The 3 Body Problem, Aliens & How The World Ends - Dr David Kipping

1. 0:00 – 7:22

   Terence Howard on Joe Rogan

   1. CWChris Williamson0:00

      Dude, I love your YouTube channel. The number of airplane flights that I've been on, delays, sat somewhere where I wish that I wasn't listening to your YouTube channel has been insane. So thank you very much for what you do.

   2. DKDr David Kipping0:11

      Likewise, I've been listening to your podcast for a while, and you have so many great guests, so much wisdom on the channel, as the name suggests. So I really appreciate being on here as well.

   3. CWChris Williamson0:18

      You got tenure. Congratulations.

   4. DKDr David Kipping0:21

      Yeah. That's a big- big deal for me personally, to hit this landmark. Yeah. I don't know if too many people know what it means, though. I think tenure is a- is a term which may be, outside of academia, it's unclear what that really means.

   5. CWChris Williamson0:33

      Yeah. But it's like a- you're allowed to research whatever you want now and no one can tell you no.

   6. DKDr David Kipping0:39

      (laughs) Right. Uh, ultimate freedom.

   7. CWChris Williamson0:41

      Yeah.

   8. DKDr David Kipping0:41

      That's kind of one way to think about it. It's- yeah, it's supposed to be, I think, ideally that it gives you the ability to pursue much more high-risk endeavors. So maybe as a tenured track faculty, which is what I was before, you're kind of living like day to day. Like, you're- each project has to deliver something within the next quarter, the next year, and everything's kind of very short term, which is how a lot of corporations work, of course. But when you get tenure, you get to think about going truly long term for something which is 10, 20 years, for the rest of your career, and that's exciting. I'm- I'm still trying to figure out exactly what I want to do with my tenure, but it's an amazing gift to have.

   9. CWChris Williamson1:17

      Speaking of high-risk, explorative conversations, did you listen to Terrence Howard on Joe Rogan?

   10. DKDr David Kipping1:25

       I did. I was actually listening this morning, I was in the gym and I was listening to Neil deGrasse Tyson's video, which was a response-

   11. CWChris Williamson1:32

       Me too. Me too.

   12. DKDr David Kipping1:32

       ... to it. And the- and I think Neil did a great job in being very respectful and thoughtful and polite, but at the same time, forcefully pushing back, uh, about many of the things which, uh, were questionable in- in this treatise that- that Terrence had come up with.

   13. CWChris Williamson1:50

       What did you make of the conversation with Joe? 'Cause there's been a lot of, uh, I think- it caused a lot of ripples. Uh, a lot of people were very excited, and, you know, it seems like it's upended or some people believe that it was able to upend mathematics, and, you know, there's sort of a narrative, it's personified there, keeping the real information from us, type thing. What did it feel like as someone who kind of lives in the world of maths and- and physics listening to that conversation?

   14. DKDr David Kipping2:15

       Yeah. I- I only saw snippets of the conversation, but I will say that it's not unusual to see a reaction like this. I know it's kind of blown up on social media, and- and in social media world, perhaps it's unusual. But in my world, I receive letters every day coming through my- through my post box with theories and ideas. I get, of course, many, many blind emails, cold emails saying, "Here's my theory of everything. Please check it out. You know, I've proved that Einstein is wrong." This kind of stuff. It's very, very common to, not just myself, but many academics, we are used to this. And I think Neil is in the same boat. I'm sure he gets tons of those kinds of pet theories sent to him as well. And so, you know, they range from, uh, from some of them are just a complete crapshoot, to some of them, there's some serious thought in it. And I think Terrence actually did try to put some thought into it, despite the fact there was many missteps and, uh, misrepresentations of- of other information that- that predates his ideas. However, I think it is true what Neil said, that it is really important that we don't kill that- that idea, that- that love and that passion, because I was that person once. I remember when I was probably 11 years old, I wrote a theory, uh, and I sent it to my- I gave it to my physics teacher at school, and I said to him, "I think I've proven, there's like a new relativity theory that I've proven." And it was something about clocks ticking at different rates to different observers, and it was kind of like a proto-relativity. So I hadn't actually (laughs) I'm not claiming like I, you know, independently invented relativity or anything. But I wasn't aware of relativity, and it just struck me that somebody approaching a clock close to the speed of light would see the rate at which it ticks be very different to someone flying away from the clock. And so does that have some in- interesting implications about time? And so I wrote one of those crazy, not crazy, but, you know, not- not well-informed, let's just say-

   15. CWChris Williamson4:03

       Speculative.

   16. DKDr David Kipping4:04

       ... speculative theories down, 'cause I wasn't crazy, and I don't think Terrence Howard's crazy. And I think you write down these ideas and it gets you impassioned and excited about physics. And part of me is a little bit embarrassed about doing that as a kid. But I also think, uh, whether- whether you're a kid, whether you're an adult, whether you're- whatever stage you're coming at, when you first start diving into this world, it's natural to have lots of ideas and questions and want to put them down into paper and have other people look at them and want to talk about them. So, you know, physics and science is like being in love. Like, when you're in love, you just want to sing it to the world. And I think that's just where he is right now. He's just at that stage where he's like getting really thick and heavy into it and enjoying it. But, uh, hopefully we can direct him towards- (laughs) towards some of the truths along the way as well.

   17. CWChris Williamson4:52

       And peer review, uh, guides, a combination of guides and beats it out of you, and sort of moves you toward what's more accurate?

   18. DKDr David Kipping5:00

       It can do. You know, peer- peer review is not a perfect system. I mean, and I think this is why people like Terrence are gaining traction, because we all recognize that having one or two people who are, you know, so-called experts in that field sway judgment about whether your idea is right or wrong, has its own flaws. There are, you know, political reasons why someone might want to squash your ideas, or simply because, uh, they might not like it because it's so, uh, fundamentally different to everything they're used to. "Hold on, this isn't what I was taught in the textbook. I don't like this, 'cause it's gonna force me to have to re-teach the way I've been taught everything for years and years." So there is- there is resistance to new ideas. And I think, you know, that came up in the podcast with Joe. And that's right, there is definitely resistance to new ideas. However...If you have a great idea and it disseminates to the community, which is, you know, the way it works these days, you can put it on social media, you can put it on an arXiv posting is how scientists typically do this, or on Twitter, or on X. You can put it out there and hopefully if it's a good idea, it will sustain, it will survive that process of not just academic peers, but ma- a much broader peer community looking at it. So peer review, I mean, it- it's kind of obvious that that has to be the way you do it. You have to have lots of people look at an idea, and it's like a meme. If it, if it hits, if it's-

   19. CWChris Williamson6:17

       Mm-hmm.

   20. DKDr David Kipping6:17

       ... if it, if it tracks with people, if there's something in it which, which appeals and see, and, and explains phenomena in a way which we previously couldn't explain, then it's going to survive, and in Darwinian evolution sense, uh, pre- persist. And hopefully the key with science is that we, we're using evidence and in, to, to make that assessment as to whether things are correct or not.

   21. CWChris Williamson6:36

       As the assessment criteria, yeah, obviously the sticky-

   22. DKDr David Kipping6:38

       Yeah, and not, not just, not just an emotional appeal.

   23. CWChris Williamson6:40

       How sexy is this? Yeah. Which is the thing that, you know-

   24. DKDr David Kipping6:42

       Yeah, which is, which has its own aspects. And, and there's certainly scientists are also appeal to that as well. There's definitely like, you know, the string theory or multiverse-

   25. CWChris Williamson6:50

       Sexiness? Sexy scientists?

   26. DKDr David Kipping6:50

       Well, perhaps, perhaps in a physical sense too, but I was really thinking about just the i- the ideas can be attractive and alluring, and I think when people talk about, for example, the multiverse, there's something very alluring about that idea that there could be other versions of you who are more successful and, uh, or maybe less successful, and kind of that imagination kind of runs wild. I think a lot of us get drawn into that idea as well. And so it's hard to sometimes stop yourself and say, "Hold on, uh, I think I'm getting deceived by what I want to be true, rather than what is really true."

2. 7:22 – 12:00

   The Science of Quantum Entanglement

   1. DKDr David Kipping7:22

   2. CWChris Williamson7:22

      A pretty sexy idea that's been floating around, uh, continues to sort of resurface all the time is that quantum entanglement allows for faster-than-light communication. What's the scientist's perspective on that?

