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In this thought-provoking Q&A episode of Space Nuts, host Andrew Dunkley and the ever-insightful Professor Fred Watson dive into a variety of compelling questions from listeners. They tackle the intriguing concept of the universe potentially being born inside a black hole, explore a new theory of gravity, and discuss the ongoing search for the elusive Planet Nine.
Episode Highlights:
- The Universe Inside a Black Hole: Listener Ash from Brisbane poses a fascinating question about the possibility of our universe being trapped inside a black hole and the implications of such a theory. Andrew and Fred Watson discuss the mechanics of black holes and what it would mean for our existence.
- A New Gravity Theory: Casey from Colorado asks about the latest advancements in gravity theories, prompting a discussion on the unification of quantum field theory and relativity, and the potential breakthroughs from Finnish researchers that could reshape our understanding of gravity.
- Understanding Hubble Tension: The duo explains the concept of Hubble tension, highlighting the discrepancies between two methods of measuring the universe's expansion rate and what this could mean for cosmology.
- The Quest for Planet Nine: Simon from New South Wales raises questions about the search for Planet Nine and the methods used to detect it, while Joe from Washington inquires about the limits of gravitational assists for interstellar travel, leading to a discussion on the practicality of such missions.
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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.
(00:00) Welcome to Space Nuts with Andrew Dunkley and Fred Watson Watson
(01:20) Discussion on the universe inside a black hole
(15:00) New theory of gravity from Finnish researchers
(25:30) Explaining Hubble tension
(35:00) The search for Planet Nine and gravitational assists
For commercial-free versions of Space Nuts, join us on Patreon, Supercast, Apple Podcasts, or become a supporter here: https://www.spreaker.com/podcast/space-nuts-astronomy-insights-cosmic-discoveries--2631155/support.
00:00:00 --> 00:00:02 Andrew Dunkley: Hi there. Thanks for joining us. This is a Q and A edition of
00:00:02 --> 00:00:05 Space Nuts. My name is Andrew Dunkley. It's
00:00:05 --> 00:00:08 good to have your company. Uh, today, uh, we
00:00:08 --> 00:00:11 will be hearing questions about, uh,
00:00:11 --> 00:00:14 the universe being inside a black hole. In fact, I
00:00:14 --> 00:00:17 think they're suggesting it was born in a black hole and
00:00:17 --> 00:00:19 is stuck in there. And how do we get out?
00:00:20 --> 00:00:23 We'll also be looking at a new gravity theory. Uh,
00:00:23 --> 00:00:25 theory Hubble tension. Not
00:00:25 --> 00:00:28 surprisingly, questions about planet nine with the
00:00:28 --> 00:00:31 most recent announcement of something being out there that's not
00:00:31 --> 00:00:34 planet nine. And, um,
00:00:34 --> 00:00:37 getting gravity assistance to Max
00:00:37 --> 00:00:39 Delta V. Those are all the questions
00:00:40 --> 00:00:42 coming up on this episode of space nuts.
00:00:42 --> 00:00:45 Voice Over Guy: 15 seconds. Guidance is internal.
00:00:45 --> 00:00:48 10, 9, ignition
00:00:48 --> 00:00:51 sequence time. Uh, space nuts. 5, 4, 3,
00:00:51 --> 00:00:54 2. 1. 2, 3, 4, 5, 5, 4,
00:00:54 --> 00:00:57 3, 2, 1. Space nuts. Astronauts
00:00:57 --> 00:00:58 report it feels good.
00:00:59 --> 00:01:02 Andrew Dunkley: And Fred Watson Watson is with us again to solve all
00:01:02 --> 00:01:03 these little riddles.
00:01:03 --> 00:01:06 Professor Fred Watson: Hello, Fred Watson. Hello Andrew. Nice to, um, help you solve the
00:01:06 --> 00:01:06 riddles.
00:01:08 --> 00:01:10 Andrew Dunkley: Uh, I don't know anything.
00:01:11 --> 00:01:12 That's why I bring you along.
00:01:12 --> 00:01:14 Professor Fred Watson: Oh, good. Well, I'm about to be of assistant.
00:01:14 --> 00:01:17 Andrew Dunkley: Makes it so much more interesting when there's two people talking.
00:01:17 --> 00:01:20 Monologues are just so boring, don't you reckon?
00:01:23 --> 00:01:26 Unless it's a super interesting person like yourself.
00:01:26 --> 00:01:26 Right.
00:01:26 --> 00:01:29 Professor Fred Watson: No, I'm, I'm capable of boring the pants off people as,
00:01:29 --> 00:01:32 uh, people have assured me before. So that's
00:01:32 --> 00:01:33 all right.
00:01:34 --> 00:01:37 Andrew Dunkley: So we've got a lot to get through and uh,
00:01:37 --> 00:01:40 it's, it's even trickier this week because we do have a
00:01:40 --> 00:01:43 technical, uh, issue, which means you are
00:01:43 --> 00:01:44 going to have to lip ring.
00:01:46 --> 00:01:48 Professor Fred Watson: Okay. Uh,
00:01:49 --> 00:01:51 so. Right. I'll do my best.
00:01:51 --> 00:01:52 Andrew Dunkley: We'll see how that.
00:01:52 --> 00:01:55 Professor Fred Watson: I'm wondering where the lips are going to be. That's the only thing.
00:01:55 --> 00:01:58 Andrew Dunkley: Yes, yes. Well, the first set of lips come from
00:01:58 --> 00:02:00 Paul. Uh, so let's hear his question.
00:02:00 --> 00:02:03 Paul: G' day, Fred Watson, Andrew, Johnty,
00:02:03 --> 00:02:06 Heidi, whoever happens to be at the helm. Uh, this
00:02:06 --> 00:02:09 is Paul from Sunnybris, Vegas. Thanks, uh, for doing a
00:02:09 --> 00:02:10 great job as always.
00:02:10 --> 00:02:13 I have a quick question about surprise
00:02:13 --> 00:02:16 black holes. Um, Dr. Shamir
00:02:16 --> 00:02:17 put out a paper recently about
00:02:19 --> 00:02:22 his ideas regarding the fact that, uh,
00:02:22 --> 00:02:25 some galaxies are spinning one way and
00:02:25 --> 00:02:27 uh, a lot of them, most of them the other way.
