#464: Dark Matter Dynamics, Spacecraft Synchronisation & Asteroid Belt Enigmas

Hi there, thanks for joining us. This is Space Nuts Q and A where we answer audience questions, and on this episode we're going to be talking about the relationship between dark matter and the cosmic web. We'll also look at an issue that's been raised about the synchronization of communication between Earth and long distance spacecraft. How do they do that because they're moving at rat of knots at great distances away from us, so how do we talk to them. There's also questions about whether or not there's more than one asteroid belt and can we build a space wheel. We'll tackle all that today on Space. Nuts fifteen seconds guidance in Channal ten nine ignition. Sequence Space Nuts or three two one Space Nuts. As when I reported Bill's. Good, here he is again, Fred. What's an hello? Fred? Hi, Andrew? How are you? I'm as good as the last time you saw me. I'm even wearing the same shirt. Strangely enough, it's extraordinary, isn't it, Soli? What a coincidence? Amazing? Are you ready to tackle some questions? Why not? All right, let's get down to it now. Our first question or questions come from the same source, and it's Ben and he's got a couple of interesting ideas. He says, Hi, there Andrew and Fred, longtime listener, but first time questioner from Chicago, though originally from Australia. Just in the form of a text as I'm one of the lucky sods who's gotten COVID twice in two months and can't talk. I'm sure some people can appreciate that. Just have two questions, not related, and of course one is going to be about dark matter. Fred mentioned in an episode that matter and dark matter don't interact, and one way of seeing that was some galaxies have moved over time, but the blob of dark matter doesn't move with it, to paraphrase. But if that's the case, my question is, how did dark matter form the cosmic web pattern of the universe in the first place. If it doesn't move, since galaxies are theorized to be held together using dark matter, wouldn't then wouldn't then moving off the dark matter blob mean they would start to fly apart. That's his first question. We'll get to the second one after we've solved. That riddle thread So that the interaction there is an interaction, which is via gravity. The least understood of all the fundamental forces, and that's why you know, if you've got a unif some baby universe that's got this web of dark matter, because that dark matter has gravitational interaction, then it will pull the normal matter in, so you do get you know, the galaxies strong, all out, strong, out along the cosmic web, as we find today when we observe galaxy surveys and things of that sort. The point I was making about the lack of interaction of other kinds, in other words, that you know, they don't bounce off one another. Was a couple of examples where we know that clusters of galaxies, which are the biggest sort of objects in the universe, they've collided and the gas and stars in those galaxies have sort of ground to a hole in the pile up. So what you end up with is a big blob of galaxy debris, except it's not debry. It's much the same as it was before they interacting, but they're gravitationally probably pulling one of an apart and. Things like that. So you've got two galaxy clusters, they collide, and you get a smash up there, which you can identify as being two different galaxy clusters colliding, but the dark matter from each of those because each of those clusters would have had its own dark matter halo. The dark matter just carries on. It doesn't interact either apparently with itself or with the debris the normal matter. So what you've got is. A scenario where you've got a new cluster of galaxies that's been formed from the two colliding clusters, and on either side of it is a blob of dark matter, which is the dark matter from the two original clusters that's just carried on going because it doesn't impact the normal matter. It does gravitationally, so it'll tend to have a gravitational influence on it, but the dark matter basically just just carries on. I'm very confusing for it. I can understand why we get so many questions about it, because it just doesn't seem to make sense. No, So the only thing that makes sense. Is that the particles of dark mutter normal matter door sort of bounce off one another, but they do have a gravitaxial effect on each other. That's really the way to put it. Okay, that makes it sound a little bit more simple, I hope. Now. Ben's second question, which is for spacecraft Communicating with them takes obviously longer and longer the further they are away, with all the planets moving all the time along the gravitational along with gravitational differences, the further or even closer to other orbital bodies, how do we keep the spacecraft synced to Earth perfectly? Would we, for spacecraft very far away, have to pinpoint or point telescopes further ahead of where they will be if it takes hours for the signal, or if it's close to a body like the Parker Solar probe. Would that not mess with the signals with delays possible or possibly the signal bending somehow. I'm sure these are taken into account, but I just wonder how people plan for it. I know telescopes account for this with redshift, but I wasn't sure how two way communication with satellite probes works. That's a really interesting question because we take for granted that we can still communicate with Voyager, and it is way beyond anything else that we've sat out so