#460: Gravity Reimagined, Quantum Field Fables & Black Hole Mysteries

Hi there, thanks for joining us on a Q and A edition of Space Nuts. My name is Andrew Dunkley. Coming up, we will be looking at gravity. Is it working backwards and we don't know it? We'll answer that question, quantum fields, ultra massive black holes, getting up close and personal with telescopes. Is it possible? And a very. Interesting surprise at the end from one of our regular sender in aurs, who's well, I'll preempt it by saying I think it's a joke. You figure it out for yourself. That's all coming up on this episode of Space Nuts. Fifteen seconds in Channel ten nine ignition Figunch Space Nuts or three two. One Space Notes. As an I report it neils good. And it's always good to have the presence of Professor Fred Watson, Astronomer at Large. Hello Fred, Hello Andrew. Yes, it's good to have your presence too, because without that I'd be sunk. Yeah, well, I'd be twiddling my thumbs and you'd be talking to yourself. All yeah. Let's get straight into some questions, and we've got a whole bunch. But and some of this might sound familiar because people keep coming back to topics we've discussed and asking questions about questions that we've answered, and that's fine. I mean, it keeps the conversation going, and obviously, you know, people are very interested in a lot of these topics. This first question comes from Carrick, Hello, Space Nuts, sending this question from Wungari, New Zealand. I hope I pronounced that correctly. I was pondering gravity and dark matter recently and had a thought. We understand gravity as a force that pulls us into objects with mass. However, is it not possible that this attraction force is not there at all and is replaced by a force that is rather pushing us away. Into objects with mass. My thinking behind this started from the fact that our known universe is expanding at an accelerated rate, and the cause behind this unknown energy or force is dark energy. Even as we experience this on Earth, rather than being attracted towards the center of our Earth, are we rather repelled by the forces towards Earth. Thanks for taking the time to read this, Carrick. Thanks Carrick. That turns the whole gravity theory upside down. Fred, Yeah, it's so. I mean, in a way, it's a legitimate way of looking at gravity. It goes to something we were talking about in the last episode. If you look at Einstein's relativity, which is probably the best, well, it is the best theory of gravity we have, uh, and imagine what a massive body does were we can only illustrate it in two dimensions because we haven't got three dimensional cartoons for this sort of thing. But it's always the picture of something solid like a planet sitting on a basically a trampoline sheet which it's bending and pulling down to the middle, so that what you've got is a representative, a representation there of the shape of space, and it's the massive object that is causing the distortion of space, and that puts a slope, puts an incline onto the shape of space. So from our experience here on Earth, if we're standing on the planet's surface, the shape of space is slightly different at our head from what it is at our feet. Could could would. That be demonstrated? And this is just my brain thinking the same way a ship displaces water, is that. The same kind of effect? So well that if you if you've got a ship displacing water, basically put the ship in the water and the water moves away, And so that's a sort of static thing. With gravity, what you've got is a bending of the surface. Now, shipping water doesn't bend. It does for a bit, right, I say, But with with with the space itself, that bending stays, stays there. Space bends in response to matter, no matter what it is. And you could so you know, what Charac says is correct, You could equally well, given that scenario of the planet sitting on a trampoline and distorting the surface, you could equally well think of that as being something that's pushing, that's pushing you from the outside, because it's effectively the same thing that. The bottom line is that space is being distorted by gravity, and we feel that as a pool. But equivalently, we could call it a push from the outside because it has the same effect. So relativity that's sort of in some ways leading to that effect. The bottom line though, and I guess the focus of you know, the thought trail that Carrick was pursuing there is that, yes, we understand all that, and that all works, but dark matter and dark energy are both things on top of that that actually affect They do affect the shape of space in their own different way, but it's not the same as just normal gravity, which is very predictable and very understandable. So I don't think we could use that notion. As any kind of vehic four illuminating what dark master and dark energy are. That's got to come from the work that's already aging. I think so physics, of course. But his idea does hold a little bit of water in terms of the Earth. Is you know, sitting on the trampoline and the trampoline's pushing back. Yes, that's right in a way. That's that's correct. So that you know, anything coming from