Supermassive Black Holes, Voyager’s Journey & Gravitational Waves Explained | Q&A | Space Nuts:...

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Kind: captions
Language: en

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Hello again. Thanks for joining us on


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Space Nuts, where we talk astronomy and


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space and science all at the same time.


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Uh, this is a Q&A episode. My name is


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Andrew Dunley, your host. Great to have


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your company. Coming up, audience


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questions. We're going to answer a


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question from Martin about super massive


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black holes. Uh, Ben has also got a


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question about black holes and


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gravitational waves. Andy, our favorite


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train driver is on about Voyager 1. And


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Jud has some thought experiments for us.


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We'll check it all out on this episode


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of Space Nuts.


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>> 15 seconds. Guidance is internal. 10 9


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Ignition sequence start.


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>> Space nuts.


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>> 5 4 3 2


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>> 1 2 3 4 5 5 4 3 2 1


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>> Space Nuts.


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>> Astronauts report. It feels good.


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And back to unravel, unpack, and solve


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all of that is Professor Fred Watson,


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astronomer at large. Hello, Fred.


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>> Hello, Andrew. Very good to see you.


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>> Good to see you, too. I've still got


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McCroy voice. Um, in fact, I've been so


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unwell, I'm still wearing the same


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clothes as I was last week.


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>> Well, there you go.


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>> Funnily enough, so am I.


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>> Yeah. Well, what a coincidence.


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>> Uh, shall we get down to business?


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Why not?


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>> All right. Something else to do. So,


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yeah.


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>> Now, we've got some text and audio


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questions. We'll go text first today.


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Uh, and forgive my rather um unreliable


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voice as I work my way through this. Hi,


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Fred and Andrew. It's Martin here from


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Hezwall on the Whirl in Murzy side. I


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posted a question before and Fred


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mentioned that he knew Barnston, which


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is just a pleasant walk over the fields


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from here. I have a question about your


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favorite topic, black hole. I thought it


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was going to be golf. Black holes. Uh


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I'm interested specifically in the


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process of their formation and more


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particularly in super massive black


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holes. The mechanism for the creation of


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stellar mass black holes seems to be


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well understood. But I find it hard to


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believe that this can be the same way


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that super massive black holes in the


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early universe were formed. I've read


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that the gravitational instability


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theory posits that black holes can be


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formed directly when a massive cloud of


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matter collapses under its own gravity.


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Why is it not possible that there can be


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two processes at work depending on the


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size? For me, part of the evidence in


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supporting uh in support of invoking


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gravitational instability is the lack of


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evidence for the existence of


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intermediate mass black holes. What are


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the arguments against this theory? As it


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does seem to be that widely, it doesn't


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seem to be that widely accepted. If


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black holes are created in two


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completely different ways, what effect


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would this have on their properties? For


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instance, charge, spin, etc. I really


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enjoy listening to the show. It helps me


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keep up to date with the world of


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science, space, and stuff. That's our


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slogan. Ha. Well done. Well done,


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Martin. That's our slogan. Um, yeah.


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Look, that's a really good question and


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we only talked in the last episode about


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the the the different theories about uh


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how black holes are formed and the


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possible discovery of primordial black


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holes. So uh if you haven't heard that


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episode, wind back because it's worth


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listening to that story. But uh yeah, he


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brings up an interesting point. Uh how


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can it be the same process for a super


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massive black hole versus a um you know


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another one, a smaller one?


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>> Yeah. So I I mean Martin's um hit on one


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of the key questions at the moment in in


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astrophysics and cosmology. So he's


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right up to date there.


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>> Yeah, he sure is. Um because um this


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idea of uh the super massive black holes


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in the early universe forming directly


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as a as a direct result of a cloud of


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gas collapsing without having to go


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through the mechanisms or of of a


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forming a star and then the stars


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basically exploding uh to form a a black


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hole. That's quite new.


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uh and that might be why as Martin says


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it's not yet sort of considered to be


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mainstream but it is it is very much an


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upand cominging idea and theory that


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answers the criticism that the


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conventional theory has uh and that is


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conventionally uh scientists have


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assumed that super massive black holes


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are created over long periods of time by


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the accretion of material. So um we know


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how a stellar mass black hole is formed


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exactly as Martin mentioned we


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understand that's massive star explodes


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at the end of its life when the fuel


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balance runs out. uh the outer layers


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are shed off and a supernova remnant and


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the center basically the central core


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collapses to be the black hole which is


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a point with zero dimensions a point


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where uh density is infinite. Uh so that


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the conventional method says you start


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off with lots of those in a galaxy and


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they eventually uh accrete to form a


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bigger object uh mixing with stuff


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that's sucked in on the accretion disc


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as well. That might include a few odd


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black holes dropping in. Yeah.


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>> To form eventually a super massive black


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hole. But the problem has been how do


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you manage to do that in less than a


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couple of hundred million years which is


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you know where the earliest super


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massive black holes are after the big


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bang we know about those because we can


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we measure them by looking using the


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James web space telescope it's measured


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I think several objects within maybe 250


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million uh years after the big bang in


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other words we're looking back almost


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13.8 billion years, 13.6 or something


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like that. Um, uh, how did they form so


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quickly if that's the mechanism? And


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that's why this alternative mechanism of


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of direct collapse from a an


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interstellar


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>> from from a not interstellar because


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there were no stars then, but from a


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primordial gas cloud might have


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occurred. And in as I understand it,


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the idea of primordial


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uh black holes postulated, this is what


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we talked about last week uh or the last


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episode postulated by Steven Hawking uh


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envisaged that there would be a very


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very wide range of masses of black holes


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ranging from things less than the mass


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of the sun. um as we reported in the


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last episode, we think we found one of


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those now. Yeah.


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>> Uh to super massive black holes. I think


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that is all within the purview of


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Hawking's theory of primordial black


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holes. And so the question, you know,


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maybe the fact that we're finding these


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super massive black holes


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too early in the universe um might to to


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have been formed by stuff coming


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together. uh might be a support for the


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Hawings theory that maybe some of these


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were actually formed immediately after


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the big bang.


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>> Wow. Wouldn't that be interesting?


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>> Um


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>> there was something about um something


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that um Martin mentioned about


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intermediate.


