Pod Insights StarTalk Podcast Cosmic Queries – Life on Exoplanets with Sara Seager About this episode Is there life on other planets? On this episode of StarTalk, Neil deGrasse Tyson and co-host Matt Kirshen dig into the search for extraterrestrial life with exoplanet expert and author of the memoir, “Smallest Lights in the Universe,” astrophysicist Sara Seager.
Originally Aired March 15, 2021
Transcript Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.
0:00 Neil deGrasse Tyson? Hey Startalkians, Neil here. You're about to listen to an episode specially drawn from our archives to serve your cosmic curiosities. Check it out.
0:13 Neil deGrasse Tyson? Welcome to StarTalk, your place in the universe where science and pop culture collide.
0:22 Neil deGrasse Tyson? StarTalk begins right now.
0:26 Neil deGrasse Tyson? This is StarTalk. I'm your host Neil deGrasse Tyson, your personal astrophysicist, and this week is a cosmic queries edition, the always popular cosmic queries, and the topic, the always popular search for life in the universe. And I've got with me as my co-host Matt Kirshen. Matt!
0:47 Matt Kirshen? Hey, hey Neil, how you doing?
0:49 Neil deGrasse Tyson? Okay, I spent all day yesterday trying to memorize the name of your podcast, It's Probably Science. Did I get it right?
0:55 Matt Kirshen? It is!
0:57 Neil deGrasse Tyson? I always mangle it.
0:58 Matt Kirshen? I was confused you were going to go for another variant.
0:59 Neil deGrasse Tyson? I stumbled in my efforts there. I found a podcast called Sometimes or Mostly Science. It's a whole other podcast.
1:07 Matt Kirshen? Oh, we hate them. No, we've got a running rivalry with them. It's gonna be-
1:10 Neil deGrasse Tyson? You totally have rivalries. I gotta make sure I get your stuff right.
1:13 Matt Kirshen? It's gonna come to violence at some point. Probably violence.
1:17 Neil deGrasse Tyson? So I know a little bit about the search for life, but not as much as our guest today. Our guest today is Sarah Seager. Sarah, welcome to StarTalk.
1:27 Speaker 02 Thanks for having me today.
1:28 Neil deGrasse Tyson? Yeah, so Sarah, let me get your full title up here. So you're professor of aeronautics and astronautics, physics and planetary science at MIT. Is that, no, they left out a few categories, I think.
1:44 Speaker 02 No, no, no. It's because exoplanets and the search for life is an incredibly interdisciplinary topic, and it draws upon all those different fields.
1:52 Neil deGrasse Tyson? Excellent. But between you and me, can I call you a planetary scientist, right? That's really-
1:57 Speaker 02 Yes, yes. I mean, my home is really in astrophysics. So you could call me an astrophysicist or a planetary scientist, or both.
2:07 Neil deGrasse Tyson? In the club. So I guess the search for life in the universe has to necessarily include the search for exoplanets, right?
2:15 Speaker 02 Right.
2:16 Neil deGrasse Tyson? They go together. But is that part of our bias?
2:19 Speaker 02 Not necessarily. We do. I mean, we're definitely terrestriolic. We're we definitely are narrow minded. But at the same time.
2:27 Neil deGrasse Tyson? Like Earth centric.
2:27 Speaker 02 Yeah, like Earth centric, you know, and on Earth, we believe that for the origin of life, we need a place for ingredients to concentrate. And it's it's hard to imagine ingredients just, you know, concentrating in in the vastness and that low density of outer space.
2:40 Neil deGrasse Tyson? OK, so this concentration thing, I think, is under celebrated out there. I mean, in the public, that people, we take it for granted that we have rocks and buildings and mountains and people. And for in our greater universe, nothing is together. I mean, mostly, it's mostly empty. And where it's not mostly empty, it's highly rarefied. And so planets are really special places. Is that?
3:07 Speaker 02 Right, they are. Very special because they do concentrate complex molecules. They concentrate elements, nutrients, and everything we need.
3:17 Matt Kirshen? Am I right in thinking they are substantially less special or at least less rare than we thought they were even five, 10 years ago?
3:25 Speaker 02 Yes, actually, we are slowly making ourselves less and less precious, less and less special.
3:34 Neil deGrasse Tyson? No, Sarah, it's OK to know that. You're not just supposed to tell people that.
3:38 Matt Kirshen? I think that's nice about science. I like the fact that scientists sort of switch between going, you're incredibly special and you're not special.
3:48 Speaker 02 We do. We love thinking back to the Copernican revolution, where before Copernicus, the model of the universe was that our Earth literally was at the center of the universe. All the planets and the sun and the stars apparently all orbited Earth.
4:02 Neil deGrasse Tyson? I think I've heard, is it Andruin described this sequence? Some combination of her and the and the Carl Sagan camp referred to it as the sequence of great demotions for whatever we imagined ourselves to be. Plus, there was some rebuttal to that. I forgot the fellow's name, but he wrote, I think convincingly, that the idea That the idea that we are in the center is not necessarily an elevated place. If heavens are above us, right? So the center could be the slag heap of where everything collects. And your ultimate goal is to ascend from that to greater places. So, but in either case, the, the location was unique, I think, I think about it.
4:46 Matt Kirshen? So, so in his mind, we're like the plug hole of the universe. We're sort of the drain.
4:52 Neil deGrasse Tyson? So, so Sarah, you, was it natural to transition from exoplanet discovery to the search for life? Or did someone have to sort of nudge you? Or was it just obvious as the next thing to do?
5:06 Speaker 02 You know, every scientist is different and I've sort of been the random walk type of scientist, like work on a problem and see a more interesting problem and then move over slowly.
5:17 Neil deGrasse Tyson? You like the dog being distracted by the squirrel, you know? Squirrel!
5:20 Speaker 02 Yeah.
5:21 Neil deGrasse Tyson? You can't keep it. But, but, but when you started out in the, in the late 90s, we, we didn't, didn't know many exoplanets and even those that we did, it was fun to think of aliens on them, but there was no research program there yet. So, so it seems to me you were there at the birth of this, if not having birthed it yourself.
