Cosmic Questions: Dark Energy, Stellar Birth & the Nature of Black Holes

Hi there, Thanks for joining us. My name is Andrew Dunkley and this is Space Nuts, a Q and A edition. It also happens to be our sixth hundredth episode Believe it or not. And what are we doing special today? Nothing. We're just going to answer audience and well it happens so often. Now we're just going to answer audience questions and we've got a bunch of them. The question of dark matter and dark energy theory has come up again. In fact, one of our listeners has come up with a theory about dark matter and dark energy theory, so we'll investigate that. We also have a question from somebody using a very interesting pseudonym finding where our son was born. I think we've been down that road before recently. So they're revisiting that the temperature of black holes has been raised yet again. We talked about that recently, and Peter has asked us about the expansion of the universe. That's all coming up on this edition of Space Nuts. Fifteen, Channel ten nine, Ignition thig one start Space Nuts nine or three two more Radio one Space notes asn't actually bought it. Bill's good once again joining us from the Oh It's not the six hundred time because we've had time off, so it's probably five hundred and ninety two or something like that. Maybe I don't know, maybe a few less. But his name is Fred Watson, Professor Fred Watson, in fact astronomer at large HIO. Fred. How you doing, Andrew? I'm google see you again. Good to see you too. Can you believe it's six hundred episodes? My goodness? So we because we know have two a week. Ye, you've got through one hundred every year, basically, doesn't it? Mora where it used to be every couple of years. So, yes, we're just moving faster. It's the expansion of the universe because it's accelerating. That's a little it is relive relativistic. Indeed, let us get straight into our questions because we've got a whole bunch of them. Daryl has set us in a question today space and that's I've been giving dark energy and dark matter some thought. If I've got this rise, dark matter pushes the universe apart or away, while dark energy attracts or brings stuff together. So could dark matter and dark energy be the same thing, but have like a north and south pole, I e. Dark matter north would be the particle that clumps together, and dark energy south would be the particle that pushes outwards, creating negative pressure and expanding the universe. Thoughts, now that's his question, But he says, by the way, Martin's joke about the Ganab Gibb being a lost bg brother made me laugh out loud for a couple of minutes. That's Daryl from South Australia. Yeah, I thought it was funny too, and that's the first time Martin's ever been funny. But no, it was a good that was a very good one. Yes, so this is an interesting theory as a dark matter, say Powell, dark energy North Powell opposite attract type of scenario. I don't know what do you think. So the issue, Yes, it's a nice thought because that you know, we naturally think along those lines when we recognize that one of these forces entities pull stuff together and the other pushes it apart. And in many ways that's the crux of the matter, because the two of them are fundamentally different in their in their effect on the universe. So dark energy, which comes as a man which is manifested to us in the accelerated expansion of the universe. That's an energy of space itself, and to the best of our ability to determine these things, it is isotropic. In other words, it's the same in all directions. Now, some people have questioned that, suggesting that maybe you know, for all, we are looking at a big chunk of the universe with a horizon of thirteen point eight billion light years. It may be that that's just a small part of the universe and there are other bits where, you know, the acceleration is not sorry, the expansion is not accelerating, and the two sort of even out. That's a caveat that we can't really deal with because with no idea what happens beyond the little bubble of the universe that we can observe, And certainly it's true within that bubble the acceleration is basically or the accelerated sorry, the accelerated expansion is basically the same in all directions. So it's a property of space itself. It's a fundamental property. Whereas dark matter, yes, that's got gravitation and pull stuff in, it's definitely clumpy. It actually, well, it follows the visible matter. That was the way it was thought to be when we first started thinking about dark matter, but now I think it's probably the other way around. That the visible matter is visible because dark matter acted as a kind of scaffolding in the early universe for the gravitational pull of dark matter in order to bring the clouds of hydrogen together, compress them and make them turn into stars. So that's why dark matter and normal matter stick together. But they do stick together. And when you know, when you observe the universe on the larger scales, we can see by for example, gravitational lensing, we can see that the dark matter definitely follows the visible matter. So there will be places where there's hardly any visible matter and there's hardly any dark matter, whereas with the dark energy it's everywhere, and so there are fundamental differences between them, and I suspect in the end, you know, if we were having this conversation in twenty to