Black Holes, Gravity Theories & the Quest for Planet Nine

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Andrew Dunkley: Hi there. Thanks for joining us. This is a Q and A edition of

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Space Nuts. My name is Andrew Dunkley. It's

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good to have your company. Uh, today, uh, we

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will be hearing questions about, uh,

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the universe being inside a black hole. In fact, I

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think they're suggesting it was born in a black hole and

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is stuck in there. And how do we get out?

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We'll also be looking at a new gravity theory. Uh,

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theory Hubble tension. Not

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surprisingly, questions about planet nine with the

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most recent announcement of something being out there that's not

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planet nine. And, um,

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getting gravity assistance to Max

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Delta V. Those are all the questions

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coming up on this episode of space nuts.

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Voice Over Guy: 15 seconds. Guidance is internal.

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10, 9, ignition

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sequence time. Uh, space nuts. 5, 4, 3,

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2. 1. 2, 3, 4, 5, 5, 4,

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3, 2, 1. Space nuts. Astronauts

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report it feels good.

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Andrew Dunkley: And Fred Watson Watson is with us again to solve all

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these little riddles.

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Professor Fred Watson: Hello, Fred Watson. Hello Andrew. Nice to, um, help you solve the

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riddles.

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Andrew Dunkley: Uh, I don't know anything.

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That's why I bring you along.

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Professor Fred Watson: Oh, good. Well, I'm about to be of assistant.

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Andrew Dunkley: Makes it so much more interesting when there's two people talking.

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Monologues are just so boring, don't you reckon?

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Unless it's a super interesting person like yourself.

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Right.

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Professor Fred Watson: No, I'm, I'm capable of boring the pants off people as,

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uh, people have assured me before. So that's

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all right.

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Andrew Dunkley: So we've got a lot to get through and uh,

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it's, it's even trickier this week because we do have a

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technical, uh, issue, which means you are

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going to have to lip ring.

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Professor Fred Watson: Okay. Uh,

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so. Right. I'll do my best.

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Andrew Dunkley: We'll see how that.

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Professor Fred Watson: I'm wondering where the lips are going to be. That's the only thing.

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Andrew Dunkley: Yes, yes. Well, the first set of lips come from

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Paul. Uh, so let's hear his question.

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Paul: G' day, Fred Watson, Andrew, Johnty,

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Heidi, whoever happens to be at the helm. Uh, this

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is Paul from Sunnybris, Vegas. Thanks, uh, for doing a

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great job as always.

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I have a quick question about surprise

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black holes. Um, Dr. Shamir

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put out a paper recently about

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his ideas regarding the fact that, uh,

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some galaxies are spinning one way and

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uh, a lot of them, most of them the other way.

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And another fellow chipped in, Nikodem Poplowski

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from New Haven, suggested that

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maybe that was because our universe was born inside a black

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hole. If that is true, how the heck

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did we get out? And if we

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didn't get out and we're still inside,

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then how is that possible given that, you know,

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anything that goes inside a black hole, uh,

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is spaghettified according to our current

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thinking and therefore incoherent. I mean I know

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I'm incoherent, but you know what I'm talking about. Talking about

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when it comes to ordinary baryonic matter.

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Uh, love to get your thoughts on this.

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Anyway, uh, keep up the good work and

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catch us later. Cheers.

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Andrew Dunkley: Thank you Paul and hope all is well in Brisbane. Paul

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is asking about the universe being born inside

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a black hole. How do we get out? And why

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don't we get spaghettified as a consequence

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of that? Amongst many other things.

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But uh, that was the basis of the question.

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Professor Fred Watson: So. Yes. So as you've already uh, mentioned, I

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didn't hear any of Paul's question there. Not at

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all. However, I did listen uh, to it yesterday. So

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I've got a bit of an idea of what Paul was suggesting. The

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fact that um, we have uh,

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new observations which uh, have

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been made with the James Webb Space Telescope,

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uh, that um, are

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intriguing in the sense that uh,

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these scientists, uh, and they

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are basically uh, mostly

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located at Kansas State University.

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Uh, the, the rotation of galaxies in the

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deep universe isn't random. Uh,

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you'd expect, you know, galaxies to

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be rotating in.

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They can only go one way or the other. But you would expect

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an equal balance of rotations.

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Uh, and uh, what find, uh, or what

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these scientists find at Kansas State

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University using the James Webb

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Space Telescope Advanced Deep Extra

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galactic survey or jades, um, what

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they find is out of 263

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galaxies, um, which

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you know, which give away their

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rotation because we know that spiral arms nearly always

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trail. There's at least one galaxy where the spiral arms are leading

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but most of them trail. And what they

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find is that out of these 263 galaxies,

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about two thirds of them are going clockwise

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and the rest are going anticlockwise. And that is an

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imbalance. That's a statistically significant

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imbalance, uh, that suggests that

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something's going on that we don't understand and

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that leads to the possibility

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that perhaps the universe itself

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is rotating. Um,

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and I've seen other um, papers

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um, on this topic that suggest that maybe the

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universe rotates once in every 500 billion years.