00:02:28 --> 00:02:31 And another fellow chipped in, Nikodem Poplowski
00:02:31 --> 00:02:33 from New Haven, suggested that
00:02:33 --> 00:02:36 maybe that was because our universe was born inside a black
00:02:36 --> 00:02:39 hole. If that is true, how the heck
00:02:39 --> 00:02:42 did we get out? And if we
00:02:42 --> 00:02:45 didn't get out and we're still inside,
00:02:45 --> 00:02:48 then how is that possible given that, you know,
00:02:48 --> 00:02:50 anything that goes inside a black hole, uh,
00:02:51 --> 00:02:53 is spaghettified according to our current
00:02:53 --> 00:02:56 thinking and therefore incoherent. I mean I know
00:02:56 --> 00:02:59 I'm incoherent, but you know what I'm talking about. Talking about
00:02:59 --> 00:03:01 when it comes to ordinary baryonic matter.
00:03:02 --> 00:03:05 Uh, love to get your thoughts on this.
00:03:06 --> 00:03:09 Anyway, uh, keep up the good work and
00:03:09 --> 00:03:11 catch us later. Cheers.
00:03:11 --> 00:03:14 Andrew Dunkley: Thank you Paul and hope all is well in Brisbane. Paul
00:03:14 --> 00:03:17 is asking about the universe being born inside
00:03:17 --> 00:03:20 a black hole. How do we get out? And why
00:03:20 --> 00:03:23 don't we get spaghettified as a consequence
00:03:23 --> 00:03:25 of that? Amongst many other things.
00:03:26 --> 00:03:28 But uh, that was the basis of the question.
00:03:28 --> 00:03:31 Professor Fred Watson: So. Yes. So as you've already uh, mentioned, I
00:03:31 --> 00:03:34 didn't hear any of Paul's question there. Not at
00:03:34 --> 00:03:37 all. However, I did listen uh, to it yesterday. So
00:03:37 --> 00:03:40 I've got a bit of an idea of what Paul was suggesting. The
00:03:40 --> 00:03:42 fact that um, we have uh,
00:03:42 --> 00:03:45 new observations which uh, have
00:03:45 --> 00:03:48 been made with the James Webb Space Telescope,
00:03:49 --> 00:03:51 uh, that um, are
00:03:51 --> 00:03:54 intriguing in the sense that uh,
00:03:54 --> 00:03:57 these scientists, uh, and they
00:03:57 --> 00:04:00 are basically uh, mostly
00:04:00 --> 00:04:01 located at Kansas State University.
00:04:03 --> 00:04:06 Uh, the, the rotation of galaxies in the
00:04:06 --> 00:04:08 deep universe isn't random. Uh,
00:04:08 --> 00:04:11 you'd expect, you know, galaxies to
00:04:11 --> 00:04:13 be rotating in.
00:04:14 --> 00:04:17 They can only go one way or the other. But you would expect
00:04:17 --> 00:04:20 an equal balance of rotations.
00:04:21 --> 00:04:24 Uh, and uh, what find, uh, or what
00:04:24 --> 00:04:26 these scientists find at Kansas State
00:04:26 --> 00:04:29 University using the James Webb
00:04:30 --> 00:04:32 Space Telescope Advanced Deep Extra
00:04:32 --> 00:04:35 galactic survey or jades, um, what
00:04:35 --> 00:04:38 they find is out of 263
00:04:38 --> 00:04:40 galaxies, um, which
00:04:41 --> 00:04:44 you know, which give away their
00:04:44 --> 00:04:46 rotation because we know that spiral arms nearly always
00:04:46 --> 00:04:49 trail. There's at least one galaxy where the spiral arms are leading
00:04:50 --> 00:04:53 but most of them trail. And what they
00:04:53 --> 00:04:55 find is that out of these 263 galaxies,
00:04:56 --> 00:04:59 about two thirds of them are going clockwise
00:04:59 --> 00:05:02 and the rest are going anticlockwise. And that is an
00:05:02 --> 00:05:04 imbalance. That's a statistically significant
00:05:04 --> 00:05:07 imbalance, uh, that suggests that
00:05:07 --> 00:05:10 something's going on that we don't understand and
00:05:11 --> 00:05:13 that leads to the possibility
00:05:14 --> 00:05:16 that perhaps the universe itself
00:05:17 --> 00:05:19 is rotating. Um,
00:05:19 --> 00:05:22 and I've seen other um, papers
00:05:22 --> 00:05:25 um, on this topic that suggest that maybe the
00:05:25 --> 00:05:28 universe rotates once in every 500 billion years.
00:05:28 --> 00:05:30 That's one figure that I've seen
00:05:31 --> 00:05:33 now, um, a consequence of the
00:05:33 --> 00:05:36 rotating universe. And I think this is where Paul's
00:05:36 --> 00:05:39 question went. I'm trying to remember having heard it
00:05:39 --> 00:05:41 yesterday, uh, is that
00:05:42 --> 00:05:45 it lend some weight to the
00:05:45 --> 00:05:48 idea that the universe is
00:05:48 --> 00:05:51 inside a black hole. Uh, in other
00:05:51 --> 00:05:54 Words that there is an event horizon at some
00:05:54 --> 00:05:56 huge distance from where we are,
00:05:57 --> 00:05:59 uh, and we are all within this
00:05:59 --> 00:06:02 black hole. Um,
00:06:03 --> 00:06:05 what does that mean for observational
00:06:05 --> 00:06:08 cosmology? I suspect it's going to be very
00:06:08 --> 00:06:11 difficult for us to confirm
00:06:11 --> 00:06:13 that ever. Uh, and I
00:06:13 --> 00:06:16 think, um, you know, this is
00:06:16 --> 00:06:19 speculative research. It's important
00:06:19 --> 00:06:21 research because you, you, you want to know
00:06:21 --> 00:06:24 um, how some of these things interact. And I might just
00:06:24 --> 00:06:27 mention, and I think we've discussed this before, Andrew, on space
00:06:27 --> 00:06:30 nuts, that the idea of a rotating universe
00:06:30 --> 00:06:33 actually relieves some of the issues,
00:06:33 --> 00:06:36 uh, that we find uh, in observing the
00:06:36 --> 00:06:39 universe. One of them is the Hubble tension. And I know there's a question coming
00:06:39 --> 00:06:42 up about that. Um, so a rotating
00:06:42 --> 00:06:45 universe has certainly attractive possibilities, but
00:06:45 --> 00:06:47 we absolutely don't know whether it is a
00:06:47 --> 00:06:50 rotating universe and indeed whether that means that we're inside
00:06:50 --> 00:06:53 a black hole. Uh, so what I was going to say was the idea of a
00:06:53 --> 00:06:56 universe within a black hole is akin to the idea of
00:06:56 --> 00:06:59 multiverses. The idea that um,
00:06:59 --> 00:07:02 um, multiple universes exist and we
00:07:02 --> 00:07:04 are just one of them. I'm not really, I
00:07:04 --> 00:07:07 don't think giving a sensible answer to Paul's question,
00:07:07 --> 00:07:10 partly because I couldn't hear it. But I think he was basically
00:07:10 --> 00:07:13 asking, you know, what happens? How does it happen?