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>> Yeah. He said for me part of the


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evidence in support of invoking


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gravitational instability is the lack of


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evidence for the existence of


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intermediate mass black holes. Although


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they're the ones we were talking about


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recently that we now have discovered,


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have we not?


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>> Yes. Um but they're still and they still


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seem to be Yes. much rarer than the


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super massive black holes or the stellar


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mass black holes which are which exist


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in profusion. Uh intermediate mass black


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holes have been quite hard to find. Uh


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>> maybe they're just beaten up.


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>> Yeah, I mean you know what Martin says


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is right. um that might point to uh to


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the the idea of gravitational


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instability, in other words, sort of


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primordial type black holes as being the


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formation. Uh that might point to that.


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Um and so I don't think there's an issue


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there. Uh but yes, his final question,


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uh if black holes are created in two


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completely different ways, what effect


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would that have on their properties? For


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example, charge, spin, etc.


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>> Now, in fact, the only properties of a


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black hole that you can observe um are


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the charge and the spin as well as the


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mass. Um and that um that's because of


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something that you and I might have


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mentioned before, Andrew, something


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called the no hair theorem, uh which I'm


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very fond of, uh as you can guess. And


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the no hair theorem basically says that


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there's


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you know there's virtually nothing um of


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the black holes characteristics that you


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can see from the outside. It's like


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suggesting a baldness of the of the


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black hole the event horizon. It doesn't


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give much away. Charge and spin are I


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think I think only the only two apart


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from mass. Now I don't know the answer


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to that. Would there be any difference


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in those properties uh for two different


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methods of black hole formation? And


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it's a really good question. Uh and um


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it's something that I probably should


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have a look at and see if I can find


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out.


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>> Yeah, I I thought I'd look up no hair


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theorem to see what happened. And um I I


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didn't get um an ad for a for a hair


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pill. It actually took me it actually


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took me to the


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>> to the to the no hair theorem


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>> to the no hair theorem about black


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holes. Yeah. So there you go.


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The internet actually worked.


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>> Yes,


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>> nice change. Nice change. And a nice


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question. Uh Martin, thanks for sending


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that to us. Hopefully that helped you


00:10:08.880 --> 00:10:11.430
sort a few things out, but uh yeah, it's


00:10:11.440 --> 00:10:13.030
there's still a lot of theory around


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black holes yet to be proven, but we're


00:10:15.519 --> 00:10:17.509
chipping away at it. We are chipping


00:10:17.519 --> 00:10:19.829
away at it. Not me personally. I leave


00:10:19.839 --> 00:10:21.190
that to other people who are more


00:10:21.200 --> 00:10:24.069
astute. Uh thanks for sending it in. Our


00:10:24.079 --> 00:10:26.470
next question comes from our favorite


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train driver. His name is Andy.


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>> Train driver here. Uh just a question


00:10:31.920 --> 00:10:35.110
for you on Voyager One. Um I know that


00:10:35.120 --> 00:10:36.949
he's currently traveling about 38,000


00:10:36.959 --> 00:10:40.230
mph and it's very low on fuel and the


00:10:40.240 --> 00:10:42.389
fuel is used for the thrusters to point


00:10:42.399 --> 00:10:45.670
it antennas back to Earth. Um and I know


00:10:45.680 --> 00:10:47.430
that space is not empty. There's


00:10:47.440 --> 00:10:50.790
particles and space dust. So, because


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he's got such a long journey before he


00:10:52.320 --> 00:10:54.790
reaches anything significant, would the


00:10:54.800 --> 00:10:57.030
particles in space


00:10:57.040 --> 00:11:00.550
slow it enough to bring it to a halt?


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Cuz as far as I'm aware, it's got about


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40,000 years before it reaches something


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significant. So, is that a long enough


00:11:07.120 --> 00:11:10.470
time, would you say, to maybe not bring


00:11:10.480 --> 00:11:12.790
it to a halt, but to to slow it


00:11:12.800 --> 00:11:14.870
significantly that it really does


00:11:14.880 --> 00:11:17.750
increase that time scale?


00:11:17.760 --> 00:11:19.269
Uh, sorry if that doesn't make much


00:11:19.279 --> 00:11:21.670
sense. Uh, thanks for your podcast,


00:11:21.680 --> 00:11:23.110
guys. Really enjoy it. Speak to you


00:11:23.120 --> 00:11:24.150
soon. Bye.


00:11:24.160 --> 00:11:26.389
>> Thank you, Andy. Hope all is well on


00:11:26.399 --> 00:11:29.509
your daily commute, although you're the


00:11:29.519 --> 00:11:31.110
driver, so you just drag everyone else


00:11:31.120 --> 00:11:35.030
around. But what a great job. Um, right.


00:11:35.040 --> 00:11:38.630
Okay. Voyager 1, 38,000 mph. Uh, is


00:11:38.640 --> 00:11:40.630
there enough material to ultimately stop


00:11:40.640 --> 00:11:42.069
it? Cuz it's going to run into a few


00:11:42.079 --> 00:11:44.230
things here and there, possibly. But I


00:11:44.240 --> 00:11:46.710
would question the spread of the dust


00:11:46.720 --> 00:11:48.470
when you get out into those uh


00:11:48.480 --> 00:11:51.829
interstellar places. The amount of


00:11:51.839 --> 00:11:53.990
material thins out significantly,


00:11:54.000 --> 00:11:55.269
doesn't it?


00:11:55.279 --> 00:11:58.389
>> Yeah, very much so. Um there is still


00:11:58.399 --> 00:12:01.110
you know there are still atoms there um


00:12:01.120 --> 00:12:04.870
or nuclei probably subatomic particles


00:12:04.880 --> 00:12:10.790
um but it's not uh it's not enough to


00:12:10.800 --> 00:12:14.230
significantly slow the spacecraft.


00:12:14.240 --> 00:12:16.069
>> Uh


00:12:16.079 --> 00:12:18.870
it's you know you you basically to all


00:12:18.880 --> 00:12:20.629
intents and purposes it's moving through


00:12:20.639 --> 00:12:24.230
a vacuum. Um it's I was thinking


00:12:24.240 --> 00:12:26.069
kilometers/s.


00:12:26.079 --> 00:12:30.310
Current speed is uh 16.920


00:12:30.320 --> 00:12:33.590
kilometers/s relative to the sun.


