Navigating Time, Saturn's Mysteries & Planetary Favourites | A Q&A Episode

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Andrew Dunkley: Hi there. Thanks again for joining us. This

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is a Q and A edition of Space Nuts where

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we talk astronomy and space science. And in a

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Q and A edition, uh, UQ and we

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A, uh. Which means we'll answer audience

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questions. Uh, today we're going to talk

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about, uh, moving through time. What does

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that mean? Uh, also some stuff from

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Saturn's rings and a sort, uh, of

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hypothetical. Not a hypothetical, but a, you

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know, uh, not even a what if question. It's

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just a question asking our favourite

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planets and why. Well, you know, um, that's

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Jonty's thing. So we will talk about all of

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that on this episode of space nuts.

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15 seconds. Guidance is internal.

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10, 9, ignition.

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Sequence time. 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. And while

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Fred Watson's away, Jonty is here to play

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and answer your questions. He is Professor

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Jonty Horner, professor of Astrophysics at

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the University of Southern Queensland. Hello,

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Jonny.

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Jonti Horner: Hey, how are you going?

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Andrew Dunkley: I'm very well. Good to see you again.

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Jonti Horner: Well, it's good, yeah. Now, I've got

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interesting questions today.

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Andrew Dunkley: Yeah, we've got some beauties. Um, we

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might get straight into it.

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Our first question comes from Rennie, uh, in

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sunny West Hills, California. Hi, Rennie.

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Rennie's a regular contributor, so we hear

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from Ren regularly.

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Uh, can you please explain what it means to

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be moving through time? If I

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theoretically could sit in a chair from birth

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to death, will I die on a faster

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timeline than someone who lived a regular,

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normal life? Uh, is

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what's ageing me about the movement of the

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Earth around the sun, combined with the sun

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moving around the galaxy, combined with the

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galaxies moving around each other, and my own

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physical movement,

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really, that. That's kind of a what if

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question. We love what if questions. Thanks.

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Uh, Rennie, um, let's open that one up to,

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uh, a little bit of, um, investigation.

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Jonti Horner: Absolutely. And I think the first thing I'd

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say here is, this is such a fun question. It

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may be. Well, give it a couple of months and

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ask it again and see whether Fred Watson

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gives a similar answer to me or not. Um,

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it's a really interesting one.

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So the idea of time being a

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dimension is something that I think makes all

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of our heads hurt a little bit when we first

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encounter it, and for most of us, continues

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to do so forevermore. It's one of

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the fundamentals of the idea of what I guess

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is often described as space time. Physics

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comes out of the work that people like Albert

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Einstein did with Relativity

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we used to the three physical

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three spatial dimensions, up,

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down, left, right and forward and back.

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Although I, I'm realising more and more that

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we actually live in a two, two plus one kind

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of existence really, because we don't

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look up very often. Part of our common sense

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is about two dimensional movement, not three

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dimensional, because we think about moving

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around on the surface of the Earth. And um,

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there's all sorts of weird and fundamental

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things with that. Now the idea that time is

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also a dimension is part of

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that whole thing of space time physics built

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into the relativity twins, you know, special

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in general. And it's a very weird one because

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with the other dimensions we choose

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where to move or we're carried along where

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we're aware of motion. Motion in a way that

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is changing direction, we can change speed,

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we feel urgency. But with

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time, when you get told that time's a

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dimension, you think, but I can't move, I

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can't choose my motion in it. Were all

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carried through time at 1 second per

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second. And um, so it's like a

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dimension without agency. It's all a little

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bit weird. Now it does

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lead to that concept of time as a dimension

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is one of the things that's part of the

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underpinning of all this stuff, like with

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special and general relativity, things like

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time dilation, stuff like this. It's

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also tied into,

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um, events and consequences, See

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logical order of things. You know, a cause

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has to cause an effect. You don't get the

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effect before the cause. Things like this.

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Now this

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rapidly gets very complicated. And I know at

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university, when you study physics as a

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partner to astronomy or you study, um,

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relative relativity as part of an astronomy

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thing, I'll know. A lot of people find it

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hugely challenging to get their head around

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it. And I will openly admit that when I did

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my relativity courses as an undergrad, my

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head hurt was really, really hard. And

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particularly in first year, special

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relativity didn't work for me. And it's

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something I always say to my students,

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something I'm very aware of and something

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I've said to listeners is that no one

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explanation will work for everybody. We

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all learn in different ways and one source

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that is brilliant for me might not be

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brilliant for you. So if my explanation

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doesn't work, please go out and seek another

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one. That's no slight on me. It just means

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that your way of learning and my way of

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explaining didn't m match in that case and

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another explanation is needed. And when it

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came to relativity, I was very much in that

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boat. I was sat in These lectures and this is

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all style education 30 years ago. And it

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actually is that 29 and a half years ago that

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I was in these lectures because it was late

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1996, sat there taking notes on

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paper while somebody's talking at you and

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writing on a board. So a lot of the

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information was going from my eyes to the

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page without going through my brain I

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suspect, you know, that autonomous writing

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thing. But it just wasn't gelling for me. The

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whole the equations are ah, written down

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so you can use them, but it wasn't making

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sense. And the course textbook we had was

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incredibly mathematical because

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the person who wrote the textbook understood

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it through the maths, so they explained it

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through the maths. And that's not the way

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that I learned. Some people learn brilliantly

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from maths. I don't. I'm much more of a

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visual form of pitch form, a metaphor type

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thinker than an equation is a be all and end

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all sorts of. About the only

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textbook I ever used in my undergrad days. I

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was terrible. I'd buy the textbooks, not open

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them and I'd sell them on at the end of the

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trimester, end of the term for someone else

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to take off me and probably do the same

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thing. But I found a textbook in the library

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that worked for me and ended up buying it.

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Now I was going to recommend it because it

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was so foundational in helping me to

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overcome something I couldn't understand.

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That I always think when people are

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struggling with the relativity stuff. Worth

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recommending it. It's a big book called Space

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Time Physics by Edwin F. Taylor and ah,

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John Archibald Wheeler. And to my shock I

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looked it up just before this podcast. Um,

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the first edition was published in 1965.

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So the first edition was born, was

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launched closer to the publishing of the

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theory of general relativity and the theory

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of Special relativity than my reading it.

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Um, certainly than we are today, should I

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say? Absolutely than we are today. Um, it is

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still in print and what worked for me was ah,

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it didn't go straight to the maths. Instead

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it used drawings and figures and thought

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experiments. And I read it voraciously.

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It was very readable. I remember it from 30

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years ago and it had an impact. So I'd really

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recommend that if you're struggling with the

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relativity stuff, um, go to your local

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library. The textbooks are punishingly

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expensive and um, therefore I'd always

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recommend people get them from library first

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and make absolutely sure. But if you're at

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all interested in those foundations of how

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relativity and everything works. I found that

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book Astonishing. Okay, that's all getting a

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bit off the topic though, but that explains a

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lot better than I could do. The concepts

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behind relativity that include time as a

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dimension include space time diagrams, which

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are these weird cone shaped figures where

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if you're travelling at the speed of light,

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you move the same distance in X, which is

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distance, as you do in time Y. So you get a

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cone opened out like this and everything

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inside that cone is moving slower than the

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speed of light because it's going up the Y

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axis quicker than it goes on the X axis.

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Anything that is nearer to the X axis of

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that line is further away from the observer

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than they could observe it yet. So any light

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that left that would not have reached you yet

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now hard to visualise. But if you look into

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the book, that is what it means.

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Now, moving in time is

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talking about our motion on the Y axis of

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that graph, where we move up it by one second

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every second. That is something

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over which we do not really have control.

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Um, I suspect some people would argue that

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certain substances that can be ingested

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change your perception of how time loads. So

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you might be able to control the speed you

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fly through it there. But that's what we mean

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by moving in time. It's perceiving time

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moving forward so that from one second to

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the next, change happens. You know,

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yesterday is a time in the past that's

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already happened. That's a cause you'll see

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the effects today. Tomorrow hasn't happened

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yet. You can't see what is there tomorrow.

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That's what it means by moving in time. And

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it. There's all sorts of wonderful ways

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people have described it or played with this

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again. You know, I often come back to the

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Terry Pratchett stuff and I was just looking

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at a thread the other day of people talking

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about their favourite Terry Pratchett quotes.

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I'll just try and pull this one up.

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Um, it's from when the eternal

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is surprised. Uh, who was the founder of the

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History Monks, um, basically

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talking about his perception of time. So I'm,

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you know. MAN LOOKS AT KEYBOARD Because I

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didn't think of doing this. But yeah, this is

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from Thief of Time, I think it was. Yes.

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Um, talking about how when

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viewed the universe and viewed moving through

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time as this ancient philosopher who set

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up the Monks of History, who are the people

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who run around unseen in the background,

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fixing things when they go wrong. Because in

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the Discworld they go wrong all the time. But

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says when considered the nature of time

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and understood that the universe is instant

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by instant, Recreated anew. Therefore, he

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understood there is, in truth, no past, only

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a memory of the past. Blink your eyes and the

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world you see next did not exist when you

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closed them. Therefore, he said, the only

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appropriate state of the mind is surprise.

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The only appropriate state of the heart is

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joy. The sky you see now you have never

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seen before.

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The perfect moment is now. Be glad of it.

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Andrew Dunkley: That's good.

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Jonti Horner: I talk about Pratchett a lot, but I always

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think that's really beautiful. And it fits in

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with this concept of time

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moving irrevocably forward. You can never

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return to the past and change things. What

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you can change is the future. When you

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wake up every morning, it says, though you're

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newborn into the universe effectively,

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because who is to say that you ever lived

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before? You know, it may well be that all of

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your memories were just implanted in you when

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you woke up this very instant. We don't know.

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Obviously, the Occam's Razor

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argument is, yes, you existed yesterday and

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we did do the record the other day. But it's

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interesting to think of that and it's the way

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that people perceive time.

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Now, moving on to the motion side of it,

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Renny M. Um, the idea of sitting in a chair

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from birth to death and how that would affect

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your life. I'm not a medic, but I suspect if

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you ask your doctor that question, they will

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probably tell you that indeed, if you sat in

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a chair from birth to death, your life would

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be shorter than if you lived a normal life as

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a person because of health reasons. I mean,

286
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if nothing else, if there's no one around to

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feed you, it might lead to a relatively short

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existence. So there is that aspect of

289
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it as well. We can't see the

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future, so we can't predict what our choices

291
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are going to do in terms of lengthening or

292
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shortening our lives. But there is one way in

293
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which your motion can lead to you having a

294
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slightly different timeline.

295
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So from the point of view of your life, or

296
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the number of beats of your heart, or your

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perceived time, you'll live the time that you

298
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live. The faster you're moving though. Ah,

299
00:11:56.100 --> 00:11:58.980
and this is an outcome of general relativity.

300
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Motion causes time dilation,

301
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particularly motion with acceleration. You

302
00:12:04.650 --> 00:12:06.730
know, there's loads and loads of complexity

303
00:12:06.730 --> 00:12:09.370
to this. If you were moving

304
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faster, the time you

305
00:12:12.090 --> 00:12:14.850
perceive is very slightly slower. Now

306
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you then get into rest frames and all that

307
00:12:17.290 --> 00:12:19.330
stuff makes my head hurt. So the only place

308
00:12:19.330 --> 00:12:21.730
this actually really becomes relevant,

309
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particularly in our day to day lives, in

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our lived experience, is when you've got a

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moving platform that's changing direction so

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it's undergoing acceleration. Think about

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satellites circling the Earth. They uh, are

314
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circling the Earth, they are moving at uh, a

315
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faster speed than we are here on the surface

316
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of the Earth. We however are slightly nearer

317
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the centre of the Earth. So we get a little

318
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bit of gravitational time dilation. As I

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understand it, our clock runs slightly

320
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slower because we're at the bottom of a

321
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gravity well. But that is hugely overcome by

322
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the fact of the high speed things are moving

323
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in orbit. You're talking several kilometres

324
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per second. Now under

325
00:13:00.090 --> 00:13:03.010
general and special relativity you can work

326
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out the number of seconds you experience per

327
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second that ticks in a certain rest frame

328
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using these equations to get the time

329
00:13:10.650 --> 00:13:13.090
dilation. And typically that is a

330
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vanishingly, vanishingly small effect unless

331
00:13:15.210 --> 00:13:17.410
you get very near the speed of light, then it

332
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ramps up. But it is a large enough effect

333
00:13:20.170 --> 00:13:23.050
that both we need to understand

334
00:13:23.210 --> 00:13:24.890
it and we can measure it

335
00:13:26.050 --> 00:13:28.330
now to illustrate the level of this. It's not

336
00:13:28.330 --> 00:13:30.370
a huge effect. There's a fabulous stat

337
00:13:31.330 --> 00:13:33.610
that there are people who spent time on the

338
00:13:33.610 --> 00:13:35.930
International Space Station who therefore

339
00:13:35.930 --> 00:13:37.890
technically have experienced less time

340
00:13:37.890 --> 00:13:39.610
passing while they were up there than we did

341
00:13:39.610 --> 00:13:41.970
on the ground watching them because of time

342
00:13:41.970 --> 00:13:43.530
dilation, because of their fast movement and

343
00:13:43.530 --> 00:13:45.250
their acceleration and all the rest of it.

344
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Space stations go around the Earth, what,

345
00:13:47.650 --> 00:13:50.290
nearly eight kilometres per second, roughly.

346
00:13:50.370 --> 00:13:52.170
A couple of Russian guys were up there for

347
00:13:52.170 --> 00:13:54.830
six months, Sergei Krikalev and

348
00:13:54.830 --> 00:13:57.790
Sergey Avdeev. They did six months

349
00:13:57.790 --> 00:14:00.190
up there and as a result of time

350
00:14:00.190 --> 00:14:03.150
dilation, when they returned to the surface

351
00:14:03.150 --> 00:14:05.430
of the Earth, they would have experienced

352
00:14:05.430 --> 00:14:07.670
less time passing than the people on the

353
00:14:07.670 --> 00:14:09.270
ground did while they were up there. Yeah,

354
00:14:09.430 --> 00:14:11.310
but not enough for them to perceive. It would

355
00:14:11.310 --> 00:14:14.110
have been 20 milliseconds. Right. Uh, so

356
00:14:14.110 --> 00:14:16.650
that's 0.02 seconds, um,

357
00:14:16.650 --> 00:14:19.510
21,000th of a second. It's not very much,

358
00:14:19.510 --> 00:14:22.110
but it has a huge impact on our day to day

359
00:14:22.110 --> 00:14:25.070
life. And this means that that

360
00:14:25.230 --> 00:14:27.710
part of the theories of relativity

361
00:14:28.110 --> 00:14:31.070
are among the most tested theories ever

362
00:14:31.070 --> 00:14:32.790
to have been developed by humans. And the

363
00:14:32.790 --> 00:14:35.350
reason I say that is that every time you use

364
00:14:35.350 --> 00:14:37.910
your generic fruit based device to

365
00:14:37.910 --> 00:14:40.790
navigate, anytime you use a sat nav, you're

366
00:14:40.790 --> 00:14:42.270
using GPS satellites.