00:07:14 --> 00:07:16 Uh, how are we not being spaghettified? That's
00:07:16 --> 00:07:19 because, uh, I can tell you the answer to that. Uh,
00:07:20 --> 00:07:23 we're not in a region, um, of the black hole
00:07:23 --> 00:07:24 where the um,
00:07:26 --> 00:07:29 gravitational pull is
00:07:29 --> 00:07:32 changing very, very rapidly with space.
00:07:33 --> 00:07:36 And that's what makes a black hole spaghettify. You, you go
00:07:36 --> 00:07:39 from one point to another and your gravitational pull is very different.
00:07:39 --> 00:07:42 So your head feels a different gravity from your feet and you get
00:07:42 --> 00:07:45 spaghettified. We're not in a place where
00:07:45 --> 00:07:48 that would be happening if we were inside a black
00:07:48 --> 00:07:51 hole. But uh, you know, all bets are off because
00:07:51 --> 00:07:53 inside a black hole, uh, there might.
00:07:54 --> 00:07:56 We're in a different dimensional space. A black hole is a
00:07:56 --> 00:07:59 singularity. Are, ah, we in a singularity? A singularity is
00:07:59 --> 00:08:02 a point with no dimensions. Work that
00:08:02 --> 00:08:05 one out. So we'd have to be almost in a different
00:08:05 --> 00:08:07 dimensional space. So it's an interesting
00:08:07 --> 00:08:10 question, um, to which I don't
00:08:10 --> 00:08:13 think anybody knows the answer, but there are a few people who
00:08:13 --> 00:08:16 are probably thinking through it a lot more clearly than I am.
00:08:17 --> 00:08:20 Andrew Dunkley: Well, Paul mentioned uh, a physicist by the name of
00:08:20 --> 00:08:22 Nicodem, um, Poplaus,
00:08:22 --> 00:08:25 uh, he's one that's put this theory
00:08:25 --> 00:08:27 forward that um, our
00:08:28 --> 00:08:30 observable universe is not just a part of a
00:08:30 --> 00:08:33 larger universe, but is in fact the interior of a
00:08:33 --> 00:08:36 black hole within a larger context.
00:08:36 --> 00:08:38 Professor Fred Watson: Yes. So you've got extra dimensions somewhere out there
00:08:39 --> 00:08:42 within, uh, which we exist. Uh,
00:08:42 --> 00:08:45 that's right. It's, um, uh, you know, I,
00:08:45 --> 00:08:48 I, Yes, I remember, um, checking out the, the researchers
00:08:48 --> 00:08:51 that, uh, that Paul mentioned yesterday when I looked at it.
00:08:51 --> 00:08:53 Uh, it's interesting stuff. Yeah.
00:08:54 --> 00:08:56 Andrew Dunkley: What do you think, personally? I mean, is there any
00:08:56 --> 00:08:58 possibility that this could be
00:08:59 --> 00:09:00 real?
00:09:00 --> 00:09:03 Professor Fred Watson: Um, to me it's on the same level
00:09:03 --> 00:09:05 as does heaven exist? Uh, you know,
00:09:06 --> 00:09:09 it's questions to which we really can't
00:09:09 --> 00:09:12 find answers. We can theorise, we can
00:09:12 --> 00:09:15 conjecture, we can speculate, we can write equations
00:09:15 --> 00:09:18 down. And probably some of the equations do support the
00:09:18 --> 00:09:21 idea that we're within an event horizon. It
00:09:21 --> 00:09:23 goes back a very long way. It's not a new idea at all.
00:09:24 --> 00:09:27 Um, but, um, I mean, people have put new
00:09:27 --> 00:09:30 numbers on it, I think, and, um, new observations. I think
00:09:30 --> 00:09:33 we, we watch this space. Next time this question comes up,
00:09:33 --> 00:09:35 I might be able to hear it properly and might be able to give a more
00:09:35 --> 00:09:37 cogent answer.
00:09:38 --> 00:09:41 Andrew Dunkley: Yes, indeed. I'll be working on that technicality.
00:09:41 --> 00:09:43 Professor Fred Watson: I don't, I'm sure it's not your fault, Andrew. I know what these
00:09:43 --> 00:09:45 gremlins are like. We get them all the time.
00:09:46 --> 00:09:49 Andrew Dunkley: Yeah, I'll blame the equipment. Never ever, though.
00:09:49 --> 00:09:51 Professor Fred Watson: Never the place. New Z. No, that's true.
00:09:54 --> 00:09:57 Andrew Dunkley: Thank you, Paul. Hope we covered that adequately, as we strive
00:09:57 --> 00:09:58 to do here on Space Nuts.
00:10:03 --> 00:10:04 Professor Fred Watson: Space Nuts.
00:10:04 --> 00:10:06 Andrew Dunkley: Uh, our next question, Fred Watson, comes from
00:10:06 --> 00:10:09 Casey in Colorado. In fact, he has two.
