Cosmic Queries – Life on Exoplanets with Sara Seager

Summary

StarTalk Radio – Episode Summary: "Cosmic Queries – Life on Exoplanets with Sara Seager"

Introduction

In this captivating episode of StarTalk Radio, astrophysicist and Hayden Planetarium Director Neil deGrasse Tyson teams up with co-host Matt Kirschen to delve deep into the enigmatic quest for extraterrestrial life. Joining them is the esteemed Sara Seager, a professor of Aeronautics and Astronautics, Physics, and Planetary Science at MIT, renowned for her pioneering work in exoplanet research and the search for life beyond Earth.

Guest Introduction

Neil introduces Sara Seager, highlighting her multidisciplinary expertise. “Exoplanets and the Search for life is an incredibly interdisciplinary topic that draws upon all different fields,” Sara asserts (02:48), emphasizing the collaborative nature of this scientific frontier.

Discussion Highlights

1. The Significance of Exoplanets in the Search for Life

   Neil and Sara explore the intrinsic link between exoplanet discovery and the search for life. Sara acknowledges humanity's inherent “terracentric” bias but stresses the necessity of focusing on planets where “elements concentrate,” making them potential cradles for life (03:23).

2. Biases in Exoplanet Research

   The conversation turns to the initial focus on "hot Jupiters" — massive gas giants orbiting close to their stars, which dominated early exoplanet discoveries. Sara notes, “We are slowly making ourselves less and less precious, less and less special,” as the diversity of exoplanets challenges our Earth-centric views (04:37).

3. Atmospheric Biosignatures and Detecting Life

   Sara elaborates on the concept of biosignature gases, such as oxygen and methane, which could indicate biological activity. However, she cautions that these gases are necessary but insufficient to confirm life, drawing an analogy to a forensic crime scene where “you have to distinguish between blood that was caused by the crime and blood that was just previously existing” (13:54).

4. Challenges of the Fermi Paradox

   Addressing the Fermi Paradox—the question of why we haven't yet encountered intelligent extraterrestrial life—Sara offers multiple explanations. One optimistic view she shares involves the possibility that other civilizations may perceive us as insignificant, similar to how ants might view humans (24:04). She also discusses the likelihood that intelligent civilizations often self-destruct before achieving interstellar communication or travel (24:17).

5. Communication with Alien Civilizations

   The trio contemplates the complexities of interstellar communication. Sara supports the idea that mathematics and symbology could serve as universal languages for extraterrestrial dialogues, acknowledging the immense challenges posed by differences in biochemistry and sensory perceptions (30:46).

6. Alternative Biochemistries and Recognizing Alien Life

   When questioned about the possibility of non-carbon-based life, Sara admits that while silicon-based life remains a topic of speculation, the lack of silicon's versatile chemistry compared to carbon makes such life forms unlikely with our current understanding (38:11). This underscores the justified focus on carbon-based life in our search.

7. Evolving Concepts of Habitable Zones

   Sara critiques the traditional Goldilocks Zone concept, advocating for a more planet-dependent approach to habitability. She illustrates how planetary atmospheres, such as those dominated by hydrogen, could maintain habitable temperatures far outside conventional habitable zones due to potent greenhouse effects (39:44).

8. Societal Implications of Discovering Alien Life

   In a reflective moment, Neil speculates on how humanity might react to discovering alien life, drawing parallels to global responses to pandemics like COVID-19. He expresses skepticism about whether such a discovery would unify humanity or exacerbate existing divisions (48:43). Sara adds that while the discovery would have profound societal impacts, the scientific community would continue to push the boundaries of understanding regardless of public sentiment.

Listener Q&A

Throughout the episode, Neil and Matt address insightful questions from listeners, including:

• Timeframe for Discovering Extraterrestrial Life: To an 8-year-old listener, Sara estimates the possibility of detecting life within “two years and 30 years” with advancements like the James Webb Space Telescope (15:15).

• Biosignature Gases on Earth: Sara explains that Earth's atmosphere's oxygen levels are maintained by continuous biological processes, and if life ceased, oxygen would react away over thousands of years, highlighting the delicate balance maintained by life (21:29).

