So far we’ve talked about life in terms of its chemistry and telltale signs of biology. But what if there’s intelligent life out there in the universe that has created technologies just as good, or even more advanced, than our own? Some scientists are thinking about how we would detect the signals that would come from distant civilizations, if they are out there. Those signals are called “technosignatures.” Jason Wright, professor of astronomy and astrophysics at Penn State, has been thinking about the different technosignatures we could pick up using the telescopes we already have, and the telescopes that we could develop in the future.

Jim Green:If you lived on a planet around a distant star and you pointed a powerful telescope back to Earth, you might easily be able to pick up the signals from all of the technologies that we have developed. Could we find this type signals from another civilization on a distant planet somewhere in the galaxy?

Jason Wright:We’re already doing a lot of search for extra-terrestrial intelligence by building and developing and using all of these instruments. We just have to think of it that way.

Jim Green:Hi, I’m Jim Green, chief scientist at NASA, and this “Gravity Assist.” On this season of “Gravity Assist” we’re looking for life beyond Earth.

Jim Green: I’m here with Dr. Jason Wright and he is a professor of astronomy and astrophysics at Penn State and a member of its Center for Exoplanets and Habitable Worlds. Welcome Jason, to “Gravity Assist.”

Jason Wright: Thank you very much, Jim. I’m really glad to be here.

Jim Green:Yeah. First, Jason, I want to congratulate you on being the recipient of the 2019 Drake Award. That’s quite a distinction.

Jason Wright: Thank you very much. Yeah, I was really honored to get it. It’s just amazing to get an award named after a pioneer like Frank Drake.

Jim Green: Well, you’re well known for discussing the important science that is really at the root of the Drake equation, so give us a little background on what that is.

Jason Wright: Sure. The Drake equation was an equation that Frank Drake wrote down to try and estimate the number of communicating civilizations in the galaxy that we might be able to detect with radio telescopes. And so he wanted to quantify and formalize the general sense we have that there are so many hundreds of billions of stars in the galaxy, surely at least one of them has some kind of technological species that might be communicating with us. So we started with the number of stars in the galaxy, and then attempted to estimate what fraction of those have planets, what fraction of those planets might host life, what fraction of those planets with life might have complex life that could build tools, and then what fraction of that life is communicating with us right now. And so it allows us to kind of break down the whole problem of finding other life in the galaxy into individual pieces that we can study and attempt to estimate numbers for.

Jason Wright: We now know that something like one in 10 or one in four of those hundreds of billions of stars in the galaxy really do have planets, rocky planets that could have liquid water on the surface of them. Now we haven’t discovered any planets with liquid water on them other than the Earth, but we’ve found many that may have liquid water. And so just that by itself means that there are hundreds of billions of potential sites for life in the galaxy and he didn’t know that.

Jason Wright:He didn’t know if most or even any other stars had planets around them when he first wrote down the equation. So that has helped a lot. But the other terms in the equation are still pretty fuzzy. We only have one example of life arising on any planet, our own, but if we were to find, say, microbes on Mars or signs of metabolism in the plumes coming out of Enceladus, that would suggest that wherever you have water, you’ll have life arise and that would greatly increase the chances that there’s someone out there trying to get ahold of us.

Jim Green:Well, the Drake Award is given to scientists by the Search for Extra-Terrestrial Intelligence Institute. This is the SETI Institute. So please tell us how SETI is looking for extra-terrestrial intelligence.

Jason Wright:Right, so the term SETI, S-E-T-I, is the Search for Extra-Terrestrial Intelligence and it actually began at NASA as a radio program to try and detect the sorts of signals that Frank Drake pioneered. But at some point, Congress directed NASA to stop doing that. And so the SETI Institute in California was founded as a way for philanthropic funds to support the search when NASA wouldn’t do or couldn’t do it because Congress told them. And so the SETI Institute now, for decades, has been the hub for the search for radio signals from other stars and through the philanthropic contributions of people like Barney Oliver and Paul Allen, they’ve managed to really advance the field and carry it forward and today radio SETI is really mature and scanning the skies all the time for signs of alien life.

Jim Green:So these are potential radio transmissions that SETI might observe coming from sources elsewhere in the galaxy. We call those signatures of technology, or technosignature. What else is a technosignature?

