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Cosmic Queries: Time Dilation, Black Holes, and Gravastars
In this thought-provoking Q&A edition of Space Nuts, hosts Andrew Dunkley and Professor Fred Watson tackle a range of intriguing questions from listeners around the globe. From the complexities of time dilation near supergiant stars to the mysteries surrounding black holes and the hypothetical concept of gravastars, this episode is a deep dive into the fabric of our universe.
Episode Highlights:
- Time Dilation Near Supergiants: Andrew and Fred discuss the effects of gravity on time near supergiant stars and whether significant time dilation occurs compared to black holes.
- Black Holes and Stars: A listener inquires why black holes can’t revert to stars, prompting a fascinating exploration of singularity and the structure of stars.
- Understanding Atoms and Black Holes: The hosts clarify the nature of atoms, free space, and how density calculations relate to black holes, addressing the paradox of infinite density.
- Redshift Limits and Gravastars: The episode wraps up with an examination of redshift limits in the expanding universe and a discussion about the theoretical existence of gravastars, including their implications for our understanding of cosmic phenomena.
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Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.
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00:00:00 --> 00:00:01 Andrew Dunkley: Hello again. Thanks for joining us. This is
00:00:01 --> 00:00:04 Space Nuts Q and A edition. My name is Andrew
00:00:04 --> 00:00:06 Dunkley. This will be our last official show
00:00:06 --> 00:00:09 for 2025. We'll go into a short
00:00:09 --> 00:00:12 recess and be back with you early in the
00:00:12 --> 00:00:15 new year. but we've got some questions
00:00:15 --> 00:00:17 to nail down before any of that happens.
00:00:17 --> 00:00:20 And we've got a whole bunch of topics that
00:00:20 --> 00:00:23 seem to have stirred the imaginations of
00:00:23 --> 00:00:25 our audience. Andrew wants to know about time
00:00:25 --> 00:00:27 dilation of stuff. Stars.
00:00:28 --> 00:00:31 Adriano is talking black holes becoming
00:00:31 --> 00:00:33 stars. Ishtok is wanting
00:00:34 --> 00:00:36 to ask about free space.
00:00:38 --> 00:00:40 I always thought it was expensive, especially
00:00:41 --> 00:00:43 all the space around where we live. Yo.
00:00:43 --> 00:00:46 And Gergo, Redshift and Gravastars.
00:00:46 --> 00:00:49 We will tackle all of that in this edition of
00:00:49 --> 00:00:52 space nuts. 15 seconds. Guidance is
00:00:52 --> 00:00:53 internal.
00:00:53 --> 00:00:56 Professor Fred Watson: 10, 9. Ignition
00:00:56 --> 00:00:57 sequence. Star space nuts.
00:00:57 --> 00:00:59 Andrew Dunkley: 5, 4, 3, 2.
00:00:59 --> 00:01:02 Professor Fred Watson: 1. 2, 3, 4, 5, 5, 4, 3,
00:01:02 --> 00:01:02 2, 1.
00:01:03 --> 00:01:05 Andrew Dunkley: Space nuts. Astronauts report it feels good.
00:01:07 --> 00:01:09 And here he is again. It's professor Fred
00:01:09 --> 00:01:11 Watson, astronomer at large. Hello Fred.
00:01:12 --> 00:01:13 Professor Fred Watson: Hello Andrew.
00:01:14 --> 00:01:15 Andrew Dunkley: Good to see you again.
00:01:15 --> 00:01:16 Professor Fred Watson: Fancy seeing you here.
00:01:16 --> 00:01:18 Andrew Dunkley: How odd. How strange.
00:01:18 --> 00:01:19 Professor Fred Watson: How strange.
00:01:20 --> 00:01:22 Andrew Dunkley: getting ready for your Christmas break. I
00:01:22 --> 00:01:24 mean you've just come back from a break so
00:01:24 --> 00:01:26 you'd be, you know, probably
00:01:27 --> 00:01:29 feeling rather relaxed.
00:01:30 --> 00:01:32 Professor Fred Watson: Well, no, because only the last six days
00:01:32 --> 00:01:33 weren't work.
00:01:35 --> 00:01:38 Yeah. So, no, it's not quite
00:01:38 --> 00:01:39 true because we did have some time off with
00:01:39 --> 00:01:42 my family in Scotland. but we did have a
00:01:42 --> 00:01:43 proper holiday at the end of our trip. But
00:01:43 --> 00:01:46 yes, we did two months of pretty hard work
00:01:46 --> 00:01:48 actually. We had a tour in Japan and then a
00:01:48 --> 00:01:50 conference in Ireland and a few other things
00:01:50 --> 00:01:53 like that that kept us busy. So if
00:01:53 --> 00:01:53 you, if you want.
00:01:53 --> 00:01:56 Andrew Dunkley: To call international travel a job, that's,
00:01:56 --> 00:01:58 you know, that's fine.
00:01:59 --> 00:02:02 Professor Fred Watson: want to call us work. if you. Yeah,
00:02:02 --> 00:02:04 but when you've got a tour group, when you
00:02:04 --> 00:02:07 got 20 people who you entertained
00:02:07 --> 00:02:10 for a month, it's actually three and a half
00:02:10 --> 00:02:12 weeks. it is work.
00:02:12 --> 00:02:15 Andrew Dunkley: Yeah. Yeah. Well we've got a similar problem
00:02:15 --> 00:02:17 in the coming week or two with four
00:02:17 --> 00:02:18 grandchildren that we're.
00:02:19 --> 00:02:19 Professor Fred Watson: To the cave.
00:02:19 --> 00:02:20 Speaker C: Yeah.
00:02:20 --> 00:02:22 Professor Fred Watson: To be honest, I'd rather have 20 tourists
00:02:22 --> 00:02:24 than four grandchildren. Although my
00:02:24 --> 00:02:26 grandchildren are now totally self propelled.
00:02:26 --> 00:02:28 But for your Yankee swan, Aggie, she's only,
00:02:28 --> 00:02:31 she's, she's nine months yesterday actually.
00:02:31 --> 00:02:34 Anyway, anyway, yes, it's
00:02:34 --> 00:02:37 a matter of. But we. Yeah. So the bottom
00:02:37 --> 00:02:40 line is we will have a relaxing end of year
00:02:40 --> 00:02:40 break.
00:02:40 --> 00:02:43 Andrew Dunkley: I hope very good you mentioned Edinburgh.
00:02:43 --> 00:02:46 Well, our first question comes from Andrew
00:02:46 --> 00:02:48 in Edinburgh. he says, I have a two part
00:02:48 --> 00:02:51 question about the gravity and subsequent
00:02:51 --> 00:02:53 time dilation that occurs in and around
00:02:53 --> 00:02:56 supergiant stars. If the supergiants
00:02:56 --> 00:02:58 can collapse into black holes, then they must
00:02:58 --> 00:03:01 have as much or even more mass than the
00:03:01 --> 00:03:04 resulting black hole. Just spread over a much
00:03:04 --> 00:03:07 large, larger area. I guess my question is,
00:03:07 --> 00:03:10 is there significant time dilation near these
00:03:10 --> 00:03:12 stars or are they simply not dense
00:03:12 --> 00:03:15 enough to have meaningful amounts of time
00:03:15 --> 00:03:18 dilation? If they do, it's weird that
00:03:18 --> 00:03:21 comes up and a slight follow up would
00:03:21 --> 00:03:24 be what about time dilation within
00:03:24 --> 00:03:27 the star itself? Presumably near the core of
00:03:27 --> 00:03:30 these stars, the density ramps right up.
