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Last week we talked about what it’s going to take to confirm basic biological life across the Solar System and the Milky Way. This week, we’ll discuss what it’s going to take to detect intelligent life out there in space.
Show Notes
MOVIE: Contact (IMDb)
What are Radio Telescopes? (NRAO)
Could We Build a Dyson Sphere? (Popular Mechanics)
Finding Artificial Signals: Lights in the Dark (Berkeley SETI)
Radio Galaxies (Stardate)
What Are Pulsars? (Space.com)
LaserSETI: Scanning the Skies in Visible Light (SETI Institute)
Astrophysical maser (Wikipedia)
What is the Transit Method? (Universe Today)
What’s a neutrino? (All Things Neutrino/FNAL)
NASA Study: To Find an Extraterrestrial Civilization, Pollution Could Be the Solution (NASA)
JWST (NASA)
The Technosignature Challenge (Scientific American)
BOOK: The Sparrow by Mary Doria Russell (Bookshop.org)
How A ‘Super Wolf Blood Moon’ Helped The Search For Alien Life (Forbes)
Coruscant (Star Wars) (Wookieepedia)
Going the distance to confirm a galaxy with almost no dark matter (Yale University)
Transcript
Transcriptions provided by GMR Transcription Services
Fraser: Astronomy Cast, Episode 611, Confirming Intelligent Alien Life. Welcome to Astronomy Cast, your weekly facts-based journey through the cosmos where we help you understand not only what we know but how we know what we know. I’m Frasier Cain, publisher of the Universe Today. With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey Pamela, how are you doing?
Dr. Gay: I am doing well. It is thunder stormy here, but so far the tornadoes have stayed on the other side of the river, which I call a win especially when I look at your weather.
Fraser: Yeah. Yeah. We were talking about this before the show, that we are gonna be experiencing extreme heat here on the west coast of Canada. Normally in June temperatures are 20 to 25. It’s cool. It’s really nice. It’s perfect weather usually. But yeah we’re supposed to hit 34 degrees today and 39 by Monday, which is –
Dr. Gay: Brutal.
Fraser: – what you might experience in Phoenix. It’s crazy.
Dr. Gay: Yeah.
Fraser: Yeah. Yeah. It’s gonna be outrageous. And nobody has air conditioning in this part of the world. So, it’s gonna be an interesting couple of days for sure. Yeah. We’re gonna be huddled up in the one room that we have an air conditioning unit in or huddled down in the basement. We’ll see what happens.
Dr. Gay: And since this may be the new normal I recommend getting window units.
Fraser: Yeah. Yeah. When we build our new place we’re actually gonna get a passive heating/cooling system heat pump. So –
Dr. Gay: Yep.
Fraser: – yeah. Yeah. There’s new technology. Our house is sold right now but our new place will have newer technology. All right. So, last week we talked about what it’s gonna take to confirm basic biological life across the solar system and the Milky Way. This week we’ll discuss what it’s gonna take to detect intelligent life out there in space. So, it’s funny, I had this conversation with Dr. Jason Wright, who’s one of my favorite exoplanetary researchers. And we were sort of talking about this shift from the NASA and the rest of the scientific community that’s starting to be interested in adopting and funding research that’s searching for intelligent life. And he was like, “We’re okay for searching for dumb life, but why aren’t we okay for searching for smart life?” But there is a bit of a sea change that’s starting to happen. So, tell me about the search for intelligent life so far.
Dr. Gay: Well, so far it has primarily taken very limited number of forms. There is, of course, the very well-advertised by the movie “Contact” method of using radio telescopes to look for systematically altering radio signals that are altering in a way that indicates there’s an intelligence behind that that is trying to send us information. Beyond looking for these radio signals that have, well, an actually signal in them we have done things like look for the infrared excess of Dyson spheres and other megastructures that are out there –
Fraser: Wow.
Dr. Gay: – in catalog data. So, this is a matter of you can take data that already exists, look through it, and see, “Hey, is there anything out there consistent with megastructures?” So far I haven’t found anything that way either.