Jason Wright: Jill Tarter, who’s one of the founders of this field and for a long time led the SETI Institute, wanted to sort of reframe the whole search for technology in the galaxy and point out that it’s not just looking for really powerful ham radio signals from another star. It’s really the search for any kind of technology that we might be able to detect. And so she looked at how NASA had developed the idea of biosignatures, the ways that we could tell that life was somewhere else, such as microbes on Mars or certain chemicals in the atmosphere of an exoplanet and said, “Well, what we’re doing is looking for techno signatures and they might not be radio waves. They could be laser pulses. We might detect the extra heat on a planet coming from all of its power plants and cities. We might detect very large structures and orbit around other stars as they pass between the stars and the Earth. There are lots of things we can imagine doing to try and find signals or signs of technology other than just narrow band radio transmit.”

Jim Green:Well, these narrow band radio transmissions are some of the things that we do here on this planet. So could another civilization pickup our technosignatures, or our radio signatures?

Jason Wright: I think so. So if we were looking at the sun from afar, say that Earth were actually around Alpha Centauri, looking back at the Sun, would we be able to tell that the sun had the Earth on it and that Earth had liquid water and that Earth had life and that Earth had humans? And even just knowing that the sun had a planet like Earth around it would be very challenging with the technology we have today. At that distance it’s very hard to detect, but it’s possible. Knowing that it had an atmosphere, knowing it had liquid water, that is really at the moment beyond our capabilities, but NASA is working on new space telescopes that could figure something like that out. But to know that Earth had life is extremely challenging. It just doesn’t put a big imprint on the Earth that’s detectable from another star.

Jason Wright:However, if they knew what frequencies to check and when to check and what they were looking for, they would be able to detect, for instance, our interplanetary radar, that we use to find the distance to Venus and study the rotations of asteroids. They might even be able to detect our ICBM radars that are constantly scanning to make sure that missiles aren’t flying around the world. They might be able to detect, perhaps eventually, our interplanetary probes that have escaped the solar system and are now flying and interstellar space. And so it’s very possible that our technosignatures are the most obvious signs that there is any life in the solar system. So it stands to reason if we’re looking at other stars, those technosignatures might be more obvious than the biosignatures. So if we want to find life in the universe, it might be most fruitful to look for technosignatures instead of biosignatures because after all, that’s probably true for us.

Jim Green:What are some of the kinds of tools that we either have today, or we need to develop to really go after technosignatures?

Jason Wright:It’s interesting because astronomers like to build these general kinds of telescopes that are looking for all kinds of things out there. And so when we think about how are we going to go to technology, the dream instruments that we would build to do that are the same ones that we’re already building to do all sorts of other kinds of astronomy and astrophysics and planetary science. So the sorts of things we would build our larger rays of radio telescopes, and sure enough, those already exist. And in fact, a lot of the work done at the SETI Institute and at the UC Berkeley SETI Research Center and other places that do SETI, piggyback on those telescopes and while they’re being used for other science, they also look for radio signals.

Jason Wright:Similarly, there’s all sorts of NASA assets. We’ve got the WISE satellite that surveyed the entire sky and infrared wavelengths. We have coming up the James Webb Space Telescope that’s going to be able to take just absolutely amazing data from all sorts of stars in the universe. These are the sorts of things that we would hope would be built to go looking for technosignatures. So I would say we’re already doing a lot of search for extra-terrestrial intelligence by building and developing and using all of these instruments. We just have to think of it that way and task those telescopes to do SETI work in addition to the other work that they are doing.

Jim Green:And when you think about a planet, perhaps an Earth-like planet orbiting it’s sun, we could see it perhaps away from the sun’s intense light during the time when the sun’s light is shining on it in the day, but also as the planet goes around the sun at its nighttime. And if there’s life on those kinds of planets, what kind of things do you think we can see in the atmospheres of those exoplanets?

Jason Wright:Yeah, that’s exactly right. These planets are very small and so there’s two ways that you can go after trying to find biosignatures or technosignatures on them. One of them, as you say, is that with these very large fancy telescopes, many of which NASA is putting into space, we can separate the light from the planet and actually take an image of the planet as maybe a pale blue dot and then study it spectrally. And then the other way is when it passes in front of the star, the star light will filter through the atmosphere and the chemicals in the atmosphere will block certain colors of light and certain patterns of chemicals in the atmosphere would be indicative of life.

