Navigating Time, Saturn’s Mysteries & Planetary Favourites | A Q&A Episode | Space Nuts:...

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Language: en

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Hi there. Thanks again for joining us.


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This is a Q&A edition of Space Nuts,


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where we talk astronomy and space


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science. And in a Q&A edition, uh UQ and


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we a uh which means we'll answer


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audience questions. Uh today we're going


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to talk about uh moving through time.


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What does that mean? Uh also some stuff


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from Saturn's rings and a sort of


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hypothetical, not a hypothetical, but a


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you know, not even a what if question.


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And it's just a question asking our


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favorite planets and why. Well, you


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know, um that's Jonty's thing. So, we


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will talk about all of that on this


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episode of Space Nuts.


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>> 15 seconds. Guidance is internal. 10 9


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Ignition sequence start.


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>> Space Nuts.


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>> 5 4 3 2 1 2 3 4 5 5 4 3 2 1


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>> Space Nuts.


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>> Astronauts report. It feels good. And


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while Fred's away, Jonty is here to play


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and answer your questions. He is


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Professor Jotty her, professor of


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astrophysics at the University of


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Southern Queensland. Hello, Johnny.


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>> Hey, how are you going?


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>> I am very well. Good to see you again.


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>> Well, it's good. Yeah. Now, I've got


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interesting questions today.


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>> Yeah, we've got some beauties. Um, we


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might get straight into it. Our first


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question comes from Renie uh in Sunny


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West Hills, California. Hi, Renie. Renie


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is a a regular contributor, so u we hear


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from Renie semi-regularly.


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Uh can you please explain what it means


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to be moving through time? If I


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theoretically could sit in a chair from


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birth to death, will I die on a faster


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timeline than someone who lived a


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regular normal life? uh is what's aging


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me about the movement of the earth


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around the sun combined with the sun


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moving around the galaxy combined with


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the galaxies moving around each other


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and my own 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 uh


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thanks Renie um let's open that one up


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to a little bit of um investigation


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>> absolutely and I think the first thing


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I'd say here is this is such a fun


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question it may be well give it a couple


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of months and ask it again and see


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whether Fred gives a similar answer to


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me or not.


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>> Um, it it's a really interesting one.


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So, the idea of time being a dimension


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is something that I think makes all of


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our heads hurt a little bit when we


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first encounter it and for most of us


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continues to do so forever more. It's


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one of the fundamentals of the idea of


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what I guess is often described as


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space-time physics comes out of the work


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that people like Albert Einstein did


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with relativity.


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We're used to the three physical three


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spatial dimensions


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up, down, left, right, and forward and


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back. Although I I'm realizing more and


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more that we actually live in a two two


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plus one kind of existence really


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because we don't look up very often.


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Part of our common sense is about


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two-dimensional movement, not


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threedimensional cuz we think about


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moving around on the surface of the


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earth and there's all sorts of weird and


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fundamental things with that. Now, the


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idea that time is also a dimension is


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part of that whole thing of space-time


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physics built into the relativity twins,


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you know, special in general. And it's a


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very weird one because with the other


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dimensions,


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we choose where to move or we're carried


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along where we're aware of motion.


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Motion in a way that is changing


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direction. We can change speed. We feel


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agency. But with time, when you get told


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that time is a dimension, you think,


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"But I can't move. I can't choose my


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motion in it. We're all carried through


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time at 1 second per second. And so it's


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like a dimension without agency. It's


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all a little bit weird.


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>> Now, it does lead to that concept of


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time as a dimension is one of the things


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that's part of the underpinninging of


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all this stuff like with special and


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general relativity, things like time


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dilation, stuff like this. It's also


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tied into


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um events and consequences, the logical


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order of things. You know, a cause has


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to cause an effect. You don't get the


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effect before the cause. Things like


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this. Now,


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this rapidly gets very complicated. And


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I know at university when you study


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physics as a partner to astronomy or you


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study um relative relativity as part of


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an astronomy thing, I know a lot of


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people find it hugely challenging to get


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their head around it. And I will openly


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admit that when I did my relativity


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courses as an undergrad, my head hurt.


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It 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


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something I'd say to listeners is that


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no one explanation will work for


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everybody. We all learn in different


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ways, and one source that is brilliant


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for me might not be brilliant for you.


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So if my explanation doesn't work,


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please go out and seek another one.


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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 match in that case and


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another explanation is needed. And when


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it came to relativity, I was very much


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in that boat. I was sat in these


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lectures and this is old style education


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30 years ago and it actually is 29 and a


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half years ago that I was in these


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lectures cuz it was late 1996. Sat there


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taking notes on paper while somebody's


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talking at you and writing on a board.


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So a lot of the information was going


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through from my eyes to the page without


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going through my brain. I suspect, you


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know, that autonomous writing thing,


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>> but it just wasn't jelling for me. The


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whole the equations are written down so


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you can use them, but it wasn't making


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sense. And the course textbook we had


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was incredibly mathematical because


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the person who wrote the textbook


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understood it through the maths, so they


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explained it through the maths. And


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that's not the way that I learn. Some


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people learn brilliantly from maths. I


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don't. I'm much more of a visual form or


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a picture form or metaphor type thinker


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than an equation is a be all and end


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all. So about the only textbook I ever


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used in my undergrad days, I was


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terrible. I'd buy the textbooks, not


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open them, and then I'd sell them on at


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the end of the trimester, end of the


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term for someone else to take off me and


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probably do the same thing.


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>> But I found a textbook in the library


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that worked for me and ended up buying


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it. And I was going to recommend it


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because it was so foundation in helping


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me to overcome something I couldn't


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understand that I always think when


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people are struggling with the


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relativity stuff. Worth recommending it.


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It's a big book called Spacetime Physics


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by Edwin F. Taylor and John Archie Bald


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Wheeler. And to my shock, I looked it up


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just before this podcast and the first


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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


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theory of special relativity than my


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reading it


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>> or certainly than we are today should I


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say absolutely than we are today. Um it


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is still in print and what worked for me


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was that it didn't go straight to the


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maths instead it used drawings and


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figures and thought experiments and I


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read it voraciously. It was very


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readable. I remember it from 30 years


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ago and it had an impact. I'd really


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recommend that if you're struggling with


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the relativity stuff, um, go to your


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local library. The textbooks are


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punishingly expensive and um, therefore


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I'd always recommend people get them


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from library first and make absolutely


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sure. But if you're at all interested in


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those foundations of how relativity and


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everything works, I found that book


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astonishing. Okay,


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>> that's all getting a bit off the topic


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though. But that explains a lot better


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than I could do the concepts behind


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relativity that include time as a


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dimension. Includes space-time diagrams,


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which are these weird cone- shaped


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figures where if you're traveling at the


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speed of light, you move the same


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distance in X, which is distance as you


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do in time Y. So you get a cone opened


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out like this and everything inside that


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cone is moving slower than the speed of


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light because it's going up the y- axis


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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


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observer than they could observe it yet.


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So any light that left that would not


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have reached you yet. Now hard to


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visualize but if you look into the book


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that is what it means. Now moving in


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time is talking about our motion on the


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y-axis of that graph where we move up it


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by 1 second every second.


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>> Y


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>> that is something over which we do not


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really have control. Um I I suspect some


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people would argue that certain


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substances that can be ingested change


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your perception of how time loads. So


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you might be able to control the speed


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you fly through it there. But that's


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what we mean by moving in time. It's


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perceiving time moving forward so that


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from one second to the next change


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happens. You know, yesterday is a time


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in the past that's already happened.


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That's a cause. You'll see the effects


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today. Tomorrow hasn't happened yet. You


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can't see what is there tomorrow.


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


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And it there's all sorts of wonderful


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ways people have described it or played


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with this. again. You know, I often come


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back to the Terry Pratt stuff and I was


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just looking at a thread the other day


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of people talking about their favorite


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Terry Pratt quotes. I'll just try and


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pull this one up. Um, it's from when the


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eternally surprised, uh, who was the


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founder of the history monks. Um,


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basically talking about his perception


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of time. So, you know, man looks a


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keyboard cuz I didn't think of doing


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this, but yeah, this is from Thief of


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Time, I think it was. Yes. um talking


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about how when viewed the universe and


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viewed moving through time as this


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ancient philosopher who set up the monks


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of history who are the people who run


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around unseen in the background fixing


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things when they go wrong because in the


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disc world they go wrong all the time.


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Yeah.


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>> But says when considered the nature of


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time


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>> and understood that the universe is


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instant by instant recreated a new.


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Therefore he understood there is in


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truth no past only a memory of the past.


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Blink your eyes and the world you see


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next did not exist when you closed them.


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Therefore, he said, the only appropriate


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state of the mind is surprise. The only


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appropriate state of the heart is joy.


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The sky you see now, you have never seen


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before. The perfect moment is now. Be


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glad of it.


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>> That's good.


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>> I talk about patchet a lot, but I always


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think that's really beautiful and it


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fits in with this concept of time moving


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irrevocably forward. You can never


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return to the past and change things.


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What you can change is the future. When


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you wake up every morning, it's as


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though you're newborn into the universe


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effectively because who is to say that


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you ever lived before? You know, it may


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well be that all of your memories were


00:10:50.640 --> 00:10:52.310
just implanted in you when you woke up


00:10:52.320 --> 00:10:53.829
this very instant. We don't know.


00:10:53.839 --> 00:10:55.190
Obviously,


00:10:55.200 --> 00:10:57.590
>> the Okam's razor argument is yes, you


00:10:57.600 --> 00:10:59.110
existed yesterday and we did do the


00:10:59.120 --> 00:11:01.590
record the other day. But it's


00:11:01.600 --> 00:11:02.790
interesting to think of that and it's


00:11:02.800 --> 00:11:06.470
the way that people perceive time. Now


00:11:06.480 --> 00:11:08.069
moving on to the motion side of it,


00:11:08.079 --> 00:11:10.550
Renie. Um the idea of sitting in a chair


00:11:10.560 --> 00:11:12.949
from birth to death and how that would


00:11:12.959 --> 00:11:15.430
affect your life. I'm not a medic, but I


00:11:15.440 --> 00:11:16.949
suspect if you ask your doctor that


00:11:16.959 --> 00:11:18.470
question, they will probably tell you


00:11:18.480 --> 00:11:21.030
that indeed if you sat in a chair from


00:11:21.040 --> 00:11:22.310
birth to death, your life would be


00:11:22.320 --> 00:11:23.670
shorter than if you lived a normal life


00:11:23.680 --> 00:11:26.150
as a person because of health reasons. I


00:11:26.160 --> 00:11:27.350
mean if nothing else if there's no one


00:11:27.360 --> 00:11:29.030
around to feed you it might lead to a


00:11:29.040 --> 00:11:32.150
relatively short existence. So there is


00:11:32.160 --> 00:11:35.509
that aspect of it as well. We can't see


00:11:35.519 --> 00:11:37.350
the future. So we can't predict what our


00:11:37.360 --> 00:11:38.630
choices are going to do in terms of


00:11:38.640 --> 00:11:40.630
lengthening or shortening our lives. But


00:11:40.640 --> 00:11:42.870
there is one way in which your motion


00:11:42.880 --> 00:11:45.269
can lead to you having a slightly


00:11:45.279 --> 00:11:48.310
different timeline. So from the point of


00:11:48.320 --> 00:11:49.750
view of your life or the number of beats


00:11:49.760 --> 00:11:51.590
of your heart or your perceived time,


00:11:51.600 --> 00:11:53.829
you live the time that you live.


00:11:53.839 --> 00:11:56.150
>> Yeah. The faster you're moving though,


00:11:56.160 --> 00:11:58.230
and this is an outcome of general


00:11:58.240 --> 00:12:02.790
relativity, motion causes time dilation,


00:12:02.800 --> 00:12:04.550
particularly motion with acceleration.


00:12:04.560 --> 00:12:06.230
You know, there's loads and loads of


00:12:06.240 --> 00:12:08.470
complexity to this.


00:12:08.480 --> 00:12:11.509
If you were moving faster,


00:12:11.519 --> 00:12:14.150
the time you perceive is very slightly


00:12:14.160 --> 00:12:16.230
slower. Now, you then get into rest


00:12:16.240 --> 00:12:18.150
frames and all that stuff makes my head


00:12:18.160 --> 00:12:20.470
hurt. So the only place this actually


00:12:20.480 --> 00:12:23.670
really becomes relevant particularly in


00:12:23.680 --> 00:12:25.110
our day-to-day lives in our lived


00:12:25.120 --> 00:12:27.430
experience is when you've got a moving


00:12:27.440 --> 00:12:28.790
platform that's changing direction. So


00:12:28.800 --> 00:12:31.190
it's undergoing acceleration.


00:12:31.200 --> 00:12:33.430
Think about satellites circling the


00:12:33.440 --> 00:12:36.230
earth. They are circling the earth. They


00:12:36.240 --> 00:12:38.949
are moving at a faster speed than we are


00:12:38.959 --> 00:12:41.350
here on the surface of the earth.


00:12:41.360 --> 00:12:43.110
>> We however slightly nearer the center of


00:12:43.120 --> 00:12:44.310
the earth. So we get a little bit of


00:12:44.320 --> 00:12:46.150
gravitational time dilation as I


00:12:46.160 --> 00:12:48.949
understand it. Our clock runs slightly


00:12:48.959 --> 00:12:50.389
slower because we're at the bottom of a


00:12:50.399 --> 00:12:51.910
gravity well, but that is hugely


00:12:51.920 --> 00:12:53.829
overcome by the fact of the high speed


00:12:53.839 --> 00:12:55.509
things are moving in orbit. You're


00:12:55.519 --> 00:12:58.470
talking several kilometers per second.


