Megastructures, Exoplanet Myths & Satellite Showers: #495 - The Quipu Conundrum and More

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Andrew Dunkley: Hi there, thanks for joining us. This is Space Nuts. Andrew Dunkley

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here. Good to have your company. And on this episode

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we have a lot to talk

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about.

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The uh, first thing will be a megastructure of

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epic proportions discovered in the universe. Now this is

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not a uh, uh, something that was

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manufactured by some incredible race

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because uh, we have talked about megastructures in the past.

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Now this is natural and it's called Quipu.

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What's that mean? We'll tell you soon. Um, this

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is uh, one of um, the biggest bugbears that

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Jonti has to deal with the overselling of the

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potential for life on exoplanets. Yes, there is

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one in the news at the moment. We'll do an update on

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M20, 24 yr, uh 4. The

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odds of it hitting us have halved and

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SpaceX satellites raining down on our

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atmosphere. Uh, what does that mean? We'll tell

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you on this episode of space. Space

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nuts.

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Generic: 15 seconds. Guidance is internal.

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10, 9. Ignition

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sequence start. 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 he's back again, surprisingly.

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It's Jonti Horner, professor of Astrophysics at the University of

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Southern Queensland. Jonti. Hello.

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Jonti Horner: G'day. How are you going?

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Andrew Dunkley: I am well. How are you?

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Jonti Horner: I'm getting there. I've never got the hang of mornings. I think I'm a bit

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like the um, characters from the Hitchhiker's Guide. Except

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for me it's mornings. It's not Mondays, it's mornings.

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Andrew Dunkley: Yes, I, I used to be like that and then

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I started in breakfast radio and did it for 30 years.

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So I, I eventually got used to being up at

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Sparrows.

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Jonti Horner: The breakfast shift does not sound fun.

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Andrew Dunkley: Uh, I enjoyed it but that was just me. I don't

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know if anyone else did, especially the audience. Boom, boom.

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Jonti Horner: Uh.

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Andrew Dunkley: All right, uh, let us get into it and we're going

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to start off with this discovery, um, of a

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megastructure which has uh, been uh,

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in the news over the last week or so

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and it's, it's called Quipu. We'll

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explain why it's called that soon. But this is a

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megastructure, uh, of natural formation in the

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universe. The enormity of this is

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mind splittingly amazing.

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Jonti Horner: Yes, yes it is. It's one of those things that just makes

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your head hurt like a lot of things in cosmology. Now

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I'll happily hold my hands up right at the start and say

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my expertise is on the parts of the universe that are a lot closer

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than this. So I'm not a cosmologist, and if there are

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cosmologists listening in or people who are cosmology

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enthusiasts and I get something wrong, please don't be too

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critical. Um, because, you know,

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the size of the things that I don't know in cosmology is enormous.

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M just like the subject itself. But

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this is a really interesting one. When we think

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about the universe, you see all these wonderful

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simulations that come out of our models of

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how the universe works that people produce all the time.

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And, um, you can almost see videos on

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fabulous documentary series where they start at the scale of an atom

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and keep zooming out, and you eventually get to the person and

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keep zooming out. And the scale of

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cosmology is roughly the

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same scale compared to a human being, that a human being is

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compared to an atom. So that's the kind of size scale we're talking

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about here, which is the study of the

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ridiculously big. But as you zoom out from that human

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being on the earth, you get the solar system, then you get the local

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stars, then you get our galaxy. And then as you move

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out, you get structures of galaxies together.

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So you get small clusters of galaxies, and those

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small clusters hang together in bigger clusters that

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gather together in superclusters. And they,

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for a long time, were kind of the biggest structures we saw in the

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universe. But then as you zoom out further, you

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start seeing these structures like walls

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and filaments, where those clusters and super

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clusters of galaxies are themselves forming structures with

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huge voids in between. So on this kind of scale, when you

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see those simulations, it looks almost like

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a view of a sponge. So if you've

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had a sponge in your bath, the

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sponge is a lot of open air spaces

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surrounded by lots of solid material. And all the solid material

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is in contact with all the solid material, but all the

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air is in contact with all the air. So you could put a bit of string and go

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all the way through the sponge, through the air holes, and come out the other

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side and m that's kind of what this view

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of the universe looks like. It sees long filaments

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and walls all connected to one another

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with these enormous voids of empty space between

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them. That's the context we're talking about here.

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So the team of researchers who studied this have

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been carrying out observations using an X

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ray survey looking at very high energy electromagnetic

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radiation that's produced from incredibly hot gas

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in the most massive clusters of galaxies. Enormous

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structures themselves, and they've looked

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at a region about 250 million

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parsecs across in all directions, maybe a bit

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more, looking for the biggest

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structures they can find in that region. And they've

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identified four of these, what they're calling

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superstructures. And their superstructures are

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megastructures because they are bigger than normal structures.

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They're structures made of structures made of superclusters made of

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clusters made of local clusters made of

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galaxies. On we go all the way down

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again. Now, these four structures that

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they found between them contain

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45% of all the galaxy clusters. They could

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see 30% of all the galaxies and 25%

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of all the matter, but they only occupy about

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13% of the volume. So that gives you the idea

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of lots of empty space with these filaments

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around it. The biggest of these, this is

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someone quipu that's getting all the attention

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is ridiculous. They talk about it being

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2000-000000-00000 times the mass of the

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sun. So if you remember. So for

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listeners in countries that do things differently, we're using the

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kind of British scale million billion system here. So a

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million is 10 to the six one with six zeros after

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it. A billion is a thousand million. So that's 10

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to the 9. A trillion is a thousand

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billion or a million million. That's 10 to the

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12. A quadrillion is a thousand

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trillion or a million billion or a billion million.

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So it's 10 to the 15, 200 of

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those means this is 2 times 10 to the 17

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or 2 with 17 zeros after

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it times the mass of the Sun. Now that's

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a number that is bound to make your head hurt. So I converted

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that down by looking at how many Milky

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Ways that would be. And that would be something like

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130,000 times the mass of our

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galaxy. So stupidly

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big numbers it is spread over a

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distance. It's a big long feature, about

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400 megaparsecs long. So one

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parsec is perversely the

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distance that an object would

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be away from the Earth if its

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parallax, as the Earth goes around the sun, was

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1/ arc second. It's a really obscure unit of

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measurement. It makes sense when you're doing the

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maths of measuring distance, but it's not particularly user

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friendly. It's a bit like talking in feet. Light

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years is a bit like talking in meters. Same kind of thing.

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Most people find light years more straightforward to

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visualize, but where one light year is the time it takes

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light to travel in one year, and there are

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3.26 light years in one parsec.

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So 400 megaparsecs is

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1.3 billion light years long. So

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in other words, light leaving one end of this structure will

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take 1.3 billion years

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or, uh, 1300 million years to go from one end

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to the other. So it's an enormous, enormous

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structure. Now, that's all well and good, and

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it's fabulous cataloging the biggest and the most massive and the

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brightest. And I know a lot of people, I do this occasionally. Look

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up Wikipedia articles like, what's the most massive star? What's the

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most luminous star? Things like that. But it's

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also really valuable to know this kind of stuff because if you study

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these big structures, that gives us information that

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we can compare to the models that are based on

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our current understanding of the universe to see

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if those models make sense. And, uh, the good thing is that

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the current models of how the universe work

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predict structures like this. So this is very much

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in line with what people expected to see. And

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that's a really good part of how science works. It's very much a

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case of our models predicted this and now you've

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seen it, that makes us happy because it means the models are working

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correctly. It also is the kind

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of information that's really useful for people studying

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the Big Bang and more ancient universe. Because

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structures like this are sufficiently massive,

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then they will influence our view of what is beyond.

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You get gravitational lensing from the big objects.

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You also even get. And, um, I don't fully understand how this

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works, but you also get the pollution of

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the cosmic microwave background, which is the

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last hiss of the Big Bang. It's

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our image of the last surface 300,000

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years after the Big Bang, where the universe became transparent.

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And we found little bits of structure in that which

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are important for us understanding how the modern

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structure of the universe formed. But that structure is

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polluted by the influence of these

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foreground objects by something called

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the integrated Sachs Wolfe effect. And I have no idea how

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that works, to be brutally honest. But

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if you've got something like that, that pollutes our view of

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what's beyond. And we want to understand what's

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beyond. The better we can see the foreground, the better

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we can account for it when we're studying the background. So

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getting studies of this a. It's fascinating. It's a

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really good test for our models. But it also

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allows us in the future to get a better handle

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on how things like the cosmic microwave background really

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look when you filter out the foreground mess.

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And I guess the equivalent here will be like having a

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light pollution filter for people who are astronomy

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photography enthusiasts. You've got a murky,

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light polluted sky, but if you put a light pollution filter on the front of

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your lens, you can cancel out that foreground mess and

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get a much better view of what's beyond. This

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will enable us to do that same kind of filtering when we're looking at the

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microwave background.

