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Cosmic Queries: Binary Planets, the Nature of Light, and Fast Radio Bursts
In this engaging Q&A episode of Space Nuts, hosts Andrew Dunkley and Professor Fred Watson tackle a series of thought-provoking questions from listeners around the globe. From the intriguing concept of binary planets to the mysteries of light and fast radio bursts, this episode is packed with insightful discussions that will spark your curiosity about the cosmos.
Episode Highlights:
- Binary Planets and Moons: Tony from Scotland wonders if planets and moons can exist in a binary configuration like binary stars. Andrew and Fred Watson explore the formation of such celestial bodies and the gravitational dynamics involved, revealing fascinating examples from our solar system.
- The Nature of Light: Kevin poses a compelling question about the longevity of light from the universe's early days. The hosts discuss how light behaves over vast distances and the implications of an expanding universe on our observations.
- Fast Radio Bursts Explained: Alan from Texas seeks clarity on the strongest fast radio burst ever recorded. Andrew and Fred Watson delve into the nature of these mysterious signals, their origins, and how astronomers measure their distances, shedding light on the ongoing research in this area.
- Vertical Oceans: Rennie brings a whimsical question about Earth's oceans and gravity. The hosts clarify the three-dimensional nature of gravitational wells and how it affects the behaviour of water on our planet.
For more Space Nuts, including our continuously updating newsfeed and to listen to all our episodes, visit our website. Follow us on social media at SpaceNutsPod on Facebook, X, YouTube Music, Tumblr, Instagram, and TikTok. We love engaging with our community, so be sure to drop us a message or comment on your favourite platform.
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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 --> 00:00:02 Andrew Dunkley: Hello, once again, thanks for joining us on
00:00:02 --> 00:00:05 yet another edition of Space Nuts, or
00:00:05 --> 00:00:08 more common than a daily breakfast. Uh, my
00:00:08 --> 00:00:09 name is Andrew Dunkley. It is great to have
00:00:09 --> 00:00:12 your company. Uh, this is a Q and A
00:00:12 --> 00:00:15 edition, and that means, uh, we only use two
00:00:15 --> 00:00:18 letters of the Alphabet. Uh, but, uh, we
00:00:18 --> 00:00:21 also answer questions from the audience. Uh,
00:00:21 --> 00:00:23 Tony wants to know about binary planets and
00:00:23 --> 00:00:26 moons. Are there such things? Uh,
00:00:26 --> 00:00:28 Kevin asks, can light last
00:00:28 --> 00:00:31 forever? Alan wants, uh, to talk about,
00:00:31 --> 00:00:34 um, a story that we did do not so long
00:00:34 --> 00:00:37 ago. The strongest fast radio burst ever
00:00:37 --> 00:00:39 recorded. And Rennie is back with
00:00:39 --> 00:00:42 vertical oceans. That's all coming up
00:00:42 --> 00:00:45 on this episode of space nuts.
00:00:45 --> 00:00:48 Generic: 15 seconds. Guidance is internal.
00:00:48 --> 00:00:50 10, 9. Uh, ignition
00:00:51 --> 00:00:53 sequence start. Space Nuts 5, 4,
00:00:53 --> 00:00:56 3, 2. 1. 2, 3, 4, 5, 5, 4,
00:00:56 --> 00:00:59 3, 2, 1. Astronauts
00:00:59 --> 00:01:01 report it feels good.
00:01:01 --> 00:01:04 Andrew Dunkley: Joining us once again to unravel all of that
00:01:04 --> 00:01:06 is Professor Fred Watson Watson, astronomer
00:01:06 --> 00:01:08 at large. Hello, Fred Watson.
00:01:08 --> 00:01:10 Professor Fred Watson: Andrew. Good to see you again. What a
00:01:10 --> 00:01:11 surprise.
00:01:11 --> 00:01:14 Andrew Dunkley: Yes, indeed. It's good to see you, too. I
00:01:14 --> 00:01:16 actually got to see your office for real the
00:01:16 --> 00:01:18 other day, which is nice. Yeah.
00:01:19 --> 00:01:21 Professor Fred Watson: And you couldn't believe how small it is.
00:01:22 --> 00:01:24 Andrew Dunkley: That's the thing about, uh, cameras in
00:01:24 --> 00:01:26 general. They tend to make things look much,
00:01:26 --> 00:01:27 much bigger than they really are.
00:01:28 --> 00:01:30 Professor Fred Watson: Um, um, but, well, ah, yes, it's in. It's big
00:01:30 --> 00:01:32 enough. But, yes, it's.
00:01:32 --> 00:01:34 Andrew Dunkley: It does the job. I mean, mine's probably
00:01:35 --> 00:01:37 a bit smaller than yours by the look.
00:01:37 --> 00:01:39 Professor Fred Watson: There you go. Yes.
00:01:40 --> 00:01:42 Andrew Dunkley: Um, now, uh, we should get straight to
00:01:42 --> 00:01:44 business. Uh, we've got, uh, four questions
00:01:44 --> 00:01:47 to tackle today, all text questions. And
00:01:47 --> 00:01:49 while I'm at it, I will send out an appeal
00:01:49 --> 00:01:51 for new questions. We're running short.
00:01:52 --> 00:01:55 Um, we sort of threw some together the other
00:01:55 --> 00:01:57 day because I didn't have much to work with
00:01:57 --> 00:01:59 when I got back because I had completely
00:01:59 --> 00:02:02 erased everything that I had done and left it
00:02:02 --> 00:02:04 all to you and Heidi. But, um, now I
00:02:04 --> 00:02:07 need some stuff. So send us some questions
00:02:07 --> 00:02:09 via our website, spacenutspodcast.com or
00:02:09 --> 00:02:12 spacenuts IO audio or text?
00:02:12 --> 00:02:15 We don't mind which. And, uh, yeah, we'll get
00:02:15 --> 00:02:16 stuck into them.
00:02:17 --> 00:02:19 Um, now, Fred Watson, question one.