   3. DKDr David Kipping7:37

      Yeah, it really doesn't work. It, it's, it seems like it should work when you first hear about the idea. Let me try and just break this down a little bit. So, you can imagine that you have a pair of particles which are what we call quantumly entangled to each other. And what that really means is that their, their state is in a superposition together. So the idea of superpositions in quantum theory is very familiar, whenever you have, uh, a single particle whose spin could be up or spin could be down, for example. It, until you measure it, it really is in a superposition of those two states, we don't know. And then once you measure it, it collapses down and makes, makes a choice, essentially, to one of those, uh, variables. With a pair of particles, if they are created together in a certain set of conditions, you can create them such that they are entangled, which really means that their, their combined sum and combined nature of their, of their state is entangled to one another. So, for example, the total of their spins could be zero. So in that case, one would have to be up and one would have to be down, but you don't know which one is which. So this is very similar to having, like, uh, a box of shoes. So you could have a left shoe and a right shoe, they're in the box, and you, you kind of blindfold yourself and you take one of the shoes, and you give it to your friend. He goes on an airplane, he keeps himself blindfolded, and, you know, you don't feel the shoe, so you don't, you don't break the illusion as to what it really is. But then once you get to the other side, one of you opens the box. And when you open the box, it collapses the uncertainty, you might say. And so the question is can that be used for communication? And the answer is, well, no, because if I open my box and I discover that it's a left-footed shoe, then that instantaneously tells me the other shoe must be right-footed. And not only does it tell me that, but in a quantum world actually does force that state to be right-footed as well. It really is a physical effect that it forces it into that state. But nevertheless, there's no way to use this for communication. Since I can't manip- I can't force my shoe to be left or right. If I could, then we could use it for communication. If I could push it to be not just a 50/50 probability, but rather a 60/40 probability even, just slightly nudge the probabilities, there would be a way to use it for communication. But as long as it's inherently random, which it is from my perspective, when I open that box, it's an inherently random process, all I can ever do is just get a string of, if I had a whole box of these things, many, many boxes, of just left, right, left, right, right, left, it'd just be random sequences. There's no way we can use these shoe boxes (laughs) to send a message to each other.

   4. CWChris Williamson10:04

      And manipulating the one that you have doesn't change the one that your friend has?

   5. DKDr David Kipping10:10

      Well, there is no way to manipulate it. All you can do ... The only manipulation you really have is that you can open the box. You can measure it. That's it. That's the only manipulation you can do. If someone could invent a way to manipulate the quantum state without measuring it, which seems like an oxymoron to me, uh, then, then there would be a path forward for communication. But-

   6. CWChris Williamson10:30

      Because during ... Th- the act of measuring causes it to collapse, and then after that, there is no such thing as changing it, which means-

   7. DKDr David Kipping10:38

      Well, once the cl- once the states have collapsed, they're no longer entangled to each other. So then, so then there's-

   8. CWChris Williamson10:42

      Oh.

   9. DKDr David Kipping10:42

      ... the link has been broken. So once the measurement's been made, that's it, they both collapse into their state, and the entanglement's gone. So it's, it's not persistent-

   10. CWChris Williamson10:50

       Oh, wow.

   11. DKDr David Kipping10:50

       ... past that point.

   12. CWChris Williamson10:51

       Right. That makes so much sense. That, that makes the quantum entanglement communication thing seem quite simple as-

   13. DKDr David Kipping10:57

       Yeah, I mean-

   14. CWChris Williamson10:58

       ... to why it's not gonna work.

   15. DKDr David Kipping10:58

       ... it, it is fairly simple. Obviously y- the way I'm describing it is a little bit simplified, but in a nutshell, that's kind of the basic principle. I obviously have a video if you want to go much deeper that gets in toward the nuts and bolts of how this works, and kind of looks at the superposition states and things, but essentially, that is the problem. And it's a shame because in, you know, I think there's a game, Mass Effect 2, which has a quantum communicator in it. I actually use that, a scene from that in one of my videos about this. And th- I think the, the character comes up to this computer and it says, "You know, I have a quantum entangled state particle, and as long as, you know, there's one back on Earth, and there's one on this ship, we can communicate with this particle." But of course, that doesn't make any sense. The moment you interact with that particle and measure it, the state collapses, and so the, the entanglement's gone. Entanglement is actually a very delicate state of affairs. It's hard to maintain entanglement, and basically any interaction with the real world will collapse it, including, and especially, you trying to measure that thing.

   16. CWChris Williamson11:57

       Wow, that's so interesting.

3. 12:00 – 17:45

   Is the Speed of Light Faster Than Gravity?

   1. CWChris Williamson12:00

      Well, I, I remember reading... This was in college, this must be nearly 20 years ago. I read that, uh, gravity moves quicker than the f- speed of light. Is that true to gravitational waves? If the sun disappeared now, would we start flying off immediately or would it take us four minutes?

   2. DKDr David Kipping12:18

      No, it would take... Well, eight minutes. Yeah, it would-

   3. CWChris Williamson12:19

      Eight minutes.

   4. DKDr David Kipping12:19

      ... take eight minutes. It actually does turn out it... In general relativity it is assumed that it travels at the speed of light, it's kind of built into the theory. And there have been some measurements, um, that have attempted to measure this, or at least constrain it. And although we don't have, like, a super precise measurement like we have for the speed of light where we can, you know, pin it down to fractions of a meter per second, for the spee- for the speed of gravity, it does appear to be at least consistent with the speed of light. But one of the ways we can actually do better with this is, is looking at the, what we call electromagnetic counterparts to gravitational wave sources. So there are these black holes which are smashing into each other and combining out there, and we've been detecting those, hundreds of them now, using a telescope or really an instrument, I should say, called LIGO. It's not really a telescope in the conventional sense, it's just kind of giant laser beams essentially. But using these laser beams we've been able to detect as, as gravitational waves ripple past, they squish and squash the Earth just a fraction of a proton-

   5. CWChris Williamson13:17

      No way.

   6. DKDr David Kipping13:17

      ... in diameter. It's a tiny, tiny disturbance, but these lasers are so sensitive they can tell when they've been squished and squashed by that tiny amount using a technique called interferometry. So we've been able to tell there's these gravitational wave source out there as, as black holes merge, and in some cases we've even seen neutron stars merge. So neutron stars are not black holes, they're kind of like failed black holes if you like. They didn't quite have enough mass to collapse all the way down to a black hole, but... And the sun will also not turn into a neutron star, it's not heavy enough to get into that regime either, but some massive stars will collapse down to a neutron star. These are things which are about the same size as New York City, Manhattan even, and they're almost the same mass as the sun, maybe a little bit heavier, so incredibly dense objects. And these, because they're not black holes, when they collide with each other they shine, they do produce a huge amount of energy. So we have two things ha- it's like a race happening, where you have the gravitational wave racing towards you from that collision, and you also have the, the light that-

   7. CWChris Williamson14:13

      Oh, of course, it is like literally-

   8. DKDr David Kipping14:14

      ... was emitted during that smash.

   9. CWChris Williamson14:14

      ... like a race.

   10. DKDr David Kipping14:15

       Yeah. So we can actually time when those two events arrived, and we can use that to test how similar they are. And for all accounts so far they've been pretty consistent, but it's still fairly early days, we only have a, a handful of neutron stars, most of the events we've detected have been black holes, but we're getting to the point where we should have hundreds of these things coming online in the next few years, so I expect we'll be able to pin that number down really precisely as going forward.

   11. CWChris Williamson14:39

       Would there be anything special, or would it be unbelievably shocking if the speed of gravity was less than the speed of light? Would that cause some oddities?

   12. DKDr David Kipping14:50

       For sure. I mean, it would basically mean general relativity was wrong, so we'd have-

   13. CWChris Williamson14:54

       Ah.

   14. DKDr David Kipping14:54

       ... to, we'd have to go back to the drawing board-

   15. CWChris Williamson14:56

       Okay. Brilliant.

   16. DKDr David Kipping14:56

       ... a little bit with the, with the ideas of general relativity. So I think you'd have to speak to some theorists about the wild ideas about what that could mean, but it might imply some kind of, uh, foam or some kind of resistance to spacetime itself for the propagation of gravitational waves in a way that is not expected in simple general relativity. So it would be a very exciting result. And, you know, it's important to remember that despite scientists, for one aspect not... Being often resistant to new ideas, on the other hand they love new ideas. And so I think if we discovered that, theorists would be very, very excited because it kind of gives theorists at least, and observers, an excuse to do a lot more science, right?

   17. CWChris Williamson15:34

       Mm-hmm.

   18. DKDr David Kipping15:34

       Because now we've got this, this mystery to explain, so we can plan either more observations to try and explain that mystery, or we can come up with lots of ideas and speculations about what might be going on, see how it lines up, hypothesize about what future observations will make. So scientists do actually really enjoy a mystery, and so I think if we discovered that most of us would be celebrating.

   19. CWChris Williamson15:54

       Right, yeah. Lots of work to do, lots of research and grants and new exciting things to focus on.

   20. DKDr David Kipping16:00

       Yeah. I think the most boring outcome is that we understand everything. That's like, that's actually what put me off when I was studying, uh, physics at school. I remember being kind of put off physics 'cause it kind of... The way it's taught at schools feels like everything's been figured out, like here's Newton's laws of gravity, here's the, the atomic structure, here's the electromagnetism, how that works, and it kind of feels like, "Well, what's left to do?" I wish I was born 200, 300 years ago-

   21. CWChris Williamson16:26

       Mm-hmm.

   22. DKDr David Kipping16:27

       ... when it felt like back then all you had to do was throw, you know, some wood in water and point at it and say it floats-

   23. CWChris Williamson16:32

       (laughs)

   24. DKDr David Kipping16:32

       ... and you could get the Nobel Prize or something. (laughs) Now it's so hard, like what's happened?

   25. CWChris Williamson16:37

       (laughs)

   26. DKDr David Kipping16:37

       And, uh, it, it does feel like that, but then that's why I got attracted to astronomy 'cause in astronomy it re- it really is like an, an, an, an, an m- a multitude of things that we can discover out there. The galaxy alone has 100 billion stars in it, and there's 100 billion at least galaxies out there. So, like, there's only 10,000 astronomers on Earth, we are never gonna run out of stars and planets and galaxies to study, there'll be millions each for us. So that was always the appeal for me is that there's just like if I'm gonna choose a subject to study, and I don't want to run out of things to be surprised and amazed about, astronomy has got to be the one.

