#470: Cosmic Questions: Dark Matter, Titan's Secrets & Universe's Energy

Hi there, Thanks for joining us on a Q and A edition of Space Nuts. Andrew Duntley here, your Host's great to have your company. In this episode, we are going to talk about the universe without black holes, dark matter or dark energy. What would it be like? Yeah, probably completely different, mightn't exist at all, don't know. We've also got a question about loss of energy and the age of the universe. Another universe question, the early universe and all the matter and the stars and things, and why we get so surprised when we discover something that's old because it's all been there from the very beginning. It's a good question. And Titan's atmosphere has come up from one of our audience members. So we'll answer all of those questions today on Space Nuts. Fifteen said in channel ten. Nine ignition Space Nuts NI or three. Two more red one Space Nets and I report it Neils good. And he's back again for more. Can't believe it. It's Professor Fred Wat's an astronomer. La. I can't believe it either. How you doing, Andrew, Well, well, yeah, thank you, you're looking well to you. In fact, I would go as far as saying that since you left the public service you seem a lot, you seem a lot less tense. A lot. How it's really interesting because I don't have to scan my you know, my government laptop every morning to see what meetings I've got during the day, and that makes the day a lot more relaxed. I do still on the meetings, but they're under a lot better control. Yeah, well that's good, that's good. Shall we tackle some questions? Well, let's attempt it. All right, Let's go to our first one that comes from Reynold or he may pronounce it Renault. How would our universe behave without black holes, dark matter, and dark energy? At what phase did dark matter and dark energy appear? That's a double banger. What do you think for it? Yeah, I think it's a profound question, and you know it's at the forefront of modern day cosmology. So we think that it was the dark matter that really caused the ability of the universe to form galaxies, well, stars and galaxies, because what we think happened was that the dark matter came first and sort of coalesced into what we call the cosmic web, this kind of honeycomb structure of sheets of dark matter, which attracted the hydrogen that that stage pervaded the universe to form a similar structure because the hydrogen collapse gravitationally to sort of mimic the underlying dark matter structure. And then, excuse me, during that collapse, many stars were formed. Star formation took place, Galaxies formed because the stars that you know, they all formed in these large blobs of matter. And we see that today. We still see when you look at a structure of where galaxies lie in today's universe, you find that they make up this honeycomb, which basically mimics what we see in the cosmic microwave background radiation, which we think is the precursor of those galaxies. That's the sound ways going through the early universe. So we think that without dark matter, the universe will be very different and wouldn't have this underlying web, and maybe galaxies and stars wouldn't have formed. That's really interesting. So now dark energy go ahead. No, I was going to say, so if dark energy was the driving force and it didn't exist, would our universe have formed at all? Anyway? Well? Yeah, dark energy is that different things? It's the. Yeah. So with that, yes, dark matter would think would is what allowed galaxies to form out the universe itself might have formed. We don't really understand the Big Bang well enough to know just where it all came from, but we might have had a universe devoid of dark matter, just full of cold hydrogen and not really doing anything. So that's pretty boring for the universe. And dark energy, it really is a property of the expansion of the universe, so it's set telling us that space itself has energy. So I think the second part of our renal question is at what phase did dark matter and dark energy appear? So we think dark matter appeared right at the beginning. Now, dark energy was probably always there. This is a hot topic in cosmology, but we think it's only manifested itself in the last five or six hundred sorry, the last five or six billion years, in other words, about half the age of the universe. And we think that's probably because dark matter. Dark energy might have been there all the time, but it didn't have enough energy to cause the universe's expansion to accelerate, which is how we see dark energy. It didn't have enough energy early on because the galaxies and stars, the galaxies themselves were too close together and their neutral gravitational pull was enough to sort of slow down the dark energy and hide its effect. So we think dark energy might always have been there. The big question is as if evolved, because for about the last twenty years, the thinking has been that it's a constant that it's a property of you know, the same amount of dark energy per unit volume of space per cubic centimeter if your like of space. That so it's said that, in other words, the dark energy is proportional to the volume of space. So as the space expands with the expansion of the universe, that you get more dark energy. But the thinking now is that maybe that's not quite true. There might be a slight evolution effect over time, which is still being explored. So another piece of his question was, you know, a universe devoid of black holes, what would that be like? Yeah, we think black holes are a natural consequence of the formation of stars and galaxies. Without a universe without black holes might not be that different because until forty or fifty years ago, we thought the universe didn't have black holes. That's true, and it's