• Probability of Life Finding Each Other in an Infinite Universe: Sara remains hopeful that the ubiquity of life's building blocks increases the chances of encounters, despite the vastness of space and time (43:54).

• Types of Alien Life and Recognition Challenges: Sara emphasizes the difficulties in recognizing life forms that deviate significantly from Earth's carbon-based biology, reinforcing the focus on observable atmospheric signs (35:12).

Conclusion

As the episode wraps up, Neil commends Sara for her contributions to the field and her memoir, “The Smallest Lights in the Universe,” which chronicles her journey and the evolution of exoplanet research. The discussion underscores the intricate interplay between scientific discovery, inherent biases, and the profound implications of potentially finding life beyond Earth.

“Keep looking up,” Neil concludes, encapsulating the spirit of exploration and curiosity that drives humanity’s quest to understand its place in the cosmos.

Notable Quotes

• Sara Seager on Exoplanet Bias: “We do. I mean, we're definitely terracentric, we definitely are narrow minded...” (03:23)

• On Biosignature Gases: “It's a signature of life. It's a gas produced by life that can accumulate in an atmosphere...” (20:42)

• Fermi Paradox Optimism: “...we have every reason to hope that on each rocky planet that's the right temperature, that there's a chance for life there...” (43:54)

• On Communication: “It would have to be something that is fundamental in a very mathematical way.” (31:05)

This episode offers a profound exploration of the scientific, philosophical, and societal dimensions of the search for extraterrestrial life, making it a must-listen for enthusiasts eager to understand the complexities and hopes embedded in this cosmic quest.

Transcript

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[Neil DeGrasse Tyson]

Hey, Start Talkins. Neil here. You're about to listen to an episode specially drawn from our archives to serve your cosmic curiosities. Check it out. Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. 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 is my co host Matt Kirschen.

[Matt Kirschen]

Matt, hey. Hey, Neil, how you doing?

[Neil DeGrasse Tyson]

I spent all day yesterday trying to memorize the name of your podcast. It's probably science. Did I get it right?

[Matt Kirschen]

It is always mangle it for another variant. But thank you.

[Neil DeGrasse Tyson]

I stumbled in my efforts there. I found a podcast called Sometimes or Mostly Science. It's a whole other podcast.

[Matt Kirschen]

Oh, we hate them. No, we've got a running rivalry with them.

[Neil DeGrasse Tyson]

It's going to be totally have rivalries. I got to make sure I get your stuff right.

[Matt Kirschen]

Probably it's going to come to violence at some point. Probably violence.

[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 Sara Seger. Sarah, welcome to StarTalk.

[Sara Seager]

Thanks for having me today.

[Neil DeGrasse Tyson]

Yeah. So Sarah, let me get your full title up here. So you're a professor of Aeronautics and Astronautics, Physics and Planetary Science at mit. Is that. No, they left out a few categories.

[Sara Seager]

No, no, no. It's because exoplanets and the Search for life is an incredibly interdisciplinary topic that draws upon all different fields.

[Neil DeGrasse Tyson]

Excellent. But between you and me, can I call. You're a planetary scientist, right? That's really.

[Sara Seager]

Yes, yes. I mean, my home is really in astrophysics, so you could call me an astrophysicist or a planetary scientist or both.

[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? They go together. But is that part of our bias?

[Sara Seager]

Not necessarily. We do. I mean, we're definitely terracentric, we definitely are narrow minded, but at the same time. 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 hard to imagine ingredients just concentrating in the vastness and that low density of outer space.

[Neil DeGrasse Tyson]

Okay, so this concentration thing I think is under celebrated out there. I mean, in the public, they have people. We take it for granted that we have rocks and buildings and mountains and people. And in our greater universe, nothing is together. It's mostly empty. And where it's not mostly empty, it's highly rarefied. And so planets are really special places.

[Sara Seager]

Is that fair? Very special. Because they do concentrate complex molecules. They concentrate elements, nutrients and everything we need.

[Matt Kirschen]

Am I right in thinking they are substantially less special or at least less rare than we thought they were even five, ten years ago?

[Sara Seager]

Yes, actually, we are slowly making ourselves less and less precious, less and less special.