00:12:33.600 --> 00:12:36.870
>> 61,000 kilometers an hour. 17 km a


00:12:36.880 --> 00:12:39.990
secondish. Uh 38,000 mph. Yep. It's


00:12:40.000 --> 00:12:41.590
going. It's fast.


00:12:41.600 --> 00:12:43.990
>> It is. Uh the the speed I like is in


00:12:44.000 --> 00:12:47.269
units of astronomical units per year. Uh


00:12:47.279 --> 00:12:51.110
and that is 3 3.6


00:12:51.120 --> 00:12:55.750
nearly 3.569. So, uh, three times a year


00:12:55.760 --> 00:12:58.470
it covers the distance from the Earth to


00:12:58.480 --> 00:13:00.629
the Sun here. So,


00:13:00.639 --> 00:13:03.190
>> yeah, that's 150 million kilometers.


00:13:03.200 --> 00:13:04.949
>> Sure is. That's that's amazing, isn't


00:13:04.959 --> 00:13:08.069
it? And it's still going strong.


00:13:08.079 --> 00:13:10.470
>> Yeah. So, and andy's right. I think the


00:13:10.480 --> 00:13:13.590
fuel's low, but the fuel is uh just for


00:13:13.600 --> 00:13:16.230
the thrusters. It's just to keep the


00:13:16.240 --> 00:13:19.590
antenna pointed towards Earth.


00:13:19.600 --> 00:13:22.949
>> So, yeah. and and he said it might come


00:13:22.959 --> 00:13:25.670
across something in about 40 40,000


00:13:25.680 --> 00:13:27.670
years. I I thought when we talked about


00:13:27.680 --> 00:13:30.069
this last that it it could just keep


00:13:30.079 --> 00:13:33.030
going. It might not run into anything.


00:13:33.040 --> 00:13:35.030
Yeah. Simply because it's not aimed at


00:13:35.040 --> 00:13:37.910
anything and space is very empty. Uh


00:13:37.920 --> 00:13:39.670
even though there's a you know 400


00:13:39.680 --> 00:13:41.350
billion stars in the Milky Way or


00:13:41.360 --> 00:13:43.750
whatever, the Milky Way is very very big


00:13:43.760 --> 00:13:49.110
indeed. Uh and um it's look it's uh its


00:13:49.120 --> 00:13:52.230
distance is I think I think the odds are


00:13:52.240 --> 00:13:54.310
that it will keep going forever. It


00:13:54.320 --> 00:13:55.910
might be captured by the gravity of


00:13:55.920 --> 00:13:59.590
another star. I think the um the notion


00:13:59.600 --> 00:14:02.629
of a collision is vanishingly small.


00:14:02.639 --> 00:14:05.829
>> Um I've just um


00:14:05.839 --> 00:14:07.590
statistics just come into my head that I


00:14:07.600 --> 00:14:10.710
used to use a lot uh to to give people


00:14:10.720 --> 00:14:13.670
the idea of just how big the galaxy is.


00:14:13.680 --> 00:14:15.670
uh and I'm sure you and I have discussed


00:14:15.680 --> 00:14:18.550
it too. If you imagine a diagram of our


00:14:18.560 --> 00:14:22.470
galaxy uh that was the size of the earth


00:14:22.480 --> 00:14:25.670
so 12 and a half thousand kilometers in


00:14:25.680 --> 00:14:28.710
diameter that's your map of the galaxy


00:14:28.720 --> 00:14:32.150
uh the size of the earth. The separation


00:14:32.160 --> 00:14:35.750
from the sun to the earth on that scale


00:14:35.760 --> 00:14:40.230
is 2 mm. That tells you that the galaxy


00:14:40.240 --> 00:14:42.949
is very very large compared with the


00:14:42.959 --> 00:14:45.990
size of the solar system.


00:14:46.000 --> 00:14:48.790
That's just mind-boggling stuff really


00:14:48.800 --> 00:14:50.069
easily.


00:14:50.079 --> 00:14:52.389
>> And the other thing I suppose like we


00:14:52.399 --> 00:14:55.030
talk about the or cloud which is this


00:14:55.040 --> 00:14:58.310
thing around our um is it around our


00:14:58.320 --> 00:14:59.990
solar system or around a galaxy? I can't


00:15:00.000 --> 00:15:00.550
remember.


00:15:00.560 --> 00:15:01.750
>> No, it's around the solar system.


00:15:01.760 --> 00:15:03.030
>> Solar system. Yeah.


00:15:03.040 --> 00:15:05.350
>> Yeah. Um, they reckon it's going to take


00:15:05.360 --> 00:15:07.910
300 years for Voyager One to reach that.


00:15:07.920 --> 00:15:11.430
>> That That's right. Um, that's right.


00:15:11.440 --> 00:15:12.389
>> That and


00:15:12.399 --> 00:15:13.269
>> still a long way off,


00:15:13.279 --> 00:15:14.710
>> which means it still hasn't really left


00:15:14.720 --> 00:15:17.030
our solar system in real terms.


00:15:17.040 --> 00:15:19.430
>> I'm not even sure that it will be 300


00:15:19.440 --> 00:15:22.310
years because the cloud is about a light


00:15:22.320 --> 00:15:24.150
year away.


00:15:24.160 --> 00:15:27.430
>> Well, actually, it says here um the


00:15:27.440 --> 00:15:29.430
inner edge in 300 years, but it will


00:15:29.440 --> 00:15:31.910
take 30,000 years to pass through it.


00:15:31.920 --> 00:15:33.590
>> That's more like it. Yeah. Yeah. It's


00:15:33.600 --> 00:15:33.990
more like


00:15:34.000 --> 00:15:35.269
>> So, I should have finished reading the


00:15:35.279 --> 00:15:39.350
sentence, shouldn't I?


00:15:39.360 --> 00:15:40.949
>> There was there was an unpredictable


00:15:40.959 --> 00:15:42.710
full stop in there, though. So,


00:15:42.720 --> 00:15:43.269
>> yeah.


00:15:43.279 --> 00:15:44.069
>> But, um,


00:15:44.079 --> 00:15:44.710
>> yeah,


00:15:44.720 --> 00:15:46.949
>> incredible.