00:12:58.480 --> 00:13:01.030
Now, under general and special


00:13:01.040 --> 00:13:04.150
relativity, you can work out the number


00:13:04.160 --> 00:13:06.150
of seconds you experience per second


00:13:06.160 --> 00:13:08.470
that ticks in a certain rest frame using


00:13:08.480 --> 00:13:10.710
these equations to get the time


00:13:10.720 --> 00:13:13.190
dilation. And typically that is a


00:13:13.200 --> 00:13:14.949
vanishingly vanishingly small effect


00:13:14.959 --> 00:13:16.870
unless you get very near the speed of


00:13:16.880 --> 00:13:19.430
light and then it ramps up. But it is a


00:13:19.440 --> 00:13:22.870
large enough effect that both we need to


00:13:22.880 --> 00:13:26.470
understand it and we can measure it. Now


00:13:26.480 --> 00:13:28.310
to illustrate the level of this, it's


00:13:28.320 --> 00:13:30.069
not a huge effect. There's a fabulous


00:13:30.079 --> 00:13:33.269
stat that there are people who spent


00:13:33.279 --> 00:13:35.269
time on the International Space Station


00:13:35.279 --> 00:13:36.710
who therefore technically have


00:13:36.720 --> 00:13:38.710
experienced less time passing while they


00:13:38.720 --> 00:13:40.150
were up there than we did on the ground


00:13:40.160 --> 00:13:42.550
watching them. because of time dilation,


00:13:42.560 --> 00:13:43.750
because of their fast movement and their


00:13:43.760 --> 00:13:45.750
acceleration and all the rest of it.


00:13:45.760 --> 00:13:47.190
Space stations going around the earth


00:13:47.200 --> 00:13:49.829
what nearly 8 km/s


00:13:49.839 --> 00:13:51.750
roughly. A couple of Russian guys were


00:13:51.760 --> 00:13:54.629
up there for 6 months. Sergey Criclev


00:13:54.639 --> 00:13:58.069
and Sergey Avd, they did 6 months up


00:13:58.079 --> 00:14:01.829
there and as a result of time dilation,


00:14:01.839 --> 00:14:03.430
when they returned to the surface of the


00:14:03.440 --> 00:14:05.829
earth, they would have experienced less


00:14:05.839 --> 00:14:07.750
time passing than the people on the


00:14:07.760 --> 00:14:09.030
ground did while they were up there.


00:14:09.040 --> 00:14:10.550
>> Yeah. but not enough for them to


00:14:10.560 --> 00:14:12.470
perceive. It would have been 20


00:14:12.480 --> 00:14:13.430
milliseconds,


00:14:13.440 --> 00:14:13.990
>> right?


00:14:14.000 --> 00:14:18.150
>> So that's 0.02 seconds. Um 21,000th of a


00:14:18.160 --> 00:14:20.710
second. It's not very much, but it has a


00:14:20.720 --> 00:14:23.670
huge impact on our day-to-day life. And


00:14:23.680 --> 00:14:26.389
this means that that part of the


00:14:26.399 --> 00:14:29.030
theories of relativity are among the


00:14:29.040 --> 00:14:31.590
most tested theories ever to have been


00:14:31.600 --> 00:14:33.189
developed by humans. And the reason I


00:14:33.199 --> 00:14:35.750
say that is that every time you use your


00:14:35.760 --> 00:14:38.550
generic fruitbased device to navigate,


00:14:38.560 --> 00:14:41.110
anytime you use a satnav, you're using


00:14:41.120 --> 00:14:43.430
GPS satellites.


00:14:43.440 --> 00:14:46.550
GPS satellites orbiting the Earth allow


00:14:46.560 --> 00:14:48.470
you to work out your position on a basic


00:14:48.480 --> 00:14:51.750
level because at any time your device


00:14:51.760 --> 00:14:54.550
can see signals from a number of those


00:14:54.560 --> 00:14:56.389
satellites


00:14:56.399 --> 00:14:59.430
and figure out where they are. There are


00:14:59.440 --> 00:15:00.949
clocks on board all of them. you know,


00:15:00.959 --> 00:15:02.470
it can figure out the like travel time


00:15:02.480 --> 00:15:04.550
to get to it. By seeing the time that


00:15:04.560 --> 00:15:06.470
they're broadcasting, knowing what your


00:15:06.480 --> 00:15:08.310
local time is, figuring out the


00:15:08.320 --> 00:15:09.350
difference between the two, you know,


00:15:09.360 --> 00:15:11.590
how far away the satellite is from one


00:15:11.600 --> 00:15:13.269
of them, that places you at any point on


00:15:13.279 --> 00:15:14.790
a sphere around that satellite that is


00:15:14.800 --> 00:15:16.710
that distance away. From a second


00:15:16.720 --> 00:15:18.069
satellite, you've got another sphere,


00:15:18.079 --> 00:15:19.350
and you're where they intersect, which


00:15:19.360 --> 00:15:22.470
gives you a line. And then a third one


00:15:22.480 --> 00:15:23.750
brings it down to a point. And the more


00:15:23.760 --> 00:15:26.230
you have, the more accurate you get. So


00:15:26.240 --> 00:15:27.990
this is all based on measurement of


00:15:28.000 --> 00:15:31.430
time, allowing you to measure distance


00:15:31.440 --> 00:15:33.269
for things that are at a known distance


00:15:33.279 --> 00:15:36.790
away. This only works so if you can take


00:15:36.800 --> 00:15:38.629
into account the way that the clocks are


00:15:38.639 --> 00:15:40.870
ticking at different speeds because the


00:15:40.880 --> 00:15:42.310
satellites are moving in orbit around


00:15:42.320 --> 00:15:43.829
the Earth.


00:15:43.839 --> 00:15:47.189
The difference including relativistic


00:15:47.199 --> 00:15:49.430
effects and time dilation into the


00:15:49.440 --> 00:15:52.230
calculations for GPS has my


00:15:52.240 --> 00:15:53.910
understanding is it's between a factor


00:15:53.920 --> 00:15:56.310
of 10 and a factor of 100 on the


00:15:56.320 --> 00:15:58.389
precision with which your location be


00:15:58.399 --> 00:16:00.629
can can be calculated and your GPS is


00:16:00.639 --> 00:16:02.550
usually good to probably about a meter.


00:16:02.560 --> 00:16:04.230
I think some of the modern ones are even


00:16:04.240 --> 00:16:06.069
more accurate than that. So if you


00:16:06.079 --> 00:16:07.990
imagine that let's take the really


00:16:08.000 --> 00:16:09.590
optimistic case that you're only getting


00:16:09.600 --> 00:16:11.269
a factor of 10 improvement by including


00:16:11.279 --> 00:16:13.670
relativity at the minute you've got an


00:16:13.680 --> 00:16:15.110
accuracy of 1 meter and that's good


00:16:15.120 --> 00:16:16.949
enough for you to navigate with 10 m it


00:16:16.959 --> 00:16:19.189
probably wouldn't be with 100 m it


00:16:19.199 --> 00:16:21.990
certainly wouldn't be. So our GPS


00:16:22.000 --> 00:16:26.389
systems only work because of our level


00:16:26.399 --> 00:16:28.949
of understanding of relativistic motion


00:16:28.959 --> 00:16:31.350
and of time dilation. So those


00:16:31.360 --> 00:16:33.590
satellites moving very very quickly


00:16:33.600 --> 00:16:35.829
around the earth


00:16:35.839 --> 00:16:37.749
are experiencing an infinite decimally


00:16:37.759 --> 00:16:39.189
small amount of time dilation compared


00:16:39.199 --> 00:16:40.710
to the things they're broadcasting to on


00:16:40.720 --> 00:16:41.749
the surface


00:16:41.759 --> 00:16:43.350
>> and we have to factor that in into our


00:16:43.360 --> 00:16:45.829
calculations to navigate. So your satnav


00:16:45.839 --> 00:16:48.470
wouldn't work without the theorems that


00:16:48.480 --> 00:16:50.470
Albert Einstein put together more than a


00:16:50.480 --> 00:16:51.990
century ago


00:16:52.000 --> 00:16:53.749
>> that are all about how things move


00:16:53.759 --> 00:16:54.870
through time.


00:16:54.880 --> 00:16:56.870
>> So hopefully that has answered that


00:16:56.880 --> 00:16:59.269
question. I think Renie, I would be very


00:16:59.279 --> 00:17:00.949
tempted to suggest that at some point


00:17:00.959 --> 00:17:02.629
you try and get friend to answer that as


00:17:02.639 --> 00:17:05.270
well, just to see where he took it. Um,


00:17:05.280 --> 00:17:06.789
but hopefully that at least is helpful.


00:17:06.799 --> 00:17:08.710
And like I say, if the relativistic


00:17:08.720 --> 00:17:10.710
stuff really interests you, spacetime


00:17:10.720 --> 00:17:12.150
physics, even though it's a book that


00:17:12.160 --> 00:17:14.390
was first published 60 years ago, I


00:17:14.400 --> 00:17:16.789
found invaluable in getting me through


00:17:16.799 --> 00:17:18.470
the exams and actually allowed me to get


00:17:18.480 --> 00:17:19.990
out of my first year and pass rather


00:17:20.000 --> 00:17:21.429
than being kicked out of uni. So, it was


00:17:21.439 --> 00:17:24.309
a great book. H uh Renie might also like


00:17:24.319 --> 00:17:26.870
to go on Wikipedia or any number of


00:17:26.880 --> 00:17:29.270
platforms and look up the twin paradox.


00:17:29.280 --> 00:17:30.950
That's a fun one. That's a great thought


00:17:30.960 --> 00:17:33.669
experiment. And I think there were twin


00:17:33.679 --> 00:17:36.789
astronauts that have uh had a little bit


00:17:36.799 --> 00:17:38.549
of a separation in age because one of


00:17:38.559 --> 00:17:41.190
them spent spent much more time in space


00:17:41.200 --> 00:17:44.390
than his brother. So um their age


00:17:44.400 --> 00:17:47.270
difference uh increased by 8.6


00:17:47.280 --> 00:17:49.510
milliseconds or something something like


00:17:49.520 --> 00:17:50.470
that.


00:17:50.480 --> 00:17:52.549
>> I've seen Yeah,


00:17:52.559 --> 00:17:54.390
>> there are a couple of well there are


00:17:54.400 --> 00:17:56.789
many science fiction books that play


00:17:56.799 --> 00:17:58.310
around this. I've spoken before about


00:17:58.320 --> 00:17:59.669
this series of science fiction books


00:17:59.679 --> 00:18:01.830
called the mass works of science fiction


00:18:01.840 --> 00:18:03.510
which was an attempt by a publisher to


00:18:03.520 --> 00:18:05.830
make money obviously but also to bring


00:18:05.840 --> 00:18:07.590
back some classic science fiction that


00:18:07.600 --> 00:18:10.710
is regarded as being very good and you


00:18:10.720 --> 00:18:12.230
know some of the things I read are very


00:18:12.240 --> 00:18:13.669
fun but they're not necessarily very


00:18:13.679 --> 00:18:15.350
good. You know, there's always that side


00:18:15.360 --> 00:18:16.950
of things. And I'd say the Chrysis books


00:18:16.960 --> 00:18:18.950
I'm reading at the minute, the guy


00:18:18.960 --> 00:18:20.710
incarnated into the body of an ant,


00:18:20.720 --> 00:18:22.230
that's very good fun. I'm really loving


00:18:22.240 --> 00:18:23.669
it, but I wouldn't necessarily say


00:18:23.679 --> 00:18:25.750
they're high literature. They're fun.


00:18:25.760 --> 00:18:27.669
Um, the practic stuff is a bit of both,


00:18:27.679 --> 00:18:30.150
but these mass works of science fiction


00:18:30.160 --> 00:18:34.310
are often fascinating because they are


00:18:34.320 --> 00:18:36.070
quite often hard sci-fi. So in other


00:18:36.080 --> 00:18:37.350
words, there science fiction that is


00:18:37.360 --> 00:18:39.029
grounded in our understanding of science


00:18:39.039 --> 00:18:41.110
at the time they were written and tries


00:18:41.120 --> 00:18:44.789
to use the laws of physics to help build


00:18:44.799 --> 00:18:46.310
the narrative rather than waving the


00:18:46.320 --> 00:18:48.150
laws of physics to allow the narrative.


00:18:48.160 --> 00:18:49.430
You know, there's a fundamental


00:18:49.440 --> 00:18:50.789
difference between the soft and woolly


00:18:50.799 --> 00:18:53.669
sci-fi and the hard scientific sci-fi.


00:18:53.679 --> 00:18:55.990
And two books in particular that leap to


00:18:56.000 --> 00:18:57.190
mind when we're talking about time


00:18:57.200 --> 00:18:58.870
dilation and relativity and things like


00:18:58.880 --> 00:19:02.470
that are The Forever War by Joe Heburn,


00:19:02.480 --> 00:19:04.310
I think his name was. I'll just put that


00:19:04.320 --> 00:19:07.430
name up. The Forever War um was


00:19:07.440 --> 00:19:10.710
basically yeah Joe Holderman. Um the


00:19:10.720 --> 00:19:13.669
idea that there is um it's written in


00:19:13.679 --> 00:19:15.590
1974. It's called military science


00:19:15.600 --> 00:19:17.750
fiction. And the idea is humans are


00:19:17.760 --> 00:19:19.350
fighting an interstellar war against


00:19:19.360 --> 00:19:21.909
these alien civilization. And they're


00:19:21.919 --> 00:19:23.750
sent off on missions on spacecraft that


00:19:23.760 --> 00:19:25.350
travel at relativistic speed because it


00:19:25.360 --> 00:19:26.549
takes a hell of a long time to get


00:19:26.559 --> 00:19:28.549
anywhere. And it's not really about what


00:19:28.559 --> 00:19:29.990
they do when they get there. It's about


00:19:30.000 --> 00:19:31.190
what they do when they come back.


00:19:31.200 --> 00:19:32.390
Because the time you've gone there and


00:19:32.400 --> 00:19:34.549
come back, the earth has moved on


00:19:34.559 --> 00:19:36.310
hugely. You know, you've been away for


00:19:36.320 --> 00:19:38.470
five years, but earth has skipped


00:19:38.480 --> 00:19:39.990
forward 100 years.