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So I think it's a fabulous story, full of

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numbers what make your head hurt. Quite.

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Andrew Dunkley: They're massive numbers. It's just uh,

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just incredible. Now why is

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it called Quipu?

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Jonti Horner: This is partially because of the structure. So it looks

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like a long thick filament with thinner filaments branching

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off the sides of it. The authors of this

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paper noticed that this looks very similar

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to the traditional counting instrument of the Incan

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people in Peru. Um, which was essentially they

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did their counting using knotted ropes and ah, that

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knotted rope counting device was a Quipu. So

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it's quite a nice nod to the traditional culture of

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that area in Peru. Again, I'm not an

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anthropologist or an archaeologist, I don't really know much more

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about it than that, but I think it is a really nice

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nod to a different culture. And

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as we've talked about in previous weeks, this idea of embracing

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all the cultures of the Earth in our studies going forward is

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really gaining traction. It's a really nice way of doing things, I

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think.

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Andrew Dunkley: Absolutely, yes, I'd agree. And uh, the

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Incans have a, um, strong history

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with astronomy so uh, that ties

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in well too. So yeah, fascinating.

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If you would like to chase up that story. It was published

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in Astronomy and Astrophysics, the journal. You can

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also read about it at the

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arxiv.org website. That's

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arXiv. I learned that last week.

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arxiv.org uh, yes,

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there was um, um, a lot of involvement from

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the Max Planck Institute in um, in

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running this. The author was Hans

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Boehringer. So uh, you might want to look that

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up.

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Space nuts.

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Uh, now, uh, let's move on to our next

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story. This is a pet peeve peeve story,

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um, which Jonti wanted to talk about. And look,

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I'm not surprised that bothers

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some people, uh, because I, I have

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often referred to the popular press when

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doing this podcast and how they latch onto

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something that isn't quite the story

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but it makes a great headline and that's what this is.

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Overselling the potential for life on

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exoplanets.

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Jonti Horner: Yeah, yeah, it's.

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Andrew Dunkley: And one in particular in the news at the moment.

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Jonti Horner: Well it's something that's niggled at me for a while. It should be said that

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the criticism here is not of the research done by these authors.

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They've done a fabulous bit of research and if you look at the paper,

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they've got the balance right. That's fine. But there

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is a very common trend, particularly among press

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offices at universities and also

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around a lot of media sites that rely on clicks for their

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income, to talk about

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the most habitable planet ever discovered. We found the

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most Earth, uh, like, planet ever. And the reports on this planet

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are not quite that bad, but they have been talking about

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potentially habitable planet discovered around nearby

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star, because that gets the clicks. And

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before we dig into this story, the reason that this niggles at

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me is that people are getting exo Earth

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fatigue and also life elsewhere fatigue.

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So by reporting things when we haven't

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actually found what the reports are saying, it creates this opinion that

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the science is already done. We've already discovered the

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autumn stuff. So when we finally find a planet that really does

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have life on it, or when we finally find a planet that

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genuinely is Earth, ah, 2.0.

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That'll be exciting. I'll be thrilled. We've finally got something to talk about

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and everybody will be kind of the boy who cried wolf. Well, you've told us that

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you've done this a million times already. Yeah, and it's easy.

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Why are you interested? You know, it's

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also the fact that we

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basically don't know enough to make these statements yet. So when you

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see a headline like, we found the most Earth, uh, like, planet

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ever. What it's actually telling you is we found a

300
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planet that's about the same diameter as the Earth, and

301
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that's it. So it's like me being an alien and

302
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visiting the Earth and scanning the oceans and saying, I

303
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found the most human, like, creature ever. It's about the same length and

304
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it's about the same weight and it's about the same size. It's called a

305
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dolphin. Nothing like a human

306
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whatsoever, but it's about the same size and about the same

307
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mass. So it's the most human, like, animal ever.

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So I get a bit grumpy. And there's a lot that goes into habitability

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that I can talk about a little bit later on, which is

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why I think this is a much more complex problem. And for me, that

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makes it much more interesting, a lot more research to do.

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But it does mean that when you get a claim saying, potentially

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habitable planet, or the most habitable planet we've ever

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found yet People even publishing articles about super

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habitable planets that are more suitable for life than Earth.

316
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I don't think you can say any of that. Aha.

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Uh, in this particular case, it is an interesting

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story. There is a star called 82

319
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Erudani, which also goes by the name HD

320
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20794. You know, astronomers love

321
00:14:57.410 --> 00:15:00.282
our acronyms and our barcodes. This

322
00:15:00.306 --> 00:15:02.794
is a star that you can see with the naked eye in the constellation of

323
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Eridanus, but it's not particularly bright. It's about magnitude 4,

324
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4 and a half. And for a while we've known it had

325
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two planets around it. But it's been monitored by

326
00:15:11.350 --> 00:15:14.206
the High Accuracy Radial Velocity Planet Search

327
00:15:14.238 --> 00:15:16.878
for Spectrograph HARPS in Chile. And

328
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HARPS is an incredible instrument.

329
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It allows you to measure the velocity of a

330
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star. So you take the light from a star, you

331
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break it up into its component colors, and laced

332
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across that spectrum is a series of dark lines.

333
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And those dark lines, which we call the Fraunhofer absorption

334
00:15:34.062 --> 00:15:36.528
lines, are, uh, the fingerprint of all the different

335
00:15:36.664 --> 00:15:39.552
atoms and molecules in the star's outer atmosphere.

336
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Every atomic species, every molecular species absorbs

337
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light at a very specific, unique set of

338
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wavelengths. And it imprints this dark set of

339
00:15:47.576 --> 00:15:50.448
lines across the star spectrum. Now, if the star's

340
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moving towards us, its light will be blue shifted.

341
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So all of those lines will move a little bit to the blue because of the

342
00:15:56.152 --> 00:15:58.992
Doppler effect. If it's moving away from us, the light will be

343
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redshifted. So it'll move a bit to the red again with the

344
00:16:01.812 --> 00:16:04.764
Doppler effect. And I've talked about this before, this is the

345
00:16:04.772 --> 00:16:07.468
equivalent of having the siren coming towards you and

346
00:16:07.524 --> 00:16:10.316
hearing it high pitched and fast with Nino, Nino,

347
00:16:10.348 --> 00:16:13.052
Nino and uh, then it moving away and you're hearing it low

348
00:16:13.076 --> 00:16:16.012
pitched and slow with Nino, Nino to do

349
00:16:16.036 --> 00:16:18.348
with the waves getting stretched or compressed

350
00:16:18.444 --> 00:16:21.372
essentially. Now what that means is if we

351
00:16:21.396 --> 00:16:24.332
measure the positions of these lines accurately enough, we can measure the

352
00:16:24.356 --> 00:16:26.960
change in the speed of the star as it moves around

353
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by seeing those lines move. So we can look at

354
00:16:30.000 --> 00:16:32.936
stars and see them wobbling and infer the presence of planets

355
00:16:32.968 --> 00:16:35.720
that we can't see by how those planets pull those

356
00:16:35.760 --> 00:16:38.744
stars around. But there are limits to this. There's a

357
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lot of challenges involved. So facility like the one

358
00:16:41.616 --> 00:16:44.568
we've got at the University of Southern Queensland, which is actually

359
00:16:44.624 --> 00:16:47.496
the Southern hemisphere's only dedicated exoplanet search

360
00:16:47.528 --> 00:16:50.312
facility, we can get an accuracy

361
00:16:50.376 --> 00:16:53.160
where we can measure the wobble of stars down to about two or three

362
00:16:53.200 --> 00:16:55.780
Meters a second. So we could see a star, ah,

363
00:16:56.214 --> 00:16:59.054
changing in speed by about as much as someone going at a

364
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very gentle jog. What that means is

365
00:17:01.910 --> 00:17:04.830
we could not find these particular planets, they're just

366
00:17:04.870 --> 00:17:07.662
much too hard. But the HAARP spectrograph is on

367
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a much bigger telescope in a much better

368
00:17:10.694 --> 00:17:13.310
location and it's an incredibly accurate piece of

369
00:17:13.350 --> 00:17:16.206
kit. So it lets you get down to sub meter

370
00:17:16.238 --> 00:17:18.590
per second measurements, which is

371
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breathtaking. Put that in perspective. We're looking at stars

372
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here whose distances are quadrillions ah,

373
00:17:24.712 --> 00:17:27.512
of kilometers away. Again using the units from before.

374
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These are stars where the light has taken decades to

375
00:17:30.496 --> 00:17:33.320
reach us and we are able to measure their

376
00:17:33.360 --> 00:17:36.360
velocity so accurately that we can see changes in that

377
00:17:36.400 --> 00:17:39.304
velocity of 50 centimeters a second.