00:15:46.959 --> 00:15:48.790
>> Sorry, I meant to say, um, last time


00:15:48.800 --> 00:15:50.470
Andy came on, I meant to tell him that


00:15:50.480 --> 00:15:53.509
I'm a train driver, too. Uh, but it's


00:15:53.519 --> 00:15:56.389
ends scale. Uh, which he'll know. He'll


00:15:56.399 --> 00:15:58.949
know what that is. Not some people might


00:15:58.959 --> 00:16:00.230
not know. Actually, probably quite a lot


00:16:00.240 --> 00:16:02.790
of our listeners do. But I drive my


00:16:02.800 --> 00:16:04.790
trains in Nscale. I love it.


00:16:04.800 --> 00:16:07.189
>> I should send Andy, if if he sends me


00:16:07.199 --> 00:16:09.829
his email address, um some video of our


00:16:09.839 --> 00:16:11.829
brand new regional trains in New South


00:16:11.839 --> 00:16:12.949
Wales that are being


00:16:12.959 --> 00:16:13.749
>> I'd like to see that.


00:16:13.759 --> 00:16:15.749
>> Yeah. They're being fitted out in um in


00:16:15.759 --> 00:16:18.389
do where I live and they've been doing


00:16:18.399 --> 00:16:19.990
test runs on them. I've actually heard


00:16:20.000 --> 00:16:21.030
it


00:16:21.040 --> 00:16:23.350
>> uh in the we small hours passing by


00:16:23.360 --> 00:16:24.949
because it it's got a completely


00:16:24.959 --> 00:16:26.069
different sound. And I've actually


00:16:26.079 --> 00:16:27.749
reached a point now where I recognize


00:16:27.759 --> 00:16:31.030
the different trains by sound.


00:16:31.040 --> 00:16:35.590
How pathetic is that? But um


00:16:35.600 --> 00:16:38.230
>> much much quieter than the current train


00:16:38.240 --> 00:16:41.110
which is the XPT uh which is well past


00:16:41.120 --> 00:16:43.990
its use by date but never let the New


00:16:44.000 --> 00:16:46.870
South Wales government, you know, build


00:16:46.880 --> 00:16:48.790
a train because they will they will say,


00:16:48.800 --> 00:16:50.310
"Okay, it's got a 20-y year life, so


00:16:50.320 --> 00:16:52.790
we'll replace it in 50." Cuz that's


00:16:52.800 --> 00:16:57.030
what's happening. Um but uh these are


00:16:57.040 --> 00:16:58.949
very slick. These are Spanish trains


00:16:58.959 --> 00:17:01.829
that are being fitted out in do and um


00:17:01.839 --> 00:17:04.470
really really lovely piece of kit as


00:17:04.480 --> 00:17:07.110
Fred would say. So um Andy sent me your


00:17:07.120 --> 00:17:09.189
email address and I will send you a


00:17:09.199 --> 00:17:12.150
video of of our um our new trains that


00:17:12.160 --> 00:17:13.829
it's weird watching them run around with


00:17:13.839 --> 00:17:17.189
nobody in them. It's just no passengers,


00:17:17.199 --> 00:17:19.510
nothing. Just all the lights are on.


00:17:19.520 --> 00:17:22.309
Nobody's home. Nobody's home.


00:17:22.319 --> 00:17:24.069
>> Yeah. If you're on the metro in Sydney,


00:17:24.079 --> 00:17:25.510
there's not even a driver on board


00:17:25.520 --> 00:17:27.990
either. Yeah, I know. I've been on the


00:17:28.000 --> 00:17:29.750
metro a couple of times. It's a slick


00:17:29.760 --> 00:17:30.549
system.


00:17:30.559 --> 00:17:31.350
>> Oh, it's brilliant.


00:17:31.360 --> 00:17:33.110
>> One of my boys lives in a suburb where


00:17:33.120 --> 00:17:35.190
they're just about to complete a metro


00:17:35.200 --> 00:17:37.190
line. So, he's really happy about that


00:17:37.200 --> 00:17:39.110
cuz it'll get him to work, you know,


00:17:39.120 --> 00:17:40.950
three times as fast.


00:17:40.960 --> 00:17:43.270
>> So, he's really he's thrilled cuz he got


00:17:43.280 --> 00:17:45.110
rid of his car. He doesn't use a car in


00:17:45.120 --> 00:17:48.070
Sydney. Doesn't see the need. Got to


00:17:48.080 --> 00:17:50.310
have one out here though in the country.


00:17:50.320 --> 00:17:51.990
Uh, thanks Andy. Lovely to hear from


00:17:52.000 --> 00:17:53.750
you. This is Space Nuts with Andrew


00:17:53.760 --> 00:17:58.630
Dunley and Professor Fred Watson.


00:17:58.640 --> 00:18:01.110
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00:19:31.120 --> 00:19:32.950
>> Roger, you're here also.


00:19:32.960 --> 00:19:34.470
>> Space nuts.


00:19:34.480 --> 00:19:39.029
>> Oh boy. Um, okay. Next question. Uh, I


00:19:39.039 --> 00:19:40.470
don't even know where we're up to. Where


00:19:40.480 --> 00:19:42.070
are we up to? We've spoken to Andy. All


00:19:42.080 --> 00:19:44.310
right. Um, question three. Hi, Space


00:19:44.320 --> 00:19:45.990
Nuts. Ben Harding here from Kent,


00:19:46.000 --> 00:19:47.990
England. Uh, having listened to your


00:19:48.000 --> 00:19:51.029
show for several years now, uh, I know


00:19:51.039 --> 00:19:52.710
everything there is to know about black


00:19:52.720 --> 00:19:54.789
holes. Indeed, I'm ready to start


00:19:54.799 --> 00:19:57.430
building my own any day now. But wait,


00:19:57.440 --> 00:19:59.990
if I build two and they crash together,


00:20:00.000 --> 00:20:02.310
they will create gravitational waves and


00:20:02.320 --> 00:20:04.070
I need to account for the ensuing


00:20:04.080 --> 00:20:06.630
distortion of the fabric of spaceime or


00:20:06.640 --> 00:20:09.350
my cats will be upset.


