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Time Travel, Saturn's Rings, and Favourite Planets In this engaging Q&A edition of Space Nuts , hosts Andrew Dunkley and Professor Jonti Horner dive into a series of thought-provoking questions from listeners. From the complexities of moving through time to the intriguing origins of Saturn's rings, this episode is packed with cosmic insights.
Episode Highlights:
- Understanding Time Travel: Rennie from California poses a fascinating question about the nature of time and whether one's lifespan could differ based on their movement through time. Jonty unpacks the concept of time as a dimension, exploring relativity and time dilation.
- The Mystery of Saturn's Rings: Paul from Brisbane asks about the potential for debris from a collision between Saturn’s moons to have impacted Earth 65 million years ago. The discussion delves into the origins of Saturn's rings and the dynamics of celestial collisions.
- Favourite Planets: Dan from the Gold Coast wonders about the hosts' favourite planets in the solar system. Andrew shares his admiration for Mars and its geological wonders, while Jonty contemplates the complexity of Earth and the awe of Jupiter.
For more Space Nuts, including our continuously updating newsfeed and to listen to all our episodes, visit our website. (https://www.spacenutspodcast.com/) Follow us on social media at SpaceNutsPod on Facebook, Instagram, and more. We love engaging with our community, so be sure to drop us a message or comment on your favourite platform.
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Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.
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- Introduction to Time Travel
- The Nature of Time and Relativity
- Saturn's Rings and Cosmic Collisions
- The Search for Debris and Impacts
- Favourite Planets: Mars vs. Earth vs. Jupiter
Episode link: https://play.headliner.app/episode/33440594?utm_source=youtube
00:00:00 --> 00:00:01 Hi there. Thanks again for joining us.
00:00:01 --> 00:00:04 This is a Q&A edition of Space Nuts,
00:00:04 --> 00:00:06 where we talk astronomy and space
00:00:06 --> 00:00:09 science. And in a Q&A edition, uh UQ and
00:00:09 --> 00:00:12 we a uh which means we'll answer
00:00:12 --> 00:00:14 audience questions. Uh today we're going
00:00:14 --> 00:00:17 to talk about uh moving through time.
00:00:17 --> 00:00:20 What does that mean? Uh also some stuff
00:00:20 --> 00:00:23 from Saturn's rings and a sort of
00:00:23 --> 00:00:25 hypothetical, not a hypothetical, but a
00:00:25 --> 00:00:27 you know, not even a what if question.
00:00:27 --> 00:00:30 And it's just a question asking our
00:00:30 --> 00:00:32 favorite planets and why. Well, you
00:00:32 --> 00:00:35 know, um that's Jonty's thing. So, we
00:00:35 --> 00:00:37 will talk about all of that on this
00:00:37 --> 00:00:38 episode of Space Nuts.
00:00:38 --> 00:00:43 >> 15 seconds. Guidance is internal. 10 9
00:00:43 --> 00:00:45 Ignition sequence start.
00:00:45 --> 00:00:46 >> Space Nuts.
00:00:46 --> 00:00:51 >> 5 4 3 2 1 2 3 4 5 5 4 3 2 1
00:00:51 --> 00:00:52 >> Space Nuts.
00:00:52 --> 00:00:55 >> Astronauts report. It feels good. And
00:00:55 --> 00:00:59 while Fred's away, Jonty is here to play
00:00:59 --> 00:01:01 and answer your questions. He is
00:01:01 --> 00:01:03 Professor Jotty her, professor of
00:01:03 --> 00:01:05 astrophysics at the University of
00:01:05 --> 00:01:07 Southern Queensland. Hello, Johnny.
00:01:07 --> 00:01:08 >> Hey, how are you going?
00:01:08 --> 00:01:11 >> I am very well. Good to see you again.
00:01:11 --> 00:01:12 >> Well, it's good. Yeah. Now, I've got
00:01:12 --> 00:01:14 interesting questions today.
00:01:14 --> 00:01:16 >> Yeah, we've got some beauties. Um, we
00:01:16 --> 00:01:18 might get straight into it. Our first
00:01:18 --> 00:01:21 question comes from Renie uh in Sunny
00:01:21 --> 00:01:22 West Hills, California. Hi, Renie. Renie
00:01:22 --> 00:01:25 is a a regular contributor, so u we hear
00:01:25 --> 00:01:27 from Renie semi-regularly.
00:01:27 --> 00:01:30 Uh can you please explain what it means
00:01:30 --> 00:01:33 to be moving through time? If I
00:01:33 --> 00:01:35 theoretically could sit in a chair from
00:01:36 --> 00:01:38 birth to death, will I die on a faster
00:01:38 --> 00:01:41 timeline than someone who lived a
00:01:41 --> 00:01:45 regular normal life? uh is what's aging
00:01:45 --> 00:01:47 me about the movement of the earth
00:01:47 --> 00:01:49 around the sun combined with the sun
00:01:49 --> 00:01:50 moving around the galaxy combined with
00:01:50 --> 00:01:52 the galaxies moving around each other
00:01:52 --> 00:01:56 and my own physical movement
00:01:56 --> 00:01:58 really that that's kind of a what if
00:01:58 --> 00:02:00 question we love what if questions uh
00:02:00 --> 00:02:02 thanks Renie um let's open that one up
00:02:02 --> 00:02:06 to a little bit of um investigation
00:02:06 --> 00:02:08 >> absolutely and I think the first thing
00:02:08 --> 00:02:09 I'd say here is this is such a fun
00:02:09 --> 00:02:12 question it may be well give it a couple
00:02:12 --> 00:02:14 of months and ask it again and see
00:02:14 --> 00:02:16 whether Fred gives a similar answer to
00:02:16 --> 00:02:17 me or not.
00:02:17 --> 00:02:21 >> Um, it it's a really interesting one.
00:02:21 --> 00:02:25 So, the idea of time being a dimension
00:02:25 --> 00:02:27 is something that I think makes all of
00:02:27 --> 00:02:28 our heads hurt a little bit when we
00:02:28 --> 00:02:30 first encounter it and for most of us
00:02:30 --> 00:02:33 continues to do so forever more. It's
00:02:33 --> 00:02:36 one of the fundamentals of the idea of
00:02:36 --> 00:02:37 what I guess is often described as
00:02:37 --> 00:02:41 space-time physics comes out of the work
00:02:41 --> 00:02:43 that people like Albert Einstein did
00:02:43 --> 00:02:46 with relativity.
00:02:46 --> 00:02:49 We're used to the three physical three
00:02:49 --> 00:02:51 spatial dimensions
00:02:51 --> 00:02:53 up, down, left, right, and forward and
00:02:53 --> 00:02:56 back. Although I I'm realizing more and
00:02:56 --> 00:02:59 more that we actually live in a two two
00:02:59 --> 00:03:01 plus one kind of existence really
00:03:01 --> 00:03:04 because we don't look up very often.
00:03:04 --> 00:03:05 Part of our common sense is about
00:03:05 --> 00:03:06 two-dimensional movement, not
00:03:06 --> 00:03:08 threedimensional cuz we think about
00:03:08 --> 00:03:09 moving around on the surface of the
00:03:09 --> 00:03:12 earth and there's all sorts of weird and
00:03:12 --> 00:03:14 fundamental things with that. Now, the
00:03:14 --> 00:03:17 idea that time is also a dimension is
00:03:17 --> 00:03:19 part of that whole thing of space-time
00:03:19 --> 00:03:22 physics built into the relativity twins,
00:03:22 --> 00:03:24 you know, special in general. And it's a
00:03:24 --> 00:03:26 very weird one because with the other
00:03:26 --> 00:03:27 dimensions,
00:03:27 --> 00:03:30 we choose where to move or we're carried
00:03:30 --> 00:03:32 along where we're aware of motion.
00:03:32 --> 00:03:33 Motion in a way that is changing
00:03:34 --> 00:03:36 direction. We can change speed. We feel
00:03:36 --> 00:03:39 agency. But with time, when you get told
00:03:39 --> 00:03:41 that time is a dimension, you think,
00:03:41 --> 00:03:43 "But I can't move. I can't choose my
00:03:43 --> 00:03:46 motion in it. We're all carried through
00:03:46 --> 00:03:50 time at 1 second per second. And so it's
00:03:50 --> 00:03:52 like a dimension without agency. It's
00:03:52 --> 00:03:54 all a little bit weird.
00:03:54 --> 00:03:58 >> Now, it does lead to that concept of
00:03:58 --> 00:03:59 time as a dimension is one of the things
00:03:59 --> 00:04:01 that's part of the underpinninging of
00:04:01 --> 00:04:03 all this stuff like with special and
00:04:03 --> 00:04:05 general relativity, things like time
00:04:05 --> 00:04:09 dilation, stuff like this. It's also
00:04:09 --> 00:04:11 tied into
00:04:11 --> 00:04:14 um events and consequences, the logical
00:04:14 --> 00:04:16 order of things. You know, a cause has
00:04:16 --> 00:04:18 to cause an effect. You don't get the
00:04:18 --> 00:04:20 effect before the cause. Things like
00:04:20 --> 00:04:22 this. Now,
00:04:22 --> 00:04:24 this rapidly gets very complicated. And
00:04:24 --> 00:04:26 I know at university when you study
00:04:26 --> 00:04:28 physics as a partner to astronomy or you
00:04:28 --> 00:04:31 study um relative relativity as part of
00:04:31 --> 00:04:33 an astronomy thing, I know a lot of
00:04:33 --> 00:04:36 people find it hugely challenging to get
00:04:36 --> 00:04:38 their head around it. And I will openly
00:04:38 --> 00:04:40 admit that when I did my relativity
00:04:40 --> 00:04:42 courses as an undergrad, my head hurt.
00:04:42 --> 00:04:43 It was really, really hard. And
00:04:44 --> 00:04:45 particularly in first year, special
00:04:45 --> 00:04:48 relativity didn't work for me. And it's
00:04:48 --> 00:04:50 something I always say to my students,
00:04:50 --> 00:04:51 something I'm very aware of, and
00:04:51 --> 00:04:53 something I'd say to listeners is that
00:04:53 --> 00:04:55 no one explanation will work for
00:04:55 --> 00:04:57 everybody. We all learn in different
00:04:58 --> 00:04:59 ways, and one source that is brilliant
00:04:59 --> 00:05:01 for me might not be brilliant for you.
00:05:01 --> 00:05:03 So if my explanation doesn't work,
00:05:03 --> 00:05:04 please go out and seek another one.
00:05:04 --> 00:05:06 That's no slight on me. It just means
00:05:06 --> 00:05:07 that your way of learning and my way of
00:05:07 --> 00:05:09 explaining didn't match in that case and
00:05:09 --> 00:05:12 another explanation is needed. And when
00:05:12 --> 00:05:14 it came to relativity, I was very much
00:05:14 --> 00:05:16 in that boat. I was sat in these
00:05:16 --> 00:05:18 lectures and this is old style education
00:05:18 --> 00:05:21 30 years ago and it actually is 29 and a
00:05:21 --> 00:05:22 half years ago that I was in these
00:05:22 --> 00:05:25 lectures cuz it was late 1996. Sat there
00:05:25 --> 00:05:28 taking notes on paper while somebody's
00:05:28 --> 00:05:29 talking at you and writing on a board.
00:05:29 --> 00:05:30 So a lot of the information was going
00:05:30 --> 00:05:32 through from my eyes to the page without
00:05:32 --> 00:05:34 going through my brain. I suspect, you
00:05:34 --> 00:05:36 know, that autonomous writing thing,
00:05:36 --> 00:05:38 >> but it just wasn't jelling for me. The
00:05:38 --> 00:05:41 whole the equations are written down so
00:05:41 --> 00:05:43 you can use them, but it wasn't making
00:05:43 --> 00:05:45 sense. And the course textbook we had
00:05:45 --> 00:05:49 was incredibly mathematical because
00:05:49 --> 00:05:51 the person who wrote the textbook
00:05:51 --> 00:05:52 understood it through the maths, so they
00:05:52 --> 00:05:53 explained it through the maths. And
00:05:53 --> 00:05:56 that's not the way that I learn. Some
00:05:56 --> 00:05:58 people learn brilliantly from maths. I
00:05:58 --> 00:06:00 don't. I'm much more of a visual form or
00:06:00 --> 00:06:02 a picture form or metaphor type thinker
00:06:02 --> 00:06:04 than an equation is a be all and end
00:06:04 --> 00:06:07 all. So about the only textbook I ever
00:06:07 --> 00:06:09 used in my undergrad days, I was
00:06:09 --> 00:06:11 terrible. I'd buy the textbooks, not
00:06:11 --> 00:06:12 open them, and then I'd sell them on at
00:06:12 --> 00:06:14 the end of the trimester, end of the
00:06:14 --> 00:06:15 term for someone else to take off me and
00:06:15 --> 00:06:17 probably do the same thing.
00:06:17 --> 00:06:19 >> But I found a textbook in the library
00:06:19 --> 00:06:21 that worked for me and ended up buying
00:06:21 --> 00:06:22 it. And I was going to recommend it
00:06:22 --> 00:06:25 because it was so foundation in helping
00:06:25 --> 00:06:27 me to overcome something I couldn't
00:06:28 --> 00:06:29 understand that I always think when
00:06:29 --> 00:06:30 people are struggling with the
00:06:30 --> 00:06:32 relativity stuff. Worth recommending it.
00:06:32 --> 00:06:34 It's a big book called Spacetime Physics
00:06:34 --> 00:06:37 by Edwin F. Taylor and John Archie Bald
00:06:37 --> 00:06:39 Wheeler. And to my shock, I looked it up
00:06:39 --> 00:06:41 just before this podcast and the first
00:06:41 --> 00:06:44 edition was published in 1965.