from the outside edge of the trampoline, you're all a marble down it or something. You could equally well say, well that that it's the outside that's pushing the marble in rather than the gravitational musk that's pulling it in. And it's because relativity tells us that it's the shape of space that has changed. There you go, all right, there you go, Carrick. You you weren't far off the mark. Can't wait to read the scientific paper you're now going to write for us? Yes, okay, we'll move on and hello where everyone in New Zealand, beautiful country? Been there a couple of times? Would go back tomorrow, but not to watch rugby. Now. Next question comes from any in California or any writes to us fairly regularly. How do quantum fields behave Do they interact with each other in any way? Take, for instance, makenetic field with the Higgs field. You might need to elaborate on that a bit for it. Yeah, So quantum fields are the equivalent of sub atomic particles. And this is where you know quantum theory gets a bit weird because you can think of a sub atomic particle in two different ways, in fact three different ways actually, because you can think of it as a particle, you know, something like a golf ball, just to draw an analogue that would be familiar. To you, Andrew. Or you could think of it as a wave because particles and waves are equivalent. Or you can think of it as a field because of the field is equivalent. And by a field, I mean kind of what we're just talking about in terms of gravity. That bent, a distorted trampoline sheet. Is a field. If it's if it's a representation of space, then it's a field. It's a field caused by gravity. So Renny's question is how these fields interact and some of them, certainly do. But a magnetic field probably doesn't interact with a Higgs field. And look, I'm not a quantum field theorist by any means, as anybody who is listening to this. Will immediately realize. But magnetism is well, it's the electromagnetic force, the electromagnetic field, and that electromagnetic field, when you turn it into a particle, it becomes it is a photon. The photon is the is the particle equivalent of the electromagnetic field. And a photon does not have a rest mass. It's got a mass but on it because of its energy as it moves, it doesn't have a rest mass. And the Higgs field is what imparts the rest mass to other particles. So my guess is, and it is just a guess here, Andrew, that the magnetism does not interact with the Higgs field. But I think some of the other particles would, do, you know, the the other fundamental particles would interact with one another because their fields do. Okay, right, thanks for that. Ready, Yeah, look he. Comes up with some real pearls questions questions. Yeah, you must you must have, you know, a very quick mind ready to come up with these questions. He puts a lot of thought into them, and you know, some of them are really clever, really clever. Good to hear from you, Rennie. Keep them coming. I know we've got a couple more in storage that we'll pluck out sooner or later an answer down the track, but yeah, good to hear from you. As always. This is space Nuts Andrew Unkley here. With Professor Fred Watson. Pace puts now. Fred another regular contributor, and we didn't hear from him too long ago, but he always seems to like Rennie, come up with a few curveballs for us. It's Rusty and Donnybrook. Rusty and Donnybrook wondering would an ultra massive black hole near the center of a large void be revealed by its gravitational lensing of more distant of distant galaxies. Kept it short and sweet. Okay, so did you catch that for it? I did, and I've got a short spe answer. Yes, kid will elaborate. Yeah. So, so everything acts as a gravitational lens no matter what it is, including the Earth. There have been ideas proposed of putting a spacecraft that the focus of the gravitational lens represented. By the Earth. I think I can't remember where it is a long way off. Yeah, I can imagine what points. But so so the you know it, any object will will distort things behind the sun. The classic example and the fact that when the eclipse of nineteen nineteen was observed, the stars of the Hyades, which happened to be behind the Sun at that time, were distorted in their positions by the potational effect of the Sun. And so. Gravitational lensing is a property. Of all objects. A human would do it if we're in space, so yeah, a supermassive black hole is going to do it. The issue might well be, though, if the black hole is an active one, that's to say, it's gobbling up stuff around it and radiating, it might be quite difficult to see the stuff behind it because we've got, you know, we'd have an accretion disc which is glowing, and as we know from the event horizon telescope, that will be radiating. And we're be able to see the accretion disc. So yeah, it's. Something that would happen, but might be very difficult to detect. Okay, all right, thank you Rusty as always, and I'm sure he'll send in more questions because he does he just does. But he's another one that probably spends a lot of time contemplating these things. We had Rusty on as a special guest some time ago and we got all