Dr Karl Podcast

00:00 This is a Triple J podcast. 00:02 Hello, welcome to another episode of Science with Dr. Carl. My name is Lucy Smith and this week it is all about radio stars. Not me, silly. I mean the ones in the sky. We get into all things space with Dr. Laura Dreesen. She's a friend of the show, a radio astronomer who we love chatting to and she got into some really in-depth questions for but also some basics around the life cycle of a star. It was all really interesting to tap into with her. And we had our regular science questions for Dr. Carl, talking all things red light, thread and pinworm, and much more. 00:35 Let's get into it. 00:38 It is a Thursday, so you know what we're doing. I've got Dr. Carl across from me. Dr. Carl, how are you? 00:43 Ever so good because we have one of my besties. Let me introduce the microphone, the fabulous Dr. Laura Dryson. 00:48 Hello, hello. I'm so excited to be here. Thank you so much. You're a friend of the show. We've had you on before. You are a radio astronomer and you went to Spain recently. 00:58 I did. 00:58 You saw something unreal. Talk us through it. 01:00 Yes. Well, it was very cool. So some of my colleagues in Spain organized a really nice meeting. So I'm a radio astronomer and I do study stars. So like classic astronomer, stars, you know. And they organized it so we could all see the solar eclipse. Oh, my gosh. 01:13 So to be clear, is the solar eclipse the one where you need to put sunglasses on, like protect your eyes? 01:18 Sunglasses are not enough. If you go out to see the solar eclipse, because we'll talk about that, there's going to be one in Australia. Wow. Please don't just wear sunglasses. Otherwise, you'll go to your optometrist and they'll say, there's all these little burns that are in the shape of an eclipse on the back of your retina, which happens every eclipse. So you have to wear really, really... There's solar eclipse glasses and there's a few other options, but you have to wear some really, really dark... glasses to see it. It's very cool. 01:43 One of my favourite pictures is of Lorde where she's, I don't know if you've seen it, but she's in I think New York and she is wearing these glasses while she looks up at the solar eclipse and then she wrote about it in one of her songs. We could potentially be seeing one. What's the projection looking like? 01:58 Yes, so it's looking very good. I get asked this a lot. We can actually project basically whenever you, whatever year you like, we can work out whether there's any eclipses happening because we've got a really good handle on what's going on with our planets and the sun in our solar system. So the next one that everyone should be getting excited for in 2028 on the 22nd of July, there's going to be a total solar eclipse. So the best kind that's going to pass over Australia. And it's going to be the line of total solar eclipse, which we call totality is going to be from Sydney to the top of WA. 02:29 So there's quite a lot of spots where you can go to have a look and see a total solar eclipse. Wow. 02:34 But what you want is cloud cover to be not there. Yes. And so you'll need a bit of warning and if you want to book a flight inland, you might be too late. 02:42 Yes, and Sydney admittedly is not the best place because cloud cover, for those of us who live in Sydney, we know that July is – well, if you like cloud cover, July is great. If you want to see the sun, July is – So I'd be planning to go somewhere else. 02:56 But the thing that bothers me about eclipses is how did Thales of Miletus two and a half thousand years ago in Greece predict an eclipse? Because yes, you can predict an eclipse, like you can predict the tides, but you need the data. And we found that what happens with eclipses is something called a soros cycle and it starts at the North Pole and there's various resonances. And so basically every 18 years and a little bit, you have one solar eclipse and then going in a swipe around the Earth, heading from the North Pole to the South Pole, 120 degrees around, you have the next eclipse and then you wait another 18 years and you've got the next one and it stutters its way around the earth and it eventually falls off and there's a bunch of sorrow cycles. 03:43 But to get the data for this, you have to have people recording it, not just in one city, but all the way from Spain into the Middle East, into India, into China and talking to each other. And so we have no proof that there was a scientific network, but there had to have been. But then secondly... You had to have somebody who was probably fairly junior, like you and I, we've all been junior, and their job is to look at the shadow of the leaves under a tree that doesn't give complete coverage. 04:17 And if there's a partial eclipse... suddenly the shadows, instead of being blobs, will turn into little crescents for maybe 15 minutes. And you need a scientist, a very junior scientist, whose job is to do that every day and then hand it over to somebody else next year and then to put all this together over a range of the world from India to China and then somebody mathematically to say, oh, the Soros cycle, and then 2,500 years ago Thales predicts an eclipse and we have no idea of that background. They didn't document it. 04:47 Oh, that's so frustrating but it's a good sign because astronomy and all science now is so much about collaboration that it's kind of cool that we can say that it was so important even 2,000 years ago. 04:56 And just to finish off before we get your own questions, Laura, Professor Laura, Dr Laura, pointed out to me that radio astronomers don't look at radio stars. They look at practically everything else. There's hardly any radio stars. Is that right? There's very few, yes. 05:11 So in our galaxy… You broke my heart on this one. I know, but I can tell you I just found a couple of hundred more. So there's more. A couple of hundred? There's more, yeah, yeah. 05:18 Is that like doubling or tripling? 