[Neil DeGrasse Tyson]

No, Sarah, it's okay to know that you're not just supposed to tell people that.

[Matt Kirschen]

I think that's nice about science. I like the fact that science is sort of switch between going, you're incredibly special and you're not special.

[Sara Seager]

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.

[Neil DeGrasse Tyson]

I think I've heard, is it Andrew describe this sequence. Some combination of her 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. But in either case, the Location was unique. I think about it.

[Matt Kirschen]

So in his mind, we're like the plug hole of the universe. We're sort of the drain.

[Neil DeGrasse Tyson]

So, Sarah, 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?

[Sara Seager]

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.

[Neil DeGrasse Tyson]

Do you like the dog being distracted by the squirrel? You know, squirrel? Yeah, you can't keep it. But when you started out in the late 90s, we 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 it seems to me you were there at the birth of this, if not having birthed it yourself.

[Sara Seager]

Yes, and in fact. But just to go back even further, before my time, perhaps even before yours, but in the decades past, since the.

[Matt Kirschen]

Alien, even before Neil, there is no such thing.

[Sara Seager]

No. Okay. Well, you know what's interesting is if you look back, like even 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, 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. And 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 Earth, then switching gears to the hot giant planets. And so the thought of finding Earth in life, it was kind of always there in the background, even though it might have been a bit of a stretch.

[Neil DeGrasse Tyson]

And just to be clear, the. 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 we. And they're hot because why?

[Sara Seager]

Because they're very close to the star. So close to the star that as heated by the star, they're just hot.

[Neil DeGrasse Tyson]

Okay, 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.

[Sara Seager]

Right, right. We always expected to find a Jupiter where our Jupiter is, which is five times further from our sun than Earth is. And instead we found Jupiter mass objects within a few day period orbits of the star.

[Neil DeGrasse Tyson]

So even our bias, which shows up every day in race relations and sexism, it even shows up in astrophysics, just.

[Sara Seager]

It did, yeah. And the funny thing is, just to take that a level further, when 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's 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.

[Neil DeGrasse Tyson]

Okay, so they're not only. So they're big Jupiters that don't look anything like Jupiter, that's what you're saying.

[Sara Seager]

Like, I mean, yes and no. They don't appear like their atmospheres aren't like Jupiter, but they're kind of bulk composition. They're mostly made of hydrogen and helium. That part's the same.

[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 got to start knocking on the doors of biologists. So when did all that happen?

[Sara Seager]

Remarkably, 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, D.C. and it's quite interdisciplinary there already. And they were already part of working on the somewhat new field back then of astrobiology. So I started 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.

[Neil DeGrasse Tyson]

Yeah, so you need the coffee lounges between, at the intersections of departments, because otherwise we just live in our stovepipes and discoveries go unattended to.

[Sara Seager]

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 collaborators.

[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 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.

[Sara Seager]

Thanks.

[Neil DeGrasse Tyson]

Yeah. So let's get straight. Let's get straight to this.

[Sara Seager]

What is life, you know, in exoplanets? We have a good excuse for completely avoiding that question. And we do. We do. I'll run it by you. I'll run it by you.

[Neil DeGrasse Tyson]

All right.

[Sara Seager]

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 gonna 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.

[Neil DeGrasse Tyson]

And you sweep it under the rug because you can't do anything about that question anyway.

[Sara Seager]

We can't do anything about it. And it's just a question that no one wants to agree on what the answer is.

[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.

[Sara Seager]

That's right.

[Neil DeGrasse Tyson]

Not to equilibrate your study with the study of feces.

[Sara Seager]

And actually, Neil, that has never been done before. So that is brand new.

[Neil DeGrasse Tyson]

That's a brand new analogy.

[Matt Kirschen]

So you're saying atmospheres on planets are kind of the animal remains of the galaxy.

[Neil DeGrasse Tyson]

Well, the gaseous effluences, I guess.

[Sara Seager]

Yes. Actually, that's a great way to look at it.

[Neil DeGrasse Tyson]

Yep. 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. How what you. Yeah, why?

[Sara Seager]

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?

[Neil DeGrasse Tyson]

So the gases you list that are the products of life are necessary but insufficient to prove that there's life.

[Sara Seager]

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.