378
00:17:39.472 --> 00:17:41.980
Wow, that's just astonishing precision

379
00:17:42.640 --> 00:17:45.500
and that's what the team have done. So they've observed this star, uh,

380
00:17:45.648 --> 00:17:48.644
HD 20794 for

381
00:17:48.732 --> 00:17:51.508
a number of years with haps getting more and more data

382
00:17:51.644 --> 00:17:54.580
tracking how the speed changes. And in the past they'd found

383
00:17:54.620 --> 00:17:57.252
two planets and hints of a third and they've now

384
00:17:57.276 --> 00:18:00.004
confirmed that third one. That third planet,

385
00:18:00.052 --> 00:18:02.820
HD2.0, uh, 794-D is

386
00:18:02.860 --> 00:18:05.764
making the star wobble with its speed changing

387
00:18:05.812 --> 00:18:08.260
by just 50cm a second plus and

388
00:18:08.300 --> 00:18:10.836
minus over a period of about 700

389
00:18:10.908 --> 00:18:13.770
days. So you're watching for 700 days,

390
00:18:14.150 --> 00:18:16.830
you get rid of all the other noise, the star wobbling around

391
00:18:16.870 --> 00:18:19.726
itself, just oscillating like a shruk

392
00:18:19.758 --> 00:18:22.702
bell. You get rid of the orbits of the two inner planets which

393
00:18:22.726 --> 00:18:25.006
are causing it to wobble by a similar amount with a different

394
00:18:25.078 --> 00:18:28.062
period and you're left with a tiny wobble of plus or

395
00:18:28.086 --> 00:18:30.958
minus 50cm a second that takes 700 days

396
00:18:31.014 --> 00:18:33.982
to complete once. And that's what they found. So this

397
00:18:34.006 --> 00:18:36.798
is our planet. It's a planet about six

398
00:18:36.854 --> 00:18:39.832
times the mass of the Earth, at least might be

399
00:18:39.856 --> 00:18:42.776
more than that. We don't know how edge on or tilted the orbit

400
00:18:42.808 --> 00:18:45.688
is because we're not seeing it transit. If it's tilted by

401
00:18:45.744 --> 00:18:48.600
30 degrees, the mass of this planet will be higher.

402
00:18:48.640 --> 00:18:51.496
If it's tilted by 60 degrees instead of being 6 earth

403
00:18:51.528 --> 00:18:54.504
masses, it'll be 12 earth masses. So this is a minimum

404
00:18:54.552 --> 00:18:57.512
mass. So it's what we call a

405
00:18:57.536 --> 00:19:00.488
super Earth, ah, or a mini Neptune. It's much

406
00:19:00.544 --> 00:19:03.480
more massive than our planet and certainly larger than our

407
00:19:03.520 --> 00:19:05.822
planet. It's moving on an orbit

408
00:19:05.886 --> 00:19:08.718
that if you calculated its semi

409
00:19:08.734 --> 00:19:11.342
major axis, the length of the

410
00:19:11.366 --> 00:19:14.334
ellipse, half the length of the ellipse, which sets a period

411
00:19:14.502 --> 00:19:16.560
that will put it in the habitable zone, um,

412
00:19:17.350 --> 00:19:20.222
that's what the paper says. Now, the habitable zone I'll get into in a

413
00:19:20.246 --> 00:19:22.670
second. But this planet moves on a very

414
00:19:22.710 --> 00:19:25.550
elongated orbit, so its distance from its star

415
00:19:25.590 --> 00:19:28.430
is changing by a factor of two from its closest to the star

416
00:19:28.470 --> 00:19:31.442
to the furthest away. Now, if you scale that up to

417
00:19:31.466 --> 00:19:34.354
the solar system and put it in the same place, temperature wise,

418
00:19:34.402 --> 00:19:37.266
as it is in its system. Now, if you put it in the solar

419
00:19:37.298 --> 00:19:39.922
system so that its orbit had that same temperature

420
00:19:39.986 --> 00:19:42.802
range, that would mean when it's closest to its star, it's as

421
00:19:42.826 --> 00:19:45.586
close as Venus. When it's furthest from its star, it's

422
00:19:45.618 --> 00:19:48.162
further out than Mars. You're going to

423
00:19:48.186 --> 00:19:50.882
have extreme, extreme temperature

424
00:19:50.946 --> 00:19:53.890
variability on this planet. Now, the habitable

425
00:19:53.970 --> 00:19:56.946
zone, um, is always thrown out for these planets. It's

426
00:19:56.978 --> 00:19:59.842
that Goldilocks idea. If you have a planet that's at the right

427
00:19:59.946 --> 00:20:02.752
distance from a star, the temperature will be not too

428
00:20:02.776 --> 00:20:05.632
hot and not too cold, and it'll be just right for liquid water on the

429
00:20:05.656 --> 00:20:08.640
surface. The subtle implication

430
00:20:08.720 --> 00:20:11.552
buried in this is not actually what I

431
00:20:11.576 --> 00:20:14.176
just said, but it's rather. If you took the Earth

432
00:20:14.368 --> 00:20:17.264
as the Earth is today, and dropped

433
00:20:17.312 --> 00:20:20.096
it where this planet is, would the Earth, uh, still have liquid

434
00:20:20.128 --> 00:20:22.976
water on its surface? Now, that's a subtle

435
00:20:23.008 --> 00:20:25.856
difference. But to illustrate it, if you think about the solar

436
00:20:25.888 --> 00:20:28.634
system, the boundaries of the habitable

437
00:20:28.682 --> 00:20:31.546
zone are usually set by looking at Venus and Mars. That's what's

438
00:20:31.578 --> 00:20:34.522
motivated this. The calculations are more robust, uh, now,

439
00:20:34.546 --> 00:20:37.498
but that's about where it washes out. Venus, closer

440
00:20:37.514 --> 00:20:40.474
to the sun than us, is super hot. 450 degrees

441
00:20:40.522 --> 00:20:43.066
centigrade on the surface and clearly not habitable.

442
00:20:43.258 --> 00:20:46.058
Mars is super cold. It's too cold for life. It's outside

443
00:20:46.114 --> 00:20:48.870
the habitable zone. The Earth's in the middle, and it's just right.

444
00:20:49.410 --> 00:20:52.346
But to illustrate why it's not so simple, imagine a thought

445
00:20:52.418 --> 00:20:55.402
experiment where you swap Venus and Mars around. If

446
00:20:55.426 --> 00:20:58.330
you put Mars where Venus is, it's got a thinner atmosphere than we

447
00:20:58.370 --> 00:21:01.354
do, so it's got less of a greenhouse effect. So

448
00:21:01.362 --> 00:21:04.266
it would probably remain clement where Venus

449
00:21:04.298 --> 00:21:07.226
would overheat. Similarly, if you put Venus where Mars

450
00:21:07.258 --> 00:21:10.074
is, Venus has this incredibly thick atmosphere with an

451
00:21:10.082 --> 00:21:13.050
incredibly strong greenhouse. It will probably still

452
00:21:13.090 --> 00:21:15.834
be habitable. It would still be warm enough where Mars

453
00:21:15.882 --> 00:21:18.794
wouldn't. So this habitable zone is a much woollier

454
00:21:18.922 --> 00:21:20.790
concept than I think most people

455
00:21:21.280 --> 00:21:24.280
realize. And it's just not really

456
00:21:24.320 --> 00:21:27.272
a guideline. It's just an indication that this could

457
00:21:27.296 --> 00:21:30.120
be somewhere worth looking at. It's not more than that, but it tends to get

458
00:21:30.160 --> 00:21:32.920
played up as being the Holy Grail. And

459
00:21:32.960 --> 00:21:35.832
one is in the habitable zone. It must therefore have

460
00:21:35.856 --> 00:21:38.696
the potential to be habitable. Whereas in fact, what you're

461
00:21:38.728 --> 00:21:41.592
saying is if you put the Earth on the orbit that this planet is

462
00:21:41.616 --> 00:21:44.552
on, it might still look like the Earth, except with

463
00:21:44.576 --> 00:21:47.160
the planet we're talking about at the minute. If you put the Earth on that

464
00:21:47.200 --> 00:21:50.130
orbit at, um, perihelion, when it was

465
00:21:50.170 --> 00:21:53.074
closest to the sun, it would receive a flux from

466
00:21:53.082 --> 00:21:55.810
the sun as high as Venus does. So the oceans would start to

467
00:21:55.850 --> 00:21:58.114
boil. Fortunately, it doesn't spend long at

468
00:21:58.122 --> 00:22:00.834
perihelion. We move quickest when we're closest to the

469
00:22:00.842 --> 00:22:03.682
object. We swing out through the habitable zone,

470
00:22:03.826 --> 00:22:06.626
probably everything's fine. But you've got bonkers weather

471
00:22:06.658 --> 00:22:09.522
because you're dealing with all that heat you've just been given. Then

472
00:22:09.546 --> 00:22:12.482
you get to your furthest point from the star and that's when you move

473
00:22:12.506 --> 00:22:15.260
the slowest. So this planet spends probably more than

474
00:22:15.300 --> 00:22:18.268
50% of its time further from its star

475
00:22:18.324 --> 00:22:21.308
than the outer edge of that habitable zone by calculation. So

476
00:22:21.364 --> 00:22:24.332
those oceans would freeze and you get this deep, Game

477
00:22:24.356 --> 00:22:27.292
of Thrones style winter. You'd have everybody going, oh, look, winter is

478
00:22:27.316 --> 00:22:30.252
coming. Everybody's doomed. And then it would

479
00:22:30.276 --> 00:22:33.212
swing back into the star and have a brief furnace like summer,

480
00:22:33.276 --> 00:22:36.124
and then a long cold winter again. It doesn't sound

481
00:22:36.172 --> 00:22:37.276
particularly clement.