   27. CWChris Williamson17:16

       Well, you're hopelessly outnumbered, stars to astronomers. It's a...

   28. DKDr David Kipping17:20

       For now, for now. We're gonna, we're gonna try and pull it back. (laughs)

   29. CWChris Williamson17:23

       Yeah, I seem to remember, uh, reading an article about how the number of kangaroos that exist on the planet compared to the population of, like, Czechoslovakia, and it was like that it, it would result in each Czech citizen having to fight 11 kangaroos, and that that was a really important, uh, stat that-

   30. DKDr David Kipping17:41

       (laughs)
4. 17:45 – 23:35

   David’s British Background

   1. CWChris Williamson17:45

   2. DKDr David Kipping17:45

      Yeah.

   3. CWChris Williamson17:45

      ... astronomers. Where did you go to school? What was your academic, uh, comeuppance?

   4. DKDr David Kipping17:49

      So, I grew up in the UK, and people get confused about that 'cause my accent, I think... I've been in the US for a while, and sometimes even people get confused about where I grew up. But I grew up in Warwickshire in the UK, I went to a little school near, i- near Twycross, it was called. Um, and then eventually I went to Cambridge University, and I studied physics there. Well, really, natural sciences was the name of the degree, but primarily I studied physics. They're kind of like a little bit pompous that way, they won't let you have a physics degree. No, this is Cambridge. It has to be called something else. So it was called natural sciences (laughs) . And then once I got that, I decided to go to London and study astronomy for my PhD, and then eventually came stateside during that process. So, I, I really loved being in the UK, I miss the UK quite a lot. Um, but I do feel the direction, especially scientifically, uh, the, you know, with the Brexit and the, the, the reduction in science funding, the state of the economy, it doesn't feel like the future is bright, at least for me, s- sat here in the US. And there's problems in the US for sure as well, but certainly looking at what's going on in the UK, there's nothing about it that's drawing me back in a career perspective. But I, I'm very fond of the UK, I love the people, I love... have so many great friends there, my family is still all there. I love the countryside, and, uh, there's something special about being back in the UK.

   5. CWChris Williamson19:05

      I feel the same. It's, uh, like an odd sort of push and pull where you go somewhere because it's a better environment for the work that you do and there's more opportunity, and then there's sort of this wistful, uh, cultural, uh, like, uh, departure that you make from, uh, from the place that you know so well. So, yeah. I feel you with that.

   6. DKDr David Kipping19:24

      Mm-hmm.

   7. CWChris Williamson19:24

      Uh, just as a side point, totally unrelated. I just got, before we started talking, an email from Dominic Cummings. Remember Dominic Cummings?

   8. DKDr David Kipping19:31

      Oh, yes. Yes.

   9. CWChris Williamson19:32

      So, I'm gonna bring him on just after the results of the general election in July.

   10. DKDr David Kipping19:38

       Okay. Great.

   11. CWChris Williamson19:39

       And, uh, I think that's gonna be a really fascinating insight about exactly what's going on. Not... I, I don't really care that much about politics, but I'm very interested in the social dynamics of what's happening and why people behave the way that they do, and I think that he has some, he has some amazing insights, uh, regardless of what you think about sort of how he contributed to anything. Uh, he just-

   12. DKDr David Kipping19:59

       Yeah.

   13. CWChris Williamson19:59

       ... knows what Whitehall is like from the inside out. So I'll have a-

   14. DKDr David Kipping20:02

       Yeah.

   15. CWChris Williamson20:02

       ... I'll have some interesting, interesting stuff to go through.

   16. DKDr David Kipping20:04

       Look forward to that. Yeah.

   17. CWChris Williamson20:05

       Yeah. Uh, going back to the-

   18. DKDr David Kipping20:06

       It's, it's a crazy world over there. Yeah. I, I think with everything going with the election right now, I know everyone in the UK keeps asking me, everyone on the phone, they're like, "What do you think of what's going on in the election?" I'm like, "I don't know. I'm... My head's pretty exploding with what's going on in November over here right now." So let's... I, I don't know if I can handle all the elections happening in the world right now. It's pretty distracting as a scientist actually, to try and, like, sit down and focus on doing some serious work, and then you open your phone and it's just crazy headline after crazy headline, you know, th- and, uh, yeah, I think I'm starting to think I need to unplug as November approaches.

   19. CWChris Williamson20:38

       Mmm. Yeah. I wonder how many people, smart people, are having their precious mind cycles captured by stuff that is sexy and interesting and newsworthy, but totally unrelated to their primary pursuit. And I wonder how much that's holding back human progress across the world. I would guess an awful lot.

   20. DKDr David Kipping20:59

       Massive, massive. I, I've never felt personally so distracted by what's going on in the world, and I'm trying to be... you know, I feel like there's a responsibility to be a good citizen and be engaged 'cause this is a democracy and this nation and, and the world will be what we make it as participants in it. And so it feels wrong to just stick your head in the sand and ignore what's going on, but at the same time, my effectiveness and my productivity crashes the more I, I open that, you know, New York Times app or CNN or Twitter or X, whatever it is. Like, it just, it's... you're being bombarded with these, these headlines that just take you down these rabbit holes and before you know it, it's 2:00 PM and you haven't done anything yet. So-

   21. CWChris Williamson21:41

       Mmm.

   22. DKDr David Kipping21:42

       ... I think... I'm seeing it with lots of people, I'm seeing it with lots of my colleagues that students and, um, young people especially, I think are really being heavily affected by what is happening, and their studies and their focus is being almost stolen from them because of the state of the world.

   23. CWChris Williamson21:58

       Well, especially for you, being captured by things that's happening on Earth when the entirety of your job occurs outside of Earth.

   24. DKDr David Kipping22:05

       Yeah.

   25. CWChris Williamson22:05

       Like, the only place that you shouldn't be looking really is, like, here. Everything is up there.

   26. DKDr David Kipping22:13

       Yeah. It, it's kind of a, um... you know, we, we do lots of work in looking out in universe, but in a way that's almost like a reflection of us as well. There's... uh, people say this often beautifully about SETI, the Search for Extraterrestrial Intelligence, that the things that we choose to worry about and look for... So for instance, there are ideas that we should look for planets which are undergoing nuclear war because we're on the precipice of that potentially, and so you could make the argument that other civilizations will do this and therefore it's our responsibility and our opportunity to detect them using, you know, neutrinos or using, you know, bright flashes from the s- from the, from the explosions on these other planets. And so that really is a reflection not so much of what aliens are doing, but of our, of ourselves. It's a, it's a inner... it's a mirror of, uh, of us. A dark mirror of our own fears and hopes for the future. And I think that's very much true in SETI, but I think when you look expansively out even beyond searching for aliens, just trying to get a sense as to who we are in the universe is still very much an inward journey as much as it is an outward one of trying to figure out, "What is the point of my life? If the universe is so vast and so big, where do I fit in it? Where do, where do our lives queue into this line?" And so for me, you know, looking for answers out in deep space is as much a process of looking for answers inward as, as beyond.

   27. CWChris Williamson23:34

       Did you

5. 23:35 – 30:32

   Explaining the Three Body Problem

   1. CWChris Williamson23:35

      get to watch The Three-Body Problem?

   2. DKDr David Kipping23:37

      Yeah, I did. And I'd read the couple of... the first couple of books, and I thought the show was really intriguing. Um, it was pretty well done actually, I thought. I like all the actors from the Game o- 'cause it's kind of the Game of Thrones mo- mock, version two or something, right?

   3. CWChris Williamson23:51

      Remake. Yeah, yeah. Yeah.

   4. DKDr David Kipping23:51

      (laughs) Just put into like the modern world or something with aliens. So I kind of enjoy seeing all those actors again doing well and getting jobs 'cause I thought they did a great job with Game of Thrones.And the story, the story was done well. Obviously, the physics is a bit spoofy. I mean, the idea... I think, like, one of my biggest gripes with it was the idea that the nearest star... 'Cause they, they never actually name the star, but they keep saying it's four light years away, so there's only one star that's four light years away, and that's Proxima Centauri. There is a triple star system there, but it's nowhere near compact enough to have this chaos that they have in, in the story, so they've taken some, some, some license there to, artistic license to make things a little bit more interesting. Um, but I think the idea that the nearest star system would have an intelligent civilization on it is a little bit contrived. 'Cause if the nearest one has it, then basically every single star should really have intelligent civilizations on it, and then that just, that just seems very curious, because for the vast majority of Earth's history, four-and-a-half billion years, there was basically no intelligent species on this planet until very, very recently. So, it would seem an enormous coincidence that all the planets, which have completely different ages, some were born, you know, very recently, some were born, uh, billions and billions of years before the sun was, and yet they all just happened to line up so that civilizations just kind of queue up at the same time. So that, that's always a little bit contrived to me, that every single star system is gonna have civilizations on it. But, you know, I can let that go. When I watch, when I watch a show, be it, you know, fantasy or sci-fi, I can, I can let go of those things just to sit down and enjoy it.

   5. CWChris Williamson25:23

      A bit of artistic license.

   6. DKDr David Kipping25:24

      Yeah.

   7. CWChris Williamson25:24

      Can you explain it to me? Can you explain the three-body problem?

