Responding to your science questions

BBC Sounds, Music Radio Podcasts. Their company's success helped build a nation. The company is such a big part of Korea's economy. But who are the family behind one of the world's tech giants? They often say, look, we built the nation and without us, South Korea as it exists today would simply not be here. Inheritance, Samsung explores the real-life dramas of the Lee family and their company. They are the equivalent of royalty. Listen first on BBC Sounds. Hello and welcome to Inside Science. Now, what I love about making this programme is the ability to really explore any aspect of science and to try to understand how it's shaping the world we live in. We've discussed everything from dark energy to food additives here. And we do our best to demystify without skimping on fascinating and important detail. And today, we're looking to you, our lovely, curious-minded listeners, to tell us what you want to hear about. What questions would you like some scientific insights into? Real human scientific insight, not something an algorithm has scraped off the internet. And to that end, we have a wonderfully clever group of humans in the studio today to answer your quandaries, as many of them as we can get through. Could you please introduce yourself, science panel? Hello, everyone. I'm Catherine Hamons. I'm the Astronomer Royal for Scotland, and I'm also a professor at the University of Edinburgh. And I'm Mark Mazin. I'm a professor of Earth System Science at University College London, which means that I'm very lucky I've studied climate change in the past, the present and the future. You have to say it like that, otherwise it doesn't sound good. And I'm Penny Sarchi. I'm managing editor at New Scientist. Before, as a journalist, I was a biologist, and my doctorate was in plant science. Well, thank you, all of you, for being here. We have quite an array of specialisms, don't we? So, are you all ready to tackle our listeners' questions? Yeah. I'm daunted, as always. So, I'm going to play to each of your scientific strengths. I'm going to direct a listener's question to a particular panelist. But if anyone wants to jump in, argue, contradict, criticise, please do. And if you want to throw an account point or perhaps take us on another fascinating tangent, we're here for it. And I should say some of our questions have been voiced by our producer, but this first recording comes directly from one of our listeners. Ian Hamilton from Dunbar in Scotland. I've heard it said that we're heading for a reversal of the magnetic poles. How quickly will this event take place? And will it mean that the Earth's shields against radiation are down for a significant time? I wonder what the risks to life or the ozone layer are from the predicted cosmic radiation will suffer while this is happening? We are getting straight into it. And, Mark, as an Earth scientist, this feels appropriate for you. Oh, absolutely. And it's one of those things that I've been very lucky to study, but also use, because those reversals in the magnetic field allow me to date sediments. So I'm on top of this. So the first thing to say is that the North Pole and the South Pole of the Earth aren't the same as the rotational axis. And also the North Pole is not really a North Pole. It is the pole that the North of a magnet points to. So technically, the North is actually a South Pole of a magnet. I know students look at me and go, really, did you have to confuse me like this? So the reason we have this magnetic shield is because the center of the Earth, the core, is solid iron with a little bit of nickel. And around it is the liquid iron, again, with a little bit of nickel. Because the Earth spins so fast once every day, that liquid is spinning around the metal, creating this magnetic shield around the whole Earth. Now, what's interesting, and I'm going to throw this to Catherine, is because the Earth has a magnetic shield, but our sisters, Venus and Mars, don't. We're heading into space, Catherine. He's right. So Venus doesn't spin very far. So the magnetic field comes from a combination of both that liquid metal in the core and the spin of the planet. And because Venus is moving so slowly, you don't have a strong magnetic field. Mars has a smaller liquid core, but there's lots of discussion about what does the moon have something to play in the magnetic field of the Earth? Lots of discussion. The key thing, though, is that Earth does have a magnetic field, because if we didn't, then Earth would be like the barren landscape that we see on Mars. Four and a half billion years ago, Mars did have a magnetic field. It had an oxygen-rich atmosphere, water on the surface. And then the magnetic field ended, and you wouldn't want to visit there now. Very important for life as we know it, which brings us back to the question of the reversal. So Ian is absolutely right. Every so often, the Earth's magnetic field flips. So the South Pole becomes the North Pole, and the North Pole becomes the South Pole. And this is what I find fascinating, because it's the only truly random thing that we know in nature. So the reversals can happen on a 10,000-year timescale, or over 10 million years. The last reversal was about 780,000 years ago. So we have no way of predicting the next one. So when Ian says, is the next one coming? No idea. It could literally happen tomorrow or in 10 million years' time, which frustrates me as a scientist. And that's because of the complexity of the fluid dynamics and the interaction