482
00:22:37.388 --> 00:22:40.364
You add to that, though, the fact that this planet is six times the mass of

483
00:22:40.372 --> 00:22:42.888
the Earth means it's going to have a very

484
00:22:42.944 --> 00:22:45.912
substantial atmosphere, and I should say at least six times the mass of the

485
00:22:45.936 --> 00:22:48.872
Earth. A much thicker atmosphere means a much stronger

486
00:22:48.936 --> 00:22:51.560
greenhouse effect, which means the

487
00:22:51.680 --> 00:22:54.024
results of that extreme insolation, the extreme

488
00:22:54.072 --> 00:22:57.000
radiation at, uh, pericentre when it's closest to the

489
00:22:57.040 --> 00:22:59.928
star, is even more pronounced. So I don't

490
00:22:59.944 --> 00:23:02.696
think it's at all fair to say that this planet could be potentially

491
00:23:02.728 --> 00:23:05.624
habitable. And in fact, the authors of the paper

492
00:23:05.672 --> 00:23:08.672
themselves don't really say that. What they do say is, is that

493
00:23:08.696 --> 00:23:11.584
this planet crosses the habitable zone. And, um, because it's a

494
00:23:11.592 --> 00:23:14.496
bit bigger and, um, because it has this big variation in existence

495
00:23:14.528 --> 00:23:17.232
from the star and, um, because it's around a nearby

496
00:23:17.296 --> 00:23:19.792
star, could be a really good test case for us to

497
00:23:19.816 --> 00:23:22.656
practice our observation techniques to learn

498
00:23:22.688 --> 00:23:25.520
more about atmospheres of planets this size before

499
00:23:25.560 --> 00:23:28.224
we really look at ones that could be habitable enough

500
00:23:28.312 --> 00:23:31.296
like. But this planet certainly isn't it.

501
00:23:31.448 --> 00:23:34.048
And even then there's a whole heap of Other things that will impact

502
00:23:34.104 --> 00:23:36.868
habitability, which we may or may not have time to go into

503
00:23:36.924 --> 00:23:39.684
today. But the habitable zone really is just

504
00:23:39.772 --> 00:23:42.532
the first of an incredibly long list of

505
00:23:42.556 --> 00:23:45.412
variables that you can slide around that could

506
00:23:45.436 --> 00:23:48.372
influence a habitability. Because all it's saying is, how hot would

507
00:23:48.396 --> 00:23:50.276
the Earth be if you put it there? Essentially?

508
00:23:50.388 --> 00:23:53.364
Andrew Dunkley: Yeah, yeah. And at six times the size of the Earth,

509
00:23:53.412 --> 00:23:56.340
at least gravity has to be a factor as well,

510
00:23:56.380 --> 00:23:57.076
doesn't it?

511
00:23:57.228 --> 00:24:00.052
Jonti Horner: It does. I mean, if you estimate that

512
00:24:00.076 --> 00:24:02.660
this thing is twice the Earth's diameter and M, we don't know that

513
00:24:02.700 --> 00:24:05.628
because this thing doesn't transit its star,

514
00:24:05.684 --> 00:24:08.620
or we've never seen it transit its star. So its orbit is almost

515
00:24:08.660 --> 00:24:11.532
certainly not edron, which means its mass is probably a bit higher

516
00:24:11.556 --> 00:24:14.492
than we say that minimum is. But it means we have no way of

517
00:24:14.516 --> 00:24:17.516
measuring the size. Now, at six Earth

518
00:24:17.548 --> 00:24:20.380
masses or a bit heavier, it's near this boundary between what we call

519
00:24:20.420 --> 00:24:23.292
super Earth or mini Neptune. Super Earth

520
00:24:23.356 --> 00:24:26.092
is a rocky object with a big thick atmosphere, and

521
00:24:26.116 --> 00:24:28.860
mini Neptune is a big thick atmosphere with a rocky core.

522
00:24:28.940 --> 00:24:31.932
So you can see how that transitions between them. But if you

523
00:24:31.956 --> 00:24:34.764
estimate for a minute that it is a super Earth with a bit of a thick

524
00:24:34.812 --> 00:24:37.372
atmosphere, you could say, well, maybe it's twice the

525
00:24:37.396 --> 00:24:39.980
diameter of the Earth. Uh, and, uh, that would kind of make

526
00:24:40.020 --> 00:24:42.972
sense density wise. That would place it a little

527
00:24:42.996 --> 00:24:45.948
bit less dense than the Earth. But that might make sense because it's

528
00:24:45.964 --> 00:24:48.880
a little bit cooler for a lot of its orbit.

529
00:24:49.220 --> 00:24:52.012
Even in that scenario, the acceleration due to

530
00:24:52.036 --> 00:24:54.924
gravity on its surface will be 50% higher than that we

531
00:24:54.932 --> 00:24:57.844
have on the Earth right now. You know, so gravity

532
00:24:57.892 --> 00:25:00.644
will be stronger. We'd probably all, if we were there, be squat

533
00:25:00.692 --> 00:25:03.492
and dumpy and grumbling about how heavy we

534
00:25:03.516 --> 00:25:06.388
feel and all the rest of it. You know, I'm heavy enough already without giving

535
00:25:06.404 --> 00:25:07.440
me 50%.

536
00:25:08.220 --> 00:25:11.150
Andrew Dunkley: Yes, no, that's a fair point. But,

537
00:25:11.150 --> 00:25:14.132
uh, yeah, these, these stories are not uncommon now.

538
00:25:14.156 --> 00:25:17.124
And you make a very valid point that people will just, you

539
00:25:17.132 --> 00:25:20.084
know, when the day comes that we've genuinely got an Earth

540
00:25:20.132 --> 00:25:22.900
like planet Earth 2.0, uh, that

541
00:25:22.940 --> 00:25:25.784
could harbor life. People will go, yeah,

542
00:25:25.832 --> 00:25:28.248
right. Oh, ah, heard it all before.

543
00:25:28.384 --> 00:25:31.112
Jonti Horner: And it's dangerous. And quite often the

544
00:25:31.136 --> 00:25:33.656
researchers involved don't have control of that story.

545
00:25:33.728 --> 00:25:36.520
That's one of the reasons I love working

546
00:25:36.560 --> 00:25:39.544
with websites, like the conversation, where I control the narrative when I

547
00:25:39.552 --> 00:25:42.552
write articles. But it's also why I really appreciate our

548
00:25:42.576 --> 00:25:45.352
media team here at unisq because they

549
00:25:45.376 --> 00:25:48.344
actually talk to us when they're writing media releases and a lot of

550
00:25:48.352 --> 00:25:51.352
the bigger universities, the media team get hold

551
00:25:51.376 --> 00:25:54.348
of a paper and they write their own interpretation of it with, with a couple

552
00:25:54.364 --> 00:25:56.860
of quotes from the authors, but they don't let the authors read the

553
00:25:56.900 --> 00:25:59.788
release. Then you get journalists who read the media

554
00:25:59.844 --> 00:26:02.652
release and spin it further and you end up from an

555
00:26:02.676 --> 00:26:05.660
article that says, we found a planet that is interesting to being

556
00:26:05.780 --> 00:26:08.588
new. Earth planet has been found. Life 2.0

557
00:26:08.644 --> 00:26:11.308
is there. And that's not what anybody actually

558
00:26:11.364 --> 00:26:11.916
said.

559
00:26:12.068 --> 00:26:13.452
Andrew Dunkley: No, no, but it's a good way.

560
00:26:13.476 --> 00:26:15.964
Jonti Horner: To get hits and links to your university's website.