thirty years time, we probably will be actually, But anyway, when we look back on this, we might have realized that the dark energy is a boson, it's a force particle, whereas dark matter is some sort of matter particle made of quarks and things of that sort. So probably fundamental differences rather than just that sort of the idea that they might be the same thing but with a different polarity. I don't think the evidence supports that. I suppose we could say Daryl's fallen for the naming era of these two things, because you've said all along that dark energy is poorly named. It's not really the right thing to call it. Well, neither of them are really, you know, the invisible would have been far better, but dark. It's actually Fritz Vicki back in nineteen thirty three who labeled this stuff dark matter. He didn't what it was, and he said there must be something there, which he was calling dark matter, that's providing enough of a gravitational attraction to stop clusters of galaxies from dispersing altogether. Interesting. They'll figure it out one day, but for now it remains a mystery. But there's got to be something in that connection between real matter and dark matter plumping. Like if you go somewhere there isn't much matter, there isn't much dark matter. So there's got to be some connection there that will give us the answer day if we can figure out what the connection is. Yeah, well, the connections gravity and it's the. Only well, we haven't figured that out either. No, that's right. We basically we know how it behaves. We know very accurately how it behaves. We don't know what it is. It is indeed a mystery, Darryl. But coming up with an idea always is a good way to get people thinking. And maybe maybe somewhere in the dark reaches of the Internet, someone will hear this and go, hang on, Daryl's onto something, and then he'll go to his Wikipedia or his Encyclopedia Britannica, or his Funk and Wagnoff, flick a few pages and go, I've got it figured out thanks to Daryl's question on space nuts. So you know there are no dumb questions in astronomy, are there for it? No, that's absolutely right. There's just dumb answers from the LOCs and mood. It's Daryl, great to hear from you. Our next question comes from the fields of Norway, and this question goes by the name of Some will recognize this slaty bar fast listening from the fjords of Norway. Last week, someone asked the question about viewing the birth of the Sun, and Fred answered with the hypothetical mirror in space. My question is if we calculated the exact location in space for the Sun four point six billion years ago and pointed a telescope at those coordinate coordinates, would we see anything? Hmmm? Slutty Bartfast won an award, didn't he, for the fields of Norway? So that's right, that's right. Yes, that was because he designed the designed them. Yes, yes, he made fjords. That's right, that was what slati Vartfast was famous for. One of my favorite Douglas Adam's characters. Ah. Yeah, I think the moment where he's forced say his name is one of the the funniest moments I've ever experienced, because first time I ever listened to it, I listened to the audio version that just caught me so beautifully. I just couldn't stop cackling. Right, No, it's a pick stuff. One of the all time greats in science fiction. Absolutely is. Yeah. Anyway, the answer to Slatly Bartfast's question is no, So do you want to keep going? Well, I mean he's basically saying, so, you're saying, we would not see anything if we could figure out where the son was four point six billion years ago and then pointed a telescope at it. Yeah, because first of all, the son isn't there anymore? No, I know where it is. Yes, the odds are that point. You let me see which way you're pointing. I'm pointing that way that way. That's good, that's probably correct to In fact, it's behind me too, it's. To my it's to my right rear. All right. Okay, that's a bit intimate, isn't it anyway? Never mind? Yeah, the sun is certainly not shining out of that particular part of me at the moment, but it's it's in that kind of direction. It's all your funds think, though, is they? Glad? I don't even have any I don't get fan mail. Good abuse. Well, anyway, notwithstanding all that, what was the question again? Yes, if you could work out where the sun was four point six billion years ago and point a telescope at it, you wouldn't see anything because the point where the sun was formed and it will be only a few at most one hundred million light years away. So yeah, you've got to look back time. But you've got to look back time. It's probably less than one hundred million years and the sun one hundred million years ago was a lot like what it is now. It's slightly hotter, and a few other things that were going on at the time, but not much different. But the fact is, it's. Not there, it's here. So even I think I said in that thought experiment, you'd have to have a mirror something like two point three billion light years away, which is going to take you quite a lot of time to put in place anyway. But if that mirror was looking back to wherever the Sun was formed, and we don't know where that was, we know it's within the present vicinity of the Sun because stars don't move that fast. Anyway, you have this mirror and you capture a reflection of the Sun being born. That thought experiment I think would work. But just king where the son was when it