00:02:20 --> 00:02:22 Hi, Fred Watson. Andrew and or Heidi, Love
00:02:22 --> 00:02:24 the podcast. Keep up the good work, dad jokes
00:02:24 --> 00:02:26 and bizarre background animal noises.
00:02:27 --> 00:02:29 Congratulations on being. Wait for this,
00:02:29 --> 00:02:31 Fred Watson. Congratulations on being the
00:02:32 --> 00:02:34 seventh biggest, uh, astronomical
00:02:34 --> 00:02:37 show. Seventh biggest.
00:02:37 --> 00:02:37 Professor Fred Watson: We were,
00:02:39 --> 00:02:42 um, seven out of the top 50. Yeah.
00:02:43 --> 00:02:45 Andrew Dunkley: Yeah, I thought there were only eight.
00:02:45 --> 00:02:46 Anyway, carry on.
00:02:48 --> 00:02:50 Uh, Tony says the podcast often talks about
00:02:50 --> 00:02:53 binary stars, but can planets and
00:02:53 --> 00:02:55 moons also form in a paired
00:02:55 --> 00:02:58 configuration? Could this happen or would
00:02:58 --> 00:03:00 competing gravitational forces from larger
00:03:00 --> 00:03:03 mass objects make it impossible? I presume
00:03:03 --> 00:03:06 that as we haven't found any binary
00:03:06 --> 00:03:08 planets or moons amongst the myriad
00:03:08 --> 00:03:10 satellites in the solar system, that it's
00:03:10 --> 00:03:13 very unlikely. But is it impossible? That
00:03:13 --> 00:03:16 comes from Tony in Scotland. He's 20
00:03:16 --> 00:03:18 minutes from St Andrews. He thought you'd
00:03:18 --> 00:03:18 like to know that.
00:03:19 --> 00:03:21 Professor Fred Watson: Yeah, that's lovely. Indeed. Uh,
00:03:21 --> 00:03:24 Saint Andrews is right behind me on the wall.
00:03:25 --> 00:03:26 That 17th century map there.
00:03:27 --> 00:03:29 Andrew Dunkley: Yes, yes, I see that. Nice.
00:03:30 --> 00:03:33 Professor Fred Watson: Um, so, uh,
00:03:34 --> 00:03:36 yeah, the answer is yes. Um, now
00:03:36 --> 00:03:39 clearly planets can form moons. We've got
00:03:39 --> 00:03:42 one. And most of the other planets actually,
00:03:42 --> 00:03:44 uh, Mercury and Venus don't have moons, but
00:03:44 --> 00:03:47 all the rest do. Um, but I think that's not
00:03:47 --> 00:03:50 what, um, uh, Tony's asking
00:03:50 --> 00:03:52 about. Uh, it's about,
00:03:53 --> 00:03:55 you know, the idea of things forming in
00:03:55 --> 00:03:58 pairs like, like binary stars where you've
00:03:58 --> 00:04:01 got two stars which might have fairly
00:04:01 --> 00:04:03 comparable masses and orbit around a,
00:04:04 --> 00:04:07 um, you know, a common centre of mass. Yeah.
00:04:07 --> 00:04:09 Uh, which we call the barycenter. So,
00:04:09 --> 00:04:12 um, yes, uh, objects,
00:04:12 --> 00:04:14 stars. We think actually stars form more
00:04:14 --> 00:04:17 commonly in pairs than singly, which is quite
00:04:17 --> 00:04:19 interesting because we don't. The sun doesn't
00:04:19 --> 00:04:22 have a binary companion. Got lost a few
00:04:22 --> 00:04:23 billion years ago and we still don't know
00:04:23 --> 00:04:26 where it is. Uh, that's one of the things
00:04:26 --> 00:04:28 that people actually look for. Sun's sibling
00:04:28 --> 00:04:31 star one that's got identical chemistry to
00:04:31 --> 00:04:33 the sun. There's a few candidates.
00:04:33 --> 00:04:36 Anyway, uh, can planets do that?
00:04:36 --> 00:04:38 Uh, and the answer is yes. Um,
00:04:40 --> 00:04:42 uh, and in fact it's not just
00:04:43 --> 00:04:46 planets, but the smaller,
00:04:46 --> 00:04:49 uh, bodies of the solar system perhaps
00:04:49 --> 00:04:51 more readily form in binaries,
00:04:52 --> 00:04:54 uh, as pairs. Uh, and,
00:04:55 --> 00:04:58 uh, the kind of classic example of
00:04:58 --> 00:05:01 this, um, is when we look
00:05:01 --> 00:05:04 at many asteroids, not all of
00:05:04 --> 00:05:06 them, but many of them are shaped like
00:05:06 --> 00:05:09 peanuts in, you know, a peanut shell
00:05:09 --> 00:05:11 because they've got two lobes to them, two
00:05:11 --> 00:05:14 blobs which are stuck together. And that's
00:05:14 --> 00:05:17 thought to be because, uh, they formed as a
00:05:17 --> 00:05:20 pair of objects, uh, and gradually
00:05:20 --> 00:05:23 spiralled together, not colliding,
00:05:23 --> 00:05:26 but in a fairly gentle, um,
00:05:26 --> 00:05:29 coming together, uh, where basically
00:05:29 --> 00:05:31 they. Gravity just pulls them together and
00:05:31 --> 00:05:33 they stick together and they often form a
00:05:33 --> 00:05:36 region around the join, if I can put it that
00:05:36 --> 00:05:39 way, where material tumbles down from the
00:05:39 --> 00:05:41 surface and collects in that area. And you've
00:05:41 --> 00:05:43 only to think of some of the best known ones,
00:05:44 --> 00:05:46 like, um, uh. Do you remember
00:05:46 --> 00:05:49 Arrokoth? We thought it was a snowman
