Will We Ever Find Alien Civilizations?

22:29David Kipping:Why did your alarm clock not go off this morning? Aliens did. And so that worries me a bit as a hypothesis, just from the kind of like the Paparian standards of how we even talk about falsifiability in science. So the fact we don't have an explanation is not evidence for aliens. That's just the first thing we should discount. And then the idea of more specific evidence for UFOs, it's mostly actually personal testimony, but the actual videos we've seen not very convincing so you know there's these three videos the pentagon released there's no range information on any of that so it's very difficult to know whether you're looking something like right in front of you in the foreground or far away and the pilots said oh no i had a good idea of where it was i knew what it was but it's not reproducible and of course science is all about reproducibility if you can't reproduce it we just don't know what to do with that so i think in a nutshell my big issue with the ufo claims has been that we can't even ingest it into science.

23:26David Kipping:If I'm going to ingest any scientific claim, I need to know two numbers, the false positive rate of that experiment and its true positive rate. And I've proven this in a Bayesian paper. There's no way to interpret an experiment if you don't know those two numbers. Because if your false positive rate is 99 % and someone says, I saw a UFO, it's almost certainly a false positive. You have to know these numbers in order to make sense of it. there's no way to even ingest these claims into science as they currently stand. Oh, that's a very interesting take, the statistical argument from Bayesian thinking that we can't even assess these claims properly.

24:06That's very much his expertise. He's really brought to the fore these kinds of ways of thinking that have allowed him really to make progress instead of saying, hey, does this specific one planet right here have life, right? It's easier to talk about the collective and what trends we might expect and to deduce from there. Yeah, I was very interested, I would say captivated, because we are hearing so much these days from what seemed like credible, maybe not quite credible. I guess what I'm thinking is the people that were military, you know, that don't seem like they're prone to exaggeration, that saw something they can't explain.

24:50And I thought the humility of David's reaction that there's so much that we can't explain. Why would we leap to the alien idea? Why don't we just say, there's a lot of things we can't explain and just live with that? Yeah, I absolutely agree with you. I don't feel that we should be disparaging people who are coming forward and reporting sightings. We kinds of data and information on observations citizens and experts are making of unidentified aerial phenomena. That's respectable, admirable. But the leaping to this is aliens is problematic. I wanted to ask you some things about that because it seems like it's right in your wheelhouse.

25:32I mean, it is so problematic given what we know about cosmic distances and given our understanding of the speed limit of the universe set by the speed of light. Yeah. I mean, I was just looking up the numbers to remind myself this morning. Just within our galaxy, the types of numbers we would be talking about, like if we imagine that an alien came by spaceship from a planet around some star in our galaxy, that would be on the order of tens of thousands of light years, even if they were going at the speed of light. We didn't even have civilization 10 ,000 years ago. Yeah, we're talking to David's point, either there have to be a huge number of civilizations for that to be viable that we overlap and communicate huge number, because they're traveling, let's say 100 ,000 light years to cross the galaxy, at the speed of light, right, to get all the way across the galaxy.

26:27So, yes, there's a lot of planets and star systems and moons within that range. But we haven't had civilizations for hundreds of thousands of years. We've had civilization, as you said, really just for a few thousand. And we've only had technology for a couple hundred years. Right? A couple hundred years. And it's unclear that our technology is sustainable, that we'll be able to keep having electricity and energy for everybody on this planet sustainably. So we might only have had a few hundred years of technology total, and that might be it. So you're talking about trying to overlap across these incredibly vast spatial distances and this incredibly long time scales in a bleep, right, an absolute bleep.

27:13And then it becomes, well, if we do overlap, then probably there are a whole huge ton of civilizations because then they're in our backyard and they came really close. and then by coincidence they overlapped with us in time. And if we don't, well, you know, that kind of seems like, yeah, maybe that's just the odds. Can I just ask one thing that's silly? I mean, because there's always this question of is there biological evidence? Like, do we have the dead alien from the crash? It's so perplexing that these civilizations would be good enough to travel at close to the speed of light or they develop wormhole technology, but they can't land safely in Kansas?