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That's one figure that I've seen

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now, um, a consequence of the

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rotating universe. And I think this is where Paul's

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question went. I'm trying to remember having heard it

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yesterday, uh, is that

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it lend some weight to the

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idea that the universe is

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inside a black hole. Uh, in other

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Words that there is an event horizon at some

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huge distance from where we are,

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uh, and we are all within this

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black hole. Um,

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what does that mean for observational

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cosmology? I suspect it's going to be very

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difficult for us to confirm

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that ever. Uh, and I

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think, um, you know, this is

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speculative research. It's important

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research because you, you, you want to know

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um, how some of these things interact. And I might just

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mention, and I think we've discussed this before, Andrew, on space

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nuts, that the idea of a rotating universe

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actually relieves some of the issues,

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uh, that we find uh, in observing the

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universe. One of them is the Hubble tension. And I know there's a question coming

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up about that. Um, so a rotating

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universe has certainly attractive possibilities, but

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we absolutely don't know whether it is a

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rotating universe and indeed whether that means that we're inside

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a black hole. Uh, so what I was going to say was the idea of a

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universe within a black hole is akin to the idea of

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multiverses. The idea that um,

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um, multiple universes exist and we

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are just one of them. I'm not really, I

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don't think giving a sensible answer to Paul's question,

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partly because I couldn't hear it. But I think he was basically

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asking, you know, what happens? How does it happen?

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Uh, how are we not being spaghettified? That's

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because, uh, I can tell you the answer to that. Uh,

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we're not in a region, um, of the black hole

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where the um,

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gravitational pull is

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changing very, very rapidly with space.

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And that's what makes a black hole spaghettify. You, you go

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from one point to another and your gravitational pull is very different.

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So your head feels a different gravity from your feet and you get

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spaghettified. We're not in a place where

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that would be happening if we were inside a black

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hole. But uh, you know, all bets are off because

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inside a black hole, uh, there might.

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We're in a different dimensional space. A black hole is a

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singularity. Are, ah, we in a singularity? A singularity is

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a point with no dimensions. Work that

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one out. So we'd have to be almost in a different

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dimensional space. So it's an interesting

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question, um, to which I don't

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think anybody knows the answer, but there are a few people who

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are probably thinking through it a lot more clearly than I am.

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Andrew Dunkley: Well, Paul mentioned uh, a physicist by the name of

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Nicodem, um, Poplaus,

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uh, he's one that's put this theory

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forward that um, our

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observable universe is not just a part of a

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larger universe, but is in fact the interior of a

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black hole within a larger context.

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Professor Fred Watson: Yes. So you've got extra dimensions somewhere out there

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within, uh, which we exist. Uh,

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that's right. It's, um, uh, you know, I,

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I, Yes, I remember, um, checking out the, the researchers

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that, uh, that Paul mentioned yesterday when I looked at it.

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Uh, it's interesting stuff. Yeah.

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Andrew Dunkley: What do you think, personally? I mean, is there any

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possibility that this could be

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real?

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Professor Fred Watson: Um, to me it's on the same level

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as does heaven exist? Uh, you know,

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it's questions to which we really can't

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find answers. We can theorise, we can

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conjecture, we can speculate, we can write equations

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down. And probably some of the equations do support the

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idea that we're within an event horizon. It

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goes back a very long way. It's not a new idea at all.

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Um, but, um, I mean, people have put new

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numbers on it, I think, and, um, new observations. I think

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we, we watch this space. Next time this question comes up,

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I might be able to hear it properly and might be able to give a more

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cogent answer.

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Andrew Dunkley: Yes, indeed. I'll be working on that technicality.

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Professor Fred Watson: I don't, I'm sure it's not your fault, Andrew. I know what these

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gremlins are like. We get them all the time.

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Andrew Dunkley: Yeah, I'll blame the equipment. Never ever, though.

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Professor Fred Watson: Never the place. New Z. No, that's true.

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Andrew Dunkley: Thank you, Paul. Hope we covered that adequately, as we strive

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to do here on Space Nuts.

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Professor Fred Watson: Space Nuts.

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Andrew Dunkley: Uh, our next question, Fred Watson, comes from

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Casey in Colorado. In fact, he has two.

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Could you please explain the new theory of

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gravity in simple terms? Does

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it, uh, have any merit? And could you, uh, please

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explain hubble tension and what it means for our

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understanding of the universe?

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Professor Fred Watson: Yes. Uh, so

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that's the answer. The answer is yes. Yes, I can.