00:20:09.360 --> 00:20:13.270
So are gravitational waves spherical or


00:20:13.280 --> 00:20:15.510
flat? I'm thinking they must be


00:20:15.520 --> 00:20:18.150
spherical. But then again, if they are


00:20:18.160 --> 00:20:20.710
created by two objects spiraling in


00:20:20.720 --> 00:20:23.909
together, the waves may be flat uh by


00:20:23.919 --> 00:20:26.789
some sort of uh conservation of angular


00:20:26.799 --> 00:20:29.669
momentum rule. Uh I hope you can help me


00:20:29.679 --> 00:20:32.390
with my cats. Um they get a bit scratchy


00:20:32.400 --> 00:20:34.310
when they're upset.


00:20:34.320 --> 00:20:37.430
Thanks for the awesome show, Ben. H


00:20:37.440 --> 00:20:39.830
Thank you, Ben. Um I'm just imagining


00:20:39.840 --> 00:20:43.029
your cats. Uh freaking out over


00:20:43.039 --> 00:20:44.870
gravitational waves. There's a comic


00:20:44.880 --> 00:20:48.630
strip in that I reckon somewhere. My my


00:20:48.640 --> 00:20:50.549
brother would do a a comic on that. I


00:20:50.559 --> 00:20:54.310
reckon he's very artistic as my brother.


00:20:54.320 --> 00:20:56.789
>> Okay. All right. So, gravitational waves


00:20:56.799 --> 00:21:00.070
from the um cataclysmic collision of uh


00:21:00.080 --> 00:21:03.590
two black holes spherical.


00:21:03.600 --> 00:21:08.950
Um, so I think what uh Ben is


00:21:08.960 --> 00:21:11.590
referring to um in his description is


00:21:11.600 --> 00:21:14.230
whether they whether they're they're


00:21:14.240 --> 00:21:16.630
radiated gravitational waves are


00:21:16.640 --> 00:21:18.789
radiated in all directions. Yeah.


00:21:18.799 --> 00:21:21.990
>> What we would call isotropic or just in


00:21:22.000 --> 00:21:24.950
a plane in the plane of the collision.


00:21:24.960 --> 00:21:27.830
>> And um to the best of my understanding


00:21:27.840 --> 00:21:29.350
the answer is that they're isotropic.


00:21:29.360 --> 00:21:30.950
They go off in all directions.


00:21:30.960 --> 00:21:34.789
>> Right? So space shutters uh just because


00:21:34.799 --> 00:21:37.590
of the the gravitational interaction.


00:21:37.600 --> 00:21:40.870
It's not got any pref I don't think I do


00:21:40.880 --> 00:21:42.390
not believe it's got any preferred


00:21:42.400 --> 00:21:45.029
direction because of the you know the


00:21:45.039 --> 00:21:46.950
direction of the collision. I think it's


00:21:46.960 --> 00:21:50.310
um it is the same in all directions. Um


00:21:50.320 --> 00:21:52.549
there's another way of interpreting


00:21:52.559 --> 00:21:56.310
Ben's question though and that is uh how


00:21:56.320 --> 00:21:59.270
the oscillations of gravitational waves


00:21:59.280 --> 00:22:02.310
take place. Um, and they're not they're


00:22:02.320 --> 00:22:05.270
not the same as sound waves where which


00:22:05.280 --> 00:22:07.590
are compression waves where things push


00:22:07.600 --> 00:22:09.830
backwards and forwards. And they're not


00:22:09.840 --> 00:22:12.070
the same as light waves which are


00:22:12.080 --> 00:22:14.230
transverse waves where the electric


00:22:14.240 --> 00:22:17.830
field and magnetic field vary in a in a


00:22:17.840 --> 00:22:19.669
transverse manner. In other words,


00:22:19.679 --> 00:22:21.590
opposite to the direction of propagation


00:22:21.600 --> 00:22:23.590
or right angles to the direction of


00:22:23.600 --> 00:22:25.110
propagation. There's something called


00:22:25.120 --> 00:22:27.990
quadruple waves which is a sort of


00:22:28.000 --> 00:22:30.549
combination of not quite a combination


00:22:30.559 --> 00:22:33.350
of the two but certainly um a slightly


00:22:33.360 --> 00:22:36.310
unusual form of of transverse wave


00:22:36.320 --> 00:22:38.630
quadrupole waves is what they are. Um


00:22:38.640 --> 00:22:40.070
but I don't think that's what he means.


00:22:40.080 --> 00:22:42.230
I think what Ben means is what I


00:22:42.240 --> 00:22:44.390
answered in the first place that uh yes


00:22:44.400 --> 00:22:46.870
they're isotropic rather than limited to


00:22:46.880 --> 00:22:48.870
a particular plane. So, they go out in


00:22:48.880 --> 00:22:50.710
all directions, unlike the gravitational


00:22:50.720 --> 00:22:53.830
wave that um I detected on a plane.


00:22:53.840 --> 00:22:55.270
>> Uh I don't know what that guy was


00:22:55.280 --> 00:22:57.510
eating, but um yeah, I hope I don't have


00:22:57.520 --> 00:23:00.470
to experience that again.


00:23:00.480 --> 00:23:02.950
>> Yeah, I know about those things as well.


00:23:02.960 --> 00:23:04.630
>> Pretty awful stuff. Really?


00:23:04.640 --> 00:23:05.510
>> Yep, they are.


00:23:05.520 --> 00:23:08.230
>> I'm impressed that Ben says he knows


00:23:08.240 --> 00:23:09.909
everything there is to know about black


00:23:09.919 --> 00:23:11.510
holes. Does that mean we've been doing


00:23:11.520 --> 00:23:14.870
our job?


00:23:14.880 --> 00:23:16.549
It means he he knows more than us, which


00:23:16.559 --> 00:23:18.230
is pretty easy to do. Really


00:23:18.240 --> 00:23:19.430
>> possible, too. Yeah.


00:23:19.440 --> 00:23:20.070
>> Yes.


00:23:20.080 --> 00:23:21.270
>> But but we're learning more and more


00:23:21.280 --> 00:23:22.470
about them. Um


00:23:22.480 --> 00:23:24.070
>> we are. That's cuz we listen to our


00:23:24.080 --> 00:23:24.710
listeners.