00:06:44 --> 00:06:47 So the first edition was born was
00:06:47 --> 00:06:50 launched closer to the publishing of the
00:06:50 --> 00:06:52 theory of general relativity and the
00:06:52 --> 00:06:54 theory of special relativity than my
00:06:54 --> 00:06:55 reading it
00:06:55 --> 00:06:58 >> or certainly than we are today should I
00:06:58 --> 00:07:00 say absolutely than we are today. Um it
00:07:00 --> 00:07:02 is still in print and what worked for me
00:07:02 --> 00:07:04 was that it didn't go straight to the
00:07:04 --> 00:07:06 maths instead it used drawings and
00:07:06 --> 00:07:09 figures and thought experiments and I
00:07:09 --> 00:07:10 read it voraciously. It was very
00:07:10 --> 00:07:12 readable. I remember it from 30 years
00:07:12 --> 00:07:13 ago and it had an impact. I'd really
00:07:13 --> 00:07:14 recommend that if you're struggling with
00:07:14 --> 00:07:17 the relativity stuff, um, go to your
00:07:17 --> 00:07:19 local library. The textbooks are
00:07:19 --> 00:07:22 punishingly expensive and um, therefore
00:07:22 --> 00:07:23 I'd always recommend people get them
00:07:23 --> 00:07:25 from library first and make absolutely
00:07:25 --> 00:07:27 sure. But if you're at all interested in
00:07:28 --> 00:07:31 those foundations of how relativity and
00:07:31 --> 00:07:33 everything works, I found that book
00:07:33 --> 00:07:35 astonishing. Okay,
00:07:35 --> 00:07:36 >> that's all getting a bit off the topic
00:07:36 --> 00:07:38 though. But that explains a lot better
00:07:38 --> 00:07:40 than I could do the concepts behind
00:07:40 --> 00:07:43 relativity that include time as a
00:07:43 --> 00:07:46 dimension. Includes space-time diagrams,
00:07:46 --> 00:07:48 which are these weird cone- shaped
00:07:48 --> 00:07:50 figures where if you're traveling at the
00:07:50 --> 00:07:53 speed of light, you move the same
00:07:53 --> 00:07:55 distance in X, which is distance as you
00:07:55 --> 00:07:57 do in time Y. So you get a cone opened
00:07:57 --> 00:07:59 out like this and everything inside that
00:07:59 --> 00:08:01 cone is moving slower than the speed of
00:08:01 --> 00:08:03 light because it's going up the y- axis
00:08:03 --> 00:08:05 quicker than it goes on the x- axis.
00:08:05 --> 00:08:08 Anything that is nearer to the x-axis of
00:08:08 --> 00:08:10 that line is further away from the
00:08:10 --> 00:08:13 observer than they could observe it yet.
00:08:13 --> 00:08:14 So any light that left that would not
00:08:14 --> 00:08:17 have reached you yet. Now hard to
00:08:17 --> 00:08:19 visualize but if you look into the book
00:08:19 --> 00:08:22 that is what it means. Now moving in
00:08:22 --> 00:08:25 time is talking about our motion on the
00:08:26 --> 00:08:28 y-axis of that graph where we move up it
00:08:28 --> 00:08:30 by 1 second every second.
00:08:30 --> 00:08:31 >> Y
00:08:31 --> 00:08:34 >> that is something over which we do not
00:08:34 --> 00:08:37 really have control. Um I I suspect some
00:08:37 --> 00:08:39 people would argue that certain
00:08:39 --> 00:08:40 substances that can be ingested change
00:08:40 --> 00:08:42 your perception of how time loads. So
00:08:42 --> 00:08:43 you might be able to control the speed
00:08:43 --> 00:08:46 you fly through it there. But that's
00:08:46 --> 00:08:48 what we mean by moving in time. It's
00:08:48 --> 00:08:52 perceiving time moving forward so that
00:08:52 --> 00:08:54 from one second to the next change
00:08:54 --> 00:08:57 happens. You know, yesterday is a time
00:08:57 --> 00:08:59 in the past that's already happened.
00:08:59 --> 00:09:00 That's a cause. You'll see the effects
00:09:00 --> 00:09:02 today. Tomorrow hasn't happened yet. You
00:09:02 --> 00:09:05 can't see what is there tomorrow.
00:09:05 --> 00:09:07 >> That's what it means by moving in time.
00:09:07 --> 00:09:09 And it there's all sorts of wonderful
00:09:09 --> 00:09:11 ways people have described it or played
00:09:11 --> 00:09:13 with this. again. You know, I often come
00:09:13 --> 00:09:15 back to the Terry Pratt stuff and I was
00:09:15 --> 00:09:16 just looking at a thread the other day
00:09:16 --> 00:09:17 of people talking about their favorite
00:09:17 --> 00:09:19 Terry Pratt quotes. I'll just try and
00:09:19 --> 00:09:23 pull this one up. Um, it's from when the
00:09:23 --> 00:09:26 eternally surprised, uh, who was the
00:09:26 --> 00:09:29 founder of the history monks. Um,
00:09:29 --> 00:09:30 basically talking about his perception
00:09:30 --> 00:09:32 of time. So, you know, man looks a
00:09:32 --> 00:09:33 keyboard cuz I didn't think of doing
00:09:33 --> 00:09:37 this, but yeah, this is from Thief of
00:09:37 --> 00:09:40 Time, I think it was. Yes. um talking
00:09:40 --> 00:09:42 about how when viewed the universe and
00:09:42 --> 00:09:45 viewed moving through time as this
00:09:45 --> 00:09:48 ancient philosopher who set up the monks
00:09:48 --> 00:09:50 of history who are the people who run
00:09:50 --> 00:09:52 around unseen in the background fixing
00:09:52 --> 00:09:53 things when they go wrong because in the
00:09:53 --> 00:09:55 disc world they go wrong all the time.
00:09:55 --> 00:09:55 Yeah.
00:09:55 --> 00:09:57 >> But says when considered the nature of
00:09:57 --> 00:09:59 time
00:09:59 --> 00:10:00 >> and understood that the universe is
00:10:00 --> 00:10:03 instant by instant recreated a new.
00:10:03 --> 00:10:05 Therefore he understood there is in
00:10:05 --> 00:10:08 truth no past only a memory of the past.
00:10:08 --> 00:10:09 Blink your eyes and the world you see
00:10:09 --> 00:10:12 next did not exist when you closed them.
00:10:12 --> 00:10:13 Therefore, he said, the only appropriate
00:10:13 --> 00:10:16 state of the mind is surprise. The only
00:10:16 --> 00:10:19 appropriate state of the heart is joy.
00:10:19 --> 00:10:21 The sky you see now, you have never seen
00:10:21 --> 00:10:23 before. The perfect moment is now. Be
00:10:23 --> 00:10:25 glad of it.
00:10:25 --> 00:10:25 >> That's good.
00:10:25 --> 00:10:27 >> I talk about patchet a lot, but I always
00:10:27 --> 00:10:29 think that's really beautiful and it
00:10:29 --> 00:10:32 fits in with this concept of time moving
00:10:32 --> 00:10:34 irrevocably forward. You can never
00:10:34 --> 00:10:36 return to the past and change things.
00:10:36 --> 00:10:39 What you can change is the future. When
00:10:39 --> 00:10:41 you wake up every morning, it's as
00:10:41 --> 00:10:43 though you're newborn into the universe
00:10:43 --> 00:10:46 effectively because who is to say that
00:10:46 --> 00:10:48 you ever lived before? You know, it may
00:10:48 --> 00:10:50 well be that all of your memories were
00:10:50 --> 00:10:52 just implanted in you when you woke up
00:10:52 --> 00:10:53 this very instant. We don't know.
00:10:53 --> 00:10:55 Obviously,
00:10:55 --> 00:10:57 >> the Okam's razor argument is yes, you
00:10:57 --> 00:10:59 existed yesterday and we did do the
00:10:59 --> 00:11:01 record the other day. But it's
00:11:01 --> 00:11:02 interesting to think of that and it's
00:11:02 --> 00:11:06 the way that people perceive time. Now
00:11:06 --> 00:11:08 moving on to the motion side of it,
00:11:08 --> 00:11:10 Renie. Um the idea of sitting in a chair
00:11:10 --> 00:11:12 from birth to death and how that would
00:11:12 --> 00:11:15 affect your life. I'm not a medic, but I
00:11:15 --> 00:11:16 suspect if you ask your doctor that
00:11:16 --> 00:11:18 question, they will probably tell you
00:11:18 --> 00:11:21 that indeed if you sat in a chair from
00:11:21 --> 00:11:22 birth to death, your life would be
00:11:22 --> 00:11:23 shorter than if you lived a normal life
00:11:23 --> 00:11:26 as a person because of health reasons. I
00:11:26 --> 00:11:27 mean if nothing else if there's no one
00:11:27 --> 00:11:29 around to feed you it might lead to a
00:11:29 --> 00:11:32 relatively short existence. So there is
00:11:32 --> 00:11:35 that aspect of it as well. We can't see
00:11:35 --> 00:11:37 the future. So we can't predict what our
00:11:37 --> 00:11:38 choices are going to do in terms of
00:11:38 --> 00:11:40 lengthening or shortening our lives. But
00:11:40 --> 00:11:42 there is one way in which your motion
00:11:42 --> 00:11:45 can lead to you having a slightly
00:11:45 --> 00:11:48 different timeline. So from the point of
00:11:48 --> 00:11:49 view of your life or the number of beats
00:11:49 --> 00:11:51 of your heart or your perceived time,
00:11:51 --> 00:11:53 you live the time that you live.
00:11:53 --> 00:11:56 >> Yeah. The faster you're moving though,
00:11:56 --> 00:11:58 and this is an outcome of general
00:11:58 --> 00:12:02 relativity, motion causes time dilation,
00:12:02 --> 00:12:04 particularly motion with acceleration.
00:12:04 --> 00:12:06 You know, there's loads and loads of
00:12:06 --> 00:12:08 complexity to this.
00:12:08 --> 00:12:11 If you were moving faster,
00:12:11 --> 00:12:14 the time you perceive is very slightly
00:12:14 --> 00:12:16 slower. Now, you then get into rest
00:12:16 --> 00:12:18 frames and all that stuff makes my head
00:12:18 --> 00:12:20 hurt. So the only place this actually
00:12:20 --> 00:12:23 really becomes relevant particularly in
00:12:23 --> 00:12:25 our day-to-day lives in our lived
00:12:25 --> 00:12:27 experience is when you've got a moving
00:12:27 --> 00:12:28 platform that's changing direction. So
00:12:28 --> 00:12:31 it's undergoing acceleration.
00:12:31 --> 00:12:33 Think about satellites circling the
00:12:33 --> 00:12:36 earth. They are circling the earth. They
00:12:36 --> 00:12:38 are moving at a faster speed than we are
00:12:38 --> 00:12:41 here on the surface of the earth.
00:12:41 --> 00:12:43 >> We however slightly nearer the center of
00:12:43 --> 00:12:44 the earth. So we get a little bit of
00:12:44 --> 00:12:46 gravitational time dilation as I
00:12:46 --> 00:12:48 understand it. Our clock runs slightly
00:12:48 --> 00:12:50 slower because we're at the bottom of a
00:12:50 --> 00:12:51 gravity well, but that is hugely
00:12:51 --> 00:12:53 overcome by the fact of the high speed
00:12:53 --> 00:12:55 things are moving in orbit. You're
00:12:55 --> 00:12:58 talking several kilometers per second.
00:12:58 --> 00:13:01 Now, under general and special
00:13:01 --> 00:13:04 relativity, you can work out the number
00:13:04 --> 00:13:06 of seconds you experience per second
00:13:06 --> 00:13:08 that ticks in a certain rest frame using
00:13:08 --> 00:13:10 these equations to get the time
00:13:10 --> 00:13:13 dilation. And typically that is a
00:13:13 --> 00:13:14 vanishingly vanishingly small effect
00:13:14 --> 00:13:16 unless you get very near the speed of
00:13:16 --> 00:13:19 light and then it ramps up. But it is a
00:13:19 --> 00:13:22 large enough effect that both we need to
00:13:22 --> 00:13:26 understand it and we can measure it. Now
00:13:26 --> 00:13:28 to illustrate the level of this, it's
00:13:28 --> 00:13:30 not a huge effect. There's a fabulous
00:13:30 --> 00:13:33 stat that there are people who spent
00:13:33 --> 00:13:35 time on the International Space Station
00:13:35 --> 00:13:36 who therefore technically have
00:13:36 --> 00:13:38 experienced less time passing while they
00:13:38 --> 00:13:40 were up there than we did on the ground
00:13:40 --> 00:13:42 watching them. because of time dilation,
00:13:42 --> 00:13:43 because of their fast movement and their
00:13:43 --> 00:13:45 acceleration and all the rest of it.
00:13:45 --> 00:13:47 Space stations going around the earth
00:13:47 --> 00:13:49 what nearly 8 km/s
00:13:49 --> 00:13:51 roughly. A couple of Russian guys were
00:13:51 --> 00:13:54 up there for 6 months. Sergey Criclev
00:13:54 --> 00:13:58 and Sergey Avd, they did 6 months up
00:13:58 --> 00:14:01 there and as a result of time dilation,
00:14:01 --> 00:14:03 when they returned to the surface of the
00:14:03 --> 00:14:05 earth, they would have experienced less
00:14:05 --> 00:14:07 time passing than the people on the
00:14:07 --> 00:14:09 ground did while they were up there.
00:14:09 --> 00:14:10 >> Yeah. but not enough for them to
00:14:10 --> 00:14:12 perceive. It would have been 20
00:14:12 --> 00:14:13 milliseconds,
00:14:13 --> 00:14:13 >> right?
