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We are ready and waiting to answer your questions that you sent in. Keep them coming. You can send us a question by emailing us at podcast.res.ac.uk or message us on Instagram at SupermassivePod. I'm not going to lie. We have had a flurry of quite difficult questions. Oh gosh. They're very good. Excellent. They're very good. But I'm just going to let people know that if you're sending in other questions, we do take silly ones as well. Yes, easy ones. Easy ones too. Once I don't make my head hurt. I have the easier job. I'm just the messenger. It's great. OK, so buckle up, Becky and Robert. Becky, let's start with this one from Peter in the Netherlands, who is pondering about leaving the sailor system. His email says, Hi, Dr Becky talked about interstellar passing objects in her December edition of Night Sky News on YouTube. And now I find myself wondering with the idea in the back of my mind that we are pretty much flying to and from asteroids, landing there and bringing back samples and that the best plan to avoid an asteroid collision on Earth is to gravitationally alter their orbit slightly with a spacecraft. How much of a stretch would it be to gravitationally tack on to one of these interstellar passing objects? And this way, hitchhike our way out of the solar system. Thank you for your work. It's great. So keep it up. Yeah, that is a really good idea, Peter. And I think most of us would love to grab a sample like a rock from an interstellar object, right, that has formed around another star in our galaxy and then it's been kicked out and it's made its way just to happen to pass through the solar system. Like if you're wondering, does this happen? Yes, we've spotted two so far in the past couple years that have actually done this. The problem is with a mission like this is that, first of all, interstellar objects are incredibly unpredictable. We've no idea when we're going to detect one. We've no idea which direction it's going to be coming from. And also they're usually traveling very fast, right? Because they're moving through interstellar space. They've been accelerated probably by a few sort of like flybys of other star systems. And so they're usually traveling in a range of like 20 to 40 kilometers a second. So catching one almost is the hard part, right? So you've got all these problems to deal with, but we have seen some research papers exploring this idea of an interstellar object sort of interceptor, if you will. So last year we had one from Alan Stern in collaborators. So Alan Stern was the head of the New Horizons mission that went to Pluto. So a lot of experience in sort of this area and they think it'll be possible to do this in the 2030s. So actually not that far away. And I think what's going to help is actually, so ESA, the European Space Agency, has a mission that's launching at the end of the decade in 2029 that's called the Comet Interceptor Mission. And it's going to do exactly what it says in the tin. It's actually going to launch and then essentially wait at one of those stable points in the Sun Earth systems. You know, we talked about Lagrange Point 2. It's where like J.D. Bush tears. It's where ESA's Gaia mission is, you know, that very stable. So it sort of always is the same distance from the Sun and Earth. And essentially, if you pop something there, it'll just wait there and then wait for a comet to sort of appear from the outer edge of the Solar System. Again, this is also quite unpredictable as well, because there's so many of them out there on massive long orbits that we also don't know all of them when they're going to come back in towards the inner Solar System. So we'll just wait there for one to appear and us to detect it and then hopefully be able to intercept it to study the comet. And that'll be really exciting because it's come from the far reach of the Solar System. And that's why we think sort of like water and a lot of all like sort of the life proteins and everything that you might need might come from. So that's exciting in itself for the comet mission. But also people said, well, does it have to be a comet? The ESA's comet intercept mission, like if there is an interstellar object that appears at the right moment, it could also intercept an interstellar object as well if it works out, right? So I think even if it does choose a comet, it's just going to be a nice mission demonstration that this could be possible if you were then going to launch something that specifically was like, I'm going to ignore the comets and just wait for an interstellar object. And in theory, once it was in orbit, maybe around this interstellar object, it had fully caught up with it and done some sort of like gravitational sort of entry into orbit around it. Then yeah, you could hitchhike out of the sources to do it as well. And so yeah, it'd be really interesting to think like, would it get further than like the Voyager probes or something if this interstellar object was moving fast enough and got a big gravity boost from the sun as well. Yeah, very cool. OK, Robert, Liam Collins emailed us and says, what the blooming hell is a gravistar? An explanation for an idiot would be marvellous from Liam after a confused discussion with his son. I think, Liam, you possibly I agree, what the