only by a lot of fairly detailed and careful research that we've discovered that the black holes everywhere. Yeah, So yes, that's an interesting question. I don't know that the consequences there would there will be a lot less high energy events going on in the universe. We wouldn't see quasars for a start. Quaisars are powered by black holes, the delinquent galaxies with a black hole at their center. HM. Okay. But if you didn't have any of that, in any of the black or dark stuff, you might just have a universe that's full of hydrogen, looking pretty boring. I suppose it might be the odd reactionary event that would create something, but it wouldn't be wouldn't be much to look at. It to be Boarsville. Yes, well, it would be Boarsville because without the formation of stars and galaxies, in particular stars. Without the formation of stars, you don't get the heavy elements. All you get is a universe with hydrogen, helium, a little bit of lithium, and a couple of other things, and that's it. So it would be a very boring place. And talking of that, that is one of the main targets of the square kilometer array, because cold hydrogen actually radiates in relatively low frequency radio waves, and the square kilometer array is going to be able to look so far into space in other words, so far back in time that it can see the dark ages when the first stars have not yet come into being, and all there was was cold hydrogen. So the built and map that cold hydrogen and see whether it does actually fall on the cosmic web as we believe it did. Fascinating, fascinating. Reynald the Answery A question was it'd be a very different universe without any of that stuff. Probably pretty boring, and it was probably always there at the beginning dark matter and dark energy perhaps as well. So yeah, it's a great question, Thanks for sending it in. Our next question, Fred comes from one of our regular although we haven't heard from him in a while, Sendor Interes buddy. Most case, that's his buddy from order again. How much is they energy of the universe is kind of like gone Basically. He's never going to touch anything or is going to just continue forever like light or gravitational waves, plus maybe the potential of the energy. Of moving object. How much of the viewers's energy is tied up that way? Gay, I got one? Not one more question? Is it possible to calculate the age of the universe from the half life of uranium or liquum. All right, guys, keep up the good work, love the vodcas. Thank you, buddy. That's two very very good questions, so we'll tackle them one at a time. He was asking about energy that's been lost. In the universe. I assume he means over the time the universe has existed, there was a big bang, everything expanded very quickly, and then it slowed down out speeding up. There's a lot been happening over billions and billions of years. But is there energy loss in that process? A great question that I'm thinking aloud here, Andrew, So, so, yeah, the energy budget of the universe is really interesting because it sort of ties in with the mass of the universe as well. You know, mass, as we know, has an intrinsic energy. Buddy is talking about the kinetic energy of moving objects, and that's certainly an energy component, but I think it is vanishingly small compared with the equivalent of the mass of the universe when you convert it to energy with the equals mc squared. So most of the energy of the universe is tied up, sorry, most of the Yeah, so most of the energy of the universe. Getting myself into knot here. If you regard mass as part of the mass energy budget of the universe, and you can draw a pie chart, the stuff we can see is about five percent of that energy budget. So that's all the mass equivalent the energy equivalent of all the mass in the universe, and it's very very small compared with dark matter, which is about five times bigger. And then the rest, which is seventy five or eighty about seventy five percent is dark energy. So dark energy is by far the biggest energy content of the universe, and the rest almost doesn't matter. You know. It is an incredible situation that we have that the biggest energy component of the universe is something we actually don't understand, making the universe expand ever more rapidly. So yeah, really very very interesting. Just moving on to uranium. Uraniums are not something that you can use to determine the age of the universe because it was created in super and over explosions which occurred after the universe was formed. With heavy elements like uranium are created within massive star either collisions, neutron star collisions, or massive super and ova eruptions. You can use uranium obviously, it has a half life, and you can. I think that might be one of the ways that you determine the age of the Earth. Actually, when I think about it, four point six billion years, I think the age of the Earth is partly due to our understanding of the radioactive decay of isotopes like uranium. So yes, it's got a place in cosmology, but not in regard to the Big Bang itself. Okay, you also mentioned lithium same day, did. Yeah, Now, lithium is not That's what I was just looking up. It's I think I'm not aware of the radioactive properties of lithium. Let me put it that way. Okay. Yeah, Well, we know about its properties when it comes to energy use on Earth, and it's a dwindling resource. So they've got to find something else eventually. And I think they're are working on sodium batteries and there's plenty of that stuff around. But yeah, So if you can't use the half life of uranium olthium to calculate the age of the universe, what do you use. The first way it was worked out was simply by the measure measuring the Hubble constant, which is the rate at which the universe is expanding. If you invert the Hubble