561
00:26:16.132 --> 00:26:18.972
Andrew Dunkley: Exactly. Yeah. Okay. If you'd like to

562
00:26:18.996 --> 00:26:21.756
read up on that, uh, the genuine article I'm talking

563
00:26:21.788 --> 00:26:24.092
about, uh, you can find it in the journal

564
00:26:24.196 --> 00:26:27.080
Astronomy and Astrophys. You

565
00:26:27.120 --> 00:26:29.832
feel better now that you've got that off your chest, Jon?

566
00:26:29.976 --> 00:26:32.840
Jonti Horner: This is a perpetual rant of mine. I actually did

567
00:26:32.960 --> 00:26:35.800
with my former mentor, Barry Jones, who passed away

568
00:26:35.840 --> 00:26:38.664
about a decade ago now. Um, we wrote

569
00:26:38.712 --> 00:26:41.320
my first ever review paper back in 2010 where I

570
00:26:41.440 --> 00:26:44.392
dug into this. So it always used to bug me that it

571
00:26:44.416 --> 00:26:47.000
was just, it's in the habitable zone, right? That's job

572
00:26:47.040 --> 00:26:49.992
done. And so we wrote this paper where we looked at all

573
00:26:50.016 --> 00:26:52.760
of the other things people have proposed that could make a planet more

574
00:26:52.800 --> 00:26:55.652
habitable or less habitable, more suitable. And for

575
00:26:55.676 --> 00:26:58.612
me, the thing here is, when we get to

576
00:26:58.636 --> 00:27:01.396
do observations to look for life on these planets,

577
00:27:01.508 --> 00:27:03.988
which is still a bit beyond us, but we're getting towards that

578
00:27:04.044 --> 00:27:06.772
point, those observations are going to be the

579
00:27:06.796 --> 00:27:09.476
hardest observations humanity's ever had to carry out. You're

580
00:27:09.508 --> 00:27:12.244
talking hundreds or thousands of hours on the biggest

581
00:27:12.292 --> 00:27:14.960
space telescopes, really competitive time.

582
00:27:15.580 --> 00:27:18.500
You're not going to be able to look at them all. So you're going to have to find a way

583
00:27:18.540 --> 00:27:21.492
to pick the best target. You're going to have to find a way to whittle down

584
00:27:21.516 --> 00:27:24.304
a list of hundreds or thousands into the best two or three.

585
00:27:24.472 --> 00:27:27.472
And you can't just use the habitables on there. So I thought, let's look

586
00:27:27.496 --> 00:27:30.020
at all the different things that can impact habitability

587
00:27:30.360 --> 00:27:33.232
to see if you can turn them almost into the volume sliders on

588
00:27:33.256 --> 00:27:36.112
the mixing desk of the dj, right? You can turn them

589
00:27:36.136 --> 00:27:39.024
up, turn them down, and see which planet

590
00:27:39.072 --> 00:27:41.920
gets the best score overall when you factor all of them in.

591
00:27:42.040 --> 00:27:44.992
And, um, some of them are things we can't yet observe. Some of them are things you

592
00:27:45.016 --> 00:27:47.472
might have to model with computer modeling, like I

593
00:27:47.496 --> 00:27:50.400
do. But it can be everything from the nature of the

594
00:27:50.440 --> 00:27:53.282
star itself, how Variable it is all the way

595
00:27:53.306 --> 00:27:56.130
through to the other planets in the system, what their gravity does,

596
00:27:56.170 --> 00:27:59.026
how much debris there is, and even down to the planet

597
00:27:59.058 --> 00:28:02.050
itself. Whether it has plate tectonics, whether it has a magnetic field,

598
00:28:02.090 --> 00:28:04.962
all of these things will factor in. It's not just as

599
00:28:04.986 --> 00:28:07.410
simple as where do you place it? Is it in the right

600
00:28:07.450 --> 00:28:08.070
spot?

601
00:28:09.290 --> 00:28:12.242
Andrew Dunkley: Valid point. All right. Uh, yeah, as

602
00:28:12.266 --> 00:28:14.962
I said, you can uh, chase that story up at Astronomy and

603
00:28:14.986 --> 00:28:17.810
Astrophysics. Uh, you could probably find it just about

604
00:28:17.850 --> 00:28:20.232
anywhere online. Uh, there's an article on

605
00:28:20.306 --> 00:28:23.196
Space.com as well. This is Space Nuts

606
00:28:23.228 --> 00:28:25.840
with Andrew Dunkley and John Horner.

607
00:28:30.020 --> 00:28:31.628
Space Nuts, right.

608
00:28:31.684 --> 00:28:33.820
Our next story, which uh,

609
00:28:34.228 --> 00:28:36.732
we've uh, done before, we did it a week

610
00:28:36.756 --> 00:28:39.564
ago, uh, about uh, the comet

611
00:28:39.612 --> 00:28:42.540
2024 yr. Uh 4. I happen to be

612
00:28:42.580 --> 00:28:45.244
playing our uh, podcast in the car.

613
00:28:45.412 --> 00:28:48.288
I always like to listen to it just to see how it sounds

614
00:28:48.304 --> 00:28:51.120
and you know, decide whether or not I'm doing a good

615
00:28:51.160 --> 00:28:53.904
job or not. Did it in radio, do it with the

616
00:28:53.912 --> 00:28:56.272
podcast. But I, I was picking up our

617
00:28:56.296 --> 00:28:59.220
grandchildren from school and uh,

618
00:28:59.220 --> 00:29:02.060
Nathaniel who um, is

619
00:29:02.520 --> 00:29:05.424
10, uh, years old, um, he was listening

620
00:29:05.472 --> 00:29:08.032
and he said to me, is a comet going to

621
00:29:08.056 --> 00:29:10.912
hit Earth? And I had to kind

622
00:29:10.936 --> 00:29:13.616
of explain to him what was going on without alarming

623
00:29:13.648 --> 00:29:16.412
him. Uh, and now an

624
00:29:16.436 --> 00:29:18.840
update on the story. Last week we were saying

625
00:29:19.300 --> 00:29:21.500
um, there was a 70 to

626
00:29:21.540 --> 00:29:24.540
77% chance of this thing, um,

627
00:29:24.540 --> 00:29:27.240
hitting the atmosphere in 2032.

628
00:29:28.720 --> 00:29:31.436
Uh, sorry, yeah, see that's,

629
00:29:31.548 --> 00:29:33.960
that was a popular press comment. One in seven.

630
00:29:34.260 --> 00:29:36.700
But now that number's dropped as at

631
00:29:36.820 --> 00:29:39.400
now. But that could change again.

632
00:29:39.710 --> 00:29:42.422
Jonti Horner: Absolutely. So as of today, so when I sent you

633
00:29:42.446 --> 00:29:44.790
notes through yesterday, it was at 1 in

634
00:29:44.830 --> 00:29:47.718
43. It's now fallen back to 1 in 48.

635
00:29:47.774 --> 00:29:50.662
This number is changing every day. And what we

636
00:29:50.686 --> 00:29:53.410
will see and what we'll continue to see is most likely

637
00:29:53.710 --> 00:29:56.374
those odds of an impact gradually

638
00:29:56.422 --> 00:29:59.270
increasing until eventually they

639
00:29:59.310 --> 00:30:02.230
most likely drop to zero. Ah. And the reason

640
00:30:02.270 --> 00:30:05.238
for that is we're getting more observations with every day that passes.

641
00:30:05.334 --> 00:30:07.904
And so with every day that passes we get a refined

642
00:30:08.062 --> 00:30:10.200
estimate of the orbit of this thing.