Fraser: So, let’s start with this idea of searching for radio signals. Why are radio signals the best thing to search for? Because that’s where we started.
Dr. Gay: Well, it’s multi-part. First of all the radio signals most of the time aren’t going to get drowned out from the star’s light the same way an optical signal would be. Folks have talked about using lasers to try and signal aliens out there who might be able to see us transiting in our sun and trying to basically be a beacon of light literally across the cosmos saying, “Here be life.”
Others have said, “Please don’t do that. We don’t want to be killed.” But there is a chance that there are braver souls out there in whatever shape they may take that have also realized that light with radio wavelengths can be used to send information that won’t get drowned out by the stars and are trying to communicate this way.
Fraser: And also, a radio signal is unambiguous.
Dr. Gay: Yes.
Fraser: There are frequencies that you can put into a radio signal that cannot be produced by nature.
Dr. Gay: Yes. And that’s the importance of looking at how it’s modulated. We’re used to carrier signals, side signals, all these different things that are taken advantage of by television broadcasts, by radio stations, to do things – especially now with digital television – as complex as putting different languages on slightly different versions of the same signal. And by being able to modulate signals in ways that clearly show mathematical intent, nature doesn’t generally do that. And so, we’re out there looking for those prime numbers in whatever base they might be in.
Fraser: Mm-hmm. So, there’s two parts to it. There’s that there can be radio signals in parts of the spectrum that there is no natural way to produce it.
Dr. Gay: Yes.
Fraser: But then there also can be a signal in the radio wave that is clearly provided by some intelligent civilization. As you say, prime numbers. What have you.
Dr. Gay: And this is where it also starts to get down to the if there is something that is produced in a wavelength where we don’t think there should be signals there’s gonna be a whole lot of people going, “No. Nature just figured out how to do something we don’t understand.”
Fraser: Right. Yeah.
Dr. Gay: So, you really need those prime numbers to get folks to believe it.
Fraser: Yeah. Yeah. But I’ve definitely heard that there are some signals.
Dr. Gay: Yeah.
Fraser: If we see some – even a combination of signals –
Dr. Gay: Yes.
Fraser: – all at the same time, then you know for certain there’s nothing out there that can produce this that isn’t a radio transmitter. So, that sounds like the perfect system. What’s the downside of radio waves?
Dr. Gay: Well, to create something capable of traveling through space and still having enough signal by the time it gets to us, requires purpose. Yes, the Earth has been leaking television and radio signals for more than a century. But while those signals are out there, they’re gonna get lost in the background of radio galaxies, of pulsars, of everything else. And they’re also fighting against each other where – all those FM stations – they’re all gonna get muddled together. And if my car can’t easily detect something in St. Louis which is half hour’s drive away –
Fraser: Right. Yeah.
Dr. Gay: – I need to worry.
Fraser: Right. And so, when you say “intentional” –essentially – the alien civilizations will need to see Earth and go, “Here’s a message for you Earth.”
Dr. Gay: Yes.
Fraser: Point their giant radio transmitter specifically at the Earth –
Dr. Gay: Yes.
Fraser: – and release the light. And if someone over on Alpha Centauri nearby, they’re not gonna see the signal. So, you’ve gotta get this alien civilization that has chosen us specifically to receive this message.
Dr. Gay: And this actually isn’t that ludicrous an idea. There are some 2,000 worlds – or rather 2,000 stars – that we believe have worlds that from where they’re positioned over the coming years and centuries they’ll be able to see the Earth passing in front of the sun’s disc of light. And if we know where they are, and we wait until we’re transiting the sun, so they know where we are and we shoot a signal their way, hopefully, they’ll be listening. And we are preferentially looking for signals from transiting planets that we hope know, “Hey, maybe people out in these directions know that we’re here.”
Fraser: And, of course, a lot of people are totally freaked out about –
Dr. Gay: Yes.
Fraser: – the possibility of us transmitting to some other alien civilization.