constant, you get the time how long it's been expanding for You can basically use that simple number to work out when everything was altogether in one place. But that assumes that the expansion has been uniform throughout, and we don't believe that's the case now, so you've got to modify it. So these days it's a combination of looking at the distribution of galaxies in the universe, plus are observations of the flash of the Big Bang, which we could still see, of course, is a cosmic microwave background radiation, and you can deduce from that how the universes, because you know, it was visible light when it left and it's now microwaves, and that's the central calculation as well. Yeah, I suppose in terms of dwindling energy or lost energy in the universe, you can you can look at I think we've spoken about it before. You can look at photons, which do die, especially if they hit something, but that energy transfers into something else, does it. That's correct, Yeah, so it's conserved. That's right there. You go. Okay, thank you buddy. Great to hear from you. It's been a while. I hope you're well, our next question comes from Oh, hang on a second, we've got to do this first broad piece MUDs there we go, always got to check one of those in. Ben has sent us a question, and Ben asks, in the early universe it was physically much smaller, but the total amount of matter slash energy was the same, so everything was much closer together than now. So wouldn't that make it much easier to build stars, galaxies and stuff, even super massive black holes? Yet we are supposed to be surprised that these structures existed in the very early days. Why so I would be surprised if huge compact structures didn't form quickly as the ingredients were so readily available, Ben Hardy, Thank you, Ben. We've kind of been talking about that stuff as a part of today's program. And yes, you bring up an interesting point. We get excited when we find a primordial black hole or an ancient galaxy that seems to almost be as old as the universe itself, which has happened in recent times. Should we be surprised, Fred or is been onto something? Look, it was all there in the first place. Why are we getting super super excited about it? So? Yeah, so if our models galaxy formation were perfect and the perfect representation of reality, then we wouldn't be surprised because the models will predict that. But the models need fine tuning, so those surprises are I think. To be honest, they're often beat up by the media, including its base notes. So there is an element of you know, researchers who are the ones who put together models of the way galaxies form and evolve. They're the ones who've in some ways had to rewrite their models. They've had to tune the parameters. We had a talk at the fiftieth anniversary of the End of Australian Telescope, that symposium that I was chairing as the local Organizing Committee chair sorry Science Organizing Committee chair not very long ago. One of the talks was about exactly this, and that particular speaker said we shouldn't be surprised that these structures formed so early in the universe because the ingredients were there exactly as Ben says, But you know, there's a bit more to it than that. You've got to have the gravitational pull that's provided by that cosmic web structure that we were talking about a few minutes ago, that needs to be in place as well, and that must have formed very very early on in the history of the universe. That's what we learn from the square kilometer array. We might get surprises from the square kilometer array as well, because we think there is at least, you know, at least a time of more than one hundred million years when the universe went through the dark ages there were no stars shining. Now, that might turn out to be an underestimate or an overestimate, and it might surprise the theorists when we start to get the results from the square kilometer array, which won't be too far down the track. I don't think maybe two thousand to ask you. That it can't be too long before they switch that on, but it is still a while. Yeah, it's twenty twenty eight or thereabouts. Yeah, right, but there will switch on bits of it beforehand, so we might glean stuff. It is an array, so you know, it's not just a single telescope. Yes, tell us, Yeah, it. Was very good, Thank you, Ben. I think we basically answered it that yes, because of modeling and it's not an exact science. These discoveries are quite surprising from time to time, and not all us stuff was there in the first place, I suppose fred because the consequence of the Big Bang and that mix of materials that created more materials and new materials and new discoveries being made as a consequence of that, I suppose. Yeah. So, I mean the modeling of the Big bangs fairly pretty well. So up. And then it's within the first few minutes that you actually get atoms forming, but they are hydrogen and helium. Uh. And then you've got to wait a long time, probably one hundred million years before you started getting carbon and oxygen and the other things that are formed by the interior of stars. And that you know, that's a fairly coherent picture, which, as I said, will be demonstrated, we hope by the square kilometer ray. What will be a surprise there is if they when they analyze the signal coming from that early gas, if heavy elements were present in that early prime audio gas, then we really have to start rewriting the textbooks because at the moment we don't think there were any. So there's a there's a challenge for the square kilometerra and that would probably win a Nobel Prize a discovery like that. Yeah, I imagine. So, so Ben's basically asked his question, A few is too early. Yes, that's right. So if a Nobel price came from that, it will please me enormously, because I'm on record