00:03:30 --> 00:03:32 Does a large difference in time dilation
00:03:32 --> 00:03:35 within a star have any impact on how
00:03:35 --> 00:03:38 it behaves? Hope that all makes sense.
00:03:38 --> 00:03:40 Thanks. Love the show. That's Andrew in
00:03:40 --> 00:03:40 Edinburgh.
00:03:41 --> 00:03:43 Professor Fred Watson: They're great questions.
00:03:45 --> 00:03:48 I'm just not sure about
00:03:49 --> 00:03:51 the first sentence. If the
00:03:51 --> 00:03:54 supergiants can collapse into black
00:03:54 --> 00:03:57 holes, then they must have as much or
00:03:57 --> 00:03:59 even more mass than the resulting black hole.
00:03:59 --> 00:04:01 Yeah, okay, I've read that properly now. just
00:04:01 --> 00:04:02 spread it maybe.
00:04:02 --> 00:04:03 Andrew Dunkley: I didn't read it properly.
00:04:03 --> 00:04:05 Professor Fred Watson: No, it's all right. No, it's fine.
00:04:06 --> 00:04:08 so yeah, Andrew's first question. Is there
00:04:08 --> 00:04:10 significant time dilation near these stars?
00:04:10 --> 00:04:11 And the answer is yes.
00:04:13 --> 00:04:15 there would be. it's, I mean the time
00:04:15 --> 00:04:18 dilation in a black hole is
00:04:18 --> 00:04:21 so great that to an outside observer,
00:04:21 --> 00:04:23 time stops on the event horizon.
00:04:24 --> 00:04:27 for a star because it's spread over
00:04:27 --> 00:04:29 a larger volume of space, the time dilation
00:04:29 --> 00:04:32 is nowhere near as great. but time dilation
00:04:32 --> 00:04:34 will be something that you would have to take
00:04:34 --> 00:04:37 into account if you had, a
00:04:37 --> 00:04:39 spacecraft orbiting near a giant star.
00:04:40 --> 00:04:42 the bottom line is with, and time dilation,
00:04:44 --> 00:04:47 it's a little bit spooky in the sense that
00:04:49 --> 00:04:52 to the star itself and to something,
00:04:52 --> 00:04:54 say you've got something in orbit around this
00:04:54 --> 00:04:56 star, their time's ticking away at the normal
00:04:56 --> 00:04:59 rate. The time dilation is only what you see
00:04:59 --> 00:04:59 from the outside.
00:05:00 --> 00:05:02 Andrew Dunkley: So this is basically the same as we were
00:05:02 --> 00:05:04 talking about in the last episode regarding
00:05:04 --> 00:05:06 Mars. Same problem.
00:05:06 --> 00:05:08 Professor Fred Watson: Yes, that's right. It is the same thing.
00:05:08 --> 00:05:11 Yeah. So time ticks away
00:05:11 --> 00:05:14 normally for the star, but to watch
00:05:14 --> 00:05:16 it from the outside, you basically see time
00:05:16 --> 00:05:19 ticking away a little bit more slowly.
00:05:20 --> 00:05:23 so they would have time dilation. M. Andrew's
00:05:23 --> 00:05:26 asking whether they're simply not dense
00:05:26 --> 00:05:28 enough to have a meaningful amount of time
00:05:28 --> 00:05:30 dilation. And I don't think that's true. I
00:05:30 --> 00:05:32 think this time dilation is significant,
00:05:32 --> 00:05:34 especially if you're looking at microseconds,
00:05:34 --> 00:05:37 as we were in the last episode. yeah,
00:05:37 --> 00:05:39 so they do. And look,
00:05:40 --> 00:05:42 you're not talking about time dilation of the
00:05:42 --> 00:05:45 kind that was depicted in interstellar
00:05:45 --> 00:05:48 where time kind of grinds to a halt
00:05:48 --> 00:05:51 almost. it's a more modest amount of
00:05:51 --> 00:05:53 time dilation, but it would actually happen.
00:05:54 --> 00:05:56 And Andrew's follow up question. What about
00:05:56 --> 00:05:58 time dilation within the star itself?
00:05:58 --> 00:06:01 Presumably near the core of these stars, the
00:06:01 --> 00:06:03 density ramps right up. There's a large
00:06:03 --> 00:06:04 difference in.
00:06:04 --> 00:06:05 Andrew Dunkley: I'm not going in there to find.
00:06:05 --> 00:06:08 Professor Fred Watson: Out there's a difference
00:06:08 --> 00:06:10 in time dilation within a star have any
00:06:10 --> 00:06:12 impact on how it behaves. and
00:06:13 --> 00:06:15 there's a curious thing there because as you,
00:06:16 --> 00:06:19 get near the core of an object, with
00:06:19 --> 00:06:22 spherical symmetry, your gravitational
00:06:22 --> 00:06:24 field gets less and less. and in fact at the
00:06:24 --> 00:06:26 center you wouldn't feel any gravity. And
00:06:26 --> 00:06:28 that's because everything's pulling you in
00:06:28 --> 00:06:31 the same direction all around. And so
00:06:31 --> 00:06:33 I believe that time dilation will probably
00:06:33 --> 00:06:35 stop in the middle of a star. That might be
00:06:35 --> 00:06:37 something I've never thought about before.
00:06:37 --> 00:06:40 maybe that's not true because you're still in
00:06:40 --> 00:06:42 a gravitational field. The fact that it
00:06:42 --> 00:06:45 cancels out everywhere. I'll check that
00:06:45 --> 00:06:46 one out actually and try and remember for
00:06:46 --> 00:06:48 our, first show next year, because that's a
00:06:48 --> 00:06:50 really interesting question. Time dilation in
00:06:50 --> 00:06:53 the center of a star, how does it behave?
00:06:54 --> 00:06:54 Andrew Dunkley: very interesting.
00:06:54 --> 00:06:56 Professor Fred Watson: But there wouldn't be a. I think the bottom
00:06:56 --> 00:06:59 line is there wouldn't be a, a big difference
00:06:59 --> 00:07:01 in time dilation from one part of a star to
00:07:01 --> 00:07:03 another. That's, that's what I'm trying to
00:07:03 --> 00:07:03 say.
00:07:03 --> 00:07:05 Andrew Dunkley: But he brings up another interesting point.
00:07:05 --> 00:07:07 You've got time dilation around a massive
00:07:07 --> 00:07:07 star.
00:07:08 --> 00:07:09 Professor Fred Watson: Yep.
00:07:09 --> 00:07:11 Andrew Dunkley: Then it goes, you know, whatever black hole,
00:07:12 --> 00:07:14 the time dilation changes.
00:07:15 --> 00:07:17 Professor Fred Watson: Yes, it does because, as it collapses, the
00:07:17 --> 00:07:20 gravitational field increases.
00:07:20 --> 00:07:23 it increases in sort of
00:07:23 --> 00:07:25 angle in the sense that, you know, it's a
00:07:25 --> 00:07:28 steeper gravitational field as you
00:07:28 --> 00:07:30 get as the black hole collapses. And by that
00:07:30 --> 00:07:33 I'm thinking of the gravitational well, you
00:07:33 --> 00:07:36 know, this dip in the trampoline sheet.