between the inner and outer cores. So the other question then is, how quickly will it happen? Well, this is where science doesn't agree. So some people have argued that this flip occurs within the length of a human lifetime. OK, so about 50 to 100 years. Others have suggested it takes thousands of years. So then we flip back. So did it have a huge impact every time it happens? No. So we looked at geology. We look at the records. There's no mass extinction. There's no change in plants. There's no change in animals. So it doesn't seem to have that impact. But this is where Ian is absolutely right. It will have a big effect on human society, because if you reduce the strength of the magnetic field, a lot more cosmic radiation gets through. And that's going to actually affect all our electronics. Solar flares we know can interrupt our electronic communications, but this would be on a much bigger scale. So life would not really notice and carry on. Maybe a few birds might get lost, but our society would be really, really affected during the flip. But for human lifetime, probably not going to have that much issues. Thank you very much, Mark. And thank you to Ian for your question. And now from magnetic fields to molecules, a question that's come directly from the classroom from 16 year old Laurie. This is something that rang familiar to me from secondary school biology. And I think it might be one for you, Penny. It's voiced by our producer, Ella. Hi, Inside Science. I have a couple of questions about chlorophyll. So I learned in biology that plants have green leaves because of the green chlorophyll pigment where photosynthesis occurs. So what is going on in plants that don't have green leaves? And why are they so much less common than the green ones? Also, do other green bits of plants have chlorophyll or are they green for a different reason? Great question, Laurie. Penny. Great plants science. Yes. So, yes, essentially all land plants have chlorophyll. The only exceptions, which are cool, so I'm going to mention them, are things like parasitic plants. So you get these orchids sometimes in jungles that are completely colorless because they just steal all their energy from other plants. Aside from that kind of weird oddity, everything has chlorophyll because it's the main pigment for doing photosynthesis. So I'm trying to imagine the kinds of non green plants you might see out and about. Near me in front gardens, there's a lot of purple smoke bushes, purple elders. So what's going on with the purple plant is that you've probably got something like anthocyanins in there as well. And these are, you know, we eat things like blueberries to get anthocyanins. They're antioxidants. They're really good and useful and protective. And plants use them in the same way. They're not actually a photosynthetic pigment. And so what's going on when you're looking at a purple plant is there's still loads of chlorophyll in there. You just can't see it because it's getting masked by the purple color. So to answer your question, yes, green is sort of the default, but sometimes more rarely you'll see another color over the top of that. And that's being used for something else. Or in the case, probably a lot of what you see out and about, it's been bred in by plant breeders because we just like things to look a bit unusual. And then in terms of why is the stem of a plant green? Yes, anything that's green can photosynthesize. And the sort of logic there is that you want to harness as much energy as you can from the sun. So you might as well put your chloroplasts, which do photosynthesis anywhere that light is going to hit. And so, yes, you can have photosynthesis happening on any above ground bit of a plant. But the reason that leaves evolved was to make it just that much more effective and efficient. So rather than just trying to get what you need through the stem, you've got these beautiful organs, a key innovation and evolution. Lovely. Thank you very much, Penny. Now, Catherine, we have a question for you that involves some astronomical time scales. So I think this is one you're going to be able to help us with. Here it is. My name is Linton Guest and I live in Beereges, Dorset. Scientists tell us that as a result of the expansion of the universe, all galaxies are moving away from each other in all directions. However, we are also told that our own Milky Way and the Andromeda Galaxy are on a collision course and will merge at some point in the distant future. How can both of these positions be true? Catherine, expansion and merging. How is this possible? It's an excellent question from Linton. So let's start off close to home with our own Milky Way galaxy and its neighbour Andromeda. Linton is right that you are normally told that in about five billion years, these two galaxies are going to collide because when we look up at Andromeda, we see that it's moving towards us. But actually, the latest study has shown using data from the European Space Agency, Gaya Satellite, that there's actually only a 50-50 chance that they're going to collide with each other in the next 10 billion years. But nevertheless, they are moving towards each other, which is the opposite of what's happening when we look out at very distant galaxies. So the distant galaxies are all moving away from us. It looks like we smell really bad in the universe and everything's etching away. But actually, that's true for every single galaxy. So long as you're looking on the large scales, everything's moving away from us because