00:23:24.720 --> 00:23:28.230
>> That's that's exactly right. But uh


00:23:28.240 --> 00:23:30.149
yeah, they've been the topic of I I


00:23:30.159 --> 00:23:32.310
think since we started a decade ago,


00:23:32.320 --> 00:23:35.430
Fred, I um you reminded me earlier, uh


00:23:35.440 --> 00:23:37.350
it's been 10 years we've been doing this


00:23:37.360 --> 00:23:39.750
podcast. That's that's extraordinary. We


00:23:39.760 --> 00:23:41.510
should have had a party, but I think we


00:23:41.520 --> 00:23:43.830
just can't stay up that late anymore.


00:23:43.840 --> 00:23:47.750
But um it it's um it's probably been the


00:23:47.760 --> 00:23:50.549
hottest topic on Space Nuts since day


00:23:50.559 --> 00:23:52.549
one is black holes.


00:23:52.559 --> 00:23:54.789
>> Uh closely followed by dark matter, dark


00:23:54.799 --> 00:23:57.270
energy and um I yeah, I don't know where


00:23:57.280 --> 00:23:59.029
you go from there, but uh it's been of


00:23:59.039 --> 00:23:59.830
>> life in space.


00:23:59.840 --> 00:24:02.710
>> Yes, life. Yes, you are right. That's


00:24:02.720 --> 00:24:04.390
those are the top four topics. So, I


00:24:04.400 --> 00:24:06.149
expect next week our four questions will


00:24:06.159 --> 00:24:09.110
be on black holes, dark matter, dark


00:24:09.120 --> 00:24:11.190
energy, and life elsewhere.


00:24:11.200 --> 00:24:13.110
>> Yeah, there's there's a good chance they


00:24:13.120 --> 00:24:14.789
will.


00:24:14.799 --> 00:24:16.470
>> That will be the standard.


00:24:16.480 --> 00:24:18.549
>> Yep. Very good. Thank you, Ben. Uh,


00:24:18.559 --> 00:24:20.230
lovely to hear from you. Hope all is


00:24:20.240 --> 00:24:24.070
well in Kent. Our final question comes


00:24:24.080 --> 00:24:26.470
from Jud.


00:24:26.480 --> 00:24:29.190
>> Good day, Fred and Andrew. It's Jud from


00:24:29.200 --> 00:24:31.830
Brisbane. Been a big fan of the show for


00:24:31.840 --> 00:24:34.789
a long time. My wife and I were


00:24:34.799 --> 00:24:38.390
listening to a recent episode uh where


00:24:38.400 --> 00:24:40.710
one of the stories was about the uh spun


00:24:40.720 --> 00:24:43.269
out asteroid that's spinning at a


00:24:43.279 --> 00:24:46.710
incredibly fast rate. And you know we


00:24:46.720 --> 00:24:50.870
found Andrew's um thought experiments um


00:24:50.880 --> 00:24:53.590
about how that would affect Earth if we


00:24:53.600 --> 00:24:57.269
were spinning at a similar rate. Um and


00:24:57.279 --> 00:25:00.149
yeah got my head spinning and uh came up


00:25:00.159 --> 00:25:02.950
with lots of other thought experiments.


00:25:02.960 --> 00:25:06.870
Um uh first my question is uh what is


00:25:06.880 --> 00:25:09.909
the current speed of the earth's


00:25:09.919 --> 00:25:13.110
rotation? Um


00:25:13.120 --> 00:25:18.470
and yeah does that speed affect the pole


00:25:18.480 --> 00:25:23.750
of gravity that we feel on earth? Um


00:25:23.760 --> 00:25:27.510
like for instance if uh if I weigh 100


00:25:27.520 --> 00:25:31.830
kg at spinning at this rate of speed uh


00:25:31.840 --> 00:25:34.310
if the earth stops spinning tomorrow


00:25:34.320 --> 00:25:39.029
would I weigh significantly more? Just


00:25:39.039 --> 00:25:41.190
wondering about that. And another


00:25:41.200 --> 00:25:46.390
question, um, would I weigh less at the


00:25:46.400 --> 00:25:49.590
equator than I would standing at the


00:25:49.600 --> 00:25:52.310
north or south pole because the equator


00:25:52.320 --> 00:25:55.269
is spinning much more rapidly than the


00:25:55.279 --> 00:25:59.750
Earth is at the poles. So, just uh some


00:25:59.760 --> 00:26:02.470
thoughts to make your head spin and


00:26:02.480 --> 00:26:05.750
maybe give me some answers. Thank you.


00:26:05.760 --> 00:26:07.830
>> Thank you, Jud. Thanks to you and your


00:26:07.840 --> 00:26:09.510
wife for being fans of the show for so


00:26:09.520 --> 00:26:11.750
long. Much appreciated and uh we can


00:26:11.760 --> 00:26:13.909
make this quick. Yes. And we're finished


00:26:13.919 --> 00:26:16.950
for the No. Um there's a lot more to it


00:26:16.960 --> 00:26:19.269
than that, but uh I think he he he


00:26:19.279 --> 00:26:20.870
pretty well nailed a few of the thoughts


00:26:20.880 --> 00:26:23.269
that he's had in terms of what the


00:26:23.279 --> 00:26:25.029
answers are. Uh what is the current


00:26:25.039 --> 00:26:26.789
speed of Earth's rotation? If you listen


00:26:26.799 --> 00:26:28.630
to the Monty Python song from the life


00:26:28.640 --> 00:26:31.510
of Brian, or was it one of the others?


00:26:31.520 --> 00:26:33.590
Um,


00:26:33.600 --> 00:26:35.029
yeah, they they were wrong, weren't


00:26:35.039 --> 00:26:37.510
they, with their assessment of the speed


00:26:37.520 --> 00:26:42.390
of the rotation of the planet. Um,


00:26:42.400 --> 00:26:45.830
I can't remember I I do remember from I


00:26:45.840 --> 00:26:46.950
don't know know what the speed is, but


00:26:46.960 --> 00:26:48.470
I'll get to that in a second. I can't


00:26:48.480 --> 00:26:49.990
remember what the song says, but I do


00:26:50.000 --> 00:26:52.310
remember listening to that song a long


00:26:52.320 --> 00:26:54.310
time ago and thinking, "Yeah, pretty


00:26:54.320 --> 00:26:56.470
well most of the astronomical statistics


00:26:56.480 --> 00:26:58.950
in it are correct." uh or they were when


00:26:58.960 --> 00:27:02.710
it was written back in the day. Um but


00:27:02.720 --> 00:27:05.750
uh Jud is right. Um the speed of


00:27:05.760 --> 00:27:08.789
rotation at the earth on the equator,


00:27:08.799 --> 00:27:10.789
which is where your linear speed is


00:27:10.799 --> 00:27:15.190
maximum, is uh 1,600 kilometers an hour.