00:19:40.000 --> 00:19:41.990
>> Can you reintegrate? How has society


00:19:42.000 --> 00:19:44.870
changed? And I think it's fair to say


00:19:44.880 --> 00:19:46.789
that without a spoiler,


00:19:46.799 --> 00:19:48.630
>> the motivation is that you've more in


00:19:48.640 --> 00:19:50.070
common with the people you've lived that


00:19:50.080 --> 00:19:51.270
experience with than you do with


00:19:51.280 --> 00:19:52.549
everybody else.


00:19:52.559 --> 00:19:55.990
>> And it's all about that. grounded in


00:19:56.000 --> 00:19:59.590
this knowledge of time dilation. I have


00:19:59.600 --> 00:20:00.789
traveled there and back again and come


00:20:00.799 --> 00:20:02.870
back to a world that is changed. The


00:20:02.880 --> 00:20:04.789
other one that really stuck in my mind


00:20:04.799 --> 00:20:07.350
as a interesting way to get your head


00:20:07.360 --> 00:20:08.950
around time dilation is a book called


00:20:08.960 --> 00:20:11.590
Talzer by Paul Anderson and I think that


00:20:11.600 --> 00:20:12.950
was published even longer ago. I think


00:20:12.960 --> 00:20:15.350
it was probably in the 1950s and part of


00:20:15.360 --> 00:20:17.350
the reason I can say that is that that


00:20:17.360 --> 00:20:20.390
book I believe predates the Big Bang


00:20:20.400 --> 00:20:23.029
Theory um or it's around the time of the


00:20:23.039 --> 00:20:25.510
Big Bang Theory. It's um based on a


00:20:25.520 --> 00:20:27.350
short story published in 1967. The book


00:20:27.360 --> 00:20:30.149
itself was published in 1970. So it's a


00:20:30.159 --> 00:20:33.510
a fabulous exploration of it was


00:20:33.520 --> 00:20:35.909
actually post Big Bang, but it's a


00:20:35.919 --> 00:20:38.070
fabulous exploration of relativity in an


00:20:38.080 --> 00:20:39.830
unusual circumstance. In this case, it


00:20:39.840 --> 00:20:42.630
was people being the first humans to


00:20:42.640 --> 00:20:45.029
travel to the stars on a spaceship that


00:20:45.039 --> 00:20:48.390
was meant to go to a star and then come


00:20:48.400 --> 00:20:50.630
back and report. Um they were aiming to


00:20:50.640 --> 00:20:53.830
reach beta vaginis. It says crew of 50,


00:20:53.840 --> 00:20:56.470
25 men, 25 women using something called


00:20:56.480 --> 00:20:59.029
a busard ramjet. So you have basically a


00:20:59.039 --> 00:21:01.190
rocket that scoops up fuel and burns it


00:21:01.200 --> 00:21:04.470
to go faster and faster, right? Um, but


00:21:04.480 --> 00:21:05.669
there's a problem. They get up to high


00:21:05.679 --> 00:21:07.029
speed and then something breaks, but


00:21:07.039 --> 00:21:08.310
they're going so quick that they can't


00:21:08.320 --> 00:21:11.510
get outside the spacecraft to fix it.


00:21:11.520 --> 00:21:13.270
And so they just have to go quicker and


00:21:13.280 --> 00:21:16.630
quicker. And so it explores this captive


00:21:16.640 --> 00:21:19.350
group of 50 people on an island in the


00:21:19.360 --> 00:21:21.110
universe that cannot stop, can only go


00:21:21.120 --> 00:21:23.350
quicker and quicker as the universe


00:21:23.360 --> 00:21:25.350
moves around them. And of course, by


00:21:25.360 --> 00:21:26.789
continually accelerating, they get


00:21:26.799 --> 00:21:28.950
closer and closer to the speed of light.


00:21:28.960 --> 00:21:30.789
And time dilation impacts them more and


00:21:30.799 --> 00:21:33.669
more. So they see the universe to the


00:21:33.679 --> 00:21:36.470
end of the universe and beyond


00:21:36.480 --> 00:21:39.190
>> within a human lifetime. And you know,


00:21:39.200 --> 00:21:40.870
the cosmology in it has changed. It was


00:21:40.880 --> 00:21:42.549
at a time where the big bang a lot of


00:21:42.559 --> 00:21:43.830
people thought would end up in a big


00:21:43.840 --> 00:21:44.950
crunch that everything would stop


00:21:44.960 --> 00:21:47.510
expanding fall back together. But it's


00:21:47.520 --> 00:21:52.710
again this awesome way of demonstrating


00:21:52.720 --> 00:21:55.270
how relativistic terms work. And the


00:21:55.280 --> 00:21:57.350
crew on the mission before anything went


00:21:57.360 --> 00:21:58.870
wrong were aware that when they returned


00:21:58.880 --> 00:22:02.310
to Earth, something like 33 years would


00:22:02.320 --> 00:22:03.750
have passed before they get to their


00:22:03.760 --> 00:22:05.990
destination, this star. But for them,


00:22:06.000 --> 00:22:07.430
only 5 years would have passed. So when


00:22:07.440 --> 00:22:08.630
they turn around and come home, they'll


00:22:08.640 --> 00:22:10.630
have aged 10 years. But 66 years would


00:22:10.640 --> 00:22:11.909
have passed on Earth, give or take.


00:22:11.919 --> 00:22:12.630
>> Yeah, that that's


00:22:12.640 --> 00:22:14.630
>> In fact, that doesn't happen. Wonderful


00:22:14.640 --> 00:22:15.110
book.


00:22:15.120 --> 00:22:16.149
>> Yeah,


00:22:16.159 --> 00:22:18.870
>> it I love those sorts of stories. I I I


00:22:18.880 --> 00:22:22.630
love time, travel, sci-fi, and uh um all


00:22:22.640 --> 00:22:27.270
those relativistic uh concepts. I Yeah,


00:22:27.280 --> 00:22:29.029
I'm actually just finished writing a


00:22:29.039 --> 00:22:30.470
trilogy, and I'm just getting it proof


00:22:30.480 --> 00:22:32.230
read at the moment. Um Oh, fabulous.


00:22:32.240 --> 00:22:33.830
>> And there's a little bit of that in it,


00:22:33.840 --> 00:22:36.230
>> but I'm not giving anything away. So, so


00:22:36.240 --> 00:22:38.149
maybe without without any spoilers at


00:22:38.159 --> 00:22:40.470
all that in a few years time maybe I'll


00:22:40.480 --> 00:22:41.990
be picking up your books as part of the


00:22:42.000 --> 00:22:43.350
mass works of science fiction.


00:22:43.360 --> 00:22:45.029
>> You might.


00:22:45.039 --> 00:22:45.990
>> That'd be nice, wouldn't it?


00:22:46.000 --> 00:22:46.950
>> No pressure.


00:22:46.960 --> 00:22:49.590
>> No. Well, okay.


00:22:49.600 --> 00:22:51.909
Uh, thanks Randy. Um, enjoyed that


00:22:51.919 --> 00:22:53.590
question. It's a It's a fun one to talk


00:22:53.600 --> 00:22:55.190
about. This is Space Nuts with Andrew


00:22:55.200 --> 00:22:58.230
Dunley and Professor Jonty Horner.


00:22:58.240 --> 00:22:59.830
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00:24:46.880 --> 00:24:47.110
Think


00:24:47.120 --> 00:24:49.029
>> we need to do a little more all weather


00:24:49.039 --> 00:24:50.310
testing.


00:24:50.320 --> 00:24:52.549
>> Amen. Space nets.


00:24:52.559 --> 00:24:54.390
>> Our next question, Jonty, comes from


00:24:54.400 --> 00:24:57.110
Paul in Brisbane, although uh he doesn't


00:24:57.120 --> 00:24:58.789
call it Brisbane. You've probably heard


00:24:58.799 --> 00:25:01.190
this term because um you live so close


00:25:01.200 --> 00:25:03.590
to Brisbane, but overseas people might


00:25:03.600 --> 00:25:04.950
think, what on earth is he talking


00:25:04.960 --> 00:25:07.430
about? Good day, Space Nuts. Paul uh


00:25:07.440 --> 00:25:11.430
from sunny Bris Vegas uh here and he's


00:25:11.440 --> 00:25:13.590
thrown a challenge at me. Before I ask


00:25:13.600 --> 00:25:15.590
my question, could you read it in a


00:25:15.600 --> 00:25:18.310
Queensland accent to make it sound


00:25:18.320 --> 00:25:21.190
authentic? Andrew T,


00:25:21.200 --> 00:25:22.950
I'll give it a go, Paul. But, you know,


00:25:22.960 --> 00:25:24.549
it's been a long time since I lived in


00:25:24.559 --> 00:25:27.029
Queensland. I was thinking just


00:25:27.039 --> 00:25:31.110
listening in episode 681 when you and


00:25:31.120 --> 00:25:33.990
Fred started talking uh about the


00:25:34.000 --> 00:25:37.110
possibility of Titan and Hypernian


00:25:37.120 --> 00:25:39.909
Hyperion Collidon, uh, thus creating


00:25:39.919 --> 00:25:43.269
Saturn's rings 100 million years ago. Uh


00:25:43.279 --> 00:25:46.310
what do you reckon the odds are of some


00:25:46.320 --> 00:25:48.549
of the bigger blocks of the collision


00:25:48.559 --> 00:25:51.510
spinning off into space uh getting


00:25:51.520 --> 00:25:53.269
closer to the sun? I don't know.


00:25:53.279 --> 00:25:56.390
Colliding with the Earth, say 65 million


00:25:56.400 --> 00:25:59.830
years ago. Is that a possibility? Or


00:25:59.840 --> 00:26:02.870
does the chemical residue from on here


00:26:02.880 --> 00:26:05.990
on Earth suggest there's more likely to


00:26:06.000 --> 00:26:08.390
have been a comet? Curious to get your


00:26:08.400 --> 00:26:11.510
thoughts on this, eh? Uh, as always,


00:26:11.520 --> 00:26:15.190
keep up the great work and thank you.


00:26:15.200 --> 00:26:17.669
Was that Queenslandish enough?


00:26:17.679 --> 00:26:19.510
>> Uh, theatrical. So, the accent thing and


00:26:19.520 --> 00:26:21.029
again, we're very good at getting off


00:26:21.039 --> 00:26:21.990
topic or I am.


00:26:22.000 --> 00:26:23.669
>> Depends what part of Queensland because


00:26:23.679 --> 00:26:25.190
it's a big state.


00:26:25.200 --> 00:26:26.470
>> For people listening


00:26:26.480 --> 00:26:28.950
>> and you got to you got to chuck in an A


00:26:28.960 --> 00:26:30.230
on the end of every sentence.


00:26:30.240 --> 00:26:33.269
>> One of the things that's always made my


00:26:33.279 --> 00:26:34.630
head hurt a little bit since I moved to


00:26:34.640 --> 00:26:36.230
Australia in 2010 and I am officially


00:26:36.240 --> 00:26:37.269
Australian, you know.


00:26:37.279 --> 00:26:39.830
>> Yeah. is a lack of diversity in the


00:26:39.840 --> 00:26:43.350
accents. I I grew up in the UK where


00:26:43.360 --> 00:26:45.110
accents are very very varied to the


00:26:45.120 --> 00:26:46.310
extent that you could tell within my


00:26:46.320 --> 00:26:47.909
school which estate people grew up in


00:26:47.919 --> 00:26:49.510
because of subtleties in their accent


00:26:49.520 --> 00:26:52.710
locally. And the variation on the larger


00:26:52.720 --> 00:26:55.029
scale is astonishing. It's part of why I


00:26:55.039 --> 00:26:57.830
I think British actors have so much


00:26:57.840 --> 00:27:00.310
success, partly because they get very


00:27:00.320 --> 00:27:01.669
good training, of course, but if you're


00:27:01.679 --> 00:27:03.909
an actor in the UK, you have to have a


00:27:03.919 --> 00:27:05.510
fluidity with accents because there's


00:27:05.520 --> 00:27:07.590
such a diversity just within the UK.


00:27:07.600 --> 00:27:07.990
>> Yeah.


00:27:08.000 --> 00:27:11.110
>> And I came to Australia and I do not


00:27:11.120 --> 00:27:12.710
I've lost some of my ear for the UK


00:27:12.720 --> 00:27:14.470
accents. I used to be really good


00:27:14.480 --> 00:27:15.669
because you grow up there, it's a


00:27:15.679 --> 00:27:17.830
natural thing. I've lost a bit of that,


00:27:17.840 --> 00:27:20.789
>> but over here it seems to be there isn't


00:27:20.799 --> 00:27:22.549
a very strong regional diversity.


00:27:22.559 --> 00:27:24.950
There's just a little bit of town versus


00:27:24.960 --> 00:27:26.870
country and a very little bit of north


00:27:26.880 --> 00:27:30.870
south, but it's very smooth, although


00:27:30.880 --> 00:27:31.909
very little variety.


00:27:31.919 --> 00:27:34.470
>> I'll tell you, when I got into radio, I


00:27:34.480 --> 00:27:37.029
um did a demo tape and I had a friend


00:27:37.039 --> 00:27:39.430
listen to it who'd been in radio a very


00:27:39.440 --> 00:27:40.870
long time and I was only just starting


00:27:40.880 --> 00:27:42.149
out and he listened to it and he said,


00:27:42.159 --> 00:27:44.470
"You know, you've got to get rid of rid


00:27:44.480 --> 00:27:46.710
of your Newcastle twang." Cuz I grew up


00:27:46.720 --> 00:27:48.470
in the Hunter Valley um in that


00:27:48.480 --> 00:27:50.789
Newcastle district. And I said, "What?"


00:27:50.799 --> 00:27:52.710
He said, "You've got a Newcastle twang.