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The new theory of gravity, which I like very much. Um,

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this comes from scientists in Finland, which is a

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place that I like very much as well.

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Um, and it's what they've done,

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you know, they've taken, um,

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a step forward. And I'm

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assuming this is the, uh, this is

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indeed the, um, the, uh,

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the, the new theory that case is speaking about,

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because we get nearly one every week, a new theory of

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gravity. But this is the latest one. Um,

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it's, uh, as I said, it's from, uh, it's

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from, uh, Finnish scientists, uh, at

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Aalto, uh, University. Um,

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so it's what they've done

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is what Einstein tried to do for the last, for

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30 years of his life. Uh, which

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is to unify quantum field

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theory and relativity.

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And uh, that's an issue because uh, they

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are incompatible at ah, the levels that we

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try and look at them now. Um,

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and so uh, to bring a

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quantum theory of gravity into being

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is a big step. So um, what do I

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mean by, by bringing a theory into being? Well

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we know that there are four fundamental

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forces in nature. Uh, the strong

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and weak nuclear forces,

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electromagnetism and gravity. And the

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first three of those have very,

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very well established and well uh,

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understood quantum theories. Um,

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for example, we know that electromagnetism is propagated

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by photons. We're talking about it all the time. So the

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suspicion is that gravity uh, is propagated by

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gravitons. But so far there's been no theory of what

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gravitons might be like. So what these scientists

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have done have developed a new

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theory, uh, a new quantum theory of gravity.

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Uh, and I'm actually going to once again ah, quote

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from phys.org, very uh, nice account of

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this, um, uh, which is

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actually, I think it is part of the press release from

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Aalto University in Finland. So I'm quoting

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the university. Um, researchers at

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Aalto University have developed a new theory, quantum theory of

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gravity, which describes gravity in a way that

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is compatible with the standard model of

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particle physics, opening the door to an improved

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understanding of how the universe began.

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While the world of uh, quant

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theoretical physics may seem remote from

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applicable tech, the findings are remarkable. Modern

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technology is built on such fundamental advances. For example the

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GPS in your smartphone works thanks to

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Einstein's theory of gravity. Uh, and then uh,

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the article goes on to describe the theory

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is published in uh, Research Reports on

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Progress in Physics. Um,

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and this is the quote that I wanted to make. This comes

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from the lead uh, author of the paper.

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Uh, and um,

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um, basically they um,

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they've got lovely Finnish names. That's why I'm stumbling. It's

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Mikko Partanen, uh, who's the um,

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lead author. Uh, and the quote

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is as follows.

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And this kind of puts it into perspective,

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if that's the big word. If this

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turns out to lead to a complete quantum

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field theory of gravity, then eventually it will give

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answers to the very difficult problems of understanding

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singularities in black hole and black holes

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and the Big Bang. A theory uh,

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that coherently describes all fundamental forces

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of nature is often called the Theory of Everything.

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Uh, some fundamental questions of physics still

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remain unanswered. For example, the present theories do not yet

300
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explain why there is more matter than antimatter in the observable

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universe. Uh, and what they've done is,

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um, they've developed something called a gauge theory. And gauge

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theories are a particular kind of theory about the way

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particles interact with each other through a field.

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Ah, like the Higgs field and the Higgs boson. Um,

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so, uh, it's basically a

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very nice a, ah, very nice account. I won't read

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any more because, you know, gauge theories got

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symmetries and things of that sort. Um,

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it's, um, a nice account.

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I recommend people have a look@the phys.org

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uh, paper. Uh, uh, sorry, the

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fizz.org article. Casey, I'd send you to that

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as well to have a look. It's a very nice account of, of what's

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happening. You may end up like me thinking I really

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need to know a bit more about gauge theory before I can understand

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this. Uh, but, uh, nevertheless,

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you'll get, um, a good idea of what's going on, I think.

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Andrew Dunkley: M. Okay.

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Now, Casey also wanted you to

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explain, if you could, Hubble tension.

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Professor Fred Watson: Yeah, that's an easier one. And, uh, as we've

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spoken about.

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Andrew Dunkley: That's good.

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Professor Fred Watson: As we've spoken about today, uh, that's one of

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the things we might get rid of. Yes, Hubble tension is a lot easier than

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gauge theory. Um, and what it amounts to is we've

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got two ways of calculating

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the current expansion of the universe.

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Uh, one is by looking at

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galaxies in our

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vicinity, uh, and looking at the rate at

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which they are speeding away from us.

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They're moving away from us faster as their distance

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increases. This is exactly the discovery that hubble made in

336
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1929. And, uh,

337
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gives us something we call the Hubble constant, which is

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just the rate of expansion of the universe. Today we call

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it, ah, h. Naught, um, Hubble

340
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zero, which is the expansion rate today.