367
00:14:43.310 --> 00:14:45.790
GPS satellites orbiting the ah, Earth

368
00:14:46.110 --> 00:14:48.110
allow you to work out your position on a

369
00:14:48.110 --> 00:14:50.990
basic level. Because at any time your device

370
00:14:51.550 --> 00:14:54.470
can, can see signals from a number of those

371
00:14:54.470 --> 00:14:56.670
satellites and

372
00:14:57.150 --> 00:14:59.870
figure out where they are. There are clocks

373
00:14:59.870 --> 00:15:01.390
on board all of them. You know, it can figure

374
00:15:01.390 --> 00:15:03.830
out the light travel time to get to it by

375
00:15:03.830 --> 00:15:05.550
seeing the time that they're broadcasting,

376
00:15:05.630 --> 00:15:08.110
knowing what your local time is, figuring out

377
00:15:08.110 --> 00:15:09.510
the difference between the two, you know, how

378
00:15:09.510 --> 00:15:11.830
far away the satellite is from one of them

379
00:15:11.830 --> 00:15:13.670
that places you at any point on a sphere

380
00:15:13.670 --> 00:15:14.950
around that satellite that is, uh, that

381
00:15:14.950 --> 00:15:17.110
distance away. From a second satellite,

382
00:15:17.110 --> 00:15:18.710
you've got another sphere on your way, they

383
00:15:18.710 --> 00:15:21.610
intersect, which gives you a line, and then

384
00:15:21.610 --> 00:15:23.490
a third one brings it down to a point. And

385
00:15:23.490 --> 00:15:25.090
the more you have, the more accurate you get.

386
00:15:26.050 --> 00:15:28.210
So this is all based on measurement of time,

387
00:15:29.330 --> 00:15:32.010
allowing you to measure distance for things

388
00:15:32.010 --> 00:15:35.010
that are a known distance away. This only

389
00:15:35.010 --> 00:15:37.330
works. So, uh, if you can take into account

390
00:15:37.330 --> 00:15:39.050
the way that the clocks are ticking at

391
00:15:39.050 --> 00:15:41.450
different speeds because the satellites are

392
00:15:41.450 --> 00:15:43.970
moving in orbit around the Earth, the

393
00:15:43.970 --> 00:15:45.330
difference, uh, including

394
00:15:46.440 --> 00:15:49.160
relativistic effects and time dilation into

395
00:15:49.160 --> 00:15:52.160
the calculations for GPS has, my

396
00:15:52.160 --> 00:15:54.280
understanding, is it's between a factor of 10

397
00:15:54.280 --> 00:15:56.880
and a factor of 100 on the precision with

398
00:15:56.880 --> 00:15:59.480
which your location can be calculated.

399
00:15:59.640 --> 00:16:01.640
And your GPS is usually good to probably

400
00:16:01.640 --> 00:16:03.720
about a metre. I think some of the modern

401
00:16:03.720 --> 00:16:05.880
ones are even more accurate than that. So if

402
00:16:05.880 --> 00:16:07.920
you imagine that, let's take the really

403
00:16:07.920 --> 00:16:09.680
optimistic case that you're only getting a

404
00:16:09.680 --> 00:16:11.080
factor of 10 improvement by including

405
00:16:11.080 --> 00:16:13.620
relativity at the minute, you've got an

406
00:16:13.620 --> 00:16:15.220
accuracy of one metre and that's good enough

407
00:16:15.220 --> 00:16:16.820
for you to navigate. With 10 metres, it

408
00:16:16.820 --> 00:16:19.060
probably wouldn't be. With 100 metres, it

409
00:16:19.060 --> 00:16:21.780
certainly wouldn't be. So our GPS

410
00:16:21.940 --> 00:16:24.180
systems only work

411
00:16:25.060 --> 00:16:27.380
because of our level of understanding of

412
00:16:27.380 --> 00:16:30.180
relativistic motion and of time dilation.

413
00:16:30.820 --> 00:16:33.300
So those satellites moving very, very quickly

414
00:16:33.460 --> 00:16:36.020
around the Earth are

415
00:16:36.020 --> 00:16:37.900
experiencing an M infinitesimally small

416
00:16:37.900 --> 00:16:39.460
amount of time dilation compared to the

417
00:16:39.460 --> 00:16:40.740
things they're broadcasting to on the

418
00:16:40.740 --> 00:16:43.130
surface. And we have to factor that in into

419
00:16:43.130 --> 00:16:45.770
our calculations to navigate. So your SAT nav

420
00:16:45.770 --> 00:16:48.450
wouldn't work without the theorems that

421
00:16:48.450 --> 00:16:50.450
Albert Einstein put together more than a

422
00:16:50.450 --> 00:16:53.410
century ago that are all about how things

423
00:16:53.410 --> 00:16:54.170
move through time.

424
00:16:54.170 --> 00:16:54.570
Andrew Dunkley: Yeah.

425
00:16:54.890 --> 00:16:57.050
Jonti Horner: So hopefully that has answered that question.

426
00:16:57.050 --> 00:16:59.850
I think. Rennie, I would be very tempted to

427
00:16:59.850 --> 00:17:01.530
suggest that at some point you try and get

428
00:17:01.530 --> 00:17:03.210
Friend to answer that as well, just to see

429
00:17:03.210 --> 00:17:06.170
where he took it. Um, but hopefully that at

430
00:17:06.170 --> 00:17:07.970
least is helpful. And like I say, if the

431
00:17:07.970 --> 00:17:09.770
relativistic stuff really interests you,

432
00:17:10.190 --> 00:17:11.950
space time physics, even though it's a book

433
00:17:11.950 --> 00:17:14.350
that was first published 60 years ago, I

434
00:17:14.350 --> 00:17:16.910
found invaluable in getting me through the

435
00:17:16.910 --> 00:17:18.710
exams and actually allowing me to get out of

436
00:17:18.710 --> 00:17:20.230
my first year and pass rather than being

437
00:17:20.230 --> 00:17:21.950
kicked out of uni. So it was a great book.

438
00:17:22.610 --> 00:17:25.110
Andrew Dunkley: Uh, Rennie might also like to Go on

439
00:17:25.110 --> 00:17:27.670
Wikipedia or any number of platforms and look

440
00:17:27.670 --> 00:17:30.350
up the twin paradox. That's a fun one. That's

441
00:17:30.350 --> 00:17:32.550
a great thought experiment. And I think there

442
00:17:32.550 --> 00:17:35.310
were twin astronauts that have,

443
00:17:35.530 --> 00:17:37.990
uh, had a little bit of a separation in age

444
00:17:37.990 --> 00:17:40.870
because one of them spent much more time in

445
00:17:40.870 --> 00:17:43.850
space than his bro. So um, their

446
00:17:43.930 --> 00:17:46.450
age difference uh, increased by

447
00:17:46.450 --> 00:17:48.650
8.6 milliseconds or something.

448
00:17:48.890 --> 00:17:51.130
Jonti Horner: Something like that I've seen. Really

449
00:17:51.130 --> 00:17:54.130
interesting. There are a couple of. Well,

450
00:17:54.130 --> 00:17:55.770
there are many science fiction books that

451
00:17:56.410 --> 00:17:58.250
play around this. I've spoken before about

452
00:17:58.250 --> 00:17:59.810
this series of science fiction books called

453
00:17:59.810 --> 00:18:02.290
the Mass Works of Science Fiction, which was

454
00:18:02.290 --> 00:18:03.850
an attempt by a publisher to make money

455
00:18:03.850 --> 00:18:06.330
obviously, but also to bring back some

456
00:18:06.330 --> 00:18:08.370
classic science fiction that is regarded as

457
00:18:08.370 --> 00:18:11.270
being very good. And you know, some of the

458
00:18:11.270 --> 00:18:12.910
things I read are very fun, but they're not

459
00:18:12.910 --> 00:18:14.670
necessarily very good. You know, there's

460
00:18:14.670 --> 00:18:16.310
always that side of things. And I'd say the

461
00:18:16.310 --> 00:18:18.070
Chrysalis books I'm reading at the minute the

462
00:18:18.390 --> 00:18:20.590
guy incarnated into the body of an ant,

463
00:18:20.590 --> 00:18:22.350
that's very good fun. I'm really loving it.

464
00:18:22.350 --> 00:18:24.150
But I wouldn't necessarily say they're high

465
00:18:24.150 --> 00:18:26.630
literature, they're fun. The um, Pratchett

466
00:18:26.630 --> 00:18:28.630
stuff is a bit of both. But these mass works

467
00:18:28.630 --> 00:18:31.270
of science fiction are often fascinating

468
00:18:31.270 --> 00:18:32.150
because they are

469
00:18:34.230 --> 00:18:36.190
quite often hard sci fi. So in other words,

470
00:18:36.190 --> 00:18:37.870
they're science fiction that is grounded in

471
00:18:37.870 --> 00:18:39.710
our understanding of science at the time they

472
00:18:39.710 --> 00:18:42.530
were written and tried to use uh, the

473
00:18:42.530 --> 00:18:45.330
laws of physics to help build the narrative

474
00:18:45.330 --> 00:18:47.290
rather than waving the laws of physics to

475
00:18:47.290 --> 00:18:48.930
allow the narrative. You know, there's a

476
00:18:48.930 --> 00:18:50.410
fundamental difference between the soft and

477
00:18:50.410 --> 00:18:53.250
woolly type I and the hard scientific sci fi.

478
00:18:53.570 --> 00:18:56.130
And two books in particular that leap to mind

479
00:18:56.130 --> 00:18:57.770
when we're talking about time dilation and

480
00:18:57.770 --> 00:19:00.250
relativity and things like that are uh, the

481
00:19:00.250 --> 00:19:02.890
Forever War by Joe Haberman, I think his name

482
00:19:02.890 --> 00:19:05.570
was. I'll just put that name up. The Forever

483
00:19:05.570 --> 00:19:07.890
War, um, was basically,

484
00:19:08.210 --> 00:19:11.170
yeah, Joe Halderman. Um, the idea that

485
00:19:11.170 --> 00:19:13.560
there is, um, written in

486
00:19:13.560 --> 00:19:16.080
1974, it's called Military science fiction.