00:07:36 --> 00:07:37 That's the gravitational well of an object
00:07:37 --> 00:07:40 which turns into something like a plug hole
00:07:41 --> 00:07:44 with water going around it as a vortex for
00:07:44 --> 00:07:46 a black hole. so that's what I mean by the
00:07:46 --> 00:07:48 steepness of the gravitational field. and
00:07:48 --> 00:07:51 yes, it is so steep that the Event horizon
00:07:51 --> 00:07:54 delineates where the time dilation becomes,
00:07:54 --> 00:07:56 such that time appears to stop on the surface
00:07:56 --> 00:07:57 of the event horizon.
00:07:57 --> 00:08:00 Andrew Dunkley: Yeah, I've seen that demonstration done with
00:08:00 --> 00:08:03 like a big rubber sheet and they say
00:08:03 --> 00:08:05 that that's the time, space time
00:08:05 --> 00:08:08 continuum and they put a bowling ball in it
00:08:08 --> 00:08:09 and they say. And that's gravity.
00:08:10 --> 00:08:12 Professor Fred Watson: That's right, yep. I know,
00:08:13 --> 00:08:13 yeah.
00:08:15 --> 00:08:17 Andrew Dunkley: It'S a simple way of explaining it, but
00:08:18 --> 00:08:20 that's what it is. I suppose. Great.
00:08:20 --> 00:08:22 questions, Andrew. I hope all is well in
00:08:22 --> 00:08:25 Edinburgh. Fred's home
00:08:25 --> 00:08:28 stomping ground. yep, yep. I'll give you his
00:08:28 --> 00:08:29 address and you can go and rock his roof.
00:08:30 --> 00:08:32 This is Space Nuts with Andrew Dunkley and
00:08:32 --> 00:08:33 Professor Fred Watson.
00:08:33 --> 00:08:36 Ah, we have got an audio question. Fred,
00:08:36 --> 00:08:38 this is from Adriano.
00:08:39 --> 00:08:42 Speaker C: Hi guys. Adriano from Florence in Italy. I
00:08:42 --> 00:08:44 have my first question about black holes. So
00:08:44 --> 00:08:46 if I understood correctly, a star continued
00:08:46 --> 00:08:49 to burn his fuel like hydrogen and helium.
00:08:50 --> 00:08:52 And there are nuclear fusions and there is
00:08:52 --> 00:08:54 enough energy for the star to fight against
00:08:54 --> 00:08:57 its own gravitational pull. But, at some
00:08:57 --> 00:09:00 point there is not enough, fuel and the star
00:09:00 --> 00:09:03 collapses into a black hole. After this, the
00:09:03 --> 00:09:06 black hole will start to absorb material like
00:09:06 --> 00:09:08 hydrogen and then it should have enough
00:09:08 --> 00:09:11 energy, enough fuel to have, nuclear
00:09:11 --> 00:09:14 fusions and to fight against the
00:09:14 --> 00:09:17 gravitational pull. But, so why a
00:09:17 --> 00:09:20 black hole cannot, turn back into a star?
00:09:20 --> 00:09:22 I'm sure this is not possible, but I cannot
00:09:22 --> 00:09:25 understand why. And also guys, we had a lot
00:09:25 --> 00:09:27 of beautiful updates from the princess. Can
00:09:27 --> 00:09:30 we also have some updates from Fred? Thank
00:09:30 --> 00:09:30 you guys.
00:09:30 --> 00:09:33 Andrew Dunkley: Bye bye, Adriano, thank you very much. Fred
00:09:33 --> 00:09:35 gave us his update when he got back,
00:09:37 --> 00:09:39 but. Yeah, your point is well made. Florence,
00:09:39 --> 00:09:41 what a beautiful, beautiful city.
00:09:41 --> 00:09:41 Speaker C: Yeah.
00:09:41 --> 00:09:42 Professor Fred Watson: isn't it just?
00:09:42 --> 00:09:44 Andrew Dunkley: we, we visited Florence a few years ago and
00:09:45 --> 00:09:48 it was, it was amazing.
00:09:48 --> 00:09:49 But it was also terrible timing because it
00:09:49 --> 00:09:51 was All Saints weekend, which is a four day
00:09:51 --> 00:09:54 long weekend and there were like tens of
00:09:54 --> 00:09:56 thousands of people there. You couldn't move.
00:09:57 --> 00:09:59 You absolutely couldn't move. So,
00:10:00 --> 00:10:01 we went to, what was it called, the Ponte
00:10:01 --> 00:10:04 Vecchia, and we couldn't get near it.
00:10:04 --> 00:10:07 You just couldn't. It was it was insane.
00:10:08 --> 00:10:09 Yeah, we didn't know until we got there
00:10:09 --> 00:10:12 that's what was happening. But yeah, we still
00:10:12 --> 00:10:15 got to see it. It was a beautiful place and
00:10:15 --> 00:10:17 all those amazing statues and Galileo got,
00:10:17 --> 00:10:19 got, got up close with Galileo.
00:10:19 --> 00:10:20 Professor Fred Watson: Very good.
00:10:20 --> 00:10:21 Andrew Dunkley: Yeah, yeah.
00:10:21 --> 00:10:24 Professor Fred Watson: Did you see his? I think it's his. It's one
00:10:24 --> 00:10:26 of his fingers or his thumb, I can't remember
00:10:26 --> 00:10:28 which is on display in the science museum
00:10:28 --> 00:10:28 there.
00:10:28 --> 00:10:31 Andrew Dunkley: Oh, no, no, couldn't get near that. yeah,
00:10:31 --> 00:10:33 honestly, it was just mayhem. But, yeah,
00:10:33 --> 00:10:34 understandable though.
00:10:35 --> 00:10:38 all right, so the bottom line with Adriano's
00:10:38 --> 00:10:40 question is, why can't a black hole
00:10:41 --> 00:10:44 turn back into a star? yeah, I
00:10:44 --> 00:10:45 would think there'd be all sorts of reasons
00:10:45 --> 00:10:46 why not.
00:10:47 --> 00:10:49 Professor Fred Watson: Well, that's right. I think once you've
00:10:49 --> 00:10:52 turned into a singularity, as the, you can't
00:10:52 --> 00:10:52 double down.
00:10:56 --> 00:10:57 Andrew Dunkley: Sorry that,
00:10:57 --> 00:11:00 Professor Fred Watson: You took the words out of my mouth. No, you
00:11:00 --> 00:11:02 didn't. I mean, all bets are off basically
00:11:02 --> 00:11:04 once you, Once you've gone into a
00:11:04 --> 00:11:07 singularity. and so I,
00:11:07 --> 00:11:09 think, you know, it's a great thought that,
00:11:10 --> 00:11:13 Adriano's had. I. And it's never occurred
00:11:13 --> 00:11:15 to me before, but, but you know, you're
00:11:15 --> 00:11:17 talking about hydrogen, which certainly would
00:11:17 --> 00:11:19 get sucked into a black hole because a lot of
00:11:19 --> 00:11:22 the gas clouds that, the black
00:11:22 --> 00:11:25 hole, accretion disk would draw
00:11:25 --> 00:11:28 in and suck into the center,
00:11:30 --> 00:11:32 that's hydrogen. and hydrogen is the raw
00:11:32 --> 00:11:35 material of stars. Why can't nuclear fusion
00:11:35 --> 00:11:38 kick in again and drive the star back into
00:11:38 --> 00:11:40 being a star rather than a black hole? And I
00:11:40 --> 00:11:42 think the answer is in structure. so
00:11:42 --> 00:11:45 stars have quite a complex
00:11:45 --> 00:11:48 structure, to make them work. with the,
00:11:49 --> 00:11:51 core, with all the nuclear burning taking
00:11:51 --> 00:11:53 place, then there's a convection zone and
00:11:53 --> 00:11:55 then there's a sort of outer layer before you
00:11:55 --> 00:11:57 get to the photosphere, the layer that you
00:11:57 --> 00:12:00 can see. when you've put something into a
00:12:00 --> 00:12:03 singularity, all structure disappears.