far. Right, it's twenty two light hours away at the moment I remember, Yeah, So yeah, it is a good question, but it can all be compensated for, and in fact the ben mentions the signals. And there's a classic case of I think it was the Cassini spacecraft when it was on its way to Saturn. This is in the early two thousands. It was at one point behind the Sun to us, but we could still see the signals because they were being bent by the gravitational effect of the Sun, just like light is. You know, it's the general relativity says that gravity will alter the direction of a beam of light or a beam of radiation. Then that was one of the ways. Actually, the Cassini observations of signals coming from the you know, the spacecraft being on the backside of the song but still being able to see the signals was one of the again one of the confirmations of gravitational deflection of light. Once again, you know, underpinning relativities absolutely fundamental place, you know, understanding of the universe. And yes, if you if you had a spacecraft that was moving across our line of sight and occasionally they are doing because they're you know, if you've got gravitational sling shot maneuvers, that might well put the spacecraft on the trajectory that's going across our line of sight. You do need to aim your your radio telescope ahead of it. You've got to you've got to take it into account, and people do that and it's completely routine. So because we understand what the orbits are doing, it's uh, it's basically a routine, you know, a routine maneuver or maneuver of telescope operations. Probably the person to talk to you about this is Glenn Nagel, who looks after the Tidbin Miller tracking station, one of NASA's deep space tracking network, which is stop far from camera. I might talk to him about it next time, I seeing. Yeah, why not? So Ben was pretty spot on with his salrus. Ben goes on to say thank you for answering this rambling and for the wonderful podcast. He said, I also worked for the ABC in Ultimo for a while. That's in Sydney, so maybe we crossed paths Andrew and never knew it. I was in the dark corner of the newsroom, Ben. I never got to the newsroom much. I think I actually only entered the newsroom once in my life, and I could feel the tension the moment or walked in. I know they talk about the atmosphere of places creating certain awareness amongst humans. I've never felt more intimidated than the Dale walked into the ABC Radio newsroom. I could feel how I don't know how deep the place was as an observer, and that's where they make all the news and current affairs programs for ABC in New South Wales. And I yeah, look, I don't envy you being there. I couldn't have worked in that environment. It was just too much for me. I liked my little regional radio job out in the Sticks much more, much more relaxed. Thank you, Ben. Great to hear from you, and hope all is well in Chicago. This is Space Nuts with Andrew Dugley and Professor Fred Watson Space Buds. Let's get some audio questions sorted out. Fred, and one of our regular sender inters is Sandy from I'm going to say Melbourne. I said that last time when I was wrong was a Brisbane I don't know Sandy somewhere my. Fred, Sandy from Melbourne a game. My question today is about the asteroid belts between Mars and Jupiter. As I understand, that's where the the primary asteroid belts are now, is there any other asteroid belts that's past the orbit of Jupiter, so I'm preferring to perhaps out towards Neptune that sort of or. Uranus sort of sort of distance. I'm assuming the answer is known, And if the answer is no, how come they've sort of massed together between Jupteri Mars and not further out. Thank you, Thanks Sandy. If you've got asteroids around Uranus, I think you should the doctor. But they're more likely to be emerhoids. Sorry I couldn't help it. Yeah, yeah, and look, I like the question because my first thought is we'll hang on the asteroid belt, yes, know all about that. Is there another one out there? And I just thought, well, it's the Kuiper Belt, but is not the same, is it? Or is it the same? Yeah? Right, Andrew. It's true that there are other asteroid belts, and they're quite different in character. So Sad is right that the main asteroid belt is the one and the most highly populated, is the one that lies between the orbits of Mars and Jupiter, and that's been known about since the early nineteenth century. The first one of those series was discovered on the first of January eighteen hundred and one, and that set the pass for you know the understanding that there is a belt of small objects between between Mars and Jupiter. We used to call them minor planets. In fact, when my MSc thesis is called the determination of minor planet orbits where you go. So that's what we now call the main asteroid belt. Actually, Sunday is right because he's talked about it as being multiple belts, and in a way there are different families is within those asteroid belts, within that main asteroid belt, if I put it that way. We talked about some of those in the last episode of Space Notes. Now as regards other asteroid belts, yes there are, and as you said, Andrew, the Kliper Belt is what really comes to mind. And that's just one of a number of different groups of icy asteroids which are beyond the orbit of Neptune, which is why they called trans Neptunian objects. One of the bigger ones is called Pluto, but it is just one of the bigger ones, and there are different families within that group of transit Tunian