Jason Wright:So for instance, if the Earth passed between the sun and another star, and you were trying to study the Earth’s atmosphere, that way you would notice that the Earth’s atmosphere contains both methane and oxygen at the same time and that’s very unusual because lightning should make the oxygen and methane combined into carbon dioxide and water and make at least one of them disappear. The reason we have all that methane is because of things like cows and metabolism of mammals just creates lots of methane and so that’s a sign of life. Also, however, if you made very sensitive measurements, you might detect that the atmosphere contains chlorofluorocarbons or CFCs. Now we don’t put much of those in the atmosphere anymore because we now understand how bad it is for the ozone layer, but that’s absolutely artificial. Nature does not make CFC and so that’s how you could tell the technosignature in our atmosphere.

Jim Green:Yeah, so in other words, the technology of that planet is actually generating those trace gases, which are affecting the atmosphere and if we can tease that out of the spectrum, we got it, then we’ll know that there’s advanced life on those planets.

Jason Wright:And it’s even better than that because scientists can dream up scenarios without any life where you might get methane and oxygen at the same time. It shouldn’t be common, but it could happen. There’s really no way that nature produces CFCs. That means you have to have technology. And so if you see that, you know you’ve got life. So in a lot of ways, searching for technosignatures is a stronger way to go because when you find it, you’ve really found it.

Jim Green:Now you were involved in a survey going back a few years called Glimpsing Heat from Alien Technologies. What was that about and what did you learn?

Jason Wright:So there are actually a lot of ways, as we said, to go looking for technosignatures and most of them actually all go back to about 1960 to 1964. There’s looking for radio waves, there’s looking for laser light, there’s looking for probes that might be in the solar system right now, but one of them hypothesized by Freeman Dyson, who sadly died just a couple of months ago,

Jim Green:Yes, indeed.

Jason Wright:…was that we could look for large technologies that orbit around the star. So Freeman Dyson’s idea was that we don’t know what alien technology is going to be like, but we can be pretty sure it will use energy. That’s almost the definition of technology. And so where is it going to get all of that energy and how much could it possibly use? If you give humans a billion years to develop technology, how much energy will we need to power it?

Jason Wright:And his answer was that the most energy that they could possibly use was all the energy coming from their star. And so if they are going to capture all, or even just 1% of the energy coming from the star, well, it would use that energy and then it would have to give it up as heat. So for instance, my computer right now is warm and the reason it’s warm is it’s getting energy from electricity, it’s going to use that energy to help me do this interview and then when it’s done with the energy, it doesn’t disappear. The energy has to come off as heat. So if there’s technology around a star using even just 1% of the star light, then not 1% of star light should be coming off as heat and we can detect that heat at infrared wavelengths. So the idea behind GHAT, Glimpsing Heat from Alien Technologies, was that NASA had just finished an all-sky survey to look at how much heat was coming off of every star and galaxy in the universe.

Jason Wright:And so I thought, well, that’s great. That’s exactly what Freeman Dyson had hoped someone would do, but no one could really do very well before that satellite flew. So it wasn’t at the time something NASA would have been interested in looking at with its telescope, but we did get some funds from the Templeton Foundation and so we were able to hire a researcher to go through the WISE database and try and put limits on what’s the most heat coming off of every star and every galaxy, maybe galaxies are filled with technology. And so we put some of the first strong upper limits on how much heat is coming out of all of the technology of other galaxies, which was just a pilot study. We weren’t able to put any really firm upper limits on it, but we could say things for instance, like, “There aren’t any galaxies where every single star has a hundred percent of its light being used up by technology,” which we actually didn’t know before. It’s not a surprise, but it’s a first step and I’m hoping we can do a lot better in the future.

Jim Green:Well, let me ask you this, let’s say you discovered evidence for a technosignature and even better, that it was confirmed. You have to put yourself in that future thinking, what would you do next?

Jason Wright:Yeah. So the confirm part is really important. I’m glad you brought that up. If you’re looking with a radio telescope and you see that signal, you’re basically done, unless that signal came from Earth, and you do have to rule that out, but you can roll that out pretty quickly. Unless it came from Earth, that signal has to be a technology from another planet when you find it. So then you’re done. But if you go looking for things like the heat of technology, or you go looking for large technosignatures or mega structures passing in front of stars, or what you think is chlorofluorocarbons in the atmosphere of another planet, you’re not going to be absolutely sure what you have. What you’re going to have is some sort of anomaly. And so you’re going to have to follow that anomaly up and it’s going to take a long time.