   8. DKDr David Kipping25:28

      So, yeah, the physical idea of the three-body problem, it's, essentially it's, it's a chaotic system. So if you have a single particle, it's obviously fairly trivial to predict its path in the future. If you know it's, what direction it's moving and you know its current location, then you should be able to predict at any point in the future where it will be. It will just basically travel along a straight line. However, if you have two particles, it's a little bit more complicated, and they have mass and they're going to gravitationally interact with each other and circle around one another, but it was shown by Newton and many others that this is also a completely determinable system as well. So, if you give me the starting positions of those two particles, and you give me the momenta in which they're moving, then again, we should be able to calculate for a billion years into the future to exact precision where they will be. But this all kind of breaks down when we get to three bodies. So, when you have three, same situation, just three particles, you know their initial positions, you know their initial trajectories. Now, you can predict where they will be, but if you very, very slightly deviate one of those particles, so you just say, "I'm going to shift one of those particles a, a millimeter over to the left," and redo that calculation, you will get a wildly different answer for the final outcome. So this is kind of like the butterfly effect. So if, you know, a butterfly flaps its wings and you think, "Well, what difference does that make?" But if you propagate it over a long enough time, it can have enormous implications, and, you know, people hyp- you know, playfully say it could cause, like, a hurricane, right? The, the flaps of a butterfly. That's maybe a little bit exaggerated, but in this case, certainly a very slight nudge to one of these particles will give a wildly different answer. So whenever you have a system like this, we call it a chaotic system, because it basically means we cannot make predictions that are reliable about their final position in a million years, a billion years from now, because we can never know the position of a planet to absolute precision. There's always going to be some slight uncertainty.

   9. CWChris Williamson27:18

      Mm.

   10. DKDr David Kipping27:18

       And if you nudge it within that uncertainty, you get a very different answer.

   11. CWChris Williamson27:22

       So it's not the same as being random, because there's not randomness, it's still fully determined, but so chaotic and complex that it's unpredictable? Is that a way to say it?

   12. DKDr David Kipping27:34

       Yeah, I think unpredictability is the key word. It's, it's that you can't forecast with any meaningful, accurate prediction where it will be. You can actually make distribution, so you can say, "I'm going to run this simulation a thousand, a million times over and over again and just slightly nudge it around and see what the spread of results are," and then that can kind of help you to, like, place your bets as to where you think is most likely to land, like kind of going to the casino and gambling where you think the ball will land on the roulette table. So you can kind of make that kind of statistical analysis, but you certainly can't make a, a, a good prediction. So even for the solar system this is true, so for the solar system it's been shown that if you go forward about a billion years into the future, Mercury is not necessarily stable. So in about 1% of simulations I think it is, and this was work done by Konstantin Batygin, uh, during his PhD, he showed that about 1% of the time, the solar system will become unstable. So in one billion years. That's before the sun actually will long engulf the Earth. And what tends to happen is I think Mercury, uh, gets ejected from the s- from the solar system altogether, and Earth and Venus swap positions.

   13. CWChris Williamson28:45

       No way.

   14. DKDr David Kipping28:46

       So Earth, Earth becomes the Venus and Venus gets a, gets a chance to cool down and could potentially become habitable, I suppose, if it was far enough away from the star. So it's pretty wild that even the solar system, which we think of as incredibly ordered and structured and, and long-lived, as not just a three-body system but a many-body system, also has instability. So the real question is, for any multi-body system, not whether it's chaotic or not, they're all chaotic, the, the question is how long is that chaos timescale start to creep in? And so for the solar system, the chaos timescale, it's called the Lyapunov number, technically, it's around about, um, you know, five billion years or so, whereas for some solar systems that we look at, the chaos timescale is very, very short, on the order of 100 million years. And so for those we're really looking at them and thinking, "That thing might not even be around here much longer, 'cause it's just, it just seems like it's balanced on a knife edge of instability."

   15. CWChris Williamson29:38

       Dude, that's so cool. Chaos timescale being how long will the current system remain, uh, similar, uh, in terms of what we would expect to see?

   16. DKDr David Kipping29:50

       ... I think it's better to think of it as, as when do your predictions diverge. So, you know, almost like in a, in a multiverse scenario, we're, we're living different lives. If you, you know, like the film Sliding Doors, where you get on the train or don't get on the door, over what time scale do the outcomes diverge from each other?

   17. CWChris Williamson30:03

       Meaningfully. Because presumably-

   18. DKDr David Kipping30:05

       Yes.

   19. CWChris Williamson30:05

       ... there's a 0.00000001%-

   20. DKDr David Kipping30:07

       Right, yeah.

   21. CWChris Williamson30:07

       ... chance that Mercury gets ejected tomorrow.

   22. DKDr David Kipping30:09

       Correct.

   23. CWChris Williamson30:09

       But-

   24. DKDr David Kipping30:09

       Yeah, there's a, there's a definition of, you know, exactly what that means, of how quantitatively large it has to be. But typically, it's of the order of sort of, um, uh, a fr- uh, an exponent number, so that's like a power of about 2.5 in terms of like the semi-major axes, the orbital periods, things like this. If they change by a f- a factor of two or three, then that's a t- that's definitely a very major change to the order of the system.

6. 30:32 – 35:09

   The Stability of the Solar System

   1. DKDr David Kipping30:32

   2. CWChris Williamson30:32

      How is it the case that there's so many bodies in the solar system and yet we're relatively stable, at least maybe for the next half billion to a billion years? Like, why is ... there seems to be so much going on. How is it that orbits get settled into kind of reliably? Why are we not, w- w- why is there not more play in the system?

   3. DKDr David Kipping30:53

      It is kind of a miracle, right? It's a miracle of stability that we should be thankful for, 'cause if it wasn't so, then we wouldn't be here. But on the other hand, perhaps that's the answer right there, that if it wasn't so, we wouldn't be here to talk about it. And it's not a guaranteed situation. So when we look at other exoplanet systems, which we have been cataloging now over the last 20 years, it's actually quite rare that we see a solar system that looks like ours. There's something not necessarily completely unique, but rare about the structure and architecture of our solar system. For example, we, we often see planets in highly elliptical orbits going around their star, which if, in our sp- solar system if you had a planet like that, if Jupiter entered a highly elliptical orbit for whatever reason, it would completely destabilize the rest of the planets. We also have lots of Hot Jupiters. These are Jupiter-sized planets which are orbiting very, very close to the star. And again, in order to get Jupiter, which has to form far out in the star system, to migrate inwards, it's like a bulldozer coming through the planetary system. It just knocks everything else out. Um, but it's possible that the solar system had instabilities. It's thought that at one point in the past, there may have been another planet similar to Uranus and Neptune that we lost. So there could have been what's called the fifth ice, uh, fifth gas giant in the, in the solar system. And the reason why we think this is true is that when you do these simulations and you put the eight planets in and you let them kind of all interact with each other and you speed it up over time, you very often find that Uranus or Neptune get ejected out of the solar system in like half of the simulations.

   4. CWChris Williamson32:24

      Mm.

   5. DKDr David Kipping32:24

      So therefore, it seems odd, you know, how ... If, if Uranus and Neptune are so unstable, why are they so stable when we look at them today? So the explanation for this, and David Nesvorniy, one of my colleagues at the Southwest Research Institute, suggested this. He said, "Look, if you put in an extra planet on the back end of that solar system, it's the one that often gets ejected, and it sacrifices itself to save Neptune and Uranus." And then that all make, and then everything makes sense if you do that. So even though we don't have direct evidence for this fifth giant planet, it kind of neatly explains why the outer solar system seems coherent and stable, because it wasn't always coherent and stable-

   6. CWChris Williamson33:02

      Mm.

   7. DKDr David Kipping33:02

      ... and it's only got that way as a result of basically chucking out the unstable stuff.

   8. CWChris Williamson33:07

      So we don't just have a rare Earth hypothesis, we have a rare solar system hypothesis as well.

   9. DKDr David Kipping33:13

      Yeah. I, I, I think about this a lot. This is one of those thoughts that really bother me as an exoplanet scientist, is understanding how special and unique we are. I'd say it's like the driving question I have as a scientist, is, is our home, is there something special about not just the Earth, but maybe the Earth-moon system, the solar system, even our sun, even our part of the galaxy, maybe even our galaxy itself. Like, where, which aspects of this are special and which aren't? Um, for example, the Sun is not a typical star. Only about 10% of stars in the universe look like the Sun. And amongst those, our sun is unusually quiet. Most stars have lots of flaring and activity, lots of star spots. Our sun is, is curiously very, very stable as well in terms of its luminosity output. So that's also kind of odd. You look at the solar system, we have a gas giant. As far as we can tell, just having one gas giant is kind of unusual. Certainly less than 20% of exoplanet systems have that, possibly as low as 10%. So just having a Jupiter around your star is weird. And Jupiter is thought to be potentially a good thing 'cause it could hoover up all the asteroids, for instance. That's been suggested. Maybe that protects the Earth from getting-

   10. CWChris Williamson34:21

       Well, um-

   11. DKDr David Kipping34:21

       ... bombarded early on in its lifetime.

   12. CWChris Williamson34:22

       ... you, you put something in, uh, in one of your videos. When was it? 2000 and ... When did Jupiter take one for the team recently?

   13. DKDr David Kipping34:30

       The Shoemaker-Levy-

   14. CWChris Williamson34:33

       Yeah.