00:10:10 --> 00:10:12 Could you please explain the new theory of
00:10:12 --> 00:10:15 gravity in simple terms? Does
00:10:15 --> 00:10:18 it, uh, have any merit? And could you, uh, please
00:10:18 --> 00:10:21 explain hubble tension and what it means for our
00:10:21 --> 00:10:22 understanding of the universe?
00:10:23 --> 00:10:26 Professor Fred Watson: Yes. Uh, so
00:10:26 --> 00:10:29 that's the answer. The answer is yes. Yes, I can.
00:10:31 --> 00:10:34 The new theory of gravity, which I like very much. Um,
00:10:34 --> 00:10:37 this comes from scientists in Finland, which is a
00:10:37 --> 00:10:38 place that I like very much as well.
00:10:39 --> 00:10:42 Um, and it's what they've done,
00:10:43 --> 00:10:45 you know, they've taken, um,
00:10:46 --> 00:10:49 a step forward. And I'm
00:10:49 --> 00:10:52 assuming this is the, uh, this is
00:10:52 --> 00:10:54 indeed the, um, the, uh,
00:10:54 --> 00:10:57 the, the new theory that case is speaking about,
00:10:57 --> 00:11:00 because we get nearly one every week, a new theory of
00:11:00 --> 00:11:03 gravity. But this is the latest one. Um,
00:11:03 --> 00:11:06 it's, uh, as I said, it's from, uh, it's
00:11:06 --> 00:11:09 from, uh, Finnish scientists, uh, at
00:11:09 --> 00:11:11 Aalto, uh, University. Um,
00:11:13 --> 00:11:15 so it's what they've done
00:11:16 --> 00:11:19 is what Einstein tried to do for the last, for
00:11:19 --> 00:11:21 30 years of his life. Uh, which
00:11:21 --> 00:11:24 is to unify quantum field
00:11:24 --> 00:11:26 theory and relativity.
00:11:27 --> 00:11:30 And uh, that's an issue because uh, they
00:11:30 --> 00:11:33 are incompatible at ah, the levels that we
00:11:33 --> 00:11:36 try and look at them now. Um,
00:11:36 --> 00:11:39 and so uh, to bring a
00:11:39 --> 00:11:41 quantum theory of gravity into being
00:11:42 --> 00:11:45 is a big step. So um, what do I
00:11:45 --> 00:11:47 mean by, by bringing a theory into being? Well
00:11:47 --> 00:11:50 we know that there are four fundamental
00:11:50 --> 00:11:53 forces in nature. Uh, the strong
00:11:53 --> 00:11:55 and weak nuclear forces,
00:11:55 --> 00:11:58 electromagnetism and gravity. And the
00:11:58 --> 00:12:01 first three of those have very,
00:12:01 --> 00:12:04 very well established and well uh,
00:12:04 --> 00:12:07 understood quantum theories. Um,
00:12:07 --> 00:12:10 for example, we know that electromagnetism is propagated
00:12:10 --> 00:12:12 by photons. We're talking about it all the time. So the
00:12:12 --> 00:12:15 suspicion is that gravity uh, is propagated by
00:12:15 --> 00:12:18 gravitons. But so far there's been no theory of what
00:12:18 --> 00:12:21 gravitons might be like. So what these scientists
00:12:21 --> 00:12:24 have done have developed a new
00:12:24 --> 00:12:26 theory, uh, a new quantum theory of gravity.
00:12:26 --> 00:12:29 Uh, and I'm actually going to once again ah, quote
00:12:29 --> 00:12:32 from phys.org, very uh, nice account of
00:12:32 --> 00:12:35 this, um, uh, which is
00:12:35 --> 00:12:38 actually, I think it is part of the press release from
00:12:38 --> 00:12:41 Aalto University in Finland. So I'm quoting
00:12:41 --> 00:12:43 the university. Um, researchers at
00:12:43 --> 00:12:46 Aalto University have developed a new theory, quantum theory of
00:12:46 --> 00:12:49 gravity, which describes gravity in a way that
00:12:49 --> 00:12:52 is compatible with the standard model of
00:12:52 --> 00:12:54 particle physics, opening the door to an improved
00:12:54 --> 00:12:56 understanding of how the universe began.
00:12:57 --> 00:13:00 While the world of uh, quant
00:13:00 --> 00:13:02 theoretical physics may seem remote from
00:13:02 --> 00:13:05 applicable tech, the findings are remarkable. Modern
00:13:05 --> 00:13:08 technology is built on such fundamental advances. For example the
00:13:08 --> 00:13:10 GPS in your smartphone works thanks to
00:13:10 --> 00:13:13 Einstein's theory of gravity. Uh, and then uh,
00:13:14 --> 00:13:17 the article goes on to describe the theory
00:13:17 --> 00:13:20 is published in uh, Research Reports on
00:13:20 --> 00:13:22 Progress in Physics. Um,
00:13:22 --> 00:13:25 and this is the quote that I wanted to make. This comes
00:13:25 --> 00:13:28 from the lead uh, author of the paper.
00:13:28 --> 00:13:30 Uh, and um,
00:13:31 --> 00:13:34 um, basically they um,
00:13:38 --> 00:13:41 they've got lovely Finnish names. That's why I'm stumbling. It's
00:13:41 --> 00:13:44 Mikko Partanen, uh, who's the um,
00:13:44 --> 00:13:47 lead author. Uh, and the quote
00:13:47 --> 00:13:49 is as follows.
00:13:50 --> 00:13:53 And this kind of puts it into perspective,
00:13:53 --> 00:13:56 if that's the big word. If this
00:13:56 --> 00:13:59 turns out to lead to a complete quantum
00:13:59 --> 00:14:02 field theory of gravity, then eventually it will give
00:14:02 --> 00:14:04 answers to the very difficult problems of understanding
00:14:05 --> 00:14:07 singularities in black hole and black holes
00:14:07 --> 00:14:10 and the Big Bang. A theory uh,
00:14:10 --> 00:14:13 that coherently describes all fundamental forces
00:14:13 --> 00:14:15 of nature is often called the Theory of Everything.