blooming hell is a gravistar and you might be getting an explanation from an idiot in this particular case. It's like I read this and I thought my mind was melted a bit. I mean, not they looked at these before. So it's an alternative to black holes that explains some of the things you see associated with what we think are black holes. And just to complicate matters, the idea appears to be you have dark energy inside it, which we don't even know what dark energy is. It's driving the expansion of the universe. So we've got stuff we don't know what it is enclosed by a thin shell of normal matter that might also be incredibly cold. And to get around the fact that gravitational wave experiments suggest these may not be this may not be the explanation. There's also the concept of nest stars, where there are lots of these things nest inside each other. So I mean, to say I'm not saying this with a great deal of confidence is fair, you know, and that might then mimic the gravitational wave signature. So this experiment obviously, you know, black holes gliding us on. But, you know, I mean, to me, to be honest, it sounds black holes sound pretty wacky, but at least we have good evidence for them. This sounds, I think it's fair to say, rather less likely than black holes do. I mean, it's a great and absolutely bonkers idea. But I admire the the physicists that came up with it. And after several decades, I think we can say that black holes are kind of part of the astronomical consensus, and this is a very exotic alternative. So Pavel Masar and Emil Motola, who proposed it in 2001 in a paper, then, you know, all credit to you guys for coming up with this. But I still tend to think odd, though they are the black holes are the more convincing explanation. But yes, that was that was definitely an out there question and one that left me scratching my butt. I learned something. So that's good. I've always thought grab a stars were just too far fetched, almost like it was like that. Not you agree. Like, yeah, OK, you can do as much as you want with equations on a blackboard. But at some point, you've got to take the chalk away from the theoretical physicist and go, yeah, but. Do you know that you're reaching too far? What does it actually look like? Yeah, you're invoking like a something that we don't even know what it is yet. It's just a name for the thing that's, you know, goes into an expansion. Just put the chalk down. OK, figure out dark energy first. Yeah, we start making. OK, I'm Becky, the difficult questions continue. Misha and Steve in here for cheer. It might be me, sorry if I've got that wrong. Have a question about our universe's fate. They say we recently heard a documentary on possibilities of what the universe is, e.g. multiverse, infinite, etc. They mentioned that if we are in a multiverse, then potentially far, far away in the future, we could create a new universe to escape as our universe comes to its end. But we're confused as to how a universe we would create would be outside of our existing universe. Surely it would still be in ours, therefore also it would die with it. Appreciate that this is a bit unusual, but we don't know where to find answers. Thank you. We love your podcast so much. OK, Becky, I have a cheer on that one. Again, I'm not surprised you're confused because multiverses give me a headache too as well, just thinking about it. Maybe it might help just linguistically to start. We think about the definition of universe, right? It means one, it means singular. And in the physics sense, it's that everything that exists is encompassed by the universe, right? That includes not just like matter and objects that we see, but space and time itself as well. Then there's the concept of multiverses, which let's also be very clear if we ask the last question, also still completely hypothetical. And so I think what multiverses really sort of do is raise this idea of whether there are other universes outside our own. But in this respect, they would be in like other dimensions, perhaps. This is what we know as like the quantum mechanics, like many worlds interpretation of the multiverse. There are then what's known as bubble universes, which... My favourite. Yeah, I know. We did a whole episode on multiverses, actually, if you do want to catch up, maker and Steve. But like, the way you can think of that, I guess, is they do exist outside our universe, but in some, I don't want to say space necessarily, because again, the definition of universe is that everything, even space is included in it. But as you picture it in your three dimensional brain, yeah, outside of our own universe in this sort of bubble. So first of all, this documentary you watched, I think they had a bit of a blue sky science license to just be like, what if? We should have took the chalk away from the producers. And so they would have thought about, OK, if multiverses exist, and if we could create one, like, you know, even having enough energy to be able to do that, everything about how much energy went into creating our own universe, right? First of all, that would require physics beyond what we currently know, not just the concept of multiverses, but the concept of how to create a universe, accessing different dimensions or distances so far in space that we currently can't reach, right? But