. So it takes 25,000 years for light to travel all that way. And we are going around it, so we're never getting anywhere close to it. So we are safe. Will our sun one day turn into a black hole? No. So to make a black hole, you have to really be extremely massive when you collapse. And the sun is just not massive enough to do that. So it will stop. It will become a quite dense clump because it's a white dwarf, but it's not going to make a black hole. Great. Another question that is probably quite hard to answer is from Miho Maiho, who wants to know how many planets are there in the universe? Lots. Can we try to, I don't know. Narrow it down a bit. Would you like to answer that one, Jack? Well, yeah. So the answer is we don't know because we actually, we don't quite know how big the universe is. But that's an easy way out, right? So we do know now that, although it's difficult to find planets around stars, it's still hard to work. Pretty much all stars have planets and a couple of them. So planets are very common. And as Monika explained, the way the stars and the planets in the solar system form is it's quite universal process. So planets are there. It's just leftover stuff. So there are plenty of them. Of course, the question is whether they're interesting. If there's anything interesting going on on them. And there might be far fewer of those. Okay. Well, that was informative. If you want a number. If you want a number. So in our Milky Way Galaxy alone, there are a few hundred billion stars. And so there's many more stars than there are people on the Earth. And if all of those stars have a few planets, it's a trillion planets in the Milky Way Galaxy alone. That's just our galaxy. There are billions of galaxies. And how many zeros are there in trillion? That's 12, right? That's a lot of zeros. Yeah, many, yeah. A big number. Right. So Josh would like to know, maybe Monica can answer this one. What would happen if Earth had 20 times more gravity? Ooh. You'll be very, very small. Tiny. We wouldn't be able to grow. Everything would be like compressed. So our shapes would all be different. It would be, can you imagine? You know, your heart has to work very hard, pumping blood up into your brain, you know, because you're standing up. And so just imagine if it had to work 20 times harder to pump blood around, it wouldn't be able to do that. So we've gradually developed to be smaller and smaller and smaller, you know, all the trees and everything, the same thing would happen. They would be very, very small. Everything would be like crawling along, probably very, very slowly. It would feel as if you've got great big bricks attached to your feet and you wouldn't be able to lift them up and move. It would be really, really difficult. Won't be very nice, Tom. Yeah, no, thank God. So we've also got a very complicated question here from Oscar, who would like to know, is the great filter theory for real? So maybe, yeah, you can explain that but also tell us what is the great filter theory? Yeah, so the great filter is the idea that for life to develop, it sometimes encounters obstacles and it may be very hard to continue developing pastos. So for instance, on the earth, life has started very early and we don't know how common that is but it might well be very common because the ingredients we find all over the place, Monica finds them in meteorites and comets. So it's quite common, but it took billions of years before we finally got something more interesting like flowers, birds, ourselves, if you find us interesting. So somehow that was not so trivial. There was something that took ages to happen and that is one great filter. And then of course, a very interesting question is, is there a next great filter we're going through and is that perhaps a filter of our own doing? So this may explain why we still haven't found any technologically advanced civilizations like aliens in the universe and there might be out there but perhaps there are so few because they haven't been able to pass that great filter. Ah, that's why they're not been, we've not got any messages. A question from Selena is, how far away can you see the sun, Monica? Oh, well, you can see the sun from at least 150 million kilometers because that's where we are on earth because we must never, ever, ever look directly at the sun because you burn your eyes out. It's so bright. Now, if you go as far away as Jupiter that we were talking about before, if you could stand on Jupiter, which you can't because it's made of gas, but if you could, you would still be able to feel the influence of the sun. You'd only be able to see it as a tiny dot just looking like any other star, but you would be able to feel its influence in terms of the wind that comes from the sun. It's not like the wind that blows the trees, but you can't see it, but you can detect it. And so we have this solar wind. So you would be able to experience that. You can certainly see the sun on Mars because we've seen pictures from the Martian rovers that are there where they can see the sun. It looks smaller and it looks a bit sort of mauve-y purple color. If you go out to the next planet there, which is Jupiter, it becomes so small. It just looks like a regular star. Excellent, back to stars. Sorry, Jaco. Yeah, I just can follow up on that. So if you were to place the sun at about 50 light years, so it would take 50 years for the light to arrive, then it appears as more or less the faintest star in the night sky that you can see. So when you look up at the night sky, those stars, they're really quite close by. And in relation to that, Georgie has actually asked how many stars are there in the universe? And we only see a few of them, but it looks like millions. Yeah, as I said, in the Milky Way Galaxy alone, there are a few hundred billion stars and many of them are a bit like the sun. And the Milky Way Galaxy is just one of the billions of galaxies. We can only see part of the universe, so we don't quite