Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / #432: Virtual Particles & Black Hole Mysteries: Listener Questions Explored

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#432: Virtual Particles & Black Hole Mysteries: Listener Questions Explored · Space Nuts: Astronomy Insights & Cosmic Discoveries

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Hi there, Thanks for joining us. Andrew Dunkley here on a Q and
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a edition of Space Nuts, and coming up on this episode, we're going
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to be talking virtual particles. What spins in a black hole besides my brain?
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And we still want black holes getting a piece of one? Is that
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possible? And what bit could you get? We'll answer all of those questions
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on this edition of Space Nuts fifteen in Channel ten nine ignition Space Nuts or
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three two Space Nuts. When I report it, Bill's good and he doesn't
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know why, but he's back, Professor Fred, what's an astronomer? Hello
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Fred? Hello Andrew, Yes, I've Why am I here? Well that's
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the ultimate question of life, the universe and everything. That's right, Yeah,
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that's right, It's yeah. I had a lovely experience at the weekend
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because I work with a very well known Australian music composer and called Ross Edwards,
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and he wrote her work. Yeah it probably knows music, very very
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well known. He wrote a work probably three four years ago which was supposed
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to be premiered in Tucson, Arizona, a major orchestral and choral work,
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part of which I wrote the words for. And it was a poem that
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I wrote, which basically is all about why are we here? That's why
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I mentioned it but at the weekend. This weekend. It never made it
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to Tucson, Arizona, but it had its premiere performance by a choral group
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called the Song Company in City Recital Hall here in Sydney. So I listened
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to my words being sung by the most amazing choir choral group just blew my
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mind away, and it did make me wonder why I always here? But
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that's what it's about. And I think you sent me a copy of the
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lyrics. There once was a man named Fred who couldn't get out of bed.
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That's the one. Yeah, it's a little bit so slightly more space
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than that, I'm sure it was. Yeah, shall we try to answer
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some questions? No? No, which thanks for joining us school. Yeah,
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let's do it. Next question. It's an all black hole edition as
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well. Yes, yes, very dark indeed, Hi, Fred, and
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Andrew really liked the show. It helps me do the washing up. There's
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a black hole in that. I used to live in Australia and when I
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started listening to Space Nuts, so I thought that Andrew might be the well
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known Sydney Swan's fullback that happens to me semi regularly twenty years after he retired.
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I live on the we're all near Liverpool. I have a question about
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virtual particles. I've found articles on the Internet that give a contradictory view of
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what they are. Some say they are real particles that come from fleetingly in
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and completingly in and out of existence. However, the other explanation suggests that
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they are not real, but a mathematical device to explain how matter and energy
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behave in empty space. I thought that Hawking radiation was caused by one of
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a pair of virtual particles falling through the event horizon of a black hole while
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the other escaped and became real. I'm sure this is a simplistic description of
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what happens, and if virtual particle don't virtual particles don't actually exist, then
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not a very accurate one. It would be great if you could sit me
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straight. Best wish is Martin. Hi Martin, thanks for the question virtual
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particles. There's a lot a lot in that question, Fred, there is,
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and let's start with a good bit because I know the area where Martin
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lives reasonably well, or I did back in the nineteen sixties. Because the
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Wirral, which is a lovely part of the country the UK. A little
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village there called Barnston was where my future in laws lived, except they were
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on the virtual future in laws because that all fell through. But I have
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to visit. I used to visit the will very frequently, so I know
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the area well and can picture it as it was in nineteen sixty seven.
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You are, yeah, so thank you. Thanks for getting in touch from
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the oral Martin. It's nice to have that reminder of a nice place.
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So virtual particles, yeah, and now Martin's absolutely right to be confused about
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this, because everybody is. And a good place to look is the Wikipedia
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page on virtual particles, because when you read through that you realize that it's
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not a case of real and imaginary. It is something a bit more subtle.
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So in fact, I picked out from the introduction. Yes, so
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there's a sentence in This is from the Wikipedia article. The accuracy and use
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of virtual particles in calculations is firmly established, but as they cannot be detected
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in experiments, deciding how to precisely describe them is a topic of debate.