00:14:14 --> 00:14:18 >> So that's 0.02 seconds. Um 21th of a
00:14:18 --> 00:14:20 second. It's not very much, but it has a
00:14:20 --> 00:14:23 huge impact on our day-to-day life. And
00:14:23 --> 00:14:26 this means that that part of the
00:14:26 --> 00:14:29 theories of relativity are among the
00:14:29 --> 00:14:31 most tested theories ever to have been
00:14:31 --> 00:14:33 developed by humans. And the reason I
00:14:33 --> 00:14:35 say that is that every time you use your
00:14:35 --> 00:14:38 generic fruitbased device to navigate,
00:14:38 --> 00:14:41 anytime you use a satnav, you're using
00:14:41 --> 00:14:43 GPS satellites.
00:14:43 --> 00:14:46 GPS satellites orbiting the Earth allow
00:14:46 --> 00:14:48 you to work out your position on a basic
00:14:48 --> 00:14:51 level because at any time your device
00:14:51 --> 00:14:54 can see signals from a number of those
00:14:54 --> 00:14:56 satellites
00:14:56 --> 00:14:59 and figure out where they are. There are
00:14:59 --> 00:15:00 clocks on board all of them. you know,
00:15:00 --> 00:15:02 it can figure out the like travel time
00:15:02 --> 00:15:04 to get to it. By seeing the time that
00:15:04 --> 00:15:06 they're broadcasting, knowing what your
00:15:06 --> 00:15:08 local time is, figuring out the
00:15:08 --> 00:15:09 difference between the two, you know,
00:15:09 --> 00:15:11 how far away the satellite is from one
00:15:11 --> 00:15:13 of them, that places you at any point on
00:15:13 --> 00:15:14 a sphere around that satellite that is
00:15:14 --> 00:15:16 that distance away. From a second
00:15:16 --> 00:15:18 satellite, you've got another sphere,
00:15:18 --> 00:15:19 and you're where they intersect, which
00:15:19 --> 00:15:22 gives you a line. And then a third one
00:15:22 --> 00:15:23 brings it down to a point. And the more
00:15:23 --> 00:15:26 you have, the more accurate you get. So
00:15:26 --> 00:15:27 this is all based on measurement of
00:15:28 --> 00:15:31 time, allowing you to measure distance
00:15:31 --> 00:15:33 for things that are at a known distance
00:15:33 --> 00:15:36 away. This only works so if you can take
00:15:36 --> 00:15:38 into account the way that the clocks are
00:15:38 --> 00:15:40 ticking at different speeds because the
00:15:40 --> 00:15:42 satellites are moving in orbit around
00:15:42 --> 00:15:43 the Earth.
00:15:43 --> 00:15:47 The difference including relativistic
00:15:47 --> 00:15:49 effects and time dilation into the
00:15:49 --> 00:15:52 calculations for GPS has my
00:15:52 --> 00:15:53 understanding is it's between a factor
00:15:53 --> 00:15:56 of 10 and a factor of 100 on the
00:15:56 --> 00:15:58 precision with which your location be
00:15:58 --> 00:16:00 can can be calculated and your GPS is
00:16:00 --> 00:16:02 usually good to probably about a meter.
00:16:02 --> 00:16:04 I think some of the modern ones are even
00:16:04 --> 00:16:06 more accurate than that. So if you
00:16:06 --> 00:16:07 imagine that let's take the really
00:16:08 --> 00:16:09 optimistic case that you're only getting
00:16:09 --> 00:16:11 a factor of 10 improvement by including
00:16:11 --> 00:16:13 relativity at the minute you've got an
00:16:13 --> 00:16:15 accuracy of 1 meter and that's good
00:16:15 --> 00:16:16 enough for you to navigate with 10 m it
00:16:16 --> 00:16:19 probably wouldn't be with 100 m it
00:16:19 --> 00:16:21 certainly wouldn't be. So our GPS
00:16:22 --> 00:16:26 systems only work because of our level
00:16:26 --> 00:16:28 of understanding of relativistic motion
00:16:28 --> 00:16:31 and of time dilation. So those
00:16:31 --> 00:16:33 satellites moving very very quickly
00:16:33 --> 00:16:35 around the earth
00:16:35 --> 00:16:37 are experiencing an infinite decimally
00:16:37 --> 00:16:39 small amount of time dilation compared
00:16:39 --> 00:16:40 to the things they're broadcasting to on
00:16:40 --> 00:16:41 the surface
00:16:41 --> 00:16:43 >> and we have to factor that in into our
00:16:43 --> 00:16:45 calculations to navigate. So your satnav
00:16:45 --> 00:16:48 wouldn't work without the theorems that
00:16:48 --> 00:16:50 Albert Einstein put together more than a
00:16:50 --> 00:16:51 century ago
00:16:52 --> 00:16:53 >> that are all about how things move
00:16:53 --> 00:16:54 through time.
00:16:54 --> 00:16:56 >> So hopefully that has answered that
00:16:56 --> 00:16:59 question. I think Renie, I would be very
00:16:59 --> 00:17:00 tempted to suggest that at some point
00:17:00 --> 00:17:02 you try and get friend to answer that as
00:17:02 --> 00:17:05 well, just to see where he took it. Um,
00:17:05 --> 00:17:06 but hopefully that at least is helpful.
00:17:06 --> 00:17:08 And like I say, if the relativistic
00:17:08 --> 00:17:10 stuff really interests you, spacetime
00:17:10 --> 00:17:12 physics, even though it's a book that
00:17:12 --> 00:17:14 was first published 60 years ago, I
00:17:14 --> 00:17:16 found invaluable in getting me through
00:17:16 --> 00:17:18 the exams and actually allowed me to get
00:17:18 --> 00:17:19 out of my first year and pass rather
00:17:20 --> 00:17:21 than being kicked out of uni. So, it was
00:17:21 --> 00:17:24 a great book. H uh Renie might also like
00:17:24 --> 00:17:26 to go on Wikipedia or any number of
00:17:26 --> 00:17:29 platforms and look up the twin paradox.
00:17:29 --> 00:17:30 That's a fun one. That's a great thought
00:17:30 --> 00:17:33 experiment. And I think there were twin
00:17:33 --> 00:17:36 astronauts that have uh had a little bit
00:17:36 --> 00:17:38 of a separation in age because one of
00:17:38 --> 00:17:41 them spent spent much more time in space
00:17:41 --> 00:17:44 than his brother. So um their age
00:17:44 --> 00:17:47 difference uh increased by 8.6
00:17:47 --> 00:17:49 milliseconds or something something like
00:17:49 --> 00:17:50 that.
00:17:50 --> 00:17:52 >> I've seen Yeah,
00:17:52 --> 00:17:54 >> there are a couple of well there are
00:17:54 --> 00:17:56 many science fiction books that play
00:17:56 --> 00:17:58 around this. I've spoken before about
00:17:58 --> 00:17:59 this series of science fiction books
00:17:59 --> 00:18:01 called the mass works of science fiction
00:18:01 --> 00:18:03 which was an attempt by a publisher to
00:18:03 --> 00:18:05 make money obviously but also to bring
00:18:05 --> 00:18:07 back some classic science fiction that
00:18:07 --> 00:18:10 is regarded as being very good and you
00:18:10 --> 00:18:12 know some of the things I read are very
00:18:12 --> 00:18:13 fun but they're not necessarily very
00:18:13 --> 00:18:15 good. You know, there's always that side
00:18:15 --> 00:18:16 of things. And I'd say the Chrysis books
00:18:16 --> 00:18:18 I'm reading at the minute, the guy
00:18:18 --> 00:18:20 incarnated into the body of an ant,
00:18:20 --> 00:18:22 that's very good fun. I'm really loving
00:18:22 --> 00:18:23 it, but I wouldn't necessarily say
00:18:23 --> 00:18:25 they're high literature. They're fun.
00:18:25 --> 00:18:27 Um, the practic stuff is a bit of both,
00:18:27 --> 00:18:30 but these mass works of science fiction
00:18:30 --> 00:18:34 are often fascinating because they are
00:18:34 --> 00:18:36 quite often hard sci-fi. So in other
00:18:36 --> 00:18:37 words, there science fiction that is
00:18:37 --> 00:18:39 grounded in our understanding of science
00:18:39 --> 00:18:41 at the time they were written and tries
00:18:41 --> 00:18:44 to use the laws of physics to help build
00:18:44 --> 00:18:46 the narrative rather than waving the
00:18:46 --> 00:18:48 laws of physics to allow the narrative.
00:18:48 --> 00:18:49 You know, there's a fundamental
00:18:49 --> 00:18:50 difference between the soft and woolly
00:18:50 --> 00:18:53 sci-fi and the hard scientific sci-fi.
00:18:53 --> 00:18:55 And two books in particular that leap to
00:18:56 --> 00:18:57 mind when we're talking about time
00:18:57 --> 00:18:58 dilation and relativity and things like
00:18:58 --> 00:19:02 that are The Forever War by Joe Heburn,
00:19:02 --> 00:19:04 I think his name was. I'll just put that
00:19:04 --> 00:19:07 name up. The Forever War um was
00:19:07 --> 00:19:10 basically yeah Joe Holderman. Um the
00:19:10 --> 00:19:13 idea that there is um it's written in
00:19:13 --> 00:19:15 1974. It's called military science
00:19:15 --> 00:19:17 fiction. And the idea is humans are
00:19:17 --> 00:19:19 fighting an interstellar war against
00:19:19 --> 00:19:21 these alien civilization. And they're
00:19:21 --> 00:19:23 sent off on missions on spacecraft that
00:19:23 --> 00:19:25 travel at relativistic speed because it
00:19:25 --> 00:19:26 takes a hell of a long time to get
00:19:26 --> 00:19:28 anywhere. And it's not really about what
00:19:28 --> 00:19:29 they do when they get there. It's about
00:19:30 --> 00:19:31 what they do when they come back.
00:19:31 --> 00:19:32 Because the time you've gone there and
00:19:32 --> 00:19:34 come back, the earth has moved on
00:19:34 --> 00:19:36 hugely. You know, you've been away for
00:19:36 --> 00:19:38 five years, but earth has skipped
00:19:38 --> 00:19:39 forward 100 years.
00:19:40 --> 00:19:41 >> Can you reintegrate? How has society
00:19:42 --> 00:19:44 changed? And I think it's fair to say
00:19:44 --> 00:19:46 that without a spoiler,
00:19:46 --> 00:19:48 >> the motivation is that you've more in
00:19:48 --> 00:19:50 common with the people you've lived that
00:19:50 --> 00:19:51 experience with than you do with
00:19:51 --> 00:19:52 everybody else.
00:19:52 --> 00:19:55 >> And it's all about that. grounded in
00:19:56 --> 00:19:59 this knowledge of time dilation. I have
00:19:59 --> 00:20:00 traveled there and back again and come
00:20:00 --> 00:20:02 back to a world that is changed. The
00:20:02 --> 00:20:04 other one that really stuck in my mind
00:20:04 --> 00:20:07 as a interesting way to get your head
00:20:07 --> 00:20:08 around time dilation is a book called
00:20:08 --> 00:20:11 Talzer by Paul Anderson and I think that
00:20:11 --> 00:20:12 was published even longer ago. I think
00:20:12 --> 00:20:15 it was probably in the 1950s and part of
00:20:15 --> 00:20:17 the reason I can say that is that that
00:20:17 --> 00:20:20 book I believe predates the Big Bang
00:20:20 --> 00:20:23 Theory um or it's around the time of the
00:20:23 --> 00:20:25 Big Bang Theory. It's um based on a
00:20:25 --> 00:20:27 short story published in 1967. The book
00:20:27 --> 00:20:30 itself was published in 1970. So it's a
00:20:30 --> 00:20:33 a fabulous exploration of it was
00:20:33 --> 00:20:35 actually post Big Bang, but it's a
00:20:35 --> 00:20:38 fabulous exploration of relativity in an
00:20:38 --> 00:20:39 unusual circumstance. In this case, it
00:20:39 --> 00:20:42 was people being the first humans to
00:20:42 --> 00:20:45 travel to the stars on a spaceship that
00:20:45 --> 00:20:48 was meant to go to a star and then come
00:20:48 --> 00:20:50 back and report. Um they were aiming to
00:20:50 --> 00:20:53 reach beta vaginis. It says crew of 50,
00:20:53 --> 00:20:56 25 men, 25 women using something called
00:20:56 --> 00:20:59 a busard ramjet. So you have basically a
00:20:59 --> 00:21:01 rocket that scoops up fuel and burns it
00:21:01 --> 00:21:04 to go faster and faster, right? Um, but
00:21:04 --> 00:21:05 there's a problem. They get up to high
00:21:05 --> 00:21:07 speed and then something breaks, but
00:21:07 --> 00:21:08 they're going so quick that they can't
00:21:08 --> 00:21:11 get outside the spacecraft to fix it.
00:21:11 --> 00:21:13 And so they just have to go quicker and
00:21:13 --> 00:21:16 quicker. And so it explores this captive
00:21:16 --> 00:21:19 group of 50 people on an island in the
00:21:19 --> 00:21:21 universe that cannot stop, can only go
00:21:21 --> 00:21:23 quicker and quicker as the universe
00:21:23 --> 00:21:25 moves around them. And of course, by
00:21:25 --> 00:21:26 continually accelerating, they get
00:21:26 --> 00:21:28 closer and closer to the speed of light.