5:47 Speaker 02 Yes, and in fact, but just to go back even further, before my time, perhaps even before yours, but in the decades past.
5:54 Neil deGrasse Tyson? Even before Neil.
5:56 Matt Kirshen? There is no such thing.
5:58 Speaker 02 No, okay, well, you know, what's interesting is if, if you look back, like even, you know, just after the time of Sputnik, like in the early 1960s, there's actually a report from a think tank kind of company and it actually talks about planets and exoplanets and the chance for other Earths. And even in the decades after that, you know, there were always studies on how would we go about finding another Earth. And so when Exoplanets was born in the mid 1990s, and yes, I was there, I was a graduate student working on exoplanets at the time, you know, they were hot Jupiters, they were not suitable for life in any way. But slowly those two things came together, you know, all the past decades of thinking about Earths, then switching gears to the hot giant planets.
6:44 Speaker 02 And so the thought of finding Earth and life, it was kind of always there in the background, even though it might have been a bit of a stretch.
6:49 Neil deGrasse Tyson? And just to be clear, the Jupiters that you're referring to being hot was it was easier to find really massive planets first compared to low mass planets. So you're going to find a Jupiter first, and they're hot because why?
7:04 Speaker 02 Because they're very close to the star, so close to the star that as heated by the star, they're just hot.
7:10 Neil deGrasse Tyson? OK, so the Jupiters, but they didn't look like our Jupiter. So there again, we were not. So we thought we were representative of the universe, and we're not. I mean, at least our solar system.
7:20 Speaker 02 Right, right. We always expected to find a Jupiter where our Jupiter is, which is, you know, five times further from our sun than Earth is. And instead, we found Jupiter mass objects within a few, you know, few day period orbits of the star.
7:35 Neil deGrasse Tyson? So even our bias that which shows up every day in race relations and sexism, it even shows up in astrophysics just.
7:42 Speaker 02 It did, yeah. And you know, the funny thing is, is just to take that a level further. When we, people first found these hot Jupiters so close to the star, we just assumed that they had the same albedo, the same reflectance properties as Jupiter itself. Jupiter is quite bright, you know? You see it in the sky because it's got icy clouds. And we couldn't see Jupiter in reflected light. And with a little more thought, we realized, wow, these hot Jupiters, they're incredibly dark. They're very absorbing. They have no reflective clouds, most of them.
8:11 Neil deGrasse Tyson? Wow, OK. So they're not only, so they're big Jupiters that don't look anything like Jupiter. That's what you're saying.
8:19 Speaker 02 Like, I mean, yes and no. They don't appear like their atmospheres aren't like Jupiter, but their kind of bulk composition, they're mostly made of hydrogen and helium. That part's the same.
8:27 Neil deGrasse Tyson? All right, so if you come to this as an astrophysicist, planetary scientist, and now you want to think about life, you gotta start knocking on the doors of biologists. So when did all that happen?
8:36 Speaker 02 Remarkably, it really, it started happening for me when I had my first staff position. I worked at a place called the Carnegie Institute of Science, and I was in Washington DC. And it's quite interdisciplinary there already, and they were already part of, of working on the somewhat new field back then of astrobiology. So I started, were interacting with biologists there. And the funny thing was, is I got a postdoc there and I signed him up to work with me. And it literally took us like nine months before we could even understand each other. Because our language was so different. Yeah.
9:08 Neil deGrasse Tyson? So you need the coffee lounges, you know, between, at the intersections of departments. Because otherwise, we just live in our stovepipes and discoveries go unattended to.
9:20 Speaker 02 It's true, it's true. And later on, I attended an astrobiology conference. And I met a remarkable person there who became one of my closest colleagues. And so then through him, him being a biologist, I was able to learn and accrete more, more collaborators.
9:34 Neil deGrasse Tyson? And so, I mean, you have a fascinating story. I only recently learned that you've actually collected that together in a, in a kind of a memoir, The Smallest Lights in the Universe. So congratulations on that memoir, published by Crown in 2020. And because we're all distracted by big explosions and big lights and big things. But maybe the smallest lights in the universe, I guess these are the exoplanets. Or it could be metaphor for other things in the book, that it's, just call attention to other previously underserved domains of the cosmos.
10:10 Speaker 02 Thanks.
10:10 Neil deGrasse Tyson? Yeah. So, so let's get straight, let's get straight to this. What is life?
10:17 Speaker 02 You know, in exoplanets, we have a good excuse for completely avoiding that question.
10:23 Speaker 02 And we do, we do, I'll run it by you, I'll run it by you.
10:26 Neil deGrasse Tyson? All right.
10:26 Speaker 02 Because we have telescopes and we can see atmospheres of other planets. We're hoping with our next generation telescopes to see atmospheres of small rocky planets. And we're going to look for signs of life by way of gases that might be attributed to life that have accumulated in the atmosphere. So we prefer to think about what life does. Life metabolizes. And it may give off gases during that chemical process of metabolism. So we conveniently sweep that under the rug and we just talk about what life does.
10:55 Neil deGrasse Tyson? Are you sweeping under the rug because you can't do anything about that question anyway?
11:00 Speaker 02 We can't do anything about it. And it's just a question that no one wants to agree on what the answer is.
11:05 Neil deGrasse Tyson? So you sweep it under the rug and say, let's do what life, let's observe what life does. So you're the atmospheric gases equivalent to the people who study animal poop, for example. It's things that life does, even if you're not studying the life itself, is that?
11:25 Speaker 02 That's right.
11:27 Neil deGrasse Tyson? Not to equilibrate your study with the study of feces.
11:30 Speaker 02 And actually, Neil, that's never been done before. So that is brand new.
11:34 Neil deGrasse Tyson? It's a brand new analogy.
11:37 Matt Kirshen? You're saying atmospheres on planets are kind of the animal remains of the galaxy?
11:42 Neil deGrasse Tyson? Well, the gaseous effluences, I guess.
11:45 Speaker 02 Yes, actually, that's a great way to look at it.