was born isn't going to tell you very much. There's got to do something there though, right, Well, yeah. Probably other stars and things like that, you know. It's just part of the solar neighborhood. Yeah. Yeah, our son, I suspect came from, you know, a pretty rough neighborhood, and that's why it left it inherited money and managed to manage to get away. Yeah, but then it discovered drugs, didn't it. Yeah, Well that's that's what happened is yes, and and then we turned up and yeah, well hell broke loose. Yes, but there'd be nothing to say. There nothing to say there now. Nothing that's really of any interest, just to other stars. Yeah, yeah, although we're still looking for Earth's siblings, sorry, the son's siblings. That's that's right, because there are there would be some, but they wouldn't be there either, would they. Well that you know that the stars and that I'm sorry. The stars that were born alongside the Sun in the same cloud of gas and dust are probably not that far away, but they Yeah, one hundred yeah, one hundred million light years I mentioned before. It's probably much much less than that. I don't know quite why I thought of that anyway, because the center of our galaxy is only twenty five thousand light years away, So I probably meant a hundred thousand light years when I said a hundred million. Something's going wrong with this program today, I'm not quite sure. Well, it's it's six hundred that's what it is. That's what it is. There's a there's a gap in space time has opened up, which I'm floundering in at the moment. Yeah, so you know, you might it's it's not gone very far. That's what I'm saying. The siblings from the Sun born in the same gas cloud from the Sun. Probably within they might even be within the nearest one hundred million, sorry, one hundred light years, not million light years. So, and that's why we can use very high resolution instruments, ones that really analyze the spectrum of a star in great detail, but need the star to be relatively bright. That's why we can use that technology with the real hope of finding the solar siblings, because it's by analyzing the spectrum the chemical composition of a star in very great detail. That's how we would identify that the star had exactly the same chemical composition as the Sun and could be regarded as likely to be a solar sibling. Okay, we may one day find one of them, but who knows. Yeah, we'll see. And thank you slightly Bardfast, whatever your real name is. That maybe that's it could be. Thanks, thanks for the question, and thank you for sending me the Babelfish so I could read the question. That was a good idea, very very good idea. This is space nuts. Andrew Duncley here with Professor Fred Watson. Let's take a break from the show to tell you about our sponsor, nord vpn. Now, if you've ever felt like your online privacy is slipping through the cracks, then you're not alone. Hackers, scammers, harvesters, they're all out there trying to get your private info, whether that's your passwords or your personal details to sell on the dark web, or to use themselves to access your bank account's, credit card details, and who knows what else. But you can protect yourself with nord vpn. You can take control at home or more importantly, when you're out in public using free Wi Fi. Right now, using the exclusive space nuts offer, you can receive four extra months for free on anrdvpn dot com plan. Nord vpn encrypt your internet connection, hides your IP address, and offers access to over seven seven hundred servers around the world. Plus with features like threat protection, pro mesh net, ultra fast speeds via nord links, your digital life stays private and efficient, So don't miss out. Visit nord vpn dot com, slash space nuts and enter the code space nuts to claim this deal. Remember there's a thirty day money back guarantee, so it's risk free to try. Stay safe stay private and browse with confidence. That's nord vpn dot com slash space nuts and use the code word space nuts. Nord vpn dot com slash space nuts. And we're looking at it. It's you know, that moment where they realized they had a problem on Apollo thirteen sounded much better in the movie. It just yeah, you. Brew, you broke up, Ah, exactly as you were saying. I noticed that, and I was going to keep talking until you came back. But tell me what you said. I said that that moment where Apollo thirteen realized they had that problem sounded much better in the movie. Yeah, it was. It nearly as dramatic in real life, was it. Well, well, it was dramatic, but the way they announced it, yea. They basically just said, yeah, this button didn't work more or less. Yeah, I picked stuff. I mean, it's always me Tingles Apollo thirteen. Absolutely. Yeah. Now, Freid, let's move on to our third question. This one it comes from. Beyond Evening Fred and Andrew. I have to thank you for a fantastic podcast. My first choice every evening among lots of interesting stuff, it's the first one I choose. It's regarding the question you had about temperature or black holes. I must ask you to clarify. If material acrets close to your horizon, it's millions of degrees hot. If I follow the material spiraling inwards, it does not suddenly become cold when it's interesting horizon. Right, it's still extremely hot, maybe even hotter, even if it's supposedly hard to measure, because it's hard to get a thermometer in there and have a reference. But