00:21:28 --> 00:21:30 And time dilation impacts them more and
00:21:30 --> 00:21:33 more. So they see the universe to the
00:21:33 --> 00:21:36 end of the universe and beyond
00:21:36 --> 00:21:39 >> within a human lifetime. And you know,
00:21:39 --> 00:21:40 the cosmology in it has changed. It was
00:21:40 --> 00:21:42 at a time where the big bang a lot of
00:21:42 --> 00:21:43 people thought would end up in a big
00:21:43 --> 00:21:44 crunch that everything would stop
00:21:44 --> 00:21:47 expanding fall back together. But it's
00:21:47 --> 00:21:52 again this awesome way of demonstrating
00:21:52 --> 00:21:55 how relativistic terms work. And the
00:21:55 --> 00:21:57 crew on the mission before anything went
00:21:57 --> 00:21:58 wrong were aware that when they returned
00:21:58 --> 00:22:02 to Earth, something like 33 years would
00:22:02 --> 00:22:03 have passed before they get to their
00:22:03 --> 00:22:05 destination, this star. But for them,
00:22:06 --> 00:22:07 only 5 years would have passed. So when
00:22:07 --> 00:22:08 they turn around and come home, they'll
00:22:08 --> 00:22:10 have aged 10 years. But 66 years would
00:22:10 --> 00:22:11 have passed on Earth, give or take.
00:22:11 --> 00:22:12 >> Yeah, that that's
00:22:12 --> 00:22:14 >> In fact, that doesn't happen. Wonderful
00:22:14 --> 00:22:15 book.
00:22:15 --> 00:22:16 >> Yeah,
00:22:16 --> 00:22:18 >> it I love those sorts of stories. I I I
00:22:18 --> 00:22:22 love time, travel, sci-fi, and uh um all
00:22:22 --> 00:22:27 those relativistic uh concepts. I Yeah,
00:22:27 --> 00:22:29 I'm actually just finished writing a
00:22:29 --> 00:22:30 trilogy, and I'm just getting it proof
00:22:30 --> 00:22:32 read at the moment. Um Oh, fabulous.
00:22:32 --> 00:22:33 >> And there's a little bit of that in it,
00:22:33 --> 00:22:36 >> but I'm not giving anything away. So, so
00:22:36 --> 00:22:38 maybe without without any spoilers at
00:22:38 --> 00:22:40 all that in a few years time maybe I'll
00:22:40 --> 00:22:41 be picking up your books as part of the
00:22:42 --> 00:22:43 mass works of science fiction.
00:22:43 --> 00:22:45 >> You might.
00:22:45 --> 00:22:45 >> That'd be nice, wouldn't it?
00:22:46 --> 00:22:46 >> No pressure.
00:22:46 --> 00:22:49 >> No. Well, okay.
00:22:49 --> 00:22:51 Uh, thanks Randy. Um, enjoyed that
00:22:51 --> 00:22:53 question. It's a It's a fun one to talk
00:22:53 --> 00:22:55 about. This is Space Nuts with Andrew
00:22:55 --> 00:22:58 Dunley and Professor Jonty Horner.
00:22:58 --> 00:22:59 Let's take a short break from the show
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00:24:46 --> 00:24:47 Think
00:24:47 --> 00:24:49 >> we need to do a little more all weather
00:24:49 --> 00:24:50 testing.
00:24:50 --> 00:24:52 >> Amen. Space nets.
00:24:52 --> 00:24:54 >> Our next question, Jonty, comes from
00:24:54 --> 00:24:57 Paul in Brisbane, although uh he doesn't
00:24:57 --> 00:24:58 call it Brisbane. You've probably heard
00:24:58 --> 00:25:01 this term because um you live so close
00:25:01 --> 00:25:03 to Brisbane, but overseas people might
00:25:03 --> 00:25:04 think, what on earth is he talking
00:25:04 --> 00:25:07 about? Good day, Space Nuts. Paul uh
00:25:07 --> 00:25:11 from sunny Bris Vegas uh here and he's
00:25:11 --> 00:25:13 thrown a challenge at me. Before I ask
00:25:13 --> 00:25:15 my question, could you read it in a
00:25:15 --> 00:25:18 Queensland accent to make it sound
00:25:18 --> 00:25:21 authentic? Andrew T,
00:25:21 --> 00:25:22 I'll give it a go, Paul. But, you know,
00:25:22 --> 00:25:24 it's been a long time since I lived in
00:25:24 --> 00:25:27 Queensland. I was thinking just
00:25:27 --> 00:25:31 listening in episode 681 when you and
00:25:31 --> 00:25:33 Fred started talking uh about the
00:25:34 --> 00:25:37 possibility of Titan and Hypernian
00:25:37 --> 00:25:39 Hyperion Collidon, uh, thus creating
00:25:39 --> 00:25:43 Saturn's rings 100 million years ago. Uh
00:25:43 --> 00:25:46 what do you reckon the odds are of some
00:25:46 --> 00:25:48 of the bigger blocks of the collision
00:25:48 --> 00:25:51 spinning off into space uh getting
00:25:51 --> 00:25:53 closer to the sun? I don't know.
00:25:53 --> 00:25:56 Colliding with the Earth, say 65 million
00:25:56 --> 00:25:59 years ago. Is that a possibility? Or
00:25:59 --> 00:26:02 does the chemical residue from on here
00:26:02 --> 00:26:05 on Earth suggest there's more likely to
00:26:06 --> 00:26:08 have been a comet? Curious to get your
00:26:08 --> 00:26:11 thoughts on this, eh? Uh, as always,
00:26:11 --> 00:26:15 keep up the great work and thank you.
00:26:15 --> 00:26:17 Was that Queenslandish enough?
00:26:17 --> 00:26:19 >> Uh, theatrical. So, the accent thing and
00:26:19 --> 00:26:21 again, we're very good at getting off
00:26:21 --> 00:26:21 topic or I am.
00:26:22 --> 00:26:23 >> Depends what part of Queensland because
00:26:23 --> 00:26:25 it's a big state.
00:26:25 --> 00:26:26 >> For people listening
00:26:26 --> 00:26:28 >> and you got to you got to chuck in an A
00:26:28 --> 00:26:30 on the end of every sentence.
00:26:30 --> 00:26:33 >> One of the things that's always made my
00:26:33 --> 00:26:34 head hurt a little bit since I moved to
00:26:34 --> 00:26:36 Australia in 2010 and I am officially
00:26:36 --> 00:26:37 Australian, you know.
00:26:37 --> 00:26:39 >> Yeah. is a lack of diversity in the
00:26:39 --> 00:26:43 accents. I I grew up in the UK where
00:26:43 --> 00:26:45 accents are very very varied to the
00:26:45 --> 00:26:46 extent that you could tell within my
00:26:46 --> 00:26:47 school which estate people grew up in
00:26:47 --> 00:26:49 because of subtleties in their accent
00:26:49 --> 00:26:52 locally. And the variation on the larger
00:26:52 --> 00:26:55 scale is astonishing. It's part of why I
00:26:55 --> 00:26:57 I think British actors have so much
00:26:57 --> 00:27:00 success, partly because they get very
00:27:00 --> 00:27:01 good training, of course, but if you're
00:27:01 --> 00:27:03 an actor in the UK, you have to have a
00:27:03 --> 00:27:05 fluidity with accents because there's
00:27:05 --> 00:27:07 such a diversity just within the UK.
00:27:07 --> 00:27:07 >> Yeah.
00:27:08 --> 00:27:11 >> And I came to Australia and I do not
00:27:11 --> 00:27:12 I've lost some of my ear for the UK
00:27:12 --> 00:27:14 accents. I used to be really good
00:27:14 --> 00:27:15 because you grow up there, it's a
00:27:15 --> 00:27:17 natural thing. I've lost a bit of that,
00:27:17 --> 00:27:20 >> but over here it seems to be there isn't
00:27:20 --> 00:27:22 a very strong regional diversity.
00:27:22 --> 00:27:24 There's just a little bit of town versus
00:27:24 --> 00:27:26 country and a very little bit of north
00:27:26 --> 00:27:30 south, but it's very smooth, although
00:27:30 --> 00:27:31 very little variety.
00:27:31 --> 00:27:34 >> I'll tell you, when I got into radio, I
00:27:34 --> 00:27:37 um did a demo tape and I had a friend
00:27:37 --> 00:27:39 listen to it who'd been in radio a very
00:27:39 --> 00:27:40 long time and I was only just starting
00:27:40 --> 00:27:42 out and he listened to it and he said,
00:27:42 --> 00:27:44 "You know, you've got to get rid of rid
00:27:44 --> 00:27:46 of your Newcastle twang." Cuz I grew up
00:27:46 --> 00:27:48 in the Hunter Valley um in that
00:27:48 --> 00:27:50 Newcastle district. And I said, "What?"
00:27:50 --> 00:27:52 He said, "You've got a Newcastle twang.
00:27:52 --> 00:27:55 There's a certain sound that comes out
00:27:55 --> 00:27:58 of the mouths of Navicestrians. You got"
00:27:58 --> 00:28:00 And I had to get I had to train that out
00:28:00 --> 00:28:01 of myself
00:28:01 --> 00:28:04 >> and and it it it can be no disrespect,
00:28:04 --> 00:28:06 but it can be a bit grating.
00:28:06 --> 00:28:10 >> Um but there there is there are
00:28:10 --> 00:28:13 diversities in in accent across
00:28:13 --> 00:28:15 Australia that when I worked for the
00:28:15 --> 00:28:17 ABC, they actually published a map of
00:28:17 --> 00:28:18 accents.
00:28:18 --> 00:28:19 >> Yeah. Yeah.
00:28:19 --> 00:28:21 >> And I think the most prominent variation
00:28:21 --> 00:28:23 is South Australia, particularly
00:28:23 --> 00:28:26 Adelaide. Much more posh,
00:28:26 --> 00:28:29 >> but it's also to me it's much more
00:28:29 --> 00:28:30 evidence because I just don't quite have
00:28:30 --> 00:28:32 the air for it cuz in the UK the accents
00:28:32 --> 00:28:34 are very much more val. So Newcastle
00:28:34 --> 00:28:36 accent to me is very different to what
00:28:36 --> 00:28:37 you think of a Newcastle accent.
00:28:37 --> 00:28:39 >> But where I see it is in language. So
00:28:39 --> 00:28:42 there's the the perennial argument among
00:28:42 --> 00:28:44 Australians of whether it's a potato
00:28:44 --> 00:28:46 cape or a potato scholar is a good
00:28:46 --> 00:28:47 example. you got regional things like
00:28:47 --> 00:28:49 that and for
00:28:49 --> 00:28:51 >> from my side of things I worked in
00:28:51 --> 00:28:52 Switzerland for 3 years
00:28:52 --> 00:28:55 >> and shared an office with Haga who was
00:28:55 --> 00:28:58 this young woman from I think Iran or
00:28:58 --> 00:29:00 somewhere Persian I'm not sure exactly
00:29:00 --> 00:29:02 where but we communicated in English
00:29:02 --> 00:29:04 which was her sixth language
00:29:04 --> 00:29:05 >> wow
00:29:05 --> 00:29:07 >> which was astonishing to me but there
00:29:07 --> 00:29:09 was one time I've been on the phone to
00:29:09 --> 00:29:10 my parents and I finished and she said
00:29:10 --> 00:29:14 so Johny what does a mean up and yeah a
00:29:14 --> 00:29:17 up um and It reminds me of the wonderful
00:29:17 --> 00:29:19 >> Isn't that Liverpoolian that
00:29:19 --> 00:29:22 >> no aopsy Yorkshire as well? Not far.
00:29:22 --> 00:29:24 >> If you want to see the accent of roughly
00:29:24 --> 00:29:26 where I grew up incidentally, it's worth
00:29:26 --> 00:29:29 people looking up the fabulous song Ilk
00:29:29 --> 00:29:31 Batat which is a cultural treasure from
00:29:31 --> 00:29:33 my part of the world and we all learned
00:29:33 --> 00:29:35 when we were in Scouts and at school and
00:29:35 --> 00:29:37 it's um basically group of group of
00:29:37 --> 00:29:39 fellas at the pub saying where where
00:29:39 --> 00:29:41 have you been since I saw you last? been
00:29:41 --> 00:29:42 you've been caught in Mary Jane and it
00:29:42 --> 00:29:45 goes on about how he's not been dressed
00:29:45 --> 00:29:46 appropriately and he's going to die in
00:29:46 --> 00:29:48 the laughter burium and but it's all in
00:29:48 --> 00:29:50 very strong dialect so you can see that
00:29:50 --> 00:29:53 but what that resulted in is everybody
00:29:53 --> 00:29:56 in burn communicated in English at the
00:29:56 --> 00:29:58 physical institute I had speak German
00:29:58 --> 00:30:01 when I was out in the town but English
00:30:01 --> 00:30:03 has become this kind of lingua frana
00:30:03 --> 00:30:06 lingua lingua frana there because
00:30:06 --> 00:30:07 Switzerland is a country with four
00:30:07 --> 00:30:08 different languages it's got French
00:30:08 --> 00:30:10 German Italian and romance
00:30:10 --> 00:30:12 But everybody's proud of their language.
00:30:12 --> 00:30:14 The French speakers will not silly
00:30:14 --> 00:30:16 themselves by speaking German to the
00:30:16 --> 00:30:18 German speakers. The German speakers
00:30:18 --> 00:30:20 therefore will not silly themselves by
00:30:20 --> 00:30:21 speaking the foul French to the French
00:30:22 --> 00:30:22 speakers.
00:30:22 --> 00:30:23 >> Yeah.
00:30:23 --> 00:30:25 >> So they speak English.