00:27:52.720 --> 00:27:55.830
There's a certain sound that comes out


00:27:55.840 --> 00:27:58.549
of the mouths of Navicestrians. You got"


00:27:58.559 --> 00:28:00.389
And I had to get I had to train that out


00:28:00.399 --> 00:28:01.750
of myself


00:28:01.760 --> 00:28:04.710
>> and and it it it can be no disrespect,


00:28:04.720 --> 00:28:06.950
but it can be a bit grating.


00:28:06.960 --> 00:28:10.789
>> Um but there there is there are


00:28:10.799 --> 00:28:13.669
diversities in in accent across


00:28:13.679 --> 00:28:15.350
Australia that when I worked for the


00:28:15.360 --> 00:28:17.909
ABC, they actually published a map of


00:28:17.919 --> 00:28:18.870
accents.


00:28:18.880 --> 00:28:19.110
>> Yeah. Yeah.


00:28:19.120 --> 00:28:21.269
>> And I think the most prominent variation


00:28:21.279 --> 00:28:23.110
is South Australia, particularly


00:28:23.120 --> 00:28:26.950
Adelaide. Much more posh,


00:28:26.960 --> 00:28:29.269
>> but it's also to me it's much more


00:28:29.279 --> 00:28:30.470
evidence because I just don't quite have


00:28:30.480 --> 00:28:32.789
the air for it cuz in the UK the accents


00:28:32.799 --> 00:28:34.710
are very much more val. So Newcastle


00:28:34.720 --> 00:28:36.149
accent to me is very different to what


00:28:36.159 --> 00:28:37.909
you think of a Newcastle accent.


00:28:37.919 --> 00:28:39.750
>> But where I see it is in language. So


00:28:39.760 --> 00:28:42.870
there's the the perennial argument among


00:28:42.880 --> 00:28:44.230
Australians of whether it's a potato


00:28:44.240 --> 00:28:46.389
cape or a potato scholar is a good


00:28:46.399 --> 00:28:47.830
example. you got regional things like


00:28:47.840 --> 00:28:49.029
that and for


00:28:49.039 --> 00:28:51.029
>> from my side of things I worked in


00:28:51.039 --> 00:28:52.710
Switzerland for 3 years


00:28:52.720 --> 00:28:55.669
>> and shared an office with Haga who was


00:28:55.679 --> 00:28:58.630
this young woman from I think Iran or


00:28:58.640 --> 00:29:00.389
somewhere Persian I'm not sure exactly


00:29:00.399 --> 00:29:02.870
where but we communicated in English


00:29:02.880 --> 00:29:04.630
which was her sixth language


00:29:04.640 --> 00:29:05.029
>> wow


00:29:05.039 --> 00:29:07.909
>> which was astonishing to me but there


00:29:07.919 --> 00:29:09.110
was one time I've been on the phone to


00:29:09.120 --> 00:29:10.630
my parents and I finished and she said


00:29:10.640 --> 00:29:14.389
so Johny what does a mean up and yeah a


00:29:14.399 --> 00:29:17.669
up um and It reminds me of the wonderful


00:29:17.679 --> 00:29:19.350
>> Isn't that Liverpoolian that


00:29:19.360 --> 00:29:22.470
>> no aopsy Yorkshire as well? Not far.


00:29:22.480 --> 00:29:24.950
>> If you want to see the accent of roughly


00:29:24.960 --> 00:29:26.950
where I grew up incidentally, it's worth


00:29:26.960 --> 00:29:29.669
people looking up the fabulous song Ilk


00:29:29.679 --> 00:29:31.909
Batat which is a cultural treasure from


00:29:31.919 --> 00:29:33.350
my part of the world and we all learned


00:29:33.360 --> 00:29:35.350
when we were in Scouts and at school and


00:29:35.360 --> 00:29:37.909
it's um basically group of group of


00:29:37.919 --> 00:29:39.190
fellas at the pub saying where where


00:29:39.200 --> 00:29:41.110
have you been since I saw you last? been


00:29:41.120 --> 00:29:42.950
you've been caught in Mary Jane and it


00:29:42.960 --> 00:29:45.269
goes on about how he's not been dressed


00:29:45.279 --> 00:29:46.470
appropriately and he's going to die in


00:29:46.480 --> 00:29:48.389
the laughter burium and but it's all in


00:29:48.399 --> 00:29:50.149
very strong dialect so you can see that


00:29:50.159 --> 00:29:53.029
but what that resulted in is everybody


00:29:53.039 --> 00:29:56.070
in burn communicated in English at the


00:29:56.080 --> 00:29:58.230
physical institute I had speak German


00:29:58.240 --> 00:30:01.269
when I was out in the town but English


00:30:01.279 --> 00:30:03.350
has become this kind of lingua frana


00:30:03.360 --> 00:30:06.470
lingua lingua frana there because


00:30:06.480 --> 00:30:07.590
Switzerland is a country with four


00:30:07.600 --> 00:30:08.950
different languages it's got French


00:30:08.960 --> 00:30:10.870
German Italian and romance


00:30:10.880 --> 00:30:12.870
But everybody's proud of their language.


00:30:12.880 --> 00:30:14.950
The French speakers will not silly


00:30:14.960 --> 00:30:16.950
themselves by speaking German to the


00:30:16.960 --> 00:30:18.789
German speakers. The German speakers


00:30:18.799 --> 00:30:20.389
therefore will not silly themselves by


00:30:20.399 --> 00:30:21.990
speaking the foul French to the French


00:30:22.000 --> 00:30:22.549
speakers.


00:30:22.559 --> 00:30:23.029
>> Yeah.


00:30:23.039 --> 00:30:25.350
>> So they speak English.


00:30:25.360 --> 00:30:28.310
Um but that means people have very good


00:30:28.320 --> 00:30:29.269
English, but they've learned a lot of


00:30:29.279 --> 00:30:31.110
their English from watching American TV


00:30:31.120 --> 00:30:33.029
rather than British TV. But even the


00:30:33.039 --> 00:30:35.750
British TV is a little bit denuded in


00:30:35.760 --> 00:30:40.070
terms of accent and um in terms


00:30:40.080 --> 00:30:43.590
particularly of dialect terms


00:30:43.600 --> 00:30:44.950
and it was to an extent we were talking


00:30:44.960 --> 00:30:46.630
about the accents the news presenters


00:30:46.640 --> 00:30:48.149
until about 20 or 30 years ago on the


00:30:48.159 --> 00:30:50.789
BBC had to use received pronunciation


00:30:50.799 --> 00:30:52.149
which is the Queen's English and you


00:30:52.159 --> 00:30:54.389
have to speak very properly and they got


00:30:54.399 --> 00:30:55.830
rid of that because people realize that


00:30:55.840 --> 00:30:57.510
actually diversity in accents represents


00:30:57.520 --> 00:30:58.710
the diversity of people and that's


00:30:58.720 --> 00:31:01.990
great. What that meant though was uh my


00:31:02.000 --> 00:31:03.750
accent I've reliably been told is


00:31:03.760 --> 00:31:06.389
relatively strong. But I don't really


00:31:06.399 --> 00:31:08.230
use any dialect terms anymore other than


00:31:08.240 --> 00:31:10.310
the o bit of Aussie stuff I've picked up


00:31:10.320 --> 00:31:11.750
because what was really throwing people


00:31:11.760 --> 00:31:14.710
in Switzerland was the dialect terms,


00:31:14.720 --> 00:31:17.190
not the accents, things like a up. And


00:31:17.200 --> 00:31:19.029
so my language has shifted. I've lost a


00:31:19.039 --> 00:31:20.789
bit of an A for the UK stuff, but I


00:31:20.799 --> 00:31:23.750
don't hear much variety in the


00:31:23.760 --> 00:31:25.430
Australian accent. Now, part of that is


00:31:25.440 --> 00:31:29.029
because I'm not from here, but I I


00:31:29.039 --> 00:31:30.630
always find that kind of stuff really


00:31:30.640 --> 00:31:32.070
really interesting. So, I mean, I could


00:31:32.080 --> 00:31:33.350
tell you were getting a stronger


00:31:33.360 --> 00:31:36.230
Australian accent. Um, but it wasn't


00:31:36.240 --> 00:31:37.830
necessarily I couldn't have told you


00:31:37.840 --> 00:31:40.549
where it was from. Other thing is,


00:31:40.559 --> 00:31:41.990
again, saw an interesting discussion


00:31:42.000 --> 00:31:43.509
online about the Australian accent


00:31:43.519 --> 00:31:45.909
changing over time, asking why when you


00:31:45.919 --> 00:31:49.110
watch Aussie films and TVs from 30, 40,


00:31:49.120 --> 00:31:51.110
50 years ago, everybody almost sounds


00:31:51.120 --> 00:31:52.230
like they're a pastiche of the


00:31:52.240 --> 00:31:54.710
Australian accent. It's so full on and


00:31:54.720 --> 00:31:57.110
there's so many terms and insults and


00:31:57.120 --> 00:31:59.190
stuff that aren't used today. Yeah.


00:31:59.200 --> 00:32:02.389
>> And apparently part of it is language


00:32:02.399 --> 00:32:03.350
evolves. We've got all these


00:32:03.360 --> 00:32:05.029
multicultural influence. We've got all


00:32:05.039 --> 00:32:06.870
that stuff. But also apparently the


00:32:06.880 --> 00:32:09.830
actors were trained to ham it up.


00:32:09.840 --> 00:32:12.310
>> Oh, absolutely. That's exactly what it


00:32:12.320 --> 00:32:14.230
was. And and uh see what you started,


00:32:14.240 --> 00:32:17.269
Paul. But uh I understand because I did


00:32:17.279 --> 00:32:18.870
some research on it. The Australian


00:32:18.880 --> 00:32:23.029
accent came about because we were


00:32:23.039 --> 00:32:25.750
a colony of convicts brought over from


00:32:25.760 --> 00:32:28.950
the UK, but the convicts were all from


00:32:28.960 --> 00:32:30.549
different walks of life, but they were


00:32:30.559 --> 00:32:33.669
conglomerated into a new community and


00:32:33.679 --> 00:32:36.070
all their accents merged into what is


00:32:36.080 --> 00:32:39.110
now the Australian accent. So you know


00:32:39.120 --> 00:32:41.990
you you you had Welsh, you had Irish,


00:32:42.000 --> 00:32:44.470
you had Scottish, you had English or


00:32:44.480 --> 00:32:46.789
with all the variations all coming


00:32:46.799 --> 00:32:48.950
together and creating the Australian


00:32:48.960 --> 00:32:51.190
accent. So that's why it is what it is.


00:32:51.200 --> 00:32:51.750
>> Yes.


00:32:51.760 --> 00:32:53.269
>> But it's ever evolving too.


00:32:53.279 --> 00:32:54.470
>> And it's a wonderful thing. It does


00:32:54.480 --> 00:32:56.389
change over time which I found


00:32:56.399 --> 00:32:58.149
interesting. Anyway, sorry about that.


00:32:58.159 --> 00:32:59.669
We get off topic wonderfully,


00:32:59.679 --> 00:33:00.630
wonderfully. Well, Saturn,


00:33:00.640 --> 00:33:02.070
>> we're good at that. So Fred started


00:33:02.080 --> 00:33:03.750
talking about the possibility of Titan


00:33:03.760 --> 00:33:06.310
and a Hyperion colliding and what


00:33:06.320 --> 00:33:08.549
happened to the stuff. Could a big rock


00:33:08.559 --> 00:33:10.710
from that event have hit Earth 65


00:33:10.720 --> 00:33:11.990
million years ago and you know what he's


00:33:12.000 --> 00:33:13.669
talking about there or did it all just


00:33:13.679 --> 00:33:15.830
go flying off into space or did it do


00:33:15.840 --> 00:33:18.310
something else etc etc.


00:33:18.320 --> 00:33:19.990
>> All all sorts of ways we can go with


00:33:20.000 --> 00:33:23.430
this. So the origin of Saturn's rings


00:33:23.440 --> 00:33:25.750
first and foremost is not yet


00:33:25.760 --> 00:33:27.350
definitively known. We know that there


00:33:27.360 --> 00:33:29.190
are ring systems around Jupiter, Uranus


00:33:29.200 --> 00:33:31.830
and Neptune as well. We suspect strongly


00:33:31.840 --> 00:33:34.630
that in the past and in the future Mars


00:33:34.640 --> 00:33:37.669
has had and will have ring rings. I


00:33:37.679 --> 00:33:40.070
think red dwarfy has will have possibly


00:33:40.080 --> 00:33:42.310
going to have whatever it it may have


00:33:42.320 --> 00:33:43.990
had episodic rings in the past. We've


00:33:44.000 --> 00:33:45.750
found rings around a few of the solstice


00:33:45.760 --> 00:33:47.509
from smaller objects like um the


00:33:47.519 --> 00:33:50.950
centaurs Chiron and Currico. Um rings


00:33:50.960 --> 00:33:52.230
are a thing. We've also found


00:33:52.240 --> 00:33:54.470
potentially rings around exoplanets.