it extremely hot, but seems called to an outside observer because it does not radiate anything. But maybe it could be clarified somehow. It's not magic that it suddenly gets called. It just stops emitting, right, Take care. It's beyond from Gothenburg. I love your show. Thank you. Beyond that Babelfish is working well because his English was excellent. He lives in a nice place as well. Gottenberg's got a very nice city center with a lovely opera house. Yeah. I haven't been there, In fact, I haven't been to Sweden yet, but it's on the wish list, so we'll see how we go. Now. He's referring to a question that came from Casey in Colorado when she was asking about the temperature of a black hole. So he's basically kind of saying, look, I understand what you were saying when you answered Casey, but now everyone thinks they're cold when they're probably not cold. They're just not emitting anything. Is that right? Yeah, that's that's right. They're cold because they're not emitting anything. But beyond's right that you know the temperature of the accretion disc, and probably the way to look at it is the temperature of the event horizon. There's millions of degrees because that's where all this stuff is circulating at high speed and with huge amounts of energy and emitting X rays. It disappears over the event horizon at very high temperature, and presumably within the event horizon it's still got that high temperature. But then it hits the black hole. It's sucked in, and if you could measure the temperature of the black hole itself, you'd find it was virtually absolute zero, very very temperature. Okay, because it's not emitting anything. Stuff's going in and it is it is hard to imagine, and Bjorn mentioned magic, and that's almost what it is. You know, stuff that's going in at very high temperature. But if you could measure the black hole itself, supposing it stopped recreating material, then you could then measure its temperature. It will be virtually zero. Well well, well, they are so complicated though, aren't they. I mean, we we're still learning a lot about black holes, and then we're starting to image a few of them. We've got a couple of good pickies now. But they are still mesmerizing and mystifying, because until dark matter came along, we got more questions about black holes than anything else. They are the thing that people want us to unravel in terms of understanding. But we're I think we're a long way away from that at the moment, aren't we. Actually? I think you know that we know a lot about black holes, considering that sixty years ago nobody believed they existed. Yeah, and we've observed them. We've actually observed the radiation coming from the the the accretion disk, the region around the event horizon. We've we've observed the effectively the shadow of the event horizon of several black holes now and even detected the polarization of the material that's been sucked into it. And this is extraordinary stuff. These are measurements that really only a few years ago would have been thought to be impossible, but we're I think, doing it rather well. So we're still learning about black holes. They are and that's the reason why they're so fascinating is that they are completely counterintuitive. How do you have something that's simultaneously at zero and a million degrees and that's what you've got. So yeah, so it's yeah, there's there's still they're still very very interesting object. But back to Beyond's question, the temperature is zero absolute zero? Were thereabout because of the fact that it. Doesn't It doesn't really get anything exactly certainly, so the way to imagine it, I think, and this probably puts it more succinctly. Yes, well, well it's a creting. You can't you can't see the black hole because it's surrounded by this hot material that very high temperature is being swallowed into it. But if there was, if that supply of gas ran out and the black hole stopped recreating, then you would and you could measure its temperature, then it will be zero, effectively be absolute zero, a little bit above but not very much. Okay, there you go, Beyond, and I'm looking at photographs of Gottenburg. It's it is an absolute beauty of a city, isn't it? What a lovely part of the world. Yeah, very lucky, nice trams. Thanks bien. Great to hear from you in Sweden. Okay, we take your being with air space nuts. And believe it or not. Our next question comes from Sweden. Does the expansion of space mean that the universe gains more meters or are the meters becoming longer? Related to this, is it space only that is expanding or is it space time? If so, what's happening to the time part of it? Is time expanding to what would that mean? Thanks for a most interesting podcast. Peter from I'm going to pronounce this incorrectly falloon in Sweden. So yeah, hopefully I got that right. I think my Babelfish can't translate and the sweet Swedish. Well, if you put it the other way around, put in the other ear, yes. That'll do it. So, yes, that's a great question. And so my view, you know, the intuitive view, which is based on a few years of thinking about this kind of thing. The meat the meters are becoming longer, and that's sort of illustrated by the fact that the wavelength of radiation is getting longer. You know that radiation had a particular wavelength when it was emitted, and as the universe has expanded, whatever it's coming from, whether it's