27:56Exactly. Or they can't keep hiding from us very successfully. Well, it can't get enough of aliens, but I think we've locked that down. Good. Well, I want to listen to more. After the break, we're going to zoom out to exomoons. And that refers to moons outside of our solar system. So we're going to discuss what exomoons mean for the search for life in our universe.

28:34Welcome back to The Joy of Why. We've been speaking with Columbia University astronomer David Kipping about the probability of life in our universe. So you've used this sort of deep statistical thinking, not just to analyze theoretical concepts like the Drake equation, but really importantly, to actually search for places where life might emerge. And we already mentioned it lightly, but the idea that moons are a really interesting place to consider. From our own experience, in our system, moons are plentiful. There are hundreds of moons in our solar system, which is really kind of amazing. What advantage are the exomoons offering you over an exoplanet in the search for life?

29:22David Kipping:Yeah, I'll give you my sort of four boilerplate reasons why I always say we should look for moons. One is that, of course, as you alluded, they could be habitable themselves. Two is that they could influence the habitability of the planet they orbit. So you might have an Earth-sized planet. And I think an obvious question is, well, does it have a moon-like moon around it as well? Because that seems like it had a big influence on our history. We probably want to know that. So you've got those two kind of habitability aspects. Then there's just the pure uniqueness question. Maybe come back down to that more kind of mechanistic astrophysicist view.

29:54David Kipping:Just how do we get here? What's our origin story? is the moon like a one-off fluke that just very rarely happens? Or is that an inevitable part of terrestrial planet formation that you end up with these large, almost quasi-binary objects? There's lots of strange moons, and it's like Triton goes around backwards around its parent planet. You've got Uranus tilted over with its moon system. So there's lots of curiosities in the solar system that from a singular example, it's difficult to know like really how does this story play out in other environments so i think just uniqueness is another reason and the fourth one is kind of subtle and that's thinking about next generation missions i mentioned we want to build a successor to james we have one day probably called at the moment the habitable world's observatory hwo but it will hopefully one day take a photo of another earth it'll be a single pixel but it'll be a single blob of light They're like the pale blue dot.

30:50David Kipping:And from that pale blue dot, we'll split the light up into a rainbow, essentially like the prism, like Newton did. And we'll look for those atmospheric biosignatures that we're so interested in. And moons here can really screw us over. If anyone's ever seen that famous pale blue dot image that I think it was a Voyager 1 took, and it looked back at something, it's like the orbit of Neptune. It turned around, it looked back and took a picture of the Earth. It's this beautiful image. You've never seen it before. and in that image it's not a pale blue dot even though sagan described it as a pale blue dot it's a pale blue gray dot because the moon's in there the moon's right it's photobombing right along right you can't distinguish it you can't separate it they're just one smudge of light so when hwo takes these images it's going to be in the same situation it's seeing what it thinks is a planet, but it's really a planet plus however many moons it has.

31:43David Kipping:And when we look at moons like Titan, Titan has a methane atmosphere. Methane lakes is full of interesting hydrocarbons. You could easily, if you didn't know that was a separate moon, get confused. You could imagine having an ocean world, a terrestrial ocean world, where the water undergoes photolysis, and that means that the H2O splits into hydrogen oxygen. So you've got an oxygen-rich planet, No life involved, just oxygen from UV radiation. That's it. And then you've got Titan mixed in there, which has methane. So now, from the astronomer's perspective, everything looks beautiful. You've got methane, you've got ozone, you've got oxygen.

32:23David Kipping:You'd be like, we're done. That's life. But it's a confounder. It's just something we hadn't thought of. So that's why I think moons are really important. I don't know how we could even look for life with HWO unless we resolved the moon problem. So can you catch us up to date as to where we are in terms of actually observing, not just theorizing, but actually observing the satellite missions, exomoons? So this has been obviously a long quest in my entire career. During my PhD, I came up with one of the methods that we are using today to try and look for these moons, thinking about the dynamical perturbations that a moon would impart upon its parent planet gravitationally.