00:05:49 --> 00:05:52 in the deepest depths of the solar
00:05:52 --> 00:05:54 system. Um, it's actually two pancakes Joined
00:05:54 --> 00:05:57 up effectively. But that's, that's a binary
00:05:57 --> 00:06:00 object. Um, you and I spoke
00:06:00 --> 00:06:03 um, uh back in the um, mid
00:06:03 --> 00:06:06 20 mid 2010s I
00:06:06 --> 00:06:09 think about um, the
00:06:09 --> 00:06:11 comet known as Churyumovka,
00:06:12 --> 00:06:14 Otherwise known as 67p which looked like a
00:06:14 --> 00:06:16 rubber duck. And that's because it had two
00:06:16 --> 00:06:19 lobes as well, a big one and a small one. So
00:06:19 --> 00:06:21 that two lobe um situation very
00:06:21 --> 00:06:24 common among the smaller objects in the solar
00:06:24 --> 00:06:27 system. Uh probably binary
00:06:27 --> 00:06:30 systems that have come together. Not only
00:06:30 --> 00:06:32 that, we know of many uh
00:06:32 --> 00:06:35 asteroids that have moons, um and perhaps the
00:06:35 --> 00:06:38 best known uh, and certainly as far as space
00:06:38 --> 00:06:41 nuts is concerned is that pair known as
00:06:41 --> 00:06:43 Didymos and Dimorphos, uh
00:06:43 --> 00:06:46 which are uh, the pair of asteroids
00:06:46 --> 00:06:49 that the DART spacecraft targeted a
00:06:49 --> 00:06:51 few years ago. Dart uh,
00:06:52 --> 00:06:55 clouted uh Dimorphos uh
00:06:55 --> 00:06:58 firmly in its face, uh at a speed of
00:06:58 --> 00:07:01 6 kilometres per second, half tonne uh of
00:07:01 --> 00:07:04 material and changed its orbit around the
00:07:04 --> 00:07:07 uh, around Didymos by no fewer
00:07:07 --> 00:07:09 than 30 minutes. It was quite a
00:07:10 --> 00:07:12 successful venture. Um, so
00:07:12 --> 00:07:15 that's all telling you that there's pairs of
00:07:15 --> 00:07:17 objects are very, very common. Um
00:07:18 --> 00:07:21 and I suppose the best example
00:07:21 --> 00:07:23 of what you might call a binary planet
00:07:23 --> 00:07:25 because a binary planet you'd expect the two
00:07:25 --> 00:07:28 masses to have roughly equal or similar
00:07:29 --> 00:07:32 characteristics. Uh but the dwarf planet
00:07:32 --> 00:07:34 Pluto and its uh, satellite
00:07:34 --> 00:07:37 Charon, uh, I think Charon is half the
00:07:37 --> 00:07:40 diameter of Pluto if I remember rightly. It's
00:07:40 --> 00:07:42 quite large compared with Pluto and they
00:07:42 --> 00:07:45 orbit around their common centre of Pluto
00:07:45 --> 00:07:48 mass, the barycenter. So uh,
00:07:50 --> 00:07:52 the kind of informal definition of a binary
00:07:52 --> 00:07:55 object um is when the
00:07:55 --> 00:07:58 centre of mass of the two halves of it
00:07:58 --> 00:08:01 are uh, is outside either
00:08:01 --> 00:08:04 body if I can put it that way. So the centre
00:08:04 --> 00:08:05 of mass is somewhere in the space between
00:08:05 --> 00:08:07 them rather than being inside as
00:08:08 --> 00:08:10 the centre of mass of the Earth and Moon is
00:08:10 --> 00:08:12 actually inside the Earth which is why we
00:08:12 --> 00:08:14 consider the moon to be a satellite and not
00:08:14 --> 00:08:17 really a binary object. Making sense
00:08:17 --> 00:08:20 there. Um, that's basically the story. It's
00:08:20 --> 00:08:22 a very common phenomenon.
00:08:23 --> 00:08:24 Andrew Dunkley: Could it work for
00:08:26 --> 00:08:28 planets the size of ours though? Let's say
00:08:28 --> 00:08:30 Venus was out here. Could
00:08:30 --> 00:08:33 we sort of get into that kind of dance with
00:08:33 --> 00:08:35 Venus because they're similar sized planets.
00:08:35 --> 00:08:37 Similar, similar mass.
00:08:38 --> 00:08:40 Professor Fred Watson: They are, that's right. And um,
00:08:41 --> 00:08:43 I'm sure it's not impossible
00:08:44 --> 00:08:47 that a situation like that might
00:08:47 --> 00:08:50 arise. I suspect why it
00:08:50 --> 00:08:52 doesn't is it's linked with
00:08:52 --> 00:08:55 the way we define a planet Andrew.
00:08:55 --> 00:08:58 Uh, because to be a planet an object's got
00:08:58 --> 00:09:01 to have pulled itself into a spherical shape,
00:09:01 --> 00:09:03 but it's also got to have cleared all the
00:09:03 --> 00:09:06 debris around it. Um, and
00:09:06 --> 00:09:08 that's the process of accretion. That's
00:09:08 --> 00:09:11 gravitational sweeping up of the material
00:09:12 --> 00:09:15 within the old protoplanetary disc that
00:09:15 --> 00:09:17 used to be around the sun but is now the
00:09:17 --> 00:09:19 planets. Uh, and so I suspect that
00:09:19 --> 00:09:22 that process itself perhaps
00:09:22 --> 00:09:24 favours, um, single
00:09:24 --> 00:09:27 objects, because anything that looks as
00:09:27 --> 00:09:28 though it's going to be another object the
00:09:28 --> 00:09:31 same size will get swept up by, uh, one.