11:47 Neil deGrasse Tyson? So Sarah, but clearly there are gases out there. And I want to get to the Q and A because Matt has them lined up and I don't want to lose any time on that. But clearly, there's some gases, let's take methane, for example, that we know is the byproduct of life, not all life, of course, but some bacterial life on Earth. We know that. So now, let's look to another place like Saturn's moon Titan. Oh, my gosh, it's completely covered in methane. So it must be teeming with life. So, but it's not. So where do you?
12:30 Speaker 02 Yeah, that's the single most biggest problem, that we need to be able to see other gases in the atmosphere and put the gas in question in context with what else is there. But even doing that will be, it'll still be hard. It'll be very, like a forensic crime scene, you know? How do we pick out what is really life, what is really not made by life?
12:50 Neil deGrasse Tyson? So the gases you list that are the products of life are necessary but insufficient to
12:58 Neil deGrasse Tyson? Prove that there's life.
12:59 Speaker 02 Yes, actually, and that is the sort of, let's call it the dirty secret of the whole field, is that we'll never be able to prove it.
13:06 Matt Kirshen? So it's sort of in forensic crime scene terms, you've sort of got to distinguish between blood that was caused by the crime and blood that was just previously existing, sort of decorative blood in that room.
13:16 Neil deGrasse Tyson? Precisely.
13:19 Matt Kirshen? Just blood that someone had put there that would just naturally be there on the walls in a splatter.
13:24 Neil deGrasse Tyson? Yeah, the normal blood that would, that exists in the room. I'm sure Sarah is going to put that analogy in her next research paper.
13:31 Matt Kirshen? Yeah. Just put it just out in an equation and that's all science is, right?
13:36 Neil deGrasse Tyson? Yeah, but it's in an equation, it's legit.
13:38 Matt Kirshen? Yeah.
13:38 Speaker 02 And so on our earth, we have methane produced by life, by bacteria, you know, by cows, but we also have methane coming out of mid ocean ridges. So in a lot of cases, it is definitely ambiguous.
13:50 Neil deGrasse Tyson? And methane is natural gas that we have in our stoves, and I'm pretty sure what's coming out of your stove is not cow farts, it's come from another location on earth. Okay, so Matt, we have a couple of minutes left in this segment, but let's see if we can squeeze in a question.
14:05 Matt Kirshen? Okay, great, well, this one, I love the questions that come from our younger listeners. This one comes from Carrie Jenkins, an eight-year-old fan.
14:12 Neil deGrasse Tyson? Eight!
14:12 Matt Kirshen? How long, I know, how long do you think it'll take for us to find other life in the universe?
14:18 Neil deGrasse Tyson? Yeah, how close are we, Sarah? How many, how many more years? What do we got here?
14:22 Speaker 02 Well, we actually will have, we like to say we'll have the, I'm not purposely trying to evade all your questions, honestly, but I would like to say that we will have the capability to find signs of life very soon with the launch of the James Webb Space Telescope. But whether we find life, that really depends on what's out there. You know, if every planet has life, if life is extremely common, life that makes gases, so I, if you want a concrete answer, I could say anywhere between two years and Thirty years, let's say.
14:54 Neil deGrasse Tyson? Okay, so this would be the life, the usable life expectancy of the James Webb Space Telescope.
15:00 Speaker 02 Well, I was putting the James Webb, whose nominal life expectancy is five years, maybe 10. I was thinking of future telescopes beyond the James Webb.
15:08 Neil deGrasse Tyson? Okay, and possibly missions to the icy moons of Jupiter, where there might be life beneath the surface, or even life beneath the surface of Mars, right? I mean, why not?
15:21 Speaker 02 Right, right.
15:21 Neil deGrasse Tyson? You're not looking for that life, but you've got other people, top people, doing that as well.
15:26 Speaker 02 Right.
15:27 Neil deGrasse Tyson? Okay, so we might find life, or definitely know there isn't life as we know it, in the lifetime of this eight-year-old girl.
15:35 Speaker 02 Well, maybe this eight-year-old girl will carry the torch. If all the searches we're doing now are exhausted, maybe she'll be the one to think of the next new idea.
15:44 Neil deGrasse Tyson? Oh, maybe you all aren't clever enough, and we need her to come along and solve all the problems.
15:49 Matt Kirshen? There you go.
16:04 Speaker 03 Hi, I'm Ernie Carducci from Columbus, Ohio. I'm here with my son Ernie because we listen to StarTalk every night and support StarTalk on Patreon.
16:14 Neil deGrasse Tyson? This is StarTalk with Neil deGrasse Tyson.
16:30 Neil deGrasse Tyson? What more do you have, man, of course?
16:32 Matt Kirshen? Also, by the way, we should mention that our guest today isn't the only one with a new book out, and you've got a book based on Cosmic Queries that has a chapter that talks about the search for life.
16:45 Neil deGrasse Tyson? Oh, yes, indeed. So, thanks for mentioning that, because I almost forgot. I probably wouldn't have forgotten by the end, but there's a book called Cosmic Queries. Because this format was so successful, we said, "We've got to do more than just put it out there as a podcast." So, there's a book called Cosmic Queries that takes all the biggest questions, including this one. And much of Sarah's research that informs this field is contained in that chapter. And so, in a celebration of Cosmic Queries as a thing, and the search for life as a subthing of the bigger thing... We've got Sarah Seager. So Sarah, thank you again for being on StarTalk and for checking in for this. So Matt, what do you have for us?
17:29 Matt Kirshen? Well, I've got to do another cosmic query question from another young Patreon listener. This comes from Violetta and Violetta's mom Izzy. Violetta is a 12 and a half year old astrophysic kid here in Birmingham, Alabama.
17:43 Neil deGrasse Tyson? 12 and a half.
17:45 Matt Kirshen? When you're young, those halves are important. And I asked Professor Seager, I want to know, firstly, what exactly are biosignature gases? And secondly, what biosignature gases would Earth give off that would be detectable by extraterrestrial life who might be looking for inhabited planets like ours?
18:03 Neil deGrasse Tyson? Perfect question. Yes, Sarah.
18:05 Matt Kirshen? Or would ETs not need to look for our biosignature gases because our existence would be pretty obvious because, duh, space junk?
18:11 Neil deGrasse Tyson? Hmm.