643
00:30:10.740 --> 00:30:13.724
That then means that uh, the exact location of the

644
00:30:13.732 --> 00:30:15.872
object on 22nd of December

645
00:30:16.031 --> 00:30:19.004
2032 has a smaller uncertainty. So

646
00:30:19.012 --> 00:30:21.692
that big area of space that we think it will be

647
00:30:21.716 --> 00:30:24.300
in with each day's observations get smaller and

648
00:30:24.340 --> 00:30:27.308
smaller. Now if the Earth is still in that area

649
00:30:27.364 --> 00:30:30.172
of space, the Earth is a bigger fraction of

650
00:30:30.196 --> 00:30:32.652
that total volume of space. And so the

651
00:30:32.676 --> 00:30:35.516
probability of impact is going up because we're a bigger

652
00:30:35.548 --> 00:30:38.420
fraction of the total area that thing could be in. But at some

653
00:30:38.460 --> 00:30:41.332
point, as that volume of space shrinks down, the

654
00:30:41.356 --> 00:30:43.860
Earth could fall out of it. And at that point, the probability

655
00:30:43.940 --> 00:30:46.868
immediately drops to zero. So it isn't a reason

656
00:30:46.924 --> 00:30:49.620
to panic at all. This is exactly the behavior you would

657
00:30:49.660 --> 00:30:52.548
expect to see. But that probability

658
00:30:52.644 --> 00:30:55.492
will continue to change day by day. It wouldn't surprise me if it

659
00:30:55.516 --> 00:30:58.468
keeps getting higher. Now, this asteroid we're

660
00:30:58.484 --> 00:31:01.412
probably going to lose track of in about April. It'll be too far

661
00:31:01.436 --> 00:31:04.334
away to observe, but then we won't see it

662
00:31:04.342 --> 00:31:06.926
again till 2028. People are digging back through

663
00:31:06.998 --> 00:31:09.150
archival observations from

664
00:31:09.190 --> 00:31:12.110
2016, 2012, 2008,

665
00:31:12.230 --> 00:31:14.942
because this thing comes roughly near the earth every four years or

666
00:31:14.966 --> 00:31:17.742
so. If we find it by chance

667
00:31:17.806 --> 00:31:20.526
on one photograph from one of those previous years,

668
00:31:20.678 --> 00:31:23.662
this probability will change dramatically and we'll probably drop to

669
00:31:23.686 --> 00:31:26.446
zero straight away. If not, we'll have to wait till

670
00:31:26.478 --> 00:31:29.374
2028. And until then we'll see this continual

671
00:31:29.422 --> 00:31:32.374
slight more wobbling around as each day's observations come

672
00:31:32.382 --> 00:31:34.550
in and it gets recalculated. So

673
00:31:34.590 --> 00:31:37.462
fundamentally, nothing has changed. This thing still

674
00:31:37.486 --> 00:31:40.342
poses a threat. Do not panic. Even if it were to hit us,

675
00:31:40.366 --> 00:31:43.270
it's not really going to cause a problem anyway, to be brutally honest.

676
00:31:43.430 --> 00:31:46.086
But it is fascinating to watch this happen

677
00:31:46.238 --> 00:31:48.850
and to see that evolution in real time.

678
00:31:49.790 --> 00:31:52.742
Andrew Dunkley: Absolutely. Yeah. I think I said comet, I meant asteroid.

679
00:31:52.806 --> 00:31:55.170
But, um, yeah, 2024, uh,

680
00:31:55.550 --> 00:31:58.496
if you do a search on Google or whatever your favorite

681
00:31:58.528 --> 00:32:01.020
search engine is, you'll find plenty of information.

682
00:32:01.800 --> 00:32:04.784
And you. I would advise filtering the

683
00:32:04.792 --> 00:32:06.620
popular press comments because,

684
00:32:08.130 --> 00:32:10.512
uh, they've been going hammer and tongs on this one.

685
00:32:10.616 --> 00:32:11.110
Jonti Horner: Absolutely.

686
00:32:11.110 --> 00:32:13.850
Andrew Dunkley: Um, but, yeah, uh, like, uh,

687
00:32:13.850 --> 00:32:16.832
Jonti said on the previous story, it's clickbait,

688
00:32:16.896 --> 00:32:19.770
isn't it? Um, that's really it. But, uh,

689
00:32:20.152 --> 00:32:22.960
I did reassure my grandson because as soon as I

690
00:32:23.000 --> 00:32:25.648
finished explaining it, he wanted to talk about

691
00:32:25.784 --> 00:32:28.656
Pokemon. So I think I was successful in deflecting

692
00:32:28.688 --> 00:32:29.500
him there.

693
00:32:30.020 --> 00:32:33.020
To, uh, our final story, Jonti, and this

694
00:32:33.060 --> 00:32:35.980
one is about stuff that's hitting the atmosphere.

695
00:32:36.140 --> 00:32:39.080
We're talking specifically about the,

696
00:32:39.390 --> 00:32:41.356
um, turnover of SpaceX

697
00:32:41.468 --> 00:32:44.396
satellites. They've been starting

698
00:32:44.428 --> 00:32:46.990
to rain down on Earth, uh,

699
00:32:47.068 --> 00:32:49.852
fairly regularly. In fact, uh, the Space Nuts podcast

700
00:32:49.916 --> 00:32:52.910
group on Facebook has been,

701
00:32:52.910 --> 00:32:55.868
um, discussing this. They put an article on there

702
00:32:55.924 --> 00:32:58.462
that the listeners were

703
00:32:58.566 --> 00:33:01.326
discussing, and some were quite

704
00:33:01.358 --> 00:33:04.062
surprised by the kinds of numbers we're talking about.

705
00:33:04.166 --> 00:33:06.718
But this is just going to get more and more

706
00:33:06.774 --> 00:33:09.406
significant as time goes on because they haven't finished

707
00:33:09.438 --> 00:33:12.254
deploying their entire, uh, fleet

708
00:33:12.302 --> 00:33:14.894
or whatever. You want to call them of, uh, SpaceX

709
00:33:14.942 --> 00:33:15.966
satellites.

710
00:33:16.158 --> 00:33:19.038
Jonti Horner: Yeah. This is yet another multifaceted story.

711
00:33:19.094 --> 00:33:22.078
So I know a lot of people who get very passionate

712
00:33:22.094 --> 00:33:24.910
in their defense of SpaceX and Elon Musk and many others who

713
00:33:24.950 --> 00:33:27.584
have very negative views of them. And I always try and be

714
00:33:27.742 --> 00:33:30.732
somewhere in the middle. It's like in literature if

715
00:33:30.756 --> 00:33:33.564
you ever read a book, very few people are

716
00:33:33.652 --> 00:33:36.508
purely evil or purely good. Everybody's somewhere in the middle

717
00:33:36.604 --> 00:33:39.484
unless it's a bad book. And it's the

718
00:33:39.492 --> 00:33:42.460
same with things like this. There's a lot of good about this and a lot of bad about

719
00:33:42.500 --> 00:33:44.876
it. Now SpaceX are putting up their Starlink

720
00:33:44.908 --> 00:33:47.756
satellites to deliver Internet

721
00:33:47.788 --> 00:33:50.764
access, which is a great benefit to people in the

722
00:33:50.772 --> 00:33:53.692
regions. I've heard plenty of stories of

723
00:33:53.716 --> 00:33:56.492
people who are living remotely in Australia who can't get a good

724
00:33:56.516 --> 00:33:59.368
Internet connection on Starlink as been revolutionary to them.

725
00:33:59.504 --> 00:34:02.392
Andrew Dunkley: Yeah. And cruise ships use Starlink.

726
00:34:02.536 --> 00:34:04.392
Jonti Horner: Absolutely. Because they're always.

727
00:34:04.496 --> 00:34:06.168
Andrew Dunkley: They're in remote areas a lot.

728
00:34:06.304 --> 00:34:08.792
Jonti Horner: Yeah, it is a really incredible

729
00:34:08.856 --> 00:34:11.832
technological development. On the other hand, you've got all the concerns about the

730
00:34:11.856 --> 00:34:14.760
light pollution from these things and

731
00:34:14.800 --> 00:34:17.640
the fact that they launched them without anybody really being able

732
00:34:17.680 --> 00:34:20.088
to regulate it or say boot about

733
00:34:20.144 --> 00:34:23.144
it. It's a multifaceted

734
00:34:23.192 --> 00:34:25.684
problem and there's good things and bad things about it.

735
00:34:25.872 --> 00:34:28.812
In much the same way, this story is both a

736
00:34:28.836 --> 00:34:31.532
good and bad story. You've got all these satellites up

737
00:34:31.556 --> 00:34:34.316
there and they have finite lifetimes.

738
00:34:34.508 --> 00:34:37.372
They are low down because you need them to be

739
00:34:37.396 --> 00:34:40.332
in low Earth orbit in order to get good latency. If you put these at

740
00:34:40.356 --> 00:34:43.260
geostationary orbit, you've got the light travel time there

741
00:34:43.300 --> 00:34:46.188
and back again, you've got a long way to go and

742
00:34:46.244 --> 00:34:49.100
that puts a significant ping, which means for the people playing

743
00:34:49.140 --> 00:34:51.900
Twitch games and first person shooter games,

744
00:34:52.020 --> 00:34:54.844
they can't play and sulk. Um, but everybody

745
00:34:54.892 --> 00:34:57.868
wants a faster Internet connection with the lowest latency possible.