00:09:31 --> 00:09:33 One or the other. There'll be one of them
00:09:33 --> 00:09:35 that turns out to be dominant. And it's
00:09:35 --> 00:09:38 possible that that's why we see the planets
00:09:38 --> 00:09:40 singly, because they're big and they've swept
00:09:40 --> 00:09:42 up the material around them. Whereas when we
00:09:42 --> 00:09:45 look at the aster moons and things like that,
00:09:45 --> 00:09:48 dwarf planets like Pluto, um, uh,
00:09:48 --> 00:09:50 you might find binary objects are much more
00:09:50 --> 00:09:52 common, uh, because there hasn't been that
00:09:52 --> 00:09:55 gravitational cleaning up of. Of their
00:09:55 --> 00:09:57 environment, if I can put it that way. Yeah.
00:09:57 --> 00:09:58 So I suspect that's the way it works.
00:09:58 --> 00:10:00 Andrew Dunkley: That makes sense. Very good.
00:10:00 --> 00:10:02 All right, so, Tony, it's taken us 10 minutes
00:10:02 --> 00:10:03 to tell you. Yes.
00:10:04 --> 00:10:07 Professor Fred Watson: Sorry about that, Tony, but. Yes, but
00:10:07 --> 00:10:09 great. Give my love to Saint Andrew.
00:10:09 --> 00:10:12 Andrew Dunkley: Yes, yes. He says he's from darkest
00:10:12 --> 00:10:13 Fife.
00:10:14 --> 00:10:15 Professor Fred Watson: Well, Fifes, Um,
00:10:16 --> 00:10:19 it'll be dark soon when we get to
00:10:20 --> 00:10:21 the winter solstice in the northern
00:10:21 --> 00:10:23 hemisphere. But it is a very, very pretty
00:10:24 --> 00:10:27 part of the world. Um, in fact, it was.
00:10:28 --> 00:10:31 It might have been. James, one of the early
00:10:31 --> 00:10:34 kings of Scotland, described it as
00:10:34 --> 00:10:37 a beggar's mantle. Uh, what was it? A
00:10:37 --> 00:10:40 beggar's mantle fringed with gold. And what
00:10:40 --> 00:10:42 he was referring to is that it's this green
00:10:42 --> 00:10:44 landscape, uh, with a lot of agriculture.
00:10:45 --> 00:10:48 Fields are like a beggar's, uh. A beggar's
00:10:48 --> 00:10:50 scarf, which is bits of material sewn
00:10:50 --> 00:10:52 together and fringed with gold because it's
00:10:52 --> 00:10:54 got golden beaches all the way around it.
00:10:54 --> 00:10:55 Andrew Dunkley: Nice. Very nice.
00:10:55 --> 00:10:56 Professor Fred Watson: Yeah. It's a great place.
00:10:56 --> 00:10:59 Andrew Dunkley: Yeah. Thanks, Tony. Thanks for your question.
00:10:59 --> 00:11:00 Next one comes from Kevin.
00:11:00 --> 00:11:00 Professor Fred Watson: Hello.
00:11:00 --> 00:11:03 Andrew Dunkley: I love your show. And please keep Heidi
00:11:03 --> 00:11:05 coming back, even as a guest host with both
00:11:05 --> 00:11:07 of you. We're actually talking about that,
00:11:08 --> 00:11:10 uh, the three of you would be great together.
00:11:10 --> 00:11:13 Oh, that's nice. Uh, my question is,
00:11:13 --> 00:11:15 if the universe is 13 and a half or
00:11:15 --> 00:11:18 so billion years old, uh, how long
00:11:18 --> 00:11:21 before we stop seeing the light from 13 and a
00:11:21 --> 00:11:24 half billion years ago? It seems that every
00:11:24 --> 00:11:26 20 or 30 years we launch a new telescope and
00:11:26 --> 00:11:28 it keeps being able to see further and
00:11:28 --> 00:11:31 further back, but eventually the light that's
00:11:31 --> 00:11:33 13 billion years old will have to be 4
00:11:33 --> 00:11:36 billion years old. Uh, the light can't keep
00:11:36 --> 00:11:39 lasting forever, can it? Uh, I hope
00:11:39 --> 00:11:41 I'm clear enough. I know they say the
00:11:41 --> 00:11:44 universe is expanding out to 46 billion light
00:11:44 --> 00:11:47 years. But uh, we don't know for sure because
00:11:47 --> 00:11:49 we can't see beyond the cosmic microwave
00:11:49 --> 00:11:52 background. Thank you. From Kevin.
00:11:52 --> 00:11:55 It's a good question. We have talked about
00:11:55 --> 00:11:57 the life of light. Um,
00:11:58 --> 00:12:00 that's a good title for a book. The life of
00:12:00 --> 00:12:03 light before. And
00:12:03 --> 00:12:05 I think you did say it does have
00:12:06 --> 00:12:09 a um, you know, a
00:12:09 --> 00:12:11 termination age. Uh,
00:12:11 --> 00:12:14 sometimes light ends where it hits something
00:12:14 --> 00:12:17 or and it turns into something else. But um,
00:12:17 --> 00:12:18 yeah, I can't remember.
00:12:18 --> 00:12:21 Professor Fred Watson: But yeah. So actually it, if it
00:12:21 --> 00:12:23 doesn't hit something, it does pretty well go
00:12:23 --> 00:12:26 on forever. Is that true? Yeah, um,
00:12:27 --> 00:12:30 and it is sort of
00:12:30 --> 00:12:32 counterintuitive. We tend to think things
00:12:32 --> 00:12:34 that go on forever, something wrong with
00:12:34 --> 00:12:34 them.
00:12:37 --> 00:12:40 Um, but uh, electro.