05:20 Well, I've now doubled it again. So this is the second time I've doubled the known number of radio stars in space. 05:27 You personally, as a human, single human, have doubled the number of radio stars that the human race knows about. 05:34 Yes. Well, as a human being plus a telescope and some computers. 05:37 But yes, yes, absolutely. Wow, you fully rock, man. 05:41 So we now have 2,000, as of this morning, 2,145. Wow. And most of them are due to you. 05:48 Yes, most of them are due to me, yes. 05:51 We are in the presence of law royalty here. 05:53 Yes, with us on the show. Now, we've already gotten a few discoveries here, but Joseph and Glee, what's your question to kick us off? 06:01 Oh, good morning, doctors. Yeah, I'm curious what the most recent astronomical discovery was that really blew the minds of scientists and astronomers. 06:14 To be honest, Joseph, this is such an amazing question because there's just so many answers that I, as I was looking at this question, I was thinking to myself, which one is the one that I think is going to be my favorite one? Yeah. 06:25 And Joseph, you said, you know, one that they didn't think was possible until it happened. 06:29 Yeah. Well, I mean, I think all of our discoveries, well, actually, no, that's not true. So the discoveries that I've made of these stars, I definitely thought was possible. because I was trying on a specific mission. But a lot of our discoveries, it's not that we didn't think they were possible. We just didn't even think about them at all until they happened. So in my field, one of the cool recent discoveries is something called a long period radio transient. We've got to get better at the names. Yeah. If I say this and you come up with a better name, let me know. So these are really slow for us repeating bursts of radio light. 07:01 So we know about things that burst really quickly. So pulsars, for example, burst every couple of milliseconds to every couple of seconds. But these were way slower, like 18 minutes, six hours. We were seeing these repeats. flashes of radio light and that's weird because those fast things by the time they get to 18 minutes they're rotating where they should be dead so we kind of shouldn't see the radio light from them so we're discovering these things that we sort of go um Sorry, what? And that happens to us quite a bit that we see something and we just think, what the heck? 07:33 So that's actually a really big Australian discovery using telescopes in Western Australia, the Murchison Widefield Array and the Australian SKA Pathfinder. So that one's one of my favourites, long period radio transients. 07:45 Gamma rays. Gamma rays. So what happened was that various countries around the world were building nuclear weapons and keeping it secret. Did you know that South Africa and Israel collaborated? Oh, I didn't. They collaborated to make nuclear weapons. And the Americans, to just check out on who was exploding nuclear weapons... They put into orbit some satellites called Vela, V-E-L-A, and they were looking for the gamma rays that come from nuclear weapons going off. Very peculiar, very odd, very powerful, and they were pointed down at the ground. 08:18 And to their surprise, they picked up some gamma rays and it couldn't be anything from the ground. They had made the first accidental astronomical gamma rays. They discovered gamma ray stars. And by the way, just a big round for everybody. Laura, while I love it to pieces, has two faults. Only two. Only two. One is that you think there's only three elements in the periodic table. 08:40 Yes, I do. 08:41 Or two, there's metals. And hydrogen and helium. Yeah, and hydrogen and helium. And that's it. Forget lead. Everything else is. 08:48 The rest of them, no. Yeah, forget about it. 08:50 And the second thing is that you confusingly talk about light as being not just the stuff that our eyeballs can see but everything else, gamma rays, x-rays, radio waves, microwaves. Okay, so when you talk about radio light, it's not the stuff that our eyeballs pick up, it's somewhere else in the radio band. But as an astronomer, you've got your own language, pick it up for you. Okay. 09:12 Yes, exactly. But just to go really quickly to actually your question, there was one thing that we really didn't think was possible. So we're in a spiral galaxy. The Milky Way is a spiral galaxy. And we thought that there was sort of a cutoff for how far back in time we could look and still see them. So basically when we look back in time, we're looking at sort of if we think about the other way instead, we think about the Big Bang happened, lots of stuff happened, and we thought it would take a certain amount of time before we would see the first spiral galaxy because it just takes time, you know. Lots of stuff has to happen. But with the JWST telescope, we're seeing a lot more further back in time than we thought was possible. 