Dr. Gay: Yes.
Fraser: And, hopefully, by the end of this conversation you will realize that that horse is already out to the stable.
Dr. Gay: Yes.
Fraser: So, the aliens know we’re here. Okay. So, that’s one kind of signal. Aliens point their big radio transmitter at Earth and let us know they’re here. Now you mentioned, briefly, laser light.
Dr. Gay: Yes.
Fraser: What are some other ways that aliens could target us directly? Because when we get into them leaking their existence unintentionally – but first I’d like to – they’re trying to reach out to us and let us know that we’re not alone in the universe. What a kind thing for them to do. How it’s gonna do it.
Dr. Gay: So, there’s things like you can develop masers that you then purposefully modulate. We see masers in a variety – this is a microwave laser – we see masers in a variety of planetary atmospheres and clouds of dust and gas. Well, take one and figure out how to modulate it, which is something beyond what we can easily do at the level that it’s going to shine bright enough to see across the galaxy right now. But this is the kind of thing we can do in the small scale. And it’s just a matter of technology and energy to do it on the big scale.
So, let’s look at this naturally occurring microwave lasers and see if they any of them are, well, dropping a beat. And that could be a definitive signal. Then purposefully trying to get our attention. Lasers are another way. Now the question is how do you put together a signal that clearly isn’t a star? Well, you can do that with a laser because it’s a single color of light. But then also make it bright enough that it can be seen at that distance. Again, you’re looking at massive energy consumption being required. So, anyone that we’re gonna be able to see that is purposefully trying to signal us, is gonna be more advanced than us. And that’s a bit –
Fraser: Right.
Dr. Gay: – intimidating.
Fraser: Back to this idea of the transit method. One idea that I think I really like as well that would require more start-up energy but –
Dr. Gay: Yeah.
Fraser: – then would be easier is to launch, say, triangular-shaped satellites around the star.
Dr. Gay: Yes.
Fraser: Because these would give off a very bizarre signal as they transit in front of the star from our perspective. It would be completely unnatural to see these.
Dr. Gay: And the reason that this works is if you have some odd-shaped structure – and I’m trying to find something round. Yep. Okay. If you have an odd-shaped structure as it passes in front of something else the amount of light that it blocks is going to change in a very different way than if you have a round structure passing in front of the star.
And so, we can actually tell the shape of whatever it is that’s blocking out starlight by the way the light that we receive changes. And a triangle is kind of the most simplistic structure that you can get. And a good old equilateral – especially one that you maybe varied the orientation with every orbit – would be a great way to say, “Hey, we’re here. Look at us doing weird stuff with our star.”
Fraser: Right.
Dr. Gay: And it could be fun.
Fraser: Yeah. And so, they could launch, say, some giant triangular-shaped solar sail and have it pass in front of the star. It’s one big launch.
Dr. Gay: Yeah.
Fraser: It’s tough to do that. But once that’s done then they don’t have to continue sending messages. It just keeps passing in front of its star every few years and showing the universe that they’re there. What about technologies that we just are starting to understand but might prove very effective like neutrinos or maybe gravitational waves.
Dr. Gay: And this is something where we don’t actually know if it’s possible to communicate this way. Now if you happen to have a pair of entangled particles that are generated you can – we believe – separate them by lightyears and still see the flip of state in one in the other. But you need to start out with one of the particles and then send the other way off. So, you can’t use entangled particles to talk with aliens unless it’s prearranged.
Fraser: Right. Yeah. Yeah. There’s no benefits to –
Dr. Gay: No.
Fraser: – using entanglement to communicate. But – the neutrinos – we have a worldwide network of neutrino detectors poised to catch the next nearby supernova.
Dr. Gay: Yes. And here we can imagine we know how to create neutrinos, just not in massive amounts. We can create them – heck, every nuclear reactor on the planet Earth is creating neutrinos. If we cold figure out how to much more massively generate neutrinos – without destroying our planet, that’s a key – and send them in a unified direction and be able to turn them on and off – that signal –so it’s not mistaken for a supernova it may be possible to confuse people who are also doing neutrino science enough –
Fraser: Right.