00:12:40 --> 00:12:42 It's not just light, it's electromagnetic
00:12:42 --> 00:12:45 radiation. Uh, it, it basically
00:12:45 --> 00:12:47 keeps going to infinity. Now it might get
00:12:47 --> 00:12:50 very very weak. Um, because of the inverse
00:12:50 --> 00:12:53 square rule. Every uh, as the distance
00:12:53 --> 00:12:56 doubles the um, you know the intensity goes
00:12:56 --> 00:12:58 down by a factor of four because it's the
00:12:58 --> 00:13:01 square of the distance. Um,
00:13:01 --> 00:13:03 but uh,
00:13:04 --> 00:13:07 the, the question that, that Kevin poses,
00:13:07 --> 00:13:10 uh, is, is an interesting one. I
00:13:10 --> 00:13:13 mean uh, where it's absolutely true
00:13:13 --> 00:13:15 that we are seeing the flash of the Big Bang
00:13:15 --> 00:13:17 when we look at the cosmic microwave
00:13:17 --> 00:13:20 background radiation. Um, exactly as he
00:13:20 --> 00:13:23 says, we can't see beyond that. So we
00:13:23 --> 00:13:26 see that as um, brightness
00:13:26 --> 00:13:28 of the sky in microwaves, radio
00:13:28 --> 00:13:31 waves that is everywhere in the sky and it's
00:13:31 --> 00:13:33 almost completely uniform. It's not quite.
00:13:33 --> 00:13:36 And it's just as well because that uh, non
00:13:36 --> 00:13:39 uniformity is caused by the sound
00:13:39 --> 00:13:41 waves within the Big Bang plasma
00:13:42 --> 00:13:45 which eventually uh, is what gave rise to
00:13:45 --> 00:13:47 galaxies and stars and all the rest of it. We
00:13:47 --> 00:13:50 think so. Um, so yes, we're so
00:13:50 --> 00:13:53 we're looking at a, a
00:13:53 --> 00:13:56 boundary uh, beyond which we can't see.
00:13:56 --> 00:13:59 And so I think um,
00:14:00 --> 00:14:03 just clarifying uh, Kevin's
00:14:03 --> 00:14:05 comment, um, that
00:14:05 --> 00:14:07 46 billion light years is
00:14:08 --> 00:14:11 probably what we call the proper radius of
00:14:11 --> 00:14:13 the universe. In other words, it's the radius
00:14:13 --> 00:14:16 of the universe if we could see it all. But
00:14:16 --> 00:14:18 we can't because we're always looking back in
00:14:18 --> 00:14:21 time. So we tend to talk about uh, co.
00:14:21 --> 00:14:22 Moving universe
00:14:23 --> 00:14:26 looking back at a time time. Um,
00:14:27 --> 00:14:29 if we think in terms of look back times
00:14:29 --> 00:14:32 rather than in terms of distances. That's the
00:14:32 --> 00:14:35 short answer. So I'll look back time to the
00:14:35 --> 00:14:38 cosmic microwave background radiation is 13.8
00:14:38 --> 00:14:41 billion years. Um, but the universe probably
00:14:41 --> 00:14:43 goes on a lot further beyond that, exactly as
00:14:43 --> 00:14:45 Kevin said. So we can't really define its
00:14:45 --> 00:14:47 size. Uh, but
00:14:48 --> 00:14:51 what is interesting is that that boundary,
00:14:52 --> 00:14:54 that cosmic microwave background boundary,
00:14:54 --> 00:14:57 is actually receding from us at speed of
00:14:57 --> 00:14:59 light. Uh, and,
00:15:00 --> 00:15:02 um, I, uh, won't go into the details of why
00:15:02 --> 00:15:04 we know that, but it is. It's moving away
00:15:04 --> 00:15:06 from us at the speed of light, but it, but
00:15:06 --> 00:15:09 it's still. The light that it has emitted
00:15:09 --> 00:15:11 is still going on through the universe and
00:15:11 --> 00:15:14 will continue to do so. Uh, eventually, as
00:15:14 --> 00:15:16 the universe expands, it'll get very weak,
00:15:16 --> 00:15:18 particularly if it turns out that dark energy
00:15:18 --> 00:15:21 just keeps on, uh, going. Uh, there's
00:15:21 --> 00:15:23 new evidence that suggests that dark energy
00:15:23 --> 00:15:26 is, is reducing. Uh, which might mean that
00:15:26 --> 00:15:28 one day there is a turnaround and we
00:15:28 --> 00:15:31 might one day be back to the Big Crunch idea
00:15:31 --> 00:15:33 that we had in the 1970s. Or the Gnab
00:15:33 --> 00:15:36 Gibbers, uh, as Brian Schmidt calls
00:15:36 --> 00:15:37 it, so.
00:15:38 --> 00:15:39 Andrew Dunkley: Or the, or the Big Crack.
00:15:40 --> 00:15:42 Professor Fred Watson: Well, the Big Crack could be if it keeps on
00:15:42 --> 00:15:44 expanding. Yeah, the Big Rip, where space
00:15:44 --> 00:15:47 itself just tears apart. I, um,
00:15:47 --> 00:15:50 think that's a weird quantum phenomenon that
00:15:50 --> 00:15:52 I'm not going to get into now. But, um,
00:15:52 --> 00:15:53 something to look forward to anyway in the
00:15:53 --> 00:15:54 distant future.
00:15:55 --> 00:15:57 Andrew Dunkley: Yes, yes, we can
00:15:57 --> 00:16:00 wait. We usually say we can't wait. We can't
00:16:00 --> 00:16:02 wait to examine the samples from
00:16:02 --> 00:16:05 Mars. But we can wait for the Big Rip. Or the
00:16:05 --> 00:16:08 Gnab Gib. Definitely no hurry for that.
00:16:08 --> 00:16:11 Uh, thank you, Kevin. Lovely to hear from
00:16:11 --> 00:16:14 you. And this is Space Nuts Q A
00:16:14 --> 00:16:16 edition with Andrew Dunkley and Professor
00:16:16 --> 00:16:17 Fred Watson Watson.
00:16:20 --> 00:16:21 Generic: Roger, your lot is right here.
00:16:21 --> 00:16:22 Professor Fred Watson: Also Space Nuts.