487
00:19:16.400 --> 00:19:18.120
And um, the idea is humans are fighting an

488
00:19:18.120 --> 00:19:20.000
interstellar war against these alien

489
00:19:20.240 --> 00:19:22.440
civilization and they're sent off on

490
00:19:22.440 --> 00:19:24.080
missions, on spacecraft that travel at

491
00:19:24.080 --> 00:19:25.840
relativistic speed because it takes a hell of

492
00:19:25.840 --> 00:19:27.840
a long time to get anywhere. And it's not

493
00:19:27.840 --> 00:19:29.280
really about what they do when they get

494
00:19:29.280 --> 00:19:30.920
there, it's about what they do when they come

495
00:19:30.920 --> 00:19:32.360
back. Because the time you've gone there and

496
00:19:32.360 --> 00:19:35.040
come back, the Earth has moved on hugely. You

497
00:19:35.040 --> 00:19:37.120
know, you've been away for five years, but

498
00:19:37.830 --> 00:19:40.170
uh, Earth has skipped forward 100 years. Can

499
00:19:40.170 --> 00:19:43.130
you reintegrate how a society changed? And

500
00:19:43.130 --> 00:19:45.410
I think it's fair to say that without a

501
00:19:45.410 --> 00:19:48.370
spoiler, the motivation is, uh, you've more

502
00:19:48.370 --> 00:19:49.970
in common with the people you've lived that

503
00:19:49.970 --> 00:19:51.570
experience with than you do with everybody

504
00:19:51.570 --> 00:19:53.370
else. And it's all about

505
00:19:54.330 --> 00:19:57.050
that, grounded in this knowledge of

506
00:19:57.610 --> 00:20:00.290
time delay. Have travelled there and back

507
00:20:00.290 --> 00:20:01.570
again and come back to a world that has

508
00:20:01.570 --> 00:20:04.130
changed. The other one that really stuck in

509
00:20:04.130 --> 00:20:07.050
my mind as a interesting way to get

510
00:20:07.050 --> 00:20:08.610
your head around time dilation is a book

511
00:20:08.610 --> 00:20:11.250
called Tal's Era by Poole Anderson. And I

512
00:20:11.250 --> 00:20:12.770
think that was published even longer ago. I

513
00:20:12.770 --> 00:20:15.000
think it was probably in the 1950s. And, um,

514
00:20:15.010 --> 00:20:16.930
part of the reason I can say that is that

515
00:20:16.930 --> 00:20:19.730
that book, I believe, predates the

516
00:20:19.730 --> 00:20:22.530
Big Bang Theory, um, or, uh, it's around the

517
00:20:22.530 --> 00:20:25.170
time of the Big Bang Theory. It's, um, based

518
00:20:25.170 --> 00:20:27.170
on a short storey, published in 1967. The

519
00:20:27.170 --> 00:20:30.010
book itself was published in 1970. So it's

520
00:20:30.010 --> 00:20:32.690
a fabulous exploration

521
00:20:32.690 --> 00:20:35.370
of. It was actually post Big Bang, but it's

522
00:20:35.370 --> 00:20:38.010
a fabulous exploration of relativity in an

523
00:20:38.010 --> 00:20:40.050
unusual circumstance. In this case, it was

524
00:20:40.450 --> 00:20:43.050
people being the first humans to travel to

525
00:20:43.050 --> 00:20:45.770
the stars on a spaceship that was meant to go

526
00:20:45.770 --> 00:20:48.730
to a star and then come back and

527
00:20:48.730 --> 00:20:51.410
report, um, they were aiming to reach Beta

528
00:20:51.410 --> 00:20:54.330
Virginis. It says, crew of 50, 25 men,

529
00:20:54.330 --> 00:20:56.970
25 women, using something called a Bussad

530
00:20:56.970 --> 00:20:59.450
ramjet. So you have basically a rocket that

531
00:20:59.450 --> 00:21:01.840
scoops up fuel and burns it to go faster and

532
00:21:01.840 --> 00:21:04.760
faster. Right. Um, but there's a

533
00:21:04.760 --> 00:21:06.160
problem. They get up to high speed and then

534
00:21:06.160 --> 00:21:07.720
something breaks. But they're going so quick

535
00:21:07.720 --> 00:21:09.560
that they can't get outside of the spacecraft

536
00:21:09.880 --> 00:21:12.600
to fix it. And so they just have to go

537
00:21:12.600 --> 00:21:14.920
quicker and quicker. And so it

538
00:21:14.920 --> 00:21:17.640
explores this captive group of 50 people

539
00:21:18.200 --> 00:21:20.160
on an island in the universe that cannot

540
00:21:20.160 --> 00:21:23.040
stop, can only go quicker and quicker as the

541
00:21:23.040 --> 00:21:25.240
universe moves around them. And of course, by

542
00:21:25.240 --> 00:21:27.200
continually accelerating, they get closer and

543
00:21:27.200 --> 00:21:29.370
closer to the speed of light and time

544
00:21:29.370 --> 00:21:31.370
dilation impacts them more and more. So they

545
00:21:31.370 --> 00:21:34.090
see the universe to the end of the

546
00:21:34.090 --> 00:21:36.930
universe and beyond within a

547
00:21:36.930 --> 00:21:39.850
human lifetime. And, you know, the cosmology

548
00:21:39.850 --> 00:21:41.490
in it has changed. It was at a time where the

549
00:21:41.490 --> 00:21:43.330
Big Bang, a lot of people thought would end

550
00:21:43.330 --> 00:21:44.889
up in a Big Crunch. Everything will stop

551
00:21:44.889 --> 00:21:47.490
expanding, fall back together. But it's

552
00:21:47.490 --> 00:21:50.370
again, this awesome way of

553
00:21:50.370 --> 00:21:52.970
demonstrating how

554
00:21:53.290 --> 00:21:56.250
relativistic terms work. And the crew on the

555
00:21:56.250 --> 00:21:57.730
mission, before anything went wrong, were

556
00:21:57.730 --> 00:21:59.450
aware that when they returned to earth,

557
00:22:00.150 --> 00:22:02.870
something like 33 years would have passed

558
00:22:02.870 --> 00:22:04.430
before they get to their destination. They

559
00:22:04.430 --> 00:22:06.870
star but for them, only five years would have

560
00:22:06.870 --> 00:22:08.110
passed. So when they turn around and come

561
00:22:08.110 --> 00:22:10.230
home, they'll have aged 10 years, but 66

562
00:22:10.230 --> 00:22:11.590
years would have passed on Earth, give or

563
00:22:11.590 --> 00:22:12.230
take. Yeah.

564
00:22:12.230 --> 00:22:12.590
Andrew Dunkley: That's.

565
00:22:12.590 --> 00:22:14.870
Jonti Horner: In fact, that doesn't happen. Wonderful book.

566
00:22:14.950 --> 00:22:17.670
Andrew Dunkley: Yeah, I love those sorts of

567
00:22:17.670 --> 00:22:20.590
storeys. I love time travel, sci fi

568
00:22:20.590 --> 00:22:22.870
and uh, um, all those

569
00:22:23.910 --> 00:22:26.470
relativistic concepts. Uh, I,

570
00:22:26.870 --> 00:22:28.950
Yeah, I'm actually just finished writing a

571
00:22:28.950 --> 00:22:30.790
trilogy and I'm just getting it proofread at

572
00:22:30.790 --> 00:22:31.660
the moment. Um.

573
00:22:31.660 --> 00:22:32.230
Jonti Horner: Oh, fabulous.

574
00:22:32.230 --> 00:22:34.150
Andrew Dunkley: There's a little bit of that in it, but I'm

575
00:22:34.150 --> 00:22:35.190
not giving anything away.

576
00:22:35.910 --> 00:22:38.070
Jonti Horner: So maybe without, without any spoilers at

577
00:22:38.070 --> 00:22:40.590
all, that in a few years time maybe I'll be

578
00:22:40.590 --> 00:22:41.990
picking up your books as part of the

579
00:22:41.990 --> 00:22:43.190
masterworks of science fiction.

580
00:22:43.190 --> 00:22:45.870
Andrew Dunkley: You might. That'd be nice, wouldn't it?

581
00:22:45.870 --> 00:22:46.550
Jonti Horner: No pressure.

582
00:22:46.870 --> 00:22:48.470
Andrew Dunkley: No. Well, okay.

583
00:22:49.750 --> 00:22:52.110
Thanks, Rennie. Um, enjoyed that question.

584
00:22:52.110 --> 00:22:54.110
It's a, it's a fun one to talk about. This is

585
00:22:54.110 --> 00:22:56.110
Space Nuts with Andrew Dunkley and Professor

586
00:22:56.110 --> 00:22:56.790
Johnty H.

587
00:22:59.320 --> 00:23:01.160
I think we need to do a little more all

588
00:23:01.160 --> 00:23:03.800
weather testing. Amen, Space

589
00:23:03.800 --> 00:23:04.440
Nuts.

590
00:23:05.000 --> 00:23:07.680
Our next question, Jonty, comes from Paul in

591
00:23:07.680 --> 00:23:09.960
Brisbane. Although he, uh, doesn't call it

592
00:23:09.960 --> 00:23:11.840
Brisbane. You've probably heard this term

593
00:23:11.840 --> 00:23:14.759
because you live so close to Brisbane, but

594
00:23:14.760 --> 00:23:17.120
overseas people might think, what on earth is

595
00:23:17.120 --> 00:23:19.560
he talking about? G', day, Space Nuts. Paul,

596
00:23:19.800 --> 00:23:22.760
uh, from sunny Bris Vegas, uh, here.

597
00:23:23.080 --> 00:23:25.880
And he's thrown a challenge at me. Before I

598
00:23:25.880 --> 00:23:28.080
ask my question, could you read it in a

599
00:23:28.080 --> 00:23:30.850
Queensland accent to make it sound

600
00:23:30.850 --> 00:23:32.450
authentic? Andrew Tar.

601
00:23:33.650 --> 00:23:35.730
I'll give it a go, Paul, but you know, it's

602
00:23:35.730 --> 00:23:37.650
been a long time since I lived in Queensland.

603
00:23:38.130 --> 00:23:40.770
I was thinking, just listening in

604
00:23:40.930 --> 00:23:43.650
episode 681, when you and

605
00:23:43.650 --> 00:23:46.570
Fred Watson started talking, uh, about the

606
00:23:46.570 --> 00:23:48.930
possibility of Titan and Hypernian,

607
00:23:49.520 --> 00:23:52.370
uh, Hyperion collide and uh, thus creating

608
00:23:52.370 --> 00:23:54.530
Saturn's rings 100 million years ago.

609
00:23:55.730 --> 00:23:58.570
What do you reckon the odds are of

610
00:23:58.570 --> 00:24:01.010
some of the bigger blocks of the collision

611
00:24:01.090 --> 00:24:03.570
spinning off into space, uh, getting

612
00:24:03.970 --> 00:24:06.450
closer to the sun, I don't know, colliding

613
00:24:06.450 --> 00:24:09.170
with the Earth, say, 65 million years

614
00:24:09.170 --> 00:24:11.410
ago? Is that a possibility?

615
00:24:11.810 --> 00:24:14.609
Or does the chemical residue from

616
00:24:14.690 --> 00:24:17.290
on here on Earth, uh, suggest there's more

617
00:24:17.290 --> 00:24:19.570
likely to have been a comet?

618
00:24:19.810 --> 00:24:22.780
Curious to get your thoughts on this, eh? Uh,

619
00:24:22.780 --> 00:24:25.560
as always, keep up the great work and

620
00:24:25.560 --> 00:24:28.160
thank you. Was that

621
00:24:28.160 --> 00:24:29.240
Queenslandish enough?

622
00:24:30.380 --> 00:24:31.960
Jonti Horner: Uh, see, I struggled. So the accent thing.

623
00:24:31.960 --> 00:24:33.600
And again, we're very good at getting off

624
00:24:33.600 --> 00:24:33.920
topic.

625
00:24:33.920 --> 00:24:35.800
Andrew Dunkley: Or I am, it depends what part of Queensland

626
00:24:35.800 --> 00:24:36.760
though, because it's a big

627
00:24:36.760 --> 00:24:39.520
Jonti Horner: state for people listening and you've got to

628
00:24:39.520 --> 00:24:40.560
See, you've got to chuck in

629
00:24:40.560 --> 00:24:42.680
Andrew Dunkley: an A on the end of every sentence.

630
00:24:42.680 --> 00:24:44.680
Jonti Horner: One of the things that's always

631
00:24:45.400 --> 00:24:47.080
made my head hurt a little bit since I moved

632
00:24:47.080 --> 00:24:48.800
to Australia in 2010 and I'm officially

633
00:24:48.800 --> 00:24:51.410
Australian, you know. Yeah. Is a lack of

634
00:24:51.410 --> 00:24:53.690
diversity in the accents. I grew up in the

635
00:24:53.690 --> 00:24:56.650
uk, where accents are

636
00:24:56.650 --> 00:24:58.250
very, very varied to the extent that you

637
00:24:58.250 --> 00:24:59.730
could tell within my school which estate

638
00:24:59.730 --> 00:25:01.410
people grew up in because of subtleties in

639
00:25:01.410 --> 00:25:04.250
their accent locally. And the

640
00:25:04.250 --> 00:25:06.610
variation on a larger scale is astonishing.

641
00:25:06.610 --> 00:25:09.410
It's part of why I think British actors

642
00:25:09.570 --> 00:25:12.330
have so much success, partly because they

643
00:25:12.330 --> 00:25:14.050
get very good training, of course. But if

644
00:25:14.050 --> 00:25:16.410
you're an actor in the uk, you have to have a

645
00:25:16.410 --> 00:25:18.370
fluidity with accents because there's such a

646
00:25:18.370 --> 00:25:21.130
diversity just within the uk. Yeah. I came to

647
00:25:21.130 --> 00:25:23.990
Australia and I do not. I've

648
00:25:23.990 --> 00:25:26.190
lost some of my ear for the UK accents. I

649
00:25:26.190 --> 00:25:27.790
used to be really good, because you grow up

650
00:25:27.790 --> 00:25:29.230
there, it's a natural thing. I've lost a bit

651
00:25:29.230 --> 00:25:31.950
of that. But over here, it seems to be

652
00:25:32.350 --> 00:25:35.070
there isn't a very strong regional diversity.

653
00:25:35.070 --> 00:25:37.510
There's just a little bit of town versus

654
00:25:37.510 --> 00:25:39.430
country and a very little bit of north.

655
00:25:39.430 --> 00:25:39.750
South.

656
00:25:39.750 --> 00:25:40.110
Andrew Dunkley: Yes.

657
00:25:40.110 --> 00:25:42.590
Jonti Horner: But it's very smooth,

658
00:25:42.830 --> 00:25:44.270
although very little variety.

659
00:25:44.350 --> 00:25:47.140
Andrew Dunkley: I'll tell you. When I got into radio, I, um,

660
00:25:47.230 --> 00:25:50.030
did a demo tape and I had a friend listen to

661
00:25:50.030 --> 00:25:52.450
it who'd been in radio a very long time, and

662
00:25:52.450 --> 00:25:54.250
I was only just starting out, and he listened

663
00:25:54.250 --> 00:25:56.130
to it and he said, you know, you've got to

664
00:25:56.130 --> 00:25:58.410
get rid of. Rid of your Newcastle twang.

665
00:25:58.650 --> 00:26:00.670
Because I grew up in the Hunter Valley, um,

666
00:26:00.670 --> 00:26:03.290
in that Newcastle district. And I said, what?

667
00:26:03.290 --> 00:26:05.050
He said, you've got a Newcastle twang.

668
00:26:05.130 --> 00:26:08.130
There's a certain sound that comes

669
00:26:08.130 --> 00:26:10.090
out of the mouths of navocastrians.

670
00:26:11.050 --> 00:26:13.090
And I had to get. I had to train that out of

671
00:26:13.090 --> 00:26:15.970
myself. And. And it. It

672
00:26:15.970 --> 00:26:18.170
can be no disrespect, but it can be a bit

673
00:26:18.170 --> 00:26:20.740
grating. Um, but

674
00:26:22.820 --> 00:26:25.210
there are diversities in accent, uh,

675
00:26:25.740 --> 00:26:28.420
across Australia. When I worked for the abc,

676
00:26:28.420 --> 00:26:30.980
they actually published a map of accents,

677
00:26:31.620 --> 00:26:34.180
and I think the most prominent variation is

678
00:26:34.180 --> 00:26:36.980
South Australia, particularly Adelaide. Much

679
00:26:36.980 --> 00:26:38.660
more posh.

680
00:26:39.460 --> 00:26:42.140
Jonti Horner: But it's also, to me, it's much more evidence

681
00:26:42.140 --> 00:26:43.660
because I just don't quite have the ear for

682
00:26:43.660 --> 00:26:45.740
it, because in the uk, the accents are very

683
00:26:45.740 --> 00:26:47.900
much more valid. So Newcastle accent, to me,

684
00:26:47.900 --> 00:26:49.220
is very different to what you think of a

685
00:26:49.220 --> 00:26:51.680
Newcastle accent, but where I see it is in

686
00:26:51.680 --> 00:26:54.440
language. So there's the perennial

687
00:26:54.440 --> 00:26:56.480
argument among Australians of whether it's a

688
00:26:56.480 --> 00:26:58.920
potato cap or a potato scholar. Is A good

689
00:26:58.920 --> 00:27:00.440
example. You've got regional things like

690
00:27:00.440 --> 00:27:03.440
that. And from my side of things, I worked

691
00:27:03.440 --> 00:27:06.040
in Switzerland for three years and shared an

692
00:27:06.040 --> 00:27:08.560
office with Hagar, who was this

693
00:27:08.960 --> 00:27:11.600
young woman from, I think, Iran or somewhere

694
00:27:11.600 --> 00:27:13.880
Persian, I'm not sure exactly where. But we

695
00:27:13.880 --> 00:27:16.480
communicated in English, which was her sixth

696
00:27:16.710 --> 00:27:17.110
language.