00:33:54.480 --> 00:33:55.830
Some debate about that. We find rings


00:33:55.840 --> 00:33:58.149
around stars in the form of debris discs


00:33:58.159 --> 00:34:00.630
and all the rest of it. Yeah,


00:34:00.640 --> 00:34:03.190
ever since Saturn's rings were known,


00:34:03.200 --> 00:34:05.430
there's been ongoing how did they get


00:34:05.440 --> 00:34:08.069
there? And there is an ongoing not only


00:34:08.079 --> 00:34:09.190
how did they get there, but are they


00:34:09.200 --> 00:34:12.470
transient or permanent? And there are a


00:34:12.480 --> 00:34:14.869
wide variety of opinions on this and


00:34:14.879 --> 00:34:16.629
modeling has not yet come down strongly


00:34:16.639 --> 00:34:19.270
one way or the other. Currently, the


00:34:19.280 --> 00:34:20.950
best thinking about Saturn's rings is


00:34:20.960 --> 00:34:23.909
that they are more likely to be new than


00:34:23.919 --> 00:34:26.950
old. So we're probably seeing a ring


00:34:26.960 --> 00:34:29.829
system that has in bulk not existed


00:34:29.839 --> 00:34:32.149
since the birth of the solar system and


00:34:32.159 --> 00:34:35.270
estimates of the age range from 10 to


00:34:35.280 --> 00:34:38.629
100 to 300 million years. These


00:34:38.639 --> 00:34:40.790
estimates on the which the rings are


00:34:40.800 --> 00:34:43.430
being depleted suggest that they may


00:34:43.440 --> 00:34:45.669
well return to the level of Neptune,


00:34:45.679 --> 00:34:48.389
Uranus, Jupiter type rings within about


00:34:48.399 --> 00:34:52.069
300 million years from now. Those


00:34:52.079 --> 00:34:54.550
theories, those arguments


00:34:54.560 --> 00:34:56.470
would suggest that if the ring system is


00:34:56.480 --> 00:34:57.750
younger than the edge of the solar


00:34:57.760 --> 00:34:59.109
system, there had to be an event to


00:34:59.119 --> 00:35:01.589
bring it into being. Obviously, and


00:35:01.599 --> 00:35:03.829
there have been a number of different


00:35:03.839 --> 00:35:06.069
suggestions to cause this. One is that,


00:35:06.079 --> 00:35:08.470
and this was commonly argued when I was


00:35:08.480 --> 00:35:10.150
a kid learning about it, that Saturn had


00:35:10.160 --> 00:35:12.390
a comet or asteroid that got too close,


00:35:12.400 --> 00:35:14.230
was torn us under creating the rings.


00:35:14.240 --> 00:35:16.950
Now this invokes a part of planetary


00:35:16.960 --> 00:35:19.030
science knowledge and physics called the


00:35:19.040 --> 00:35:21.990
ro limit which is essentially if you


00:35:22.000 --> 00:35:24.390
have two massive objects and you bring


00:35:24.400 --> 00:35:26.870
them close enough together tidal effects


00:35:26.880 --> 00:35:29.910
will disrupt the smaller of them due to


00:35:29.920 --> 00:35:31.829
the gravity of the bigger of them. And


00:35:31.839 --> 00:35:33.750
the point there is if you think that the


00:35:33.760 --> 00:35:35.349
strength of the gravitational pull falls


00:35:35.359 --> 00:35:37.349
off as a square of the distance and


00:35:37.359 --> 00:35:39.109
you've got an object that's 100 km


00:35:39.119 --> 00:35:41.510
across, the side that is nearer a planet


00:35:41.520 --> 00:35:43.030
will be feeling a stronger pull than the


00:35:43.040 --> 00:35:45.349
side that's further away. Now depending


00:35:45.359 --> 00:35:47.910
on the strength of the object, that


00:35:47.920 --> 00:35:49.430
distance will vary. The stronger the


00:35:49.440 --> 00:35:51.670
object is, the closer it can get to a


00:35:51.680 --> 00:35:53.589
planet before disruption. But we have


00:35:53.599 --> 00:35:54.950
this concept of the ro limit. And


00:35:54.960 --> 00:35:57.190
Saturn's rings are within the ro limit,


00:35:57.200 --> 00:35:58.950
which is why they've been disrupted. And


00:35:58.960 --> 00:36:01.670
the largest objects in them are probably


00:36:01.680 --> 00:36:03.750
to be honest the shepherd moons that are


00:36:03.760 --> 00:36:06.150
kilometer scale objects which are


00:36:06.160 --> 00:36:08.310
probably due to the nature of the ro


00:36:08.320 --> 00:36:11.109
limit and stuff they're probably fairly


00:36:11.119 --> 00:36:12.710
rubbish rather than rubble panels


00:36:12.720 --> 00:36:13.829
because if they were rubble panels


00:36:13.839 --> 00:36:16.230
they'd get disintegrated. Um, so they're


00:36:16.240 --> 00:36:18.310
probably at a distance where they are


00:36:18.320 --> 00:36:20.790
within the ro limit for a fluid object


00:36:20.800 --> 00:36:22.069
that has no strength, but they are


00:36:22.079 --> 00:36:23.589
strong enough that the ro limit for them


00:36:23.599 --> 00:36:24.950
will be closer in. Anyway, a bit off


00:36:24.960 --> 00:36:26.550
topic there, but that's the physics


00:36:26.560 --> 00:36:28.790
behind it. And you can work out that ro


00:36:28.800 --> 00:36:30.870
limit either as a ratio of the mass of


00:36:30.880 --> 00:36:32.710
the object to the mass of the thing it's


00:36:32.720 --> 00:36:34.069
the bigger thing that it's coming near


00:36:34.079 --> 00:36:36.790
or as a ratio of the densities. It works


00:36:36.800 --> 00:36:40.710
either way, which is kind of cool. Um,


00:36:40.720 --> 00:36:43.349
that's what


00:36:43.359 --> 00:36:45.349
the physics is behind why you don't have


00:36:45.359 --> 00:36:46.790
a single object there. It can't form a


00:36:46.800 --> 00:36:48.710
single object. It's got to be broken up


00:36:48.720 --> 00:36:51.510
into debris. The rings are decaying.


00:36:51.520 --> 00:36:53.750
Dust is lost to Saturn all the time.


00:36:53.760 --> 00:36:55.510
They're also being slightly replenished


00:36:55.520 --> 00:36:56.790
by the activity particularly of


00:36:56.800 --> 00:36:58.390
Enceladus


00:36:58.400 --> 00:37:00.550
um, which is repopulating the earrings.


00:37:00.560 --> 00:37:03.510
So, there are system in flux and it's


00:37:03.520 --> 00:37:05.430
not clear exactly where they formed.


00:37:05.440 --> 00:37:07.109
There was the idea when I was a kid that


00:37:07.119 --> 00:37:08.950
it was a comed asteroid that was


00:37:08.960 --> 00:37:11.270
disrupted to make that much material. I


00:37:11.280 --> 00:37:13.829
think that has gone probably by the


00:37:13.839 --> 00:37:16.550
wayside because you need a way to


00:37:16.560 --> 00:37:18.950
dissipate the energy for an object to be


00:37:18.960 --> 00:37:21.270
captured. So if you have a comet or an


00:37:21.280 --> 00:37:22.870
asteroid get close enough to Saturn to


00:37:22.880 --> 00:37:25.670
be torn apart, that material is still


00:37:25.680 --> 00:37:27.109
moving faster than Saturn's escape


00:37:27.119 --> 00:37:29.030
velocity. So we just fly away, albeit


00:37:29.040 --> 00:37:29.829
torn apart.


00:37:29.839 --> 00:37:31.750
>> Right? If you have something that is


00:37:31.760 --> 00:37:34.470
temporarily captured as a satellite,


00:37:34.480 --> 00:37:36.310
it'll be on a fairly elongated orbit if


00:37:36.320 --> 00:37:37.510
it's going to get close enough to be


00:37:37.520 --> 00:37:39.430
disrupted and it will continue to follow


00:37:39.440 --> 00:37:41.030
that. So if you look at comet Schumac


00:37:41.040 --> 00:37:44.310
119 back in the 1990s, it came very


00:37:44.320 --> 00:37:46.870
close to Jupiter in 1992, I think, was


00:37:46.880 --> 00:37:48.870
torn apart so that we had many smaller


00:37:48.880 --> 00:37:50.790
comets that all followed essentially the


00:37:50.800 --> 00:37:53.829
same art orbit in a lengthy chain and


00:37:53.839 --> 00:37:56.069
fell apart, crashed into Jupiter one


00:37:56.079 --> 00:37:57.510
after the other over the space of a


00:37:57.520 --> 00:37:58.950
couple of weeks in 1994.


00:37:58.960 --> 00:38:01.109
>> That's right. They didn't form a ring


00:38:01.119 --> 00:38:02.069
system.


00:38:02.079 --> 00:38:02.390
>> No.


00:38:02.400 --> 00:38:04.390
>> When that had its first approach to


00:38:04.400 --> 00:38:06.710
Jupiter, it was torn apart, but it


00:38:06.720 --> 00:38:08.790
didn't make a new ring system. So, you


00:38:08.800 --> 00:38:10.470
need some way to dissipate the energy to


00:38:10.480 --> 00:38:11.910
trap all the debris onto a circular


00:38:11.920 --> 00:38:13.910
orbit near the planet. And it's very


00:38:13.920 --> 00:38:15.349
hard to visualize how you do that from


00:38:15.359 --> 00:38:17.670
an asteroid or comet passing through.


00:38:17.680 --> 00:38:21.109
So, that's led to instead the idea of


00:38:21.119 --> 00:38:23.030
the collision between two moons. Now,


00:38:23.040 --> 00:38:25.190
the most recent version I've seen


00:38:25.200 --> 00:38:28.550
discussed of this is that there was a


00:38:28.560 --> 00:38:31.349
moon that was possibly as large as


00:38:31.359 --> 00:38:34.069
Hyperion or even bigger


00:38:34.079 --> 00:38:37.510
that collided that sorry, whose orbit


00:38:37.520 --> 00:38:39.349
spiraled inwards to the point it crossed


00:38:39.359 --> 00:38:41.910
the ro limit. Now, we're seeing this


00:38:41.920 --> 00:38:44.069
happen with Phoebe, the innermost of


00:38:44.079 --> 00:38:46.630
Mars's two moons. Phoebe is closer to


00:38:46.640 --> 00:38:49.270
Mars than what we call the co- rotation


00:38:49.280 --> 00:38:51.589
altitude, which means its orbit around


00:38:51.599 --> 00:38:53.750
Mars takes less time than Mars takes to


00:38:53.760 --> 00:38:55.829
spin. And when you're closer than that


00:38:55.839 --> 00:38:57.750
co- rotation place, tidal forces will


00:38:57.760 --> 00:38:59.270
make you spiral inwards rather than


00:38:59.280 --> 00:39:00.870
spiraling outwards. Our moon's further


00:39:00.880 --> 00:39:02.870
out. It takes longer to orbit the Earth


00:39:02.880 --> 00:39:04.710
than the Earth takes to spin. So, it


00:39:04.720 --> 00:39:05.510
moves away.


00:39:05.520 --> 00:39:09.589
>> Yeah. Imagine then that you had a moon


00:39:09.599 --> 00:39:12.470
few hundred km across 200 300 400 km


00:39:12.480 --> 00:39:16.069
across close in that spiraled inwards


00:39:16.079 --> 00:39:17.589
and cross the ro limit it would be


00:39:17.599 --> 00:39:19.910
disrupted forming system that's one


00:39:19.920 --> 00:39:21.910
theory another is that you had a moon


00:39:21.920 --> 00:39:24.470
that was pretty close in that was then


00:39:24.480 --> 00:39:26.630
struck by an object large enough to


00:39:26.640 --> 00:39:30.550
shatter and disrupt it. that collisions


00:39:30.560 --> 00:39:33.270
of that size would be relatively rare


00:39:33.280 --> 00:39:34.870
these days because projectiles big


00:39:34.880 --> 00:39:37.109
enough to shatter a moon of that size


00:39:37.119 --> 00:39:40.630
are relatively scarce. Um, a more more


00:39:40.640 --> 00:39:42.390
recent version that's been proposed is


00:39:42.400 --> 00:39:44.790
that you had a much larger object,


00:39:44.800 --> 00:39:46.870
something more like the size of Titan


00:39:46.880 --> 00:39:49.109
and that was stripped off during the


00:39:49.119 --> 00:39:50.710
formation period of Saturn. There's all


00:39:50.720 --> 00:39:53.030
sorts of theories here, but like I say,


00:39:53.040 --> 00:39:54.710
we're not fully there yet. We're still


00:39:54.720 --> 00:39:57.190
exploring. That's where future missions


00:39:57.200 --> 00:39:59.109
to Saturn are going to teach us a lot


00:39:59.119 --> 00:40:02.470
more. Um, we've got an age here. Um,


00:40:02.480 --> 00:40:05.349
observations based on the KEK telescope


00:40:05.359 --> 00:40:07.510
suggests that the rings will be gone in


00:40:07.520 --> 00:40:09.190
292


00:40:09.200 --> 00:40:12.870
plus 818US 124 million years, which


00:40:12.880 --> 00:40:14.550
illustrates that as astronomers, we are


00:40:14.560 --> 00:40:16.550
terrible at choosing significant


00:40:16.560 --> 00:40:18.069
figures. And I tell my students this all


00:40:18.079 --> 00:40:19.829
the time because if you talk to a


00:40:19.839 --> 00:40:21.349
physicist, they'd see those numbers and


00:40:21.359 --> 00:40:23.030
weep because they'd say, "Well, that


00:40:23.040 --> 00:40:25.589
should just be 300 plus 800 minus 100


00:40:25.599 --> 00:40:26.470
because the other numbers are


00:40:26.480 --> 00:40:29.829
meaningless anyway." Um, but it's a very


00:40:29.839 --> 00:40:31.829
large uncertainty on how long they will


00:40:31.839 --> 00:40:33.910
take till they're gone. We don't know


00:40:33.920 --> 00:40:36.710
how massive they were initially, and how


00:40:36.720 --> 00:40:39.589
massive they are initially will be part


00:40:39.599 --> 00:40:41.670
of what determines


00:40:41.680 --> 00:40:43.270
how long they've been around.