a distant galaxy or a quasar or whatever, as the universe has expanded, that radiation has been stretched, which means that the meat has been stretched, because the frequency remains the same except when you observe it from our vantage point in the depths of the universe. Yeah, forget about the frequency, that's a furfe but the wavelength, the wavelength stretches so the time that the length scale is increasing. In fact, there's there's a thing called the scale factor of the universe, and it's very easy to prove. It's one of the most simple geometrical equations in cosmology. The scale factor of the universe now compared with when the light was emitted. The ratio of the two is equal to one over one plus said, where z is the red shift of the light that you're measuring. And so there's this direct link between the sort of scale size of the universe, which is the length of meter effectively, and the red shift that we measure when we look deep into the universe. You look as you've got a question. Now I'm confused. So what you basically say in regard to his question that the met is expanding? So a meter is not a meter? Well, it's it's still a meter, but it's a different meter, okay, because the scale factor of the universe was less when the light was emitted. This is the thing, you know. You've got two different reference frames here. That's why this stuff gets a little bit complicated because in our reference frame, the meter is longer. But if you were traveling along with your meter stick as it as it sped through the universe, it will be changing in length. It would it would sorry appear to be the same length. Right, I'm sorry. This is just it's mind bending, mm hmm, isn't it it? It bends mine as well, and something similar happens to time. But once again, so we are we're still inside the universe, but where we're observers from in a different reference frame from when the light was emitted. Because that's what we're talking about. We're talking about being able to measure the expansion of the universe through the through the light waves. So so and we know that time dilation took place, we can we can measure that by looking at this rise and fall rates of supernova in the distant universe, and they actually appear to rise and fall slower, So it is the time element of that changes as well. Okay, I think he chose a meter because the meter was defined by the International System of Units as the length of the path light travels in a vacuum during a time in the interval of one two hundred and ninety nine million, seven hundred and ninety two four hundred and fifty eighths of the second. Yeah, that's how it's that's how it's defined today. Originally defined as being what was it, one four hundred thousand of the circumference of the Earth. I can't remember, Yeah, I. Can't something like that, all right, okay, so well it would be one forty yeah one. Anyway, so it was it was. It was related to the circumference of the Earth. I don't do the sums anymore. My brain's fried today. I don't know why. I mean, you're right, I think it's episode three six hundred. Yeah, is a relativistic phenomenon taking place here. It's just messing us up. I mean, we need a holiday of some kind. But anyway, hopefully that helped Peter, I don't know, but I think somewhere in there we did answer a question. Thanks for sending it in, and and good to have a very Scandinavian sort of six hundred episode. So yeah, I mean we've got slightly fast, We've got Sweden a couple of times over Norway and then South Australia. Okay, well anyway close enough plus enough. South Australia is not known for its fjords, but it is a nice place. It is a lovely place, except it was pouring rain and gale force wins when we visited. But anyway, that's the way it goes. Thank you Peter, Bjorn, slightly badcast and Darryl for sending in questions. If you've got questions for us, please send them in to us via our website, spacenuts podcast dot com, space nuts dot Io. Click on the AMA button which stands for Ask Me Anything and send us your text or audio questions. Don't forget to tell us who you are and we're from. We'd love to hear from you, especially if you haven't sending questions before. Also, if you'd like to help us out, please wherever you listen to us, leave reviews because the more reviews the better, the more we move up the relativistic food chain that is podcast world, and we get more listeners. Perhaps that's that's the aim of the game. Anyway, if you do that for us, that'd be great. And Fred, thank you very much. Nice to chat. We'll catch you on the next episode. Sounds great, Andrew, I hope we get our breath boat before then. Yes, yes, it's been a bit tiring, hasn't Itred. We got there in the Professor Fred Wartson, Astronomer at Large, and he'll be back with us next week here in the studio. We thank him too for all the work he's done over these last well actually he doesn't turn up for most so the last four episodes that he's been with us. In fact, he couldn't be with us today because we told him he could have every six hundredth episode off and from me Andrew Dunkley, thanks for your company. We'll see you on the next episode of Space Nuts. Bye bye. You'll listening to the Space Nuts podcast. Available at Apple Podcasts, Spotify, iHeartRadio, or your favorite podcast player. You can also stream on demand buy dot com. This has been another quality podcast production from Nights dot com