our universe is expanding and that expansion is getting faster and faster each and every day thanks to something that we've called dark energy. We don't really know what dark energy is, but it is fueling the accelerated expansion of our universe. So there are two things at play here. On the very, very large scales in the universe, you've got dark energy expanding the universe at an ever-increasing rate. But when you look on smaller scales, like our Milky Way, Galaxy and Andromeda, what's governing the motion there is another dark entity called dark matter. Now dark matter is a strong gravitational force in our universe. It likes to pull matter together and it's gravity that's pulling the Milky Way towards Andromeda. And indeed, if you look at galaxies close to each other in the universe, they are often pulling towards each other. Galaxies often live in groups or galaxy clusters. And so the answer to Linton's question is just a case of scale. On small scales, galaxies tend to move towards each other, but on the very, very largest scales, everything is moving away from each other. The competing, warring siblings of dark matter and dark energy at play. Thank you, Catherine. That was an amazingly succinct answer on a very expansive question. And I think going from dark matter and dark energy at war to this next question really does epitomise the breadth of topics that we cover on this programme. This comes from Marie in London. I am 80 this year. After all these years, I still wonder, why do men have nipples? We'll be glad to be informed should you take this subject on. Marie, we have taken on the subjects and I'm looking at you, Penny. We've got listeners from 16 to 80 years old asking questions from chlorophyll to male nipples and I'm coming back to you. Brilliant. So go for it. Biology throughout the time course of life. Exactly. Yes, so this is because when a male or a female body is being built in the womb, they're actually extremely similar and they're using what is essentially the same genetic blueprint. Especially during that first month or two of embryonic and fetal development. And it's actually quite complicated to evolve features that only one biological sex will then have because you're using the shared blueprint. So there are things for which it's worth evolving that. For example, if you have ovaries and testes, they're going to get in the way of each other and hamper your ability to reproduce. However, having nipples on a male body doesn't really seem to come with any kind of disadvantage. So we basically just haven't evolved a way to stop that from happening. There are even possibly hints that there might be an advantage. I did see one study suggested that the nipples might actually play a role in sexual arousal in men. So maybe there is a use for them after all. So it may be useful, but they certainly don't get in the way. Yes, exactly. And one thing you do sometimes hear people say is that everyone starts off as a sort of default female in the womb and then some then become male when certain genes kick in. But that's not quite true. Those first few months, every fetus is basically sexually undifferentiated. And there are little clusters of tissue or cells within that fetus that could go either way, it could develop into a female organ or a male organ, depending on later on. Well, thank you, Penny, for taking on the gamut of biological questions, therefore. Thank you very much, Marie, for your question. You're listening to Inside Science with me, Victoria Gill. And this week, we've turned the show over to listeners curiosity. We're helping to provide answers and we have Penny Sarche from the new scientist, Catherine Heymans from Edinburgh University and Mark Maslin from University College London here to answer all those questions. Now, we have come back to the problem of plastic pollution many times on this programme, looking for scientific solutions to this global scourge. And of course, even the term plastic encompasses many different types of material, but we have a query about recycling. And I think this is one for you, Mark. Hi there. My name's Anne from Travegluis in Montgomeryshire. Like millions of other people, I carefully collect every scrap of soft plastic and take it back to the supermarket. My question is, what happens to it then? Is it recycled? And if so, into what? Is it incinerated for heating or electricity generation? Or is it simply centre-broad for recycling or dumping? I don't think it's a simple answer to this question, but can we start with what we mean by soft plastic, Mark? OK, so soft plastic are all those wrappers that you have, whether it's on bread, whether it's on crisp packets, your bin bags. It's in the name. They're soft. And they are much harder to recycle than hard plastics. And we have advanced technology that can transform the soft plastics. And what you have to do is you have to break it down into sort of like their basic chemical building blocks and then build new plastics. So it can be done. And so if you want to do that, you need to do what Anne's doing, which is there are supermarkets and particular companies who will take that soft plastic from you and actually do that. But you have to take it to a special place to get it recycled. But the local authorities are so overwhelmed with what they have to do that a lot of it goes partly into landfill and partly into energy recovery. So basically, it just gets burnt and that energy is used to generate electricity. Thank you very much, Mark. I'm sure that is not the