   15. DKDr David Kipping34:33

       ... comet that hit it? Yeah.

   16. CWChris Williamson34:33

       Big boy.

   17. DKDr David Kipping34:34

       Yeah. That was a huge impa- That, that happened when I was a kid. So yeah, it wasn't when I was a professional astronomer. I think this is when I was like 13 or 14, I think, that was happening, and I remember seeing it in the news and seeing the images. But that was, yeah, that was a situation that obviously happens very often. If it happened in a human lifetime, it's happening probably every few decades or so to a planet like that. So that's not surprising. And if that had hit the Earth, it would have definitely extinguished life on Earth, no, no doubt about it. It was a massive, massive impact. So having, having Jupiter take that (laughs) for the team was, was one that we were pretty grateful for.

   18. CWChris Williamson35:08

       Have we got any idea

7. 35:09 – 41:08

   Likelihood of Life & Intelligence in the Galaxy

   1. CWChris Williamson35:09

      about the odds of life and intelligence?

   2. DKDr David Kipping35:13

      That's something that, that is definitely right up my street. I've been thinking about my whole career, I'd say. Um, you know, it's often said there are two types of astronomers, the ones who want to understand how the universe works, they want to understand the m- the mechanisms, what, you know, what was the Big Bang, how does space time work, and there are astronomers who just want to have this itch: Are we alone? And it's just, it just drives you, and you can't help thinking about it. And I probably fall into that latter category. I find both questions very interesting, but that latter one really bothers me. Um, calculating on odds is very difficult because there's only us that we know of. So you have 100 billion stars potentially, and so a lot of people would say therefore the probability of life somewhere in the galaxy is very high, because if the probability is, say-... 0.1%, then that would mean there was, you know, millions and millions of civilizations out there in the galaxy. Fine, but we don't know that the probability is 0.1%. So there's 10 to the 11, 100 billion stars. Let's say 100 billion potentially Earth-like planets out there. But if the probability of life starting on each one of those Earth-like planets is less than one in 100 billion, then it's just us, that's it. And that's just life. I mean, then you could add on, well, what about multicellular life? What about eukaryotes? What about photosynthesis? What about getting all the way up to intelligence and technology even? Because intelligence and technology are not the same thing. You have intelligent species on Earth which do not have intel- which do not have technology, such as, you know, crows or humpback whales and dolphins and things. So just ha- just being intelligent isn't enough either. We have no idea what th- what the outcome of, of all those steps would be. But what we do know is that life started pretty quickly on the Earth, and that's interesting. So we can look at the time scale, and we can say it happened within about the first maybe 200, 300 million years, there's evidence for life on Earth since th- when the oceans formed. Whereas intelligent life took a lot longer. It took intelligent life, you know, four, four and a half billion years depending on when you st- you make the start date. That's a long time. And the Earth will not be habitable that much longer. I just think this is kind of an amazing fact. The Earth will probably be uninhabitable to complex life in less than a billion years, about 900-

   3. CWChris Williamson37:28

      So-

   4. DKDr David Kipping37:28

      ... million years is the estimate.

   5. CWChris Williamson37:29

      ... if it had, if it had taken only a little bit more, we would have been just about getting to the stage of intelligence just about when we would be uninhabitable?

   6. DKDr David Kipping37:38

      Yeah, yeah. There's a really interesting idea called the hard locks idea that, um, Brandon Carter wrote about. And his idea was, um, it's kind of odd that we have these major evolutionary transitions, such as the development of, uh, combigenesis, which is sex, the development of eukaryote cells, photosynthesis, all these major evolutionary developments. They seem to be kind of uniformly spaced in time from the start date of Earth to the end date of Earth, they seem to be kind of uniformly spaced. And he said, "Look, that's actually similar to trying to pick a lock, a very hard lock." So imagine you had a sequence of doors in front of you, and the lock on average would take, let's say, 100 hours to pick. But I only give you 30 minutes to pick all six, and you've got to get through these six locks to get to the end. Now, the vast majority of people, of course, will not get through the six locks, and they'll all... And we just never hear from them, they never become an intelligent civilization in this picture. But very, very rarely someone will be fortunate enough, just very lucky, that they'll get through those six locks despite the fact the odds are against them. And when you look at the distribution of how long it took them to get through those locks, they end up being uniformly spread in time, even if the locks are grossly different in difficulty. So the first lock could take maybe an hour to break, the next one could be 1,000 hours, the next one could be 10 hours. And if e- as long as e- they could be completely different numbers, as long as they're all, as long as they're all hard, the final distribution is always uniform, which is what we see. So he suggested this is consistent with each of these steps being incredibly unlikely events, and that would naturally explain why they seem to be almost coincidentally evenly spread in time in evolutionary record. Which is obviously-

   7. CWChris Williamson39:24

      So-

   8. DKDr David Kipping39:24

      ... bad news if intelligent life... If that's true, then there's not-

   9. CWChris Williamson39:28

      Yeah, because-

   10. DKDr David Kipping39:28

       ... many people out there.

   11. CWChris Williamson39:29

       ... the, uh, hurdles to get over are all really, really high.

   12. DKDr David Kipping39:33

       Yeah. So I- I'm, I'm receptive to that argument. The only real thing I feel confident saying anything about on this, I've done a paper about this a few years ago, where I said, "Well, let's just... Intelligent life is hard to deal with, but let's look at the early life situation." And despite the fact life did start early when, when we did this full Bayesian analysis of the timing and the chronology of Earth's history, it is a good sign for life starting again if we kind of rerun the clock. If we could go in a time machine, and we did that and what we did for the chaos theory, we kind of push things around a little bit, we just nudge things around, and we rerun the tape, and we see how often would life start again. And the outcome was that about nine out of every 10 simulations we would expect life to start again given that, given that situation. So that's just purely looking at the chronology and how fast life started. But it's not a guaranteed, it's not a guaranteed outcome, so it is possible that you could have planets that do not form life as well. Whereas when it comes to intelligence, we try to do the same thing for intelligence, it actually slightly disfavored intelligence. It said that, you know, e- when you look at the numbers, it looks kind of unlikely that intelligence would happen again, but it was a very marginal result. And so we just... Really what that's telling us, we need more data. Whenever, whenever you come to a point where your statistical significance is kind of weak, as a scientist that's a point to reflect that we need better data. And certainly for intelligent life, and for life (laughs) as well, we need more data. And my analysis was only restricted to running the Earth's tape backwards. I mean, who knows if Earth is common either. Like-

   13. CWChris Williamson41:05

       Mm-hmm. Mm-hmm.

   14. DKDr David Kipping41:05

       ... the Earth might be special out there as well.

8. 41:08 – 54:17

   Planetary Conditions Required for Life

   1. CWChris Williamson41:08

      What are the planetary conditions required for life, as far as we know it?

   2. DKDr David Kipping41:15

      For life as we know it, the basic condition is liquid water. So every single living organism on this planet has to have living water in order to survive. There are some animals and some creatures which can go without water for extended periods of time, but they, they can't go forever without liquid water. So that seems to be a basic requirement. You also need an energy source. All, all life metabolizes, so there has to be some source of energy. For most life on Earth, that essentially comes from the sun. Obviously, we get our food from eating animals and plants, but all of that essentially still derives from the sun if you go far enough back down the food chain. And then there's some things which, like chemotrophs, which get their energy from chemical gradients or from deep down on, you know, n- near to the bottom of the ocean, there are some volcanic vents that could be a source of energy.So you have to have an energy source, you have to have water, and I think a lot of us think that you need some kind of information storage system as well. So for us that's DNA, some life uses RNA, um... Whether there's other versions of that on other planets is an open question and something that's very interesting to explore. RNA seems to be a popular idea that it could be almost a common precursor for life out there that we might find. It's very difficult to form RNA spontaneously, so it doesn't seem like it's easy to make RNA, but somehow it must have got started and once you get it, it's autocatalytic, so it can make more of itself. It does reproduce. But getting that first one is kind of the chicken and egg problem with life, quite literally. And then you probably also want to have some kind of cell structure, something to bind the organism together. It can't just be diffuse and just dilute across the entire ocean, it probably needs some physical structure. So that could be, for instance, like a- a- an oil droplet can actually form almost a natural vessel without having to have a- an organism already around, you can have the- the- the oil do that job for you. It's also been suggested that in clays, uh, they can form these little bubbles as well, if you have like wet clay and air cycling through it, you can form these bubbles and those- those clay bubbles could also be potentially little pockets that form like proto-cells as well. So there's lots of interesting ideas about getting the precursors to life going, but of course that's just life on Earth. It is possible that life elsewhere does not require liquid water, but I think there are very good arguments as to why it probably would. You want some kind of solvent, and there are alternatives that you could imagine, um, such as, you know, kind of alcohols for instance, but in- in general it's difficult to argue that water is both extremely common in the universe, it's one of the most abundant things out there, we see it in many, many planetary atmospheres that we've been studying over the last couple of decades, so we know this stuff is all over the place, it's just hydrogen and oxygen, two of the most obvious and common things in the universe, and it has so many advantages for life. So if you want to have liquid water as your- as your basic requirement, then that all comes down to the surface temperature or the subsurface temperature of the object, you want to have it in that- in that temperature range where it- it's not too cold so it's not freezing to ice and not too hot that it's boiling to steam.