18:12 Speaker 02 Yes, well, a biosignature gas is a signature of life. It's a gas produced by life that can accumulate in an atmosphere of a planet to a level that we can detect with our telescopes. You know, I love to imagine, you know, there are intelligent aliens on a planet orbiting a nearby star, and they have the kind of space telescopes we're building or hoping to build. They would look at our Earth and they would definitely see a very strong biosignature gas, and that's oxygen. And oxygen fills our atmosphere to 20% by volume. But without plants, without photosynthetic bacteria, we would have literally virtually no oxygen.
18:52 Neil deGrasse Tyson? So if all the plant life went away, you know, walked off the Earth today, how long would it take for our oxygen supply to sort of drop to zero? And why would it drop at all? Why wouldn't it just stay there?
19:04 Speaker 02 Well, we also have bacteria that make oxygen, so I'm not sure, you know, what the division between...
19:10 Neil deGrasse Tyson? So no, no, no, just take away everything that's making oxygen. Take everything away.
19:13 Speaker 02 Yeah.
19:13 Neil deGrasse Tyson? And so now we've got 20% oxygen. What happens to it?
19:17 Speaker 02 Well, what happens to it is oxygen is a highly reactive gas. And it will just react away with other molecules in the atmosphere with lots of things on the surface, with gases coming out of vents and volcanoes. And that oxygen just won't be there.
19:31 Neil deGrasse Tyson? And how about how over how much time would that take? Would it happen like next week or in a year?
19:36 Speaker 02 No, no, it wouldn't happen next week. It probably wouldn't happen in a year. It's probably more like thousands of years.
19:42 Neil deGrasse Tyson? Or more, okay. So we so we if we kill all the life, the oxygen, which life, we can still live out our lives with oxygen. It's subsequent generation will suffocate.
19:52 Speaker 02 Yes, probably we could live without our lives.
19:55 Neil deGrasse Tyson? Okay, so what you're saying is even though this 20% has been stable over the mostly stable, it's not actually a stagnant number because we are constantly producing it and constantly removing it. And it just happens to be balanced at this number. Is that a fair way to say it?
20:13 Speaker 02 That's a fair way to say it.
20:14 Neil deGrasse Tyson? Okay, okay, cool. All right, all right, Matt, give me another one.
20:19 Matt Kirshen? All right, this this comes from Grumsetuff, one word. I hope I'm pronouncing that even close to correctly.
20:26 Neil deGrasse Tyson? Whatever you did, it's better than what Chuck does with names. Chuck can't pronounce anything.
20:30 Matt Kirshen? What is your most optimistic explanation of the Fermi paradox?
20:34 Neil deGrasse Tyson? I like that question.
20:35 Speaker 02 Oh, yeah, I think we all have our favorite answer to that one.
20:37 Neil deGrasse Tyson? Well, tell me what it is first.
20:38 Speaker 02 The Fermi paradox is the idea that if if there is intelligent life that can harness energy and get in spacecraft and journey beyond their planet, that they should have colonized the entire galaxy by now. Because once they can get to one planet and colonize that, they can just keep going. And so the Fermi paradox is summed up by the question, where are they?
21:02 Neil deGrasse Tyson? Hmm, so what you're saying is in the lifetime of the galaxy, it doesn't really take that much time if you're intelligent by our measures to build spacecraft and start traveling to planets, even if you can't travel at the speed of light.
21:16 Speaker 02 Right, right, that over time you would eventually reach planets and and colonize.
21:21 Neil deGrasse Tyson? Okay, so all right, so where are they?
21:23 Speaker 02 Okay, so there's the explanation I think is the real one. And then there's the one that I hope is the real one.
21:26 Neil deGrasse Tyson? Wait, so Matt, Matt, her explanation would be they're already here.
21:32 Speaker 02 I like that one.
21:33 Neil deGrasse Tyson? Yeah, that's the funnest answer, but go on. We don't need to talk about that.
21:39 Speaker 02 So you know, one answer is that it just takes too much energy. Like we as humans, we know now what it takes to get in a spacecraft and go somewhere. That's a lot of resources. So perhaps they're just not, not doing that. There's another answer that the intelligent civilization will unfortunately and inevitably self-destruct. They'll destroy their planet, they'll kill each other, they'll, they won't ever reach.
22:05 Neil deGrasse Tyson? Wouldn't that be the definition of not being intelligent?
22:09 Speaker 02 Yeah, well, it would be. My explanation that I love is I'll put it to you this way. Just imagine an ant, an ant colony in your house, you know, what you might have or your apartment. And the ants, they appear kind of, you know, dumb, but they're somewhat clever, right? Because they have a society and you see them doing like a reconnaissance.
22:30 Neil deGrasse Tyson? But just to be clear, just to make sure we're all on the same page. By ant colony, you mean like a, one of those ant habitat module things where you can see.
22:38 Speaker 02 No, I just mean, it could be, it could be that ant colony habitat, or it could just be the ants like in your house.
22:44 Neil deGrasse Tyson? Oh, just ants in the house, okay.
22:47 Speaker 02 And I don't know if you've ever had this, but you'll see like a few of them kind of looking around and they might come across like a piece of cat food on your counter or something. And then shortly thereafter, you have a huge stream of them and they're all coming to get this cat food in like a little river. Well, you can mess them up if you like wipe away their trail for a moment, they kind of get lost. But I want you to imagine, you know, Neil, Matt, having a conversation with those ants. Like tell them about the universe, tell them about the Hubble Space Telescope and the vastness of, of the number of stars and galaxies.
23:18 Neil deGrasse Tyson? And tell them about calculus and geography.
23:21 Speaker 02 Yes, yes, yes. So what I love to imagine is that these, to these intelligent aliens out there, that we are like the ants. Like why and how would they, they contact us?
23:31 Neil deGrasse Tyson? Okay. So Matt, Sarah's bumming us out. Now we're, first we're insignificant, now we're just plain stupid.
23:37 Matt Kirshen? Well, also I think it is worth pointing out, there are, there are different, I mean, like Sarah was alluding to, there are very different types of intelligence. You know, I've been to university, you've both spent a lot more time in academia, that we've all met people who are incredibly smart in specific ways and otherwise idiots.