00:27:15.200 --> 00:27:19.190
So that's significant. It's about uh


00:27:19.200 --> 00:27:22.870
half a kilometer/s roughly. Uh, and


00:27:22.880 --> 00:27:25.190
that's why you tend to build space


00:27:25.200 --> 00:27:27.830
launch sites at the equator because


00:27:27.840 --> 00:27:31.190
you've got that additional.5


00:27:31.200 --> 00:27:32.870
kilometers/s.


00:27:32.880 --> 00:27:34.230
That's quite significant when you're


00:27:34.240 --> 00:27:36.470
trying to get up to 8 kilometers/s to


00:27:36.480 --> 00:27:39.029
get into into orbit. So, you're kind of


00:27:39.039 --> 00:27:41.350
a 16th of the way there already just by


00:27:41.360 --> 00:27:43.510
putting your launch site on the equator


00:27:43.520 --> 00:27:45.669
and of course launching towards the east


00:27:45.679 --> 00:27:46.950
which is the direction that we're


00:27:46.960 --> 00:27:50.310
rotating in. Um, at middle latitudes it


00:27:50.320 --> 00:27:53.190
reduces. At our latitude here in uh, New


00:27:53.200 --> 00:27:56.389
South Wales, it's about 1,400 kilometers


00:27:56.399 --> 00:28:00.230
per hour. Um, uh, at Jud's latitude in


00:28:00.240 --> 00:28:02.310
Brisbane, it's a little bit less. Not


00:28:02.320 --> 00:28:05.750
that much less, though. Uh, but there's


00:28:05.760 --> 00:28:07.750
So, what's the effect on your weight?


00:28:07.760 --> 00:28:09.990
That's the interesting thing. Yeah.


00:28:10.000 --> 00:28:14.070
>> And, um, there are two two parts to


00:28:14.080 --> 00:28:16.630
this. Um,


00:28:16.640 --> 00:28:19.430
one is kind of what we've just alluded


00:28:19.440 --> 00:28:23.669
to, the fact that you are rotating uh


00:28:23.679 --> 00:28:26.630
1,600 kilometers uh an hour, roughly


00:28:26.640 --> 00:28:29.269
1,000 miles an hour. Um, it basically


00:28:29.279 --> 00:28:31.350
there's a centrifugal force that means


00:28:31.360 --> 00:28:34.389
that you are slightly lighter. Uh, your


00:28:34.399 --> 00:28:36.310
mass doesn't change of course, but your


00:28:36.320 --> 00:28:38.870
weight does because of that centrifugal


00:28:38.880 --> 00:28:42.789
force. But there there is another effect


00:28:42.799 --> 00:28:45.590
that acts with that too. And that's


00:28:45.600 --> 00:28:48.389
because the Earth isn't spherical. It's


00:28:48.399 --> 00:28:50.630
slightly bulging. And in the center,


00:28:50.640 --> 00:28:53.830
it's what we call an abl spheroid.


00:28:53.840 --> 00:28:58.710
>> And at the equator, you're about 20


00:28:58.720 --> 00:29:00.549
kilometers


00:29:00.559 --> 00:29:02.950
further away from the Earth's center of


00:29:02.960 --> 00:29:06.310
gravity than you are at the poles. And


00:29:06.320 --> 00:29:10.149
so that too reduces the gravitational


00:29:10.159 --> 00:29:13.029
pull that you feel. Um so those two


00:29:13.039 --> 00:29:15.669
things together the equatorial bulge of


00:29:15.679 --> 00:29:18.070
the earth and the centrifugal force of


00:29:18.080 --> 00:29:21.269
the earth's rotation come they basically


00:29:21.279 --> 00:29:24.789
combine to give you a figure that's a


00:29:24.799 --> 00:29:28.710
bit less than 1% of your weight changes


00:29:28.720 --> 00:29:30.310
if you're at the equator compared with


00:29:30.320 --> 00:29:30.870
the poles.


00:29:30.880 --> 00:29:32.630
>> That that'd be a lot for some people


00:29:32.640 --> 00:29:33.110
maybe.


00:29:33.120 --> 00:29:35.110
>> Yes. Yeah. that I mean it means that if


00:29:35.120 --> 00:29:38.549
you do weigh 100 kg then at the equator


00:29:38.559 --> 00:29:40.470
then you're only going to be 99 at the


00:29:40.480 --> 00:29:40.950
pole.


00:29:40.960 --> 00:29:41.669
>> Yeah.


00:29:41.679 --> 00:29:43.350
>> No, I've got it the other way around. If


00:29:43.360 --> 00:29:45.750
you're 100 kg at the pole, you're only


00:29:45.760 --> 00:29:47.430
going to be 99 at the equator.


00:29:47.440 --> 00:29:49.269
>> I knew what you meant.


00:29:49.279 --> 00:29:50.710
>> Yeah.


00:29:50.720 --> 00:29:54.950
>> Um yeah, it's fascinating really. And um


00:29:54.960 --> 00:29:58.470
yeah, that was one of his questions. Um


00:29:58.480 --> 00:30:00.950
weight at the equator versus the poles.


00:30:00.960 --> 00:30:04.710
Uh what would happen if Earth stops


00:30:04.720 --> 00:30:07.510
spinning? Like I think we'd all be


00:30:07.520 --> 00:30:08.950
doomed for starters. That would be the


00:30:08.960 --> 00:30:10.630
end.


00:30:10.640 --> 00:30:11.190
>> But um


00:30:11.200 --> 00:30:13.590
>> we'd all be projected eastwards at uh


00:30:13.600 --> 00:30:15.909
1,600 kilometers an hour if you're on


00:30:15.919 --> 00:30:16.710
the equator.