   3. CWChris Williamson44:24

      Why do you need the lubricant?

   4. DKDr David Kipping44:27

      The solvent?

   5. CWChris Williamson44:28

      Solvent.

   6. DKDr David Kipping44:30

      Yeah. So you need the solvent to- to- to- to basically carry nutrients around the organism. If you have a- a completely solid object, um, it's difficult to imagine how it would transfer energy from different organelles and different components of the cell, so a solvent is just useful for- for- for keeping... I mean, I'm not a biologist, but my understanding is it's just, it's just to keep- keep a- a way of moving stuff around inside the cell.

   7. CWChris Williamson44:56

      What else about the planet, stuff like the magnetosphere and plate tectonics and a big moon and stuff like that, what else is sort of rare about where we are?

   8. DKDr David Kipping45:06

      I mean, possibly part of the galaxy could be rare as well. People have suggested that where we live in the galaxy may be itself special. We live in a- in a spiral arm, and we live, you know, sort of like halfway to two thirds of the way out from the- from the center...

   9. CWChris Williamson45:21

      In the suburbs.

   10. DKDr David Kipping45:21

       ...of the galaxy to its edge. Yeah, so the suburban district. And we certainly think that if you were too close to the galactic center, that would be bad. As you get closer and closer towards the galactic core, the density of stars increases, there's more and more stars, which means the spacing between stars decreases. Now, that's problematic because you can have exposure to supernovae and gamma ray bursts, which can be essentially life-extinguishing events. So if you get too close, that's a problem. We also did some work in my team with Moyra McTier where we showed that actually the instability we talked about earlier, the three-body problem type effect, also gets worse as you get closer in, because stars themselves often, not collide with each other, but come very close to each other, and when that happens, the gravity of a nearby star can actually rip off and destabilize the planets around your- that you're trying to form. So this is bad, and we think that, you know, certainly once you get within that inner core, you actually lose the majority of your planets this way. This is why I always get a little bit bo- sometimes you'll hear astronomers say, uh, this is a pet peeve I have with my colleagues, that locally we know this is true, nearby to the star, that about, um, let's say 10% of sun-like stars have planets of similar kind of size to the Earth. Not necessarily habitable planets, but similar size to the Earth. Therefore, there are 100 billion stars, therefore there's a billion of those, uh, 10 billion of those in the entire galaxy. Now the problem with that is that we just don't know that we can extrapolate what happens locally in our neck of the woods to the entire galaxy, and especially to that galactic core. It seems very unlikely that the- that in a region... You know, unlike Star Wars, in Star Wars that inner region is where, like, all the activity is going on, everyone wants to live in Coruscant, which is like right at the center of the galaxy. In the real world you do not want to live in the center of the galaxy, that's actually a hell hole place to be living. So I don't think, um, we can generalize these numbers elsewhere, and so when you look out to the outer nec- the suburbs of where we live, there are some reasons why it seems useful, we're- we're far enough away from all that behavior, but we're in a region that's dense enough to be forming stars and dense enough to be forming planets, the metallicity gradient's good. Um, we also happen to move around the galaxy, our orbit around the galaxy is comparable to the speed at which the galactic arms themselves rotate round, and so people have-

   11. CWChris Williamson47:43

       So we're not crossing streams and other, uh, lanes of traffic.

   12. DKDr David Kipping47:47

       Right, exactly. So we don't get these co- these... The spiral arms are basically compression waves of, of gas that are, that are moving through the galaxy. And those compression waves, as they push through, they ge- they lead to a star formation increases. So you have this compression wave, suddenly you get more and more stars being born. And that's generally hazardous to have lots of stars being born, because that means you're going to have some stars which are going to go supernovae. Uh, it's not common, you know, that one in a thousand stars will go supernovae, but if you have a star forming surge, a few of them will, and that's going to be bad if you live in that neck of the neighborhood. So it's like having a swarm of, um, I don't know, like migrants or something swarming through your neighborhood (laughs) -

   13. CWChris Williamson48:24

       (laughs)

   14. DKDr David Kipping48:24

       ... and some of them just explode randomly as they come through or something. You don't really want that. You'd rather be in a place where it, it, there's no visitors and it's a fairly stable place environment. And that seems to be kind of the p- the neck of the woods that we live in. So, in that sense, uh, it may be fortuitous that we live where we are, but this is an open question. I don't think we really established this, but we have some ideas as to why it might be so, but ultimately this is something we hope to test. If we can detect planets right down the center of the galaxy, that would disprove what I'm saying.

   15. CWChris Williamson48:56

       Mm.

   16. DKDr David Kipping48:56

       And prove that actually planets can form in these bizarre places, uh, which would be, again, interesting to discover. Or maybe we'll even discover that there's Earth-like planets in that region and life in that region, which would again upend a lot of what I'm saying. So, it's a testable theory, but it is the only idea we've got right now prior to have any data that there's... it does seem like there's some advantages to being where we are in the galaxy.

   17. CWChris Williamson49:19

       Rare Earth, rare solar system, rare suburb. It's so interesting to, uh, think about that number of this is how many billion stars there are and this is how many planets we think are on average around each star, therefore if you run the numbers forward... but what it doesn't account for is that not all star localities are created equal. And presumably as you get closer toward the center of the galaxy, that accounts for a very large number of the number of stars, but at a much lower, um, appropriateness. The, the, the, uh, environment within which those planets inhabit isn't sufficiently stable and long-lasting to actually allow-

   18. DKDr David Kipping49:56

       Yeah.

   19. CWChris Williamson49:56

       ... life. Yeah, that's so cool.

   20. DKDr David Kipping49:59

       Yeah, I mean, one of the str- one of the strange things, not just location but star type, is the most common type of star in the universe is a red dwarf. So 75% of all stars are red dwarfs. And it... immediately you might think, "Well, how come we don't live around one if they're so common?" But it gets even worse than that because as far as we can tell, they seem to have more Earth-sized planets around them than Sun-like stars do. And yet more, we know that they live for far, far longer. So the sun, as we talked about earlier, will eventually burn out and die. Uh, it'll probably take another 5 billion years before it turns into a giant. But even within a billion years from now, it will become hot enough that it will make the Earth uninhabitable. So this is climate change forced from the sun over, over a billion-year timescales. That would just basically... I mean, there's no way for us to adapt to that and we will die. Um, however, these, these red dwarfs, it's like everything happens in slow motion for a red dwarf. So their lives, they're, they're extended to trillions of years. Because they're so small, it takes them a lot longer, they're much less efficient at burning that nuclear fuel in their center. And so that means that if you lived around a red dwarf, you could have a civilization which lasts far, far, far longer than we ever will. And so all of this kind of is intriguing. You know, you have... there's more of them, they have more Earths and they, and they last for far longer. So they seem to have everything going for them, and yet we don't live around one. And that has also kind of bothered me in the past. And I call this the red sky paradox. Like, why don't we have a red star in our sky rather than a yellow star in our sky? And one possible resolution is, is that there is something wrong with red dwarfs that we don't yet understand. Maybe the radiation they spew out is just hazardous to forming life in the first place. They have these very prolonged... I say they do everything in slow motion, that includes their adolescence. So the sun went through i- its adolescence pretty quick in order of like 10 million years, it kind of settled down, it chilled out, it stopped spewing flares out all the time. And it became-

   21. CWChris Williamson51:55

       What happens during adolescence?

   22. DKDr David Kipping51:57

       It's just a very active star. So it's very unstable. It's, it's very volatile. Its luminosity is changing dramatically. It's spewing out high-energy radiation. It is not a nice place to be living during that time. For red dwarfs, that, that adolescence extends for a billion years in some cases. So the, the problem with that is that it can actually eradicate the planets of their water. So let's say the Earth happened to be a water-rich world born around a red dwarf, but then it's being bombarded with this high-energy radiation. It can actually remove the atmosphere completely off the planet, they're so powerful, these events. When you remove the atmosphere, the water then just escapes. It boils off, it forms maybe clouds at a high, at a high altitude, but then the ultraviolet radiation, which these stars also produce, splits water up into hydrogen and oxygen, so it's like fission of the, of the molecule into hydrogen and oxygen, and the hydrogen will escape into deep space. So an Earth-like planet does not have enough gravity to hold onto hydrogen. If you let out hydrogen in the air into a balloon or something, um, minus the weight of the, of the film itself of the balloon, the hydrogen will just float off into deep space and, and not come back. The Earth does not have enough gravity to hold onto it. So once you lose your hydrogen, you've now just got oxygen by itself. You can't make water with just oxygen. And so the planet loses all of its, its water this way. Um, this is thought to have happened to Venus, actually, in its past. And so this is, um... which is a ve- which is a very dry planet, and we can see that. So this is potentially an explanation as to why, despite the fact red dwarfs are everywhere, they may not be as hospitable as we hope. But perhaps civilizations go there eventually. They might be like the retirement homes, like the Florida of the universe.

   23. CWChris Williamson53:37

       (laughs)

   24. DKDr David Kipping53:37

       Because I think a civilization like us would recognize that there's something here for our future, right? Even though there's no water, maybe we could bring water with us. We could have a huge...... resettlement program. We eventually have huge ships, and we can move over there and bring everything we need. And these stars will be energy sources, stable energy sources for the future trillion years of the rest of the universe. When all the other stars go out, it will just be the red dwarfs left shining. And so it seems obvious that that's where civilizations would be drawn to one day live.