23:57 Neil deGrasse Tyson? Okay.
23:58 Matt Kirshen? So, you know, maybe they have the ability to travel across galaxies, but they're not the ability to not shoot themselves within a very short amount of time.
24:04 Neil deGrasse Tyson? So the official answer to the Fermi paradox, where are they? They think we're idiots.
24:13 Speaker 02 Either they think we're idiots or we think they are for having self-destructed before they could get here.
24:17 Neil deGrasse Tyson? Oh, there it is. Touche. Touche. All right. So Matt, give me some more.
24:22 Matt Kirshen? So along the lines of interacting with other civilizations, Eric Gross asks, let's say we discover proof of life, not in our own solar system, but on some distant celestial body. Would there be any meaningful scientific value of the discovery or opportunity to expand upon the knowledge? It may, of course, have broad societal and emotional effects, but would science practitioners have any real hope of gaining more information about life forms that are at a minimum of 4.3 light years from Earth?
24:48 Neil deGrasse Tyson? I love that question. And Matt, who asked it?
24:50 Matt Kirshen? That was Eric Gross.
24:51 Neil deGrasse Tyson? Eric Gross. Okay. Yeah. So Sarah, I love that question because generally when we think of scientific discoveries or advances, we think, okay, in five years or 10 years, engineers will get a hold of it and they'll make some new device and we'll all be living better and differently. And so life's somewhere else that you can't actually have a conversation with. Even if it's intelligent, are you getting secrets from that? I mean, what if you can't? Or can you? Are we missing something here?
25:19 Speaker 02 It's such a great question. I mean, we are so wrapped up in the emotion and the excitement of the journey of exploration and of being the first who can try to find out what's out there. So in a practical sense, not really. I mean, we're not doing this to find anything practical. That said, wouldn't it be amazing if there is life, intelligent life, on the nearest star system four light years away? We could have a very slow conversation.
25:42 Neil deGrasse Tyson? Very slow.
25:43 Speaker 02 But we could imagine.
25:44 Neil deGrasse Tyson? No witty repartee there. Right.
25:47 Speaker 02 Send them a message and, you know, four years later, you'll get their message back and we could exchange ideas about technology. So if we want it to be practical, like, that's probably the most practical avenue.
25:57 Neil deGrasse Tyson? Hmm.
25:59 Neil deGrasse Tyson? But in terms of biology, unless we learn from them through these radio signals, what their sort of biochemistry is like, we wouldn't get to compare DNA, or if they have DNA at all, you wouldn't be able to do any sort of in-situ kind of comparisons to advanced biology on life, I would guess. Is that correct?
26:18 Speaker 02 Right. No, that's correct. That's correct.
26:20 Neil deGrasse Tyson? Yeah, but I don't want to sound like, who was that philosopher 150 years ago? Who said, "The stars, they're just lights on the sky, and we can know, you know, how bright they are in the location, but we will never know what they're made of."
26:34 Speaker 02 Right. And think about this, like, we're just here now. Imagine 1,000 years from now, you know, 10,000 years from now.
26:40 Neil deGrasse Tyson? Right.
26:40 Speaker 02 We may have a way to get to this. Imagine if there's life, intelligent life on that planet, and we do like a sample return. We fly something by, they send something up, we grab it, we, you know, gravitational slingshot around their star, and we come back.
26:54 Neil deGrasse Tyson? Okay. So, all right, I'll just think 1,000 years from now, rather than next week. Okay?
27:02 Matt Kirshen? Well, what you just said, that answer segues quite neatly into this question, which I like. And I'm gonna combine two different questions from what Tom says, who asks, "What forms of communication are most likely to be able to cross between the stars?" And Trumpet Wom, who says, "How do you think we will overcome the language barrier if we ever meet another sentient life form?"
27:26 Neil deGrasse Tyson? I love it. And Sarah, you remember that movie Arrival? So I got in trouble for, and I knew I was gonna get in trouble for saying this. I said, "In the movie Arrival, they brought a physicist and a linguist to try to communicate with the alien, when they should have brought an exobiologist and a cryptographer." And I got so much shit from the linguists out there. Because this is their one time to appear in a movie, and there I am, just dissing them. But what is your opinion about how we would actually communicate?
27:58 Speaker 02 I mean, I love that movie. I love the concept that it may be so difficult that we may, we may not find a way to communicate.
28:06 Neil deGrasse Tyson? Okay, so Matt, she just swept that one under the rug. You hear that? Matt, she...
28:12 Speaker 02 Neil doesn't like any of my answers, but...
28:14 Neil deGrasse Tyson? She's sweeping it. I don't know how big her rug is in the middle. But how about mathematics? How about symbology? How about? I mean.
28:24 Speaker 02 I like all those answers.
28:26 Neil deGrasse Tyson? You're OK with them or not?
28:27 Speaker 02 I like it. I like it. It would have to be something that is fundamental in a very mathematical way. I agree with that.
28:34 Neil deGrasse Tyson? Because math apparently applies across the universe. So if they discover something that is cosmic, universal, it'll have to be the cosmic, universal things we discovered as well, I presume.
28:44 Speaker 02 Right.
28:44 Neil deGrasse Tyson? So I wonder. So I think one of our greatest triumphs is the periodic table of elements. If we can like show that to them and see if they have a version of it. Because there'd be a lot of pantomiming initially, I would guess.
28:56 Speaker 02 Yes.
28:56 Neil deGrasse Tyson? Before anybody actually communicated. So it is funny that, you know, aliens often just spoke English, you know, in the movies.
29:05 Speaker 02 Right, right. That's why The Arrival is so great. It's such a great movie. The first time they have these beings that have no way to really, really interact with us.
29:13 Neil deGrasse Tyson? Right, right, right. So Matt, give me one more question before we wrap up this middle segment.