00:12:03 --> 00:12:05 And it
00:12:06 --> 00:12:08 almost relates to, an issue
00:12:08 --> 00:12:11 that occupied the m. Mind of Stephen Hawking
00:12:11 --> 00:12:13 for a while, which is that does information
00:12:14 --> 00:12:16 get lost when it goes into a black
00:12:16 --> 00:12:19 hole? And I think there was some
00:12:19 --> 00:12:21 argument with another well known physicist.
00:12:21 --> 00:12:23 In fact, I think they had a bet, which
00:12:23 --> 00:12:25 Hawking lost. because,
00:12:27 --> 00:12:30 I think the bottom line was Hawking back that
00:12:30 --> 00:12:31 information couldn't come out of a black
00:12:31 --> 00:12:34 hole. But somebody proved a theory that
00:12:34 --> 00:12:35 information could come out of a black hole. I
00:12:35 --> 00:12:37 think I've got the right way.
00:12:38 --> 00:12:41 Basically, it's all completely mangled in
00:12:41 --> 00:12:43 terms of, we don't understand the
00:12:43 --> 00:12:45 physics of what would happen inside a
00:12:45 --> 00:12:48 singularity. We just have no idea what the
00:12:48 --> 00:12:50 physical processes would be. And they almost
00:12:50 --> 00:12:53 certainly would rule out hydrogen
00:12:53 --> 00:12:56 atoms getting together, and with
00:12:56 --> 00:12:59 enough temperature to produce the nuclear
00:12:59 --> 00:13:01 fusion that we see in a normal star. a
00:13:02 --> 00:13:04 black hole is a very abnormal object.
00:13:04 --> 00:13:07 Nothing relates to normal in a black
00:13:07 --> 00:13:10 hole. And so I think that is the answer to
00:13:10 --> 00:13:12 Adriana's question. physics
00:13:12 --> 00:13:14 doesn't work the way it works on the outside
00:13:14 --> 00:13:16 of a black hole, and I think that's why we
00:13:16 --> 00:13:18 don't see black holes turning into stars.
00:13:18 --> 00:13:21 Andrew Dunkley: Yeah, well, there's also the fuel issue,
00:13:21 --> 00:13:24 like, you know, the star has collapsed
00:13:24 --> 00:13:27 because of fuel depletion, has it
00:13:27 --> 00:13:27 not?
00:13:27 --> 00:13:29 Professor Fred Watson: Yes, that's right. But what we're saying and
00:13:29 --> 00:13:31 what Adriano is saying is that, among the
00:13:31 --> 00:13:34 stuff that is accreted by the black hole,
00:13:34 --> 00:13:36 when it's sitting there gobbling stuff up, a
00:13:36 --> 00:13:39 lot of that is hydrogen, which is the fuel.
00:13:39 --> 00:13:42 So they're getting more fuel, but they don't
00:13:42 --> 00:13:44 any longer have the process to make it turn
00:13:44 --> 00:13:47 into something that will deliver energy. I
00:13:47 --> 00:13:48 think that's the bottom line.
00:13:48 --> 00:13:50 Andrew Dunkley: I get it, I get it. Okay.
00:13:51 --> 00:13:52 great question, though, because,
00:13:55 --> 00:13:58 we've been talking black holes
00:13:58 --> 00:14:01 for I don't know how long, probably since the
00:14:01 --> 00:14:02 very beginning of the time that this
00:14:03 --> 00:14:06 podcast began, and I don't think we've ever
00:14:06 --> 00:14:07 been asked that question before.
00:14:07 --> 00:14:08 Professor Fred Watson: No, I think that's right.
00:14:08 --> 00:14:09 Andrew Dunkley: Yeah.
00:14:10 --> 00:14:12 Professor Fred Watson: So it's a lot for our. For our, listeners,
00:14:12 --> 00:14:15 doesn't it, that they can produce questions
00:14:15 --> 00:14:17 that we've never had before after however
00:14:17 --> 00:14:20 many episodes. It's getting on for 500 now.
00:14:20 --> 00:14:21 Andrew Dunkley: This is 582.
00:14:22 --> 00:14:23 Professor Fred Watson: Oh, 582. Okay.
00:14:23 --> 00:14:24 Andrew Dunkley: 582.
00:14:24 --> 00:14:25 Speaker C: Yeah.
00:14:25 --> 00:14:26 Professor Fred Watson: Right. There you go. Getting on for 600.
00:14:27 --> 00:14:29 Andrew Dunkley: Oh, no, it's not. I mean, it's happening
00:14:29 --> 00:14:32 faster because of time dilation and the fact
00:14:32 --> 00:14:35 that we decided to do two episodes
00:14:35 --> 00:14:36 a week instead of one. But.
00:14:37 --> 00:14:40 Professor Fred Watson: But I think it's nuts by definition, isn't
00:14:40 --> 00:14:41 it? I've got a feeling.
00:14:43 --> 00:14:43 Yeah.
00:14:44 --> 00:14:46 Andrew Dunkley: anyway, thank you, Adriano, and hope all is
00:14:46 --> 00:14:49 well in the beautiful Florence. This is Space
00:14:49 --> 00:14:52 Nuts with Andrew Dunkley and Professor Fred
00:14:52 --> 00:14:52 Watson.
00:14:54 --> 00:14:56 Lets take a break from the show to tell you
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00:16:30 --> 00:16:32 Three, two, one.
00:16:33 --> 00:16:34 Space nuts.
00:16:34 --> 00:16:36 Our, next question doesn't come from Italy,
00:16:36 --> 00:16:39 it comes from Slovenia. Russian store.
00:16:39 --> 00:16:42 Yeah. I am listening to your podcast while
00:16:42 --> 00:16:44 driving to and from work. Great show. I hope
00:16:44 --> 00:16:46 you managed to keep control because, you
00:16:46 --> 00:16:49 know, this gets a bit crazy sometimes. I'm
00:16:49 --> 00:16:51 curious about. Wait for it, Fred. Black
00:16:51 --> 00:16:53 holes. we know that an atom is actually a
00:16:53 --> 00:16:56 lot of free space where electrons fly around.
00:16:57 --> 00:17:00 eliminating that, we probably, probably
00:17:00 --> 00:17:02 get a neutron star. Ah, with high density.
00:17:02 --> 00:17:04 But what about a black hole? How does this
00:17:04 --> 00:17:07 work? Where is the free space, that can
00:17:07 --> 00:17:10 be squeezed even further to get a black hole?
00:17:10 --> 00:17:12 get black hole material and density and to
00:17:12 --> 00:17:14 calculate the density of the black hole.
00:17:14 --> 00:17:17 Would it be a correct assumption to take the
00:17:17 --> 00:17:20 event horizon as the boundary and,
00:17:20 --> 00:17:23 based on that, calculate the volume? Or is
00:17:23 --> 00:17:26 it something else? Thank you. Best regards.