00:30:16.720 --> 00:30:19.430
>> Yeah. Yeah. That'd be that'd be pretty


00:30:19.440 --> 00:30:20.870
messy. Um


00:30:20.880 --> 00:30:23.110
>> but it Yeah. But if the Earth stopped


00:30:23.120 --> 00:30:25.190
spinning, you'd only have that uh


00:30:25.200 --> 00:30:28.230
equatorial bulge component that's


00:30:28.240 --> 00:30:29.830
reducing your weight. the fact that


00:30:29.840 --> 00:30:31.110
you're a little bit further away from


00:30:31.120 --> 00:30:32.789
the center and that's almost negligible


00:30:32.799 --> 00:30:33.669
on its own.


00:30:33.679 --> 00:30:37.590
>> Yeah, fair enough. That was easy. And I


00:30:37.600 --> 00:30:39.190
found that Monty Python song. It was


00:30:39.200 --> 00:30:40.870
from the meaning of life, not from the


00:30:40.880 --> 00:30:42.070
life of Brian.


00:30:42.080 --> 00:30:42.789
>> That's right.


00:30:42.799 --> 00:30:45.269
>> And it's called the Galaxy song. And the


00:30:45.279 --> 00:30:47.350
first verse first verse says, just


00:30:47.360 --> 00:30:48.630
remember that you're standing on a


00:30:48.640 --> 00:30:51.350
planet that's evolving and revolving at


00:30:51.360 --> 00:30:54.630
900 miles an hour.


00:30:54.640 --> 00:30:57.510
>> Um, which is Yeah. All right. So, it's


00:30:57.520 --> 00:31:00.310
it's uh A bit slow.


00:31:00.320 --> 00:31:02.870
>> 100 miles an hour slow. Yeah,


00:31:02.880 --> 00:31:05.029
>> but it rhymes.


00:31:05.039 --> 00:31:07.350
>> That's it. A thousand would have rhymed.


00:31:07.360 --> 00:31:08.549
>> It would have worked.


00:31:08.559 --> 00:31:08.950
>> Yeah.




00:31:09.440 --> 00:31:11.830
>> Oh, well, maybe they needed two words


00:31:11.840 --> 00:31:13.350
rather than No, it would have still been


00:31:13.360 --> 00:31:13.830
two words.


00:31:13.840 --> 00:31:16.389
>> Or or or Andrew, maybe the Earth has


00:31:16.399 --> 00:31:18.470
speeded up since they recorded the song.


00:31:18.480 --> 00:31:20.149
>> That's poss. It's slowing down though,


00:31:20.159 --> 00:31:21.110
isn't it?


00:31:21.120 --> 00:31:22.870
>> Yes.


00:31:22.880 --> 00:31:24.870
Yeah.


00:31:24.880 --> 00:31:26.310
>> Well, eventually their song will be


00:31:26.320 --> 00:31:27.830
right.


00:31:27.840 --> 00:31:30.549
Yes, it will.


00:31:30.559 --> 00:31:31.190
>> That's right.


00:31:31.200 --> 00:31:32.230
>> Oh gosh.


00:31:32.240 --> 00:31:34.470
>> All right. Um, thank you so much, Jud.


00:31:34.480 --> 00:31:36.310
Lovely to hear from you. Hope all is


00:31:36.320 --> 00:31:38.870
well in Brisbane. Uh, sorry about your


00:31:38.880 --> 00:31:42.549
football team. Not. Um, and I think that


00:31:42.559 --> 00:31:44.310
brings us to the end. Uh, if you have


00:31:44.320 --> 00:31:47.269
questions for us, uh, we would love to


00:31:47.279 --> 00:31:49.110
hear from you. Uh, you can go to our


00:31:49.120 --> 00:31:51.909
website, spacenuts.io, io and click on


00:31:51.919 --> 00:31:55.509
the AMA uh link at the top of the page


00:31:55.519 --> 00:31:57.350
uh where you can ask me anything or ask


00:31:57.360 --> 00:31:59.190
me and I'll give it to Fred to figure it


00:31:59.200 --> 00:32:02.230
out. Uh so uh send us text and audio


00:32:02.240 --> 00:32:03.669
questions. Don't forget to tell us who


00:32:03.679 --> 00:32:05.750
you are and where you're from. And a


00:32:05.760 --> 00:32:08.389
little request if you will uh when you


00:32:08.399 --> 00:32:10.549
uh next listen or are listening to us


00:32:10.559 --> 00:32:12.710
right now, please leave a review on


00:32:12.720 --> 00:32:15.830
whatever podcast platform you uh use


00:32:15.840 --> 00:32:18.310
because uh reviews are very handy. Um,


00:32:18.320 --> 00:32:21.990
it sort of moves us up some laddery


00:32:22.000 --> 00:32:25.909
thing, ranking thing, which is very good


00:32:25.919 --> 00:32:28.470
for us apparently. I don't understand


00:32:28.480 --> 00:32:31.509
how this works. It's it's all to do with


00:32:31.519 --> 00:32:34.789
gravity. Uh, and thank you, Fred, uh,


00:32:34.799 --> 00:32:36.950
once again for helping us out today. I


00:32:36.960 --> 00:32:40.230
think you did all the work, actually.


00:32:40.240 --> 00:32:42.230
>> Nice to help, Andrew. Always good to


00:32:42.240 --> 00:32:43.750
talk. And we'll catch up again.


00:32:43.760 --> 00:32:45.350
>> We will, Professor Fred Watson,


00:32:45.360 --> 00:32:48.470
astronomer at large. And thanks to Hugh


00:32:48.480 --> 00:32:51.430
in the studio, although he couldn't be


00:32:51.440 --> 00:32:56.310
with us today, he um had a thought and


00:32:56.320 --> 00:32:59.110
um it was experimental and he's going to


00:32:59.120 --> 00:33:00.789
go and investigate that right now and


00:33:00.799 --> 00:33:02.950
see if it's real.


00:33:02.960 --> 00:33:04.389
I don't know what that means. Uh and


00:33:04.399 --> 00:33:05.909
from me, Andrew Dunley, thanks for your


00:33:05.919 --> 00:33:07.029
company. We'll see you on the next


00:33:07.039 --> 00:33:09.430
episode of Space Nuts. Bye-bye.


00:33:09.440 --> 00:33:11.669
>> Space Nuts. You've been listening to the


00:33:11.679 --> 00:33:14.710
Space Nuts podcast


00:33:14.720 --> 00:33:17.669
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00:33:20.320 --> 00:33:22.710
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