09:48 So now we have this question of like we saw them and it's too early to see them. What's going on? How did they get there? So that's definitely one we didn't think. 09:55 Yeah. Yeah, a bit early. So the Big Bang happens and then after three minutes the cores of the elements happen. After 380,000 years the electrons join on and we thought that stars would happen at hundreds of millions of years. 10:07 Yeah, a really long time. But? But instead we're seeing them way earlier and then you've got stars but then you have to turn them into galaxies and then those galaxies have to form spirals and all of that takes millions and millions of years and we're seeing them just really early in the universe's history, earlier than we thought. So that's a really unexpected discovery. Does that get you started, Joseph? 10:26 Just a couple of things. Oh, yeah, my God, it was so fascinating. Thank you so much. 10:29 Thank you. We are, of course, getting your regular science questions as well for Dr. Carl. Olivia in Geelong. Olivia, you had a car accident recently. Is everything okay? 10:38 Hi, doctors. Yeah, I'm okay. Thanks for asking. 10:42 My question is around the body and the systems that we have. 10:47 So because of my traumatic accident, I was hit, I was teemed at 100 kilometres. 10:54 And I've noticed that my digestive system has changed quite dramatically. I used to, I was going to the toilet regularly every day. And now my functions have changed. I have lost my appetite. I can go three to four days without going to the toilet. And I just wanted to know why the body does that and where the energy is actually going to now. 11:16 And you got t-boned at 100Ks? 11:19 Correct, yeah. Okay, so the reason for that is because we have engineers in our society. And if you ask somebody like Laura, what is pi? She'll go 3.14159, blah, blah, blah. But if you ask an engineer, they'll go... I don't know, what, five? Let's call it ten for a safety factor. And because of the engineers' preoccupation with safety and government regulation, you have been able to survive that. The second thing is you want to exclude physical causes. So that involves going to a GP and then maybe being bounced onto a gastroenterologist... 11:55 And it may be that there's something physical in your gut that's between the bottom of your lungs and the top of your legs that has changed. I don't know. I'm guessing probably not. I don't know. And then maybe the second part is to go and get some psychotherapy and maybe cognitive behavior therapy because if you haven't got any physical damage... then you have conditioned yourself into it. And this happens by accident and it's really terrible. And so in the book trade, I love the book trade and I love all the editors and they're wonderful and you meet for Christmas and you have champagne with them and on one occasion they had champagne and prawns and the prawns were off and they vomited and most of the editors now can't drink champagne because they want to vomit. 12:40 Which is a terrible thing. 12:41 Wow, they associate it. 12:43 Yeah, yeah. And so it could be that that's happened. So what happens in the actual collision in the short term, you've got the sympathetic nervous system kick in. And that is happening within seconds. Eyeballs get bigger, muscle, blood flow diverted, blah, yada, yada. But then in the medium to long term, you get what's called the hypothalamic axis. look it up in wikipedia h-y-p-o-t-h-a-l-a-m-i-c access and that can then cause long-term changes and if you don't want these long-term changes to happen you got you may i'm guessing here if you haven't got any physical changes you may have accidentally got conditioned like the paul uh publicist who can't drink champagne anymore and you can the good news is you can condition yourself back again in many cases Is that helping a bit? 13:34 Yeah, absolutely. So it's really a mind trick. 13:37 Maybe. You could have. I would exclude the physical thing first. GP, then a gastroenterologist, then scanning, and then try the mind thing. And maybe CBT. See a professional psychologist. Don't go on Wikipedia. Don't go online. And don't ask AI. See a human being. 13:56 Will do. Thank you, Dr. Carl. Thank you. 13:59 Linda in Ballarat though, we're going to go to you and something that happened to you while you were working in a photographic darkroom. Can you set the scene? What happened? 14:08 Hi, doctors. How are you going? I am, yeah, so about 20 years ago, I used to work in a photographic lab. I was the printer processor of like black and white films and photography. And I was in there one day and there was a fly in there. The normal light was on and the fly was just buzzing around like a usual fly. Once I turned the red photography lights on, but during the processing, the fly slowed right down and I could catch it over and over and over again. 14:41 And I'm thinking it's got something to do with how the fly sees and light waves and just, I've been sitting on it for 25 years and I just need to know. Wow. 14:51 Wow. Well, it turns out that in that narrow band of light, as we visual electro-neuro-physiologists call it, as opposed to the astronomy people, that runs from 400 to 700 nanometers in wavelength, a nanometer being a billionth of a meter. 15:10 We've got three sets of receptors that are tuned to different colors. There's some tuned to blue at around 440 nanometers. I'm going from memory here, could be wrong. And then green at around 520 and then red at about 575. 