00:16:23 --> 00:16:25 Andrew Dunkley: Our next question comes from Alan. He's in
00:16:25 --> 00:16:28 San Antonio, Texas. Recently, I was listening
00:16:28 --> 00:16:31 to another podcast where they talked about a
00:16:31 --> 00:16:34 news story about the strongest fast radio
00:16:34 --> 00:16:36 burst ever recorded. Yes, we have talked
00:16:36 --> 00:16:38 about that before. Uh, it's not an astronomy
00:16:38 --> 00:16:41 or science podcast, so, uh, they'll not be
00:16:41 --> 00:16:44 able to answer my question. And he thinks we
00:16:44 --> 00:16:45 can, Fred Watson.
00:16:46 --> 00:16:48 Professor Fred Watson: Anyway, we can put him right.
00:16:49 --> 00:16:52 Andrew Dunkley: They mentioned that most fast radio bursts
00:16:52 --> 00:16:55 were from billions of light years away. My
00:16:55 --> 00:16:58 first thought was, hold on. If we don't know
00:16:58 --> 00:17:01 the cause of FRBs, how can anyone
00:17:01 --> 00:17:03 know the distance to the source? Hopefully
00:17:03 --> 00:17:05 Fred Watson can answer that. Then maybe
00:17:05 --> 00:17:07 Fred Watson will talk about the news item. If
00:17:07 --> 00:17:10 I heard right, the, FRB that, uh, it was
00:17:10 --> 00:17:13 talking about is intrinsically the brightest
00:17:13 --> 00:17:15 ever, and it was in the Milky Way.
00:17:16 --> 00:17:18 Uh, if that is the case, then it's apparent
00:17:18 --> 00:17:20 brightness must have been so powerful that it
00:17:20 --> 00:17:22 saturated the instruments on the telescope.
00:17:22 --> 00:17:25 That comes from Alan in Texas. Yeah, we spoke
00:17:25 --> 00:17:27 about that when it was first uh, published.
00:17:27 --> 00:17:29 The uh, findings. First published. Yeah, the
00:17:29 --> 00:17:32 um, the, the brightest um, ever
00:17:33 --> 00:17:35 fast radio burst or something to that effect.
00:17:35 --> 00:17:37 Uh, so we probably should talk about that
00:17:37 --> 00:17:40 first before we um, answer
00:17:40 --> 00:17:41 the first part of the question.
00:17:42 --> 00:17:45 Professor Fred Watson: Yeah, the goat, wasn't it greatest of all
00:17:45 --> 00:17:46 time? Yes,
00:17:49 --> 00:17:50 but I think we're talking about two different
00:17:50 --> 00:17:52 things because, um,
00:17:53 --> 00:17:55 if you have the intrinsically
00:17:56 --> 00:17:58 greatest of all time within our own Milky
00:17:58 --> 00:18:01 Way, don't get fried. I think,
00:18:01 --> 00:18:04 um. Whoops. Uh, or at least as
00:18:04 --> 00:18:07 exactly as. As Alan
00:18:07 --> 00:18:09 says it would fry the instruments on the
00:18:09 --> 00:18:12 telescope. Exactly right. There certainly
00:18:12 --> 00:18:14 have been, um,
00:18:14 --> 00:18:16 FRBs which
00:18:17 --> 00:18:20 uh, which come from our galaxy.
00:18:20 --> 00:18:21 Um,
00:18:23 --> 00:18:26 they're, they're thought to be flares
00:18:26 --> 00:18:29 on magnetars. Uh, a magnetar is
00:18:29 --> 00:18:31 a highly magnetic neutron star.
00:18:32 --> 00:18:34 Intense magnetic fields, sort of unbelievably
00:18:34 --> 00:18:37 intense. And eventually occasionally you get
00:18:37 --> 00:18:39 flares on these things which give you this
00:18:39 --> 00:18:41 very brief uh, burst of
00:18:41 --> 00:18:44 radio radiation which we call an frb, a
00:18:44 --> 00:18:46 fast radio burst. Um,
00:18:47 --> 00:18:50 but, but that was. So that was one that
00:18:50 --> 00:18:53 was not as powerful as the ones that we see
00:18:53 --> 00:18:55 deep in the universe. The goats. The greatest
00:18:55 --> 00:18:58 of all time. Um, so I'm, I'm m probably
00:18:58 --> 00:19:00 not covering that news item very well. Uh,
00:19:00 --> 00:19:03 but let me just briefly answer the first part
00:19:03 --> 00:19:06 of Alan's question. Um, if we don't know the
00:19:06 --> 00:19:08 cause of FRBs, how can anyone know the
00:19:08 --> 00:19:10 distance to the source? It's a great
00:19:10 --> 00:19:13 question. And um, that was one of the
00:19:13 --> 00:19:16 puzzles. In the early era of fast
00:19:16 --> 00:19:18 radio bursts, there were a lot of them were
00:19:18 --> 00:19:20 detected. They only happened once. There are
00:19:20 --> 00:19:22 a few repeating ones, uh,
00:19:23 --> 00:19:25 but um, most of them only
00:19:26 --> 00:19:28 happen uh, once. Um,
00:19:29 --> 00:19:31 what you have to do is,
00:19:32 --> 00:19:34 uh, when you detect one of these things,
00:19:35 --> 00:19:37 you have to use a radio telescope that is
00:19:37 --> 00:19:40 capable of pinpointing its
00:19:40 --> 00:19:43 direction with very high accuracy. And
00:19:43 --> 00:19:45 that's where ASCAP came in. The Australian,
00:19:46 --> 00:19:49 uh, um, Square Kilometre Array
00:19:49 --> 00:19:51 Pathfinder. Ascap, uh, which is a
00:19:51 --> 00:19:53 telescope in Western Australia. It's an array
00:19:53 --> 00:19:56 of 36 dishes. Um, and
00:19:56 --> 00:19:59 because it's an array like that, it's very,
00:19:59 --> 00:20:02 very good at pinpointing where signals
00:20:02 --> 00:20:04 come from to a very high degree of accuracy.