697
00:27:17.110 --> 00:27:17.550
Andrew Dunkley: Wow.

698
00:27:17.550 --> 00:27:20.510
Jonti Horner: Which was astonishing to me. But there

699
00:27:20.510 --> 00:27:21.870
was one time I've been on the phone to my

700
00:27:21.870 --> 00:27:23.390
parents and I finished and she said, so,

701
00:27:23.390 --> 00:27:25.830
Jonty, what does A up mean? And

702
00:27:26.150 --> 00:27:28.990
yeah, ay up. Um, it

703
00:27:28.990 --> 00:27:30.150
reminds me of the wonderful.

704
00:27:30.150 --> 00:27:31.750
Andrew Dunkley: Isn't that Liverpudlian, that.

705
00:27:31.830 --> 00:27:34.790
Jonti Horner: No, AUP's. Yorkshire as well. M not far.

706
00:27:34.950 --> 00:27:37.550
If you want to see the accent of roughly

707
00:27:37.550 --> 00:27:39.470
where I grew up, incidentally, it's worth

708
00:27:39.470 --> 00:27:42.190
people looking up the fabulous song Ilklim al

709
00:27:42.190 --> 00:27:44.590
bar Tat, which is a cultural treasure from my

710
00:27:44.590 --> 00:27:45.910
part of the world. And we all learned, um,

711
00:27:45.910 --> 00:27:47.940
when we were in scouts and at school. And

712
00:27:47.940 --> 00:27:50.540
it's, um, basically a group of. Group of

713
00:27:50.540 --> 00:27:52.020
fellows at the pub saying, where have you

714
00:27:52.020 --> 00:27:53.580
been since I saw you last? You've been.

715
00:27:53.660 --> 00:27:55.740
You've been caught in Mary Jane. And it goes

716
00:27:55.740 --> 00:27:57.900
on about how he's not being dressed

717
00:27:57.900 --> 00:27:59.180
appropriately, he's going to die and they'll

718
00:27:59.180 --> 00:27:59.860
have to bury him.

719
00:27:59.860 --> 00:28:00.140
Andrew Dunkley: And.

720
00:28:00.140 --> 00:28:02.380
Jonti Horner: But it's all in very strong dialect, so you

721
00:28:02.380 --> 00:28:04.300
can see that. But what that resulted in is

722
00:28:04.860 --> 00:28:07.580
everybody in Bern communicated in

723
00:28:07.580 --> 00:28:09.420
English. At, uh, the Physicalisches

724
00:28:09.420 --> 00:28:11.180
Institute, I had to speak German when I was

725
00:28:11.180 --> 00:28:14.110
out in the town. But English has

726
00:28:14.110 --> 00:28:16.390
become this kind of lingua franca. Lingua,

727
00:28:16.390 --> 00:28:18.470
Lingua franca there. Because

728
00:28:18.870 --> 00:28:20.350
Switzerland's country with four different

729
00:28:20.350 --> 00:28:22.270
languages, it's got French, German, Italian

730
00:28:22.270 --> 00:28:24.630
and Romansh, but everybody's proud of their

731
00:28:24.630 --> 00:28:27.470
language. The French speakers will not sully

732
00:28:27.470 --> 00:28:29.750
themselves by speaking German to the German

733
00:28:29.750 --> 00:28:31.710
speakers. The German speakers, therefore,

734
00:28:31.710 --> 00:28:33.390
will not sully themselves by speaking the

735
00:28:33.390 --> 00:28:36.030
foul French to the French speakers. So they

736
00:28:36.030 --> 00:28:38.920
speak English. Um,

737
00:28:39.040 --> 00:28:41.080
but that means people have very good English,

738
00:28:41.080 --> 00:28:42.200
but they've learned a lot of their English

739
00:28:42.200 --> 00:28:44.640
from watching American TV rather than British

740
00:28:44.640 --> 00:28:47.400
tv. But even the British TV is a little bit

741
00:28:47.400 --> 00:28:49.920
denuded in terms of accent

742
00:28:50.240 --> 00:28:52.560
and, um, in terms

743
00:28:52.560 --> 00:28:54.320
particularly of dialect terms.

744
00:28:56.080 --> 00:28:57.680
And it was to an extent we were talking about

745
00:28:57.680 --> 00:28:59.640
the accents. The news presenters, until about

746
00:28:59.640 --> 00:29:02.120
20 or 30 years ago on the BBC had to use

747
00:29:02.120 --> 00:29:04.160
received pronunciation, which is a Queen's

748
00:29:04.160 --> 00:29:06.000
English, and you have to speak very properly.

749
00:29:06.000 --> 00:29:07.880
And they got rid of that because people

750
00:29:07.880 --> 00:29:09.640
realised that actually diversity in accents

751
00:29:09.640 --> 00:29:11.280
represents a diversity of people. And that's

752
00:29:11.280 --> 00:29:13.560
great. What that meant, though, was,

753
00:29:13.610 --> 00:29:16.240
uh, my accent, I've reliably been told, is

754
00:29:16.240 --> 00:29:19.120
relatively Strong. But I don't really use

755
00:29:19.120 --> 00:29:21.120
any dialect terms anymore other than the old

756
00:29:21.120 --> 00:29:23.200
bit of Aussie stuff I've picked up. Because

757
00:29:23.200 --> 00:29:24.480
what was really throwing people in

758
00:29:24.480 --> 00:29:27.440
Switzerland was the dialect terms, not

759
00:29:27.440 --> 00:29:30.400
the accents. Things like A up. And, um. So my

760
00:29:30.400 --> 00:29:32.080
language has shifted. I've lost a bit of an A

761
00:29:32.080 --> 00:29:34.710
for the UK stuff, but I don't hear much

762
00:29:35.270 --> 00:29:37.550
variety in the Australian accent. Now. Part

763
00:29:37.550 --> 00:29:39.270
of that is because I'm not from here,

764
00:29:40.310 --> 00:29:42.790
but I, I always find that kind of stuff

765
00:29:42.790 --> 00:29:44.510
really, really interesting. So, I mean, I

766
00:29:44.510 --> 00:29:45.950
could tell you were getting a stronger

767
00:29:45.950 --> 00:29:48.790
Australian accent. Um, but it wasn't

768
00:29:48.790 --> 00:29:50.550
necessarily. I couldn't have told you where

769
00:29:50.550 --> 00:29:53.390
it was from. Um, other thing is, again,

770
00:29:53.390 --> 00:29:55.110
saw an interesting discussion online about

771
00:29:55.110 --> 00:29:56.950
the Australia accent changing over time,

772
00:29:57.270 --> 00:30:00.160
asking why, when you watch Aussie films and

773
00:30:00.160 --> 00:30:02.400
TVs from 30, 40, 50 years ago,

774
00:30:02.720 --> 00:30:04.080
everybody almost sounds like they're a

775
00:30:04.080 --> 00:30:06.160
pastiche of the Australian accent. It's so

776
00:30:06.480 --> 00:30:09.080
full on and there's so many terms and

777
00:30:09.080 --> 00:30:10.720
insults and stuff that aren't, um, used

778
00:30:10.720 --> 00:30:13.520
today. Yeah. And, um, apparently part of it

779
00:30:13.520 --> 00:30:15.920
is language evolves. We've got all these

780
00:30:15.920 --> 00:30:17.720
multicultural influence, we've got all that

781
00:30:17.720 --> 00:30:20.240
stuff. But also apparently the actors were

782
00:30:20.880 --> 00:30:22.160
trained to ham it up.

783
00:30:22.240 --> 00:30:25.120
Andrew Dunkley: Oh, absolutely. That's exactly what it was.

784
00:30:25.120 --> 00:30:27.630
And, uh. See what you started, Paul. But,

785
00:30:27.630 --> 00:30:30.260
uh, I understand because I did some research

786
00:30:30.260 --> 00:30:32.620
on it. The Australian accent came about

787
00:30:32.700 --> 00:30:34.610
because we were, uh,

788
00:30:35.580 --> 00:30:38.540
a colony of convicts brought over from the

789
00:30:38.540 --> 00:30:41.500
uk. But the convicts were all from

790
00:30:41.500 --> 00:30:43.060
different walks of life, but they were

791
00:30:43.060 --> 00:30:46.060
conglomerated into a new community and

792
00:30:46.140 --> 00:30:48.980
all their accents merged into what is now the

793
00:30:48.980 --> 00:30:49.900
Australian accent.

794
00:30:49.980 --> 00:30:52.820
So, you know, you

795
00:30:52.820 --> 00:30:55.460
had Welsh, you had Irish, you had Scottish,

796
00:30:55.460 --> 00:30:57.700
you had English, of. With all their

797
00:30:57.700 --> 00:31:00.420
variations all coming together and

798
00:31:00.420 --> 00:31:02.380
creating the Australian accent. So that's why

799
00:31:02.380 --> 00:31:03.140
it is what it is.

800
00:31:03.620 --> 00:31:04.100
Jonti Horner: Yes.

801
00:31:04.180 --> 00:31:05.700
Andrew Dunkley: But it's ever evolving too.

802
00:31:05.700 --> 00:31:07.500
Jonti Horner: It is a wonderful thing that does change over

803
00:31:07.500 --> 00:31:09.780
time. Yes. Which I found interesting. Anyway,

804
00:31:09.860 --> 00:31:10.580
sorry about that.

805
00:31:10.660 --> 00:31:12.540
We get off topic. Wonderfully, wonderfully.

806
00:31:12.540 --> 00:31:13.260
Well, Saturn.

807
00:31:13.260 --> 00:31:14.860
Andrew Dunkley: Good at that. So Fred Watson started talking

808
00:31:14.860 --> 00:31:17.180
about the possibility of Titan and Hyperion

809
00:31:17.180 --> 00:31:19.780
colliding and what happened to the stuff.

810
00:31:19.780 --> 00:31:22.420
Could a big rock from that event have hit

811
00:31:22.420 --> 00:31:24.380
Earth 65 million years ago? And you know what

812
00:31:24.380 --> 00:31:26.220
he's talking about there? Or did it all just

813
00:31:26.220 --> 00:31:28.300
go flying off into space or did it do

814
00:31:28.300 --> 00:31:30.160
something, something else, etc. Etc.

815
00:31:30.800 --> 00:31:33.120
Jonti Horner: All sorts of ways we can go with this. So

816
00:31:34.000 --> 00:31:36.320
the origin of Saturn's rings, first and

817
00:31:36.320 --> 00:31:39.240
foremost is not yet definitively known.

818
00:31:39.240 --> 00:31:41.360
We know that the ruin systems around Jupiter,

819
00:31:41.360 --> 00:31:44.080
Uranus and Neptune as well. We suspect

820
00:31:44.080 --> 00:31:45.920
strongly that in the past and in the future

821
00:31:46.240 --> 00:31:49.200
Mars has had and will have ring

822
00:31:49.440 --> 00:31:52.080
rings. I think red dwarfy has, will have,

823
00:31:52.080 --> 00:31:54.780
possibly going to have whatever it is, it may

824
00:31:54.780 --> 00:31:56.740
have had episodic rings. In the past we found

825
00:31:56.740 --> 00:31:58.420
rings around a few of the solar system

826
00:31:58.420 --> 00:32:00.980
smaller objects like um, the Centaurs, Chiron

827
00:32:00.980 --> 00:32:03.980
and Curricula, um, rings are a thing.

828
00:32:03.980 --> 00:32:05.900
We've also found potentially rings around

829
00:32:05.900 --> 00:32:08.140
exoplanets. Some debate about that. We find

830
00:32:08.140 --> 00:32:10.500
rings around stars in the form of debris

831
00:32:10.500 --> 00:32:13.420
discs and all the rest of it. Ever

832
00:32:13.420 --> 00:32:16.340
since Saturn's rings were known there's been

833
00:32:16.500 --> 00:32:19.420
ongoing how did they get there? And there is

834
00:32:19.420 --> 00:32:21.330
an ongoing not only how did they get there,

835
00:32:21.330 --> 00:32:23.450
but are they transient or permanent? And

836
00:32:24.330 --> 00:32:27.210
there are a wide variety of opinions on this

837
00:32:27.210 --> 00:32:29.250
and modelling has not yet come down strongly

838
00:32:29.250 --> 00:32:32.050
one way or the other. Currently the best

839
00:32:32.050 --> 00:32:33.890
thinking about Saturn's rings is that they

840
00:32:33.890 --> 00:32:36.810
are more likely to be new than old.

841
00:32:37.530 --> 00:32:40.450
So we're probably seeing a ring system that

842
00:32:40.450 --> 00:32:43.130
has in bulk not existed since the birth of

843
00:32:43.130 --> 00:32:45.810
the Sol system. And estimates of the age

844
00:32:45.810 --> 00:32:48.570
range from 10 to 100 to

845
00:32:49.130 --> 00:32:52.010
300 million years. These estimates on the

846
00:32:52.250 --> 00:32:54.250
which the rings are being depleted

847
00:32:54.970 --> 00:32:57.010
suggest that they may well return to the

848
00:32:57.010 --> 00:32:59.930
level of Neptune, Uranus, Jupiter type rings

849
00:33:00.250 --> 00:33:02.410
within about 300 million years from now.