33:00David Kipping:And that's kind of how we look for planets. We often look for planets by detecting the gravitational influence it has on the star. So we've kind of extended that to looking for these moons. And I think what we know for sure is that Kepler, which, as I said, was this transformative mission, had this sensitivity down to about Earth-sized stuff, moons, planets, whatever it is. And it really didn't throw out many candidates. There's just not a lot there. So out of the four, 5 ,000 Canada exoplanets, we have just a couple of hints of moons in that entire database. So that already tells you Earth-sized moons are not that normal.

33:42David Kipping:I'm not saying they never happen, but they're certainly not par for the course. We did find a couple of interesting candidates that I hinted at there, but they both have been very surprising because they're so large. They are Neptune-size or even mini-Neptune-size moons orbiting Jupiter-size or super Jupiter-mass planets. So nobody really expected that. I mean, it reminds me a bit of hot Jupiters, some of the first exoplanets ever found. They're Jupiter-like worlds, but are about 10 times closer to their star than Mercury's around the Sun. Very close. Yes, scorching temperatures, thousands of degrees Celsius on their day side.

34:20David Kipping:and so it was very surprising actually a lot of people didn't believe them they thought how could you possibly get Jupiter there because we think we know how Jupiter formed it formed from ices it formed from essentially the same kind of cometary material that you find out in the distant solar system so that stuff just wouldn't be stable close to a star it would boil off so you can't make Jupiter-like planets there but we now know they're definitely real because we've just found like so many of them and it still puzzles us how they got there we still don't understand it and so we found these two large moons, 1625 B-I, and then there's also Kepler 1708 B-I.

34:59David Kipping:So the B is the planet, the number plate is the star, and then the dash I is the moon. Those are the only two we found. Other teams have seen hints in different observations as well. No one yet has like a crisp, clear slam dunk signal. And I think that's what we really need. The field is in desperate need of that kind of clear signal. Obviously, a big thing close to the star is the easiest signal you can possibly get. And I think a general story in astronomy is that often the first examples of things we discover are not typical. They're often very unusual beasts. And the reason we find them first is because they're so loud.

35:39David Kipping:They're disproportionate. They're tail end members of their population. They're not representative. And so it wouldn't surprise me if these things turn out to be real, but they're still requiring follow-up to ultimately figure out what they are. But James Webb has been opening up a lot of doors for that. So the Kepler sample you're talking about is within a few thousand light years. So our galaxy's over 100 ,000 light years across. So this is still pretty much, as you've said, we're really only probing our region of the galaxy. How is James Webb Space Telescope changing some of the story? yeah so james webb is not really trying to discover new planets it's certainly more than capable of doing so it's just that the tusk at time is so precious a better use of its time is to do stuff like look for exo moons we've done that experiment recently unfortunately it came out flat we looked at this beautiful jupiter analog planet it's really had kind of a similar orbit, a similar star to our own solar system.

36:41David Kipping:This Jupiter-sized planet on a nice long orbital period far from its star. We searched it for moons down to about the size of sort of Ganymede, so the largest moons of Jupiter, and we don't see them. So that's already really interesting. Another experiment we've been doing is actually measuring the ablateness of exoplanets, which has never been done before. But you can actually tell whether the planet is a pure sphere or slightly ellipsoidal, which of course planets really are. They're ablate spheroids because as they rotate, they bulge out at the sides. And so they get these kind of love handles like the Earth has a slightly wider equator than it does the North-South Pole.

37:19David Kipping:And Saturn's actually pretty extreme. That's actually quite detectable with James Webb. So it's such an impressive machine. There's no need to use it to find planets because it can really characterize the planets and especially atmospheres. Well, let's talk about atmospheres. We've talked a little bit about technological signatures, we haven't talked that much about the biosignatures. Would that be a reason why astronomers are obsessed with atmospheres? Because they're looking for biosignatures for the emergence of life. I think we want to get there. I think a lot of us are dubious. James Webb is sensitive enough to detect biosignatures.

37:52David Kipping:If you take the Earth, and even if you put the Earth around a very favorable star, so a nearby star, and make it a small star because the smaller the star is an earth-sized planet will block out more of its starlight and so it's easier for us then to actually measure these atmospheric signals and even in those very favorable conditions the signal we're looking for is that the planet effectively appears different sizes at different wavelengths of light and the wavelengths of light corresponding to say ozone absorption you see the planet puff up a little bit and what that's telling us is that there's a molecule, ozone in that case, that really likes to absorb that wavelength of light and therefore make the planet appear a little bit larger.