341
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Now, you can also get an idea of that

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or a measurement of it from the cosmic microwave

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background radiation. And that, to recap, is

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the flash of the Big Bang. We're looking back so far

345
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in time. We're seeing back to a time 380,000 years after

346
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the Big Bang, when the universe was still opaque and glowing brightly.

347
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So we see this wall of radiation which is now in the

348
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microwave region of the spectrum,

349
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uh, and it's peppered with a pattern

350
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of warmer and cooler places,

351
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uh, and those, uh, zones

352
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of higher and lower temperature, and it's only by a tiny

353
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fraction, uh, they correspond to the

354
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structure in that fireball. Um,

355
00:16:57.360 --> 00:17:00.360
in fact, it's caused by sound waves moving through

356
00:17:00.360 --> 00:17:02.800
it, they're called baryonic acoustic oscillations.

357
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And we can, by measuring the properties of that

358
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peppering of warmer and cooler regions,

359
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we can actually work out what the

360
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expansion of the universe is today. And

361
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it turns out that the two figures are different,

362
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um, by something like 4

363
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or 5%. And that in

364
00:17:22.870 --> 00:17:25.870
modern terms is big enough to worry about. It's

365
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not just an error of measurement. Uh,

366
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these have got fairly tight limits on the

367
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uncertainties, but they're different. And that is the

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Hubble tension. Hm.

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Andrew Dunkley: But didn't they recently, recently

370
00:17:39.710 --> 00:17:42.670
release a paper that suggested that the variations

371
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are actually within a normal range? That this,

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this, these two

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00:17:48.750 --> 00:17:51.430
figures that don't match are, ah, close

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00:17:51.430 --> 00:17:51.790
enough?

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Professor Fred Watson: Well, yes.

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Andrew Dunkley: Didn't we talk?

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00:17:53.230 --> 00:17:56.230
Professor Fred Watson: We did that. Um, some people have suggested that, that it is,

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that it is actually within the experimental

379
00:17:58.870 --> 00:18:01.720
uncertainty, but it's still seen as attention. They

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00:18:01.720 --> 00:18:04.000
could, they should be nearer than what they are.

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Andrew Dunkley: Yeah, okay. Very, very interesting,

382
00:18:08.000 --> 00:18:10.600
Casey. Thanks for both your questions. And no, you haven't

383
00:18:10.600 --> 00:18:13.120
spammed us. Two questions doesn't equal spam.

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00:18:14.560 --> 00:18:17.440
There's probably a definition somewhere online that says how many,

385
00:18:17.520 --> 00:18:19.200
how many emails become spam.

386
00:18:20.160 --> 00:18:23.160
You're well, well outside that tolerance. So no

387
00:18:23.160 --> 00:18:26.000
problem there. Uh, this is Space Nuts

388
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Q A edition with Andrew Dunkley and Professor

389
00:18:28.680 --> 00:18:29.680
Fred Watson Watson.

390
00:18:34.380 --> 00:18:37.260
Space Nuts. Okay, Fred Watson, let's uh, move

391
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on to our next question. It's an audio question so

392
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you won't be able to hear it, but it comes

393
00:18:43.180 --> 00:18:44.700
from Simon.

394
00:18:45.180 --> 00:18:47.900
Simon: Hi, it's uh, Simon from Vasey in

395
00:18:48.220 --> 00:18:50.940
New South Wales here. Uh, my question's around,

396
00:18:51.830 --> 00:18:53.580
uh, the search for Planet Nine,

397
00:18:55.250 --> 00:18:58.220
uh, other exoplanets. Ah, few have been found

398
00:18:58.220 --> 00:19:01.080
using radial velocity methods. Is

399
00:19:01.080 --> 00:19:03.960
that something we could do with the sun?

400
00:19:04.270 --> 00:19:07.240
Um, I guess Planet nine being so far

401
00:19:07.240 --> 00:19:09.880
out, probably wouldn't have much influence,

402
00:19:10.920 --> 00:19:13.800
but we would have so much data on the

403
00:19:13.800 --> 00:19:15.000
sun as well

404
00:19:16.680 --> 00:19:19.000
that it might be easy to suss out.

405
00:19:19.320 --> 00:19:21.000
Anyway, Ah, that's my question.

406
00:19:23.800 --> 00:19:26.760
Andrew Dunkley: Thank you, Simon. Good to hear from you. Hope all is

407
00:19:26.760 --> 00:19:29.600
well in Veyce in New South Wales. Uh, he's

408
00:19:29.600 --> 00:19:32.560
asking, in the search for Planet nine, um,

409
00:19:33.060 --> 00:19:35.770
we've used the radial velocity method, uh,

410
00:19:35.860 --> 00:19:38.390
in the past to find other objects. Could, uh,

411
00:19:38.660 --> 00:19:41.660
we use the sun in the search for

412
00:19:41.660 --> 00:19:42.420
Planet Nine?