00:20:04 --> 00:20:07 So if you could do that, and it took them a
00:20:07 --> 00:20:10 while to get that act together, but
00:20:10 --> 00:20:13 they did. Um, and what you can do is then
00:20:13 --> 00:20:16 take that position and look at that point
00:20:16 --> 00:20:19 with a visible light telescope. And
00:20:19 --> 00:20:22 uh, what was found consistently with
00:20:22 --> 00:20:25 fast radio bursts is yes, they come from
00:20:25 --> 00:20:28 distant galaxies. Uh, um,
00:20:28 --> 00:20:30 the puzzle was that they're not usually in
00:20:30 --> 00:20:31 the centre of these galaxies, which is where
00:20:31 --> 00:20:34 you expect all the high energy processes to
00:20:34 --> 00:20:35 take place because there's a supermassive
00:20:35 --> 00:20:38 black hole there. Often they're in the kind
00:20:38 --> 00:20:41 of suburbs of galaxies, which is one
00:20:41 --> 00:20:43 reason why we believe they're these magnetar
00:20:43 --> 00:20:45 flares because then they're not something
00:20:45 --> 00:20:47 associated with a, um, high energy
00:20:47 --> 00:20:50 supermassive black hole. They're associated
00:20:50 --> 00:20:53 with very compact stars. So
00:20:54 --> 00:20:56 if you can identify in a galaxy,
00:20:56 --> 00:20:59 then you can measure the redshift of the
00:20:59 --> 00:21:02 galaxy itself using an optical, a visible
00:21:02 --> 00:21:04 light telescope. That gives you the redshift
00:21:04 --> 00:21:06 which we equate to distance. Uh, so that's
00:21:06 --> 00:21:08 how we know where they are and how far away
00:21:08 --> 00:21:11 they are. And that's really, um, you know,
00:21:11 --> 00:21:14 one of the great stories of the, of the FRB
00:21:14 --> 00:21:17 saga that we have managed to pinpoint these
00:21:17 --> 00:21:19 brief flashes of radiation, they last a
00:21:19 --> 00:21:22 thousandth of a second at most, uh, and find
00:21:22 --> 00:21:24 out where they come from. And it's just
00:21:24 --> 00:21:26 because we can pinpoint their positions very
00:21:26 --> 00:21:28 accurately and then follow it up with optical
00:21:28 --> 00:21:31 or visible light telescopes. I have to say
00:21:31 --> 00:21:33 that one of the, um, uh, great
00:21:35 --> 00:21:37 collaborations uh, in that regard has been
00:21:37 --> 00:21:39 ascap, the Australian Square Kilometre Array
00:21:39 --> 00:21:42 Pathfinder, ah, uh, linking with the
00:21:43 --> 00:21:45 telescopes of the European Southern
00:21:45 --> 00:21:47 Observatory down in Chile, the optical
00:21:47 --> 00:21:49 telescopes, what we call the VLT, the Very
00:21:49 --> 00:21:52 Large Telescope, those four 8.2
00:21:52 --> 00:21:54 metre telescopes that are so good
00:21:55 --> 00:21:57 at uh, measuring the distances to very
00:21:57 --> 00:21:59 distant objects. So that's been a really
00:21:59 --> 00:22:00 great collaboration.
00:22:00 --> 00:22:03 Andrew Dunkley: M. Now, um, you probably
00:22:03 --> 00:22:05 already answered this in the past and my
00:22:05 --> 00:22:07 brain won't let me find the answer,
00:22:08 --> 00:22:10 but what causes fast radio bursts?
00:22:10 --> 00:22:13 Professor Fred Watson: It's what we were saying, the idea of a flare
00:22:14 --> 00:22:16 taking place on the surface of a, ah, highly
00:22:16 --> 00:22:19 magnetised neutron star. Now we find
00:22:19 --> 00:22:21 that very hard to envisage because you and I
00:22:21 --> 00:22:24 have struggled to imagine what neutron stars
00:22:24 --> 00:22:26 are like when we know that they've got
00:22:26 --> 00:22:28 mountains on them that are a few millimetres
00:22:28 --> 00:22:31 high. Um, you know, um, what is
00:22:31 --> 00:22:33 the surface of an neutron star like? It's
00:22:33 --> 00:22:35 just, ah, it's impossible to imagine, um,
00:22:36 --> 00:22:38 and so it's kind of equally impossible to
00:22:38 --> 00:22:40 imagine a flare on one of these things that
00:22:40 --> 00:22:42 is so bright that it outshines the sun for
00:22:43 --> 00:22:45 um, you know, for a thousandth of a second or
00:22:45 --> 00:22:47 outshines the sun's entire radiation,
00:22:48 --> 00:22:50 uh, uh, history for a thousandth of a second.
00:22:51 --> 00:22:52 Amazing stuff.
00:22:52 --> 00:22:54 Andrew Dunkley: Extraordinary. Thanks for the question, Alan.
00:22:54 --> 00:22:55 Hope you're well.
00:22:57 --> 00:23:00 Generic: Zero G and I feel fine.
00:23:00 --> 00:23:01 Andrew Dunkley: Space nuts.
00:23:01 --> 00:23:03 And to our final question today from one of
00:23:03 --> 00:23:06 our regular contributors. Hi, Rennie. Uh, if
00:23:06 --> 00:23:08 I look at the Earth from the distance, let's
00:23:08 --> 00:23:11 say of Earth's moon and Earth is in a
00:23:11 --> 00:23:14 gravitational well, why aren't the
00:23:14 --> 00:23:16 vertical, uh, why aren't the vertical
00:23:16 --> 00:23:19 oceans on Earth that I'm looking at not
00:23:19 --> 00:23:21 dripping down the sides of the Earth towards
00:23:21 --> 00:23:24 the deepest parts of the gravitational well?
00:23:26 --> 00:23:29 Uh, I'm not sure he's serious. Maybe he is.
00:23:29 --> 00:23:32 Um, some people look at
00:23:32 --> 00:23:34 the planet and go, okay, it's a sphere, so
00:23:34 --> 00:23:37 why is everything staying where it is? Why,
00:23:37 --> 00:23:40 why wouldn't the water drip down.