38:34David Kipping:So we think that's how you would potentially detect ozone. It's just that the telescope isn't quite sensitive enough, unfortunately, to get most of those biosignatures. We think of things like methane, ozone, phosphine, dimethyl sulfide has been proposed recently as well. There was a claim actually of dimethyl sulfide. Maybe some of your listeners might know that using James Webb, but it's really spectacular levels compared to what we have on the Earth. So a lot of people are skeptical. It's remotely possible that could be a biosignature, just way too much of it to make sense for certainly an Earth-like biosphere.

39:09David Kipping:But there's a lot of controversy with some of these detections, but I think most of my colleagues think that it's just beyond the ability of James Webb to detect biosignatures, but that's fine. Probably a more basic question you might ask is, do Earth-like planets even have atmospheres to begin with? Or are they barren rocks? Because the moon doesn't have an atmosphere. Mars doesn't have much of an atmosphere. Mercury doesn't have an atmosphere. And so there's a huge program right now with James Webb called the Cosmic Shoreline Program, which is to look at a group of planets which are Earth-sized in the haptical zones of their stars.

39:42David Kipping:And the question is whether the planets even have atmospheres, because M-dwarfs are quite active. They throw out these huge coronal mass ejections, these stellar flares. And so there is a concern that maybe the atmospheres are gone. Maybe these planets can't even sustain an atmosphere. James Webb can answer that question. So that's what this program is doing. So it should be able to tell whether Earth-sized, habitable zone planets have an atmosphere or not. And that would already be a massive breakthrough. Amazing. So clearly, if they have atmospheres, the prospects for life goes up, loosely speaking, in that Drake equation kind of a way.

40:20Some of these biosignatures, though, are confounding. If you could find the atmospheres and you were to look for some of these signatures, you've mentioned certain elements that we're looking for, certain molecules that we're looking for in the atmospheres, because the presumption is that these are outgassings of metabolism, presumably, or something like that. But we don't even really know that, do we?

40:39David Kipping:No, I mean, we just have one example. The confounders is a really big problem. And I've been thinking about that a lot. And what worries me a lot is that when you look at the history of biosignatures, just very broadly, there's been so many spurious claims. I mentioned very briefly that Alan Hill was meteor, which was rock on Mars four billion years ago that knocked off land on the earth, land in Antarctica, I think in 1984 or something. And they collected it, they studied it, and they found these like things which looked like little worms under the electron microscope. And so that was essentially a biosignature.

41:11David Kipping:It's not a gas, but it is a biosignature. It's a signature of biology. And it turned out that even though it looked like life, other geochemists and scientists were able to show that you can make structures like that without biology involved whatsoever, just basically through water and high pressure water in particular. And so that really killed the momentum behind that claim. Another example, if we go really far back, would be Martian canals. Seems silly now, but Percival Lowell, he thought there was canals on Mars because he thought that was a biosignature. He saw these lines on Mars and he thought, I know what causes that.

41:46David Kipping:It's a canal system. So often we are tripped by what we don't know. It's not Percival Law's fault that he didn't know about those psychological biases because nobody had published on them yet. And a very recent example was DMS, dimethyl sulfide. Dimethyl sulfide was claimed, as we mentioned earlier, in an exoplanet atmosphere recently, K-18b, Cambridge University did a huge press release talking about this being, you know, a historic moment in the search for life. But we now know that DMS is on comets in the solar system. Unless you think there's living creatures on all the comets, it seems difficult to believe that this is an unambiguous biosignature anymore.

42:21David Kipping:So just time after time after time, it's like Groundhog Day, Johnny. You just keep waking up, we hear these claims of life, and then we all know what's going to happen. Happens every time, it just dissolves. So I've been thinking about this really hard recently. And yeah, I do think the current approach we're using just will never work. And we do need to really rethink how we do this. And have you made progress in suggesting a way that we should do this differently? Yeah. So my tentative suggestion is to do what I call A-B testing, which in YouTube landscape is something we're very familiar with.