these questions out of his system, but then he came back. Come out with plenty more. Next question comes from David. If the James Webb telescope can see so far into the past with such great detail, why can't we have a telescope where we can see every grain of sand on the moon or do we? Thank you? David, I must confess I've wondered the same thing. Good. Well, I'm here to tell you why. I'm guessing there's a reason why not. Yeah, there is, and it's all about so the ability of a telescope to see detail is something we call in the trade. We call it the angular resolution, and it's the angle on the sky that is the finest detail that the telescope can reveal. With the angle. Australian telescope here on in northwestern New South Wales a four meter angle Australian telescope three point nine meters. The one I was stronggering charge off for a while that if you put it in space would resolve detail on the scale of the thirtieth of an arcsecond. Now, an arcsecond is is the angle made by basically a dime or a one dollar coin at a distance of five kilometers about three miles. It's a tiny angle. The at in space could resolve a thirtieth of that, something like a thirtieth of an arcsecond. So the bottom line, however, is that because we're sitting at the bottom of an atmosphere that's quite turbulent, the very best you can do is about ero point nine of an arcsecond on a really exquisite night, and that would be the angle, the minimal I Goode that you would be able to resolve. Now, James Web telescope is a six point five meter tell it's bigger than our angle Australian telescope, which is for me says I just said three point nine meters. And the. Sensitivity to detail depends linearly actually on the diameter of the telescope. So the bigger the telescope, the finer the detail. You can see. So with it James Web telescope, the finest detail it can see is point zero six eight of an arcsecond, a little bit less finer than a tenth of an arcsecond. Is that because? Is that because of its size and the fact that it's not being disrupted by a setmasphy. That's correct, that's right, that's correct. It's sixty eight milliarc seconds, Is that right? Yes? Point zero six eight it's quite a bit less than a tenth actually. Anyway, the bottom line is that's the finest detail that the telescope can resolve. Put it anywhere else, and you know, you can point it anywhere in the universe, this is what I'm trying to say, and you will get that same resolution to detail. Whether it's distant galaxies, whether it's the planets, whether it's exoplanets, you will get the same fineness of detail. So what happens if you point it to the Moon? You get you get a resolution of point zero six eight millie sorry, point zero six eight arcseconds. What does that show you at the distance of the Moon. It will show you details on a scale of one hundred and twenty six meters. That's the finest thing that you could see on the Moon with the web telescope. And it's quite big. It's not grains of sand, it's one hundred and twenty six meters. It's a big object, and that's because the Moon's a long way away, three hundred and eighty four thousand kilometers. So okay, do you think that the day may come with it I'll build a bigger and better telescope that may be capable of much more detail I'm going to envisage. The answer is yes, well. Yes, so that we already We already have that on the stocks the thirty nine point three meter diameter e l T the extremely large telescope being built at Cero Homozonas in Chile. Now that telescope is at the bottom of the atmosphere, so it suffers from that. But it's got a very very sophisticated system of adaptive optics on board that will give it twenty times the detailed sensitivity. Of the Hubble telescope. Wow. Remember the Leubble is not the gems Web but smaller, so it's it's yeah, it's uh, it's a very fine resolution machine. We still will only be seeing detail, you know, on the scale of tens of meters on the Moon. To imagine seeing rains of sad you probably need a telescope bigger than the Earth. That worked out what it is, and it's actually a lot easier just to set the spacecraft with a cabrole. And that's how we've seen images of all the Apollo landing sites because of Fluido Reconnoissance orbiter, which is photographing it from thirty or fifty kilometers above the surface. Yeah. I was sort of HARKing back to the sixties in the early seventies. With the Moon missions. After they were all complete, of course, three gazillion books were released, and I got one that was aimed more at younger people. And even though back then we only had black and white television. Yes, kids, it's true, we only had black and white television and the pictures were quite fuzzy, the book was mind blowingly beautiful. The image images, as I recall from that book, was so high definition compared to what we could see on TV. I was absolutely blown away by it. Yeah. So even then, the cameras that they had on the Moon were quite quite brilliant. But when they go back and start walking around up there again, I can't imagine what the pictures are going to be like with modern day equipment. It's going to be very exciting. And even the pictures coming back