00:30:25 --> 00:30:28 Um but that means people have very good
00:30:28 --> 00:30:29 English, but they've learned a lot of
00:30:29 --> 00:30:31 their English from watching American TV
00:30:31 --> 00:30:33 rather than British TV. But even the
00:30:33 --> 00:30:35 British TV is a little bit denuded in
00:30:35 --> 00:30:40 terms of accent and um in terms
00:30:40 --> 00:30:43 particularly of dialect terms
00:30:43 --> 00:30:44 and it was to an extent we were talking
00:30:44 --> 00:30:46 about the accents the news presenters
00:30:46 --> 00:30:48 until about 20 or 30 years ago on the
00:30:48 --> 00:30:50 BBC had to use received pronunciation
00:30:50 --> 00:30:52 which is the Queen's English and you
00:30:52 --> 00:30:54 have to speak very properly and they got
00:30:54 --> 00:30:55 rid of that because people realize that
00:30:55 --> 00:30:57 actually diversity in accents represents
00:30:57 --> 00:30:58 the diversity of people and that's
00:30:58 --> 00:31:01 great. What that meant though was uh my
00:31:02 --> 00:31:03 accent I've reliably been told is
00:31:03 --> 00:31:06 relatively strong. But I don't really
00:31:06 --> 00:31:08 use any dialect terms anymore other than
00:31:08 --> 00:31:10 the o bit of Aussie stuff I've picked up
00:31:10 --> 00:31:11 because what was really throwing people
00:31:11 --> 00:31:14 in Switzerland was the dialect terms,
00:31:14 --> 00:31:17 not the accents, things like a up. And
00:31:17 --> 00:31:19 so my language has shifted. I've lost a
00:31:19 --> 00:31:20 bit of an A for the UK stuff, but I
00:31:20 --> 00:31:23 don't hear much variety in the
00:31:23 --> 00:31:25 Australian accent. Now, part of that is
00:31:25 --> 00:31:29 because I'm not from here, but I I
00:31:29 --> 00:31:30 always find that kind of stuff really
00:31:30 --> 00:31:32 really interesting. So, I mean, I could
00:31:32 --> 00:31:33 tell you were getting a stronger
00:31:33 --> 00:31:36 Australian accent. Um, but it wasn't
00:31:36 --> 00:31:37 necessarily I couldn't have told you
00:31:37 --> 00:31:40 where it was from. Other thing is,
00:31:40 --> 00:31:41 again, saw an interesting discussion
00:31:42 --> 00:31:43 online about the Australian accent
00:31:43 --> 00:31:45 changing over time, asking why when you
00:31:45 --> 00:31:49 watch Aussie films and TVs from 30, 40,
00:31:49 --> 00:31:51 50 years ago, everybody almost sounds
00:31:51 --> 00:31:52 like they're a pastiche of the
00:31:52 --> 00:31:54 Australian accent. It's so full on and
00:31:54 --> 00:31:57 there's so many terms and insults and
00:31:57 --> 00:31:59 stuff that aren't used today. Yeah.
00:31:59 --> 00:32:02 >> And apparently part of it is language
00:32:02 --> 00:32:03 evolves. We've got all these
00:32:03 --> 00:32:05 multicultural influence. We've got all
00:32:05 --> 00:32:06 that stuff. But also apparently the
00:32:06 --> 00:32:09 actors were trained to ham it up.
00:32:09 --> 00:32:12 >> Oh, absolutely. That's exactly what it
00:32:12 --> 00:32:14 was. And and uh see what you started,
00:32:14 --> 00:32:17 Paul. But uh I understand because I did
00:32:17 --> 00:32:18 some research on it. The Australian
00:32:18 --> 00:32:23 accent came about because we were
00:32:23 --> 00:32:25 a colony of convicts brought over from
00:32:25 --> 00:32:28 the UK, but the convicts were all from
00:32:28 --> 00:32:30 different walks of life, but they were
00:32:30 --> 00:32:33 conglomerated into a new community and
00:32:33 --> 00:32:36 all their accents merged into what is
00:32:36 --> 00:32:39 now the Australian accent. So you know
00:32:39 --> 00:32:41 you you you had Welsh, you had Irish,
00:32:42 --> 00:32:44 you had Scottish, you had English or
00:32:44 --> 00:32:46 with all the variations all coming
00:32:46 --> 00:32:48 together and creating the Australian
00:32:48 --> 00:32:51 accent. So that's why it is what it is.
00:32:51 --> 00:32:51 >> Yes.
00:32:51 --> 00:32:53 >> But it's ever evolving too.
00:32:53 --> 00:32:54 >> And it's a wonderful thing. It does
00:32:54 --> 00:32:56 change over time which I found
00:32:56 --> 00:32:58 interesting. Anyway, sorry about that.
00:32:58 --> 00:32:59 We get off topic wonderfully,
00:32:59 --> 00:33:00 wonderfully. Well, Saturn,
00:33:00 --> 00:33:02 >> we're good at that. So Fred started
00:33:02 --> 00:33:03 talking about the possibility of Titan
00:33:03 --> 00:33:06 and a Hyperion colliding and what
00:33:06 --> 00:33:08 happened to the stuff. Could a big rock
00:33:08 --> 00:33:10 from that event have hit Earth 65
00:33:10 --> 00:33:11 million years ago and you know what he's
00:33:12 --> 00:33:13 talking about there or did it all just
00:33:13 --> 00:33:15 go flying off into space or did it do
00:33:15 --> 00:33:18 something else etc etc.
00:33:18 --> 00:33:19 >> All all sorts of ways we can go with
00:33:20 --> 00:33:23 this. So the origin of Saturn's rings
00:33:23 --> 00:33:25 first and foremost is not yet
00:33:25 --> 00:33:27 definitively known. We know that there
00:33:27 --> 00:33:29 are ring systems around Jupiter, Uranus
00:33:29 --> 00:33:31 and Neptune as well. We suspect strongly
00:33:31 --> 00:33:34 that in the past and in the future Mars
00:33:34 --> 00:33:37 has had and will have ring rings. I
00:33:37 --> 00:33:40 think red dwarfy has will have possibly
00:33:40 --> 00:33:42 going to have whatever it it may have
00:33:42 --> 00:33:43 had episodic rings in the past. We've
00:33:44 --> 00:33:45 found rings around a few of the solstice
00:33:45 --> 00:33:47 from smaller objects like um the
00:33:47 --> 00:33:50 centaurs Chiron and Currico. Um rings
00:33:50 --> 00:33:52 are a thing. We've also found
00:33:52 --> 00:33:54 potentially rings around exoplanets.
00:33:54 --> 00:33:55 Some debate about that. We find rings
00:33:55 --> 00:33:58 around stars in the form of debris discs
00:33:58 --> 00:34:00 and all the rest of it. Yeah,
00:34:00 --> 00:34:03 ever since Saturn's rings were known,
00:34:03 --> 00:34:05 there's been ongoing how did they get
00:34:05 --> 00:34:08 there? And there is an ongoing not only
00:34:08 --> 00:34:09 how did they get there, but are they
00:34:09 --> 00:34:12 transient or permanent? And there are a
00:34:12 --> 00:34:14 wide variety of opinions on this and
00:34:14 --> 00:34:16 modeling has not yet come down strongly
00:34:16 --> 00:34:19 one way or the other. Currently, the
00:34:19 --> 00:34:20 best thinking about Saturn's rings is
00:34:20 --> 00:34:23 that they are more likely to be new than
00:34:23 --> 00:34:26 old. So we're probably seeing a ring
00:34:26 --> 00:34:29 system that has in bulk not existed
00:34:29 --> 00:34:32 since the birth of the solar system and
00:34:32 --> 00:34:35 estimates of the age range from 10 to
00:34:35 --> 00:34:38 100 to 300 million years. These
00:34:38 --> 00:34:40 estimates on the which the rings are
00:34:40 --> 00:34:43 being depleted suggest that they may
00:34:43 --> 00:34:45 well return to the level of Neptune,
00:34:45 --> 00:34:48 Uranus, Jupiter type rings within about
00:34:48 --> 00:34:52 300 million years from now. Those
00:34:52 --> 00:34:54 theories, those arguments
00:34:54 --> 00:34:56 would suggest that if the ring system is
00:34:56 --> 00:34:57 younger than the edge of the solar
00:34:57 --> 00:34:59 system, there had to be an event to
00:34:59 --> 00:35:01 bring it into being. Obviously, and
00:35:01 --> 00:35:03 there have been a number of different
00:35:03 --> 00:35:06 suggestions to cause this. One is that,
00:35:06 --> 00:35:08 and this was commonly argued when I was
00:35:08 --> 00:35:10 a kid learning about it, that Saturn had
00:35:10 --> 00:35:12 a comet or asteroid that got too close,
00:35:12 --> 00:35:14 was torn us under creating the rings.
00:35:14 --> 00:35:16 Now this invokes a part of planetary
00:35:16 --> 00:35:19 science knowledge and physics called the
00:35:19 --> 00:35:21 ro limit which is essentially if you
00:35:22 --> 00:35:24 have two massive objects and you bring
00:35:24 --> 00:35:26 them close enough together tidal effects
00:35:26 --> 00:35:29 will disrupt the smaller of them due to
00:35:29 --> 00:35:31 the gravity of the bigger of them. And
00:35:31 --> 00:35:33 the point there is if you think that the
00:35:33 --> 00:35:35 strength of the gravitational pull falls
00:35:35 --> 00:35:37 off as a square of the distance and
00:35:37 --> 00:35:39 you've got an object that's 100 km
00:35:39 --> 00:35:41 across, the side that is nearer a planet
00:35:41 --> 00:35:43 will be feeling a stronger pull than the
00:35:43 --> 00:35:45 side that's further away. Now depending
00:35:45 --> 00:35:47 on the strength of the object, that
00:35:47 --> 00:35:49 distance will vary. The stronger the
00:35:49 --> 00:35:51 object is, the closer it can get to a
00:35:51 --> 00:35:53 planet before disruption. But we have
00:35:53 --> 00:35:54 this concept of the ro limit. And
00:35:54 --> 00:35:57 Saturn's rings are within the ro limit,
00:35:57 --> 00:35:58 which is why they've been disrupted. And
00:35:58 --> 00:36:01 the largest objects in them are probably
00:36:01 --> 00:36:03 to be honest the shepherd moons that are
00:36:03 --> 00:36:06 kilometer scale objects which are
00:36:06 --> 00:36:08 probably due to the nature of the ro
00:36:08 --> 00:36:11 limit and stuff they're probably fairly
00:36:11 --> 00:36:12 rubbish rather than rubble panels
00:36:12 --> 00:36:13 because if they were rubble panels
00:36:13 --> 00:36:16 they'd get disintegrated. Um, so they're
00:36:16 --> 00:36:18 probably at a distance where they are
00:36:18 --> 00:36:20 within the ro limit for a fluid object
00:36:20 --> 00:36:22 that has no strength, but they are
00:36:22 --> 00:36:23 strong enough that the ro limit for them
00:36:23 --> 00:36:24 will be closer in. Anyway, a bit off
00:36:24 --> 00:36:26 topic there, but that's the physics
00:36:26 --> 00:36:28 behind it. And you can work out that ro
00:36:28 --> 00:36:30 limit either as a ratio of the mass of
00:36:30 --> 00:36:32 the object to the mass of the thing it's
00:36:32 --> 00:36:34 the bigger thing that it's coming near
00:36:34 --> 00:36:36 or as a ratio of the densities. It works
00:36:36 --> 00:36:40 either way, which is kind of cool. Um,
00:36:40 --> 00:36:43 that's what
00:36:43 --> 00:36:45 the physics is behind why you don't have
00:36:45 --> 00:36:46 a single object there. It can't form a
00:36:46 --> 00:36:48 single object. It's got to be broken up
00:36:48 --> 00:36:51 into debris. The rings are decaying.
00:36:51 --> 00:36:53 Dust is lost to Saturn all the time.
00:36:53 --> 00:36:55 They're also being slightly replenished
00:36:55 --> 00:36:56 by the activity particularly of
00:36:56 --> 00:36:58 Enceladus
00:36:58 --> 00:37:00 um, which is repopulating the earrings.
00:37:00 --> 00:37:03 So, there are system in flux and it's
00:37:03 --> 00:37:05 not clear exactly where they formed.
00:37:05 --> 00:37:07 There was the idea when I was a kid that
00:37:07 --> 00:37:08 it was a comed asteroid that was
00:37:08 --> 00:37:11 disrupted to make that much material. I
00:37:11 --> 00:37:13 think that has gone probably by the
00:37:13 --> 00:37:16 wayside because you need a way to
00:37:16 --> 00:37:18 dissipate the energy for an object to be
00:37:18 --> 00:37:21 captured. So if you have a comet or an
00:37:21 --> 00:37:22 asteroid get close enough to Saturn to
00:37:22 --> 00:37:25 be torn apart, that material is still
00:37:25 --> 00:37:27 moving faster than Saturn's escape
00:37:27 --> 00:37:29 velocity. So we just fly away, albeit
00:37:29 --> 00:37:29 torn apart.
00:37:29 --> 00:37:31 >> Right? If you have something that is
00:37:31 --> 00:37:34 temporarily captured as a satellite,
00:37:34 --> 00:37:36 it'll be on a fairly elongated orbit if
00:37:36 --> 00:37:37 it's going to get close enough to be
00:37:37 --> 00:37:39 disrupted and it will continue to follow
00:37:39 --> 00:37:41 that. So if you look at comet Schumac
00:37:41 --> 00:37:44 119 back in the 1990s, it came very
00:37:44 --> 00:37:46 close to Jupiter in 1992, I think, was
00:37:46 --> 00:37:48 torn apart so that we had many smaller
00:37:48 --> 00:37:50 comets that all followed essentially the
00:37:50 --> 00:37:53 same art orbit in a lengthy chain and
00:37:53 --> 00:37:56 fell apart, crashed into Jupiter one
00:37:56 --> 00:37:57 after the other over the space of a
00:37:57 --> 00:37:58 couple of weeks in 1994.
00:37:58 --> 00:38:01 >> That's right. They didn't form a ring
00:38:01 --> 00:38:02 system.
00:38:02 --> 00:38:02 >> No.
00:38:02 --> 00:38:04 >> When that had its first approach to
00:38:04 --> 00:38:06 Jupiter, it was torn apart, but it
00:38:06 --> 00:38:08 didn't make a new ring system. So, you
00:38:08 --> 00:38:10 need some way to dissipate the energy to
00:38:10 --> 00:38:11 trap all the debris onto a circular
00:38:11 --> 00:38:13 orbit near the planet. And it's very
00:38:13 --> 00:38:15 hard to visualize how you do that from
00:38:15 --> 00:38:17 an asteroid or comet passing through.