413
00:19:42.500 --> 00:19:45.220
Professor Fred Watson: Yeah, and it's a great question. Uh, I'm

414
00:19:45.220 --> 00:19:48.019
very well posed, Simon. Uh, I did actually manage

415
00:19:48.019 --> 00:19:50.900
to hear that through my own, um, recording,

416
00:19:50.900 --> 00:19:53.860
which I found and listened back to. So I know what

417
00:19:53.860 --> 00:19:56.660
Simon asked. And

418
00:19:57.300 --> 00:20:00.260
what he's saying is that we know that when

419
00:20:00.260 --> 00:20:02.940
we look for exoplanets, planets around,

420
00:20:03.210 --> 00:20:06.140
uh, other stars. What we look for is the change in position

421
00:20:06.700 --> 00:20:09.580
of the star itself as it's pulled one way

422
00:20:09.580 --> 00:20:11.820
and another by the planet orbiting around it.

423
00:20:12.540 --> 00:20:14.780
And yes, indeed, the solar system,

424
00:20:15.670 --> 00:20:18.340
uh, has such an effect. So

425
00:20:18.340 --> 00:20:21.100
Jupiter principally is the main planet

426
00:20:21.100 --> 00:20:23.980
that's pulling the sun's centre

427
00:20:23.980 --> 00:20:26.940
one way or the other. Uh, but the other planets all

428
00:20:27.020 --> 00:20:30.010
intervene as well. And so what we

429
00:20:30.490 --> 00:20:33.250
have is something that's called the solar system's

430
00:20:33.250 --> 00:20:35.370
barycenter, the centre of mass

431
00:20:35.930 --> 00:20:38.850
of the solar system and that moves as the

432
00:20:38.850 --> 00:20:41.690
planets wander around. And,

433
00:20:42.160 --> 00:20:44.790
um, we've exactly as, um,

434
00:20:45.210 --> 00:20:48.010
Simon says, we've managed

435
00:20:48.010 --> 00:20:50.690
to work out the position of the

436
00:20:50.690 --> 00:20:53.130
barycenter very, very accurately,

437
00:20:53.780 --> 00:20:56.610
uh, partly because we know where the planets are and

438
00:20:56.610 --> 00:20:58.720
things of that sort of. Now,

439
00:20:59.600 --> 00:21:02.520
Simon's question is

440
00:21:02.520 --> 00:21:05.480
actually exactly the same as a

441
00:21:05.480 --> 00:21:08.240
question that I found on Stack Exchange Online.

442
00:21:08.640 --> 00:21:11.360
The question was, wow, can the paper

443
00:21:11.520 --> 00:21:14.520
narrowing the solar system's barycenter to within

444
00:21:14.520 --> 00:21:17.440
100 metres help find Planet Nine?

445
00:21:18.460 --> 00:21:21.240
Uh, so that's basically what Simon asked. And

446
00:21:21.240 --> 00:21:23.920
the bottom line, there's a long, long

447
00:21:24.080 --> 00:21:27.000
set of calculations here which I won't

448
00:21:27.000 --> 00:21:29.800
go through, but the answer is probably

449
00:21:29.800 --> 00:21:32.120
not. Um, uh, it's because

450
00:21:32.440 --> 00:21:35.400
the Planet

451
00:21:35.400 --> 00:21:37.680
nine's influence on the solar system's

452
00:21:37.680 --> 00:21:40.680
barycenter, it's helped by the fact that Planet nine's

453
00:21:40.680 --> 00:21:43.679
a long way away. Um, um, so it's got

454
00:21:43.679 --> 00:21:46.120
sort of leverage, uh, as it goes around.

455
00:21:46.950 --> 00:21:48.070
Um, um,

456
00:21:49.800 --> 00:21:51.480
the short answer is

457
00:21:52.920 --> 00:21:55.910
maybe we could do it, but we wouldn't be

458
00:21:55.910 --> 00:21:58.430
able to do it without hundreds, if not

459
00:21:58.590 --> 00:22:01.550
thousands of years of precise data. And

460
00:22:01.550 --> 00:22:04.470
that's because Planet nine is probably orbiting the

461
00:22:04.470 --> 00:22:07.470
sun on that kind of timescale. And

462
00:22:07.470 --> 00:22:10.270
so you don't see any, you know, what you'd be looking for

463
00:22:10.670 --> 00:22:13.590
is, um, changes in the position

464
00:22:13.590 --> 00:22:16.390
of the barycenter, which are not caused by the

465
00:22:16.390 --> 00:22:19.150
known planets. But it'll take you

466
00:22:19.310 --> 00:22:22.240
hundreds or thousands of years to see that because of

467
00:22:22.800 --> 00:22:24.960
the great distance that Planet nine is at.