29:19 Matt Kirshen? I will do. And for the people who are watching the video rather than just the audio, I apologize for the other life form that keeps walking across my lap while we're trying to record. I have no way of communicating with him. Well, so I'm also going to combine these two questions because they're in similar themes. So Rob Carter asks, when searching for life on other planets, is there a priority of what type of life you look for? For example, would a land-based life form take precedence over an aquatic species and so forth? And then Jonathan R. Brown asks, carbon-based life on Earth developed in the oceans and diversified exponentially from there, spreading to land and beyond. Life on other worlds may develop from a different elemental base and begin on land or in other environments. Could ET life be too alien for us to recognize as life? And what is the baseline?
30:31 Neil deGrasse Tyson? All right, so Matt, we left off with a brilliant pair of questions. Tell me the two names, who asked it again?
30:37 Matt Kirshen? Yes, that was Rob Carter and Jonathan R. Brown, and they were both asking about the types of life forms that you might find on other planets, whether land-based, aquatic, and so on, and whether we'd even be able to recognize those things as life.
30:49 Neil deGrasse Tyson? And must they be based on carbon?
30:51 Matt Kirshen? They're too different from us.
30:52 Speaker 02 Yes, well, we won't have a chance to see that life. We'll only see what life does, we'll see the byproducts of that life.
30:59 Neil deGrasse Tyson? Because the telescopes aren't good enough yet.
31:00 Speaker 02 Right, right, we'll only see the planet far away, we won't even see it in some cases, it'll be a pale blue dot, or we'll just see its atmosphere as backlit by its star, so we won't see the animals.
31:09 Neil deGrasse Tyson? So the point is, when you study the chemistry of the atmosphere, it's a remarkable feat of observational astrophysics, because the light from the star behind it passes through the transparent atmosphere, and then the molecules leave their fingerprint, and that's what you're studying.
31:26 Speaker 02 Right, that's the way we're studying exoplanet atmospheres today.
31:29 Neil deGrasse Tyson? So we're a long way off from you watching something wave to you in the telescope lens.
31:34 Speaker 02 We are, but, you know, funnily enough, it doesn't stop us...
31:36 Neil deGrasse Tyson? You got an answer there?
31:37 Speaker 02 Yeah, I do have an answer.
31:38 Neil deGrasse Tyson? That's good.
31:39 Speaker 02 Well, I was gonna say, it doesn't stop us from speculating about what life might be like. I want you to just imagine for a moment, because there are... Exoplanets are so diverse, they're different masses and sizes, and we're imagining their atmospheres are all different. Imagine a planet where the atmosphere is so massive and heavy, that it's a similar density to water. So imagine you have a water ocean, and above that is a heavy, dense atmosphere. You could imagine things like flying fish, that can just move between the atmosphere and the water, because it's the same density.
32:10 Neil deGrasse Tyson? Wow.
32:12 Speaker 02 Yeah, we love to imagine a planet that is somewhat dark, because of a massive atmosphere. And we like to imagine this idea of birds with giant wings, that are photosynthetic, that the wings are like giant plant leaves, they can fly up to where there is sunlight. And gain energy from the sun that way.
32:30 Neil deGrasse Tyson? Sarah, that reminds me, some science fiction writer, forgive me for not remembering, there was a punchline in it where the aliens come to the earth, they see what we all do here, and then they return to their home planet and they report on what they discovered. And they said, "They're all made of meat."
32:49 Neil deGrasse Tyson? And because we basically eat each other, right? Life eats other life, unless you're a plant, in which case you eat sunlight.
32:57 Speaker 02 Right, wow.
32:58 Neil deGrasse Tyson? So, I mean, just think about that. So if you are a bird that has photosynthetic wings, then to eat, like you just said, you just go to an altitude where you get the sunlight and then come back down, and you're not killing anything for your survival.
33:13 Matt Kirshen? But then you would presumably be prey for whatever is in the lower levels, because they aren't accessing that sunlight.
33:20 Neil deGrasse Tyson? You'd want to make sure they're photosynthetic too.
33:24 Neil deGrasse Tyson? But imagine a whole world where that's the case, and they come visit us, and we have all these slaughterhouses, and not just us, other animals eat other animals. And this would look like a really bloody nasty place to them. I mean, you guys ever think about that?
33:38 Speaker 02 No, no, but it sounds pretty scary.
33:42 Neil deGrasse Tyson? Okay, so tell me also about a carbon-based life. How important is that?
33:46 Matt Kirshen? Yeah, because, well, Sam Couch actually asked this specifically while we're doing that. Sam asked, "Is it possible to have life elsewhere that is not carbon-based? And if so, what would that look like compared to carbon-based life? And what would be the requirements for that life to survive?"
34:00 Speaker 02 Yeah, there really hasn't been a lot of solid work done in that area. It's really hard to construct, you know, a biochemistry of like a completely different type of life out there. We're not sure if silicon-based life is even really possible. We think silicon, you know, a lot of our silicon here on Earth, for example, it's locked away into rocks, and there's just not a lot of silicon. We think silicon compounds are often, they dissolve in water too easily. So I think the jury is still out on that one.
34:28 Neil deGrasse Tyson? Okay, so even though silicon makes the same families of molecules as carbon does, because they're top and bottom to each other on the periodic table, as we learned in high school chemistry, that they'll all make the same kinds of molecules. But you're saying the other properties of silicon molecules make them wholly different from what carbon is giving us.
34:49 Speaker 02 Yes, yes.
34:50 Neil deGrasse Tyson? So our search for life is justifiably carbon-based, not to put words in your mouth, but that's kind of what you're saying.
34:56 Speaker 02 Yeah, you said it well. That's right.
34:58 Neil deGrasse Tyson? Okay. Matt, did she sweep any of that under the rug?
35:00 Matt Kirshen? No, I think that rug is fully lifted and the items underneath are exposed to the elements.
35:08 Neil deGrasse Tyson? All right. So Matt, keep going.
35:09 Matt Kirshen? All right, okay. This one's pitting host against guest here. Josh V. asks, "Dr. Tyson has spoken in the past StarTalk episodes about the idea of Goldilocks zones being antiquated at best and possibly the wrong approach to searching for life. What is Professor Seager's opinion on the use and definition of Goldilocks zones as it applies to what galactic locations are prioritized in searching the vast cosmos?"