850
00:33:03.370 --> 00:33:06.170
Those theories, those arguments

851
00:33:07.050 --> 00:33:09.010
would suggest that if the ring system is

852
00:33:09.010 --> 00:33:10.490
younger than the edge of the solar system,

853
00:33:10.490 --> 00:33:12.090
there had to be an event to bring it into

854
00:33:12.090 --> 00:33:14.710
being. Obviously and there have been

855
00:33:14.710 --> 00:33:17.470
a number of different suggestions to

856
00:33:17.470 --> 00:33:19.430
cause this. One is that, and this was

857
00:33:19.750 --> 00:33:21.630
commonly argued when I was a kid learning

858
00:33:21.630 --> 00:33:23.310
about it, that Saturn had a commodore

859
00:33:23.310 --> 00:33:25.830
asteroid that got too close was Taunus under

860
00:33:25.830 --> 00:33:28.629
creating the rings. Now this invokes

861
00:33:28.629 --> 00:33:30.830
a part of planetary science knowledge and

862
00:33:30.830 --> 00:33:33.270
physics called the Roche limit, which is

863
00:33:33.270 --> 00:33:35.990
essentially if you have two massive objects

864
00:33:36.230 --> 00:33:37.990
and you bring them close enough together,

865
00:33:38.600 --> 00:33:41.200
tidal effects will disrupt the smaller of

866
00:33:41.200 --> 00:33:43.920
them due to the gravity of the bigger of

867
00:33:43.920 --> 00:33:45.800
them. And the point there is if you think

868
00:33:45.800 --> 00:33:47.640
that the strength of the gravitational pull

869
00:33:47.640 --> 00:33:49.920
falls off as the square of the distance and

870
00:33:49.920 --> 00:33:51.680
you've got an object that's 100 kilometres

871
00:33:51.680 --> 00:33:54.239
across, the side that is nearer a planet will

872
00:33:54.239 --> 00:33:55.720
be feeling a stronger pull than the side

873
00:33:55.720 --> 00:33:58.320
that's further away. Now depending on the

874
00:33:58.320 --> 00:34:01.040
strength of the object that distance will

875
00:34:01.040 --> 00:34:02.960
vary. The stronger the object is, the closer

876
00:34:02.960 --> 00:34:05.900
it can get to a planet before disruption. But

877
00:34:05.900 --> 00:34:07.540
we have this concept of the Roche limit and

878
00:34:07.540 --> 00:34:09.540
Saturn's rings are within the Roche limit

879
00:34:09.540 --> 00:34:11.740
which is why they've been disrupted. And the

880
00:34:11.740 --> 00:34:14.540
largest objects in them are uh, probably to

881
00:34:14.540 --> 00:34:16.380
be honest the shepherd moons that are

882
00:34:16.380 --> 00:34:19.140
kilometre scale objects which are probably

883
00:34:19.620 --> 00:34:21.300
due to the nature of the Roche limit and

884
00:34:21.300 --> 00:34:24.260
stuff. They're probably fairly robust

885
00:34:24.260 --> 00:34:25.940
rather than rubble piles. Because if they're

886
00:34:25.940 --> 00:34:27.460
rubble piles, they get disintegrated.

887
00:34:27.460 --> 00:34:27.899
Andrew Dunkley: Yeah. Um.

888
00:34:28.340 --> 00:34:30.260
Jonti Horner: So they're probably at a distance where they

889
00:34:30.260 --> 00:34:33.080
are within the Roche limit. For a fluid

890
00:34:33.080 --> 00:34:34.680
object that has no strength, but they are

891
00:34:34.680 --> 00:34:36.160
strong enough that the Roche limit for them

892
00:34:36.160 --> 00:34:37.760
will be closer in Anyway. A bit off topic

893
00:34:37.760 --> 00:34:40.280
there, but that's the physics behind it. And

894
00:34:40.280 --> 00:34:42.160
you can work out that Roche limit either as a

895
00:34:42.160 --> 00:34:44.440
ratio of the mass of the object and the mass

896
00:34:44.440 --> 00:34:46.240
of the thing it's the bigger thing that it's

897
00:34:46.240 --> 00:34:48.080
coming near, or as a ratio of the densities.

898
00:34:48.720 --> 00:34:50.960
It works either way, which is kind of cool.

899
00:34:51.579 --> 00:34:53.840
Um, that's

900
00:34:54.320 --> 00:34:57.240
what the physics is behind why

901
00:34:57.240 --> 00:34:58.880
you don't have a single object there. It

902
00:34:58.880 --> 00:35:00.440
can't form single object. It's got to be

903
00:35:00.830 --> 00:35:03.350
broken up into debris. The rings are

904
00:35:03.350 --> 00:35:06.150
decaying, dust is lost to Saturn all the

905
00:35:06.150 --> 00:35:08.110
time. They're also being slightly replenished

906
00:35:08.110 --> 00:35:10.270
by the activity, particularly of Enceladus,

907
00:35:10.780 --> 00:35:13.390
um, which is repopulating the earring. So

908
00:35:13.390 --> 00:35:16.230
there are system influx and it's not

909
00:35:16.230 --> 00:35:18.350
clear exactly where they're formed. There was

910
00:35:18.350 --> 00:35:20.190
the idea when I was a kid that it was a

911
00:35:20.190 --> 00:35:22.310
commodore asteroid that was disrupted to make

912
00:35:22.310 --> 00:35:25.150
that much material. I think that has gone

913
00:35:25.470 --> 00:35:28.340
probably by the wayside because you

914
00:35:28.340 --> 00:35:30.940
need a way to dissipate the energy for an

915
00:35:30.940 --> 00:35:33.660
object to be captured. So if you have a comet

916
00:35:33.660 --> 00:35:35.460
or an asteroid get close enough to Saturn to

917
00:35:35.460 --> 00:35:38.220
be torn apart, that material is still

918
00:35:38.220 --> 00:35:40.020
moving faster than Saturn's escape velocity.

919
00:35:40.020 --> 00:35:42.260
So we'll just fly away, albeit torn apart.

920
00:35:42.260 --> 00:35:42.660
Andrew Dunkley: Right.

921
00:35:42.980 --> 00:35:44.900
Jonti Horner: If you have something that is temporarily

922
00:35:44.900 --> 00:35:47.820
captured as a satellite, it'll be on a fairly

923
00:35:47.820 --> 00:35:49.540
elongated orbit. If it's going to get close

924
00:35:49.540 --> 00:35:51.660
enough to be disrupted and it will continue

925
00:35:51.660 --> 00:35:53.100
to follow that. So if you look at Comet

926
00:35:53.100 --> 00:35:55.470
Schumacher, Levy 9 back in the

927
00:35:55.470 --> 00:35:58.470
1990s, it came very close to Jupiter in 1992,

928
00:35:58.470 --> 00:36:00.990
I think was torn apart so that we had many

929
00:36:00.990 --> 00:36:03.150
smaller comets that all followed essentially

930
00:36:03.150 --> 00:36:05.750
the same art orbit. Ah. In a lengthy chain

931
00:36:05.910 --> 00:36:08.670
and fell apart, crashed into Jupiter one

932
00:36:08.670 --> 00:36:10.309
after the other over the space of a couple of

933
00:36:10.309 --> 00:36:11.390
weeks in 1994.

934
00:36:11.390 --> 00:36:11.990
Andrew Dunkley: That's right.

935
00:36:12.630 --> 00:36:13.990
Jonti Horner: They didn't form a ring system.

936
00:36:14.550 --> 00:36:14.910
Andrew Dunkley: No.

937
00:36:14.910 --> 00:36:17.350
Jonti Horner: When that had its first approach to Jupiter,

938
00:36:17.350 --> 00:36:19.910
it was torn apart, but it didn't make a new

939
00:36:19.910 --> 00:36:22.070
ring system. So you need somewhere to

940
00:36:22.070 --> 00:36:23.750
dissipate the energy to trap all the debris

941
00:36:23.750 --> 00:36:26.030
onto a circular orbit near the planet. And

942
00:36:26.030 --> 00:36:27.790
it's very hard to visualise how you do that

943
00:36:27.790 --> 00:36:30.470
from an asteroid or comet passing through. So

944
00:36:30.470 --> 00:36:33.350
that's led to uh, instead the idea of

945
00:36:33.590 --> 00:36:35.950
the collision between two moons. Now the most

946
00:36:35.950 --> 00:36:38.870
recent version I've seen discussed of this

947
00:36:39.270 --> 00:36:41.670
is that uh, there was a moon

948
00:36:42.150 --> 00:36:44.950
that was possibly as large as Hyperion or

949
00:36:44.950 --> 00:36:47.560
even bigger, that collided

950
00:36:48.680 --> 00:36:51.400
sorry whose orbit spiralled inwards to the

951
00:36:51.400 --> 00:36:54.120
point it crossed the Roche limit. Now we're

952
00:36:54.120 --> 00:36:56.640
seeing this happen with Phoebe, the innermost

953
00:36:56.640 --> 00:36:59.560
of Mars 2 moons. Phoebe is closer to Mars

954
00:36:59.560 --> 00:37:02.440
than what we call the CO rotation altitude,

955
00:37:02.680 --> 00:37:05.240
which means its orbit around Mars takes less

956
00:37:05.240 --> 00:37:07.720
time than Mars takes to spin. And when you're

957
00:37:07.720 --> 00:37:09.760
closer than that corrotation place, tidal

958
00:37:09.760 --> 00:37:11.720
forces will make you spiral inwards rather

959
00:37:11.720 --> 00:37:13.360
than spiralling outwards. Our moons further

960
00:37:13.360 --> 00:37:15.590
out, it takes longer to orbit the Earth than

961
00:37:15.590 --> 00:37:17.830
the Earth takes to spin. So it moves away.

962
00:37:17.910 --> 00:37:18.390
Andrew Dunkley: Yeah.

963
00:37:19.270 --> 00:37:21.670
Jonti Horner: Imagine then that you had a moon

964
00:37:22.070 --> 00:37:24.630
few hundred kilometres across, 200, 300, 400

965
00:37:24.630 --> 00:37:27.510
kilometres across, close end that

966
00:37:27.510 --> 00:37:29.510
spiralled inwards and crossed the Roche

967
00:37:29.510 --> 00:37:31.150
limit. It will be disrupted from a ring

968
00:37:31.150 --> 00:37:33.870
system. That's one theory. Another is that

969
00:37:33.870 --> 00:37:36.510
you had a moon that was pretty close in that

970
00:37:36.510 --> 00:37:39.190
was then struck by an object large enough to

971
00:37:39.190 --> 00:37:41.280
shatter and disrupt it.

972
00:37:42.000 --> 00:37:44.960
But collisions of that size would

973
00:37:44.960 --> 00:37:46.520
be relatively rare these days because

974
00:37:46.520 --> 00:37:48.560
projectiles big enough to shatter a moon of

975
00:37:48.560 --> 00:37:51.440
that size are relatively scarce.

976
00:37:52.070 --> 00:37:54.360
Um, a more, more recent version that's been

977
00:37:54.360 --> 00:37:56.920
proposed is that you had a much larger

978
00:37:56.920 --> 00:37:59.120
object, something more like the size of Titan

979
00:37:59.440 --> 00:38:01.640
and that was stripped off during the

980
00:38:01.640 --> 00:38:03.480
formation period of time. There's all sorts

981
00:38:03.480 --> 00:38:06.000
of theories here but like I said, we're not

982
00:38:06.250 --> 00:38:07.850
fully there yet. We're still exploring.

983
00:38:08.250 --> 00:38:10.770
That's where future missions to Saturn are

984
00:38:10.770 --> 00:38:13.370
going to teach us a lot more. Um, we've got

985
00:38:13.370 --> 00:38:16.130
an edge here. Um, observations based on the

986
00:38:16.130 --> 00:38:18.970
Keck telescope suggest that the rings

987
00:38:18.970 --> 00:38:21.130
will be gone in 292

988
00:38:21.610 --> 00:38:24.530
plus 818 minus 124 million

989
00:38:24.530 --> 00:38:26.770
years. Which illustrates that as astronomers

990
00:38:26.770 --> 00:38:29.050
we are terrible at, ah, choosing significant

991
00:38:29.050 --> 00:38:30.770
figures. And I tell my students this all the

992
00:38:30.770 --> 00:38:32.810
time because if you talk to a physicist

993
00:38:32.810 --> 00:38:34.850
they'd see those numbers and weep because

994
00:38:34.850 --> 00:38:36.930
they'd say, well that should just be 300 plus

995
00:38:36.930 --> 00:38:39.030
800 minus 1 because the other numbers are

996
00:38:39.030 --> 00:38:41.950
meaningless anyway. Um, but it's

997
00:38:41.950 --> 00:38:44.150
a very large uncertainty on how long they

998
00:38:44.150 --> 00:38:46.510
will take till they're gone. We don't know

999
00:38:46.510 --> 00:38:49.230
how massive they were initially and how

1000
00:38:49.230 --> 00:38:52.110
massive they are initially will be part

1001
00:38:52.110 --> 00:38:54.990
of what determines how long they've

1002
00:38:54.990 --> 00:38:57.870
been around anyway. So that's why

1003
00:38:57.870 --> 00:38:59.670
there's still a lot of misunderstanding and a

1004
00:38:59.670 --> 00:39:01.910
lot of confusion there. And it may well be

1005
00:39:01.910 --> 00:39:04.230
that rings of the scale of the rings of

1006
00:39:04.230 --> 00:39:05.830
Saturn around the giant planets are an

1007
00:39:05.830 --> 00:39:08.150
episodic thing. It may well be the

1008
00:39:08.620 --> 00:39:10.940
planets like Saturn, Jupiter, uh, Uranus and

1009
00:39:10.940 --> 00:39:13.620
Neptune have minor ring systems all the time,

1010
00:39:13.620 --> 00:39:15.260
but occasionally will get a really good one.

1011
00:39:15.260 --> 00:39:17.100
And it could be that in the past Jupiter had

1012
00:39:17.100 --> 00:39:19.340
a massive ring system like this and in the

1013
00:39:19.340 --> 00:39:21.820
future Uranus back, for example,

1014
00:39:22.140 --> 00:39:24.580
Mars will probably get a ring system when um,

1015
00:39:24.580 --> 00:39:26.620
Phobos gets close enough and is disrupted.

1016
00:39:27.580 --> 00:39:29.900
All that now to aside, the next part was

1017
00:39:30.060 --> 00:39:32.860
about debris reaching us from

1018
00:39:33.100 --> 00:39:36.010
the collision and reaching the Earth.