42:52David Kipping:Like you have two thumbnails and you challenge them against each other and see which one gets the most clicks. And so the way we do it here is you'd have two samples of planets, for example, and you have some reason to believe this is the condition for this experiment to work you have reasons to believe that the occurrence rate of life is different it can't be the same if they're the same this doesn't work there has to be a difference in the life occurrence rate but the confounder rate how often natural geochemistry or whatever it is producing ozone or whatever signature you're looking for, that has to be the same.

43:28David Kipping:So the confounded rate is the same between the two samples, but the life rate is different. And so really then you're doing a differential measurement. Any difference you observe in biased signatures between those two populations, therefore in a differential sense, has to be due to life. It doesn't tell you how much life there is in an absolute sense. You still don't know, but you know that that excess must be driven by life. So that statistically is very clean. It resolves a lot of these problems and these unknowns, but you might reasonably question whether it's even possible to set up such an experiment.

44:00David Kipping:And that's what I'm thinking about now. Amazing. So again, you're returning to the kind of statistician's roots, right? That the observations aren't going to be one moon with one obvious signal, it's more large samples and large statistics. Yeah, I'm skeptical it would be a slam dunk in the same way maybe we've had with other fields. To quote Donald Rumsfeld, it's the unknown unknowns that get you, right? And so there's so much we don't know about chemistry and geochemistry and other planetary environments that it feels like we are doomed to always be caught out by those things. I think the only exception to this I can imagine is actually a really strong information-rich SETI signal.

44:44David Kipping:So if it was like a laser beam with a video transmission encoded within it, there's just no plausible natural confounder to that. You just can't imagine it. It just seems impossible. But with biosignatures, those gases are very information weak. Really, all you measure is that gas is there and an abundance, maybe, if you're lucky. And that's about it. So it's that informatics perspective, I think, that really endangers biosignatures. They just don't carry a lot of information to begin with. So how do you place yourself in the optimism, pessimism spectrum? Are you searching for life scientifically because you believe that this is a viable result within your scientific lifetime?

45:29Or are you more, I'm interested in planets and moons from the aspect of astronomy regardless of the discovery of life?

45:38David Kipping:I'd say I'm hoping and I'm more interested in the idea of life. That is a great dichotomous split, I think, that you just gave there. And I think a lot of astronomers are driven by how does the universe work or are we alone? And those are like two very basic drivers, a lot of astrophysicists in different ways. I mean, I'm interested in both, but I'd say I'm probably more driven by the latter. However, am I an optimist or a pessimist? I honestly try to be, it's a little bit of a cop-out, but agnostic and forcefully agnostic because I'm so terrified of experimenters' bias. And we've seen this so many times in history of scientists even claiming life, claiming this comet is an interstellar ship, claiming this little rock on Mars is a face, claiming this fossil from the Alan Hills meteor, Bill Clinton stood on the White House lawn and talked about that as evidence for life on Mars.

46:35David Kipping:And now nobody believes it. So many times we've got caught up in that excitement of optimism. And I think the lesson for me has always been like, just try and remain sober. Just try and look at it objectively and require those high standards of evidence that we apply in all other aspects of our science. It's not different when we look for life. So I try to remain objective. And I think, honestly, it is perfectly consistent with everything we know about the universe that we are alone. There's nothing we know about the universe that rules that out is within the realms of possibility. Well, given that we're alive and we're here and we have the luxury of looking deep into the sky, What is it about this exploration that makes this the way you want to spend this precious life that we have?

47:28David Kipping:For me, it's very much just curiosity driven. It's just these are the things I've always wondered about life in the universe. What else might be out there? I've always dreamed of visiting other stars and seeing their planets. It's just that pure, very simple curiosity driven fascination with what's out there. And I think if you don't have that, life can feel a bit empty, at least for me. Like, I always get a bit depressed when we ask sometimes a scientist to defend the technologies or industrial applications of searching the universe for gravitational waves or something. Sure, there is many side benefits and we can list those off.