15:27 Now, it turns out photographic film, if you put black and white film and the paper, if you put white light on it, it just goes black immediately. But if you put red light on it, it does not go black. And so people would switch on the red light and then they could still see with the red and they could see what they're doing and not stumble into things and not bump into things. We won't even talk about dark adaptation. But then separately, the fly has receptors up at the other end. It can see a little bit in the ultraviolet and it can see blue. 15:58 It can see violet and blue and a little bit of green. It can barely pick up red. It's not totally blind to red but it can barely pick up red. And so in the same way, if you wake up in the middle of the night and you want to go to the bathroom, you move slowly because you can just barely see. So the fly could just barely see and it was flying really slowly because if it was flying at normal speed, it would run into things. 16:24 Yeah, right. 16:25 And so it was sort of mixture of the control system is tied to what they can see because if they run into things, they can die. And so they prefer not to. Is that kind of helping? Is it? 16:39 That absolutely has answered my 25-year-old question. 16:43 Ring sooner on 0439 7575. Don't wait 25 years for the next one. 16:49 Linda, thank you so much. No worries. Thank you very much. We've got Courtney in Penrith. Now, Courtney, your kid had one hell of a question. This is a hypothetical for all hypotheticals. What did they want to know? 17:05 Hey, doctors. So we were driving to school this morning and my nine-year-old said to me, hey, mum, if there's aliens out in space and they're looking at Earth through a telescope, they would see dinosaurs. 17:19 And I said, what do you mean? He goes, because the light takes so long to get there, they wouldn't see what's happening now. 17:27 This is an amazing, amazing question. 17:30 What did you think when they asked you that? 17:34 I was just shocked. I just looked at him and I was like, he could be right. Yes, absolutely. 17:39 Maybe not as far back as dinosaurs, but would they see the path? 17:44 He is, in fact, right. Yes, absolutely. And you're also right, though, that maybe not the dinosaurs. It depends where the aliens are. So light takes time to travel. And we call one light year is the distance that light can travel in one year. 18:01 So just for a little bit of context, the sun is eight light minutes. 18:05 away from the earth so it takes the light from the sun eight minutes to reach us so the dinosaurs lived between about 200 million and about 60 million years ago so if the aliens were that many light years away then yes they would look at earth they probably wouldn't see much at all because earth is very tiny and if you're that far away earth is ridiculously tiny so really they wouldn't see much at all but if they looked at the sun they would be looking at the sun when the dinosaurs existed but if we think about this from the human perspective instead radio waves are really good for communications we use them most of you are probably listening to a radio on wi-fi or bluetooth or something like that and that's all radio waves and we started communicating with radio waves about 100 years ago give or take So if there are aliens that are 100 light years away and they had a really big radio telescope, they might just pick up a teeny, teeny, tiny little bit of radio waves from us. 19:00 But if they're further than 100 light years away, then we're just a cold, dark, rock to them because we weren't really making any particularly bright lights or big radio waves or anything like that so yes depending on how far away you are from earth even if you were on proxima centauri the nearest star to earth which is about four light years away you'd be looking at earth and you'd be seeing 2022 Wow. 19:24 And then just to fill on it, if you had a telescope mirror, say, light years across, which is kind of not possible without technology, you might be able to see Earth from, say, 60 million light years away. 19:39 Oh, my goodness, yes. If you could instantaneously build a big mirror very, very far away, then, yeah, we would be seeing the reflection from the past because light takes time to travel. 19:49 And then secondly, we are all living in the past because it takes three-tenths of a second between when the photons land on your retina and your brain turns that into 3D colour vision. It takes three-tenths of a second. We are all living three-tenths of a second behind reality. I don't understand how Bruce Lee did his stuff. So, yes, we are all living behind reality. And remember, as hippies used to say, reality is for people who can't handle drugs. 20:15 And just for one last little bit of trivia, to see the dinosaurs, if you were aliens, you'd have to be outside our galaxy because our galaxy is big but it's only thousands of light years across, not millions. So the dinosaurs are millions of years ago so you'd have to be millions of light years away. 20:30 In fact, the nearest galaxy to us is Andromeda which is about two million light years and you'd have to be at least 50 times, 100 times further than that. Exactly. So how big would the mirror have to be like tens of light years across? Huge. 20:42 Huge. Humongous, yes. 20:43 Hundreds of light is something. Something. We'll leave that as an exercise for first-year physics students. 20:47 Exactly. 