1019
00:39:36.170 --> 00:39:38.810
Yeah, um, two parts to this. The first is

1020
00:39:38.810 --> 00:39:41.450
that some

1021
00:39:41.850 --> 00:39:43.890
material from that collision could

1022
00:39:43.890 --> 00:39:45.650
potentially have reached Earth. I don't doubt

1023
00:39:45.650 --> 00:39:47.890
that. I did work while I was at the

1024
00:39:47.890 --> 00:39:49.530
University of Bern, which we talked about

1025
00:39:49.530 --> 00:39:52.290
earlier with a PhD student at the time called

1026
00:39:52.290 --> 00:39:55.130
Augustine Anich, who was doing simulations

1027
00:39:55.210 --> 00:39:58.170
of the giant collision that made Mercury

1028
00:39:58.170 --> 00:40:00.730
the planet we know it is today. Mercury is

1029
00:40:00.810 --> 00:40:03.570
over dense, it has an oversized core. And the

1030
00:40:03.570 --> 00:40:05.450
thinking is it was probably once a planet

1031
00:40:05.450 --> 00:40:08.290
twice the diameter of the current Mercury.

1032
00:40:08.290 --> 00:40:10.410
And it had this massive collision that

1033
00:40:10.410 --> 00:40:12.210
stripped it of its mantle and crust, leaving

1034
00:40:12.210 --> 00:40:13.850
behind a core with a little bit of rubble on

1035
00:40:13.850 --> 00:40:16.330
top. And he was doing simulations of that

1036
00:40:16.330 --> 00:40:19.290
impact. And my contribution

1037
00:40:19.290 --> 00:40:21.490
was I ran orbital mechanics simulations. This

1038
00:40:21.490 --> 00:40:23.690
is kind of core to my day to day work. This

1039
00:40:23.690 --> 00:40:26.330
is what I've done all through my career. And

1040
00:40:26.330 --> 00:40:29.100
I said where would the ejector go? If you

1041
00:40:29.100 --> 00:40:30.900
have a collision like that, some of the

1042
00:40:30.900 --> 00:40:33.020
material ejected will be travelling at less

1043
00:40:33.020 --> 00:40:34.700
than the escape velocity for all of the

1044
00:40:34.700 --> 00:40:36.580
masses around. So that material won't be

1045
00:40:36.580 --> 00:40:39.020
lost. And it would either in the case of the

1046
00:40:39.020 --> 00:40:40.740
Earth Moon collision, form a satellite like

1047
00:40:40.740 --> 00:40:43.260
the Moon or fall back and contribute to the

1048
00:40:43.260 --> 00:40:46.100
re accretion. Material travelling

1049
00:40:46.100 --> 00:40:49.100
above the escape velocity will escape and

1050
00:40:49.100 --> 00:40:51.140
go into orbit around the Sun. And at that

1051
00:40:51.140 --> 00:40:53.260
point it is subject to all of the dynamics

1052
00:40:53.260 --> 00:40:54.950
that goes on, the gravity, gravitational

1053
00:40:54.950 --> 00:40:57.230
interactions with all the other planets. And

1054
00:40:57.230 --> 00:40:59.550
I run simulations of the ejector to see what

1055
00:40:59.550 --> 00:41:01.870
their eventual fates would be, where they

1056
00:41:01.870 --> 00:41:04.230
would wind up. The majority of the ejector

1057
00:41:04.230 --> 00:41:06.350
from the Mercury forming collision hit the

1058
00:41:06.350 --> 00:41:09.110
sun or was flung from the solar system, never

1059
00:41:09.110 --> 00:41:11.550
to return as a final fate. That's where it

1060
00:41:11.550 --> 00:41:13.910
ended up. But about 2% of the material

1061
00:41:13.910 --> 00:41:16.030
ejected from Mercury would have landed on

1062
00:41:16.030 --> 00:41:18.670
Earth. So we will have been polluted by the

1063
00:41:18.670 --> 00:41:21.360
Mercury forming impact by what you

1064
00:41:21.360 --> 00:41:23.840
describe as Hermian material. If, if we were

1065
00:41:23.840 --> 00:41:26.680
talking about Venus being venereal

1066
00:41:27.160 --> 00:41:29.560
material which then became Venusian material,

1067
00:41:29.560 --> 00:41:32.280
Mars being Martian, Jupiter being Jovian

1068
00:41:32.600 --> 00:41:35.480
for Mercury, Mercurian never quite worked So

1069
00:41:35.480 --> 00:41:37.920
a lot of people used to call it Hermione, um,

1070
00:41:37.920 --> 00:41:39.800
so the traditional name. But anyway, the

1071
00:41:39.880 --> 00:41:41.680
material from Mercury, about 2% of it, would

1072
00:41:41.680 --> 00:41:42.680
have rained down on the Earth.

1073
00:41:42.680 --> 00:41:45.080
Now this ties into the

1074
00:41:45.890 --> 00:41:47.410
work that I've talked about before about

1075
00:41:47.410 --> 00:41:50.290
panspermia as well. Material ejected from one

1076
00:41:50.290 --> 00:41:52.810
planet becomes objects moving

1077
00:41:52.810 --> 00:41:55.330
freely within the solar system, subject to

1078
00:41:55.970 --> 00:41:58.610
the gravitational pinball that goes on.

1079
00:41:59.410 --> 00:42:01.570
If you have a collision in orbit around

1080
00:42:01.570 --> 00:42:04.490
Saturn, if it is a collision between two of

1081
00:42:04.490 --> 00:42:07.210
Saturn's moons, the overwhelmingly vast

1082
00:42:07.210 --> 00:42:09.250
majority of ejecta will stay bound in the

1083
00:42:09.250 --> 00:42:11.410
Saturn system because the moons are both

1084
00:42:11.410 --> 00:42:13.370
themselves very deep in Saturn's gravity

1085
00:42:13.370 --> 00:42:16.320
while very tightly held. So

1086
00:42:16.320 --> 00:42:18.360
the vast majority of ejector from two moons

1087
00:42:18.360 --> 00:42:20.680
colliding with each other will be kept in

1088
00:42:20.680 --> 00:42:23.640
house. But that's not all of it.

1089
00:42:24.120 --> 00:42:26.920
Also some of that ejector, uh, that ejector

1090
00:42:26.920 --> 00:42:28.520
in the Saturn system will be like ejector in

1091
00:42:28.520 --> 00:42:30.200
the solar system. It'll be bounced around and

1092
00:42:30.200 --> 00:42:32.640
moved around by the gravity of the moons. So

1093
00:42:32.640 --> 00:42:34.320
a small tiny fraction of it could eventually

1094
00:42:34.320 --> 00:42:36.880
be ejected that way as well. If you have a

1095
00:42:36.880 --> 00:42:39.560
collision that instead involves or

1096
00:42:39.560 --> 00:42:41.530
invokes an object that is not currently

1097
00:42:41.530 --> 00:42:43.250
orbiting Saturn, but is a comet or an

1098
00:42:43.250 --> 00:42:45.890
asteroid passing through, that object itself

1099
00:42:45.890 --> 00:42:47.810
is moving faster than the escape velocity of

1100
00:42:47.810 --> 00:42:49.250
Saturn. So a significant amount of the

1101
00:42:49.250 --> 00:42:52.210
ejector also will be that case. You'll get

1102
00:42:52.210 --> 00:42:54.450
more material put into orbit around the sun.

1103
00:42:55.010 --> 00:42:57.250
Once the material has escaped from Saturn,

1104
00:42:57.810 --> 00:43:00.210
it is moving on an orbit that makes it one of

1105
00:43:00.210 --> 00:43:02.010
the Centaurs. And the Centaurs are one of my

1106
00:43:02.010 --> 00:43:04.330
favourite populations of objects anyway

1107
00:43:04.330 --> 00:43:06.090
because they're what I studied for my PhD and

1108
00:43:06.090 --> 00:43:08.290
I did the same dynamic simulations of them.

1109
00:43:08.290 --> 00:43:09.530
Where do they come from? Where are they

1110
00:43:09.530 --> 00:43:11.790
going? How will they get there? The

1111
00:43:11.790 --> 00:43:14.150
Centaurs are uh, the parent population of the

1112
00:43:14.150 --> 00:43:16.950
short period comets. The Centaurs themselves

1113
00:43:17.030 --> 00:43:19.830
are uh, daughters, sons,

1114
00:43:19.910 --> 00:43:22.550
children of the transept union. Objects

1115
00:43:22.790 --> 00:43:24.350
moving around in the after solar system being

1116
00:43:24.350 --> 00:43:27.310
scattered inwards. In my simulations

1117
00:43:27.310 --> 00:43:29.830
of the Centaurs, about one third of

1118
00:43:29.830 --> 00:43:31.910
Centaurs, which is about one third of those

1119
00:43:31.910 --> 00:43:33.590
objects between the orbits of Jupiter and

1120
00:43:33.590 --> 00:43:35.680
Neptune that are on unstable orbits, about

1121
00:43:35.680 --> 00:43:37.200
one third of them will eventually become a

1122
00:43:37.200 --> 00:43:38.880
Jupiter family comet will be flung into the

1123
00:43:38.880 --> 00:43:41.250
inner solar system, usually by Jupiter, uh,

1124
00:43:41.250 --> 00:43:42.600
which means it'll be put onto an Earth

1125
00:43:42.600 --> 00:43:45.280
crossing orbit, which means that if you eject

1126
00:43:45.280 --> 00:43:48.080
enough material from the Saturn

1127
00:43:48.080 --> 00:43:50.760
system, some of it will hit the

1128
00:43:50.760 --> 00:43:53.280
Earth. It'll be vanishingly small amount.

1129
00:43:54.000 --> 00:43:56.760
It is unlikely though that you'll get a

1130
00:43:56.760 --> 00:43:59.200
chunk big enough to cause a mass extinction,

1131
00:43:59.360 --> 00:44:02.250
making it all that far. The

1132
00:44:02.250 --> 00:44:04.610
thing that killed the dinosaurs was about 10

1133
00:44:04.610 --> 00:44:06.170
kilometres across, we think, maybe even a

1134
00:44:06.170 --> 00:44:08.490
little bit bigger. That's a very, very, very

1135
00:44:08.490 --> 00:44:11.130
big bit of stuff. Now, obviously there's a

1136
00:44:11.130 --> 00:44:12.450
small chance it could have been the result of

1137
00:44:12.450 --> 00:44:14.890
something like that. There are suggestions

1138
00:44:15.050 --> 00:44:17.009
that the thing that killed off the dinosaurs

1139
00:44:17.009 --> 00:44:19.770
might have been an asteroid that was probably

1140
00:44:19.770 --> 00:44:21.530
producing a collision in the asteroid belt.

1141
00:44:21.530 --> 00:44:23.090
And being a member of one of the collisional

1142
00:44:23.090 --> 00:44:24.490
families that feed material to the inner

1143
00:44:24.490 --> 00:44:26.690
solar system, others have suggested it could

1144
00:44:26.690 --> 00:44:29.420
be a comet, it could potentially

1145
00:44:29.660 --> 00:44:32.660
have been a fragment of a smashed

1146
00:44:32.660 --> 00:44:34.500
moon, like Paul is suggesting. It could have

1147
00:44:34.500 --> 00:44:36.620
been a very ancient fragment of another

1148
00:44:36.620 --> 00:44:38.340
Mercury collision that had managed to survive

1149
00:44:38.340 --> 00:44:40.020
4 billion years. But that's vanishingly

1150
00:44:40.020 --> 00:44:42.450
unlikely. Cause things are ejected on a m

1151
00:44:42.450 --> 00:44:43.780
much shorter time scale. So there'll be

1152
00:44:43.780 --> 00:44:46.460
nothing left, effectively. But we don't know

1153
00:44:46.780 --> 00:44:49.540
that's a fundamental thing. What drives

1154
00:44:49.540 --> 00:44:52.340
the understanding that the impact itself was

1155
00:44:52.340 --> 00:44:55.020
extraterrestrial was initially the

1156
00:44:55.020 --> 00:44:56.900
iridium layer that was found globally. That

1157
00:44:56.900 --> 00:44:59.140
was kind of a bit of a smoking gun. At the

1158
00:44:59.140 --> 00:45:00.580
point of the mass extinction in the fossil

1159
00:45:00.580 --> 00:45:03.140
record, they found the crater. You

1160
00:45:03.140 --> 00:45:06.090
cannot tell from the crater's size alone, um,

1161
00:45:06.090 --> 00:45:08.220
what the nature of the impactor was or the

1162
00:45:08.220 --> 00:45:11.220
impact speed. Now, for a crater

1163
00:45:11.220 --> 00:45:13.820
that old, it's a bit impossible to do.

1164
00:45:13.820 --> 00:45:16.020
Anyway, I've been really interested and we've

1165
00:45:16.020 --> 00:45:18.020
never got around to doing this as research to

1166
00:45:18.420 --> 00:45:20.460
talk with people like the creator, counting

1167
00:45:20.460 --> 00:45:22.690
people to see if there is anywhere for bodies

1168
00:45:22.690 --> 00:45:24.170
like the Moon or Mars where there's much less

1169
00:45:24.170 --> 00:45:27.170
weathering to distinguish between a cometary

1170
00:45:27.170 --> 00:45:29.770
or asteroidal impact on the basis of

1171
00:45:31.130 --> 00:45:33.770
whether the speed's influence on the

1172
00:45:33.770 --> 00:45:36.690
kinetic energy of the impact can modify

1173
00:45:36.690 --> 00:45:39.250
the crater formation process. Probably it

1174
00:45:39.250 --> 00:45:41.290
can't, because effectively you're dumping X

1175
00:45:41.370 --> 00:45:43.290
energy into the surface and that's what makes

1176
00:45:43.290 --> 00:45:46.210
the crater. But I've been interested in that.

1177
00:45:46.210 --> 00:45:47.690
But what that means from the Earth's point of

1178
00:45:47.690 --> 00:45:49.990
view is, uh, from the morphology of the

1179
00:45:49.990 --> 00:45:52.550
crater, from what's left from that impact, we

1180
00:45:52.550 --> 00:45:54.390
cannot tell what the impact was or how fast

1181
00:45:54.390 --> 00:45:56.790
it's travelling. Had to be faster than the

1182
00:45:56.790 --> 00:45:58.310
escape velocity of the Earth because it came

1183
00:45:58.310 --> 00:46:00.350
from beyond the Earth. So the minimum speed

1184
00:46:00.350 --> 00:46:03.030
is 12 kilometres a second. It is almost

1185
00:46:03.590 --> 00:46:05.590
guaranteed that it was a solar system object,

1186
00:46:05.590 --> 00:46:07.750
not an interstellar comet like Comet Atlas.

1187
00:46:07.990 --> 00:46:09.750
Which means that the maximum speed it could

1188
00:46:09.750 --> 00:46:11.750
have hit us is 72 kilometres a second.