[Matt Kirschen]

So in forensic crime scene terms, you sort of gotta distinguish between blood that was caused by the crime and blood that was just previously existing. Sort of decorative blood in that room.

[Neil DeGrasse Tyson]

Precisely.

[Matt Kirschen]

Just blood that someone had put there that would just naturally be there on the walls in a slabby.

[Neil DeGrasse Tyson]

Yeah, the normal blood that. That exists in the room. I'm sure Sarah is gonna put that analogy in her next research paper.

[Matt Kirschen]

Yeah, just add an equation and that's all science is, right.

[Neil DeGrasse Tyson]

Yeah, it's in an equation. It's legit.

[Matt Kirschen]

Yeah.

[Sara Seager]

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.

[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.

[Matt Kirschen]

Okay, great. Well, this one, I love the questions that come from our younger listeners. This one comes from Carrie Jenkins, an 8 year old fan.

[Neil DeGrasse Tyson]

8.

[Matt Kirschen]

How long. I know. How long do you think it'll take for us to find other life in the universe?

[Neil DeGrasse Tyson]

Yeah. How close are we, Sarah? How many more years? What do we got here?

[Sara Seager]

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 if you want a concrete answer, I could say anywhere between two years and 30 years, let's say.

[Neil DeGrasse Tyson]

Okay, so this would be the usable life expectancy of the James Webb Space Telescope.

[Sara Seager]

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.

[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?

[Sara Seager]

Right? Right.

[Neil DeGrasse Tyson]

You're not looking for that life, but you got other people, top people doing that as well.

[Sara Seager]

Right?

[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.

[Sara Seager]

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.

[Neil DeGrasse Tyson]

Oh. Ooh. Maybe you all aren't clever enough and we need her to come along and solve all the problems.

[Sara Seager]

Okay, there you.

[Neil DeGrasse Tyson]

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[Neil DeGrasse Tyson]

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.

[Sara Seager]

This is StarTalk with Neil DeGrasse Tyson.

[Neil DeGrasse Tyson]

What more do you have, Matt, for us?

[Matt Kirschen]

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.

[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 sub thing 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?

[Matt Kirschen]

Well, I've got to do another cosmic query question from another young Patreon listener. This comes from Violetta and Violetta's mum, Izzy. Violetta is a 12½ year old astrophysica here in Birmingham, Alabama.

[Neil DeGrasse Tyson]

12 and a half?

[Matt Kirschen]

When you're young, those halves are important. And I asked Professor Sega, 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?

[Neil DeGrasse Tyson]

Perfect question. Yes, Sarah, what do you want?

[Matt Kirschen]

Or would ETs not need to look for our biosignature gases? Because our existence would be pretty obvious because duh, space junk.

[Sara Seager]

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. I love to imagine there are intelligent aliens on a planet orbiting a nearby star and they have the 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. Oxygen fills our atmosphere to 20% by volume. But without plants, without photosynthetic bacteria, we would have literally Virtually no oxygen.

[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?

[Sara Seager]

Well, we also have bacteria that make oxygen. So I'm not sure, you know, what the division between.

[Neil DeGrasse Tyson]

So. No, no, no, just take away everything that's making oxygen. Take everything away. And so now we've got 20% oxygen. What happens to it?

[Sara Seager]

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.

[Neil DeGrasse Tyson]

How about, how much time would that take? Would it happen like next week or in a year?

[Sara Seager]

No, no, it wouldn't happen next week. It probably wouldn't happen in a year. It's probably more like thousands of years or more.

[Neil DeGrasse Tyson]

Okay. If we kill all the life, the oxygen producing life, we can still live out our lives with oxygen. Subsequent generations will suffocate.

[Sara Seager]

Yes, probably. We could live out our lives.

[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?

[Sara Seager]

That's a fair way to say it.

[Neil DeGrasse Tyson]

Okay. Okay, cool. All right. All right, Matt, give me another one.

[Matt Kirschen]

All right. This comes from Grumstuff. All one word. I hope I'm pronouncing that even close to correctly. What is.

[Neil DeGrasse Tyson]

Whatever you did, it's better than what Chuck does with names. Chuck can't pronounce anything.