00:38:17 --> 00:38:21 So, that's led to instead the idea of
00:38:21 --> 00:38:23 the collision between two moons. Now,
00:38:23 --> 00:38:25 the most recent version I've seen
00:38:25 --> 00:38:28 discussed of this is that there was a
00:38:28 --> 00:38:31 moon that was possibly as large as
00:38:31 --> 00:38:34 Hyperion or even bigger
00:38:34 --> 00:38:37 that collided that sorry, whose orbit
00:38:37 --> 00:38:39 spiraled inwards to the point it crossed
00:38:39 --> 00:38:41 the ro limit. Now, we're seeing this
00:38:41 --> 00:38:44 happen with Phoebe, the innermost of
00:38:44 --> 00:38:46 Mars's two moons. Phoebe is closer to
00:38:46 --> 00:38:49 Mars than what we call the co- rotation
00:38:49 --> 00:38:51 altitude, which means its orbit around
00:38:51 --> 00:38:53 Mars takes less time than Mars takes to
00:38:53 --> 00:38:55 spin. And when you're closer than that
00:38:55 --> 00:38:57 co- rotation place, tidal forces will
00:38:57 --> 00:38:59 make you spiral inwards rather than
00:38:59 --> 00:39:00 spiraling outwards. Our moon's further
00:39:00 --> 00:39:02 out. It takes longer to orbit the Earth
00:39:02 --> 00:39:04 than the Earth takes to spin. So, it
00:39:04 --> 00:39:05 moves away.
00:39:05 --> 00:39:09 >> Yeah. Imagine then that you had a moon
00:39:09 --> 00:39:12 few hundred km across 200 300 400 km
00:39:12 --> 00:39:16 across close in that spiraled inwards
00:39:16 --> 00:39:17 and cross the ro limit it would be
00:39:17 --> 00:39:19 disrupted forming system that's one
00:39:19 --> 00:39:21 theory another is that you had a moon
00:39:21 --> 00:39:24 that was pretty close in that was then
00:39:24 --> 00:39:26 struck by an object large enough to
00:39:26 --> 00:39:30 shatter and disrupt it. that collisions
00:39:30 --> 00:39:33 of that size would be relatively rare
00:39:33 --> 00:39:34 these days because projectiles big
00:39:34 --> 00:39:37 enough to shatter a moon of that size
00:39:37 --> 00:39:40 are relatively scarce. Um, a more more
00:39:40 --> 00:39:42 recent version that's been proposed is
00:39:42 --> 00:39:44 that you had a much larger object,
00:39:44 --> 00:39:46 something more like the size of Titan
00:39:46 --> 00:39:49 and that was stripped off during the
00:39:49 --> 00:39:50 formation period of Saturn. There's all
00:39:50 --> 00:39:53 sorts of theories here, but like I say,
00:39:53 --> 00:39:54 we're not fully there yet. We're still
00:39:54 --> 00:39:57 exploring. That's where future missions
00:39:57 --> 00:39:59 to Saturn are going to teach us a lot
00:39:59 --> 00:40:02 more. Um, we've got an age here. Um,
00:40:02 --> 00:40:05 observations based on the KEK telescope
00:40:05 --> 00:40:07 suggests that the rings will be gone in
00:40:07 --> 00:40:09
00:40:09 --> 00:40:12 plus 818US 124 million years, which
00:40:12 --> 00:40:14 illustrates that as astronomers, we are
00:40:14 --> 00:40:16 terrible at choosing significant
00:40:16 --> 00:40:18 figures. And I tell my students this all
00:40:18 --> 00:40:19 the time because if you talk to a
00:40:19 --> 00:40:21 physicist, they'd see those numbers and
00:40:21 --> 00:40:23 weep because they'd say, "Well, that
00:40:23 --> 00:40:25 should just be 300 plus 800 minus 100
00:40:25 --> 00:40:26 because the other numbers are
00:40:26 --> 00:40:29 meaningless anyway." Um, but it's a very
00:40:29 --> 00:40:31 large uncertainty on how long they will
00:40:31 --> 00:40:33 take till they're gone. We don't know
00:40:33 --> 00:40:36 how massive they were initially, and how
00:40:36 --> 00:40:39 massive they are initially will be part
00:40:39 --> 00:40:41 of what determines
00:40:41 --> 00:40:43 how long they've been around.
00:40:43 --> 00:40:45 >> Uhhuh. Anyway, so that's why there's
00:40:45 --> 00:40:47 still a lot of misunderstanding and a
00:40:47 --> 00:40:49 lot of confusion there. And it may well
00:40:49 --> 00:40:51 be that rings of the scale of the rings
00:40:51 --> 00:40:53 of Saturn around the giant planets are
00:40:53 --> 00:40:55 an episodic thing. It may well be that
00:40:55 --> 00:40:58 planets like Saturn, Jupiter, Uranus,
00:40:58 --> 00:41:00 and Neptune have minor ring systems all
00:41:00 --> 00:41:02 the time, but occasionally they'll get a
00:41:02 --> 00:41:03 really good one. And it could be that in
00:41:03 --> 00:41:05 the past Jupiter had a massive ring
00:41:05 --> 00:41:07 system like this. And in the future,
00:41:07 --> 00:41:10 Uranus might, for example, Mars will
00:41:10 --> 00:41:11 probably get a ring system when um
00:41:12 --> 00:41:13 Phobos gets close enough and is
00:41:13 --> 00:41:15 disrupted.
00:41:15 --> 00:41:17 >> All that now to aside, the next part was
00:41:17 --> 00:41:20 about debris reaching us from the
00:41:20 --> 00:41:23 collision and reaching the Earth.
00:41:23 --> 00:41:24 >> Yeah.
00:41:24 --> 00:41:28 >> Um two parts to this. The first is that
00:41:28 --> 00:41:31 some material from that collision could
00:41:31 --> 00:41:32 potentially have reached Earth. I don't
00:41:32 --> 00:41:35 doubt that. I did work while I was at
00:41:35 --> 00:41:36 the University of Burn, which we talked
00:41:36 --> 00:41:39 about earlier, with a PhD student at the
00:41:39 --> 00:41:41 time called Augustine Anich, who was
00:41:41 --> 00:41:44 doing simulations of the giant collision
00:41:44 --> 00:41:46 that made Mercury the planet we know it
00:41:46 --> 00:41:49 is today. Mercury is over dense. It has
00:41:49 --> 00:41:51 an oversized core. And the thinking is
00:41:51 --> 00:41:53 it was probably once a planet twice the
00:41:53 --> 00:41:56 diameter of the current Mercury. And it
00:41:56 --> 00:41:58 had this massive collision that stripped
00:41:58 --> 00:41:59 it of its mantle and crust, leaving
00:41:59 --> 00:42:00 behind a core with a little bit of
00:42:00 --> 00:42:02 rubble on top. and he was doing
00:42:02 --> 00:42:05 simulations of that impact.
00:42:05 --> 00:42:07 And my contribution was I ran orbital
00:42:07 --> 00:42:09 mechanics simulations. This is kind of
00:42:09 --> 00:42:11 core to my day-to-day work. This is what
00:42:11 --> 00:42:13 I've done all through my career. And I
00:42:14 --> 00:42:16 said, where would the ejector go? If you
00:42:16 --> 00:42:18 have a collision like that, some of the
00:42:18 --> 00:42:20 material ejected will be traveling at
00:42:20 --> 00:42:21 less than the escape velocity for all of
00:42:22 --> 00:42:23 the mass that's around. So that material
00:42:23 --> 00:42:26 won't be lost and it would either in the
00:42:26 --> 00:42:27 case of the earth moon collision form a
00:42:27 --> 00:42:29 satellite like the moon or fall back and
00:42:29 --> 00:42:32 contribute to the reacion.
00:42:32 --> 00:42:34 >> Material traveling above the escape
00:42:34 --> 00:42:37 velocity will escape and go into orbit
00:42:37 --> 00:42:39 around the sun. And at that point it is
00:42:39 --> 00:42:41 subject to all of the dynamics that goes
00:42:41 --> 00:42:42 on the grav gravitational interactions
00:42:42 --> 00:42:45 with all the other planets. And I ran
00:42:45 --> 00:42:47 simulations of the ejector to see what
00:42:47 --> 00:42:49 their eventual fates would be where they
00:42:49 --> 00:42:51 would wind up. The majority of the
00:42:51 --> 00:42:52 ejector from the mercury forming
00:42:52 --> 00:42:55 collision hit the sun or was flung from
00:42:55 --> 00:42:57 the solar system never to return as a as
00:42:57 --> 00:42:59 a final fate. That's where it ended up.
00:42:59 --> 00:43:01 But about 2% of the material ejected
00:43:01 --> 00:43:03 from Mercury would have landed on Earth.
00:43:04 --> 00:43:04 >> Oh.
00:43:04 --> 00:43:06 >> So we will have been polluted by the
00:43:06 --> 00:43:08 Mercury forming impact by what you
00:43:08 --> 00:43:11 describe as herian material. If if we
00:43:11 --> 00:43:14 were talking about Venus being venerial
00:43:14 --> 00:43:16 material which then became Venian
00:43:16 --> 00:43:18 material, Mars being Martian, Jupiter
00:43:18 --> 00:43:22 being Jovian for Mercury, Mercurian
00:43:22 --> 00:43:23 never quite worked. So a lot of people
00:43:23 --> 00:43:25 used to call it herian um the
00:43:25 --> 00:43:27 traditional name for but anyway the
00:43:27 --> 00:43:28 material from Mercury about 2% of it
00:43:28 --> 00:43:31 would have rained down on the earth. Now
00:43:31 --> 00:43:34 this ties into the work that I've talked
00:43:34 --> 00:43:36 about before about panspermia as well.
00:43:36 --> 00:43:39 Material ejected from one planet becomes
00:43:39 --> 00:43:41 objects moving freely within the solar
00:43:41 --> 00:43:44 system subject to the gravitational
00:43:44 --> 00:43:47 pinball that goes on. If you have a
00:43:47 --> 00:43:50 collision in orbit around Saturn, if it
00:43:50 --> 00:43:52 is a collision between two of Saturn's
00:43:52 --> 00:43:55 moons, the overwhelmingly vast majority
00:43:55 --> 00:43:57 of ejector will stay bound in the Saturn
00:43:57 --> 00:43:58 system because the moons are both
00:43:58 --> 00:44:00 themselves very deep in Saturn's gravity
00:44:00 --> 00:44:04 while very tightly held. So the vast
00:44:04 --> 00:44:05 majority of ejector from two moons
00:44:05 --> 00:44:07 colliding with each other will be kept
00:44:07 --> 00:44:09 in house.
00:44:09 --> 00:44:12 But that's not all of it. Also some of
00:44:12 --> 00:44:14 that ejector that ejector in the Saturn
00:44:14 --> 00:44:16 system will be like ejector in the solar
00:44:16 --> 00:44:17 system. It'll be bounced around and
00:44:17 --> 00:44:18 moved around by the gravity of the
00:44:18 --> 00:44:21 moons. So a small tiny fraction of it
00:44:21 --> 00:44:22 could eventually be ejected that way as
00:44:22 --> 00:44:25 well. If you have a collision that
00:44:25 --> 00:44:27 instead involves or invokes an object
00:44:27 --> 00:44:29 that is not currently orbiting Saturn
00:44:29 --> 00:44:31 but is a comet or an asteroid passing
00:44:31 --> 00:44:33 through that object itself is moving
00:44:33 --> 00:44:35 faster than the escape velocity of
00:44:35 --> 00:44:36 Saturn. So a significant amount of the
00:44:36 --> 00:44:39 ejector also will be that case you'll
00:44:39 --> 00:44:41 get more material put into orbit around
00:44:41 --> 00:44:43 the sun. Once the material has escaped
00:44:44 --> 00:44:46 from Saturn it is moving on an orbit
00:44:46 --> 00:44:48 that makes it one of the centaurs. And
00:44:48 --> 00:44:49 the centaurs are one of my favorite
00:44:49 --> 00:44:51 populations of objects anyway because
00:44:52 --> 00:44:53 they're what I studied for my PhD and I
00:44:53 --> 00:44:55 did the same dynamic simulations of
00:44:55 --> 00:44:56 them. Where do they come from? Where are
00:44:56 --> 00:44:59 they going? How will they get there? The
00:44:59 --> 00:45:01 centaurs are the parent population of
00:45:01 --> 00:45:03 the short period comets. The centaurs
00:45:03 --> 00:45:08 themselves are daughters, sons, children
00:45:08 --> 00:45:10 of the transep union objects moving
00:45:10 --> 00:45:11 around in the out solar system being
00:45:11 --> 00:45:14 scattered inwards. In my simulations of
00:45:14 --> 00:45:17 the Centaurs, about onethird of Centos,
00:45:17 --> 00:45:19 which is about onethird of those objects
00:45:19 --> 00:45:21 between the orbits of Jupiter and
00:45:21 --> 00:45:22 Neptune that are on unstable orbits,
00:45:22 --> 00:45:24 about onethird of them will eventually
00:45:24 --> 00:45:25 become a Jupiter family comet, will be
00:45:25 --> 00:45:27 flung into the inner solar system,
00:45:27 --> 00:45:29 usually by Jupiter, which means it'll be
00:45:29 --> 00:45:31 put onto an Earth crossing orbit, which
00:45:31 --> 00:45:34 means that if you eject enough material
00:45:34 --> 00:45:37 from the Saturn system,
00:45:37 --> 00:45:38 some of it will hit the Earthh.