know how many more galaxies there are than the ones that we can see. But you asked me how many zeros there are in a trillion. So I had a couple more to get the number of stars in the universe. Amazing, and it might be too many to count. Too many, we won't have a word for it. There is an estimate that there are more stars in the universe than there are grains of sand on the shore. And if you ever go to the seaside, and if we're ever allowed to go to the seaside again, although you might live there, if you pick up a handful of sand and just look at it in your hand and think, I can't count all the grains of sand there. And that's just one handful on one beach. And you think of all the beaches in all the world. It's just an unimaginable number. I can't imagine it. Yeah, no, impossible. Back to something a bit more easy to understand, I guess. And that is, what temperature is it on the moon? Louie wants to know, wants to know. Well, sometimes it's really, really cold, sometimes it's quite hot. The temperature on the earth is regulated by our atmosphere. Because there's no atmosphere on the moon at all, no atmosphere there. So the sun, when the moon is on the side of the moon that's turned towards the sun, the sun beats down on it, and it can get very hot there. But the rest, when it's turned away from the sun, it's bitterly, bitterly, bitterly cold. So you actually get quite high rises and falls in the temperature. It doesn't get hot enough, we don't think, to boil water on the moon. But it gets plenty warm, but for very short periods of time, because the heat is radiated away very, very quickly. Great. So we need a lot of equipment with us to go live there. Nadia would like to know, what happens if you fall into a black hole? Jaco? Yeah, so actually, astronomers invented a word for that, it's called spaghettification. So when you get close to a black hole, now if your toes are just a little bit close to the black hole, then your nose, you're going to get stretched out. And that's not gonna feel good. So I added something to that, because if you get stretched out completely and to pieces, then you'll make a nice volume near the source on it. So that's what's gonna happen. So you're gonna pass out. And then once you're disappearing in the black hole, of course there's no way out. Yes, indeed. That's it, the end. What makes, what is the space highway? Nicola wants to know, Monica, do you know that? No. No, me neither. How about you, Jaco? Not entirely sure, but if you're thinking of a route to take to, for instance, other planets in the solar system, there are preferred routes. So you could call that a highway. And this is the reason why, for instance, last summer there were a couple of missions to Mars because it's the right time to do that. It takes less fuel. So they all went one after the other and sort of sticking the same path to get there. And that will only happen again in another two years' time. So you could call that a space highway, if you like. I did find here a news story which says a new super highway network running through the solar system has been discovered by astronomer and it could speed up space travel in the future. It allows objects to move through space much faster than previously thought possible. For example, traveling between Jupiter and Neptune under a decade. Well, you can make use of the motion of the planets around the sun and we have been doing that already to get a bit of a swing and then you go faster and get using less fuel. You tap a bit out of that gravitational energy. We talked about gravity being so strong so there's a lot of potential to get energy out of that. And that's what you do if you're clever. Recently, people have been thinking more about using the light from the sun as I alluded to. Especially if we wanted to travel out of the solar system at great speeds to go somewhere interesting, say a nearby star, which would take very long. So you want to get a really high speed very close to the speed of light. You could possibly do that by using the sun's light. Okay, that sounds like an interesting proposal. Back to the solar system and maybe a look beyond as well. Abraham would like to know what could be the next habitable planet? So say we wanted to live somewhere else or we were looking for other habitable planets nearby or far away. Monica, what do you think? What's the best option? Well, I think we're hoping it might be Mars. That's why we're sending so many probes there. The Perseverance probe, which landed last week. That is going to look for signs of life. It's going to try and see if it can see any fossilized life. Mars should have had life when it formed. It formed at the same time as the Earth. A very special number, four, five, six, seven million. All right, so the Earth and all the planets in the solar system and the sun, they formed 4,567 million years ago. And when the Earth formed, it was far too hot to have any life on it, but Mars was just right. So life should have got going on Mars and there might be traces of it there still today. So that's what Perseverance is going to look for. Other places though, where there might be life. There's one of the moons of Jupiter is called Europa and it's covered in ice and below that ice is an ocean and something keeps that ocean liquid. And heat comes from the bottom of the ocean floor in sort of vents and produces hot water which circulates. And it's possible there might be life at the bottom of Europa's ocean. We don't know. It's not like fishes. Satellite, not so much like fish but things like tube worms, they're called and crabs. So there should be crabs. There won't be any plants because there's no light there for them to synthesize, but there'll be animals which is a really cool thing. It's going to take us quite some time to find that out though because it's going to be very difficult to get to the bottom of Europa's ocean. Yeah, you have to go through a lot of ice, don't you? Can we just say we're talking about a