objects. There are objects called classical Coiper belt objects. There are objects called resonant objects where they have a resonance with the orbit of Neptune. And then the most distant ones are called scattered disc objects. So these are three different groups of objects which are in that to asteroid belt. They have a different formation we think from from the inner asteroid belt, because mostly I see those objects as we know blue toys, and that means that what we're seeing is a family of objects that really are the remnants of the of the of the cloud of dust and gas from which the Solar System formed. It's the outer extremities, objects that have never been warmed up by the Sun, the star that formed in the middle, whereas the asteroid belt is principally rocky objects, and we think it's just a sort of cloud of debris that's been shepherd in into that particular orbit between Mars and Jupiter by the huge gravitational pool of Jupiter. Jupiter's gravitational influence is enormous on the other planets and the minor planets, and we think that's what it is. There's a region between Mars and Jupiter where debris is collected and probably it's still primordial damer it's the rocky material from which the planets were made, but it was never able to form a planet because it's giant right next to it, as gravity is kind of swishing. It around a lot. So yes, logical reasons why we understand these different sorts of belts. What about the oat cloud? Yeah, would that be an asteroid belt of some kind? I'm meant to mention the oak cloud. Thank you for reminding me, Andrew, that's more of a sphere of objects rather than the belt of objects. I mean, we think of a belt as being within the plane of the Solar System, as indeed the asteroid belt is. The Transceptunian objects are much more highly inclined in their own bits, so they're not really a belt, but they're more like a belt than the Oak cloud, which is thought to be something that surrounds the Solar system completely. And yes, again it's the outer edges of this blob of gas and dust from which the Solar System formed. So the oak cloud is where the bits come from, and they are mostly made of vice. So that's a big difference. Yeah, all right, So the answer to say Andy's question is yes. Ish, it's yes, and it's big time yes really because we've got you know, so much more that we now know about the Solar System, and it's various families of minor objects, small objects which are important to us because these things occasionally collide with the Earth, so that's why we need to know about them. It would it be logical to suggest that these kinds of belts exist in other solar systems. Yeah, I think so. There's the problem with trying to discover them is that the objects in them are so small that they're you know, trying to detect them from from the distance that we are, which is measured in light years rather than millions of kilometers as we are in the Solar system. That's a difficult task, but maybe one day we'll find some evidence. There is actually evidence, there's evidence of comic clouds. For example, around one star from below if I remember rightly had an object that was in its protoplanetary disc that's the disc of stuff that's got a form planets that actually broke up into into pieces, and it's thought to have been an asteroid collision. And we've also seen a very peculiar star that has a brightness range that changes, and the thinking is that we're seeing a cloud of comments passing in front of it. So yes, there evidence is there, right. Okay, thank you Sandy, Great question, and yes you were right. Okay, we take a. Space neuts. Our final question today comes from Steve. Hi. Guys, it's Steve here from Liverpool and England. Actually just across the river from Liverpool, so technically plastic sculpture. Just a question reference. Do you ever think a Von Brawn wheel or you know wheel space station will ever be built? It's within our capabilities now, I think, you know, with multiple launchers and modular design they could even sell different modules to hotels, et cetera. But do you think it'll ever be built? Thank you, take care and calling on with the show. Cheers, Good on your Steve. Thank you. I'll be visiting Liverpool sometime next year. Can't wait. Can't go to the Beatles experience and do its grown. That's exactly what I'm going to do. Yeah, I'm going to do the Beatles Tour. Yeah, space Wheel. The first time I ever became aware of space Wheel, Fred was when I was a kid and I used to watch a TV show called Space Patrol. It was one of those marrying it type shows. Yeah, they Captain Scarlett was was probaly will be the most famous of the shows. This one was called Space Patrol and one of the space ships was actually a space wheel that I don't remember much more about it than that. I do remember a strange space creature called Gabbler, and they were trying to teach him to say medicine, but he kept saying pencil instead. Look, I don't know why that's stuck in my head. Say pencil, Say medicine, Gabler. He'd say pencil. Or was it say pencil, Gabler, He'd say medicine. It was. It was a sweet, some weird interstellar bird. I've got some strange memories from my childhood, but that one sticks out because of the space wheel. Do you think we'll ever build one? I do, because it is, you know, the most direct way of trying to provide well, that's the only way we know of trying to provide an artificial gravity in a spacecraft that's away from the Earth. You've got to be very careful about it, though, because