Dr. Gay: – to figure out, “Well, that doesn’t look natural.” Now neutrinos – because they are so hard to detect – it’s gonna be hard to create enough signal that we can unambiguously say, “That’s intelligence.”
Fraser: Right.
Dr. Gay: But then gravitational waves is something else where it would take such massive energy to create something that unambiguously says, “That is intelligence.” You have to wonder just how it advanced is that civilization. Are they building their own method to move stellar mass blackholes around –
Fraser: Right.
Dr. Gay: – and fling them together just to communicate?
Fraser: Yeah. Exactly. They collide two blackholes together to say, “Hi.”
Dr. Gay: Right. Exactly. And what –
Fraser: Yeah. Yeah.
Dr. Gay: – that feels like an awful waste of energy. But we have to be aware that the way we think, the way we imagine, the way we perceive time, may not be the same as whatever else is out there. So, we have to be prepared for weirdo signals in our neutrinos. For strange signals in our blackholes. Imagine that if instead of getting the characteristic blackhole chirp we got a musical melody.
Fraser: Mm-hmm. Mm-hmm.
Dr. Gay: That would completely confuse the bejesus out of everyone doing blackhole science.
Fraser: Yeah. That would be crazy. All right. So, let’s talk about ways that we could sneakily detect aliens – intelligent civilizations – out there in the universe.
Dr. Gay: Pollution. This is one of my favorites. I actually have – I don’t know if you remember. I made a bet with Seth Shostak a number of years ago that while we were alive life or at least a civilization by its carnage would be discovered through its atmospheric pollution. So, there is combinations of molecules in our environment that just aren’t naturally occurring. You don’t get combustion engines, you don’t get the nuclear tide distributions, in terms of all the stuff that was created during atomic blasts. You don’t get just free oxygen with all this other stuff going on –
Fraser: Right.
Dr. Gay: – unless there is life to produce the oxygen and intelligence to pollute it.
Fraser: Right. The chlorofluorocarbons as the aliens wreck their ozone layer.
Dr. Gay: Exactly. Exactly.
Fraser: So, yeah. So – okay. So, we could detect the pollution. And it’s probably beyond the capability of any telescope currently. But things like James Webb and the next generation telescopes after that should just barely be able to –
Dr. Gay: Yeah.
Fraser: – sense that kind of thing.
Dr. Gay: And so, there’s the potential that we are one refuses to launch telescope that should’ve gone up in 2007, thank you very much. One very belated telescope away from finding civilizations.
Fraser: Right.
Dr. Gay: And then science-fiction writers have pointed out some really amazing things. Imagine if we decide with our tidally locked moon that we want to put communication stations up on the moon that are strong enough to send a signal so that everyone who can see the moon can hear that radio station, watch that television news. Now that’s the high energy thing to do. It’s kind of not effective. Probably never gonna happen. But you can kind of imagine a public art project going this way. Well, as that moon orbits its world we would see that radio signal turning on and off with its orbit. And so –
Fraser: Right.
Dr. Gay: – here is the way to get a massive radio signal that behaves in strange ways and says, “There’s life doing something weird right over there.”
Fraser: Mm-hmm. And that’s different than sending a specific beam signal –
Dr. Gay: Yes.
Fraser: – towards the Earth. This would be more like the leaked electromagnetic radiation –the leaked radio waves – coming from the planet and its moon. And that’s way trickier to detect but not impossible.
Dr. Gay: And also makes excellent science fiction. The Sparrow by Mary Norris Russell has this as part of its premise.
Fraser: Oh. Well, a telescope that’s in the works right now –
Dr. Gay: Yeah.
Fraser: – the Square Kilometre Array – in theory – can detect the – and I forget. I’m trying to remember the exact numbers. But something like air traffic control systems of planet Earth to a distance of about 100 lightyears. And that’s leaked radio transmission. So, not directly beamed out. But literally you will hear – with the Square Kilometre Array – alien airplanes landing 100 lightyears away.