[Matt Kirschen]

What is your most optimistic explanation of the Fermi paradox?

[Neil DeGrasse Tyson]

I like that question.

[Sara Seager]

Oh, yeah, I think we all have our favorite answer to that one.

[Neil DeGrasse Tyson]

Well, tell me what it is first.

[Sara Seager]

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?

[Neil DeGrasse Tyson]

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.

[Sara Seager]

Right, right. That over time you would eventually reach planets and colonize.

[Neil DeGrasse Tyson]

Okay, so, all right, so where are they?

[Sara Seager]

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.

[Neil DeGrasse Tyson]

Wait, wait, so, Matt, Matt. Her explanation would be. They're already here.

[Sara Seager]

I like that one.

[Neil DeGrasse Tyson]

Yeah, that's the funnest answer. But go on, shut up.

[Matt Kirschen]

We're not meant to.

[Sara Seager]

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.

[Neil DeGrasse Tyson]

Wouldn't that be the definition of not being intelligent?

[Sara Seager]

Yeah, well, it would be. My explanation that I love is. I'll put it to you this way. Just imagine an ant colony in your house, you know, which 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.

[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 one of those ant habitat module things where you can see.

[Sara Seager]

No, I just mean it could be that ant colony habitat or it could just be the ants, like, in your house. Like you might have ants in the house. 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 the number of.

[Neil DeGrasse Tyson]

Stars and galaxies, and tell them about calculus and geography.

[Sara Seager]

Yes, yes, yes. So what I love to imagine is that to these intelligent aliens out there, that we are like the ants, like, why? And how would they contact us?

[Neil DeGrasse Tyson]

Okay, so Matt, Sarah's bumming us out now. First we're insignificant, now we're just plain stupid.

[Matt Kirschen]

Well, also I think it is worth pointing out 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. We've all met people who are incredibly smart in specific ways and otherwise idiots. So, okay, so, you know, maybe they have the ability to travel across galaxies, but then not the ability to not shoot themselves within a very short amount of time.

[Neil DeGrasse Tyson]

So maybe they're usually the official answer to the Fermi paradox. Where are they? They think we're idiots.

[Sara Seager]

So either they think we're idiots or we think they are for having self destructed before they could get here.

[Neil DeGrasse Tyson]

Oh, there it is. Touche, touche. All right, so Matt, give me some more.

[Matt Kirschen]

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?

[Neil DeGrasse Tyson]

I love that question. And Matt, who asked it?

[Matt Kirschen]

That was Eric Gross.

[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 somewhere else that you can't actually have a conversation with, even if it's intelligent. Are you getting secrets from? I mean, what if you can't? Or can you? Are we missing something here?

[Sara Seager]

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, and we could have a very slow conversation, very slow. We could imagine.

[Neil DeGrasse Tyson]

No witty repartee there, right?

[Sara Seager]

Send them a message and four years later you'll get their message back and we could exchange ideas about technology. So if we wanted to be practical, like that's probably the most practical avenue.

[Neil DeGrasse Tyson]

So. 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 advance biology on life, I would guess. Is that correct?

[Sara Seager]

Right? No, that's correct. That's correct.

[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 how bright they are in the location, but we will never know what they're made of.

[Sara Seager]

Right. And think about this like we're just here. Now imagine a thousand years from now, you know, 10,000 years from now, we may have a way to get to this. Imagine if there's life on intelligent life on that planet. And we do like a sample return. We fly something by, they send something up, we grab it, we gravitational slingshot around their star and we come back.

[Neil DeGrasse Tyson]

Okay, so, all right, I'll just think a thousand years from now rather than next week.

[Matt Kirschen]

Okay, well, what you just said, that answer segues quite neatly into this question, which I like. And I'm going to combine two different questions from Tom says, who asks what forms of communication are most likely to be able to cross between the stars and trumpet womb. Who says, how do you think we will overcome the language barrier if we ever meet another sentient life form?

[Neil DeGrasse Tyson]

I love it. And Sarah, remember that movie Arrival? 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. Cause 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?

[Sara Seager]

I mean, I love that movie. I love the concept that it may be so difficult that we may not find a way to communicate.