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So there you are. It's a hot topic and I think the bottom line
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is, well, let me read a bit more, because I think this
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perhaps illuminates it. It is a you know, it's a subtle area whether
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these are real particles or not. And they come about because they are a
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particle description of a field, a bit like the Higgs boson is a particle
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that relates to the Higgs field. Let me just read. The concept of
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virtual particles arises in the perturbation theory of quantum field theory, where interactions between
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ordinary particles are described in terms of exchanges of virtual particles. And so basically
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you've got and then it goes on to describe the Feynman diagrams. Fine,
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sorry, Richard Feynmand, that great physicist who did all these sorts of wonderful
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things. And you know, it goes on to say that virtual particles do
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not carry the same mass as a corresponding ordinary particle, although they always conserve
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energy and momentum. And it's a good place to start if you want to
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understand virtual particles, and in fact, just the definition that they give at
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the beginning of this Wikipedia article, a virtual particle is a theoretical transient particle
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that exhibits some of the characteristics of an ordinary particle while having its existence limited
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by the uncertainty principle, which allows the virtual particles to spontaneously emerge from vacuum
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a short time and space ranges. That's it in a nutshell. I don't
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know whether that helps, Martin, but the answer is you're quite right.
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It's a mishmash. Yeah, you mentioned Hawking radiation, which we know of.
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Yes, we do studies the black holes, and talking about a pair
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of virtual particles falling through the event horizon of a black hole. One gets
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captured, the other escapes and becomes real. Is that I think that's as
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good a way as any of looking at it. It's because the Hawking radiation
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has never been detected because it's too weak basically, but simulations, experimental simulations
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have been done and I can't remember the physics of that. But what you're
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doing is you're having proxies for the virtual particles, and it turns out that
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they confirm that Hawking radiation is real, and of course it answers various loose
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ends, but it does mean that eventually black calls evaporate because the particular particles
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that come off Hawking radiation of photons and they basically they are you know that
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that's radiation, so that's why they carry energy away because of this virtual and
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real particle. By the way, virtual photons, according to the Wikipedia article,
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are the exchange particles for the electromagnetic interaction, which makes sense. Electromagnetic
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radiation is carried by photons, So welton, have a look at that Wikipedia
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page. It does go on to get into some pretty deep physics with the
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finemand diagrams, but nevertheless, I think it was quite helpful. It certainly
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helped me to realize that, yes, nobody really knows the answer to this.
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That's the simple answer. No one knows. But thanks Martin for the
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question from the UK to the USA. Gentlemen, this is Michael from Evanston,
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Illinois, having recently read an article on measuring the spin of a black
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hole. Raises a question that I trust you can resolve you a lot of
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faith. I believe the definition of a black hole is a singularity consisting of
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a point of infinite idnsity and infinitely small and an event horizon beyond which nothing
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can escape. That being the case, the question is what exactly is spinning
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or rotating the definitely or the infinitely small and dense point that is difficult for
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me to comprehend, but I admit that my thinking is based on Euclidean geometry.
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Thanks for the great podcast, Michael, Thank you, Michael. Yeah,
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what's spinning in a black hole? For Rick again? Michael, You
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know, this is a very similar question to the other one. It's a
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counterintuitive. If you've got a single point of infinite density, how can it
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half spin? Gives a single point in space can't spin? But it does.
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And the best way to think of it, well, you know,
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going back to our old friend Wikipedia, the definition of a rotating black hole
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is a black hole that possesses angular momentum. So that is the giveaway,
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and if you think about it, you can kind of understand where that comes
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from. I think it's easy to get your head excuse me, easy to
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get your head around this than it is the real and virtual particles. If
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you think about a stellar mass black hole, a black hole which has perhaps
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twenty times the mass of the sun or fifteen times the mass of the sun.
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Let me start again. If you think of a star that is going
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to collapse into a black hole, in other words, one that is perhaps
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ten to twenty times the mass of the Sun at the end of its life.
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So this star explodes as a super and ova its core collapses. But
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the core has itself angular momentum because the star is rotating. So that rotation
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of the star and hence of the core that is now collapsing into a black
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hole. That rotation is still present, has angular momentum. It's a property
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that is conserved. So the collapsing star takes the angular momentum with it when
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it's forming a black hole. So the black hole itself, despite having no
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dimensions, has angular momentum, and that I think is the Yeah, maybe
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like an eddie, that's right, Yes, I mean, you know the
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classic conservation of angular momentum demonstration where you sit on an office chair and you
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spin yourself around with your legs sticking out, and then you pull your legs
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in and that speeds up your rotation. That's the conservation of angular momentum.
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If you then collapse to a black hole, you take the angular momentum with
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you, you'd still be rotating even though you were a black hole. How
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fascinating. So, yeah, Michael, looks like you were well on the
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money, even though your brain is hurting you minus two. He mentioned Euclidean
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geometry. What's that the normal geometry that we experience in everyday life thanks to
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euclid So Euclidean geometry has parallel lines never meeting. It has the angles of
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a triangliding up to one hundred and eighty degrees. Non Euclidean geometry doesn't.