468
00:22:25.760 --> 00:22:28.680
So the answer is probably not, but it's a great question

469
00:22:28.680 --> 00:22:31.600
and really nice thinking. I like Simon's thinking there.

470
00:22:32.240 --> 00:22:35.040
Andrew Dunkley: Yeah, yeah, it's quite astute. Uh, the

471
00:22:35.600 --> 00:22:38.240
other factor that comes into play here is

472
00:22:38.400 --> 00:22:41.080
the new theory that Planet nine doesn't

473
00:22:41.080 --> 00:22:43.880
exist because there's another planet even further

474
00:22:43.880 --> 00:22:46.760
out that, uh, has only

475
00:22:46.760 --> 00:22:49.560
just been sort of put into, um, a

476
00:22:49.560 --> 00:22:52.360
pager and open for discussion. So we only

477
00:22:52.360 --> 00:22:55.200
talked about that last week. So the search for

478
00:22:55.200 --> 00:22:58.150
Planet nine might be a forlorn hope anyway, uh,

479
00:22:58.720 --> 00:23:01.560
um, because it probably, according to the new

480
00:23:01.560 --> 00:23:03.000
theory that's correct.

481
00:23:03.000 --> 00:23:06.000
Professor Fred Watson: Yeah. Now, the new theory is based more on observations

482
00:23:06.000 --> 00:23:07.960
than theory because it's two

483
00:23:08.680 --> 00:23:11.640
observations separated by something like 30 years that seem to

484
00:23:11.640 --> 00:23:14.200
show something moving very slowly in the outer solar system.

485
00:23:15.710 --> 00:23:18.370
You can bet your life will do more observing of that over, uh,

486
00:23:19.280 --> 00:23:21.870
uh, coming decades. Uh, and

487
00:23:21.870 --> 00:23:24.790
maybe that will turn out to be what I think is being called Planet

488
00:23:24.790 --> 00:23:27.750
eight and a half at the moment, because nobody really knows whether it's

489
00:23:27.750 --> 00:23:30.589
there or not. But as you said, if that is

490
00:23:30.589 --> 00:23:33.550
real, it rules out Planet nine. The two can't exist

491
00:23:33.550 --> 00:23:33.950
together.

492
00:23:35.310 --> 00:23:37.910
Andrew Dunkley: Exactly right. All right, there you go, Simon.

493
00:23:37.910 --> 00:23:40.830
Um, we'll see where that, uh, ends up, but

494
00:23:40.830 --> 00:23:41.790
it might take a while.

495
00:23:42.450 --> 00:23:45.230
Uh, final question comes from Joe

496
00:23:45.230 --> 00:23:48.130
in Olala in Washington. I hope I pronounced that

497
00:23:48.130 --> 00:23:50.930
correctly. Is there an upper limit to how much

498
00:23:50.930 --> 00:23:53.730
Delta V, uh, that can be practically

499
00:23:53.730 --> 00:23:56.730
generated by gravitational assists? Is it possible

500
00:23:56.810 --> 00:23:59.770
to develop sufficient Delta V for

501
00:23:59.770 --> 00:24:02.690
timely interstellar travel by winding up a probe in

502
00:24:02.690 --> 00:24:05.490
our solar system before launching it, uh, to a

503
00:24:05.490 --> 00:24:08.450
nearby star? Uh, thanks for all that you do.

504
00:24:08.450 --> 00:24:11.130
Cheers, Joe. Now, Delta V, that is the

505
00:24:11.130 --> 00:24:13.920
impulse per unit of spacecraft mass,

506
00:24:14.160 --> 00:24:14.640
yes?

507
00:24:15.520 --> 00:24:17.840
Professor Fred Watson: Well, it's basically the change in velocity.

508
00:24:19.530 --> 00:24:22.400
Um, yes. And impulse is the, uh, that's the way people

509
00:24:22.960 --> 00:24:25.680
talk about these Delta V's in this, in the rocket

510
00:24:25.680 --> 00:24:28.560
industry. It's all rocket science. What is it

511
00:24:28.560 --> 00:24:31.080
anyway, Delta V, uh, I think in

512
00:24:31.080 --> 00:24:33.880
Joe's context here is how much

513
00:24:33.880 --> 00:24:36.880
velocity increase you can get from a

514
00:24:36.960 --> 00:24:38.960
gravity assist, from a, ah, slingshot.

515
00:24:39.790 --> 00:24:42.280
Uh, and the answer is probably no, um,

516
00:24:42.610 --> 00:24:45.530
in terms of trying to wind up, you know, the speed

517
00:24:45.530 --> 00:24:48.290
of things so that you, you know, you

518
00:24:48.290 --> 00:24:50.450
tell something out of the solar system at

519
00:24:51.890 --> 00:24:54.050
10th, uh, the speed of light or something like that.