746
00:34:57.924 --> 00:35:00.892
So these things are in low Earth orbit, which means that they

747
00:35:00.916 --> 00:35:03.756
are moving through a significant chunk of the Earth's

748
00:35:03.788 --> 00:35:06.604
atmosphere. The Earth's atmosphere doesn't just stop, it just gets thinner and

749
00:35:06.612 --> 00:35:09.596
thinner and thinner the further you go away. Technically, the moon

750
00:35:09.628 --> 00:35:12.572
is still encountering bits of the Earth's atmosphere. It should by that point it's so

751
00:35:12.596 --> 00:35:15.420
thin as to be irrelevant. But at the altitude of these

752
00:35:15.460 --> 00:35:18.460
Starlink satellites, they are actually traveling into

753
00:35:18.500 --> 00:35:21.332
a headwind. So without something to

754
00:35:21.356 --> 00:35:23.940
bump them up, they would eventually come down naturally anyway.

755
00:35:24.020 --> 00:35:26.836
But also they are a fixed

756
00:35:26.868 --> 00:35:29.652
term thing. They typically, I think thinking about

757
00:35:29.756 --> 00:35:32.676
an individual satellite having about A five year lifetime.

758
00:35:32.788 --> 00:35:33.444
Andrew Dunkley: Yeah.

759
00:35:33.572 --> 00:35:36.500
Jonti Horner: Now it's about five years since the Starlink satellite started getting

760
00:35:36.540 --> 00:35:39.156
launched, which means the very first generation of them

761
00:35:39.308 --> 00:35:41.640
are now in their retirement phase.

762
00:35:42.380 --> 00:35:45.252
What is really good about this is

763
00:35:45.276 --> 00:35:48.068
that SpaceX and Starlink are being

764
00:35:48.124 --> 00:35:51.102
very aggressive in the retirement in that they

765
00:35:51.126 --> 00:35:54.062
are controlling these things and deliberately putting them back in the

766
00:35:54.086 --> 00:35:56.878
atmosphere to burn up in a controlled fashion. So they're

767
00:35:56.894 --> 00:35:59.694
controlling where they drop them into the atmosphere to minimize the

768
00:35:59.702 --> 00:36:02.510
risk to air travel and the risk of them

769
00:36:02.550 --> 00:36:05.422
dropping on a city and things like this. And that

770
00:36:05.446 --> 00:36:08.334
is really good governance. It's really important to say that there's a lot

771
00:36:08.342 --> 00:36:11.182
of stuff up there that will come down of its own

772
00:36:11.206 --> 00:36:14.078
accord, at its own time, with no control over it.

773
00:36:14.214 --> 00:36:17.170
And that's a risk. And people are talking about the fact

774
00:36:17.210 --> 00:36:19.874
that there's probably as high as a 26% chance

775
00:36:20.002 --> 00:36:22.642
that in a given year from now on space debris will

776
00:36:22.666 --> 00:36:25.270
fall through a populated airspace

777
00:36:26.220 --> 00:36:29.202
m which is problematic. There's even studies saying there's a 1

778
00:36:29.226 --> 00:36:32.210
in 10 chance that within the next decade somebody will

779
00:36:32.250 --> 00:36:34.670
die as a result of space debris hitting them.

780
00:36:35.050 --> 00:36:37.954
So that's a concern. And by deliberately

781
00:36:38.002 --> 00:36:40.754
deorbiting these things in a controlled fashion, they're mitigating

782
00:36:40.802 --> 00:36:43.054
those risks, putting things down in a safe

783
00:36:43.102 --> 00:36:45.966
fashion. But because of how many satellites they're

784
00:36:45.998 --> 00:36:48.910
putting up there, that means we've got an increasing number of them coming

785
00:36:48.950 --> 00:36:51.934
back down. There are currently 7,000

786
00:36:52.022 --> 00:36:54.894
Starlink satellites up there. The goal is to get up

787
00:36:54.902 --> 00:36:57.822
to 42,000. That is their stated end.

788
00:36:57.926 --> 00:37:00.430
So that's the factor of six times more.

789
00:37:00.550 --> 00:37:03.390
Andrew Dunkley: Yeah, that's just Starlink, because there are many

790
00:37:03.430 --> 00:37:03.966
others.

791
00:37:04.118 --> 00:37:06.398
Jonti Horner: There are. If you look at all of the proposed mega

792
00:37:06.414 --> 00:37:09.250
constellations, I think the current number is that there

793
00:37:09.290 --> 00:37:12.226
could be as many as 550,000 satellites in orbit

794
00:37:12.258 --> 00:37:14.706
within a decade. Which makes me, as an amateur

795
00:37:14.738 --> 00:37:17.586
astronomer, the kind of part of me that goes out and observes meteor

796
00:37:17.618 --> 00:37:20.610
showers and stuff just makes me weep because we'll lose the night

797
00:37:20.650 --> 00:37:23.346
sky to such a degree. But that's a slightly

798
00:37:23.378 --> 00:37:26.322
separate thing. With 7,000 up there at

799
00:37:26.346 --> 00:37:29.234
the minute, the retirements of those first gen ones are now coming at a

800
00:37:29.242 --> 00:37:31.630
rate of four or five satellites per day.

801
00:37:32.010 --> 00:37:34.834
So that means four or five satellites are burning up somewhere

802
00:37:34.882 --> 00:37:37.822
over the Earth, uh, every single day of

803
00:37:37.846 --> 00:37:40.814
the calendar year. That's only going to go

804
00:37:40.822 --> 00:37:43.678
up because if you increase the number of satellites up there by a factor of

805
00:37:43.734 --> 00:37:46.142
six times, then you'll increase that number of

806
00:37:46.166 --> 00:37:48.958
reentries per day by a factor of six times. So within

807
00:37:49.014 --> 00:37:51.850
five Years, we could well be looking at

808
00:37:52.230 --> 00:37:55.102
something nearer to 25 or even 30 satellites per

809
00:37:55.126 --> 00:37:58.062
day coming back into the atmosphere. Now, these are coming in

810
00:37:58.086 --> 00:38:01.022
in a controlled fashion. So, uh, they're trying to drop them in the

811
00:38:01.046 --> 00:38:03.792
atmosphere away from things that would be threatened

812
00:38:03.856 --> 00:38:06.096
by lumps of metal hitting the Earth's atmosphere,

813
00:38:06.128 --> 00:38:08.992
essentially. Yeah. But there is now a growing

814
00:38:09.056 --> 00:38:11.088
concern about the pollution side of this.

815
00:38:11.224 --> 00:38:14.016
Andrew Dunkley: That's the thing that I was getting. Yeah, that's

816
00:38:14.048 --> 00:38:16.096
the. That's the big if, isn't it?

817
00:38:16.168 --> 00:38:19.152
Jonti Horner: And it's a difficult one because it's not an experiment that's ever been

818
00:38:19.176 --> 00:38:22.144
done before. Things have re entered. Um, but in

819
00:38:22.152 --> 00:38:25.040
the past, we've not been putting much up in space. So it's been a very

820
00:38:25.080 --> 00:38:28.064
rare thing. A little bit of extra material dumped into the

821
00:38:28.072 --> 00:38:31.062
atmosphere. A tiny amount compared to the amount that

822
00:38:31.086 --> 00:38:34.010
comes in naturally through meteors and meteorites,

823
00:38:34.370 --> 00:38:37.238
um, stuff hitting the Earth's atmosphere, naturally. But we're now getting

824
00:38:37.294 --> 00:38:39.542
to a stage where this is a significant amount of

825
00:38:39.566 --> 00:38:42.326
material entering the Earth's atmosphere. Each of these

826
00:38:42.398 --> 00:38:45.142
Generation 1 satellites is several hundred kilos of

827
00:38:45.166 --> 00:38:47.990
material. So when you've got five of them

828
00:38:48.030 --> 00:38:50.822
coming in a day, that's a couple of tons of material

829
00:38:50.966 --> 00:38:53.846
being ablated and added to the atmosphere, mainly

830
00:38:53.878 --> 00:38:56.382
in the form of heavy metals. There

831
00:38:56.406 --> 00:38:59.214
is a fact that I've pulled out of an interesting article.

832
00:38:59.302 --> 00:39:02.078
India Today of all places, have got a fairly good article about

833
00:39:02.134 --> 00:39:05.102
this. And, um, one thing they point out is that each

834
00:39:05.206 --> 00:39:08.126
individual one of these Generation 1 Starlink satellites,

835
00:39:08.158 --> 00:39:10.638
when it burns up in the atmosphere, when it ablates,

836
00:39:10.814 --> 00:39:13.518
deposits about 30 kilos of aluminum

837
00:39:13.614 --> 00:39:16.590
oxide into the upper atmosphere, about

838
00:39:16.630 --> 00:39:19.454
where the ozone layer is. Now that's a problem

839
00:39:19.542 --> 00:39:22.532
because aluminium oxide is a compound that is known to

840
00:39:22.556 --> 00:39:25.300
be very devastating to the ozone layer.

841
00:39:25.460 --> 00:39:28.084
It's a real problem. Now, if each satellite is dumping

842
00:39:28.132 --> 00:39:31.012
30 kg into the atmosphere, that has a

843
00:39:31.036 --> 00:39:33.812
potential to destroy a large amount of ozone.