last time we will come back to that question of plastic pollution and recycling. Now, though, the force of gravity is pulling us into a question about space travel from Brian in Wrexham. This question is voiced by our producer, Ella, and I think it could be one for you, Catherine. I have a question about gravity. If an object uses the gravity of a planet like a slingshot to gain gravity assist, like Voyager 1 and 2 did to cross the solar system, the energy they receive is stolen from the planet's rotation and the planet slows down its rotation fractionally. If an object used a planet's gravity to slingshot, but that planet wasn't rotating, where would that energy come from? Help, please. Help, please, Catherine. Yes, so that's a great question, Brian. One of the best ways to think about it is indeed the Voyager mission. So they were launched back in 1977. It was a one in 176 years special alignment of Jupiter, Saturn, Uranus and Neptune. And the Voyagers used gravitational assist on all of those planets to make their way out of the solar system at high speed. Voyager 1 is currently 16 billion miles from Earth, which is six times further away from us than Neptune. So what is this gravitational slingshot? Let's start off by just thinking about a stationary planet. So imagine you're heading towards that stationary planet in your spacecraft. The gravity of the planet is going to pull you towards it, and that's going to speed you up. Now, provided you're not on a direct collision course with the planet, you will go around the back of it, sling around and come out the other side and fly away from it. But the gravity is still pulling you back. So whatever speed you gained on your way in, you lose on your way out. Now, the trick with a gravitational assist is to use a moving planet and you want the planet to be moving in the direction that you want to go. So the planet's moving away from you as you come towards it. You're going to be sped up. The gravity of that planet is going to speed you up. You're going to go around the back of it, come out the other side. And again, you're going to slow down as you're moving away from that planet. But because the planet's moving in the direction that you want to go, the amount that you lose the speed on your way out is less than the amount of the speed that you gain on your way in. So you get a net boost in your velocity. And that is the gravitational slingshot. So what about the the stolen energy part of Brian's question? Is some of that energy stolen? Does that planet then slow down? It does. Very, very, very slightly. You gain this energy and that energy is coming from the gravitational force field. So that planet is moving around the sun. That's what gives it its motion that gives you that extra energy as you slingshot around it. And the energy that you gain is lost by the planet. And so that slows it down a little bit, which moves it slightly close to the sun. But the amount that it moves is absolutely minuscule. Jupiter, for example, was so, so much bigger than the Voyager as it slingshot around it on its way out of the solar system. So, Catherine, can I ask you the opposite question? Because one of the big problems when you're trying to actually get probes round planets is slowing them down. So you speed them up to get them to the planet, but then you have to slow them down. So do you do the opposite thing? Do you actually put? Ah, excellent. So you can use a gravitational slingshot to both speed up and slow down. So you just have to make sure that you're approaching the planet from the right direction. So if you want to slow down, then you want to approach it from the direction that the planet is moving towards you. So when you go away from it from the other side, then you lose more speed than you gained on your way in. That was brilliantly explained. Thank you ever so much, Catherine. That's great. And now we have a little twist on our listener's questions format for you. We've been sent so many brilliant questions that we wanted to get through. So we're having a quick fire round. I'm going to give each of you one question and you have a maximum of 90 seconds to tackle it. You can complete your answer in less than 90 seconds, but I will cut you off when your time runs out. So make sure you hit your key scientific points before the 90 seconds are up. Are you ready? Yes. Bring it on. Penny, let's begin with you. The clock will start after listener K's question has been asked. And I'm going to read K's question. So here we go. As trees and plants make their own energy through using the chlorophyll in their leaves to work with carbon dioxide in the air and sunlight. I wondered if the principle of photosynthesis in nature could be used to make energy on an industrial scale to solve our energy problems. This would be a use of natural resources that are readily abundant. And it's a basic principle of how our world works. Penny, go. OK, so, well, speed. I think I'd first say that, yes, we already use plant photosynthesis on an industrial scale to get energy, and that is actually the cause of our energy problems. So if you think about fossil fuels, that stored energy that was captured by photosynthesis a very long time ago when we burn it, it releases carbon. Similarly, we're using biofuels now. That's a kind of modern day version of this. It's not really solving any of our problems either. So then we get to solar panels because that's us trying to take light and turn it into energy in much the same way as plants do. There have been