in Hansard as having promised the government that the square kilometer array would win a Nobel prize. Oh day, Yeah that was a few years. I'm just going to write a note because we're going to follow that up. Okay, thanks Ben, Okay, we take space nuts and our final question today comes from youngst. Hello, space Nuts. This is the young from the Forest of Dalston and Sweden. As we all know, Saturn's moon, Titan is a very special place. So here's my question. How did Titan become so special? How did it accumulate stick nitrogen atmosphere and know it's meeting and eating so does some months of out planets. Only Titan has an atmosphere. What is it about Titan that made it become different from all the other moons? And another related question. This often said that Mars is too small to retain an atmosphere in the long term, the Titan is even smaller. How came Titan carry in an atmosphere when Mars cannot? Thanks? Very great show, Thank you, Yes, great to hear from somebody in Sweden and gee, that were great questions, especially that last part comparing Mars that couldn't hold an atmosphere to Tighten that's smaller, that can hold an atmosphere, and had it Titan get its atmosphere in the first place because it's unique. I think that was a reasonably good paraphrasing it. Solo phrases it very well. Yeah, and I can paraphrase the answer, which is basically, I don't know. I'm home. Yeah. I think we will do some of homework on this, but it's a great question, yes, and I just thinking about it. You know, with Mars, the obvious difference between Mars and Titan is that Mars, well, Mars is bigger than Titan, but Mars is much closer to the Sun and so well, it's not in the Goldilock zone, it's it's near enough to the Sun that we think the Sun's radiation. By that, I mean the sub atomic particles has helped us strip off the atmosphere from Mars, which is you know, some of it, some of it is water, baker that's frozen frozen out, a lot of that, but a lot of it was dissociated into well, the water was certainly dissociated into hydrogen and oxygen, and the hydrogen has just gone into space. Yeah, likewise, probably some of the carbon dioxide. It's so I think it's there's a temperature difference there. But once you get to Jupiter, now Ganymede is bigger than Titan, Ganymede doesn't have a sceric of an atmosphere. There's nothing there at all. So it's a really interesting question why Titan should have that thick atmosphere. And I am not an expert on planetary signs, but I will take that one un notice because I think that's worth following up just to find out. It's such a great question, and it's a you know, it's glaringly obvious. Why is this body in the outer Solar System? Why is it clung onto an atmosphere that is thick and murky when we've got a similar sized object, Ganymede, not that far nearer to the inner Solar System in orbit around Jupiter, that doesn't have any side of an atmosphere like that. So that is one I'll come back to and thank you for the question. Just throw it. There could be something to do with the volatility of Titan. It's it's it's volcanic, is it not? And it's throwing up a lot of these nasty, smelly guesses. And could it constantly be renewing its atmosphere, which anyway it cannot. Perhaps these are the cry of cry of volcanoes. We think it's a mixture of water and pneumonia that comes up from them and not, you know, not what the kind of thing that we imagine when we think of a terrestrial volcano. So the volcanoes are coming up from the ocean layer beneath the ice of Titan, because titan surface is solid ice, as we believe it is Ganymedes. So it's a it's such a contrast, I mean, in a sense. My first thought about this was, well, gas giants are you know, they grow their gasiness because they've got a massive core that's been built up by the fact that that the beyond the ice line so is has formed and they've got probably got an icy core. Whether you can apply the same argument to Titan, I'm not sure. I need to check on that. So, yeah, thanks for the question, and we'll we'll have a look at it. I'm going to put. We'll put a pin in that one and try and come back to it in a later episode. But great question. It's very very good. And hope all as well in Sweden. Are you're heading into the colder month so I won't be visiting for a while, Well we will. We'll be there next not next month, but the month after. We've been so wonderful. Ye, excellent. Okay, that's it for today. Thanks to everyone who's sending questions. Don't forget you can send us questions as well via our website space nuts dot Io. Just click on the A M A link up the top and send us your questions through that and have a look around while you're there, particularly the space nuts shop or the space Nuts support a button if you want to push that. What it does is as soon as you push that button, it sends out a trojan and and your bank bank account. No it doesn't, No, no it doesn't. Don't even joke about that. No it shouldn't. Really good grief, No it doesn't. It's purely voluntary. Thanks. Fred is always great to chat and great questions again this week. Well they're just they're terrific questions. Yeah, thank you very much everybody, and Thanks Andrew. No worries, catch you soon, Professor Fred Wat's an astronomer at large. And thanks to Hu in the studio for telling me about the trojan horse problem we've been having now and I'm kidding again No he didn't, although he's working on it. And from me Andrew Dunkley, thanks for your company. Will catch you on the very next episode of Space Nuts. See it then, Bye bye Nuts. You'll be listening to the Space Nuts podcast. Available at Apple Podcasts, Spotify, iHeartRadio, or your favorite podcast player. You can also stream on demand at bites dot com. This has been another quality podcast production from nights dot com.