35:33 Speaker 02 Wow, actually, this is one where Neil and I agree, actually. So just to go into some detail, the habitable zone, it's a good construct, the Goldilocks zone. It helps us think of where we should be looking for planets. But in reality, I think it really depends on the individual planet. Like, I want you to imagine a planet that, instead of having an atmosphere like ours that is mostly nitrogen and it has a good amount of oxygen, imagine a planet that has a hydrogen atmosphere, dominated by hydrogen. Did you know hydrogen is a nasty, potent greenhouse gas, way worse than any of the gases we have on our planet Earth? So a planet with hydrogen, it turns out, it could still be the right temperature, far
36:15 Speaker 02 outside to what we think of as this traditional Goldilocks zone, because it has such a powerful greenhouse.
36:20 Neil deGrasse Tyson? And they wouldn't call it nasty. They would be thankful for it.
36:22 Speaker 02 They would need it, or their planet would be too cold. Right, right. So I like to think of habitability concept as being, you know, planet-independent, not your location in the galaxy, or your location in your own planetary system, but dependent on the properties of the planet.
36:36 Neil deGrasse Tyson? So that's an enlightened, modern view of the concept of a zone. So the zone is not a... It's a virtual zone, in that sense. Because it can be in places that are not just in the narrow-minded swath that's around the sun. So I hadn't thought about these other kinds of Goldilocks zones you're referencing. So, yeah. And for all we know, even the definitions we've come up with now, 20, 30 years from now, Carrie and Violetta, the eight-year-olds or the 12-year-olds listening to this, in their day, they might look back at our definition, broadened definition of a
37:15 Neil deGrasse Tyson? Goldilocks zone, and say, what do they know? Because for all we know, there could be like life inside of volcanoes or something. I mean, who knows? But
37:25 Speaker 02 Right, right. And we haven't observed any rocky exoplanet atmospheres yet. We're just beginning, so.
37:30 Neil deGrasse Tyson? Right, right, right. Okay. Very good. Very good. So what I want to do now is go into a semi-lightning round. And so Sarah, pretend you're on the evening news, and the whole interview is going to last just a couple of minutes. And so this is your soundbite quiz, can you give us a soundbite? You've been very good in this program up so far. So I think you'll come out in flying colors. So Matt, let's see how many questions we can squeeze in before we call it a day.
37:56 Matt Kirshen? We've actually got a few questions left, if that's...
37:58 Neil deGrasse Tyson? Okay.
37:59 Matt Kirshen? I think I know the answer to this one. But Andrew Gendrow asks, "My question is about the probability of life in the universe finding each other. If we think of the universe as infinite and the axis of time as infinite, does it stand to reason that the probability of life in different areas of the universe finding each other on both axes, time and space, approaches zero?"
38:18 Neil deGrasse Tyson? Ooh, I like that.
38:19 Matt Kirshen? My guess is no. But I want to hear from the scientists.
38:24 Speaker 02 Okay, I didn't totally get that, the last part of that. So he's saying, if everything's infinite, life should find each other. So why is he saying...
38:30 Matt Kirshen? Shouldn't find each other. I think the question is, if we're dealing with an infinite universe and a finite amount of life, would that not be so far apart from each other that it couldn't find each other?
38:42 Neil deGrasse Tyson? No, he added another dimension. Let's say life is there and we're here, and we go there and we find them. Okay? If space is infinite, that reduces the likelihood that they're just going to be there. They're going to be probably much farther away from us. That's the first axis on this. The other axis is... Maybe the life is there now, but they're not going to be there in 100 years. So you have to intersect not only in time, but in place. And if both the time axis and the place axis are infinite, what hope do we have of ever making contact? I think I got his question.
39:19 Speaker 02 I think you got it. I think that is the question, yes. You got it, yes, yes. It really all depends on how common life is. If life is rare, then yes, that question is and answer is valid. But we all want to believe that we will, we see. But we see the ingredients for life everywhere. And so we have every reason to hope that on each rocky planet, that's the right temperature, that there's a chance for life there. In which case, life is, yeah.
39:44 Neil deGrasse Tyson? Okay, and but but in terms of how how far we've actually searched, my favorite reference there is an analogy given by Jill Tarter of the SETI Institute. And I've, it was so good, I've given this 100 times since then. And I, we got her to say it on StarTalk, so we, we have it bronzed in our.
40:04 Speaker 02 I know, I know what you're gonna say.
40:05 Neil deGrasse Tyson? In our archives. It's, you can ask how much of the universe have we searched? Before we start saying, there's no life here. And if you look at all the parameter space, time, space, frequency of bandwidth, right? You could be trying to say hi in one frequency, and they're trying to say hi in another frequency, and there's ships passing in the night. And you both conclude that there is no sign of intelligent life. So she said, it's like going up to the ocean, scooping a cup, an empty cup, filling it with ocean water, looking at it and say, there are no whales in the ocean. So in terms of how much total volume that of space, time, frequency is searchable.
40:49 Neil deGrasse Tyson? And so that was depressing, but fascinating at the same time for me.
40:52 Speaker 02 Right, right. But at the same time, now I'm going to turn the tables and do the opposite of trashing all the the comments. Like, if you're scooping up that one glass of water, surely there is some kind of life in there.
41:06 Neil deGrasse Tyson? Mmm.
41:07 Speaker 02 So we're thinking that we can look at the nearest stars and the nearest planets, and that the ingredients for life are everywhere, and that they should come together often enough that we have a chance of finding signs of life.
41:18 Neil deGrasse Tyson? Excellent, excellent. So that's like taking a scoop of anywhere soil on Earth, there's gonna be life in it, no matter what.
41:25 Speaker 02 Right, or any air, air parcel.
41:26 Neil deGrasse Tyson? Even air, very cool, very cool. Matt, let's slip in a couple more questions.
41:30 Matt Kirshen? All right, John David Newman says, "Is it possible that the galaxies we observe relatively easily are less likely to have life than the dwarf galaxies or wandering stars in deep space which are more difficult to see? Could wandering stars or dwarf galaxies in deep space be less threatening to life?"