00:17:26 --> 00:17:29 Ishtok. another black hole question. Not
00:17:29 --> 00:17:30 surprising. We get a lot of them.
00:17:31 --> 00:17:32 Professor Fred Watson: We do, yeah. So,
00:17:34 --> 00:17:37 it's a great question and, that's absolutely
00:17:37 --> 00:17:39 right. An atom is a lot of free space, empty
00:17:39 --> 00:17:42 space, with a, cloud of electrons doing their
00:17:42 --> 00:17:44 quantum thing. if, you collapse the
00:17:44 --> 00:17:47 space down so that only the electrons are
00:17:47 --> 00:17:49 pushing the, atoms apart, you've got a white
00:17:49 --> 00:17:51 dwarf star, which is called electron
00:17:51 --> 00:17:53 degenerate. and if you get rid of the
00:17:53 --> 00:17:55 electrons, then you get a neutron star
00:17:55 --> 00:17:57 exactly as Ishtok, says, with
00:17:58 --> 00:18:01 very, high density, where only the neutrons
00:18:01 --> 00:18:03 keep the thing from collapsing into a black
00:18:03 --> 00:18:05 hole. But with a black hole,
00:18:07 --> 00:18:09 well, the free space is basically
00:18:09 --> 00:18:11 disappeared down the black hole.
00:18:13 --> 00:18:15 and in terms of its density,
00:18:16 --> 00:18:19 you have a definition of a black
00:18:19 --> 00:18:21 hole. one of the definitions is A point in
00:18:21 --> 00:18:24 space with infinite density. So the
00:18:24 --> 00:18:27 volume is zero. See, Jordy thinks that ah, as
00:18:27 --> 00:18:29 well. He does. Gosh, I don't know what's
00:18:29 --> 00:18:32 happening out there, but yeah, I love it.
00:18:34 --> 00:18:35 Andrew Dunkley: We had to hear him from.
00:18:35 --> 00:18:36 Professor Fred Watson: Yeah.
00:18:36 --> 00:18:37 Andrew Dunkley: For the last show of the year.
00:18:38 --> 00:18:41 Professor Fred Watson: That's right. In full
00:18:41 --> 00:18:44 flight. so. Yes, so it's a point of
00:18:44 --> 00:18:47 infinite density. So it talks a comment about
00:18:47 --> 00:18:48 calculating the density of the black hole.
00:18:48 --> 00:18:50 Would it be a correct assumption to take the
00:18:50 --> 00:18:52 event horizon as the boundary? no, it
00:18:52 --> 00:18:54 wouldn't. The event horizon's just that
00:18:54 --> 00:18:57 imaginary point where of no return.
00:18:57 --> 00:19:00 and the volume is zero. the volume of the
00:19:00 --> 00:19:02 black hole is zero, which is how the, the
00:19:02 --> 00:19:04 density gets infinite because,
00:19:06 --> 00:19:08 mass over density. Sorry, Mass over volume is
00:19:08 --> 00:19:11 density. The mass is a, ah, is a parameter,
00:19:12 --> 00:19:14 but the volume is zero. I've no idea what's
00:19:14 --> 00:19:16 happening out there, Andrew, with Jordy, but
00:19:16 --> 00:19:18 he obviously likes this conversation.
00:19:18 --> 00:19:20 Andrew Dunkley: Yes, yes, he does. He wants in.
00:19:23 --> 00:19:25 dear. yeah, look, I still
00:19:26 --> 00:19:28 don't get black holes
00:19:29 --> 00:19:32 receding into the distance. Yeah,
00:19:32 --> 00:19:35 probably chasing a snake. yeah,
00:19:35 --> 00:19:36 go ahead, Andrew.
00:19:36 --> 00:19:37 Professor Fred Watson: No, it's.
00:19:37 --> 00:19:40 Andrew Dunkley: It's hard to get your head around
00:19:40 --> 00:19:42 something like a black hole
00:19:43 --> 00:19:44 having.
00:19:46 --> 00:19:48 No, no density.
00:19:48 --> 00:19:49 Professor Fred Watson: M. No.
00:19:49 --> 00:19:50 Andrew Dunkley: In my brain.
00:19:50 --> 00:19:51 Professor Fred Watson: No volume.
00:19:51 --> 00:19:52 Andrew Dunkley: No volume.
00:19:52 --> 00:19:54 Professor Fred Watson: It's got no size. It's got zero
00:19:54 --> 00:19:55 dimensions.
00:19:55 --> 00:19:58 Andrew Dunkley: I mean, we, we give them names
00:19:58 --> 00:20:00 based on size and yet it has no size.
00:20:01 --> 00:20:03 Professor Fred Watson: Superlastic. Yeah, well, but it's the mass
00:20:03 --> 00:20:06 that's the thing. So the mass is defined for
00:20:06 --> 00:20:08 a black hole. It's one of the properties that
00:20:08 --> 00:20:11 they have. There's this thing called the no
00:20:11 --> 00:20:13 hair theorem, which I like very much.
00:20:14 --> 00:20:16 Yeah. And it's about, you know, wouldn't.
00:20:16 --> 00:20:16 Andrew Dunkley: They wouldn't.
00:20:17 --> 00:20:19 Professor Fred Watson: Yeah, that's right. Which is.
00:20:20 --> 00:20:23 It's about the very few parameters that you
00:20:23 --> 00:20:25 can get from a black hole. I think it's mass,
00:20:25 --> 00:20:27 charge and spin. I think that's all you know
00:20:27 --> 00:20:30 about a black hole. because the volume zero.
00:20:30 --> 00:20:33 And that's why the density zero. Density is
00:20:33 --> 00:20:36 mass over volume, volume zero. So the density
00:20:36 --> 00:20:38 goes to infinite infinity, but you can vary
00:20:38 --> 00:20:39 the mass.
00:20:39 --> 00:20:41 And that's why we talk about supermassive
00:20:41 --> 00:20:43 black holes and intermediate mass black holes
00:20:43 --> 00:20:44 and things of that sort.
00:20:44 --> 00:20:47 Andrew Dunkley: Okay, so what was the answer to the
00:20:47 --> 00:20:47 question?
00:20:49 --> 00:20:49 Professor Fred Watson: no.
00:20:51 --> 00:20:51 Andrew Dunkley: Righto.
00:20:52 --> 00:20:54 Professor Fred Watson: What was the question again? Hang on.
00:20:55 --> 00:20:57 yeah. Would it be. Yes. Would it be correct
00:20:57 --> 00:20:58 assumption to take the event horizon as a
00:20:58 --> 00:21:00 boundary and use that to calculate the
00:21:00 --> 00:21:03 volume? No. The event horizon is an imaginary
00:21:03 --> 00:21:06 sphere that is where the thing
00:21:06 --> 00:21:08 turns black Basically because no light can
00:21:08 --> 00:21:08 escape.
00:21:09 --> 00:21:12 Andrew Dunkley: Precisely. hope that helped Ishok.
00:21:12 --> 00:21:13 Professor Fred Watson: it's a great question.
00:21:13 --> 00:21:16 Andrew Dunkley: It is terrific question. just a very
00:21:16 --> 00:21:18 difficult subject because we just don't
00:21:19 --> 00:21:21 know a hell of a lot about black
00:21:21 --> 00:21:24 holes. They're just such a mysterious and
00:21:25 --> 00:21:26 weird object. And,
00:21:28 --> 00:21:30 we're still trying to gather information
00:21:30 --> 00:21:32 about them and they just keep throwing up
00:21:32 --> 00:21:35 these curveballs at us and not letting us in.