Dr. Gay: That’s just –
Fraser: It’s just crazy.
Dr. Gay: – disturbing.
Fraser: Right. Right. So, imagine a Super Square Kilometre. It’ll send a 10 square kilometer area. 100 Square Kilometre Array. A space base Square Kilometre –
Dr. Gay: Yeah.
Fraser: – Array. In theory we should be able to get to this.
Dr. Gay: Turn that giant triangle into a radio telescope.
Fraser: Yeah. Yeah. So, then imagine what are some other things that we do as a civilization that could theoretically be detected by other civilizations and vice versa.
Dr. Gay: Well, we light things up. Our light pollution actually is something that could be seen. There’s been some really cool studies done during lunar eclipses where they’ve looked at variations in the Earth’s shine coming off the moon and they’ve been able to see that there’s light coming off the Earth that is affecting what we see on the moon. So –
Fraser: Or light pollution.
Dr. Gay: – light pollution. Our light pollution –
Fraser: Ooh.
Dr. Gay: – can be seen from space.
Fraser: That’s amazing.
Dr. Gay: So, there’s light pollution as an option. And then just building stuff in places that weren’t that way to begin with. So, take an asteroid in the cold darkness of space hanging out doing its cold dark space kind of thing and start putting civilizations on it. All of the expanse. Well, that’s gonna heat that asteroid up to a temperature it wasn’t meant to be. It’s going to add lights in specific wavelengths that don’t really make sense for a blackbody. And that combination of excess heat and LED lights, florescent lights, whatever kind of light that you’re using that says there’s something not natural there.
Fraser: I can imagine this future advanced civilization which has colonized their entire solar system.
Dr. Gay: Yeah.
Fraser: They’ve got cities on their other terrestrial planets. They’ve got bases and stuff on all of the different asteroids. You’ve now got a totally different electromagnetic signature. A different light curve –
Dr. Gay: Yeah.
Fraser: – coming from this star and its planets that you would if it was just a regular star and empty dead planets.
Dr. Gay: And to use a won’t ever hopefully actually exist example, imagine the Star Wars planet Coruscant with all of its lights, all of its buildings, and now make all of them compressed sodium bulbs. Suddenly you have this weird atomic spectral feature due to using the same kind of lightbulb everywhere. And we can imagine a similar everyone uses blue LEDs, everyone by using a consistent form of lighting, because it’s cheap and efficient, you specifically screw up light coming from your solar system in a really cool way.
Fraser: And you mentioned this earlier on in the episode, but if you take this to its logical extreme and you actually enclose the star in some Dyson swarm –
Dr. Gay: Yeah.
Fraser: – what kind of a signature does that give off?
Dr. Gay: It creates an infrared peak. And so, you have to be careful because there could be a debris disc and it’s not easy to separate a Dyson’s swarm from a debris disc. But different composition things radiate heat in different ways. We can actually – to a certain degree – tell what is the composition of an asteroid by how it reradiates light. And if we look close and we see that there’s an infrared excess that is consistent with it being a big old metal object out there it could be a big old metal object out there. Now add some LED lights and it’s a done deal.
Fraser: Right. Yeah. So, the LED sphere is surrounded by LED lights blinking out there and you’ve got a pretty interesting signature. And you can take this idea to the logical extreme. This idea of some alien civilization that has enclosed all of the stars in their entire galaxy –
Dr. Gay: Yes.
Fraser: – in Dyson spheres. Now you’ve got a galaxy that looks weird.
Dr. Gay: Yeah. And that starts to become how to initially differentiate that from a just dark matter galaxy. And so, you have to really just sit there with a telescope and expose and expose and expose. And it’s kind of crazy to think we have found at least one galaxy that – no matter how we look – appears to have no dark matter. And if we find a galaxy out there that appears to have no luminous matter now we need to figure out if aliens just hid it. Just hid it.
Fraser: Right. Just hid the entire galaxy.