1189
00:46:12.550 --> 00:46:15.490
Which is, you get that number by

1190
00:46:15.490 --> 00:46:17.050
combining the orbital speed of the Earth,

1191
00:46:17.050 --> 00:46:19.010
which is 30 kilometres a second going forward

1192
00:46:19.490 --> 00:46:21.410
with the maximum speed that something could

1193
00:46:21.410 --> 00:46:23.370
be travelling at one astronomical unit at our

1194
00:46:23.370 --> 00:46:25.730
location and still be bound to the sun,

1195
00:46:25.730 --> 00:46:28.170
which, if you work out the velocity, if

1196
00:46:28.170 --> 00:46:31.170
you're going at 42 kilometres a second at the

1197
00:46:31.170 --> 00:46:32.730
location of the Earth's orbit, you're right

1198
00:46:32.730 --> 00:46:34.970
on the boundary between the solar system's

1199
00:46:34.970 --> 00:46:37.490
escape velocity and not so anything faster

1200
00:46:37.490 --> 00:46:39.890
than that will escape. Take those two numbers

1201
00:46:39.890 --> 00:46:41.280
and say, right, you've got an optic, the

1202
00:46:41.280 --> 00:46:43.360
object coming head on at, uh, the fastest

1203
00:46:43.360 --> 00:46:45.800
speed it could have and stay bound to the

1204
00:46:45.800 --> 00:46:48.720
solar system. 42 kilometres a second one

1205
00:46:48.720 --> 00:46:50.400
way, 30 kilometres a second the other way

1206
00:46:50.400 --> 00:46:53.320
gives you 72 kilometres a second. So we know

1207
00:46:53.320 --> 00:46:55.800
the velocity with which this thing was coming

1208
00:46:55.800 --> 00:46:58.560
in within a factor of six. Most likely it's

1209
00:46:58.560 --> 00:46:59.680
at the lower end because we get more

1210
00:46:59.680 --> 00:47:02.640
asteroidal impactors and cometary ones, but

1211
00:47:02.640 --> 00:47:04.600
we don't really have much more than that on

1212
00:47:04.600 --> 00:47:07.040
the composition of it. There is a lot of

1213
00:47:07.040 --> 00:47:09.780
debate over whether it was cometary, whether

1214
00:47:09.780 --> 00:47:12.020
it was asteroidal. An object

1215
00:47:12.660 --> 00:47:15.580
formed from part of one of the moons of

1216
00:47:15.580 --> 00:47:18.500
Saturn would be ice rich and, uh,

1217
00:47:18.540 --> 00:47:20.940
so it would look like a cometary impactor. So

1218
00:47:20.940 --> 00:47:23.779
I'm not sure for an impact 65 million years

1219
00:47:23.779 --> 00:47:26.380
old, whether we would ever be able to

1220
00:47:26.380 --> 00:47:28.980
distinguish between a fragment of one of the

1221
00:47:28.980 --> 00:47:31.940
moons of Saturn as the impactor and a

1222
00:47:31.940 --> 00:47:34.130
comet as the impactor. Um,

1223
00:47:35.670 --> 00:47:37.630
I just have no idea how we would do that.

1224
00:47:37.630 --> 00:47:39.670
What we would probably be able to do is if we

1225
00:47:39.670 --> 00:47:42.470
went to a near Earth object, whether

1226
00:47:42.470 --> 00:47:44.630
it's a comet or an asteroid, and took

1227
00:47:44.630 --> 00:47:47.510
samples, there is a potential that

1228
00:47:47.510 --> 00:47:50.270
then maybe through isotopic analysis we could

1229
00:47:50.270 --> 00:47:52.990
tell that something was a fragment of a

1230
00:47:52.990 --> 00:47:55.710
Saturnian moon. But we need things to compare

1231
00:47:55.710 --> 00:47:58.310
that to. That is very much on the very

1232
00:47:58.310 --> 00:48:00.150
fringes of what we can do. But we do that a

1233
00:48:00.150 --> 00:48:02.940
little bit with some meteorites. There's a

1234
00:48:02.940 --> 00:48:04.420
couple of families of meteorites where we

1235
00:48:04.420 --> 00:48:06.940
think we know the parent object. And these

1236
00:48:06.940 --> 00:48:09.940
meteorites are compositionally grouped

1237
00:48:09.940 --> 00:48:11.980
together with such tightness that they are

1238
00:48:11.980 --> 00:48:14.700
distinguishable against the compositions of

1239
00:48:14.700 --> 00:48:16.300
everything as a background. It's like if you

1240
00:48:16.380 --> 00:48:17.940
measure the composition of everything and

1241
00:48:17.940 --> 00:48:19.860
then points on a wall. These ones all group

1242
00:48:19.860 --> 00:48:21.660
together so they come from the same parent.

1243
00:48:22.060 --> 00:48:23.820
But I don't know how we could

1244
00:48:25.580 --> 00:48:28.260
figure out whether it was a fragment of a

1245
00:48:28.260 --> 00:48:30.870
Saturnian moon versus a comet.

1246
00:48:31.350 --> 00:48:32.670
If we got to the point where we could

1247
00:48:32.670 --> 00:48:35.470
distinguish comet versus asteroid, I think

1248
00:48:35.470 --> 00:48:37.390
the argument will be it's a cometary body,

1249
00:48:37.390 --> 00:48:40.030
probably, um, but we couldn't tell you

1250
00:48:40.030 --> 00:48:41.550
whether it's short or a long period comet.

1251
00:48:41.550 --> 00:48:43.390
But people will probably come down on the

1252
00:48:43.390 --> 00:48:46.190
cometary exclamation rather than the fragment

1253
00:48:46.190 --> 00:48:48.470
of a moon explanation because of the Occam's

1254
00:48:48.470 --> 00:48:49.990
razor thing. So if you've got two

1255
00:48:50.470 --> 00:48:52.270
explanations that are equally good at

1256
00:48:52.270 --> 00:48:54.030
explaining the storey, take the one that's

1257
00:48:54.030 --> 00:48:55.670
simpler. Yeah, that might not be Occam's

1258
00:48:55.670 --> 00:48:57.190
razor, but that's one of those philosophical

1259
00:48:57.190 --> 00:48:59.780
constructs that, you know, it's a

1260
00:48:59.940 --> 00:49:02.780
more complex and challenging

1261
00:49:02.780 --> 00:49:04.420
route to get a fragment of a saturnian

1262
00:49:04.420 --> 00:49:06.900
satellite to kill the dinosaurs than it is to

1263
00:49:06.900 --> 00:49:08.340
have it just be a normal comet.

1264
00:49:08.340 --> 00:49:10.980
Andrew Dunkley: Yeah, fair enough. All right, very good.

1265
00:49:11.070 --> 00:49:13.700
Um, thank you, Paul. I think we

1266
00:49:13.780 --> 00:49:16.660
covered that topic uh, very, very well and

1267
00:49:16.660 --> 00:49:18.740
hope all's well in Queensland.

1268
00:49:18.900 --> 00:49:21.660
Hey, uh, we're going to take a breath

1269
00:49:21.660 --> 00:49:24.620
and then we'll quickly go into our final

1270
00:49:24.620 --> 00:49:26.740
question here on Space Nuts.

1271
00:49:31.490 --> 00:49:32.450
Jonti Horner: Space Nuts.

1272
00:49:32.610 --> 00:49:35.530
Andrew Dunkley: And we're with Professor Johnty Horner today

1273
00:49:35.530 --> 00:49:38.210
with Fred Watson Away, uh, a Q A edition.

1274
00:49:38.850 --> 00:49:41.130
One last question. Uh, we'll have to make it

1275
00:49:41.130 --> 00:49:42.610
quick because I think we really burnt the

1276
00:49:42.610 --> 00:49:44.690
clock today. Too much talking about accents.

1277
00:49:44.690 --> 00:49:46.370
I think, uh, I have a question.

1278
00:49:47.250 --> 00:49:49.210
Jonti Horner: I was just gonna say talking of accents, get

1279
00:49:49.210 --> 00:49:52.050
Fred Watson to sing a Climb or Bata because

1280
00:49:52.050 --> 00:49:54.130
he's from my neck of the woods originally.

1281
00:49:54.130 --> 00:49:56.750
Andrew Dunkley: Okay. Uh, I have a question

1282
00:49:56.830 --> 00:49:59.390
that might come across as lame or childish.

1283
00:49:59.390 --> 00:50:02.190
Yes it did. No, no it didn't. Uh, but I'm

1284
00:50:02.190 --> 00:50:04.950
hoping that a professor and a genuine

1285
00:50:04.950 --> 00:50:07.830
space nut, uh, or I'm

1286
00:50:07.830 --> 00:50:10.670
hoping that asking a professor and a genuine

1287
00:50:10.670 --> 00:50:12.990
space nut this question, it might prompt

1288
00:50:13.390 --> 00:50:15.990
for much more interesting answer than the

1289
00:50:15.990 --> 00:50:16.830
average Joe.

1290
00:50:16.910 --> 00:50:19.110
What is your favourite planet in our solar

1291
00:50:19.110 --> 00:50:21.430
system and why? I wish I could give you an

1292
00:50:21.430 --> 00:50:23.570
interesting answer myself. I do find Jupiter

1293
00:50:23.570 --> 00:50:26.530
fascinating. And Europa. Okay, yeah, I know

1294
00:50:26.530 --> 00:50:29.170
it's a moon, but I'm intrigued by what could

1295
00:50:29.170 --> 00:50:31.650
be under all that ice. Hopefully um, we'll

1296
00:50:31.650 --> 00:50:33.770
find out in my lifetime. So yeah, childish

1297
00:50:33.770 --> 00:50:35.770
question from a 40 year old, but hopefully

1298
00:50:36.090 --> 00:50:38.449
you can turn it into a more deep and

1299
00:50:38.449 --> 00:50:40.490
meaningful answer. That's Dan from the Gold

1300
00:50:40.490 --> 00:50:42.250
coast, also a Queenslander.

1301
00:50:42.950 --> 00:50:45.730
Um, I can go first and be very quick. I'm

1302
00:50:45.730 --> 00:50:48.130
fascinated by Mars. I just find the

1303
00:50:48.130 --> 00:50:50.910
geography um,

1304
00:50:51.110 --> 00:50:53.830
outstanding. A smaller planet than Earth

1305
00:50:54.710 --> 00:50:57.250
with geographic um,

1306
00:50:57.270 --> 00:51:00.150
highlights that are just mind bogglingly

1307
00:51:00.230 --> 00:51:02.950
huge. Like the, the Olympus

1308
00:51:02.950 --> 00:51:05.229
Mons for example. That, that is a volcano

1309
00:51:05.229 --> 00:51:07.070
that is, it's the biggest in the solar

1310
00:51:07.070 --> 00:51:10.070
system. And um, I think

1311
00:51:10.070 --> 00:51:12.430
it is so high that it's actually sticking out

1312
00:51:12.430 --> 00:51:14.520
of Earth's, out of Mars's atmosphere.

1313
00:51:15.230 --> 00:51:17.990
Um, the canyons on Mars and

1314
00:51:17.990 --> 00:51:20.990
there's more than one, but the biggest

1315
00:51:20.990 --> 00:51:23.630
one dwarfs the Grand Canyon. On Earth.

1316
00:51:23.790 --> 00:51:25.790
Like I think you can fit the Grand Canyon in

1317
00:51:25.950 --> 00:51:28.830
one of its tributaries. Um, and the

1318
00:51:28.830 --> 00:51:30.749
list goes on. It is a

1319
00:51:31.550 --> 00:51:33.590
fascinating planet. I always like to think of

1320
00:51:33.590 --> 00:51:35.990
it as, um, that was God's first attempt and

1321
00:51:35.990 --> 00:51:38.190
he stuffed it up and then we came next.

1322
00:51:40.680 --> 00:51:43.570
Uh, and, and because we've been able

1323
00:51:43.570 --> 00:51:46.330
to send so many probes and rovers

1324
00:51:46.330 --> 00:51:49.250
and satellites to Mars, we've

1325
00:51:49.250 --> 00:51:51.450
been able to document it, get some

1326
00:51:51.690 --> 00:51:54.690
incredible high res pictures of

1327
00:51:54.690 --> 00:51:57.690
it. I just find it a beautiful, beautiful

1328
00:51:57.690 --> 00:52:00.250
world. And I mentioned my sci fi

1329
00:52:00.250 --> 00:52:02.860
trilogy earlier. Um,

1330
00:52:03.050 --> 00:52:05.850
Mars is in it. I couldn't leave it out.

1331
00:52:06.730 --> 00:52:09.050
So Mars for me that was a quick answer.

1332
00:52:09.450 --> 00:52:11.210
What's yours? It's got to be in the solar

1333
00:52:11.210 --> 00:52:11.450
system.

1334
00:52:12.260 --> 00:52:14.540
Jonti Horner: It's a really tough one. And these kind of

1335
00:52:14.540 --> 00:52:17.500
questions throw, throw me because it

1336
00:52:17.500 --> 00:52:19.180
might be a childish question because it's

1337
00:52:19.180 --> 00:52:21.660
kind of questions kids ask, but it's entirely

1338
00:52:21.660 --> 00:52:24.580
a good question. I'm um, not as broken

1339
00:52:24.580 --> 00:52:27.090
by this. While I was over in Switzerland, um,

1340
00:52:27.090 --> 00:52:29.700
met up with an ex of mine whose daughter's

1341
00:52:29.700 --> 00:52:32.580
now 9 or 10 years old and her daughter's

1342
00:52:32.580 --> 00:52:35.380
doing English in school and all well and good

1343
00:52:35.940 --> 00:52:38.650
and she wanted to practise her English and

1344
00:52:38.650 --> 00:52:40.570
was talking to us a bit in English. And kids

1345
00:52:40.570 --> 00:52:41.930
ask you what's your favourite colour? Things

1346
00:52:41.930 --> 00:52:43.330
like that. She asked me what my favourite

1347
00:52:43.330 --> 00:52:45.770
fruit was. And um, I was just broken because

1348
00:52:45.770 --> 00:52:48.250
I've never really thought of that. And um, it

1349
00:52:48.250 --> 00:52:49.890
took me like two or three minutes to kind of.