   25. CWChris Williamson54:09

       It's a reliable retirement home, reliable long-term goods, stable property prices throughout.

9. 54:17 – 1:00:17

   Can We Prolong & Control Stars

   1. DKDr David Kipping54:17

      Yeah.

   2. CWChris Williamson54:17

      I've seen, uh, Sunshine. I've seen that movie. How much truth is there in what we can do to stars to prolong them, to control them?

   3. DKDr David Kipping54:27

      Yeah. Uh, we- we actually have an idea on my team. We- we've been working on some of these ideas. If... One immediate threat to... in our solar system is, of course, the sun. So the sun is evolving, which means as it's- as it's maturing, it's becoming more luminous over time. When the sun... When the Earth was first born, the sun was about 20% to 30% less luminous than it is today, so that's a, that's a big drop-off, 30% less luminous over four billion years. So if you go, like, another billion years into the future, that's another sort of 10% increase in luminosity, even a bit more than that, and- and then that will wreak havoc to the climate at this point. So you have to do something. One option that one of my colleagues suggested, Greg Laughlin, was to try and push the Earth back into a wider orbit. So what you could do is you could actually hurl an asteroid directly just off center of the Earth, and as it hurls towards, i- it'll swing around. It will do like a s- a gravitational slingshot around the Earth, and it will fling off in the other direction. But every time that you have one of these gravitation interactions, if it does a slingshot, it basically steals a bit of speed, and it will steal that speed and go off faster than it was before. And that means the Earth will change speed, or lose speed. So you can actually modify the orbit of the Earth by having these interactions. So in this case, we'd actually want to increase the Earth's angular momentum, want to increase its speed, and as you do so, it push it out into a wider orbit. So you'd have to throw thousands and thou- millions of asteroids at the Earth to do this.

   4. CWChris Williamson55:54

      (laughs)

   5. DKDr David Kipping55:54

      And every time, you'd have to do it very close, but not just too close. So... (laughs)

   6. CWChris Williamson55:58

      That would... That is a high-risk strategy. It seems like a very high-risk strategy.

   7. DKDr David Kipping56:01

      It's a high-risk strategy (laughs) for an advanced civilization that really knows what they're doing.

   8. CWChris Williamson56:06

      Mm-hmm.

   9. DKDr David Kipping56:06

      But that's where you could move the Earth back at the r- just the right rate to keep the temperature the same. I guess you could do this for climate change as well, uh, in the near term, but I wouldn't recommend it. I think there's probably safer solutions. Um, the other solution, there's, I think, uh, more feasible, uh, or at least less risky for this, is actually to remove mass off the sun. But maybe this is a bit more sci-fi, uh, even more sci-fi than throwing asteroids at the Earth. You could actually, you know, have some kind of s- way, you know, like, you know, most simply like a ram scoop or something off the surface of the sun, but you can actually probably do it with lasers as well. You can actually excite certain modes on the surface of the sun and- and get material to be ejected out this way. If you- if you make the sun lose mass, that reduces its gravitational pressure in the center. And so the- the core of the sun is where all the energy's produced, and it's- it's like a thermostat. The greater the gravitational pressure from the outside squeezing down on that core, the hotter it gets. So if we take some mass off the top, it'll reduce the pressure, and the oven will cool down a little bit.

   10. CWChris Williamson57:07

       Hmm.

   11. DKDr David Kipping57:07

       And so we can actually reduce the output of the sun.

   12. CWChris Williamson57:08

       Would that not cause it to expand if it's got less gravity?

   13. DKDr David Kipping57:12

       It would... It could cause it to slightly change in radius, but it would, it would not be a dramatic effect. So when we- when we're modifying the- the radii of these stars, it would actually end up probably overall, um, net decreasing the radius of the sun, because as you cool down the s- the core of the sun, there's less, um, outward radiation pressure. So that radiation pressure is bas-... If- if that wasn't there, the sun would collapse into a black hole. The sun wants to collapse into a black, or- or to a very small object, maybe not a black hole 'cause of electron degeneracy pressure, but it wants to collapse all the way down. The only thing stopping it from collapsing down is radiation pressure, like energy spewing out in all directions and pushing back against that, against that force. So if we reduce the power in the oven, we make that core less powerful, the- the radiation pressure will decrease, and it will actually net shrink very slightly. So actually, that's why if you look at stars with lower masses, they tend to have smaller radii. They don't- they don't actually get bigger as a result of the- of the lower gravity-

   14. CWChris Williamson58:10

       Hmm.

   15. DKDr David Kipping58:10

       ...which you might think of. So overall, this would slightly decrease the s- the radius of the sun, and the net effect would be to decrease the luminosity. So we calculated a rate of doing this, and it turns out to be... I'm trying to remember the number, but it was about something like a- a one asteroid's worth. Like, Vesta is, like, one of the largest asteroids. It's one asteroid's worth of material off the sun every year. So not very much. That's how much you have to remove off the sun to basically keep it cooling down gradually over the next billion years such that it basically doesn't change temperature. It'll basically stay exactly the same luminosity as it is today. So we did this calculation in my team, and we think it's an intriguing idea, and we think that if somebody was ever gonna move to another star and potentially colonize it for a trillion years, this would be an obvious thing that they would do. And there are actually signatures that we could look for potentially to detect this. So we call this star lifting. Star lifting is lifting material off the star.

   16. CWChris Williamson59:06

       I was- I was thinking about, uh, s- solar landscaping, that, like, a solar landscaper would be a- a future job.

   17. DKDr David Kipping59:12

       Yeah, that's like a... Solar gardening almost. Yeah.

   18. CWChris Williamson59:14

       Yeah. Correct.

   19. DKDr David Kipping59:15

       And then another idea was that, uh, my- my student had this idea that, you know, you could also use this in the neighborhood. So we talked about supernovae being potentially dangerous. Like, Betelgeuse is nearby, and people are worried about Betelgeuse one day going supernovae and potentially... Or, you know, it's too far away to actually really affect us to be honest, but you could have a- a star like this nearby. We could potentially, or a civilization more advanced than us could potentially fly there, do this mass removal process almost as a pruning technique. Right? So this star is kinda like a weed in your garden that you... like a pest that you wanna get rid of. And so by stripping mass off the top, you could, you could remove that threat.... and de-chlor it and mean that your neighborhood is safe again. So, it's really fun to imagine this is all what physics allows, right? There's nothing, there's nothing about the laws of physics which prevent somebody from doing any of this. And so if the laws of physics allow it and there's a good motivation for why a civilization might want to do it, then it's interesting to ask whether somebody is actually trying this right now.

   20. CWChris Williamson1:00:15

       Mm. Given the

10. 1:00:17 – 1:08:08

    Is an Underwater Civilisation Possible?

    1. CWChris Williamson1:00:17

       requirement for water that's needed for life in any form, at least as far as we know it, uh, what is the likelihood of underwater civilizations? And if you have an underwater civilization, I seem to remember learning that there's a few restrictions that those kinds of species would have. Like they can't smelt, uh, iron-

    2. DKDr David Kipping1:00:41

       Mm-hmm.

    3. CWChris Williamson1:00:41

       ... and, and, and materials that they would be able to use to build things in the same way to be able to go to other planets. Is that something you've considered?

    4. DKDr David Kipping1:00:49

       Yeah. I mean, it... This is super in- intriguing. I've... Also, one of the most interesting aspects of this is the communication aspect of, of dolphins and whales as our, as our sea intelligent companions that live in the ocean. And for years and years we've been trying to just communicate with them, right? If we want to communicate with an alien civilization, we should at least be able to communicate with dolphins and whales and have a conversation with them but we haven't really succeeded very well at that, although there has recently been breakthroughs in this. There was a, a wonderful, uh, podcast on The Daily, a daily podcast The New York Times does, that talked about some recent breakthroughs in this area. So there are, there are some advances happening, um, but in terms of a whale or a dolphin or anything analogous to that ever becoming a civilization, it does seem like there's obvious hurdles. My colleague, Adam Frank, has been thinking about this a little bit harder than I have, and he pointed out that oxygen is not just, um, a problem in the ocean but it's a... It could be a problem in the atmosphere as well. You could be on an exoplanet that has no oxygen but you could still be a, an, you know, creature with thumbs and opposable thumbs and hands and things and a, and a smart brain that you might have the idea of developing technology. But similarly, you wouldn't be able to really do any industry if you couldn't burn, if you had... if you didn't have access to combustion, that seems to prohibit a huge range of technologies that were foundational to us getting started. And then people often say this about fossil fuels as well, like fossil fuels are clearly a, a poison to our atmosphere, but had they had not been on our planet at all, it's questionable whether we would've got to a point where we'd even be developing solar panels, right? Because that requires some pretty advanced technology compared to Stone Age tools. You can't go from Stone Age tools to solar panels, you need, you need something in between to bridge that-

    5. CWChris Williamson1:02:37

       Some steps in between.