00:21:35 --> 00:21:37 Not that you want to go in, but you know what
00:21:37 --> 00:21:37 I mean.
00:21:38 --> 00:21:40 Professor Fred Watson: Yes, that's right.
00:21:40 --> 00:21:40 Andrew Dunkley: Yeah.
00:21:40 --> 00:21:41 Professor Fred Watson: Quite soon.
00:21:41 --> 00:21:43 Andrew Dunkley: All right, thanks Ishtok.
00:21:44 --> 00:21:46 Time to take a break from the show to tell
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00:23:12 --> 00:23:13 Professor Fred Watson: Space Nuts.
00:23:14 --> 00:23:16 Andrew Dunkley: We have one more question to finish things
00:23:16 --> 00:23:19 off for 2025. And
00:23:19 --> 00:23:22 it's a real European flavor for this episode.
00:23:22 --> 00:23:25 This is Gergo. Greetings gentlemen.
00:23:25 --> 00:23:28 Gergo from Slovakia here. I have a question
00:23:28 --> 00:23:31 about redshifting. Does it have a limit?
00:23:31 --> 00:23:33 Is there a point beyond which light cannot be
00:23:33 --> 00:23:36 stretched any further? If so, what happens if
00:23:36 --> 00:23:38 the light continues to travel through
00:23:38 --> 00:23:40 expanding space? And the second question.
00:23:41 --> 00:23:43 Could you talk a bit about Gravastars? Do you
00:23:43 --> 00:23:46 think they might be real? thank you for your
00:23:46 --> 00:23:47 time and for The Great show.
00:23:48 --> 00:23:48 Speaker C: Bye.
00:23:49 --> 00:23:51 Andrew Dunkley: Thanks, Georgia. yeah, it's
00:23:52 --> 00:23:55 an eclectic mix of nationalities. This
00:23:55 --> 00:23:56 Fabius was. Yeah, it's terrific.
00:23:57 --> 00:23:57 Professor Fred Watson: Yeah, it's great.
00:23:58 --> 00:24:00 Andrew Dunkley: so two questions he's, thrown into the mix.
00:24:00 --> 00:24:03 yeah. Is there a limit on redshift?
00:24:05 --> 00:24:05 yeah. Good one.
00:24:07 --> 00:24:10 Professor Fred Watson: So, yeah,
00:24:10 --> 00:24:13 it is a good question. I mean, so redshift,
00:24:13 --> 00:24:15 as a term we
00:24:16 --> 00:24:19 define as being due to the expansion of the
00:24:19 --> 00:24:22 universe. and it's slightly
00:24:22 --> 00:24:24 different from the Doppler shift. Doppler,
00:24:25 --> 00:24:27 shift is something we understand. Well, it's
00:24:27 --> 00:24:29 the way the light changes wavelength from a
00:24:29 --> 00:24:31 moving object. But with redshift, we're
00:24:31 --> 00:24:34 talking about space itself. Rather
00:24:34 --> 00:24:36 than objects moving through space. We're
00:24:36 --> 00:24:39 talking about the way space behaves. and so
00:24:39 --> 00:24:41 it's a much more fundamental thing than the
00:24:41 --> 00:24:44 Doppler shift. So in a sense,
00:24:45 --> 00:24:47 there's already a limit to redshift.
00:24:48 --> 00:24:51 but it's one that is
00:24:52 --> 00:24:54 exactly related to the age of the universe.
00:24:57 --> 00:24:59 so what I'm thinking of here is
00:25:00 --> 00:25:02 the, cosmic microwave background
00:25:02 --> 00:25:05 radiation. That's the wall of radiation
00:25:05 --> 00:25:08 which corresponds to the brightness of
00:25:08 --> 00:25:11 the Big Bang fireball. Which
00:25:11 --> 00:25:14 we're still seeing. Because as we look
00:25:14 --> 00:25:17 further into space, we look back in time. So
00:25:17 --> 00:25:19 everywhere in space we see this wall of
00:25:19 --> 00:25:21 radiation. Which is now in the microwave
00:25:21 --> 00:25:23 region of the spectrum. Which is why we call
00:25:23 --> 00:25:24 it the cosmic m. Microwave background
00:25:24 --> 00:25:27 radiation. Yeah. And so, if I
00:25:27 --> 00:25:30 remember rightly, that
00:25:30 --> 00:25:33 is basically the visible flash
00:25:33 --> 00:25:36 of the Big Bang. Because
00:25:36 --> 00:25:38 it was, basically
00:25:39 --> 00:25:42 a visible light flash. It's the visible
00:25:42 --> 00:25:45 flash redshifted by, I think,
00:25:45 --> 00:25:47 about 1300 times.
00:25:48 --> 00:25:51 So everything in the universe must have a.
00:25:51 --> 00:25:54 That we can observe. Must have a redshift
00:25:54 --> 00:25:57 less than that. I think 1300
00:25:57 --> 00:25:59 is the number that comes into my mind. I've
00:25:59 --> 00:26:02 looked at this for a long time, but it's
00:26:02 --> 00:26:05 visible light, Whose
00:26:05 --> 00:26:07 waves have been stretched by that amount to
00:26:07 --> 00:26:10 give us microwaves. So stretched about
00:26:10 --> 00:26:13 1300 times thereabouts. Now,
00:26:15 --> 00:26:18 as the universe expands and time goes
00:26:18 --> 00:26:21 on, that number will increase not
00:26:21 --> 00:26:24 by much. Might become 1301 or
00:26:24 --> 00:26:26 1305. But as time goes on, that number's
00:26:26 --> 00:26:29 increasing. So in a sense, that's a limit
00:26:29 --> 00:26:32 to redshift. physically though,
00:26:32 --> 00:26:34 I don't think there is a limit. You could,
00:26:34 --> 00:26:36 you know, if you expand the universe. If
00:26:36 --> 00:26:38 you're talking about 40 billion years into
00:26:38 --> 00:26:40 the future. And the universe is expanding
00:26:40 --> 00:26:42 more. Yes. The cosmic microwave background.
00:26:42 --> 00:26:45 Is going to be the cosmic long wavelength
00:26:45 --> 00:26:48 radio background. and so,
00:26:49 --> 00:26:51 the wavelength Will have stretched more.
00:26:51 --> 00:26:54 So there isn't a physical limit, but
00:26:54 --> 00:26:57 there is a, ah, a limit in the real
00:26:57 --> 00:27:00 universe, simply because of the age of the
00:27:00 --> 00:27:02 universe. The universe hasn't expanded
00:27:02 --> 00:27:05 for long enough for the redshift to be more
00:27:05 --> 00:27:07 than about 1300. Right,
00:27:08 --> 00:27:08 okay.
00:27:08 --> 00:27:09 Andrew Dunkley: Yeah, got it.
00:27:10 --> 00:27:10 Professor Fred Watson: Good.
00:27:11 --> 00:27:12 What was the other thing? Oh, Gravisars.