[Neil DeGrasse Tyson]

Okay, so Matt, she just swept that.

[Sara Seager]

One under the rug.

[Neil DeGrasse Tyson]

You hear that?

[Matt Kirschen]

When you hear.

[Sara Seager]

Neil doesn't like any of my answers, but she's sweeping it.

[Neil DeGrasse Tyson]

I don't know how big her rug is in the middle, but how about mathematics? How about symbology? How about.

[Sara Seager]

I mean, I like all those answers.

[Neil DeGrasse Tyson]

You're okay with them or not?

[Sara Seager]

I like it. I like it. It would have to be something that is fundamental in a very mathematical way. I agree with that.

[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.

[Sara Seager]

Right?

[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 it'd be a lot of pantomiming initially, I would guess, before anybody actually communicated. So it is funny that, you know, aliens often just spoke English, you know, in the movies.

[Sara Seager]

Right, right. That's why the Arrival is so great. It's such a great movie because it's the first time they have these beings that have no way to really, really interact with us.

[Neil DeGrasse Tyson]

Right, right, right. So, Matt, give me one more question before we wrap up this middle segment.

[Matt Kirschen]

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?

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[Neil DeGrasse Tyson]

So Matt, we left off with a brilliant pair of questions. Tell me the two names who asked it again.

[Matt Kirschen]

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.

[Neil DeGrasse Tyson]

And must they be based on carbon?

[Sara Seager]

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.

[Neil DeGrasse Tyson]

Because the telescopes aren't good enough yet, right?

[Sara Seager]

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 stars, so we won't see the animals.

[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.

[Sara Seager]

Right? That's the way we're studying exoplanet atmospheres today.

[Neil DeGrasse Tyson]

So we're a long way off from you watching something wave to you in the telescope lens.

[Sara Seager]

We are. But you know, funnily enough, it doesn't stop.

[Neil DeGrasse Tyson]

You got an answer there?

[Sara Seager]

Yeah, I do have an answer. 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.

[Neil DeGrasse Tyson]

Wow. Okay.

[Sara Seager]

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.

[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. And because we basically eat each other. Right. Life eats other life. Unless you're a plant, in which case you eat sunlight.

[Sara Seager]

Right.

[Matt Kirschen]

Wow.

[Neil DeGrasse Tyson]

Okay, 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 a altitude where you get the sunlight and then come back down. And you're not killing anything for your survival.

[Matt Kirschen]

But then you would presumably be prey for whatever is in the lower levels. Cause they aren't accessing that sunlight.

[Neil DeGrasse Tyson]

You'd want to make sure they're photosynthetic too. 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?

[Sara Seager]

No, but it sounds pretty scary.

[Neil DeGrasse Tyson]

Okay, so tell me also about a carbon based life. How important is that?

[Matt Kirschen]

Yeah, because 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?

[Sara Seager]

There really hasn't been a lot of solid work done in that area. It's. It's really hard to construct a biochemistry of a completely different type of life out there. We're not sure if silicon based life is even really possible. We think silicon, 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's still out on that one.

[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. 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.

[Sara Seager]

Yeah, you said it. Well, that's right.

[Neil DeGrasse Tyson]

Okay, Matt, did she sweep any of that under the rug?

[Matt Kirschen]

No, I think that rug is fully lifted and the items underneath are exposed to the elements.

[Neil DeGrasse Tyson]

All right, so Matt, keep going.

[Sara Seager]

All right.

[Matt Kirschen]

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?

[Sara Seager]

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 outside to what we think of as this traditional Goldilocks zone because it has such a powerful greenhouse.

[Neil DeGrasse Tyson]

And they wouldn't call it nasty, they would be thankful for it.

[Sara Seager]

They would need it. Or they'd be able to.

[Neil DeGrasse Tyson]

Yes, they would need it.

[Sara Seager]

Right, 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.

[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 take it's. It can be in places that are not just in the narrow minded swath that's around the sun. So that's good. 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 8 year olds, or the 8 and 12 year olds listening to this in their day, they might look back at our definition, broadened definition of a Goldilocks zone. Say, what do they know? Because for all we know, they could be like life inside of volcanoes or something. I mean, who knows? But.