00:40:43.280 --> 00:40:45.510
>> Uhhuh. Anyway, so that's why there's


00:40:45.520 --> 00:40:47.109
still a lot of misunderstanding and a


00:40:47.119 --> 00:40:49.109
lot of confusion there. And it may well


00:40:49.119 --> 00:40:51.510
be that rings of the scale of the rings


00:40:51.520 --> 00:40:53.109
of Saturn around the giant planets are


00:40:53.119 --> 00:40:55.910
an episodic thing. It may well be that


00:40:55.920 --> 00:40:58.150
planets like Saturn, Jupiter, Uranus,


00:40:58.160 --> 00:41:00.790
and Neptune have minor ring systems all


00:41:00.800 --> 00:41:02.150
the time, but occasionally they'll get a


00:41:02.160 --> 00:41:03.589
really good one. And it could be that in


00:41:03.599 --> 00:41:05.109
the past Jupiter had a massive ring


00:41:05.119 --> 00:41:07.750
system like this. And in the future,


00:41:07.760 --> 00:41:10.150
Uranus might, for example, Mars will


00:41:10.160 --> 00:41:11.990
probably get a ring system when um


00:41:12.000 --> 00:41:13.430
Phobos gets close enough and is


00:41:13.440 --> 00:41:15.109
disrupted.


00:41:15.119 --> 00:41:17.589
>> All that now to aside, the next part was


00:41:17.599 --> 00:41:20.950
about debris reaching us from the


00:41:20.960 --> 00:41:23.670
collision and reaching the Earth.


00:41:23.680 --> 00:41:24.069
>> Yeah.


00:41:24.079 --> 00:41:28.550
>> Um two parts to this. The first is that


00:41:28.560 --> 00:41:31.349
some material from that collision could


00:41:31.359 --> 00:41:32.790
potentially have reached Earth. I don't


00:41:32.800 --> 00:41:35.109
doubt that. I did work while I was at


00:41:35.119 --> 00:41:36.710
the University of Burn, which we talked


00:41:36.720 --> 00:41:39.430
about earlier, with a PhD student at the


00:41:39.440 --> 00:41:41.190
time called Augustine Anich, who was


00:41:41.200 --> 00:41:44.790
doing simulations of the giant collision


00:41:44.800 --> 00:41:46.550
that made Mercury the planet we know it


00:41:46.560 --> 00:41:49.190
is today. Mercury is over dense. It has


00:41:49.200 --> 00:41:51.430
an oversized core. And the thinking is


00:41:51.440 --> 00:41:53.670
it was probably once a planet twice the


00:41:53.680 --> 00:41:56.150
diameter of the current Mercury. And it


00:41:56.160 --> 00:41:58.230
had this massive collision that stripped


00:41:58.240 --> 00:41:59.589
it of its mantle and crust, leaving


00:41:59.599 --> 00:42:00.870
behind a core with a little bit of


00:42:00.880 --> 00:42:02.710
rubble on top. and he was doing


00:42:02.720 --> 00:42:05.510
simulations of that impact.


00:42:05.520 --> 00:42:07.829
And my contribution was I ran orbital


00:42:07.839 --> 00:42:09.670
mechanics simulations. This is kind of


00:42:09.680 --> 00:42:11.349
core to my day-to-day work. This is what


00:42:11.359 --> 00:42:13.990
I've done all through my career. And I


00:42:14.000 --> 00:42:16.550
said, where would the ejector go? If you


00:42:16.560 --> 00:42:18.390
have a collision like that, some of the


00:42:18.400 --> 00:42:20.230
material ejected will be traveling at


00:42:20.240 --> 00:42:21.990
less than the escape velocity for all of


00:42:22.000 --> 00:42:23.589
the mass that's around. So that material


00:42:23.599 --> 00:42:26.069
won't be lost and it would either in the


00:42:26.079 --> 00:42:27.589
case of the earth moon collision form a


00:42:27.599 --> 00:42:29.829
satellite like the moon or fall back and


00:42:29.839 --> 00:42:32.150
contribute to the reacion.


00:42:32.160 --> 00:42:34.550
>> Material traveling above the escape


00:42:34.560 --> 00:42:37.109
velocity will escape and go into orbit


00:42:37.119 --> 00:42:39.430
around the sun. And at that point it is


00:42:39.440 --> 00:42:41.030
subject to all of the dynamics that goes


00:42:41.040 --> 00:42:42.870
on the grav gravitational interactions


00:42:42.880 --> 00:42:45.109
with all the other planets. And I ran


00:42:45.119 --> 00:42:47.030
simulations of the ejector to see what


00:42:47.040 --> 00:42:49.349
their eventual fates would be where they


00:42:49.359 --> 00:42:51.270
would wind up. The majority of the


00:42:51.280 --> 00:42:52.630
ejector from the mercury forming


00:42:52.640 --> 00:42:55.430
collision hit the sun or was flung from


00:42:55.440 --> 00:42:57.829
the solar system never to return as a as


00:42:57.839 --> 00:42:59.829
a final fate. That's where it ended up.


00:42:59.839 --> 00:43:01.750
But about 2% of the material ejected


00:43:01.760 --> 00:43:03.990
from Mercury would have landed on Earth.


00:43:04.000 --> 00:43:04.309
>> Oh.


00:43:04.319 --> 00:43:06.150
>> So we will have been polluted by the


00:43:06.160 --> 00:43:08.790
Mercury forming impact by what you


00:43:08.800 --> 00:43:11.190
describe as herian material. If if we


00:43:11.200 --> 00:43:14.630
were talking about Venus being venerial


00:43:14.640 --> 00:43:16.550
material which then became Venian


00:43:16.560 --> 00:43:18.870
material, Mars being Martian, Jupiter


00:43:18.880 --> 00:43:22.150
being Jovian for Mercury, Mercurian


00:43:22.160 --> 00:43:23.270
never quite worked. So a lot of people


00:43:23.280 --> 00:43:25.829
used to call it herian um the


00:43:25.839 --> 00:43:27.430
traditional name for but anyway the


00:43:27.440 --> 00:43:28.950
material from Mercury about 2% of it


00:43:28.960 --> 00:43:31.190
would have rained down on the earth. Now


00:43:31.200 --> 00:43:34.069
this ties into the work that I've talked


00:43:34.079 --> 00:43:36.390
about before about panspermia as well.


00:43:36.400 --> 00:43:39.430
Material ejected from one planet becomes


00:43:39.440 --> 00:43:41.430
objects moving freely within the solar


00:43:41.440 --> 00:43:44.790
system subject to the gravitational


00:43:44.800 --> 00:43:47.670
pinball that goes on. If you have a


00:43:47.680 --> 00:43:50.710
collision in orbit around Saturn, if it


00:43:50.720 --> 00:43:52.390
is a collision between two of Saturn's


00:43:52.400 --> 00:43:55.030
moons, the overwhelmingly vast majority


00:43:55.040 --> 00:43:57.030
of ejector will stay bound in the Saturn


00:43:57.040 --> 00:43:58.870
system because the moons are both


00:43:58.880 --> 00:44:00.870
themselves very deep in Saturn's gravity


00:44:00.880 --> 00:44:04.150
while very tightly held. So the vast


00:44:04.160 --> 00:44:05.829
majority of ejector from two moons


00:44:05.839 --> 00:44:07.910
colliding with each other will be kept


00:44:07.920 --> 00:44:09.910
in house.


00:44:09.920 --> 00:44:12.390
But that's not all of it. Also some of


00:44:12.400 --> 00:44:14.870
that ejector that ejector in the Saturn


00:44:14.880 --> 00:44:16.230
system will be like ejector in the solar


00:44:16.240 --> 00:44:17.589
system. It'll be bounced around and


00:44:17.599 --> 00:44:18.870
moved around by the gravity of the


00:44:18.880 --> 00:44:21.349
moons. So a small tiny fraction of it


00:44:21.359 --> 00:44:22.870
could eventually be ejected that way as


00:44:22.880 --> 00:44:25.589
well. If you have a collision that


00:44:25.599 --> 00:44:27.910
instead involves or invokes an object


00:44:27.920 --> 00:44:29.750
that is not currently orbiting Saturn


00:44:29.760 --> 00:44:31.349
but is a comet or an asteroid passing


00:44:31.359 --> 00:44:33.829
through that object itself is moving


00:44:33.839 --> 00:44:35.190
faster than the escape velocity of


00:44:35.200 --> 00:44:36.630
Saturn. So a significant amount of the


00:44:36.640 --> 00:44:39.430
ejector also will be that case you'll


00:44:39.440 --> 00:44:41.510
get more material put into orbit around


00:44:41.520 --> 00:44:43.990
the sun. Once the material has escaped


00:44:44.000 --> 00:44:46.710
from Saturn it is moving on an orbit


00:44:46.720 --> 00:44:48.470
that makes it one of the centaurs. And


00:44:48.480 --> 00:44:49.829
the centaurs are one of my favorite


00:44:49.839 --> 00:44:51.990
populations of objects anyway because


00:44:52.000 --> 00:44:53.670
they're what I studied for my PhD and I


00:44:53.680 --> 00:44:55.510
did the same dynamic simulations of


00:44:55.520 --> 00:44:56.870
them. Where do they come from? Where are


00:44:56.880 --> 00:44:59.270
they going? How will they get there? The


00:44:59.280 --> 00:45:01.349
centaurs are the parent population of


00:45:01.359 --> 00:45:03.910
the short period comets. The centaurs


00:45:03.920 --> 00:45:08.150
themselves are daughters, sons, children


00:45:08.160 --> 00:45:10.550
of the transep union objects moving


00:45:10.560 --> 00:45:11.829
around in the out solar system being


00:45:11.839 --> 00:45:14.870
scattered inwards. In my simulations of


00:45:14.880 --> 00:45:17.910
the Centaurs, about onethird of Centos,


00:45:17.920 --> 00:45:19.750
which is about onethird of those objects


00:45:19.760 --> 00:45:21.030
between the orbits of Jupiter and


00:45:21.040 --> 00:45:22.870
Neptune that are on unstable orbits,


00:45:22.880 --> 00:45:24.309
about onethird of them will eventually


00:45:24.319 --> 00:45:25.829
become a Jupiter family comet, will be


00:45:25.839 --> 00:45:27.109
flung into the inner solar system,


00:45:27.119 --> 00:45:29.349
usually by Jupiter, which means it'll be


00:45:29.359 --> 00:45:31.670
put onto an Earth crossing orbit, which


00:45:31.680 --> 00:45:34.150
means that if you eject enough material


00:45:34.160 --> 00:45:37.109
from the Saturn system,


00:45:37.119 --> 00:45:38.950
some of it will hit the Earthh.


00:45:38.960 --> 00:45:41.829
>> It'll be a vanishingly small amount. It


00:45:41.839 --> 00:45:44.230
is unlikely though that you'll get a


00:45:44.240 --> 00:45:45.910
chunk big enough to cause a mass


00:45:45.920 --> 00:45:49.349
extinction making it all that far. You


00:45:49.359 --> 00:45:51.109
the thing that killed the dinosaurs was


00:45:51.119 --> 00:45:53.430
about 10 km across. We think maybe even


00:45:53.440 --> 00:45:55.510
a little bit bigger. That's a very very


00:45:55.520 --> 00:45:58.150
very big bit of stuff. Now obviously


00:45:58.160 --> 00:45:59.349
there's a small chance it could have


00:45:59.359 --> 00:46:01.190
been the result of something like that.


00:46:01.200 --> 00:46:03.190
There are suggestions that the thing


00:46:03.200 --> 00:46:04.870
that killed off the dinosaurs might have


00:46:04.880 --> 00:46:07.190
been an asteroid that was probably


00:46:07.200 --> 00:46:08.630
produced in a collision in the asteroid


00:46:08.640 --> 00:46:10.069
belt and been a member of one of the


00:46:10.079 --> 00:46:11.430
collisional families that feed material


00:46:11.440 --> 00:46:13.430
to the inner solar system. Others have


00:46:13.440 --> 00:46:15.349
suggested it could be a comet.


00:46:15.359 --> 00:46:17.670
>> It could potentially have been a


00:46:17.680 --> 00:46:20.870
fragment of a a smashed moon like Paul


00:46:20.880 --> 00:46:22.950
is suggesting. It could have been a very


00:46:22.960 --> 00:46:24.550
ancient fragment of the Mercury


00:46:24.560 --> 00:46:25.990
collision that had managed to survive 4


00:46:26.000 --> 00:46:27.510
billion years. But that's vanishingly


00:46:27.520 --> 00:46:29.670
unlikely because things are rejected on


00:46:29.680 --> 00:46:31.030
a much shorter time scale. So there'll


00:46:31.040 --> 00:46:33.430
be nothing left effectively. But we


00:46:33.440 --> 00:46:36.069
don't know. That's a fundamental thing.


00:46:36.079 --> 00:46:38.309
What drives the understanding that the


00:46:38.319 --> 00:46:41.430
impact itself was extraterrestrial was


00:46:41.440 --> 00:46:43.510
initially the iridium layer that was


00:46:43.520 --> 00:46:44.870
found globally. That was kind of a bit


00:46:44.880 --> 00:46:46.870
of a smoking gun at the point of the


00:46:46.880 --> 00:46:48.390
mass extinction in the fossil record.