00:14:16 --> 00:14:19 Uh, some fundamental questions of physics still
00:14:19 --> 00:14:22 remain unanswered. For example, the present theories do not yet
00:14:22 --> 00:14:25 explain why there is more matter than antimatter in the observable
00:14:25 --> 00:14:28 universe. Uh, and what they've done is,
00:14:28 --> 00:14:31 um, they've developed something called a gauge theory. And gauge
00:14:31 --> 00:14:34 theories are a particular kind of theory about the way
00:14:34 --> 00:14:36 particles interact with each other through a field.
00:14:37 --> 00:14:39 Ah, like the Higgs field and the Higgs boson. Um,
00:14:40 --> 00:14:43 so, uh, it's basically a
00:14:43 --> 00:14:46 very nice a, ah, very nice account. I won't read
00:14:46 --> 00:14:49 any more because, you know, gauge theories got
00:14:49 --> 00:14:51 symmetries and things of that sort. Um,
00:14:52 --> 00:14:55 it's, um, a nice account.
00:14:55 --> 00:14:58 I recommend people have a look@the phys.org
00:14:59 --> 00:15:01 uh, paper. Uh, uh, sorry, the
00:15:01 --> 00:15:04 fizz.org article. Casey, I'd send you to that
00:15:04 --> 00:15:07 as well to have a look. It's a very nice account of, of what's
00:15:07 --> 00:15:10 happening. You may end up like me thinking I really
00:15:10 --> 00:15:12 need to know a bit more about gauge theory before I can understand
00:15:12 --> 00:15:15 this. Uh, but, uh, nevertheless,
00:15:15 --> 00:15:18 you'll get, um, a good idea of what's going on, I think.
00:15:19 --> 00:15:20 Andrew Dunkley: M. Okay.
00:15:20 --> 00:15:22 Now, Casey also wanted you to
00:15:23 --> 00:15:25 explain, if you could, Hubble tension.
00:15:25 --> 00:15:27 Professor Fred Watson: Yeah, that's an easier one. And, uh, as we've
00:15:27 --> 00:15:28 spoken about.
00:15:28 --> 00:15:29 Andrew Dunkley: That's good.
00:15:29 --> 00:15:32 Professor Fred Watson: As we've spoken about today, uh, that's one of
00:15:32 --> 00:15:34 the things we might get rid of. Yes, Hubble tension is a lot easier than
00:15:34 --> 00:15:37 gauge theory. Um, and what it amounts to is we've
00:15:37 --> 00:15:40 got two ways of calculating
00:15:40 --> 00:15:43 the current expansion of the universe.
00:15:44 --> 00:15:46 Uh, one is by looking at
00:15:47 --> 00:15:49 galaxies in our
00:15:49 --> 00:15:52 vicinity, uh, and looking at the rate at
00:15:52 --> 00:15:54 which they are speeding away from us.
00:15:55 --> 00:15:58 They're moving away from us faster as their distance
00:15:58 --> 00:16:00 increases. This is exactly the discovery that hubble made in
00:16:00 --> 00:16:03 1929. And, uh,
00:16:03 --> 00:16:06 gives us something we call the Hubble constant, which is
00:16:06 --> 00:16:09 just the rate of expansion of the universe. Today we call
00:16:09 --> 00:16:12 it, ah, h. Naught, um, Hubble
00:16:12 --> 00:16:15 zero, which is the expansion rate today.
00:16:16 --> 00:16:18 Now, you can also get an idea of that
00:16:18 --> 00:16:21 or a measurement of it from the cosmic microwave
00:16:21 --> 00:16:24 background radiation. And that, to recap, is
00:16:24 --> 00:16:27 the flash of the Big Bang. We're looking back so far
00:16:27 --> 00:16:30 in time. We're seeing back to a time 380 years after
00:16:30 --> 00:16:33 the Big Bang, when the universe was still opaque and glowing brightly.
00:16:34 --> 00:16:37 So we see this wall of radiation which is now in the
00:16:37 --> 00:16:38 microwave region of the spectrum,
00:16:39 --> 00:16:42 uh, and it's peppered with a pattern
00:16:42 --> 00:16:45 of warmer and cooler places,
00:16:45 --> 00:16:48 uh, and those, uh, zones
00:16:48 --> 00:16:51 of higher and lower temperature, and it's only by a tiny
00:16:51 --> 00:16:54 fraction, uh, they correspond to the
00:16:54 --> 00:16:57 structure in that fireball. Um,
00:16:57 --> 00:17:00 in fact, it's caused by sound waves moving through
00:17:00 --> 00:17:02 it, they're called baryonic acoustic oscillations.
00:17:03 --> 00:17:06 And we can, by measuring the properties of that
00:17:06 --> 00:17:08 peppering of warmer and cooler regions,
00:17:08 --> 00:17:11 we can actually work out what the
00:17:11 --> 00:17:14 expansion of the universe is today. And
00:17:14 --> 00:17:16 it turns out that the two figures are different,
00:17:17 --> 00:17:20 um, by something like 4
00:17:20 --> 00:17:22 or 5%. And that in
00:17:22 --> 00:17:25 modern terms is big enough to worry about. It's
00:17:25 --> 00:17:28 not just an error of measurement. Uh,
00:17:28 --> 00:17:31 these have got fairly tight limits on the
00:17:31 --> 00:17:34 uncertainties, but they're different. And that is the
00:17:34 --> 00:17:36 Hubble tension. Hm.
00:17:36 --> 00:17:38 Andrew Dunkley: But didn't they recently, recently
00:17:39 --> 00:17:42 release a paper that suggested that the variations
00:17:42 --> 00:17:45 are actually within a normal range? That this,
00:17:45 --> 00:17:48 this, these two
00:17:48 --> 00:17:51 figures that don't match are, ah, close
00:17:51 --> 00:17:51 enough?
00:17:51 --> 00:17:52 Professor Fred Watson: Well, yes.
00:17:52 --> 00:17:53 Andrew Dunkley: Didn't we talk?
00:17:53 --> 00:17:56 Professor Fred Watson: We did that. Um, some people have suggested that, that it is,
00:17:56 --> 00:17:58 that it is actually within the experimental
00:17:58 --> 00:18:01 uncertainty, but it's still seen as attention. They
00:18:01 --> 00:18:04 could, they should be nearer than what they are.