there are only certain limits between which you can build it in terms of diameter and how fast it rotates. What gives me some confidence in this is a conversation I had. It's quite a number of years ago now, but with the husband of Linda Spilker, Linda Spilker was the mission scientist for Cassini for the Cassini Space mission. Her husband Tom is the space engineer contracted to NASA. He was at the time, I guess it problem still is and his specialty is space wheels. It's all designing the possibility of these large rotating structures in space that will give you artificial gravity. I know, when I think of the future of humankind, I tend to think of them not as colonizing Mars, which I think would be a bad thing to do, but I think of them building megastructures in space which might have artificial gravity, a bit like the Halo world from that very well lit early game. Oh yeah, it was in the early years of the century. Love loved playing that game with the boys when they were at home. And of course they made it into a TV series, although they've got canned after two seasons, but yeah, it's become a huge franchise. Did you know I might have mentioned this before, but in Halo there was a Private Chips. Dubbo, one of the characters. Yeah, Private Chips Dubbo because and he had an Australian accent. And well there you go. So he appeared in the first version of the Halo video game, Private Chips Dubbo because I'm from Dubbo. This is where I am. So yeah, so somebody must have. Yeah, it's a great name. Love it. And he didn't get killed off. He wasn't he wasn't a Red Shirt. Sorry I'm getting I'm digressing. Space wheels, Yes, but you're right that was the Halo was a space wheel, a big one. Yeah. And if we could lost to the engineering to build something like that, I think that's a far better way than colonizing a lot of the world that might have, you know, rudimentary microscopic life on it. So if you build a space wheel, and as you said, you've got to be careful because of size and speeds and creating that oneergy effect, would bigger be better because you wouldn't have to rotate it nearly as fast or I don't know. Yeah, Yeah, it's a it's a fine line between the two. It's I looked at some of the work that Tom Spilker is done, and you know, you you've you've wanted big enough that it mimics gravity rather than making you feel sick, which is what happens with the smaller ones, and you know you want you want to ensure that if you if you drop something in this artificial gravity, it just goes directly downwards rather than moving sideways, which if it's too small and rotating too quickly, then it would do or moving. I'm just thinking all these questions as I go. But if you did build a space wheel in orbit around Earth as a hotel or whatever, a research center, probably both in years to come, and who knows what else, But would you have it pointing at Earth on its axis or on its wheel? Because if you if you had it sort of wheel up, then you'd be standing with your feet in proximity to Earth. But if you put it on its axis, you'd actually be standing sideways. Yes, I think what you might do both, couldn't it? Yeah? You could? I think you'd. You you you know, I'm guessing here that what you'd want to do is really aligned it up in terms of where the Sun is. So if you had it with its axis pointing towards the Earth, but in a geostatiary orbit, so it was going around the Earth once a day, that would mean that you'd sort of limit the twenty four hour cycle of night and day. In a way that you wouldn't if it was some other way. That's a good thought. Yeah, actually that's a really good thought. Yeah, I know, trust you to come up with a better idea than me. Yeah, I'm glad did that makes perfect sense? So the answer is yes, probably it will happen. Why hasn't it happened yet? I think they've been focused on other things for it. I suppose it's fairly significant engineering. You know, there was certainly talk of earlier in the idea of sending people to Mars, probably a couple of decades ago, of making two spacecraft that are tied together and rotate about their common center of gravity and that basically provides artificial gravity. But even that turned out to be just a little bit beyond the engineering we've got at the book. Although we sound like we're going to get there. Thanks Steve, I hope you will, hope all as well in Liverpool, and thanks for your questions. We've got a whole bunch of new questions that have come in that we're going to get through. That doesn't mean you should not send them to us, So go to our website, Spacenuts podcast dot com or spacenuts dot io and have a look around while you're there. But if you've got a device with a microphone like a smartphone or a computer or whatever, you could send us audio questions. Just don't forget to tell us who you are and where you're from. Or you can send us text questions via the AMA link on our homepage. And that's about it, Fred, thanks so much for answering all those questions for us today. It's a pleasure. It's what I do, so I'm likely to do that all right, and we'll up with you again real soon. Fred, what's an astronomer at large? And here in the student video who I think was taking the bins out when we started this episode and we I've got to do that. Thank you, interesting to do it tomorrow. Uh, And from me Andrew Acpley, thanks for your company catching on the next episode of space Nuts. Until then, bye byepaceus. You'll be listening to the Space Nuts. 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