00:46:48.400 --> 00:46:51.270
They found the crater. You cannot tell


00:46:51.280 --> 00:46:54.150
from the crater's size alone what the


00:46:54.160 --> 00:46:56.069
nature of the impactor was or the impact


00:46:56.079 --> 00:46:59.510
speed. Now for a crater that old it's a


00:46:59.520 --> 00:47:01.750
bit bit impossible to do anyway. I've


00:47:01.760 --> 00:47:03.589
been really interested and we've never


00:47:03.599 --> 00:47:05.910
got round to doing this as research to


00:47:05.920 --> 00:47:07.510
talk with people like the create


00:47:07.520 --> 00:47:09.430
accounting people to see if there is any


00:47:09.440 --> 00:47:10.870
way for bodies like the moon or Mars


00:47:10.880 --> 00:47:13.109
where there's much less weathering to


00:47:13.119 --> 00:47:14.790
distinguish between a cometary or


00:47:14.800 --> 00:47:18.630
asteroidal impact on the basis of


00:47:18.640 --> 00:47:21.190
whether the speeds influence on the


00:47:21.200 --> 00:47:24.150
kinetic energy of the impact can modify


00:47:24.160 --> 00:47:26.550
the crater formation process. probably


00:47:26.560 --> 00:47:27.990
it can't because effectively you're


00:47:28.000 --> 00:47:30.230
dumping X energy into the surface and


00:47:30.240 --> 00:47:32.870
that's what makes the crater but I've


00:47:32.880 --> 00:47:34.150
been interested in that but what that


00:47:34.160 --> 00:47:35.589
means from the Earth's point of view is


00:47:35.599 --> 00:47:37.829
that from the morphology of the crater


00:47:37.839 --> 00:47:39.990
from what's left from that impact we


00:47:40.000 --> 00:47:41.670
cannot tell what the impact was or how


00:47:41.680 --> 00:47:43.910
fast it's traveling had to be faster


00:47:43.920 --> 00:47:45.190
than the escape velocity of the earth


00:47:45.200 --> 00:47:47.030
because it came from beyond the earth so


00:47:47.040 --> 00:47:49.829
the minimum speed is 12 km a second it


00:47:49.839 --> 00:47:52.470
is almost guaranteed that it was a solar


00:47:52.480 --> 00:47:54.230
system object not an interstellar comet


00:47:54.240 --> 00:47:56.309
like comet Atlas Which means that the


00:47:56.319 --> 00:47:58.230
maximum speed it could have hit us is 72


00:47:58.240 --> 00:48:02.630
km a second which is you get that number


00:48:02.640 --> 00:48:04.230
by combining the orbital speed of the


00:48:04.240 --> 00:48:06.150
earth which is 30 km a second going


00:48:06.160 --> 00:48:08.390
forward with the maximum speed that


00:48:08.400 --> 00:48:09.589
something could be traveling at one


00:48:09.599 --> 00:48:11.990
astronomical unit at our location and


00:48:12.000 --> 00:48:13.750
still be bound to the sun which if you


00:48:13.760 --> 00:48:16.230
work out the velocity if you're going at


00:48:16.240 --> 00:48:19.190
42 km a second at the location of the


00:48:19.200 --> 00:48:20.470
earth's orbit you're right on the


00:48:20.480 --> 00:48:22.390
boundary between the solar systems


00:48:22.400 --> 00:48:24.549
escape velocity and not so anything


00:48:24.559 --> 00:48:26.870
faster than that will escape. Take those


00:48:26.880 --> 00:48:28.069
two numbers and say, "Right, you've got


00:48:28.079 --> 00:48:30.470
an op object coming head on at the


00:48:30.480 --> 00:48:32.790
fastest speed it could have and stay


00:48:32.800 --> 00:48:35.829
bound to the solar system. 42 km a


00:48:35.839 --> 00:48:37.670
second one way, 30 km a second the other


00:48:37.680 --> 00:48:40.710
way gives you 72 km a second. So we know


00:48:40.720 --> 00:48:43.109
the velocity with which the signal was


00:48:43.119 --> 00:48:45.349
coming in within a factor of six. Most


00:48:45.359 --> 00:48:46.950
likely at the lower end because we get


00:48:46.960 --> 00:48:48.790
more asteroidal impactors and cometry


00:48:48.800 --> 00:48:51.510
ones, but we don't really have much more


00:48:51.520 --> 00:48:53.109
than that on the composition of it.


00:48:53.119 --> 00:48:55.910
There is a lot of debate over whether it


00:48:55.920 --> 00:48:58.790
was cometry, whether it was asteroidal.


00:48:58.800 --> 00:49:02.549
An object from from part of one of the


00:49:02.559 --> 00:49:05.910
moons of Saturn would be iceer rich and


00:49:05.920 --> 00:49:07.349
so it would look like a cometary


00:49:07.359 --> 00:49:10.230
impactor. So I'm not sure for an impact


00:49:10.240 --> 00:49:13.109
65 million years old whether we would


00:49:13.119 --> 00:49:15.589
ever be able to distinguish be between a


00:49:15.599 --> 00:49:17.030
fragment of one of the moons of Saturn


00:49:17.040 --> 00:49:20.390
as the impactor and a comet as the


00:49:20.400 --> 00:49:24.390
impactor. Um, I I just have no idea how


00:49:24.400 --> 00:49:25.990
we would do that. What we would probably


00:49:26.000 --> 00:49:28.390
be able to do is if we went to a


00:49:28.400 --> 00:49:30.390
near-Earth object, whether it's a comet


00:49:30.400 --> 00:49:33.829
or an asteroid, and took samples, there


00:49:33.839 --> 00:49:36.069
is a potential that then maybe through


00:49:36.079 --> 00:49:38.150
isotopic analysis, we could tell that


00:49:38.160 --> 00:49:41.109
something was a fragment of a Saturnian


00:49:41.119 --> 00:49:43.430
moon, but we need things to compare that


00:49:43.440 --> 00:49:45.829
to. That is very much on the very


00:49:45.839 --> 00:49:47.270
fringes of what we can do. But we do


00:49:47.280 --> 00:49:49.910
that a little bit with some meteorites.


00:49:49.920 --> 00:49:51.030
There's a couple of families of


00:49:51.040 --> 00:49:52.549
meteorites where we think we know the


00:49:52.559 --> 00:49:55.589
parent object. And these meteorites are


00:49:55.599 --> 00:49:58.150
compositionally grouped together with


00:49:58.160 --> 00:49:59.510
such tightness that they are


00:49:59.520 --> 00:50:01.910
distinguishable against the compositions


00:50:01.920 --> 00:50:03.270
of everything as a background. It's like


00:50:03.280 --> 00:50:04.950
if you measure the composition of


00:50:04.960 --> 00:50:06.549
everything and they're points on a wall,


00:50:06.559 --> 00:50:07.990
these ones all group together. So they


00:50:08.000 --> 00:50:10.150
come from the same parent. But I don't


00:50:10.160 --> 00:50:13.030
know how we could


00:50:13.040 --> 00:50:15.589
figure out whether it was a fragment of


00:50:15.599 --> 00:50:19.190
a Saturnian moon versus a comet. If we


00:50:19.200 --> 00:50:20.150
got to the point where we could


00:50:20.160 --> 00:50:22.790
distinguish comet versus asteroid, I


00:50:22.800 --> 00:50:24.150
think the argument will be it's a


00:50:24.160 --> 00:50:26.950
commentary body probably um but we


00:50:26.960 --> 00:50:28.150
couldn't tell you whether it's short or


00:50:28.160 --> 00:50:29.589
a long period comet. But people will


00:50:29.599 --> 00:50:31.349
probably come down on the cometry


00:50:31.359 --> 00:50:33.750
explanation rather than the fragment of


00:50:33.760 --> 00:50:35.910
a moon explanation because of the Okam's


00:50:35.920 --> 00:50:37.990
razor thing. So if you've got two


00:50:38.000 --> 00:50:39.750
explanations that are equally good at


00:50:39.760 --> 00:50:41.270
explaining the story, take the one


00:50:41.280 --> 00:50:42.230
that's simpler. Yeah,


00:50:42.240 --> 00:50:43.589
>> that might not be AM's razor, but that's


00:50:43.599 --> 00:50:45.190
one of those philosophical constructs


00:50:45.200 --> 00:50:49.750
that, you know, it's a more complex and


00:50:49.760 --> 00:50:51.349
challenging route to get a fragment of a


00:50:51.359 --> 00:50:52.630
Saturnian satellite to kill the


00:50:52.640 --> 00:50:54.950
dinosaurs than it is to have it just be


00:50:54.960 --> 00:50:55.910
a normal comet.


00:50:55.920 --> 00:50:58.549
>> Yeah, fair enough. All right, very good.


00:50:58.559 --> 00:51:01.670
Um, thank you, Paul. I think we covered


00:51:01.680 --> 00:51:04.470
that uh topic very, very well. And hope


00:51:04.480 --> 00:51:08.230
all's well in Queensland. Hey, uh we're


00:51:08.240 --> 00:51:10.390
going to take a breath and then uh we'll


00:51:10.400 --> 00:51:12.870
quickly go into our final question here


00:51:12.880 --> 00:51:17.670
on Space Nuts


00:51:17.680 --> 00:51:18.950
and I feel fine.


00:51:18.960 --> 00:51:20.150
>> Space Nuts


00:51:20.160 --> 00:51:23.430
>> and we're with Professor Jyer today with


00:51:23.440 --> 00:51:27.030
Fred away. Uh a Q&A edition. Uh one last


00:51:27.040 --> 00:51:28.710
question. Uh we'll have to make it quick


00:51:28.720 --> 00:51:30.069
because I think we've really burnt the


00:51:30.079 --> 00:51:31.670
clock today. Too much talking about


00:51:31.680 --> 00:51:33.670
accents. I think uh I have a question.


00:51:33.680 --> 00:51:35.910
Talking. I was just going to say talking


00:51:35.920 --> 00:51:39.190
accents. Get Fred to single climb


00:51:39.200 --> 00:51:41.030
>> cuz he's from my neck of the woods


00:51:41.040 --> 00:51:41.750
originally.


00:51:41.760 --> 00:51:44.870
>> Okay. Uh I have a question that might


00:51:44.880 --> 00:51:47.270
come across as lame or childish. Yes, it


00:51:47.280 --> 00:51:49.670
did. No. No, it didn't. Uh, but I'm


00:51:49.680 --> 00:51:52.390
hoping that a professor and a genuine


00:51:52.400 --> 00:51:57.030
space nut uh or I'm hoping that asking a


00:51:57.040 --> 00:51:59.190
professor and a genuine space nut this


00:51:59.200 --> 00:52:01.750
question, it might prompt uh for much


00:52:01.760 --> 00:52:03.829
more interesting answer than the average


00:52:03.839 --> 00:52:06.230
Joe. What is your favorite planet in our


00:52:06.240 --> 00:52:08.470
solar system and why? I wish I could


00:52:08.480 --> 00:52:10.230
give you an interesting answer myself. I


00:52:10.240 --> 00:52:12.630
do find Jupiter fascinating and Europa.


00:52:12.640 --> 00:52:15.109
Okay, you know, I know it's a moon, but


00:52:15.119 --> 00:52:17.109
I'm intrigued by what could be under all


00:52:17.119 --> 00:52:19.349
that ice. Hopefully, um, we'll find out


00:52:19.359 --> 00:52:21.190
in my lifetime. So, yeah, childish


00:52:21.200 --> 00:52:22.870
question from a 40-year-old, but


00:52:22.880 --> 00:52:25.430
hopefully you can turn it into a more


00:52:25.440 --> 00:52:27.349
deep and meaningful answer. That's Dan


00:52:27.359 --> 00:52:28.870
from the Gold Coast, also a


00:52:28.880 --> 00:52:30.470
Queenslander.


00:52:30.480 --> 00:52:32.870
Um, I can go first and be very quick.


00:52:32.880 --> 00:52:35.589
I'm fascinated by Mars. I just find the


00:52:35.599 --> 00:52:37.109
geography


00:52:37.119 --> 00:52:40.950
um outstanding. a smaller planet than


00:52:40.960 --> 00:52:44.390
Earth uh with geographic


00:52:44.400 --> 00:52:46.390
um highlights that are just


00:52:46.400 --> 00:52:50.390
mind-bogglingly huge like the Olympus


00:52:50.400 --> 00:52:52.549
Mons for example that that is a volcano


00:52:52.559 --> 00:52:54.470
that is it's the biggest in the solar


00:52:54.480 --> 00:52:58.790
system and um I think it is so high that


00:52:58.800 --> 00:53:00.549
it's actually sticking out of Earth's


00:53:00.559 --> 00:53:02.950
out of Mars's atmosphere.


00:53:02.960 --> 00:53:05.430
um the the the canyons on Mars and


00:53:05.440 --> 00:53:07.750
there's more than one but there's the


00:53:07.760 --> 00:53:10.470
the biggest one dwarfs the Grand Canyon


00:53:10.480 --> 00:53:12.390
on Earth like I think you can fit the


00:53:12.400 --> 00:53:13.829
Grand Canyon in one of one of its


00:53:13.839 --> 00:53:15.510
tributaries


00:53:15.520 --> 00:53:19.109
um and the list goes on. It is a f a


00:53:19.119 --> 00:53:20.790
fascinating planet. I always like to


00:53:20.800 --> 00:53:22.790
think of it as um that was God's first


00:53:22.800 --> 00:53:25.030
attempt and he stuffed it up and then we


00:53:25.040 --> 00:53:27.030
came next.


00:53:27.040 --> 00:53:30.309
I I I just uh I just and because we've


00:53:30.319 --> 00:53:32.630
we've been able to send so many probes


00:53:32.640 --> 00:53:36.309
and and rovers and satellites to Mars,


00:53:36.319 --> 00:53:39.270
we've been able to document it, get some


00:53:39.280 --> 00:53:42.710
incredible high res pictures of it. It's


00:53:42.720 --> 00:53:44.790
I I just find it a a beautiful,


00:53:44.800 --> 00:53:47.109
beautiful world. And I mentioned my


00:53:47.119 --> 00:53:51.270
sci-fi trilogy um earlier. Um Mars is in


00:53:51.280 --> 00:53:54.150
it. I couldn't I couldn't leave it out.


00:53:54.160 --> 00:53:56.950
So Mars for me, that was a quick answer.


00:53:56.960 --> 00:53:58.390
What's yours? It's got to be in the


00:53:58.400 --> 00:54:01.109
solar system. It's a really tough one.


00:54:01.119 --> 00:54:03.750
And these kind of questions throw throw


00:54:03.760 --> 00:54:05.910
me because the it might be a childish


00:54:05.920 --> 00:54:06.870
question because it's the kind of


00:54:06.880 --> 00:54:09.349
questions kids ask, but it's entirely a


00:54:09.359 --> 00:54:11.190
good question to ask.