00:23:40 --> 00:23:41 Professor Fred Watson: To the bottom
00:23:43 --> 00:23:46 a big puddle in Antarctica? Um,
00:23:46 --> 00:23:49 well, it, yes, it is in a gravitational well,
00:23:49 --> 00:23:51 but it's a three dimensional one. We, you
00:23:51 --> 00:23:53 know, we look at, uh, depictions
00:23:54 --> 00:23:56 of a gravitational well and it's
00:23:57 --> 00:23:59 a, it's like a trampoline. It's a surface
00:23:59 --> 00:24:02 with a dent in the middle where
00:24:02 --> 00:24:05 you've got planet Earth or whatever,
00:24:05 --> 00:24:08 uh, other gravitational objects, uh, we're
00:24:08 --> 00:24:10 talking about. Uh, so a gravitational well
00:24:10 --> 00:24:13 is, um, a good description because
00:24:13 --> 00:24:15 that's sort of what it looks like, except
00:24:16 --> 00:24:19 that it's a gravitational well in three
00:24:19 --> 00:24:21 dimensions, not two dimensions, as the
00:24:21 --> 00:24:24 surface of a trampoline is. Uh, so it's a
00:24:24 --> 00:24:27 three dimensional entity. And it turns out
00:24:27 --> 00:24:29 that the gravitational well is at the
00:24:29 --> 00:24:32 centre of any gravitating object
00:24:32 --> 00:24:35 like the Earth. So, um, yes, the
00:24:35 --> 00:24:37 oceans do drip down, but they drip down
00:24:37 --> 00:24:40 towards the centre of the Earth, which is
00:24:40 --> 00:24:43 where the gravitational well is, uh,
00:24:43 --> 00:24:45 because it's a three dimensional well, not a
00:24:45 --> 00:24:48 two dimensional one. I do love the idea of
00:24:48 --> 00:24:50 the oceans kind of running down the side
00:24:50 --> 00:24:53 though. It's quite nice to think
00:24:53 --> 00:24:55 about. Fortunately, fortunately
00:24:55 --> 00:24:58 not the way it is because the, uh, the whole
00:24:58 --> 00:25:00 thing exists in three dimensions and we've
00:25:00 --> 00:25:02 got, um, the centre of the Earth as being the
00:25:02 --> 00:25:03 bottom of the gravitational well.
00:25:04 --> 00:25:07 Andrew Dunkley: Indeed. Simple, uh, answer to that
00:25:07 --> 00:25:09 one, Rennie. So thanks for sending your
00:25:09 --> 00:25:11 question in and once again I'll appeal for
00:25:11 --> 00:25:13 new questions. If you'd like to send them
00:25:13 --> 00:25:16 into us, jump on our website. I'll just do a
00:25:16 --> 00:25:19 search for Space Nuts podcast on your
00:25:19 --> 00:25:21 search engine and uh, find us there and, uh,
00:25:21 --> 00:25:24 send us text or
00:25:24 --> 00:25:27 audio questions, uh, um,
00:25:27 --> 00:25:30 through the AMA tab up the top. And
00:25:30 --> 00:25:32 don't uh, forget to tell us who you are and
00:25:32 --> 00:25:34 where you're from. We always like to know
00:25:34 --> 00:25:36 that just so that we can spam you.
00:25:37 --> 00:25:37 Professor Fred Watson: Um.
00:25:39 --> 00:25:40 Andrew Dunkley: Yes, all right.
00:25:40 --> 00:25:41 Professor Fred Watson: Is that what it's for?
00:25:41 --> 00:25:43 Andrew Dunkley: No, of course not.
00:25:44 --> 00:25:47 Of course not. We only send spam to people
00:25:47 --> 00:25:48 who volunteer for it.
00:25:49 --> 00:25:50 Professor Fred Watson: Yes, that's right.
00:25:51 --> 00:25:54 Andrew Dunkley: Uh, thanks, Ronnie, Alan, Kevin and
00:25:54 --> 00:25:56 Tony for your questions today. And thank you,
00:25:56 --> 00:25:58 Fred Watson, as always. It's been great fun.
00:25:58 --> 00:25:58 Generic: Fun.
00:25:59 --> 00:26:01 Professor Fred Watson: It's, it's great to answer the, you know,
00:26:01 --> 00:26:03 questions like that or at least have a crack
00:26:03 --> 00:26:05 at answering them. They're, uh, always
00:26:05 --> 00:26:07 thought provoking. And, um, thanks to all our
00:26:07 --> 00:26:09 listeners. And thanks too to you, Andrew, for
00:26:09 --> 00:26:10 carrying the show forward.
00:26:10 --> 00:26:13 Andrew Dunkley: Oh, my pleasure. I enjoy it. It's great
00:26:13 --> 00:26:16 fun. And we'd thank Huw in the studio, except
00:26:16 --> 00:26:18 he didn't turn up today. He went for a swim
00:26:19 --> 00:26:21 and ended up in Antarctica. So,
00:26:21 --> 00:26:24 um, he
00:26:24 --> 00:26:27 loves it down there. He's, um. Yeah,
00:26:27 --> 00:26:30 he's a fun guy. Uh, and, uh, that's it
00:26:30 --> 00:26:32 from, uh, us for another week. We'll see you
00:26:32 --> 00:26:35 very soon on another edition of Space Nuts.
00:26:35 --> 00:26:37 And from me, Andrew Dunkley. Bye. Bye.
00:26:38 --> 00:26:41 Generic: You've been listening to the Space Nuts
00:26:41 --> 00:26:44 podcast, available at
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00:26:46 --> 00:26:49 iHeartRadio or your favourite podcast
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00:26:51 --> 00:26:51 Bitesz.com Com.
00:26:51 --> 00:26:53 Andrew Dunkley: This has been another quality podcast
00:26:53 --> 00:26:55 production from Bitesz.com