basically, I think if multiverses exist, then they are completely separate entities from our own. They are independent of our own as well. And that's true of all multiverse hypotheses. There are some that perhaps if there are bubble universes and they're touching the edge of ours, we might be able to detect another cosmic microwave background, but they would still be independent of our own. So if we created a new one, then that new one wouldn't die with our universe. If our universe was dying, it would be its own separate entity. And also another thing that this documentary probably was like, we'll just gloss over this. Even if our universe did come to an end, it's going to be in so many billions or even trillions of years time, depending on energy budgets and all this kind of, you know, how much is in the universe. But let's face it, humans aren't going to be around to see that. Yeah. We haven't been around in like a blink of an eye in comparison to the universe's timeline. I think as humans, we forget that we are not eternal now. Like as a species, like something. I think we've got main characters in the world. We really do have some main character energy. We're going to be around for trillions of years to see this. Literally, we've only just been able to figure out stuff about the universe in the past hundred. So rated in guys, you know, creating multiverses and all this kind of stuff. Like, yes, I think it's like a step past like, oh, if we destroy the earth, then we'll have to go to like Mars or a new planet. Hey, why don't we just not destroy the earth? You know, like, I'm like, not everyone has Wi-Fi like, you know, we know some other bigger steps. Yeah. It's also like, you know, maybe if the universe is dying, we should just die with it. Like maybe that's the universe is. I don't know. You know what I mean? It's just like, we're not going to be around to see that first of all. We won't last that long. I don't think but it's very, I was an arrogant standpoint to be like, if we're around at the end of time and if we can create a multiverse. Yeah. So I wouldn't lose the thought about that. Okay. And Robert, Debbie has a question about something that we covered last year. So this is fast radio burst. We've called them FRBs. We also like to call them Furbies and so does Debbie. And she says, hi all. Still loving the pod and never missing episodes. Thanks so much for the knowledge you all drop. You're welcome. On to my query. I was learning about FRBs or Furbies as I like to call them. And I suddenly wondered, are Furbies like solar flares on steroids? Since it looks like they're from magnetars, do they build up tension of their magnetic fields till they snap and send Furbies? Like when the magnetic field snaps and sends out solar flares from our sun? Or are they a totally different process? Thanks from Fridged Wisconsin where the air hurts your face. What a selling point to visit. This is definitely a buckle up episode then, Debbie, isn't it? And thanks from Sussex where that question's hurting my head. No, as a reminder, an FRB is a fast radio burst. So a radio signal lasting up to a few seconds. Not really properly understood. And they give out a huge amount of energy in that short time. But despite that, they're so far away, it's a teeny, teeny weak signal. But yeah, one idea is that FRBs or Furbies come from highly magnetized neutron stars. Incredibly dense remnants of massive stars and they're called magnetars. And sometimes their magnetic fields are disrupted and you can get things like starquakes. And or the lines, the magnetic field lines can reconnect, which is so they jiggle around. They're likely to imagine elastic bands snapping and somehow reconnecting. And in each case, these release vast amounts of energy. And the second one of these is a bit like the process that leads still thought to be like the process that leads to a solar flare. So the only difference being it's maybe a trillion times as powerful. So there's something of an energy step change there. Imagine this pretty powerful event on the surface of the sun and making it a trillion times more powerful. So credit to you, Debbie. I mean, this was actually discussed in a release in the Hubble team last year. Remember Hubble? You talked about JWST, remember Hubble? So it's really impressive that you made the comparison if you haven't seen that. So and, you know, I'm sure spring will be in Wisconsin any time soon. Oh, fingers crossed. Oh, yeah, he's hoping. Right, that's it for all of the questions this time. Do keep sending them in along with your pictures and your ponderings. You can email. Can you silly questions? Any silly questions? More potatoes. Yes, exactly. Robert and Becky need a rest. You can email your questions to podcast at rs.ac.uk or find us on Instagram at supermassivepod. And we'll be back in a couple of weeks with a main episode for you all about gravity. But until then, everybody, happy stargazing. Hi, Derek, Tara from Flash Designs here. Hope you well. Not sure if you've seen my emails from last month, but could you please pay my invoice? Thank you so much. Bye. Hi, it's Tara from Flash Designs. Did you get my last voicemail? I know you're busy, but please pay my invoice today, if possible. Hello again. It's Tara again. 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