20:48 Courtney, does that help? Sorry, they'd need really good technology, which maybe they have. Yeah. Yeah, so it's possible. 20:57 It's not impossible in the sense that it's not impossible that the Pacific Ocean would freeze over tomorrow morning. 21:05 Well, it's one hell of a hypothetical. I hope you can play that back via the Triple J podcast to your kid, Courtney. 21:12 I will, yep. 21:15 Blake in Meand in Brisbane, you know, Dr. Carl just mentioned the oceans. What's your question? 21:21 Hey, doctors, my question's about displacement, like your mass getting into a bathtub and the water rising. 21:28 If that happens in the ocean, sort of every time I see a giant ship or think about shipwrecks or anything man-made that's ever fallen in the ocean, surely that's a whole lot of mass that could displace the water. 21:42 question yes so i think the weight of all the ships is roughly two billion tons i rely on this for xkcd who is randall munro um follow him he's very good and he worked out that if you took all of the ships out of the ocean the two billion tons that the water level would drop down by about nine millionths of a meter but the oceans are rising at 12 billionths of a meter so Within about two-thirds of a day, the oceans would have risen to compensate for the ships being taken out. 22:15 The oceans are rising because we're heating the oceans, so you've got thermal expansion, plus we're shifting water from land to sea, from underground, plus we're also melting glaciers. 22:30 But the good news is we can fix global warming, keep fossil carbon, that's oil, gas and coal, in the ground. 22:37 Okay. Does that answer your question, Blake? Yeah. Maybe I just went off on my own and didn't answer your question. Tell me what I should have answered. Go on. 22:46 Oh, no idea. That's why I'm asking. 22:49 Okay. Oh, yeah. So, yeah, the ships do make the oceans a bit higher, but if you took them all out within less than a day, global warming would have more than compensated for all the ships being taken out. 23:00 It just got itself out. Okay. 23:01 Very good. Great. Thanks, Blake. Thanks. 23:06 We are doing science with Dr. Carl. Dr. Laura Dreesen joins us as well, talking all things astronomy. And Simon in Gladstone Park, you have a question about gravity. Talk us through it. 23:16 Hey. So as we know, the moon is moving slowly away from the Earth. I think it's away from. So that brings about a point of curiosity for me. Yeah. how are the other planets in the solar system moving in relation like are they moving away from each other towards each other the sun loses a little bit of mass through burning its mass and then ejecting its mass occasionally so are the planets sort of moving away from the sun towards the sun are they moving away from each other how does that work 23:47 Whoa. 23:48 Ask a little question, why don't you? 23:49 Yeah, yeah. Just a simple one, you know. 23:52 Yeah, just a simple one. 23:53 Well, you're right about the moon. The moon is moving away and so are all the planets. So moving away from each other, maybe that's a little bit trickier to calculate because we're all going around the sun. But yes, we're all moving slowly away from the sun. And that's for a few different reasons. One of the key reasons is that there's no such thing as a perpetual motion machine and this applies across all space and time. 24:17 Except on the internet? 24:18 Except on the internet, maybe the internet. But if we're looking at space, there's no such thing as a perpetual motion machine. So even if two things were orbiting each other and they stayed the same mass and didn't lose anything, they can't stay in exactly the same orbit forever because that would be perpetual motion and we don't allow that in this universe. Maybe in a different one, but not this one. So they're moving away because they're losing energy through gravitational waves, which is another very cool topic. So everything is moving away. You're also right that the sun is losing mass. 24:51 It's losing mass in a couple of ways. So it has a solar wind where it's losing plasma from its outer layers. You're right, it's also losing mass from flares, big chunks of plasma that we get then the pretty, pretty lights of the aurora, which is very nice. But also every time that it's doing fusion in its core and then it takes a really long time for the photons of light to get out. But as the photons leave, they're also taking energy, which we know from E equals MC squared is also mass. So the sun is also losing mass because it's shining. So that's always going to be the way. 25:21 So the sun is losing mass over time. And I suppose slowly this would impact our gravity, but we are all moving away from the sun slowly over time, just like the moon is moving away. 25:34 And the good news is that we probably won't get swallowed up by the expanding red giant that the sun will become, according to some recent research I read. Did you come across that? 25:42 No, I didn't, but that's a good hot tip. 25:45 I was so worried about it. Just a few billion years. So in about five billion years, the sun will have come, burn up most of its fuel and it will start to expand and turn into a red giant and it will lose about 20% of its mace in its final conniptions and expand... to definitely swallow up Mercury and Venus and there was always a worry, would it take the Earth or not? And some astronomers looked at a red giant 120 light years away and then they did some calculations. On one hand, there'll be a lot of debris in the solar system from the sun going through its conniptions and that would tend to slow the earth down so it would come in closer to the sun. 26:26 But on the other hand, the sun has lost 20% of its mass so the gravity is weaker so the earth would tend to go far and away. So weighing it up, probably we won't be swallowed by the sun in 5 billion years so you can sleep easy on that one. You don't have to worry anymore. 