    6. DKDr David Kipping1:02:38

       ... and, and combustion was certainly a pivotal filling in step for us in our own development. So we're getting a little bit speculative as to whether other civilizations could use other things. I think, uh, Adam Frank has been interested in, in alternatives to oxygen for combustion, I think he talks about hydrofluoride as a possible alternative but that's a very toxic, uh, uh, molecule and so it's unclear if anything could actually survive (laughs) and not be intoxicated by having such a poisonous fume for its, for its one combustion thing. And also that doesn't just combust but it combusts way, uh, harsher than oxygen does. So i- it would really explode basically every time you try to use it, so it'd be very difficult maybe to imagine combustion. So similarly, it does seem like having an oxygen-rich atmosphere could be a requirement to potentially developing a technological civilization. But subsurface intelligences and subsurface life more broadly is one of the most interesting things we can do in the near term to look for because we have Europa and we have Enceladus, these moons in our solar system, which almost certainly have liquid water beneath their icy crusts, and we know we can visit them and we know we could think of ways of getting down to that surface and probing and looking for life in them. It's gonna be very difficult to do so but I think the investment is worth it because we could answer this most profound question as to whether life started in a completely different environment to that of the Earth. I think if we found that there, it would resolve the question I brought about earlier as to how often does life start in general. If there's two instantiations of it in the same solar system but under completely different independent circumstances, that essentially proves that life is easy and life-

    7. CWChris Williamson1:04:26

       Mm.

    8. DKDr David Kipping1:04:27

       ... could therefore start everywhere. So having that second data point will be incredibly important for us in our understanding of life in the universe, even if it's not intelligent. I doubt we're gonna find a... you know, the city of Atlantis on the bottom of (laughs) Europa.

    9. CWChris Williamson1:04:41

       Some very cold dolphins.

    10. DKDr David Kipping1:04:42

        But I do imagine... Yeah, we might, we might find, who knows, we might have Europan sushi in a few centuries and the billionaires would be shipping over some Europan sushi and selling that at a, at a premium, I'm sure. But, uh, it's, uh, it's, it's a possibility that I think is to be taken very seriously that there could be life in our own solar system. And for me, that is the most likely place we're gonna find it beyond the Earth.

    11. CWChris Williamson1:05:04

        I suppose the only... or one of the potential pushbacks there would be w- what if there was some sort of cross-pollination? How do you know that we're in the same solar system, something hit us, there was something carried on that which seeded this other moon or, or, or some other-

    12. DKDr David Kipping1:05:22

        Yeah.

    13. CWChris Williamson1:05:22

        ... area of the solar system with the same, uh, original sort of genesis of this?

    14. DKDr David Kipping1:05:26

        Yeah. That's a great question and that's, that's an idea called panspermia. So panspermia is the idea that life can transfer between planets, between moons, and spread out between... within a solar system but potentially even beyond into other solar systems as well. So the nice thing about Europa and Enceladus is that they're pretty much sealed behind this prison of this thick ice sheet, which is at least a kilometer, probably several kilometers thick for both of those objects and so it's very difficult to imagine. Let's say...... a rock got knocked off the Earth in a- in a- in an impact, and on that rock was a tardigrade, or a whole bunch of them, a whole bunch of extremophiles clinging on for dear life, and they somehow survived the journey of space, which I think is actually feasible. They survived the impact, but even so they- un- unless that impact is- is extremely massive, it's not going to crack all the way through many kilometers of ice and penetrate through into that ocean water. So I think the- the chall- and also, not only this, but it's also, it's further out in the solar system, so you're going from, imagine like a- a- a well, you know that there's coin drops, that you throw a coin, it circles down, it circles down, it circles down, it circles down. Now you can have two coins hit each other fairly deep down in the well, that's the Earth. The Earth is pretty deep down in the gravitational well. It's pretty close to the sun. Jupiter's pretty far out, it's 5.2 further times out than the Earth is from the sun. And that's where the nearest one of these moons is, Europa. So you have to have a collision that is impactful enough that that rock can then circle all the way back up five times higher-

    15. CWChris Williamson1:06:58

        Mm. Mm.

    16. DKDr David Kipping1:06:59

        ... and then still have enough energy to strike Europa and break through the ice. It's not impossible, I don't think, but it- it would be pretty unlikely that you would- you would have the circumstances to create something like this. For Mars, for Venus, and the Earth, there we can imagine interchange of material much more readily, and it is intriguing to ask maybe life started on Venus or maybe life started on Mars and moved over to the Earth and- and there's some transfer between us. But I think Europa and Enceladus, they're- they're almost like sealed boxes.

    17. CWChris Williamson1:07:29

        Yeah. That's exactly what I had in my head.

    18. DKDr David Kipping1:07:30

        But then- but then that does raise the question of wha- we might break that seal, right? 'Cause if we deliberately drill down into it, we are going to int- uh, whether we want to or not, some extremophile's going to cling onto the side of that spaceship. You can't- it's basically impossible to completely clean the spacecraft.

    19. CWChris Williamson1:07:44

        Sterilize your- your spaceship out in space.

    20. DKDr David Kipping1:07:47

        Yeah.

    21. CWChris Williamson1:07:48

        Yeah.

    22. DKDr David Kipping1:07:48

        It- there- there's always something. And then it's going to penetrate into that ocean and potentially be a source of contaminant. So, you know, you get that one chance of doing the experiment correctly, and if you screw it up, you've- you've potentially introduced an entire new biosphere that could be fairly dangerous, in fact, to an existing biosphere there.

11. 1:08:08 – 1:17:20

    Origin of the Moon

    1. CWChris Williamson1:08:08

       Talking about large impacts, can we talk about the importance of the moon, and its creation, and stuff?

    2. DKDr David Kipping1:08:14

       Yeah. The mo- the moon's a puzzle that we still wonder about today, despite the fact it seems like it's a- a sealed story. We think the moon formed from a huge impact. It's thought that there was a Mars-sized planet which smashed into the proto-Earth billions of years ago, for, uh, just after the solar system formed. So the Earth would've been actually been larger than it had this impact not had occurred. It would've been maybe 50% more massive than it is today, maybe twice as massive. And this impactor came along, smashed into the Earth, it knocked off a huge amount of material, and it's thought that that impactor, which we normally give it the name Theia, would've been almost completely obliterated in this, and vaporized in this- in this collision. And then some chunk of the Earth was knocked off, and that chunk of the Earth is ultimately what formed the moon or maybe even multiple moons that then coalesced later into a single moon. So there's- there's a huge amount of interest about why- why you might come up with this speculative idea, and- and still people are challenging this idea. The thing we know for sure is that the- the moon rocks that were collected by the Apolo- Apollo astronauts have almost the exact same isotropic ratio of oxygen, 18 to oxygen 17 I think it is, as Earth rocks do. And this is thought to be a fingerprint that the rocks formed in the exact same place around the sun. We look at rocks from Mars, we look at rocks from Venus, these are basically meteorites we've collected that land on- on the Earth, they have distinct isotropic ratios. But the moon and the Earth have exactly the same, so that tells us that they formed from the same inherent clump of material. That's challenging with this impactor. With the impactor, if this thing really did have its own unique origin, this impactor, Theia, why didn't it contaminate that then and have its own distinct signature that gets mixed in? So that has been a challenge. One idea that has been suggested to counteract this is called synestia. I think I'm pronouncing that right, synestia. And that's when the impact happened, it was so, uh, extreme that it formed basically one giant donut-shaped planet for a while (laughs) . So the Earth and the moon would've smashed together, formed basically a ball of lava, essentially, that was shaped like a- almost a donut in space, spinning very rapidly because of all the angular momentum from the impact, and then gradually have peeled off and formed a moon and the Earth separately from this giant impact. The reason why this is attractive because it allows for this material to mix in th- thoroughly. So- so this impactor, whatever it was, Theia and the Earth completely mix into one single object, and then it separates out into the Earth and the moon separately. That seems to, uh, explain some of the mysteries, but not everybody accepts that idea, and there's still a lot of controversy about the moon. Like, the moon's far side has a very different appearance and thickness to the near side. If you've ever seen a picture of the far side of the moon, it looks radically different to the near side. The near side has these maria, these beautiful lava flows that happened millions of- billions of years ago that kind of smooth out, and then it has these more cratered, uh, areas. Whereas the far side's almost completely cratered, there's very, very few maria. That's because the crust, the actual lithosphere of the moon, is much thicker on the far side than the near side. And again, that's weird. Like, why- why should that be? Why is there a dichotomy like that? And so one s- one idea of there is that actually two moons formed in this process, and then one kind of pancaked onto the back of the- of the moon as we know it today.

    3. CWChris Williamson1:11:54

       No way.

    4. DKDr David Kipping1:11:54

       And that- it's that pancaking that then formed like a thicker shell on the far side of the moon. So...... there's- it's like, I wish we had a time machine, because this would have been like the greatest fireworks show in- in- in the universe to have seen the formation of the moon. And again, it raises so many questions, like how- how unique was that? Does that happen in other exoplanet systems? Are we special that this happened here? We don't really have any observational evidence either way, but obviously my team and I, one of the things we've been trying to do over the last few years is to try and detect moons around other planets, to try and ultimately answer this question. Because, at the end of the day, the moon has a huge influence on our planet. It stabilizes the obliquity of the Earth, it gives us the tides, it gives us, you know, the- the rise and the fall of the tides which potentially are a useful thing for life. They create rock pools on the s- on the- on the coastlines. Especially when the moon was closer in, it would have formed o- you know, continent-covering tides, basically. The entire continent would have been covered in a massive tide that would have formed all these rock pools all over the place. Um, it also, uh, potentially stripped off the upper mantle, the upper lithosphere of the Earth, and that could have been used...

Episode duration: 2:21:30