00:18:05 --> 00:18:08 Andrew Dunkley: Yeah, okay. Very, very interesting,
00:18:08 --> 00:18:10 Casey. Thanks for both your questions. And no, you haven't
00:18:10 --> 00:18:13 spammed us. Two questions doesn't equal spam.
00:18:14 --> 00:18:17 There's probably a definition somewhere online that says how many,
00:18:17 --> 00:18:19 how many emails become spam.
00:18:20 --> 00:18:23 You're well, well outside that tolerance. So no
00:18:23 --> 00:18:26 problem there. Uh, this is Space Nuts
00:18:26 --> 00:18:28 Q A edition with Andrew Dunkley and Professor
00:18:28 --> 00:18:29 Fred Watson Watson.
00:18:34 --> 00:18:37 Space Nuts. Okay, Fred Watson, let's uh, move
00:18:37 --> 00:18:40 on to our next question. It's an audio question so
00:18:40 --> 00:18:42 you won't be able to hear it, but it comes
00:18:43 --> 00:18:44 from Simon.
00:18:45 --> 00:18:47 Simon: Hi, it's uh, Simon from Vasey in
00:18:48 --> 00:18:50 New South Wales here. Uh, my question's around,
00:18:51 --> 00:18:53 uh, the search for Planet Nine,
00:18:55 --> 00:18:58 uh, other exoplanets. Ah, few have been found
00:18:58 --> 00:19:01 using radial velocity methods. Is
00:19:01 --> 00:19:03 that something we could do with the sun?
00:19:04 --> 00:19:07 Um, I guess Planet nine being so far
00:19:07 --> 00:19:09 out, probably wouldn't have much influence,
00:19:10 --> 00:19:13 but we would have so much data on the
00:19:13 --> 00:19:15 sun as well
00:19:16 --> 00:19:19 that it might be easy to suss out.
00:19:19 --> 00:19:21 Anyway, Ah, that's my question.
00:19:23 --> 00:19:26 Andrew Dunkley: Thank you, Simon. Good to hear from you. Hope all is
00:19:26 --> 00:19:29 well in Veyce in New South Wales. Uh, he's
00:19:29 --> 00:19:32 asking, in the search for Planet nine, um,
00:19:33 --> 00:19:35 we've used the radial velocity method, uh,
00:19:35 --> 00:19:38 in the past to find other objects. Could, uh,
00:19:38 --> 00:19:41 we use the sun in the search for
00:19:41 --> 00:19:42 Planet Nine?
00:19:42 --> 00:19:45 Professor Fred Watson: Yeah, and it's a great question. Uh, I'm
00:19:45 --> 00:19:48 very well posed, Simon. Uh, I did actually manage
00:19:48 --> 00:19:50 to hear that through my own, um, recording,
00:19:50 --> 00:19:53 which I found and listened back to. So I know what
00:19:53 --> 00:19:56 Simon asked. And
00:19:57 --> 00:20:00 what he's saying is that we know that when
00:20:00 --> 00:20:02 we look for exoplanets, planets around,
00:20:03 --> 00:20:06 uh, other stars. What we look for is the change in position
00:20:06 --> 00:20:09 of the star itself as it's pulled one way
00:20:09 --> 00:20:11 and another by the planet orbiting around it.
00:20:12 --> 00:20:14 And yes, indeed, the solar system,
00:20:15 --> 00:20:18 uh, has such an effect. So
00:20:18 --> 00:20:21 Jupiter principally is the main planet
00:20:21 --> 00:20:23 that's pulling the sun's centre
00:20:23 --> 00:20:26 one way or the other. Uh, but the other planets all
00:20:27 --> 00:20:30 intervene as well. And so what we
00:20:30 --> 00:20:33 have is something that's called the solar system's
00:20:33 --> 00:20:35 barycenter, the centre of mass
00:20:35 --> 00:20:38 of the solar system and that moves as the
00:20:38 --> 00:20:41 planets wander around. And,
00:20:42 --> 00:20:44 um, we've exactly as, um,
00:20:45 --> 00:20:48 Simon says, we've managed
00:20:48 --> 00:20:50 to work out the position of the
00:20:50 --> 00:20:53 barycenter very, very accurately,
00:20:53 --> 00:20:56 uh, partly because we know where the planets are and
00:20:56 --> 00:20:58 things of that sort of. Now,
00:20:59 --> 00:21:02 Simon's question is
00:21:02 --> 00:21:05 actually exactly the same as a
00:21:05 --> 00:21:08 question that I found on Stack Exchange Online.
00:21:08 --> 00:21:11 The question was, wow, can the paper
00:21:11 --> 00:21:14 narrowing the solar system's barycenter to within
00:21:14 --> 00:21:17 100 metres help find Planet Nine?
00:21:18 --> 00:21:21 Uh, so that's basically what Simon asked. And
00:21:21 --> 00:21:23 the bottom line, there's a long, long
00:21:24 --> 00:21:27 set of calculations here which I won't
00:21:27 --> 00:21:29 go through, but the answer is probably
00:21:29 --> 00:21:32 not. Um, uh, it's because
00:21:32 --> 00:21:35 the Planet
00:21:35 --> 00:21:37 nine's influence on the solar system's
00:21:37 --> 00:21:40 barycenter, it's helped by the fact that Planet nine's
00:21:40 --> 00:21:43 a long way away. Um, um, so it's got
00:21:43 --> 00:21:46 sort of leverage, uh, as it goes around.
00:21:46 --> 00:21:48 Um, um,
00:21:49 --> 00:21:51 the short answer is
00:21:52 --> 00:21:55 maybe we could do it, but we wouldn't be
00:21:55 --> 00:21:58 able to do it without hundreds, if not
00:21:58 --> 00:22:01 thousands of years of precise data. And
00:22:01 --> 00:22:04 that's because Planet nine is probably orbiting the
00:22:04 --> 00:22:07 sun on that kind of timescale. And
00:22:07 --> 00:22:10 so you don't see any, you know, what you'd be looking for
00:22:10 --> 00:22:13 is, um, changes in the position
00:22:13 --> 00:22:16 of the barycenter, which are not caused by the
00:22:16 --> 00:22:19 known planets. But it'll take you
00:22:19 --> 00:22:22 hundreds or thousands of years to see that because of
00:22:22 --> 00:22:24 the great distance that Planet nine is at.