26:41 Yeah, okay. That's very interesting. That gives me a lot to mull over. Thank you for your detailed answer on that, Doctors. 26:49 Thanks, Simon. We've got Brit in Wollongong. Dr. Brit, you've got a space question as well. 26:54 Yeah, hi, Doctors. 26:57 So similar to a previous caller, I also have a child that's a bit space-obsessed at the moment, and he borrowed a kids' space encyclopedia, and inside it is kind of a diagram of... of the life cycle of a star and previously I'd thought that all stars kind of went through a similar cycle of expanding and then collapsing um with a supernova but this diagram seems to suggest that there's other pathways that a star can take so I wanted to know um what kind of determines the trajectory of a star and their life cycle and what trajectory is our sun on 27:37 So we're talking stellar evolution. So this is pretty cool because actually it really depends on a whole bunch of things because a lot of stars aren't born on their own. They're born in a big cloud of gas and dust and quite a lot of stars are actually born in binaries and that has a really big impact on how they evolve because it's not just one star evolving on its own. They have lots of interactions and they change mass with each other and one explodes and messes with the other one. So there's a lot of complexity. It's a whole field of research. But you're right, not all stars end up in a supernova explosion. 28:10 And even the stars that explode as a supernova, there's three options for what could be left over, a black hole, a neutron star, or maybe nothing. We're not 100% sure about that last one, but black hole or neutron star. But the sun is not going to do that. It will never do that. It's never going to explode. there's a rough threshold so stars that are about about because it's a very hand wavy threshold about 10 times more massive than the sun those ones typically end in in an explosion and their lives are shorter still hundreds of thousands of years but shorter than something like the sun but stars that are less massive than about 10 times the mass of the sun. 28:46 Instead, over time, they expand into a red giant, which is a cool, dusty star like Betelgeuse, which is in the Orion constellation. Then they blow away like their outer layers. So they're in an outer layer of kind of colder dust and plasma, and they blow that away. And then you're left with what's basically the core of the star, which is called a white dwarf. And those sort of just stick around for a really, really, really long time. So there's all different sorts of stars. And the smaller the star, the longer it lives. So the sun's got until... 29:17 It's middle-aged right now and it's going to be middle-aged, what we call main sequence for about 10 billion years in total and we're about halfway through that. But some other stars will stick around in that midlife, that main sequence, just chilling basically for longer than the age of the universe. So they just, and they're called M dwarfs or red dwarfs and they just stick around. And that also means they're the most common type of star in the entire universe and we see them everywhere. 29:45 No matter which direction you look, there's M dwarfs or red dwarfs just everywhere because they live basically forever. 29:51 And you hate them because they're like cockroaches. 29:54 They can be confused for other things. 29:56 Yes. So depending on the type of astronomer, you might hate them. I actually love them because M dwarfs are very common radio stars because I look for stars that have a strong magnetic field. So big magnets in space. And M-dwarfs have a lot of interesting properties like how fast they spin and how deep their outer layers are that mean they're often quite magnetic. So I love an M-dwarf. 30:16 But other astronomers hate them like Peter Tuthill. 30:18 Yes. Yes, they do. 30:20 And just to finish off, 40% of stars are binaries and look up the Hertzsprung – what's the Russell diagram? 30:25 The Hertzsprung-Russell diagrams. 30:26 Look that up on Wikipedia. Yep. And with regard to your child, I do Q&As. Go to drcarl.com. I'll do a Q&A with their class online for free on a Wednesday afternoon. 30:37 Oh, excellent. Yes, this book also has stuff on binary stars, so I'm glad to have some context for that. But I will say my son will probably be a little bit disappointed to learn that our son will not end up a black hole. 30:49 It would be cool. 30:50 I love that. Britt, thanks for your question. Thank you. And we've got Nathan in Mullumbimby. Nathan, you've noticed something while using silicon. What's going on? 30:58 Hello, doctors. Yeah, I've got a thousand questions, but one is I use silicon at work and if you spit on your finger to smooth it over, it doesn't stick to your finger. But if you dip your finger in water and smooth it over, it sticks to you. What's going on with spit? 31:17 So what sort of tradie are you? 31:19 I'm in a very exciting industry, solar and batteries, so we seal the roof quite a lot. 31:26 I've been running my house and my car entirely off sunlight for two and a half months. I love it. Okay, getting back to the silicon. Silicon sealant is sticky because it spreads over a surface and it makes strong intermolecular attractions both with itself and the surface – that you are joining it to. If you use water, the water actually helps the uncured silicon smear. It evaporates away and it gets onto your skin. Spit has chemicals in it called mucins and they stop it from sticking. 