00:54:11.200 --> 00:54:12.870
>> I'm not as broken by this. While I was


00:54:12.880 --> 00:54:15.270
over in Switzerland, um met up with an


00:54:15.280 --> 00:54:17.990
ex of mine whose daughter's now 9 or 10


00:54:18.000 --> 00:54:20.309
years old and her daughter's doing


00:54:20.319 --> 00:54:23.430
English at school and all well and good


00:54:23.440 --> 00:54:25.910
and she wanted to practice her English


00:54:25.920 --> 00:54:27.270
and was talking to us a bit in English


00:54:27.280 --> 00:54:28.870
and kids ask you what's your favorite


00:54:28.880 --> 00:54:30.069
color, things like that. She asked me


00:54:30.079 --> 00:54:32.549
what my favorite fruit was and I was


00:54:32.559 --> 00:54:33.990
just broken cuz I've never really


00:54:34.000 --> 00:54:36.309
thought of that and it took me like two


00:54:36.319 --> 00:54:37.829
or three minutes to kind of it just put


00:54:37.839 --> 00:54:40.710
me into this head jam and I didn't know


00:54:40.720 --> 00:54:42.790
an answer. This one's a little bit like


00:54:42.800 --> 00:54:45.510
this. And to me, this question is a bit


00:54:45.520 --> 00:54:47.589
like asking somebody with a large family


00:54:47.599 --> 00:54:49.349
who their favorite child is or asking


00:54:49.359 --> 00:54:50.630
someone who their favorite pet is. Now,


00:54:50.640 --> 00:54:53.589
I suspect I don't have kids, but I think


00:54:53.599 --> 00:54:55.270
the favorite kid varies from time to


00:54:55.280 --> 00:54:56.470
time with people who've got parents and


00:54:56.480 --> 00:54:57.910
they'd never say they have a favorite,


00:54:57.920 --> 00:55:00.390
but there's a little ranking scale. It's


00:55:00.400 --> 00:55:01.990
nanny and her extended family in the


00:55:02.000 --> 00:55:03.430
discorld series where you could tell how


00:55:03.440 --> 00:55:04.870
in favor people were where where the


00:55:04.880 --> 00:55:06.710
trinkets that they bought her were in


00:55:06.720 --> 00:55:08.309
the house. and you know, heaven for fend


00:55:08.319 --> 00:55:09.430
that the little thing you brought back


00:55:09.440 --> 00:55:10.710
from holiday ended up on the coffee


00:55:10.720 --> 00:55:12.549
table outside in the hallway cuz that


00:55:12.559 --> 00:55:14.790
meant you were really in the bad books.


00:55:14.800 --> 00:55:17.270
I really struggle to answer questions


00:55:17.280 --> 00:55:19.349
like this because they're all


00:55:19.359 --> 00:55:21.910
fascinating in different ways. You know,


00:55:21.920 --> 00:55:23.510
there are things that we can really get


00:55:23.520 --> 00:55:25.750
from them. Mars from an astrobiology


00:55:25.760 --> 00:55:27.109
point of view is really the obvious


00:55:27.119 --> 00:55:28.710
answer because it's the place that we'll


00:55:28.720 --> 00:55:31.349
look for life elsewhere. Jupiter is the


00:55:31.359 --> 00:55:32.630
obvious answer because it's been


00:55:32.640 --> 00:55:34.150
fundamental to a lot of the research


00:55:34.160 --> 00:55:35.829
I've done in terms of the question of


00:55:35.839 --> 00:55:38.230
Jupiter friend or foe. It throws a lot


00:55:38.240 --> 00:55:40.390
of comments our way. It's the source of


00:55:40.400 --> 00:55:42.790
therefore indirectly the cause of many


00:55:42.800 --> 00:55:43.990
of the meteor showers and many of the


00:55:44.000 --> 00:55:46.950
meteor storms and stuff we see. I they


00:55:46.960 --> 00:55:49.270
they would be contenders as would the


00:55:49.280 --> 00:55:51.430
others to a certain degree. Neptune


00:55:51.440 --> 00:55:54.309
because it's a fabulous insight into how


00:55:54.319 --> 00:55:56.549
science can change over time and how we


00:55:56.559 --> 00:55:58.710
can discover things without seeing them.


00:55:58.720 --> 00:56:01.510
Neptune kind of preaged the exoplanet


00:56:01.520 --> 00:56:04.230
era because we discovered Neptune not by


00:56:04.240 --> 00:56:06.150
seeing Neptune but by observing Uranus


00:56:06.160 --> 00:56:08.230
misbehaving and inferring that Neptune


00:56:08.240 --> 00:56:10.069
had to be there to cause that


00:56:10.079 --> 00:56:11.190
misbehavior.


00:56:11.200 --> 00:56:12.870
>> Although there are some suggestions that


00:56:12.880 --> 00:56:16.150
Galileo actually saw Neptune in 1610 and


00:56:16.160 --> 00:56:17.990
should be credited as the discoverer but


00:56:18.000 --> 00:56:20.150
didn't realize what he had. There's a


00:56:20.160 --> 00:56:22.950
background star marked on one of his


00:56:22.960 --> 00:56:24.950
drawings I think of the Galilean moons,


00:56:24.960 --> 00:56:27.349
the moons of Jupiter where there is no


00:56:27.359 --> 00:56:28.710
star and people think it was actually


00:56:28.720 --> 00:56:29.589
Neptune.


00:56:29.599 --> 00:56:31.270
>> So there are some suggestions Galileo


00:56:31.280 --> 00:56:32.390
was a discover of Neptune.


00:56:32.400 --> 00:56:33.270
>> Interesting.


00:56:33.280 --> 00:56:34.789
>> But for me, Neptune's fascinating


00:56:34.799 --> 00:56:36.470
because of that indirect discovery. But


00:56:36.480 --> 00:56:38.950
I think for me, if you really push it, I


00:56:38.960 --> 00:56:40.630
probably have to say the Earth


00:56:40.640 --> 00:56:44.069
>> and a it's the Earth because we is here.


00:56:44.079 --> 00:56:45.589
>> But the Earth is a place that's driven


00:56:45.599 --> 00:56:47.349
all that complexity in terms of life.


00:56:47.359 --> 00:56:48.950
And if you think about Mars being a


00:56:48.960 --> 00:56:51.829
complex place, the Earth is even more so


00:56:51.839 --> 00:56:53.190
because of the influence of the water


00:56:53.200 --> 00:56:54.470
and the atmosphere, the weathering and


00:56:54.480 --> 00:56:57.109
the plate tectonics, you know. So, it's


00:56:57.119 --> 00:56:58.470
my favorite from the point of view of


00:56:58.480 --> 00:57:00.069
it's the only place I can sit around


00:57:00.079 --> 00:57:01.510
comfortably in shorts and t-shirt and


00:57:01.520 --> 00:57:05.510
chat like this. Also, because it is the


00:57:05.520 --> 00:57:08.069
window into the future of our knowledge


00:57:08.079 --> 00:57:10.710
of life elsewhere, and it's the cradle


00:57:10.720 --> 00:57:11.829
of everything we know and everything


00:57:11.839 --> 00:57:14.789
we've experienced. I do have a deep and


00:57:14.799 --> 00:57:16.230
abiding love of the earth from that


00:57:16.240 --> 00:57:17.990
point of view. But also as a scientist,


00:57:18.000 --> 00:57:20.870
the earth is fascinatingly complex


00:57:20.880 --> 00:57:23.430
compared to the other planets. It's the


00:57:23.440 --> 00:57:26.390
only planet on which we observe plate


00:57:26.400 --> 00:57:27.430
tectonics.


00:57:27.440 --> 00:57:28.390
>> Yeah.


00:57:28.400 --> 00:57:30.069
>> Therefore, it's the only planet whose


00:57:30.079 --> 00:57:32.549
surface on longtime scales is that


00:57:32.559 --> 00:57:34.549
degree of changeable and mutable. You


00:57:34.559 --> 00:57:38.069
know, if I brought you back, say we did


00:57:38.079 --> 00:57:39.990
um play with Ren's question from the


00:57:40.000 --> 00:57:41.750
start a bit more. We built the


00:57:41.760 --> 00:57:43.270
spacecraft from tow zero. We


00:57:43.280 --> 00:57:46.230
accelerated. Had a problem. Couldn't


00:57:46.240 --> 00:57:48.390
slow down. Eventually managed to fix it.


00:57:48.400 --> 00:57:49.750
Came back and we came back in a billion


00:57:49.760 --> 00:57:51.990
years time. Mars would still look like


00:57:52.000 --> 00:57:54.230
it does today. Unless humanity


00:57:54.240 --> 00:57:56.549
terraforms Mars. Mars would look like it


00:57:56.559 --> 00:57:58.069
does today. Venus would look like it


00:57:58.079 --> 00:57:59.510
does today. All of the planets would


00:57:59.520 --> 00:58:01.750
look like they do today. Saturn's rings


00:58:01.760 --> 00:58:03.030
may have gone. Peripheral things like


00:58:03.040 --> 00:58:04.230
that will have gone, but the Earth would


00:58:04.240 --> 00:58:05.990
be unrecognizable.


00:58:06.000 --> 00:58:07.910
>> With continental drift, the Earth


00:58:07.920 --> 00:58:09.990
wouldn't look like home. And even with


00:58:10.000 --> 00:58:11.349
the change in the atmosphere, the earth


00:58:11.359 --> 00:58:13.190
may have changed. I've seen some


00:58:13.200 --> 00:58:14.630
suggestions that when the earth was


00:58:14.640 --> 00:58:16.710
young, the oceans weren't blue, they


00:58:16.720 --> 00:58:17.270
were green.


00:58:17.280 --> 00:58:17.990
>> Yeah, I've heard that.


00:58:18.000 --> 00:58:20.069
>> That's how much the earth has changed.


00:58:20.079 --> 00:58:21.670
The mountain ranges will have shifted. I


00:58:21.680 --> 00:58:23.829
always find it fascinating to wonder


00:58:23.839 --> 00:58:25.589
what is the biggest mountain that the


00:58:25.599 --> 00:58:27.510
Earth has ever had. And you Google that,


00:58:27.520 --> 00:58:29.829
that's been asked a lot. Nobody's really


00:58:29.839 --> 00:58:32.870
got a strong answer because a lot of it


00:58:32.880 --> 00:58:34.630
depends on the elasticity of the Earth's


00:58:34.640 --> 00:58:36.150
interior and the energy available for


00:58:36.160 --> 00:58:38.230
plate tectonics because a limiting


00:58:38.240 --> 00:58:39.750
factor on the height of a mountain on


00:58:39.760 --> 00:58:42.549
Earth is the sinking that you get as a


00:58:42.559 --> 00:58:44.230
result of the mass of the mountain and


00:58:44.240 --> 00:58:45.910
the weathering that we get that wears it


00:58:45.920 --> 00:58:47.829
away. On Mars, you don't have that with


00:58:47.839 --> 00:58:50.230
Olympus Mons. There's no weathering.


00:58:50.240 --> 00:58:51.829
>> So, it could just get bigger and bigger


00:58:51.839 --> 00:58:53.270
even though it will have a very deep


00:58:53.280 --> 00:58:55.270
route. It could keep getting bigger


00:58:55.280 --> 00:58:56.390
because there was nothing wearing it


00:58:56.400 --> 00:58:59.109
down again. So I think for me because of


00:58:59.119 --> 00:59:01.750
the complexity and because it gives me a


00:59:01.760 --> 00:59:03.670
place to do my astrophotography and live


00:59:03.680 --> 00:59:06.069
my life and all the rest of it, the


00:59:06.079 --> 00:59:07.270
earth would have to be the top of the


00:59:07.280 --> 00:59:09.030
list. But trying to pick a planet other


00:59:09.040 --> 00:59:11.349
than the earth is a bit like trying to


00:59:11.359 --> 00:59:13.270
fi pick your favorite pet or your


00:59:13.280 --> 00:59:14.710
favorite child. And it might be that you


00:59:14.720 --> 00:59:16.150
have one internally, but heaven offend


00:59:16.160 --> 00:59:18.950
you tell them.


00:59:18.960 --> 00:59:20.710
Very good answer. Very good answer. I


00:59:20.720 --> 00:59:22.870
love the question. So uh not childish at


00:59:22.880 --> 00:59:25.030
all and appreciate you sending it in.


00:59:25.040 --> 00:59:26.710
And if you'd like to send questions into


00:59:26.720 --> 00:59:29.030
us at Spacenuts, jump on our website,


00:59:29.040 --> 00:59:31.510
spacenuts.io


00:59:31.520 --> 00:59:34.069
or spacenutspodcast.com


00:59:34.079 --> 00:59:36.069
and click on the ask me anything button


00:59:36.079 --> 00:59:38.390
at the top. It's just labeled AMA. And


00:59:38.400 --> 00:59:39.670
while you're there, have a look around,


00:59:39.680 --> 00:59:41.109
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00:59:41.119 --> 00:59:43.510
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00:59:48.720 --> 00:59:50.309
And that'll wrap us up for another


00:59:50.319 --> 00:59:52.549
episode. Jonty, thank you so much.


00:59:52.559 --> 00:59:53.670
>> That's a pleasure. Thank you for having


00:59:53.680 --> 00:59:55.349
me. Always a pleasure. Uh, Professor


00:59:55.359 --> 00:59:58.150
Jonty her prof professor of astrophysics


00:59:58.160 --> 00:59:59.589
at the University of Southern


00:59:59.599 --> 01:00:02.630
Queensland. Hey, and uh, Hugh in the


01:00:02.640 --> 01:00:04.710
studio um, couldn't be with us today. He


01:00:04.720 --> 01:00:06.950
realized that Earth wasn't his favorite


01:00:06.960 --> 01:00:09.430
planet, so he left. And from me, Andrew


01:00:09.440 --> 01:00:11.030
Dunley, thanks for your company. Catch


01:00:11.040 --> 01:00:13.430
you on the next episode of Space Nuts.


01:00:13.440 --> 01:00:14.549
Bye-bye.


01:00:14.559 --> 01:00:16.870
>> Space Nuts. You'll be listening to the


01:00:16.880 --> 01:00:19.829
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01:00:19.839 --> 01:00:22.870
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