41:45 Speaker 02 Well, at the moment, we're only able to observe the very nearest stars. We can't see other galaxies. So that question's out of our purview at the moment. However, each star is fairly isolated, and each star has its own planetary system as far as we can tell, so it shouldn't matter which galaxy the planet is in in relation to whether life is there or not.
42:06 Neil deGrasse Tyson? And we see the same kinds of stars in most galaxies. There are differences, of course, but that repeats enough, so I agree with you. We'll be perfectly happy searching stars in our own galaxy without having to go to others just to wonder if it's different. But another point implicit there is there are some galaxies that have very rocking active nuclei with very deadly radiation coming out, and it could be that some galaxies are hostile to the formation of complex molecules, and more peaceful galaxies, like the dwarf galaxies, that they may be more hospitable. I mean, we don't really know this yet. And I agree, Sarah, there's still much more searching to go before we start creating a galactic model for what life would or should be like.
42:51 Neil deGrasse Tyson? Let's get one more question, Matt.
42:53 Matt Kirshen? All right, well, I'm gonna combine these two then. I'm really on a combining kick today, because these are both quite philosophical. Jet Thomas asks, "We as a species love to stimulate our senses by watching movies, listening to music, telling stories and more." Assuming an alien civilization is interested in leisure, could we hypothesize what a stimulation of different senses would look like outside of our familiar five and look for evidence of such things? And then Chris Hampton says, what effect do you think the discovery of alien life would have on society? Would borders eventually dissipate and self-identification move from Russian, American, et cetera, to Earthling? How long would the initial pandemonium last? So, music, society, culture, and art. How would everything change?
43:32 Neil deGrasse Tyson? In one soundbite, Sarah.
43:34 Speaker 02 I think I was going to ask Neil for that because Neil is so articulate and good at speaking. I think you should take a crack at it.
43:40 Neil deGrasse Tyson? I'll take a quick crack at it. It is interesting. When you find something that's more other than you are from among yourselves, it does act as a kind of binding force. And sometimes for the good, sometimes not. But I had hoped that we would have had this kind of binding force in the face of battling COVID. COVID was like an alien, then it doesn't care what your skin color is, or your gender, or gender expression. It doesn't care, it'll infect you. And that would be a good place to band together and fight it. And we failed that test. So I wish I had more confidence than I currently do in how we would react collectively as a
44:25 Neil deGrasse Tyson? species to an alien, be they friendly or hostile. And the other question was what?
44:31 Matt Kirshen? It was about what kind of version of stories and art and music and
44:35 Neil deGrasse Tyson? Oh, yeah.
44:36 Matt Kirshen? Alien civilization have and how would it differ from ours?
44:39 Neil deGrasse Tyson? Sarah, do you guys?
44:40 Matt Kirshen? Or how would we interact with it?
44:41 Neil deGrasse Tyson? Sarah, do you guys think much about the senses that an alien might have?
44:46 Speaker 02 No.
44:50 Matt Kirshen? I mean, is that something that you could look for, look for evidence of, or ways that they could have changed their environment to accommodate the different ways that they that they interact with each other?
45:00 Speaker 02 No. I mean, if you think about it for a moment, our oxygen on Earth, life on Earth bacteria, cyanobacteria, you know, billions of years ago, they re-engineered our atmosphere. They completely changed our atmosphere so it was unrecognizable. So we can see giant things like that. But small things like that animals do or that aliens would do, those are out of our possibility for now.
45:24 Neil deGrasse Tyson? Yeah, but you're being like straight scientist there. But now let me ask you, Sarah Seager, the human being who watches science fiction movies, what?
45:33 Neil deGrasse Tyson? Can you imagine, if an alien had another sense, what might it be?
45:39 Speaker 02 Yeah, that's a tough one. I don't have a good answer for that.
45:42 Neil deGrasse Tyson? I can take any answer. It doesn't have to be good.
45:44 Speaker 02 Well, sometimes I do like to think about our own planet Earth and all the intelligent life here, you know, like the dolphins and octopus. And there's a lot of creatures here that we think are highly intelligent. And so I do like to think about how they interact with each other, what signs they give each other.
46:01 Neil deGrasse Tyson? My favorite New Yorker comic, and we've got to end, was there were two dolphins swimming together, and they're looking up at two humans talking to each other, looking out of the water, and they see them. And one dolphin says to the other, "They face each other and make sounds, but it's not clear that they're actually communicating."
46:21 Neil deGrasse Tyson? Dolphin with brains bigger than ours. Sarah, it's been a delight to have you on. And we neglected to even mention that you were co-author on the recent discovery of phosphine, a molecule in the upper atmosphere of Venus, a possible product of life. I know that that result is still getting contested, but it's fun to watch science at its best when ideas come forth and people try to explain it in multiple ways. So just good luck on that. It was great to see you active in that. And in your part memoir, "The Smallest Lights in the Universe", it's a delight to see that contains a firsthand account, not only of your life, but the birth of an entire cottage industry in our beloved field of astrophysics,
47:06 Neil deGrasse Tyson? the search for exoplanets and the search for life itself. So great to have you on, and good luck with that book.
47:10 Speaker 02 Thank you. Thanks for having me.
47:11 Neil deGrasse Tyson? All right. And Matt, always good to have you, man.
47:13 Matt Kirshen? Oh, it's a pleasure. Thanks for having me.
47:15 Neil deGrasse Tyson? And we'll look for you on Probably Science.
47:17 Matt Kirshen? Yes, please.
47:17 Neil deGrasse Tyson? I got it straight.
47:18 Matt Kirshen? In one. And also your book as well, Neil. We've got to give that another plug.
47:21 Neil deGrasse Tyson? Oh, so another plug for Cosmic Queries. If you like this format, and if you're listening, you probably do, because it's one of our most popular, we just put it all in one book. It's got the deepest questions, what is life? And what is the universe made of? And how did it begin? How will it end? And are there multiverses? And so we're very proud of that book as a StarTalk community, because a lot of it has been inspired by shows like this, where you write in and ask your deepest questions. And that inspired us to... Put the book out there and it's a product of the StarTalk family. This has been StarTalk Cosmic Queries. I'm Neil deGrasse Tyson, your personal astrophysicist. As always, keep looking up.
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