from Mars so like death these days. That's right, Yeah, fantastic. I'm just going to revisit something I said Andrew, which was about the Angle Australian telescope being able to resolve for thirtieth of an arc second. That is assuming the mirror is absolutely perfect with no flaws on it. So in reality it will be slightly worse than that in space. And that's why the figure that I mentioned for the James Web telescope on zero six eight is sort of, you know, sounds that it was worse than the. Angle Australian telescope. It's not. It's much better, but that takes into account the imperfections in the mirror as well. Whereas the value that I quoted for the eighties is if the mirror was perfect, if it was an absolutely perfect mirror, the only thing that was limiting its ability to see detail was the theory of diffraction. Okay, Yeah, And just. In case anybody who was listening carefully and said, wait a minute, he just said something else. I can't imagine what the badget is at a telescope like the Anglo Australian for windex. I mean that must cost a fortune. You know. The End Australian telescope. Mirror is cleaned once a year when the aluminium surface is removed and and it's requoated, right, so it's never cleaned with chemicals. Some observatories avoid doing that by using carbon dioxide snow home solid carbon dioxide across the mirror and that takes away some of the dust. We don't do that in the Angle Australian. We take the surface away and recoat it. But just down the road from the Angle Australian Telescope is the United Kingdom Schmidt telescope, which I was also a strollery and Childe off yep. That was at one point two meter diame. It a lens at the front, not a mirror. It does have a mirror in it, but the main thing that gets dirty is a lens. And guess what we used to clean it with wind as. So you ask a dumb question, you get a great answer. Sometimes sometimes it works. I was joking anyway, that's good, that's good to know. Yeah, well, so no, it can't work, David. It's just a bit beyond our capability and spread. Yeah yeah. And you know, if you wanted to build one capable of that, you might as well build a whole planet, although that work, that works for Darth Vader. But yeah, all right, thanks David, thanks for the question. One final thing, it's not a question. It's one of our regular sender ins who shall remain. Nameless because he'll tell us who he is. Anyway, This is kind of well, he's going to eventually tell a joke, but you're gonna have to because he bleeps part of it out. You're going to have to use your brain to figure out the punchline. Some people may already have heard this one. I love it is Martin. Hello, Space Nights. Martin Berman Borvain here from Potomac, Maryland, US, a writer extraordinaire in many genres, especially science fiction, and I am currently working on a novel about an obnoxious billionaire called Egon Risk and his plans to take a starship full of dim witted celebrities to found a new master race among the stars, and how these plans may or may not come to grief. I don't actually have a question this week. I actually just have a little known bit of Star Wars trivia. Did you know that George Lucas was originally planning to have Skywalker's home planet Tattooing be a satellite of the seventh planet of our solar system. Yes, but he had to move the planet Tattooing to a long long time ago in a galaxy far far away because someone pointed out to him that his original plan would have resulted in a double planet called Tattooing. Your plea, Okay, that's all the time we have for dad jokes today, Bermin goorvain over and out out. Oh Martin, Oh Martin, Martin, Matt, I love that joke, though, I really do very clever. Again a play on words, A play on words. It has done the rounds a bit, but it's always worth retelling. God on you, Martin. If you've got a question for us, please jump on our website and send it in. You can do that by going to space Nuts podcast dot com and then all you need to do is click on the AMA tab at the top and it's a simple case of just sending us a text question, or if you've got a device with a microphone, you can send it an audio question. As always, don't forget to tell us who you are and where you're from, and we'd love to hear from you, no matter how big, small, or insignificant the question, we'll give it a crack and sometimes we get very similar questions. So if we don't answer yours, chances are it's because someone else asks something the same. And while you're there, just have a look around. And if you're on social media, don't forget to like us or follow us or subscribe, depending on which platform it is. We're all done, Fred, thank you as always. Thank you Andrew. Good to talk to you, and we'll catch up again soon. I think we will. Yes, Indeed, Professor Fred Watson, astronomer at large and here in the studio who didn't ask us any questions today. Very disappointing, but I'm sure that'll fix itself down the track. From me Andrew Dunkley, thanks for your company. We'll catch you again real soon on another episode of Space Nuts. Bye bye spaces. You'll be listening to the Space Nuts podcast. 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