48:04David Kipping:But in a very pure sense, the reason for doing it is the same reason why we do poetry. It's the same reason why we do art. It's that what is the point of being on this earth if our sole interest is bread on the table, feeding myself, going to sleep, waking up next day, going back to work, and that's your whole life. It's just this pure machine-like process. We're more than that, I believe. And I think looking out and wondering about the universe, it enriches our soul, enriches our human nature. I would hate to live in a world where we didn't ask these questions. And I think it's a real privilege, certainly, that I've had a career where I've been able to dwell on some of these questions and think about them so much.

48:44Such a pleasure to talk to you and to share your stories and your insights and your ideas about the future of discovering whether or not we're alone. This is really a delight. Thank you so much.

48:55David Kipping:It's always a pleasure, Janet. Well, I want to agree with that. I have often tried to make that argument myself about enriching our soul. But there's a very natural reaction to have to that, which is we fund, or at least we used to fund science, but we don't really fund poetry. You know, why should the taxpayer invest in science if it's another form of poetry? Yeah. And what do you think the answer to that question is? I think it's much more than poetry. At least it's very different from poetry. It's partly poetry. It's many things. I mean, it's a really serious question, especially in the age of artificial intelligence where so many of the things that we're doing, we have to ask, why are we doing them?

49:44I don't know. Yes, part of it is for soul enrichment. Part of it is for helping future technology or helping new medicine or improve the quality of life of all of us. I want all of it. I don't know. What do you think? Well, I would say that obviously really resonates with me what David's saying, but for a reason that I think is also transformative for humanity. If you think about the shift with Copernicus from thinking we're at the center of the universe to understanding and comprehending that we are not, that has untold implications, consequences, ramifications for the entire paradigm of civilization and what we're doing here and how we handle each other.

50:28And so I think it can both be the dreaming blue skies approach and have implications for the future of humanity. I think Earthrise is a very good example of that. Looking back at the Earth as it rose over the moon in the Apollo missions, initiated environmental movements. It really gave people a strong sense of connectivity on the Earth and kind of the limitations and evils of tribalism. So it changed culture, right? It changed civilization. And so I think we can do both those things. I like your answer a lot, that this cosmic perspective, as someone like Carl Sagan might have called it, maybe he even used that phrase, gives us a kind of humility and maybe makes us better people.

51:17You know, and if, as you say, like when we're talking about alien civilizations, that our whole civilization is a blip in time, each of our individual lives is an even shorter blip in time. And why not be as good as we can be for that blip? You know, I mean, here we're getting into theology and ethics and all of that. But maybe science, which is often seen as somehow separate from all of that, is really a very good teacher about how to live ethically. I think it is. Yes. And I think about how to cooperate internationally, how to transcend belief systems and trappings of nation and faith and to instead view ourselves as one species playing out on this one place together.

52:04Well, on that note, man, I need to go meditate. Okay. Exactly. I need some universal transcendence. If you're enjoying The Joy of Why and you're not already subscribed, hit the subscribe or follow button where you're listening. You can also leave a review for the show. It helps people find this podcast. Find articles, newsletters, videos, and more at quantamagazine.org. The Joy of Why is a podcast from Quanta Magazine, an editorially independent publication supported by the Simons Foundation. Funding decisions by the Simons Foundation have no influence on the selection of topics, guests, or other editorial decisions in this podcast or in Quanta Magazine.

52:56The Joy of Why is produced by PRX Productions. The production team is Caitlin Falls, Jade Abdul-Malik, Genevieve Sponsler, and Merit Jacob. The executive producer of PRX Productions is Jocelyn Gonzalez. Edwin Ochoa is our project manager. From Quanta Magazine, Simon France and Samir Patel provided editorial guidance with support from Samuel Velasco, Simone Barr, and Michael Canyangolo. Samir Patel is Quanta's editor-in-chief. The episode art is by Chanel Nibble Inc. And our logo is by Jackie King and Christina Armitage.

53:37David Kipping:Special thanks to Garth Avery at the Cornell Broadcast Studio. I'm your host, Jana Levin. If you have any questions or comments, please email us at quanta at simonsfoundation.org. Thanks for listening.