00:45:38 --> 00:45:41 >> It'll be a vanishingly small amount. It
00:45:41 --> 00:45:44 is unlikely though that you'll get a
00:45:44 --> 00:45:45 chunk big enough to cause a mass
00:45:45 --> 00:45:49 extinction making it all that far. You
00:45:49 --> 00:45:51 the thing that killed the dinosaurs was
00:45:51 --> 00:45:53 about 10 km across. We think maybe even
00:45:53 --> 00:45:55 a little bit bigger. That's a very very
00:45:55 --> 00:45:58 very big bit of stuff. Now obviously
00:45:58 --> 00:45:59 there's a small chance it could have
00:45:59 --> 00:46:01 been the result of something like that.
00:46:01 --> 00:46:03 There are suggestions that the thing
00:46:03 --> 00:46:04 that killed off the dinosaurs might have
00:46:04 --> 00:46:07 been an asteroid that was probably
00:46:07 --> 00:46:08 produced in a collision in the asteroid
00:46:08 --> 00:46:10 belt and been a member of one of the
00:46:10 --> 00:46:11 collisional families that feed material
00:46:11 --> 00:46:13 to the inner solar system. Others have
00:46:13 --> 00:46:15 suggested it could be a comet.
00:46:15 --> 00:46:17 >> It could potentially have been a
00:46:17 --> 00:46:20 fragment of a a smashed moon like Paul
00:46:20 --> 00:46:22 is suggesting. It could have been a very
00:46:22 --> 00:46:24 ancient fragment of the Mercury
00:46:24 --> 00:46:25 collision that had managed to survive 4
00:46:26 --> 00:46:27 billion years. But that's vanishingly
00:46:27 --> 00:46:29 unlikely because things are rejected on
00:46:29 --> 00:46:31 a much shorter time scale. So there'll
00:46:31 --> 00:46:33 be nothing left effectively. But we
00:46:33 --> 00:46:36 don't know. That's a fundamental thing.
00:46:36 --> 00:46:38 What drives the understanding that the
00:46:38 --> 00:46:41 impact itself was extraterrestrial was
00:46:41 --> 00:46:43 initially the iridium layer that was
00:46:43 --> 00:46:44 found globally. That was kind of a bit
00:46:44 --> 00:46:46 of a smoking gun at the point of the
00:46:46 --> 00:46:48 mass extinction in the fossil record.
00:46:48 --> 00:46:51 They found the crater. You cannot tell
00:46:51 --> 00:46:54 from the crater's size alone what the
00:46:54 --> 00:46:56 nature of the impactor was or the impact
00:46:56 --> 00:46:59 speed. Now for a crater that old it's a
00:46:59 --> 00:47:01 bit bit impossible to do anyway. I've
00:47:01 --> 00:47:03 been really interested and we've never
00:47:03 --> 00:47:05 got round to doing this as research to
00:47:05 --> 00:47:07 talk with people like the create
00:47:07 --> 00:47:09 accounting people to see if there is any
00:47:09 --> 00:47:10 way for bodies like the moon or Mars
00:47:10 --> 00:47:13 where there's much less weathering to
00:47:13 --> 00:47:14 distinguish between a cometary or
00:47:14 --> 00:47:18 asteroidal impact on the basis of
00:47:18 --> 00:47:21 whether the speeds influence on the
00:47:21 --> 00:47:24 kinetic energy of the impact can modify
00:47:24 --> 00:47:26 the crater formation process. probably
00:47:26 --> 00:47:27 it can't because effectively you're
00:47:28 --> 00:47:30 dumping X energy into the surface and
00:47:30 --> 00:47:32 that's what makes the crater but I've
00:47:32 --> 00:47:34 been interested in that but what that
00:47:34 --> 00:47:35 means from the Earth's point of view is
00:47:35 --> 00:47:37 that from the morphology of the crater
00:47:37 --> 00:47:39 from what's left from that impact we
00:47:40 --> 00:47:41 cannot tell what the impact was or how
00:47:41 --> 00:47:43 fast it's traveling had to be faster
00:47:43 --> 00:47:45 than the escape velocity of the earth
00:47:45 --> 00:47:47 because it came from beyond the earth so
00:47:47 --> 00:47:49 the minimum speed is 12 km a second it
00:47:49 --> 00:47:52 is almost guaranteed that it was a solar
00:47:52 --> 00:47:54 system object not an interstellar comet
00:47:54 --> 00:47:56 like comet Atlas Which means that the
00:47:56 --> 00:47:58 maximum speed it could have hit us is 72
00:47:58 --> 00:48:02 km a second which is you get that number
00:48:02 --> 00:48:04 by combining the orbital speed of the
00:48:04 --> 00:48:06 earth which is 30 km a second going
00:48:06 --> 00:48:08 forward with the maximum speed that
00:48:08 --> 00:48:09 something could be traveling at one
00:48:09 --> 00:48:11 astronomical unit at our location and
00:48:12 --> 00:48:13 still be bound to the sun which if you
00:48:13 --> 00:48:16 work out the velocity if you're going at
00:48:16 --> 00:48:19 42 km a second at the location of the
00:48:19 --> 00:48:20 earth's orbit you're right on the
00:48:20 --> 00:48:22 boundary between the solar systems
00:48:22 --> 00:48:24 escape velocity and not so anything
00:48:24 --> 00:48:26 faster than that will escape. Take those
00:48:26 --> 00:48:28 two numbers and say, "Right, you've got
00:48:28 --> 00:48:30 an op object coming head on at the
00:48:30 --> 00:48:32 fastest speed it could have and stay
00:48:32 --> 00:48:35 bound to the solar system. 42 km a
00:48:35 --> 00:48:37 second one way, 30 km a second the other
00:48:37 --> 00:48:40 way gives you 72 km a second. So we know
00:48:40 --> 00:48:43 the velocity with which the signal was
00:48:43 --> 00:48:45 coming in within a factor of six. Most
00:48:45 --> 00:48:46 likely at the lower end because we get
00:48:46 --> 00:48:48 more asteroidal impactors and cometry
00:48:48 --> 00:48:51 ones, but we don't really have much more
00:48:51 --> 00:48:53 than that on the composition of it.
00:48:53 --> 00:48:55 There is a lot of debate over whether it
00:48:55 --> 00:48:58 was cometry, whether it was asteroidal.
00:48:58 --> 00:49:02 An object from from part of one of the
00:49:02 --> 00:49:05 moons of Saturn would be iceer rich and
00:49:05 --> 00:49:07 so it would look like a cometary
00:49:07 --> 00:49:10 impactor. So I'm not sure for an impact
00:49:10 --> 00:49:13 65 million years old whether we would
00:49:13 --> 00:49:15 ever be able to distinguish be between a
00:49:15 --> 00:49:17 fragment of one of the moons of Saturn
00:49:17 --> 00:49:20 as the impactor and a comet as the
00:49:20 --> 00:49:24 impactor. Um, I I just have no idea how
00:49:24 --> 00:49:25 we would do that. What we would probably
00:49:26 --> 00:49:28 be able to do is if we went to a
00:49:28 --> 00:49:30 near-Earth object, whether it's a comet
00:49:30 --> 00:49:33 or an asteroid, and took samples, there
00:49:33 --> 00:49:36 is a potential that then maybe through
00:49:36 --> 00:49:38 isotopic analysis, we could tell that
00:49:38 --> 00:49:41 something was a fragment of a Saturnian
00:49:41 --> 00:49:43 moon, but we need things to compare that
00:49:43 --> 00:49:45 to. That is very much on the very
00:49:45 --> 00:49:47 fringes of what we can do. But we do
00:49:47 --> 00:49:49 that a little bit with some meteorites.
00:49:49 --> 00:49:51 There's a couple of families of
00:49:51 --> 00:49:52 meteorites where we think we know the
00:49:52 --> 00:49:55 parent object. And these meteorites are
00:49:55 --> 00:49:58 compositionally grouped together with
00:49:58 --> 00:49:59 such tightness that they are
00:49:59 --> 00:50:01 distinguishable against the compositions
00:50:01 --> 00:50:03 of everything as a background. It's like
00:50:03 --> 00:50:04 if you measure the composition of
00:50:04 --> 00:50:06 everything and they're points on a wall,
00:50:06 --> 00:50:07 these ones all group together. So they
00:50:08 --> 00:50:10 come from the same parent. But I don't
00:50:10 --> 00:50:13 know how we could
00:50:13 --> 00:50:15 figure out whether it was a fragment of
00:50:15 --> 00:50:19 a Saturnian moon versus a comet. If we
00:50:19 --> 00:50:20 got to the point where we could
00:50:20 --> 00:50:22 distinguish comet versus asteroid, I
00:50:22 --> 00:50:24 think the argument will be it's a
00:50:24 --> 00:50:26 commentary body probably um but we
00:50:26 --> 00:50:28 couldn't tell you whether it's short or
00:50:28 --> 00:50:29 a long period comet. But people will
00:50:29 --> 00:50:31 probably come down on the cometry
00:50:31 --> 00:50:33 explanation rather than the fragment of
00:50:33 --> 00:50:35 a moon explanation because of the Okam's
00:50:35 --> 00:50:37 razor thing. So if you've got two
00:50:38 --> 00:50:39 explanations that are equally good at
00:50:39 --> 00:50:41 explaining the story, take the one
00:50:41 --> 00:50:42 that's simpler. Yeah,
00:50:42 --> 00:50:43 >> that might not be AM's razor, but that's
00:50:43 --> 00:50:45 one of those philosophical constructs
00:50:45 --> 00:50:49 that, you know, it's a more complex and
00:50:49 --> 00:50:51 challenging route to get a fragment of a
00:50:51 --> 00:50:52 Saturnian satellite to kill the
00:50:52 --> 00:50:54 dinosaurs than it is to have it just be
00:50:54 --> 00:50:55 a normal comet.
00:50:55 --> 00:50:58 >> Yeah, fair enough. All right, very good.
00:50:58 --> 00:51:01 Um, thank you, Paul. I think we covered
00:51:01 --> 00:51:04 that uh topic very, very well. And hope
00:51:04 --> 00:51:08 all's well in Queensland. Hey, uh we're
00:51:08 --> 00:51:10 going to take a breath and then uh we'll
00:51:10 --> 00:51:12 quickly go into our final question here
00:51:12 --> 00:51:17 on Space Nuts
00:51:17 --> 00:51:18 and I feel fine.
00:51:18 --> 00:51:20 >> Space Nuts
00:51:20 --> 00:51:23 >> and we're with Professor Jyer today with
00:51:23 --> 00:51:27 Fred away. Uh a Q&A edition. Uh one last
00:51:27 --> 00:51:28 question. Uh we'll have to make it quick
00:51:28 --> 00:51:30 because I think we've really burnt the
00:51:30 --> 00:51:31 clock today. Too much talking about
00:51:31 --> 00:51:33 accents. I think uh I have a question.
00:51:33 --> 00:51:35 Talking. I was just going to say talking
00:51:35 --> 00:51:39 accents. Get Fred to single climb
00:51:39 --> 00:51:41 >> cuz he's from my neck of the woods
00:51:41 --> 00:51:41 originally.
00:51:41 --> 00:51:44 >> Okay. Uh I have a question that might
00:51:44 --> 00:51:47 come across as lame or childish. Yes, it
00:51:47 --> 00:51:49 did. No. No, it didn't. Uh, but I'm
00:51:49 --> 00:51:52 hoping that a professor and a genuine
00:51:52 --> 00:51:57 space nut uh or I'm hoping that asking a
00:51:57 --> 00:51:59 professor and a genuine space nut this
00:51:59 --> 00:52:01 question, it might prompt uh for much
00:52:01 --> 00:52:03 more interesting answer than the average
00:52:03 --> 00:52:06 Joe. What is your favorite planet in our
00:52:06 --> 00:52:08 solar system and why? I wish I could
00:52:08 --> 00:52:10 give you an interesting answer myself. I
00:52:10 --> 00:52:12 do find Jupiter fascinating and Europa.
00:52:12 --> 00:52:15 Okay, you know, I know it's a moon, but
00:52:15 --> 00:52:17 I'm intrigued by what could be under all
00:52:17 --> 00:52:19 that ice. Hopefully, um, we'll find out
00:52:19 --> 00:52:21 in my lifetime. So, yeah, childish
00:52:21 --> 00:52:22 question from a 40-year-old, but
00:52:22 --> 00:52:25 hopefully you can turn it into a more
00:52:25 --> 00:52:27 deep and meaningful answer. That's Dan
00:52:27 --> 00:52:28 from the Gold Coast, also a
00:52:28 --> 00:52:30 Queenslander.
00:52:30 --> 00:52:32 Um, I can go first and be very quick.
00:52:32 --> 00:52:35 I'm fascinated by Mars. I just find the
00:52:35 --> 00:52:37 geography
00:52:37 --> 00:52:40 um outstanding. a smaller planet than
00:52:40 --> 00:52:44 Earth uh with geographic
00:52:44 --> 00:52:46 um highlights that are just
00:52:46 --> 00:52:50 mind-bogglingly huge like the Olympus
00:52:50 --> 00:52:52 Mons for example that that is a volcano
00:52:52 --> 00:52:54 that is it's the biggest in the solar
00:52:54 --> 00:52:58 system and um I think it is so high that
00:52:58 --> 00:53:00 it's actually sticking out of Earth's
00:53:00 --> 00:53:02 out of Mars's atmosphere.
00:53:02 --> 00:53:05 um the the the canyons on Mars and
00:53:05 --> 00:53:07 there's more than one but there's the
00:53:07 --> 00:53:10 the biggest one dwarfs the Grand Canyon
00:53:10 --> 00:53:12 on Earth like I think you can fit the
00:53:12 --> 00:53:13 Grand Canyon in one of one of its
00:53:13 --> 00:53:15 tributaries
00:53:15 --> 00:53:19 um and the list goes on. It is a f a
00:53:19 --> 00:53:20 fascinating planet. I always like to
00:53:20 --> 00:53:22 think of it as um that was God's first
00:53:22 --> 00:53:25 attempt and he stuffed it up and then we
00:53:25 --> 00:53:27 came next.