844
00:39:33.956 --> 00:39:36.644
If you're suddenly dumping five of them in per day, that's

845
00:39:36.692 --> 00:39:39.440
150 kilos per day.

846
00:39:39.900 --> 00:39:42.692
We go up to the 25. Obviously, that

847
00:39:42.716 --> 00:39:45.572
goes up again from 150 kilos to what, five

848
00:39:45.596 --> 00:39:48.104
times 150, 750. 50

849
00:39:48.272 --> 00:39:50.616
nil. Your ton of aluminium oxide per

850
00:39:50.688 --> 00:39:53.656
day. Something that can damage the ozone layer.

851
00:39:53.688 --> 00:39:56.632
And we've only just got out of the time where we did an incredible job

852
00:39:56.656 --> 00:39:59.608
of preventing us killing the ozone layer. Yeah, we're

853
00:39:59.624 --> 00:40:02.600
about to start it again. People have

854
00:40:02.640 --> 00:40:05.576
tried to do some computational studies of the effects of adding

855
00:40:05.608 --> 00:40:08.520
all this metal to the upper atmosphere. And, uh, nobody really

856
00:40:08.560 --> 00:40:11.140
knows what's going to happen? Some studies have said

857
00:40:11.440 --> 00:40:14.296
that it could accidentally help to slightly mitigate climate

858
00:40:14.328 --> 00:40:17.016
change because it might increase the albedo of the Earth's atmosphere.

859
00:40:17.048 --> 00:40:20.022
It might cause more clouds to form, so it could reflect a bit

860
00:40:20.046 --> 00:40:22.950
more sunlight or could be good. But other studies have

861
00:40:22.990 --> 00:40:25.878
suggested the opposite, that it could actually lower the amount of clouds we've

862
00:40:25.894 --> 00:40:28.854
got and also add a bit more greenhouse nastiness

863
00:40:28.902 --> 00:40:31.814
to the mix. So it could have an impact on our climate. We

864
00:40:31.822 --> 00:40:34.406
don't know which way it'll go. It could have an impact on the ozone

865
00:40:34.438 --> 00:40:37.286
layer. We just don't know yet. And so what's

866
00:40:37.318 --> 00:40:40.262
happening with this is we're effectively running a

867
00:40:40.286 --> 00:40:42.982
science experiment like the ones you do in the lab, the ones you do at

868
00:40:43.006 --> 00:40:45.860
school without ever done it, without ever having

869
00:40:45.900 --> 00:40:48.852
done it before. And we're running it on the planet that

870
00:40:48.876 --> 00:40:51.844
is our own home. Um, so I guess it's a bit like,

871
00:40:52.012 --> 00:40:54.756
you know, you've got two unruly toddlers running around

872
00:40:54.828 --> 00:40:57.812
with, um, insects, prey. Like the stuff you've got

873
00:40:57.836 --> 00:41:00.404
to get rid of. The mosquitoes. Yeah. Running around

874
00:41:00.492 --> 00:41:03.492
emptying can after can of that in your house. And you just said, yeah, well,

875
00:41:03.516 --> 00:41:06.244
let's do it. What's the worst that can happen? And you just don't know.

876
00:41:06.412 --> 00:41:09.124
Andrew Dunkley: Yeah. Uh, 42,000

877
00:41:09.212 --> 00:41:12.100
satellites, when they're ultimately all up there, coming back down

878
00:41:12.140 --> 00:41:14.828
into the atmosphere, will deposit 1.26

879
00:41:14.924 --> 00:41:17.276
million kg of

880
00:41:17.348 --> 00:41:20.332
aluminium oxide. So, and that's going

881
00:41:20.356 --> 00:41:23.340
to be continuous because it's not just

882
00:41:23.380 --> 00:41:26.076
42,000. Uh, as they come down, they'll replace

883
00:41:26.108 --> 00:41:28.684
them and add more to get to their full

884
00:41:28.852 --> 00:41:31.532
structure. So it'll be an ongoing

885
00:41:31.596 --> 00:41:34.172
thing, multiplied by however many

886
00:41:34.276 --> 00:41:37.020
constellations are created to do the same thing. So.

887
00:41:37.060 --> 00:41:39.996
Jonti Horner: But it isn't also like, that is easily recoverable.

888
00:41:40.028 --> 00:41:42.300
That's a lot of resources that we're just losing.

889
00:41:42.460 --> 00:41:43.660
Andrew Dunkley: Yeah, exactly.

890
00:41:43.660 --> 00:41:46.396
Jonti Horner: Um, now, I could imagine a much further

891
00:41:46.468 --> 00:41:48.972
future where instead of things being retired by

892
00:41:48.996 --> 00:41:51.836
deorbiting them, you retire them by boosting

893
00:41:51.868 --> 00:41:54.428
them to kind of graveyard orbits and have something there

894
00:41:54.484 --> 00:41:57.280
collecting them and melting them down for the materials.

895
00:41:57.620 --> 00:42:00.476
That's why in the future, because that will be a lot more expensive.

896
00:42:00.668 --> 00:42:03.612
It's cheaper at the minute m to just throw them away. I mean, we

897
00:42:03.636 --> 00:42:06.572
see with recycling efforts that there's not much motivation to

898
00:42:06.596 --> 00:42:09.510
recycle when making things from new products is

899
00:42:09.550 --> 00:42:10.410
still cheaper.

900
00:42:11.470 --> 00:42:14.422
Andrew Dunkley: Yeah, well, if they could solve the latency problem, that

901
00:42:14.446 --> 00:42:17.158
would maybe help cure it as well.

902
00:42:17.214 --> 00:42:20.198
But how do you do that? Relay stations on Earth? I don't

903
00:42:20.214 --> 00:42:23.174
know. I Don't know. But, uh, yeah, that's a

904
00:42:23.182 --> 00:42:26.182
really fascinating story. I know Fred and I have talked about it before, but

905
00:42:26.206 --> 00:42:28.790
it's worth revisiting. And, uh, yeah, the information

906
00:42:28.910 --> 00:42:31.686
just keeps evolving over time

907
00:42:31.758 --> 00:42:34.460
and we're not nearly at

908
00:42:34.500 --> 00:42:37.450
capacity yet with these constellations. If you'd like to read it,

909
00:42:37.450 --> 00:42:40.044
uh, as Jonti said, it's, uh, on the website

910
00:42:40.132 --> 00:42:41.960
India today.in

911
00:42:42.980 --> 00:42:45.980
that brings us to the end of the show. Don't forget to visit our

912
00:42:46.020 --> 00:42:48.908
website or our social media sites. Plenty of things to see and

913
00:42:48.964 --> 00:42:51.804
do there. Uh, if you have any thoughts on any of the

914
00:42:51.812 --> 00:42:54.684
things we've discussed, by all means, uh, send us a message

915
00:42:54.732 --> 00:42:57.612
via our website. Just, there's a little, uh, button up the top of

916
00:42:57.636 --> 00:43:00.612
our homepage, um, ama, where you

917
00:43:00.636 --> 00:43:03.588
can send us messages and audio questions or whatever

918
00:43:03.604 --> 00:43:04.390
you like. Uh,

919
00:43:04.390 --> 00:43:07.252
spacenutspodcast.com or

920
00:43:07.276 --> 00:43:10.228
spacenuts IO is the place to

921
00:43:10.284 --> 00:43:13.268
go. John D. Thank you so much. We're at the end. We'll

922
00:43:13.284 --> 00:43:14.788
catch up with you real soon.

923
00:43:14.924 --> 00:43:17.332
Jonti Horner: It's absolute pleasure. Thank you for having me.

924
00:43:17.510 --> 00:43:20.372
Andrew Dunkley: Uh, John D. Horner, professor of Astrophysics at the University of

925
00:43:20.396 --> 00:43:23.310
Southern Queensland. Thanks to Huw in the studio, who,

926
00:43:23.310 --> 00:43:26.292
um. Well, he couldn't be with us today because he

927
00:43:26.316 --> 00:43:28.878
got hit by a piece of SpaceX

928
00:43:28.974 --> 00:43:31.422
satellite. Uh, no. No, he

929
00:43:31.446 --> 00:43:34.334
didn't. Maybe he did. I don't know. I haven't seen him for

930
00:43:34.342 --> 00:43:37.326
ages. And from me, Andrew Dunkley, thanks very much for your company.

931
00:43:37.398 --> 00:43:40.190
We'll catch you on the next episode of Space Nuts.

932
00:43:40.270 --> 00:43:41.290
Bye for now.

933
00:43:42.230 --> 00:43:44.494
Voice Over Guy: You've been listening to the Space Nuts

934
00:43:44.542 --> 00:43:47.470
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