1350
00:52:49.890 --> 00:52:52.730
It just put me into this head jam and um, I

1351
00:52:52.730 --> 00:52:55.050
didn't know an answer. This one's a little

1352
00:52:55.050 --> 00:52:57.970
bit like this. And to me this question's a

1353
00:52:57.970 --> 00:53:00.130
bit like asking somebody with a large family

1354
00:53:00.130 --> 00:53:02.010
who their favourite child is or asking

1355
00:53:02.010 --> 00:53:03.250
someone who their favourite pet is. Now I

1356
00:53:03.250 --> 00:53:05.590
suspect I don't have kids but I think

1357
00:53:06.070 --> 00:53:07.950
the favourite kid varies from time to time

1358
00:53:07.950 --> 00:53:09.270
with people who've got parents and they'd

1359
00:53:09.270 --> 00:53:11.430
never say they have a favourite but there's a

1360
00:53:11.430 --> 00:53:13.790
little ranking scale. It's Nanny Ogg and her

1361
00:53:13.790 --> 00:53:15.430
extended family in the Discworld series where

1362
00:53:15.430 --> 00:53:16.870
you could tell how in favour people were

1363
00:53:16.870 --> 00:53:18.750
where, where the trinkets that they bought

1364
00:53:18.750 --> 00:53:20.510
her were in the house. And you know, heaven

1365
00:53:20.510 --> 00:53:21.830
forfend that the little thing you brought

1366
00:53:21.830 --> 00:53:23.310
back from holiday ended up on the coffee

1367
00:53:23.310 --> 00:53:25.190
table outside in the hallway because that

1368
00:53:25.190 --> 00:53:27.670
meant you were really in the bad books. I

1369
00:53:28.390 --> 00:53:30.310
really struggle to answer questions like this

1370
00:53:30.310 --> 00:53:32.900
because they're all fascinating in

1371
00:53:33.220 --> 00:53:35.060
different ways. You know, there are things

1372
00:53:35.300 --> 00:53:37.540
that we can really get from the Mars, from an

1373
00:53:37.540 --> 00:53:39.380
astrobiology point of view is really the

1374
00:53:39.380 --> 00:53:41.020
obvious answer. Because it's a place that

1375
00:53:41.020 --> 00:53:43.940
will look for life elsewhere. Jupiter's the

1376
00:53:43.940 --> 00:53:45.820
obvious answer because it's been fundamental

1377
00:53:45.820 --> 00:53:47.460
to a lot of the research I've done in terms

1378
00:53:47.460 --> 00:53:50.100
of the question of Jupiter, friend or foe. It

1379
00:53:50.100 --> 00:53:51.860
throws a lot of comments our way. It's a

1380
00:53:51.860 --> 00:53:54.780
source of, therefore, indirectly the

1381
00:53:54.780 --> 00:53:56.380
cause of many of the meteor showers and many

1382
00:53:56.380 --> 00:53:58.830
of the meteor stones and stuff we see. I

1383
00:53:59.150 --> 00:54:01.830
they would be contenders, as would the

1384
00:54:01.830 --> 00:54:04.150
others. To a certain degree. Neptune, because

1385
00:54:04.150 --> 00:54:06.190
it's a fabulous insight into how

1386
00:54:06.750 --> 00:54:09.270
science can change of time and how we can

1387
00:54:09.270 --> 00:54:11.790
discover things without seeing them. Neptune

1388
00:54:11.790 --> 00:54:14.350
kind of presaged the exoplanet era

1389
00:54:15.070 --> 00:54:17.030
because we discovered Neptune not by seeing

1390
00:54:17.030 --> 00:54:19.550
Neptune but by observing Uranus, misbehaving

1391
00:54:19.630 --> 00:54:22.150
and inferring that Neptune had to be there to

1392
00:54:22.150 --> 00:54:24.180
cause that, uh, misbehaviour. Although there

1393
00:54:24.180 --> 00:54:26.380
are some suggestions that Galileo actually

1394
00:54:26.380 --> 00:54:29.060
saw Neptune in 1610 and should be

1395
00:54:29.060 --> 00:54:31.100
credited as the discoverer but didn't realise

1396
00:54:31.100 --> 00:54:33.940
what he had. There's a background star marked

1397
00:54:33.940 --> 00:54:36.660
on one of his drawings, I think of the

1398
00:54:36.660 --> 00:54:39.220
Galilean moons, the moons of Jupiter, where

1399
00:54:39.220 --> 00:54:40.980
there is no, uh, star and people think it was

1400
00:54:40.980 --> 00:54:42.820
actually Neptune. So there are some

1401
00:54:42.820 --> 00:54:44.540
suggestions. Galileo was a discoverer of

1402
00:54:44.540 --> 00:54:44.860
Neptune.

1403
00:54:44.860 --> 00:54:45.420
Andrew Dunkley: Interesting.

1404
00:54:45.740 --> 00:54:47.780
Jonti Horner: But for me, Neptune's fascinating because of

1405
00:54:47.780 --> 00:54:49.900
that indirect discovery. But I think for me,

1406
00:54:50.140 --> 00:54:52.100
if you really push it, I probably have to say

1407
00:54:52.100 --> 00:54:54.820
the Earth. Oh, and a. It's the, uh, Earth

1408
00:54:54.900 --> 00:54:57.620
because we is here. But the Earth is a place

1409
00:54:57.620 --> 00:54:59.620
that's driven all that complexity in terms of

1410
00:54:59.620 --> 00:55:01.500
life. And if you think about Mars being a

1411
00:55:01.500 --> 00:55:04.420
complex place, the Earth is even more so

1412
00:55:04.420 --> 00:55:06.020
because of the influence of the water and the

1413
00:55:06.020 --> 00:55:07.460
atmosphere, the weathering and the plate

1414
00:55:07.460 --> 00:55:10.300
tectonics, you know, so it's my favourite

1415
00:55:10.300 --> 00:55:11.700
from the point of view of it's the only place

1416
00:55:11.700 --> 00:55:13.700
I can sit around comfortably in shorts and T

1417
00:55:13.700 --> 00:55:16.660
shirt and chat like this. Also because

1418
00:55:16.660 --> 00:55:18.820
it is the window into

1419
00:55:19.620 --> 00:55:21.700
the future of our knowledge of life elsewhere

1420
00:55:22.180 --> 00:55:24.140
and it's a cradle of everything we know and

1421
00:55:24.140 --> 00:55:27.020
everything we've experienced. I do have a

1422
00:55:27.020 --> 00:55:28.620
deep and abiding love of the Earth, uh, from

1423
00:55:28.620 --> 00:55:30.500
that point of view, but also as a scientist,

1424
00:55:30.500 --> 00:55:33.340
the Earth is fascinatingly complex

1425
00:55:33.340 --> 00:55:36.100
compared to the other planets. It's the only

1426
00:55:36.100 --> 00:55:39.020
planet on which we observe plate

1427
00:55:39.020 --> 00:55:41.940
tectonics. Yeah. Therefore it's the only

1428
00:55:41.940 --> 00:55:44.580
planet whose surface on long time scales is

1429
00:55:44.660 --> 00:55:47.170
that degree of changeable, immutable. You

1430
00:55:47.170 --> 00:55:50.130
know, if I brought you back, say we did,

1431
00:55:50.490 --> 00:55:52.530
um, play with Rennie's question from the

1432
00:55:52.530 --> 00:55:54.810
start a bit more. We built the spacecraft

1433
00:55:54.810 --> 00:55:57.650
from Tau Zero, we accelerated, had a problem,

1434
00:55:58.290 --> 00:56:00.690
couldn't slow down, eventually managed to fix

1435
00:56:00.690 --> 00:56:02.250
it, came back and we came back. In a billion

1436
00:56:02.250 --> 00:56:04.770
years time, Mars would still look like it

1437
00:56:04.770 --> 00:56:07.450
does today unless humanity terraforms

1438
00:56:07.450 --> 00:56:09.650
Mars. Mars would look like it does today.

1439
00:56:09.650 --> 00:56:11.410
Venus would look like it does today. All of

1440
00:56:11.410 --> 00:56:12.930
the planets would look like they do today.

1441
00:56:13.580 --> 00:56:15.380
Saturn's rings may have gone, peripheral

1442
00:56:15.380 --> 00:56:16.500
things like that will have gone, but the

1443
00:56:16.500 --> 00:56:18.780
Earth will be unrecognisable. With

1444
00:56:18.780 --> 00:56:20.900
continental drift, the Earth wouldn't look

1445
00:56:20.900 --> 00:56:23.140
like home. And even with a change in the

1446
00:56:23.140 --> 00:56:24.420
atmosphere, the Earth may have changed.

1447
00:56:24.420 --> 00:56:26.780
I've seen some suggestions that when the

1448
00:56:26.780 --> 00:56:29.099
Earth was young, the oceans weren't blue,

1449
00:56:29.099 --> 00:56:30.780
they were green. Yeah, I've heard, uh, that's

1450
00:56:30.780 --> 00:56:33.140
how much the Earth has changed. The mountain

1451
00:56:33.140 --> 00:56:34.740
ranges will have shifted. I always find it

1452
00:56:34.740 --> 00:56:37.500
fascinating to wonder what is the biggest

1453
00:56:37.500 --> 00:56:39.540
mountain that the Earth has ever had? And you

1454
00:56:39.540 --> 00:56:41.020
Google that, that's been asked a lot.

1455
00:56:41.620 --> 00:56:44.260
Nobody's really got a strong answer

1456
00:56:44.500 --> 00:56:46.700
because a lot of it depends on the elasticity

1457
00:56:46.700 --> 00:56:48.140
of the Earth's interior and the energy

1458
00:56:48.140 --> 00:56:50.460
available for plate tectonics. Because the

1459
00:56:50.460 --> 00:56:52.100
limiting factor on the height of the mountain

1460
00:56:52.100 --> 00:56:55.060
on Earth is the sinking that you get as a

1461
00:56:55.060 --> 00:56:57.059
result of the m mass of the mountain and the

1462
00:56:57.059 --> 00:56:59.020
weathering that we get that wears it away on

1463
00:56:59.020 --> 00:57:01.140
Mars, you don't have that. With Olympus Mons,

1464
00:57:01.140 --> 00:57:03.740
there's no weathering. So it could just get

1465
00:57:03.740 --> 00:57:05.380
bigger and bigger. Even though it will have a

1466
00:57:05.380 --> 00:57:07.860
very deep root, it could keep getting bigger

1467
00:57:07.860 --> 00:57:09.100
because there was nothing wearing it down

1468
00:57:09.100 --> 00:57:11.880
again. So I think for me, because of the

1469
00:57:11.880 --> 00:57:14.320
complexity and, um, because it gives me a

1470
00:57:14.320 --> 00:57:16.440
place to do my astrophotography and live my

1471
00:57:16.440 --> 00:57:19.000
life and all the rest of it, the Earth would

1472
00:57:19.000 --> 00:57:20.680
have to be the top of the list. But trying to

1473
00:57:20.680 --> 00:57:23.320
pick a planet other than the Earth is a bit

1474
00:57:23.320 --> 00:57:25.679
like trying to pick your favourite pet or

1475
00:57:25.679 --> 00:57:27.120
your favourite child. And it might be that

1476
00:57:27.120 --> 00:57:28.920
you have one internally, but Heaven and you

1477
00:57:28.920 --> 00:57:29.360
tell them.

1478
00:57:31.440 --> 00:57:33.400
Andrew Dunkley: Very good answer, Very good answer. I love

1479
00:57:33.400 --> 00:57:35.680
the question. So, uh, not childish at all

1480
00:57:35.760 --> 00:57:37.880
and, uh, appreciate you sending it in. And if

1481
00:57:37.880 --> 00:57:40.210
you'd like to send questions into us at Space

1482
00:57:40.210 --> 00:57:42.530
Nuts, jump on our website, spacenuts

1483
00:57:42.930 --> 00:57:44.370
IO or

1484
00:57:44.370 --> 00:57:47.250
spacenutspodcast.com and click on

1485
00:57:47.250 --> 00:57:49.370
the Ask me anything button at the top. It's

1486
00:57:49.370 --> 00:57:51.450
just labelled AMA M. And while you're there,

1487
00:57:51.450 --> 00:57:53.170
have a look around, cheque out the shop, sign

1488
00:57:53.170 --> 00:57:55.890
up for the newsletter, um, see if you want to

1489
00:57:55.890 --> 00:57:58.050
become a supporter, that's optional and

1490
00:57:58.130 --> 00:58:00.330
please leave reviews wherever you listen to

1491
00:58:00.330 --> 00:58:02.730
us and that'll wrap us up for another

1492
00:58:02.730 --> 00:58:04.450
episode. Jonty, thank you so much.

1493
00:58:05.020 --> 00:58:06.500
Jonti Horner: That's a pleasure. Thank you for having me.

1494
00:58:06.500 --> 00:58:07.340
Andrew Dunkley: Always a pleasure.

1495
00:58:07.420 --> 00:58:09.940
Professor John T Horner, professor of

1496
00:58:09.940 --> 00:58:12.140
Astrophysics at the University of Southern

1497
00:58:12.140 --> 00:58:15.060
Queensland. Hey. And, uh, Huw in

1498
00:58:15.060 --> 00:58:17.260
the studio, um, couldn't be with us today. He

1499
00:58:17.260 --> 00:58:19.620
realised that Earth wasn't his favourite

1500
00:58:19.620 --> 00:58:22.020
planet, so he left. And from me, Andrew

1501
00:58:22.020 --> 00:58:23.700
Dunkley. Thanks for your company. Catch you

1502
00:58:23.700 --> 00:58:26.620
on the next episode of Space Nuts. Bye. Bye.

1503
00:58:27.900 --> 00:58:30.100
Jonti Horner: You've been listening to the Space Nuts

1504
00:58:30.100 --> 00:58:32.790
podcast, available

1505
00:58:32.870 --> 00:58:35.110
at Apple Podcasts, Spotify,

1506
00:58:35.190 --> 00:58:37.990
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1507
00:58:37.990 --> 00:58:40.390
player. You can also stream on demand at

1508
00:58:40.390 --> 00:58:41.430
bytes. Com.

1509
00:58:41.750 --> 00:58:43.830
Andrew Dunkley: This has been another quality podcast

1510
00:58:43.830 --> 00:58:45.510
production from Bytes.

1511
00:58:45.590 --> 00:58:47.530
Jonti Horner: Com. Um.