32:01 But the trouble is that some of the other chemicals in saliva might interfere with the silicon if you're using it like a really specialised silicon. I don't know, there's so many different types, high temperature, etc. So in general, the silicon manufacturers recommend that you use soapy water. Although, yes, it will work. That was a good answer. We think so. 32:20 Yeah. 32:20 Thank you, Dr. Nathan. 32:23 Phil and carry on, what's your question? 32:26 G'day, doctors. 32:29 I heard an ad on the radio which dealt with medication for the management of thread and pin worms, and I was just wondering, it sort of got me thinking, the average person, what's the odds that they are playing host to these things? 32:45 Ah, I'm guessing that this advertisement was not on a government ABC radio station because they don't have ads. Correct. Right, okay, fair enough. Now, there's something weird about these whole worm things and I'll just dive in the hard end first. It turns out that there are certain populations of humans around the world who have, firstly, very low levels of asthma, allergies, inflammatory bowel disease and some autoimmune diseases and we think... is because they are naturally infected with different types of worms, right? 33:18 And the way that we think this works is that the worm doesn't want to be attacked and we've found, looking carefully at it, that the worm actually takes over your immune system so that it's more likely to survive and accidentally it makes you more resistant to asthma, inflammatory bowel disease, et cetera, et cetera. Now, do not go down a pathway deliberately, which they do in the USA, of deliberately buying little worm seeds, little sacks over the internet and swallowing them to get rid of your asthma. They do that. But rather the real research is looking at the chemicals that they produce to stop them doing that. 33:52 So with regard to you actually having worms, the way you get them is by swallowing the eggs from bedding or food or undercooked meats. Of course, some parasite worm-y things have a life cycle involving animals or some can penetrate through the skin. Jimmy Carter, the ex-president of the USA, was instrumental in bringing down the cases of that worm where he had a worm up to a metre long, pushing through the muscles in your body like you can push through the corn in a cornfield. 34:22 He brought the incidence down of that from 100 million to a couple of dozen by using his influence. Good on him for that. And contaminated food. So you can be carrying worms and feel perfectly normal, but I definitely wouldn't go out and automatically take worming tablets. All drugs are poisons. What matters is the dose. Now, have I left something out there, Dr. Phil? 34:42 No, it's not that. Yeah, I'm just curious because I thought if it's going to be on radio, then it must be a thing. 34:49 I was hoping not a common thing, but that's why I was asking the question. 34:52 Now, look, a colleague of my son is defending a certain Sydney personality and I've learned something very important, which is that in law, everybody is innocent until they are proven to have run out of money. Mm-hmm. And in the same way, according to the advertisers, you have whatever disease they're selling your tablets for because they're really good at selling them. So I would go to your GP and your pharmacist first. 35:17 Right. Okay. No worries. 35:19 Thanks, Phil. We've got Darren in Sydney here. Darren, what do you want to ask Dr. Laura? 35:25 Yes. Hello, doctors. A few weeks ago, Dr. Carl, you mentioned that the universe and space was expanding, I'm not sure which kilometres or miles, but around 42 miles a second. 35:37 My question is, and I've always wondered this from a little boy looking at the stars, if it's expanding, what is it expanding into? What is actually there and where does that end? Like it just boggles my brain that something can just go on forever. 35:54 So I'm going to take a leaf out of Dr. Carl's book and start by answering sort of a different question. Get him, girl. 36:03 Yeah, exactly. 36:04 Well, no, but I think it's important context. Let's say really important context for this. I think sometimes we feel like we have to understand things. And a lot of things that we know about science and even those worms that Lucy and I were making faces. Yeah, yeah, yeah. that there's a lot of things that we know but we don't like and don't ever feel good so i think we feel like if we if we you know ask what one plus one is and it equals two that feels good we understand that it feels nice but there's quite a lot of things especially about astronomy and physics that just really will never feel good and the answer to this question is we don't know and we will probably never know So we don't know what was before the Big Bang. 36:45 We don't know what's outside of the universe. And we can only know things if we can observe them. When we're talking about space, we can only know things if we can observe them. Now, there's lots of theories and lots of maths and lots of really cool things. But unless we can test it, a theory is kind of just a nice idea. So we can't get information coming from outside of the universe. And unless we can detect information from outside of the universe... then we'll never know what's outside of the universe. 