a few comparisons and actually studies usually seem to find that solar panels do it better than photosynthesis. So photosynthesis is good, but it's not perfect. But that's not to say that some researchers aren't seeing, well, can we still make solar panels even better by picking up on some of the tricks of how plants do this and applying that to improve our photovoltaic cells even more? How did I do? Did I get it in there? You did. Fifty nine seconds. One minute. That's fantastic. So can I add a bit then? It's still not time then, Mark. I've got a few extra seconds. Right, so also think about it. All our food comes from photosynthesis. So therefore it's a huge, massive operation that feeds eight point two billion people. And I feel like I'm presenting just a minute. No, that's a 10 second. No hesitation. Thank you very much, both. Yeah, I defy you to get through these scientific answers without repeating anything. But moving on swiftly, we're back to space, Catherine. And Ted has a quick question about the red planet. And the time will start after I've read Ted's question, which is here. I have heard it said that material originating from Mars has been found on Earth, delivered by comets. How could we possibly know where it's come from, even if the material is such that it could be from Mars? Why would one rule out the possibility of it being from somewhere else? Ninety seconds, Catherine, go. Excellent question. All right, so there are about 80,000 meteorites known on Earth, and about 400 of them are believed to be Martian three steps to discover their origin. The first is age dating. Most meteorites come from the asteroid belt, which lies between Jupiter and Mars. And that formed about four and a half billion years ago. So if something is younger than that, then it's experienced some geological activity on a planet and has come to us from another planet. All right, next is to look at the oxygen composition in the chemicals. So the oxygen on Earth is almost all oxygen 16. That has eight protons, eight neutrons and eight electrons in it. But on Mars, there is more oxygen 17 and 18, an additional one or two neutrons. So you can look at the chemicals that make the rock and look at the oxygen isotopes in it. If it's heavier on the heavy oxygen, more likely to be for Mars. And finally, if you've got a large sample, then you can look for traces of gases trapped within the rock. In 1976, the Viking probes sampled the atmosphere of Mars. We know there is neon argon, zeon and krypton, their rare isotopes. And we know the precise chemical signature of the atmosphere on Mars. So if we find traces of those gases trapped within the rock that matches the Martian atmosphere, we can be fairly sure that that is where it originated. That was one minute, 26 seconds. You were four seconds. Absolutely. Absolutely. You can use this for a second, Mark. That was a quickfire masterclass and plenty for your periodic table bingo card there as well. I think Catherine, fascinating. Thank you very, very much. And finally, a fascinating question has been blown in on the wind just for you, Mark. And it comes from Nick in Deadington. When there's a predictable source of noise, such as a motway or a football game, it sometimes seems louder when the wind is coming from that direction. It's commonly said that the sounds are carried on the wind. But hold on. Sound is a wave that's propagated through air at approximately three hundred and forty three meters per second. If the air is traveling at, for example, five meters per second, that won't make the sound louder, although it will alter the pitch slightly. It's getting into the weeds here, but I'm not going to start your timer yet. Hence, I have two questions. Have any controlled experiments been carried out to see if sounds are carried on the wind? And two, what is responsible for this phenomenon or illusion? Go. So it's a real effect. The reason being is sound is a mechanical wave, which means that it needs air to propagate it. So when wind blows in the same direction as the sound, I downwind, it refracts the sound wave towards the ground, which makes it bounce and therefore it seems louder and carries further. But if you think about it, that also means that different parts of the sound wave will arrive at different times. So it will be less distinct, less easy to understand what it is, but it will carry further. Whereas conversely, if the wind is blowing against you again, the sound is then upwind. What happens is it bends the sound wave upwards and away from the listener. So it's a real effect. There's been experiments have been done and guess what? It's all because of the bounce on the ground, not because of the speed of the wind or the actual sound wave. Wonderful. Well, that came through loud and clear in just under a minute. Yes. You are all absolutely brilliant. Thank you so much, Penny, Mark, Catherine for being here and answering our listeners' questions. Do come back again. I'm sure we'll have more of these brilliant questions throughout the year. It's been an absolute pleasure. Oh, it's great fun. Thank you very much for having us. Thanks for your time. And Leaves, Gravity, Nipples, Sound Waves, we've covered so much in just half an hour. So thank you to our guests, Mark Maslin, Catherine Heymans and Penny Sarshe. And thank you to all of you listeners. We love getting your questions. We never know where they're going to take us. Please keep them coming. Our email is insidescience at bbc.co.uk. Thanks for listening and I'll see you soon.