00:22:25 --> 00:22:28 So the answer is probably not, but it's a great question
00:22:28 --> 00:22:31 and really nice thinking. I like Simon's thinking there.
00:22:32 --> 00:22:35 Andrew Dunkley: Yeah, yeah, it's quite astute. Uh, the
00:22:35 --> 00:22:38 other factor that comes into play here is
00:22:38 --> 00:22:41 the new theory that Planet nine doesn't
00:22:41 --> 00:22:43 exist because there's another planet even further
00:22:43 --> 00:22:46 out that, uh, has only
00:22:46 --> 00:22:49 just been sort of put into, um, a
00:22:49 --> 00:22:52 pager and open for discussion. So we only
00:22:52 --> 00:22:55 talked about that last week. So the search for
00:22:55 --> 00:22:58 Planet nine might be a forlorn hope anyway, uh,
00:22:58 --> 00:23:01 um, because it probably, according to the new
00:23:01 --> 00:23:03 theory that's correct.
00:23:03 --> 00:23:06 Professor Fred Watson: Yeah. Now, the new theory is based more on observations
00:23:06 --> 00:23:07 than theory because it's two
00:23:08 --> 00:23:11 observations separated by something like 30 years that seem to
00:23:11 --> 00:23:14 show something moving very slowly in the outer solar system.
00:23:15 --> 00:23:18 You can bet your life will do more observing of that over, uh,
00:23:19 --> 00:23:21 uh, coming decades. Uh, and
00:23:21 --> 00:23:24 maybe that will turn out to be what I think is being called Planet
00:23:24 --> 00:23:27 eight and a half at the moment, because nobody really knows whether it's
00:23:27 --> 00:23:30 there or not. But as you said, if that is
00:23:30 --> 00:23:33 real, it rules out Planet nine. The two can't exist
00:23:33 --> 00:23:33 together.
00:23:35 --> 00:23:37 Andrew Dunkley: Exactly right. All right, there you go, Simon.
00:23:37 --> 00:23:40 Um, we'll see where that, uh, ends up, but
00:23:40 --> 00:23:41 it might take a while.
00:23:42 --> 00:23:45 Uh, final question comes from Joe
00:23:45 --> 00:23:48 in Olala in Washington. I hope I pronounced that
00:23:48 --> 00:23:50 correctly. Is there an upper limit to how much
00:23:50 --> 00:23:53 Delta V, uh, that can be practically
00:23:53 --> 00:23:56 generated by gravitational assists? Is it possible
00:23:56 --> 00:23:59 to develop sufficient Delta V for
00:23:59 --> 00:24:02 timely interstellar travel by winding up a probe in
00:24:02 --> 00:24:05 our solar system before launching it, uh, to a
00:24:05 --> 00:24:08 nearby star? Uh, thanks for all that you do.
00:24:08 --> 00:24:11 Cheers, Joe. Now, Delta V, that is the
00:24:11 --> 00:24:13 impulse per unit of spacecraft mass,
00:24:14 --> 00:24:14 yes?
00:24:15 --> 00:24:17 Professor Fred Watson: Well, it's basically the change in velocity.
00:24:19 --> 00:24:22 Um, yes. And impulse is the, uh, that's the way people
00:24:22 --> 00:24:25 talk about these Delta V's in this, in the rocket
00:24:25 --> 00:24:28 industry. It's all rocket science. What is it
00:24:28 --> 00:24:31 anyway, Delta V, uh, I think in
00:24:31 --> 00:24:33 Joe's context here is how much
00:24:33 --> 00:24:36 velocity increase you can get from a
00:24:36 --> 00:24:38 gravity assist, from a, ah, slingshot.
00:24:39 --> 00:24:42 Uh, and the answer is probably no, um,
00:24:42 --> 00:24:45 in terms of trying to wind up, you know, the speed
00:24:45 --> 00:24:48 of things so that you, you know, you
00:24:48 --> 00:24:50 tell something out of the solar system at
00:24:51 --> 00:24:54 10th, uh, the speed of light or something like that.
00:24:54 --> 00:24:57 Um, the reading that I've done on this, and
00:24:57 --> 00:25:00 I did check it out seems, uh, to suggest,
00:25:01 --> 00:25:04 excuse me, that um, we are probably
00:25:05 --> 00:25:07 limited to,
00:25:08 --> 00:25:11 um, the sorts of velocities that we
00:25:11 --> 00:25:14 see among the planets of the solar
00:25:14 --> 00:25:16 system. Now remember, the Earth is orbiting
00:25:16 --> 00:25:19 the sun at 30 kilometres per second.
00:25:20 --> 00:25:23 Um, and, um, those velocities
00:25:23 --> 00:25:26 get less as you get farther away from the sun. And
00:25:26 --> 00:25:29 that's part of the equation with a slingsot, because what you're
00:25:29 --> 00:25:31 trying to do is steal some momentum from the planet and,
00:25:31 --> 00:25:34 and give it to the spacecraft. And so there are upper
00:25:34 --> 00:25:37 limits, uh, on, um, what sort of velocity
00:25:37 --> 00:25:40 change you can get. It depends on how close
00:25:40 --> 00:25:43 you go to the planet, depends whether the planet's got an atmosphere or
00:25:43 --> 00:25:46 not. It, uh, depends on the angle that you come in. Um,
00:25:46 --> 00:25:49 the figure that I've seen quoted As a maximum
00:25:49 --> 00:25:52 for Jupiter, which is the most effective planet for this sort
00:25:52 --> 00:25:55 of thing, being by far the most massive planet in the solar system,
00:25:55 --> 00:25:57 is a change of 40 kilometres per second.