520
00:24:54.710 --> 00:24:57.650
Um, the reading that I've done on this, and

521
00:24:57.650 --> 00:25:00.290
I did check it out seems, uh, to suggest,

522
00:25:01.570 --> 00:25:04.450
excuse me, that um, we are probably

523
00:25:05.420 --> 00:25:07.980
limited to,

524
00:25:08.350 --> 00:25:11.340
um, the sorts of velocities that we

525
00:25:11.340 --> 00:25:14.180
see among the planets of the solar

526
00:25:14.180 --> 00:25:16.900
system. Now remember, the Earth is orbiting

527
00:25:16.900 --> 00:25:19.340
the sun at 30 kilometres per second.

528
00:25:20.170 --> 00:25:23.100
Um, and, um, those velocities

529
00:25:23.100 --> 00:25:26.060
get less as you get farther away from the sun. And

530
00:25:26.060 --> 00:25:29.060
that's part of the equation with a slingsot, because what you're

531
00:25:29.060 --> 00:25:31.900
trying to do is steal some momentum from the planet and,

532
00:25:31.970 --> 00:25:34.890
and give it to the spacecraft. And so there are upper

533
00:25:34.890 --> 00:25:37.690
limits, uh, on, um, what sort of velocity

534
00:25:37.690 --> 00:25:40.610
change you can get. It depends on how close

535
00:25:40.610 --> 00:25:43.370
you go to the planet, depends whether the planet's got an atmosphere or

536
00:25:43.370 --> 00:25:46.160
not. It, uh, depends on the angle that you come in. Um,

537
00:25:46.370 --> 00:25:49.370
the figure that I've seen quoted As a maximum

538
00:25:49.370 --> 00:25:52.370
for Jupiter, which is the most effective planet for this sort

539
00:25:52.370 --> 00:25:55.250
of thing, being by far the most massive planet in the solar system,

540
00:25:55.730 --> 00:25:57.890
is a change of 40 kilometres per second.

541
00:25:58.810 --> 00:26:01.690
Um, now that's very good if you're

542
00:26:01.770 --> 00:26:04.490
you know, trying to get something out to the outer solar system,

543
00:26:04.810 --> 00:26:07.610
but it's not going to help you getting things

544
00:26:07.770 --> 00:26:10.730
to other planets. Especially when you think,

545
00:26:11.130 --> 00:26:14.010
you know, if you give uh, a planet,

546
00:26:14.410 --> 00:26:16.490
sorry a spacecraft, an impulse

547
00:26:17.530 --> 00:26:20.530
Delta V of 40 kilometres per second by interacting with

548
00:26:20.530 --> 00:26:23.370
Jupiter, you've got to then find

549
00:26:23.370 --> 00:26:26.290
another planet that's, that's going to give

550
00:26:26.290 --> 00:26:29.090
it even more. But the other planets are all moving slower than

551
00:26:29.090 --> 00:26:31.930
that so uh, the change in

552
00:26:31.930 --> 00:26:34.530
momentum is a lot harder to get. Uh,

553
00:26:34.610 --> 00:26:37.490
so I think the answer is it's a very nice idea. As

554
00:26:37.890 --> 00:26:40.529
Joe suggests, winding up by all these gravitational

555
00:26:40.529 --> 00:26:43.010
interactions, you can only do it within

556
00:26:43.010 --> 00:26:44.850
limits. You're not going to be able to get

557
00:26:45.730 --> 00:26:48.530
like 100,000 kilometres per second or something like that

558
00:26:48.610 --> 00:26:49.410
from doing that.

559
00:26:49.730 --> 00:26:52.610
Andrew Dunkley: Yeah, I suppose you could equate it to using

560
00:26:52.610 --> 00:26:55.490
a slingshot or a shanghai. There's only so much

561
00:26:55.490 --> 00:26:58.350
tension you can push, put in, into the, the rubber band,

562
00:26:58.350 --> 00:27:01.190
let's say to fire the rock. And you're not going to be able to

563
00:27:01.190 --> 00:27:03.670
fire the rock any faster than the

564
00:27:03.670 --> 00:27:06.670
maximum amount of storage the rubber band can hold.

565
00:27:06.670 --> 00:27:08.910
And I'm guessing it's the same.

566
00:27:09.230 --> 00:27:12.190
Professor Fred Watson: Yes, there's a, there's a limited amount of energy

567
00:27:12.269 --> 00:27:14.830
that you can get from, from a slingshot. That's right,

568
00:27:15.790 --> 00:27:17.190
yeah. Nice idea there.

569
00:27:17.190 --> 00:27:20.070
Andrew Dunkley: Although it's, it's been very effective as you

570
00:27:20.070 --> 00:27:23.030
said, for sending things to the outer solar system.