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And we think the universe is non Euclidean, although it does have there's a
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suggestion that perhaps it's almost Euclidean if I put it that way. It's what
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we call it a flat universe. We've talked about this before. Flat is
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the if you've got a flat universe, that's one that has Euclidean geometry throughout,
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and it's probably not flat, but it's not far from flat. We
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know we know from relativity and from the fact that we see gravity warping space
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that the geometry is something we call remannion. It's a Remannian manifold. Is
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the structure of the universe, which is the mathematical term for the geometry that's
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embedded in the universe. Your face has gone blown, Andrew, I'm just
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so glad. I asked the question, Yeah, anyway, you clearing geometries,
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the geometry that we're all familiar with, and to worry about it.
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Geometry wasn't one of my strengths at school, but I probably did better than
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triggeronometry and all those other yeah nometories. I wasn't very good at any of
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them. That's a good one. Yes, yes, I think I just
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made that one up. Thank you, Michael. Great questions. This is
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space and that's Andrew Ankley. Here we professor Fred Watson of Space Nuts.
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Our final question, Fred comes from Josh. Hello, my name is Josh
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Williams, Pennsylvania in the United States. My question is, so, if
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you have one supermousive black hole lying at the rage jectory and it was to
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hit it in a supermousive black hole, would be able to crack off a
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piece of black hole? That's my question. Love your show, it was
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all the time. You got good work, goes. Thanks Thanks Josh.
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That's an interesting question. I mean, you know, we have we know
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of black hole collisions through gravitational waves. We know that when black holes get
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together they get bigger and bigger. But you know, could a piece crack
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off, and you know, could could virtual particles be omitted? Who knows
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could you get a bit, could you get a bit? Yeah? I
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think the bottom line with black holes is they always merge. Yeah, so
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so that you know, two black holes coming together at very high velocity,
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they will basically spin around one another, and that spin will gradually increase in
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speed and they'll get closer and closer until they merge. And that's what we
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make a squeaking sound, that group sound, that's right in the gravitational waves.
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That's what we pick up with gravitational waves of Ligo and other gravitational detectors.
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So yes, so I think bits of broken off black hole are something
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we're never going to find. I think they they only get bigger, they
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don't split into smaller bits. That's just in the nature of their being.
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Their their gravity is so strong that nothing can escape it. So you're never
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going to have a bit that's smashing off because the gravity is so strong within
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the event horizon, nothing even light can escape it. I don't think i'd
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want to get hold of a piece of black if you could not something you
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want to. It's a great way to lose weight, but it's yeah,
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Yeah, the trouble is, you know, you're even with a small modest
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sized black hole, you'd still get spaghettified if you're trying to mess around with
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it. You don't want that. Yeah, No, it's not something I
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guess you can ever handle. And we've never actually we've now got images of
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black holes, a couple of them, and so we know what we're looking
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at. And we weren't surprised by those images when they were released a few
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years ago because mathematically we already knew what they probably looked like. And it
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turned out they looked like orange doughnuts. But they but they But physically speaking,
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yeah, do not touch. I suppose it's the best warning. Do
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not touch within you probably several thousand light years. Yes, yes, exactly
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so Josh. No, you couldn't grab a bit if it if there was
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a collision and a piece broke off, I'm suppose to qualify that pieces don't
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break off, except except when somebody is working at your house and Jordie gets
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interrupted with it's his lot in life to try and break break bits off things,
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especially burns. Johnny goodness, see I love him so great question,
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Josh, But probably not feasible in the scheme of things, and rightly so.
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If you have questions for us. Don't forget to send them in as
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Martin, Michael and Josh didn't. We thank them for that. You can
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go to our website and that is space Nuts dot Io. Click on the
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am a link at the top where you can send audio and text questions,
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like to become a supporter of space Nuts, you can click on the support
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space Nuts button. So good, yeah, good helfor Thank you for it
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has always it's been a great pleasure. It does. It's always good.
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Great to have these questions from our listener's keep them coming. Indeed, all
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right, see you soon, Fred, and you'll catch on the next episode
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coming soon Fred Wat's an astronomer at large. And from oh and thanks to
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Hugh in the studio. What's he doing right now? The usual much And
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from me Andrew Dunkley, thanks for your company. See you on the next
19:56
episode of space Nuts. Allie, Space Nuts, You'll be listening to the
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