37:16 So unfortunately the answer is we don't know to all of your questions, which is cool. Science loves the we don't knows, right? And we've got to be okay with the unknown. Yeah, exactly. 37:25 And you happy with the Hubble tension? We don't have time? 37:28 Well, the Hubble tension is about how old the universe is. And we disagree. There's lots of disagreements about that one. 37:35 Science is like that. What do you think? How old do you think the universe is? 37:38 I mean, I'm a radio astronomer and I'm an observational astronomer. So I'm happy with, you know, around 13 billion years. That sounds good. But we're debating and we're getting lots of information from different sources. So the trick with the age of the universe is we've tried to measure it. a few different ways. There was the Planck telescope, which is a really cool telescope that many people have never heard of. And it really did a lot of the experiments required for finding this out. And it sort of said, this is how old the universe is. And then we tested it using gravitational waves. And we were like, meh. Eh, maybe. 38:09 And then we tested it using all different methods and we got different answers. Depending on how far back in time you look, what information you get, you get a different age of the universe. So this is the sort of thing that astronomers love. This is the I don't know that we love because it gives us more things to look at and work on. 38:25 And to close this out, Woody and Adelaide, this is a pretty big question to end on. What do you want to know? 38:30 Hi, doctors. Could electromagnetic radiation have mass if you reverse the classic E equals MC squared to M equals E over C squared? Yeah, like, can it obviously be big and spread out? Would there be gravity from that? 38:46 Okay, I'll give you the easy answer. Energy is just mass that's been allowed to run free. And mass is energy that's coagulated and joined by the famous E equals MC squared equation. And so you can go backwards and say if there's energy in electromagnetic radiation, does it have mass? I think so. Help me, Laura. Am I wrong on this? 39:06 No, I think that's fine. I was thinking about this because I haven't done classical physics in so long. I've been too worried about what my telescope is seeing. Mm-hmm. But, yeah, I think why not? Why not? 39:17 Yeah, because I've been sitting on this for ages and I did some little calculations of myself, obviously limited for what I can do, but it worked out that the sun was spitting out like four tonnes a second. 39:29 Yeah, so the sun is burning 620 million tonnes of hydrogen every second, turning that into 616 million tonnes of helium. There's a shortfall of 4 million tonnes, 1 million tonnes of which goes out as a solar wind and 3 million tonnes is E equals MC squared energy. 39:45 Yeah, I think that as physicists, we're used to seeing the other way around. We often see mass turned into energy, which is emitted as light. But I don't think there's any particular reason why we can't go the other way. 39:57 Would that light have, like on the grand scale of the galaxy, have an effect with its mass? 40:03 oh, I think it depends which light you're converting and how you're doing it. But, yeah, it would have an effect. But, of course, most of these things are happening on smaller scales, like inside stars or inside galaxies and that sort of thing. 40:13 And the really big effect comes from very massive objects, whereas the amount associated with radiation is relatively small, unless you're looking at the centre of the atom, but that's another story. 40:23 Yeah, it gets very complicated. 40:25 Very complicated. Woody, I think we'd need a whole episode for that. Thank you for your question. 40:29 Oh, please do. Thanks very much, guys. 40:31 Yay! Dr. Laura Dreesen, thank you so much for joining us. If we want to learn more about the work that you're doing, your discoveries, where should we go? 40:38 So I'm astrolora.com or astrolorad on most social media. Someone already had astrolora, so we had to go with astrolorad. 40:46 God damn. 40:47 I know. We love it. They don't even post about space. 40:49 I know. Isn't that so annoying? Someone took Lucy Smith and they haven't posted since 2012. No. It's really annoying. But either way, we'll pop your details in the podcast episode show notes. Dr. Carl, we'll catch you next week. 41:00 Pitchy Keen. Yay. 41:02 And that's it. Thank you so much to Dr. Laura Dreesen for coming through and answering our questions. She's so great, so enthusiastic. If you want to check out more of her work, we'll pop her details for you in the show notes. A big thank you to Ella Carter and Byron Smith for producing this episode. I'm Lucy Smith. We'll have more Dr. Carl for you next week. 41:20 Dave Marchese here from the Triple J Hack team. Hey, if you love Dr. Carl's podcast like I do, you might enjoy the Hack podcast as well. Each day we bring you the news that matters to you, from the latest science on climate change to what's happening in politics and news around the world. The Hack podcast. It's your daily fix of the news you need to know. Get it wherever you're listening now.