Dr. Gay: It’s a thing.
Fraser: Yeah. So, which of all of these methods do you think is gonna be the one that pays off first?
Dr. Gay: I honestly think that the first thing that we’re gonna find is going to be a polluted atmosphere because I suspect pretty much every form of life that occupies land on its way to civilizing is going through a “And now we burn stuff” phase.
Fraser: Right. Yeah.
Dr. Gay: And that’s –
Fraser: “Now we drive places” phase.
Dr. Gay: Yeah. Yeah.
Fraser: Yeah.
Dr. Gay: Well, even if they don’t drive places they’re probably gonna burn stuff.
Fraser: Yeah.
Dr. Gay: And that will show up. And then I keep thinking that a ringworld out there with its IR excess superimposed on a star. That wouldn’t be that hard to find. And while we haven’t found one yet I keep hoping. I keep hoping.
Fraser: It is kind of amazing when you think of how quickly our telescopes are getting bigger and bigger. With the Event Horizon Telescope we have a telescope the size of planet Earth.
Dr. Gay: Yeah.
Fraser: There are plans in the works to maybe make that the size of the solar system.
Dr. Gay: Yeah.
Fraser: There are future space telescopes in the works like Luvlar and HabEx and stuff that are gonna be dramatically bigger and more powerful than even James Webb. And so, continue that technology on for hundreds of years and it just seems impossible that we won’t have the capability to detect intelligent life in a pretty vast chunk of the Milky Way. And so, then if we still haven’t seen any life and we have the ability to scan a quarter of the Milky Way’s volume what do you think that means?
Dr. Gay: So, it could either mean that the universe is mostly empty, or it’s mostly filled with people who take a look at how they live in a way that is closer to the thinking of the indigenous people here of North America. Where instead of seeing themselves as having a right to the land, a right to the world, a right to the solar system to use and colonize as they will, that if they instead see it as they have an obligation to the land, they have an obligation to the animals to be there as stewards and to protect. If that different ideal of being a steward of the landscape is the dominant one in the universe it’s gonna be a whole lot harder to find alien civilizations.
Fraser: Mm-hmm.
Dr. Gay: And that is something for the philosophers and the writers –
Fraser: Right.
Dr. Gay: – to contemplate.
Fraser: Or they’re all just jacked into the matrix, and they don’t bother –
Dr. Gay: There’s that too. There’s that too.
Fraser: – going out into the world anymore. But, yeah, super interesting. All right. Thank you Pamela.
Dr. Gay: Thank you.
Fraser: All right. Did you have some names for us this week?
Dr. Gay: So, we are – as always – brought to you by you. And as a reminder when we go on summer hiatus it’s so that we can improve what we do, take some time off. And when we come back in the fall it is my hope that we’re gonna be able to bring you live media videos, images, while we talk here on Astronomy Cast. We can only make this happen thanks to your year-round support over on patreon.com/astronomycast.
This week I would like to thank Wayne Johnson, Iggy Hammick, Geoff MacDonald, Ruben McCarthy, Philip Grand, The Mysterious Mark, Randa, Jim McGihon, Chris Wheelwright, Bob the Cat, Kathleen Mattson, Mark Phillips, Leigh Harbone, Father Prax, Scott Bieber, Gfour184, Ronald McCoy, John, Aron Tannenbaum, J. AlexAnderson, Brian Kilby, Tim Gerrish, Michelle Cullen, Roland Warmerdam, Brent Kreinop, Marco Iarossi, Jeremy Kerwin, Mark Steven Rasnake, Omar Del Rivero, Dustin A Ruoff, Claudia Mastroianni, Eran Segev, Saebre Lark, Frode Tennebo, Paul L Hayden, Arthur Latz-Hall, Joe Wilkinson, Matthew Horstman, Justin Proctor, Cemanski, and Alex Raine. Thank you all so much for being here supporting us and allowing us to do what we do.
Fraser: Thanks everyone. And we’ll see you next week.
Dr. Gay: Bye-bye.
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