habitable planet. So I mean, which of these places would be the best place for humans to move to that would be hospitable for us? Right. Well, I think the best place in the solar system for humans to live is the Earth. For us to live here safely, we've got to make sure that we deal with climate change. We have to make sure that we keep our Earth suitable for us to live in. Because Mars, there's a question in here about why doesn't Mars have an atmosphere? Well, Mars doesn't have an atmosphere, it's very thin. It's only about, it's about just over a thousandth, 6,000 of our atmosphere in pressure. So we can't breathe it and there's no atmosphere on the moon. Venus is too hot, Mercury is too close to the sun, Jupiter and the giant planets are too far away. The Earth is in the just right place. Mars we could probably go to, we could make a habitat but I don't know whether we would want to live there. We might have to travel beyond the solar system to find a planet like the Earth which is orbiting a star, maybe like the sun. But at the moment, the best place in the solar system is the Earth. Well, that's good as we're here and hopefully we'll take care of it. Let's move to, oh, this is an interesting question. So Julio wants to know, does dark matter, dark matter, so invisible matter that's out there that we don't know what it is, does it affect the solar system? Jaco? So dark matter is something mysterious. It's because when we look at how things move around in the universe, they move faster than we can explain with a pool by stars. And that's why I think that there's dark matter to add to that. But we only see that when we look at very large things like galaxies, for instance. So at the scale of the solar system, you don't notice that, even though it might be here. So it doesn't affect the solar system directly. But of course, the solar system lives in the Milky Way galaxy and the Milky Way galaxy as a whole has got that dark matter in it. So without it, the Milky Way galaxy itself would be a little bit different and we might be somewhere else in the Milky Way galaxy. And so that may well have been important for us. I realize that we are nearly running out of time, but I'm gonna, we can squeeze in a few more, right? So just really briefly, Monica, why does Jupiter have a big red spot, Helen wants to know? Well, it's a bit of a mystery. I mean, Jupiter has weather systems like ours. So when you think of the earth and the way the winds move, we have different belts of winds, which is why it's very windy in some parts of the world and not so windy in other parts of the world. And Jupiter has the same sort of weather patterns and it's thought that the great red spot is just a massive, massive, massive weather system, which is so enormous. I mean, it's a weather system, which is bigger than the earth. It is changing and it is moving and it is rotating. We don't know whether one day it'll disappear or whether it will still, you know, how it appeared, how it happened. It's a bit of a mystery. We don't know, but there is a probe, which is going to go to Jupiter, which is going to look very closely, much more closely than before at some of those weather systems. It won't go down into the atmosphere, but it will observe from above. So I'm afraid I can't answer your question. That's a good thing. That's a good thing. We'll have to keep researching. It's still mysteries for us to answer. Jaco, very briefly, what happens if a planet crashes into another planet? Alex wants to know. It actually probably happened to the Earth when it was really young, something like the size of Mars bumped into the Earth and kicked out stuff that then became the moon. So it does happen, but only early on, because now the planets move around in quite regular, almost circles, so they don't come close enough to bump into each other. But it wouldn't be good, no. If you think about what happened to the dinosaurs 65 million years ago, that was an asteroid, maybe 10 kilometers across, maybe a little bit more than that. So imagine a planet, maybe a few thousand kilometers across or more, it will completely destroy the surface of the Earth. So why not just some cute animals, but everything? I completely agree with Monika. This planet is really precious. We have to preserve it. We can't do very much against another planet running into it. So I say the planets in the solar system go around in circles, but the ones we have to be careful about is the rogue planets that come from outside. And we already discovered an asteroid and a comet that came from outside the solar system. So those you have to be much more careful about. Hopefully there won't be many of them. No, and they are monitoring, aren't they? So hopefully you can catch them. Okay, so I think we'll have to pick one final question. And I think a good one to end with is Timmy's question. What happens if you pee in space, Monika? What happens if you pee in space? You get towed off. We don't want to talk things like that. What happens is the water will evaporate straight away. I mean, some of it might freeze instantly, but then I'll go whoof, because there isn't enough atmosphere in space to keep it as water. So it might get cold. Well, it will get cold. It will turn into ice. And then it go whoof, and something disappeared. Very good. Now we know that was a very good question to end on. I would just like to thank you all for joining us. And I think we've answered most of the question. There might be a few that we didn't get to. So if you have a question that we didn't answer, you can send it to us, and we can answer it in the Britain version as part of Curious Kids, or you can get Googling and find out. But I really hope you all continue to ask questions as you've had some really good ones, and I've learned a lot. And I'm sure Jaco and Monika really enjoy that. So yeah, thank you, everyone. Have a wonderful day, and we hope you join us again for our next future events, Curious Kids events. All right.