571
00:27:23.030 --> 00:27:25.410
The, the Voyager probes particularly

572
00:27:25.940 --> 00:27:28.930
uh, used um, the slingshot effect,

573
00:27:29.680 --> 00:27:32.570
um, several times to get to

574
00:27:32.570 --> 00:27:35.410
the outer solar system because they didn't have the fuel to do it.

575
00:27:36.130 --> 00:27:38.530
So they figured out through um,

576
00:27:39.170 --> 00:27:42.090
an alignment of the planets that they

577
00:27:42.090 --> 00:27:44.450
could get out there just by using

578
00:27:45.490 --> 00:27:48.230
the rotation of the planets or um,

579
00:27:48.930 --> 00:27:51.510
the process uh, that uh, uh,

580
00:27:51.760 --> 00:27:54.640
Joe's been talking about. So um, yeah it does

581
00:27:54.640 --> 00:27:57.360
work quite effectively for slower,

582
00:27:58.400 --> 00:28:00.560
slower speeds that uh, yeah,

583
00:28:00.800 --> 00:28:03.600
interstellar, probably beyond us in that

584
00:28:03.600 --> 00:28:04.080
regard.

585
00:28:04.480 --> 00:28:07.180
Professor Fred Watson: Yeah, probably the lasers and um,

586
00:28:07.360 --> 00:28:10.320
you know in a solar cell or a light sail might be a

587
00:28:10.320 --> 00:28:13.040
better bet. But even that beyond our technology

588
00:28:13.120 --> 00:28:13.840
at the moment.

589
00:28:16.040 --> 00:28:18.720
Andrew Dunkley: Um, probably won't be for long though. I think they'll develop

590
00:28:18.720 --> 00:28:21.500
that and get some spacecraft

591
00:28:21.500 --> 00:28:24.300
heading out towards the Alpha Centauri sector and

592
00:28:25.160 --> 00:28:28.000
um, anyway that remains to be seen. Uh,

593
00:28:28.000 --> 00:28:30.740
but that would still be a pretty slow mission in the scheme of things.

594
00:28:30.740 --> 00:28:33.580
But um, yeah, great question Joe,

595
00:28:33.580 --> 00:28:36.540
thanks for sending it in. And if you'd like to send us a

596
00:28:36.620 --> 00:28:39.500
question, uh, you can do that, uh, through

597
00:28:39.500 --> 00:28:41.780
our website, spacenutspodcast.com

598
00:28:41.780 --> 00:28:44.580
spacenuts IO. Click on the AMA

599
00:28:44.580 --> 00:28:47.210
link at the top and you can send us text and

600
00:28:47.210 --> 00:28:50.130
audio questions. And don't forget to tell us

601
00:28:50.130 --> 00:28:53.010
who you are and where you're from. We love to know that sort of stuff so that we

602
00:28:53.010 --> 00:28:55.770
can send the boys around. Or, uh, we could send

603
00:28:55.770 --> 00:28:58.450
Huw around because he can't be with us today, so he must be

604
00:28:58.450 --> 00:29:01.330
visiting one of you guys, um, with his, with his,

605
00:29:01.440 --> 00:29:04.170
um, you know, balaclava on, maybe.

606
00:29:04.170 --> 00:29:04.690
Yeah.

607
00:29:05.250 --> 00:29:08.050
Professor Fred Watson: Thank, um, you, Fred Watson, as always, a pleasure. Andrew, as

608
00:29:08.050 --> 00:29:10.970
always. Good to talk and uh, good to hear our

609
00:29:10.970 --> 00:29:12.200
listeners questions. It's.

610
00:29:12.990 --> 00:29:15.750
Andrew Dunkley: It is, it is. All right, well catch you again

611
00:29:15.750 --> 00:29:18.710
real soon. Professor Fred Watson Watson, astronomer at large, and from me,

612
00:29:18.710 --> 00:29:21.430
Andrew Dunkley. Thanks for your company. See you on the next

613
00:29:21.430 --> 00:29:23.470
episode of Space Nuts. Bye for now.

614
00:29:24.670 --> 00:29:26.950
Professor Fred Watson: You've been listening to the Space Nuts.

615
00:29:26.950 --> 00:29:29.910
Andrew Dunkley: Podcast, available at

616
00:29:29.910 --> 00:29:31.870
Apple Podcasts, Spotify,

617
00:29:32.030 --> 00:29:34.790
iHeartRadio or your favourite podcast

618
00:29:34.790 --> 00:29:36.590
player. You can also stream on

619
00:29:36.590 --> 00:29:39.550
demand@bytes.com. um, this has been another

620
00:29:39.550 --> 00:29:41.840
quality podcast production from Bytes.

621
00:29:42.470 --> 00:29:42.710
Professor Fred Watson: Com.