[Sara Seager]

Right, right. And we haven't observed any rocky exoplanet atmospheres yet. We're just beginning, so.

[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, so this is your sound bite quiz. Really? Can you give us a sound bite? You've been very good in this program up till so far, so I think you'll come out in flying colors. So Matt, let's see how many questions we can squeeze in.

[Matt Kirschen]

We only actually got a few questions left, if that's okay. I think I know the answer to this one, but Andrew Gondreau 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 the probability of life in different areas of the universe finding each other on both axes, time and space approaches zero.

[Neil DeGrasse Tyson]

Ooh, I like that.

[Matt Kirschen]

My guess is no, but I want to hear from the scientists.

[Sara Seager]

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.

[Matt Kirschen]

So why should we 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?

[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 a hundred 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.

[Sara Seager]

I think you got it.

[Neil DeGrasse Tyson]

I think I got it.

[Matt Kirschen]

That is the question.

[Sara Seager]

Yes, yes, yes. It really all depends on how common life is. If life is rare, then yes, that question is an answer is valid. But we all want to believe that. But we see the ingredients for life everywh. 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.

[Neil DeGrasse Tyson]

Yeah, okay. But in terms of how far we've actually searched, my favorite reference, there is an analogy given by Jill Tarter of the SETI Institute. And this is so good. I've given this a hundred times since then. And we got her to say it on StarTalk, so we have it bronzed in our archives. I know what you're gonna say in our archives. 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 saying there are no whales in the ocean. So in terms of how much total volume of space time, frequency is searchable. And so that was depressing but fascinating at the same time for me.

[Sara Seager]

Right, right. But at the same time, now I'm going to turn the tables and do the opposite of trashing all the comments. Like if you're scooping up that one glass of water, surely there is some kind of life in there. 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.

[Neil DeGrasse Tyson]

Excellent, excellent. So that's like taking a scoop of anywhere soil on Earth. There's going to be life in it no matter what.

[Sara Seager]

Right. Or any air, air parcel, even air.

[Neil DeGrasse Tyson]

Very cool, Very cool. Matt, let's slip in a couple more questions. What do you have?

[Matt Kirschen]

All right, John David New 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?

[Sara Seager]

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.

[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's 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. Let's get one more question, Matt, see if we can get it.

[Matt Kirschen]

All right, well, I'm going to combine these two then. I'm really on a combining kick today.

[Neil DeGrasse Tyson]

Okay.

[Matt Kirschen]

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. LAUGHS so music, society, culture and art, how would everything change based on Sarah.

[Sara Seager]

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.

[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 that 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 species to an alien, be they friendly or hostile. And the other question was what it was about.

[Matt Kirschen]

What kind of version of stories and art and music and alien civilization have and how would it differ from ours?

[Neil DeGrasse Tyson]

Sarah, do you guys interact with it? Sarah, do you guys think much about the senses that an alien might have?

[Sara Seager]

No.

[Matt Kirschen]

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 interact with each other?

[Sara Seager]

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.

[Neil DeGrasse Tyson]

Yeah, but you're being like straight scientists there. But now let me ask you, Sarah Seager, the human being who watches science fiction movies, can you imagine if an alien had another sense? What might it be?

[Sara Seager]

Yeah, that's a tough one. I don't have a good answer for that.

[Neil DeGrasse Tyson]

I can take any answer and have to be good.

[Sara Seager]

Well, sometimes I do like to think about our own planet Earth and all the intelligent life here, 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.

[Neil DeGrasse Tyson]

My favorite New Yorker comic we gotta 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. Dolphin with brains bigger than ours. Sarah, it has 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 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, the search for exoplanets, and the search for life itself. So great to have you on and good luck with your work.

[Sara Seager]

Thank you. Thanks for having me.

[Neil DeGrasse Tyson]

All right. And Matt, always good to have you, man.

[Matt Kirschen]

Oh, it's a pleasure. Thanks for having me.

[Neil DeGrasse Tyson]

And we'll look for you on probably Science.

[Matt Kirschen]

Yes, please. I got it straight in one. And also your book as well, Neil. We've got to give that another plug.

[Neil DeGrasse Tyson]

Oh, sorry. 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 start talk 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 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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