00:53:27 --> 00:53:30 I I I just uh I just and because we've
00:53:30 --> 00:53:32 we've been able to send so many probes
00:53:32 --> 00:53:36 and and rovers and satellites to Mars,
00:53:36 --> 00:53:39 we've been able to document it, get some
00:53:39 --> 00:53:42 incredible high res pictures of it. It's
00:53:42 --> 00:53:44 I I just find it a a beautiful,
00:53:44 --> 00:53:47 beautiful world. And I mentioned my
00:53:47 --> 00:53:51 sci-fi trilogy um earlier. Um Mars is in
00:53:51 --> 00:53:54 it. I couldn't I couldn't leave it out.
00:53:54 --> 00:53:56 So Mars for me, that was a quick answer.
00:53:56 --> 00:53:58 What's yours? It's got to be in the
00:53:58 --> 00:54:01 solar system. It's a really tough one.
00:54:01 --> 00:54:03 And these kind of questions throw throw
00:54:03 --> 00:54:05 me because the it might be a childish
00:54:05 --> 00:54:06 question because it's the kind of
00:54:06 --> 00:54:09 questions kids ask, but it's entirely a
00:54:09 --> 00:54:11 good question to ask.
00:54:11 --> 00:54:12 >> I'm not as broken by this. While I was
00:54:12 --> 00:54:15 over in Switzerland, um met up with an
00:54:15 --> 00:54:17 ex of mine whose daughter's now 9 or 10
00:54:18 --> 00:54:20 years old and her daughter's doing
00:54:20 --> 00:54:23 English at school and all well and good
00:54:23 --> 00:54:25 and she wanted to practice her English
00:54:25 --> 00:54:27 and was talking to us a bit in English
00:54:27 --> 00:54:28 and kids ask you what's your favorite
00:54:28 --> 00:54:30 color, things like that. She asked me
00:54:30 --> 00:54:32 what my favorite fruit was and I was
00:54:32 --> 00:54:33 just broken cuz I've never really
00:54:34 --> 00:54:36 thought of that and it took me like two
00:54:36 --> 00:54:37 or three minutes to kind of it just put
00:54:37 --> 00:54:40 me into this head jam and I didn't know
00:54:40 --> 00:54:42 an answer. This one's a little bit like
00:54:42 --> 00:54:45 this. And to me, this question is a bit
00:54:45 --> 00:54:47 like asking somebody with a large family
00:54:47 --> 00:54:49 who their favorite child is or asking
00:54:49 --> 00:54:50 someone who their favorite pet is. Now,
00:54:50 --> 00:54:53 I suspect I don't have kids, but I think
00:54:53 --> 00:54:55 the favorite kid varies from time to
00:54:55 --> 00:54:56 time with people who've got parents and
00:54:56 --> 00:54:57 they'd never say they have a favorite,
00:54:57 --> 00:55:00 but there's a little ranking scale. It's
00:55:00 --> 00:55:01 nanny and her extended family in the
00:55:02 --> 00:55:03 discorld series where you could tell how
00:55:03 --> 00:55:04 in favor people were where where the
00:55:04 --> 00:55:06 trinkets that they bought her were in
00:55:06 --> 00:55:08 the house. and you know, heaven for fend
00:55:08 --> 00:55:09 that the little thing you brought back
00:55:09 --> 00:55:10 from holiday ended up on the coffee
00:55:10 --> 00:55:12 table outside in the hallway cuz that
00:55:12 --> 00:55:14 meant you were really in the bad books.
00:55:14 --> 00:55:17 I really struggle to answer questions
00:55:17 --> 00:55:19 like this because they're all
00:55:19 --> 00:55:21 fascinating in different ways. You know,
00:55:21 --> 00:55:23 there are things that we can really get
00:55:23 --> 00:55:25 from them. Mars from an astrobiology
00:55:25 --> 00:55:27 point of view is really the obvious
00:55:27 --> 00:55:28 answer because it's the place that we'll
00:55:28 --> 00:55:31 look for life elsewhere. Jupiter is the
00:55:31 --> 00:55:32 obvious answer because it's been
00:55:32 --> 00:55:34 fundamental to a lot of the research
00:55:34 --> 00:55:35 I've done in terms of the question of
00:55:35 --> 00:55:38 Jupiter friend or foe. It throws a lot
00:55:38 --> 00:55:40 of comments our way. It's the source of
00:55:40 --> 00:55:42 therefore indirectly the cause of many
00:55:42 --> 00:55:43 of the meteor showers and many of the
00:55:44 --> 00:55:46 meteor storms and stuff we see. I they
00:55:46 --> 00:55:49 they would be contenders as would the
00:55:49 --> 00:55:51 others to a certain degree. Neptune
00:55:51 --> 00:55:54 because it's a fabulous insight into how
00:55:54 --> 00:55:56 science can change over time and how we
00:55:56 --> 00:55:58 can discover things without seeing them.
00:55:58 --> 00:56:01 Neptune kind of preaged the exoplanet
00:56:01 --> 00:56:04 era because we discovered Neptune not by
00:56:04 --> 00:56:06 seeing Neptune but by observing Uranus
00:56:06 --> 00:56:08 misbehaving and inferring that Neptune
00:56:08 --> 00:56:10 had to be there to cause that
00:56:10 --> 00:56:11 misbehavior.
00:56:11 --> 00:56:12 >> Although there are some suggestions that
00:56:12 --> 00:56:16 Galileo actually saw Neptune in 1610 and
00:56:16 --> 00:56:17 should be credited as the discoverer but
00:56:18 --> 00:56:20 didn't realize what he had. There's a
00:56:20 --> 00:56:22 background star marked on one of his
00:56:22 --> 00:56:24 drawings I think of the Galilean moons,
00:56:24 --> 00:56:27 the moons of Jupiter where there is no
00:56:27 --> 00:56:28 star and people think it was actually
00:56:28 --> 00:56:29 Neptune.
00:56:29 --> 00:56:31 >> So there are some suggestions Galileo
00:56:31 --> 00:56:32 was a discover of Neptune.
00:56:32 --> 00:56:33 >> Interesting.
00:56:33 --> 00:56:34 >> But for me, Neptune's fascinating
00:56:34 --> 00:56:36 because of that indirect discovery. But
00:56:36 --> 00:56:38 I think for me, if you really push it, I
00:56:38 --> 00:56:40 probably have to say the Earth
00:56:40 --> 00:56:44 >> and a it's the Earth because we is here.
00:56:44 --> 00:56:45 >> But the Earth is a place that's driven
00:56:45 --> 00:56:47 all that complexity in terms of life.
00:56:47 --> 00:56:48 And if you think about Mars being a
00:56:48 --> 00:56:51 complex place, the Earth is even more so
00:56:51 --> 00:56:53 because of the influence of the water
00:56:53 --> 00:56:54 and the atmosphere, the weathering and
00:56:54 --> 00:56:57 the plate tectonics, you know. So, it's
00:56:57 --> 00:56:58 my favorite from the point of view of
00:56:58 --> 00:57:00 it's the only place I can sit around
00:57:00 --> 00:57:01 comfortably in shorts and t-shirt and
00:57:01 --> 00:57:05 chat like this. Also, because it is the
00:57:05 --> 00:57:08 window into the future of our knowledge
00:57:08 --> 00:57:10 of life elsewhere, and it's the cradle
00:57:10 --> 00:57:11 of everything we know and everything
00:57:11 --> 00:57:14 we've experienced. I do have a deep and
00:57:14 --> 00:57:16 abiding love of the earth from that
00:57:16 --> 00:57:17 point of view. But also as a scientist,
00:57:18 --> 00:57:20 the earth is fascinatingly complex
00:57:20 --> 00:57:23 compared to the other planets. It's the
00:57:23 --> 00:57:26 only planet on which we observe plate
00:57:26 --> 00:57:27 tectonics.
00:57:27 --> 00:57:28 >> Yeah.
00:57:28 --> 00:57:30 >> Therefore, it's the only planet whose
00:57:30 --> 00:57:32 surface on longtime scales is that
00:57:32 --> 00:57:34 degree of changeable and mutable. You
00:57:34 --> 00:57:38 know, if I brought you back, say we did
00:57:38 --> 00:57:39 um play with Ren's question from the
00:57:40 --> 00:57:41 start a bit more. We built the
00:57:41 --> 00:57:43 spacecraft from tow zero. We
00:57:43 --> 00:57:46 accelerated. Had a problem. Couldn't
00:57:46 --> 00:57:48 slow down. Eventually managed to fix it.
00:57:48 --> 00:57:49 Came back and we came back in a billion
00:57:49 --> 00:57:51 years time. Mars would still look like
00:57:52 --> 00:57:54 it does today. Unless humanity
00:57:54 --> 00:57:56 terraforms Mars. Mars would look like it
00:57:56 --> 00:57:58 does today. Venus would look like it
00:57:58 --> 00:57:59 does today. All of the planets would
00:57:59 --> 00:58:01 look like they do today. Saturn's rings
00:58:01 --> 00:58:03 may have gone. Peripheral things like
00:58:03 --> 00:58:04 that will have gone, but the Earth would
00:58:04 --> 00:58:05 be unrecognizable.
00:58:06 --> 00:58:07 >> With continental drift, the Earth
00:58:07 --> 00:58:09 wouldn't look like home. And even with
00:58:10 --> 00:58:11 the change in the atmosphere, the earth
00:58:11 --> 00:58:13 may have changed. I've seen some
00:58:13 --> 00:58:14 suggestions that when the earth was
00:58:14 --> 00:58:16 young, the oceans weren't blue, they
00:58:16 --> 00:58:17 were green.
00:58:17 --> 00:58:17 >> Yeah, I've heard that.
00:58:18 --> 00:58:20 >> That's how much the earth has changed.
00:58:20 --> 00:58:21 The mountain ranges will have shifted. I
00:58:21 --> 00:58:23 always find it fascinating to wonder
00:58:23 --> 00:58:25 what is the biggest mountain that the
00:58:25 --> 00:58:27 Earth has ever had. And you Google that,
00:58:27 --> 00:58:29 that's been asked a lot. Nobody's really
00:58:29 --> 00:58:32 got a strong answer because a lot of it
00:58:32 --> 00:58:34 depends on the elasticity of the Earth's
00:58:34 --> 00:58:36 interior and the energy available for
00:58:36 --> 00:58:38 plate tectonics because a limiting
00:58:38 --> 00:58:39 factor on the height of a mountain on
00:58:39 --> 00:58:42 Earth is the sinking that you get as a
00:58:42 --> 00:58:44 result of the mass of the mountain and
00:58:44 --> 00:58:45 the weathering that we get that wears it
00:58:45 --> 00:58:47 away. On Mars, you don't have that with
00:58:47 --> 00:58:50 Olympus Mons. There's no weathering.
00:58:50 --> 00:58:51 >> So, it could just get bigger and bigger
00:58:51 --> 00:58:53 even though it will have a very deep
00:58:53 --> 00:58:55 route. It could keep getting bigger
00:58:55 --> 00:58:56 because there was nothing wearing it
00:58:56 --> 00:58:59 down again. So I think for me because of
00:58:59 --> 00:59:01 the complexity and because it gives me a
00:59:01 --> 00:59:03 place to do my astrophotography and live
00:59:03 --> 00:59:06 my life and all the rest of it, the
00:59:06 --> 00:59:07 earth would have to be the top of the
00:59:07 --> 00:59:09 list. But trying to pick a planet other
00:59:09 --> 00:59:11 than the earth is a bit like trying to
00:59:11 --> 00:59:13 fi pick your favorite pet or your
00:59:13 --> 00:59:14 favorite child. And it might be that you
00:59:14 --> 00:59:16 have one internally, but heaven offend
00:59:16 --> 00:59:18 you tell them.
00:59:18 --> 00:59:20 Very good answer. Very good answer. I
00:59:20 --> 00:59:22 love the question. So uh not childish at
00:59:22 --> 00:59:25 all and appreciate you sending it in.
00:59:25 --> 00:59:26 And if you'd like to send questions into
00:59:26 --> 00:59:29 us at Spacenuts, jump on our website,
00:59:29 --> 00:59:31 spacenuts.io
00:59:31 --> 00:59:34 or spacenutspodcast.com
00:59:34 --> 00:59:36 and click on the ask me anything button
00:59:36 --> 00:59:38 at the top. It's just labeled AMA. And
00:59:38 --> 00:59:39 while you're there, have a look around,
00:59:39 --> 00:59:41 check out the shop, sign up for the
00:59:41 --> 00:59:43 newsletter, um see if you want to become
00:59:43 --> 00:59:45 a supporter. That's optional. And please
00:59:46 --> 00:59:48 leave reviews wherever you listen to us.
00:59:48 --> 00:59:50 And that'll wrap us up for another
00:59:50 --> 00:59:52 episode. Jonty, thank you so much.
00:59:52 --> 00:59:53 >> That's a pleasure. Thank you for having
00:59:53 --> 00:59:55 me. Always a pleasure. Uh, Professor
00:59:55 --> 00:59:58 Jonty her prof professor of astrophysics
00:59:58 --> 00:59:59 at the University of Southern
00:59:59 --> 01:00:02 Queensland. Hey, and uh, Hugh in the
01:00:02 --> 01:00:04 studio um, couldn't be with us today. He
01:00:04 --> 01:00:06 realized that Earth wasn't his favorite
01:00:06 --> 01:00:09 planet, so he left. And from me, Andrew
01:00:09 --> 01:00:11 Dunley, thanks for your company. Catch
01:00:11 --> 01:00:13 you on the next episode of Space Nuts.
01:00:13 --> 01:00:14 Bye-bye.
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