00:25:58 --> 00:26:01 Um, now that's very good if you're
00:26:01 --> 00:26:04 you know, trying to get something out to the outer solar system,
00:26:04 --> 00:26:07 but it's not going to help you getting things
00:26:07 --> 00:26:10 to other planets. Especially when you think,
00:26:11 --> 00:26:14 you know, if you give uh, a planet,
00:26:14 --> 00:26:16 sorry a spacecraft, an impulse
00:26:17 --> 00:26:20 Delta V of 40 kilometres per second by interacting with
00:26:20 --> 00:26:23 Jupiter, you've got to then find
00:26:23 --> 00:26:26 another planet that's, that's going to give
00:26:26 --> 00:26:29 it even more. But the other planets are all moving slower than
00:26:29 --> 00:26:31 that so uh, the change in
00:26:31 --> 00:26:34 momentum is a lot harder to get. Uh,
00:26:34 --> 00:26:37 so I think the answer is it's a very nice idea. As
00:26:37 --> 00:26:40 Joe suggests, winding up by all these gravitational
00:26:40 --> 00:26:43 interactions, you can only do it within
00:26:43 --> 00:26:44 limits. You're not going to be able to get
00:26:45 --> 00:26:48 like 100 kilometres per second or something like that
00:26:48 --> 00:26:49 from doing that.
00:26:49 --> 00:26:52 Andrew Dunkley: Yeah, I suppose you could equate it to using
00:26:52 --> 00:26:55 a slingshot or a shanghai. There's only so much
00:26:55 --> 00:26:58 tension you can push, put in, into the, the rubber band,
00:26:58 --> 00:27:01 let's say to fire the rock. And you're not going to be able to
00:27:01 --> 00:27:03 fire the rock any faster than the
00:27:03 --> 00:27:06 maximum amount of storage the rubber band can hold.
00:27:06 --> 00:27:08 And I'm guessing it's the same.
00:27:09 --> 00:27:12 Professor Fred Watson: Yes, there's a, there's a limited amount of energy
00:27:12 --> 00:27:14 that you can get from, from a slingshot. That's right,
00:27:15 --> 00:27:17 yeah. Nice idea there.
00:27:17 --> 00:27:20 Andrew Dunkley: Although it's, it's been very effective as you
00:27:20 --> 00:27:23 said, for sending things to the outer solar system.
00:27:23 --> 00:27:25 The, the Voyager probes particularly
00:27:25 --> 00:27:28 uh, used um, the slingshot effect,
00:27:29 --> 00:27:32 um, several times to get to
00:27:32 --> 00:27:35 the outer solar system because they didn't have the fuel to do it.
00:27:36 --> 00:27:38 So they figured out through um,
00:27:39 --> 00:27:42 an alignment of the planets that they
00:27:42 --> 00:27:44 could get out there just by using
00:27:45 --> 00:27:48 the rotation of the planets or um,
00:27:48 --> 00:27:51 the process uh, that uh, uh,
00:27:51 --> 00:27:54 Joe's been talking about. So um, yeah it does
00:27:54 --> 00:27:57 work quite effectively for slower,
00:27:58 --> 00:28:00 slower speeds that uh, yeah,
00:28:00 --> 00:28:03 interstellar, probably beyond us in that
00:28:03 --> 00:28:04 regard.
00:28:04 --> 00:28:07 Professor Fred Watson: Yeah, probably the lasers and um,
00:28:07 --> 00:28:10 you know in a solar cell or a light sail might be a
00:28:10 --> 00:28:13 better bet. But even that beyond our technology
00:28:13 --> 00:28:13 at the moment.
00:28:16 --> 00:28:18 Andrew Dunkley: Um, probably won't be for long though. I think they'll develop
00:28:18 --> 00:28:21 that and get some spacecraft
00:28:21 --> 00:28:24 heading out towards the Alpha Centauri sector and
00:28:25 --> 00:28:28 um, anyway that remains to be seen. Uh,
00:28:28 --> 00:28:30 but that would still be a pretty slow mission in the scheme of things.
00:28:30 --> 00:28:33 But um, yeah, great question Joe,
00:28:33 --> 00:28:36 thanks for sending it in. And if you'd like to send us a
00:28:36 --> 00:28:39 question, uh, you can do that, uh, through
00:28:39 --> 00:28:41 our website, spacenutspodcast.com
00:28:41 --> 00:28:44 spacenuts IO. Click on the AMA
00:28:44 --> 00:28:47 link at the top and you can send us text and
00:28:47 --> 00:28:50 audio questions. And don't forget to tell us
00:28:50 --> 00:28:53 who you are and where you're from. We love to know that sort of stuff so that we
00:28:53 --> 00:28:55 can send the boys around. Or, uh, we could send
00:28:55 --> 00:28:58 Huw around because he can't be with us today, so he must be
00:28:58 --> 00:29:01 visiting one of you guys, um, with his, with his,
00:29:01 --> 00:29:04 um, you know, balaclava on, maybe.
00:29:04 --> 00:29:04 Yeah.
00:29:05 --> 00:29:08 Professor Fred Watson: Thank, um, you, Fred Watson, as always, a pleasure. Andrew, as
00:29:08 --> 00:29:10 always. Good to talk and uh, good to hear our
00:29:10 --> 00:29:12 listeners questions. It's.
00:29:12 --> 00:29:15 Andrew Dunkley: It is, it is. All right, well catch you again
00:29:15 --> 00:29:18 real soon. Professor Fred Watson Watson, astronomer at large, and from me,
00:29:18 --> 00:29:21 Andrew Dunkley. Thanks for your company. See you on the next
00:29:21 --> 00:29:23 episode of Space Nuts. Bye for now.
00:29:24 --> 00:29:26 Professor Fred Watson: You've been listening to the Space Nuts.
00:29:26 --> 00:29:29 Andrew Dunkley: Podcast, available at
00:29:29 --> 00:29:31 Apple Podcasts, Spotify,
00:29:32 --> 00:29:34 iHeartRadio or your favourite podcast
00:29:34 --> 00:29:36 player. You can also stream on
00:29:36 --> 00:29:39 demand@bytes.com. um, this has been another
00:29:39 --> 00:29:41 quality podcast production from Bytes.
00:29:42 --> 00:29:42 Professor Fred Watson: Com.