00:27:12 --> 00:27:14 Andrew Dunkley: Oh, Gravastars. Yeah, we've had, we've had
00:27:14 --> 00:27:17 questions about Gravastars before, more than
00:27:17 --> 00:27:20 once. it seems to be something that sort of
00:27:20 --> 00:27:23 captured the imagination of people that
00:27:23 --> 00:27:25 are so interested in astronomy and space
00:27:25 --> 00:27:28 science. So I suppose we should
00:27:28 --> 00:27:30 start by reminding people what a gravastar
00:27:30 --> 00:27:32 is supposed to be, because I don't think
00:27:32 --> 00:27:33 we've ever found one.
00:27:34 --> 00:27:37 Professor Fred Watson: No, that's correct. I'm going to read
00:27:37 --> 00:27:39 from that font of all knowledge,
00:27:39 --> 00:27:42 Wikipedia, who I do subscribe to, despite
00:27:42 --> 00:27:44 the fact that they keep asking me for another
00:27:44 --> 00:27:46 subscription. Anyway, that's probably because
00:27:46 --> 00:27:48 I've got more than one username. Never mind,
00:27:48 --> 00:27:51 let me read from Wikipedia. In astrophysics,
00:27:52 --> 00:27:54 a Gravis star, which is a blend word
00:27:54 --> 00:27:57 of gravitational vacuum star,
00:27:57 --> 00:28:00 is an object Hypothesized in a
00:28:00 --> 00:28:02 2001 paper by Pavel O.
00:28:02 --> 00:28:05 Mazur and Emil Motola
00:28:05 --> 00:28:08 as an alternative to the black hole theory.
00:28:09 --> 00:28:11 It has the usual black hole metric
00:28:11 --> 00:28:14 outside of the horizon. And the metric is
00:28:14 --> 00:28:17 just a way of describing space, but de
00:28:17 --> 00:28:19 sittomatric inside. And that's a different
00:28:19 --> 00:28:22 one, don't worry about that. A typical
00:28:22 --> 00:28:24 gravastar is as big as London,
00:28:25 --> 00:28:27 but weighs 10 solar masses.
00:28:28 --> 00:28:31 Yeah. So a neutron star would be about the
00:28:31 --> 00:28:34 size of London, but weigh one solar mass,
00:28:34 --> 00:28:34 basically.
00:28:35 --> 00:28:37 Andrew Dunkley: Didn't they find one in a sewer? they called
00:28:37 --> 00:28:38 it a fratberg or something.
00:28:38 --> 00:28:41 Professor Fred Watson: Fatberg. That's right, yeah. Which was
00:28:41 --> 00:28:43 just about to turn into a gravastar.
00:28:43 --> 00:28:43 Andrew Dunkley: Yes.
00:28:44 --> 00:28:46 Professor Fred Watson: on the horizon there is an ultra thin,
00:28:46 --> 00:28:49 incredibly tight shell of entirely
00:28:49 --> 00:28:52 new unique exotic matter
00:28:52 --> 00:28:54 named galactic Flubber.
00:28:55 --> 00:28:56 Andrew Dunkley: That was close.
00:28:57 --> 00:28:59 Professor Fred Watson: You weren't far off. That's right. Which is
00:28:59 --> 00:29:02 the next thing to a fatberg. Yeah. Anyway,
00:29:02 --> 00:29:04 continuing to read this solution to the
00:29:04 --> 00:29:06 Einstein equations is stable and has
00:29:06 --> 00:29:09 no singularities, which we've just been
00:29:09 --> 00:29:12 talking about singularities, points of zero
00:29:12 --> 00:29:15 volume. Instead, Gravastar is filled with
00:29:15 --> 00:29:17 either dark energy or with vacuum energy,
00:29:17 --> 00:29:20 but also vacuum. only
00:29:20 --> 00:29:23 the inside one, 10 to the 44 times denser
00:29:23 --> 00:29:26 than the outside. I'm not sure how you can
00:29:26 --> 00:29:28 have a vacuum that's 10 to the 44 times
00:29:28 --> 00:29:31 denser than another one, but I'll just let
00:29:31 --> 00:29:32 that pass. Yes.
00:29:34 --> 00:29:36 as a bonus, further theoretical
00:29:36 --> 00:29:38 considerations of gravastars include the
00:29:38 --> 00:29:40 notion of a nestar. A second gravastar
00:29:40 --> 00:29:43 nested within the first one. So that's
00:29:43 --> 00:29:46 the technical definition. I bet you're no
00:29:46 --> 00:29:48 wiser than I am. but the bottom
00:29:48 --> 00:29:50 line is that,
00:29:51 --> 00:29:54 And I'll read again. Mazur and Mottola
00:29:54 --> 00:29:56 suggest that the violent creation of a
00:29:56 --> 00:29:59 gravastar might be an explanation for the
00:29:59 --> 00:30:02 origin of our universe and, many other
00:30:02 --> 00:30:04 universes, because all the matter from a
00:30:04 --> 00:30:06 collapsing star would implode through the
00:30:06 --> 00:30:09 central hole and explode into a new dimension
00:30:09 --> 00:30:12 and expand forever, which would be consistent
00:30:12 --> 00:30:14 with the current theories regarding the Big
00:30:14 --> 00:30:15 Bang.
00:30:16 --> 00:30:19 Andrew Dunkley: Okay, so now that we know what
00:30:19 --> 00:30:22 it is, do you think they exist and
00:30:22 --> 00:30:23 will we ever find one?
00:30:24 --> 00:30:26 Professor Fred Watson: no and no. Basically, it's,
00:30:28 --> 00:30:31 an alternative theory for the Big Bang,
00:30:31 --> 00:30:34 and it's certainly interesting. And,
00:30:34 --> 00:30:37 I, you know, I, I think m.
00:30:37 --> 00:30:39 Gago's asked us to talk about it, and now we
00:30:39 --> 00:30:42 have. So, so,
00:30:42 --> 00:30:44 that's perhaps doing the best we can.
00:30:45 --> 00:30:47 Interesting. There's. There's just one other
00:30:47 --> 00:30:49 sentence I might like to read.
00:30:51 --> 00:30:54 if I can find
00:30:54 --> 00:30:57 it, I've lost it now. Oh, yeah. The
00:30:57 --> 00:31:00 new dimension that will be created in this
00:31:00 --> 00:31:02 implosion. The new dimension
00:31:02 --> 00:31:05 exerts an outward pressure on the Bose
00:31:05 --> 00:31:08 Einstein condensate layer and
00:31:08 --> 00:31:11 prevents it from collapsing further. So
00:31:11 --> 00:31:14 the Bose Einstein condensate. It sounds as
00:31:14 --> 00:31:16 though that's this thinned crust that it's
00:31:16 --> 00:31:19 got rather than an event horizon. And the
00:31:19 --> 00:31:22 Bose Einstein condensate is really
00:31:22 --> 00:31:24 interesting. I think we've just celebrated.
00:31:25 --> 00:31:28 Is it the 30th anniversary
00:31:28 --> 00:31:31 of the first example of a Bose
00:31:31 --> 00:31:34 Einstein condenser being produced? I
00:31:34 --> 00:31:36 think that's right. I think it's 30 years. I
00:31:36 --> 00:31:38 think it's 1995. what is it?
00:31:39 --> 00:31:42 it's a condensation of atoms at very low
00:31:42 --> 00:31:45 temperature that behave like one quantum
00:31:45 --> 00:31:47 object. that's the crucial things. So
00:31:48 --> 00:31:50 it's almost like entanglement, Andrew, where
00:31:50 --> 00:31:52 you've got quantum particles being entangled.
00:31:52 --> 00:31:55 This is a whole bunch of stuff that is so
00:31:55 --> 00:31:57 entangled it just looks like one quantum
00:31:57 --> 00:32:00 object and we can now create them. so
00:32:00 --> 00:32:01 that's what they're saying, that maybe this
00:32:01 --> 00:32:04 thing is made of a Bose Einstein condenser. I
00:32:04 --> 00:32:07 think this is a really good way to end, the
00:32:07 --> 00:32:09 year's, Space Nuts episode because it is
00:32:09 --> 00:32:12 completely off the wall and talking about
00:32:12 --> 00:32:15 stuff that is right at the cutting edge of
00:32:15 --> 00:32:16 physics, which I love.
00:32:16 --> 00:32:19 Andrew Dunkley: Indeed. Thank you for your questions. Gergo
00:32:19 --> 00:32:21 and Hope, you're well. Good, to hear from
00:32:21 --> 00:32:23 you. He's sending questions before so it's
00:32:23 --> 00:32:25 nice to catch up. in fact, I think, I think
00:32:25 --> 00:32:28 Ishtok, has sent questions in before as
00:32:28 --> 00:32:30 well. But, yeah, thank you for your questions
00:32:30 --> 00:32:32 everybody, for contributing to this, the
00:32:32 --> 00:32:34 final episode of 2025. Keep the questions
00:32:34 --> 00:32:37 coming in because we're coming back next
00:32:37 --> 00:32:40 year and we'll need some fresh stuff because
00:32:40 --> 00:32:42 we're down to the last one or two,
00:32:43 --> 00:32:44 which I didn't use because they all came from
00:32:44 --> 00:32:46 the same source and I like to spread the love
00:32:46 --> 00:32:48 a bit. So, we'll get into those next year.
00:32:48 --> 00:32:50 But, go to our website if you'd like to send
00:32:50 --> 00:32:53 a question in. Click on the AMA link at the
00:32:53 --> 00:32:56 top and you can send text and audio questions
00:32:56 --> 00:32:59 there. As always, please remember to tell us
00:32:59 --> 00:33:01 who you are and where you're from while
00:33:01 --> 00:33:03 you're at, on the website. check out how you
00:33:03 --> 00:33:05 might be able to support us, through various
00:33:05 --> 00:33:08 channels. whatever you choose or don't choose
00:33:08 --> 00:33:10 to, we're not going to make you do it. you
00:33:10 --> 00:33:11 can check out the shop as well. That's
00:33:11 --> 00:33:14 another way of supporting us and so on and
00:33:14 --> 00:33:16 so forth. while I think.
00:33:16 --> 00:33:18 Professor Fred Watson: Andrew, while you're talking about the
00:33:18 --> 00:33:20 questions, I think we've got a pending one
00:33:20 --> 00:33:22 still from Rusty, which we just wish to.
00:33:23 --> 00:33:25 We'll take it next year.
00:33:25 --> 00:33:28 Andrew Dunkley: Yes, yes, I recall that. But, we.
00:33:28 --> 00:33:29 I thought we'd sit on it till the new year
00:33:29 --> 00:33:31 because reading the question will actually
00:33:31 --> 00:33:33 take the pulp of the episode.
00:33:37 --> 00:33:39 Professor Fred Watson: Thank you, Andrew. Sorry to interrupt you.
00:33:39 --> 00:33:41 Andrew Dunkley: That's okay. No, that's okay. I just want to
00:33:41 --> 00:33:43 say thank you to you, Fred.
00:33:44 --> 00:33:47 and, and I should also, thank
00:33:47 --> 00:33:49 Jonti because he, he did a, fair chunk of the
00:33:49 --> 00:33:52 show and we also
00:33:52 --> 00:33:54 had our guest presenter, Heidi while I was
00:33:54 --> 00:33:57 away. So thank you to Heidi for her amazing,
00:33:57 --> 00:33:59 contribution because, it really saved my,
00:34:00 --> 00:34:03 my back because, there's probably no way in
00:34:03 --> 00:34:05 the world I could have recorded from a cruise
00:34:05 --> 00:34:07 ship and got away with it. But, yeah,
00:34:07 --> 00:34:08 fantastic. we've got a great team.
00:34:10 --> 00:34:13 and, and you know, bring on the next, the
00:34:13 --> 00:34:14 next year of Space Nuts.
00:34:14 --> 00:34:14 Speaker C: And I.
00:34:14 --> 00:34:16 Andrew Dunkley: Look, I give him a hard time every week, I
00:34:16 --> 00:34:18 do. But I've got to say thanks to Huw in the
00:34:18 --> 00:34:21 studio for his, amazing work.
00:34:22 --> 00:34:24 It's not just our podcast that he looks
00:34:24 --> 00:34:26 after. He's got a whole stable of them and
00:34:26 --> 00:34:29 it's it's basically a full time job trying to
00:34:29 --> 00:34:32 run all and you know there's not much money
00:34:32 --> 00:34:34 in it but there's certainly joy in putting
00:34:34 --> 00:34:37 our skills into something in our
00:34:37 --> 00:34:39 semi retirement from, from radio. So.
00:34:40 --> 00:34:43 Yeah. But also without the audience we would
00:34:43 --> 00:34:45 be nothing. So we send out our
00:34:47 --> 00:34:49 our thanks. We are so grateful to have you
00:34:49 --> 00:34:52 behind us and I do keep an eye on the
00:34:52 --> 00:34:55 audience through the Space Nuts podcast group
00:34:55 --> 00:34:57 on Facebook because they they spend a lot of
00:34:57 --> 00:34:59 time there talking to each other, sharing
00:34:59 --> 00:35:02 pictures, and posing unusual
00:35:02 --> 00:35:04 questions which occasionally we will bring up
00:35:04 --> 00:35:06 on the show. And special thanks to our
00:35:06 --> 00:35:08 sponsors. We've had a few sponsors who've
00:35:08 --> 00:35:11 been with us for quite some time now and, and
00:35:11 --> 00:35:13 you know, obviously we're doing something
00:35:13 --> 00:35:15 right if they're willing to stick with us. So
00:35:16 --> 00:35:18 very much appreciated. thank you
00:35:18 --> 00:35:21 Fred. thank you Jordi and,
00:35:21 --> 00:35:24 and we'll talk to you in the new year.
00:35:25 --> 00:35:27 Professor Fred Watson: Sounds great. Look forward to it Andrew. And
00:35:27 --> 00:35:29 all the very best for the festive season to
00:35:29 --> 00:35:29 you.
00:35:29 --> 00:35:31 Andrew Dunkley: And to you Imani. thank you very much,
00:35:31 --> 00:35:33 Professor Fred Watson, Astronomer at large,
00:35:33 --> 00:35:35 and from me, Andrew Dunkley. Have a great
00:35:35 --> 00:35:37 Christmas. A happy new year. We'll see you in
00:35:37 --> 00:35:40 2026. Until then, bye
00:35:40 --> 00:35:43 bye. You'll be listening to the
00:35:43 --> 00:35:44 Space Nuts podcast
00:35:46 --> 00:35:49 available at Apple Podcasts, Spotify,
00:35:49 --> 00:35:52 iHeartRadio or your favorite podcast
00:35:52 --> 00:35:53 player. You can also stream on
00:35:53 --> 00:35:56 demand@bytes.comm this.
00:35:56 --> 00:35:58 Professor Fred Watson: Has been another quality podcast production
00:35:58 --> 00:35:59 from bytes.com