Jason Wright:And so I think it’ll be a lot like, “Well, we have an interesting candidate. Wow, that candidate is stronger than we thought, Oh, that thing we thought it might’ve been isn’t and it really could be aliens.” And it’ll just be a slow process where more and more astronomers are convinced, yes, that really is aliens. Now, if it’s confirmed, if we get that radio signal or that laser signal from that source, and there it is, we know what it is, then the S in SETI just changes because it’s the Search for Extra-Terrestrial Intelligence, well it will become the Study of Extra-Terrestrial Intelligence. And at that point, it’s going to depend on what it is that we have found and we’ll have to figure out how to study it.

Jim Green:Yeah, you’re right. Probably every telescope in the world will be looking at it.

Jason Wright:It’ll be a big deal.

Jim Green:It’ll be a big deal. And then, okay, let’s say you want to be able to communicate with it, I would think. So in other words, if a technosignature came from a star, a thousand light-years away, that means it’s already been a thousand years since that was emitted for us to see it. How would we know that that civilization is still around?

Jason Wright:Oh, well, yeah, the ping time, that’s going to be a problem. So if it’s a thousand light years away, which is a very reasonable distance, then if we have a message that looks like it’s inviting a response and if we should choose to respond, and I don’t even want to go there, then we’ll send that back and it’ll take a thousand years before they get it. And so that’s 2,000 years from their perspective of sending it out and it coming back and 2,000 years ago, well, we had very different technology levels and very different social structures and completely different governments and societies. And so you can imagine that, yeah, it’ll be a very different place when our message finally gets back, if they’re even there at all.

Jim Green:Well, you’ve been working on this topic now for many, many years. What really inspires you to keep going on it?

Jason Wright:I really like puzzles that no one else seems to be working on and this is not a field with a lot of people working in it. I also really liked that it’s a big question that captures everybody’s attention. A lot of times we find our vocations working on important problems, but then when our Aunt Millie at Christmas asks what we work on, we have to figure out how to explain it and why it’s relevant and her eyes glaze over and it can be hard. But when I say I’m looking for signs of technological life in the galaxy to see if we’re alone, nobody’s eyes glaze over. They get wider. Everyone understands how neat that is. So it’s a great problem to work on where there’s a lot of headway to be made and everybody gets why it’s so important. It’s a lot of fun.

Jim Green:Good, that’s interesting. Well, Jason, I always like to ask my guests to tell me what was the event in their life, whether it’s a person place or thing, something that got them so excited about becoming the scientist they are today. I call that event a Gravity Assist. So Jason, what was your Gravity Assist?

Jason Wright:Oh man. It’s funny, I’ve wanted to be an astronomer for as long as I can remember so my Gravity Assist might’ve come out of is pretty young. One thing that’s always struck me about my career arc is that when I was six, I wanted to be an astronomer, but I had no idea what that meant. I didn’t know if I was any good at it, I didn’t know what being an astronomer was day to day and so at every stage of my career, when I got to Boston University and first got to do some research and take my physics classes and then at UC Berkeley, where I started doing much more research and much more difficult classes and then when I started as a professor here, I started advising students, I started teaching courses, at every step along the way, I discovered that I really enjoyed what I was doing and that I was really good at it.

Jason Wright:And so I’ve been incredibly lucky. And so maybe it’s more like Voyager leaving the solar system. There wasn’t just one gravity assist. Every time it went by one of the giant planets, it went a little bit faster and it headed on to its next destination and every gravity assist was just right. And if any one of those have been unlucky and missed, not that NASA would have missed, but it was a difficult calculation, it wouldn’t have made it, but it did. And so I think my career trajectory maybe is more like Voyager’s.

Jim Green:Well, I understand completely and you’ve got to have those little nudges along the way to keep you going sometimes. And, you know, we’ve gotten to the point where we find so many things out there that I would call circumstantial evidence that there’s life beyond Earth, but there’s so many of them. It’s almost inconceivable to me to think that there’s no life beyond Earth and I think you’re in that same, same bucket that I am in that respect.

Jim Green:Early on, Frank Drake worked with Carl Sagan. They went to the Arecibo telescope and they fired off a message and that means they were trying to send a technosignature. Should we go back to that process?

Jason Wright:It’s a neat question. The Arecibo Message, as it’s called, was a fantastic project. It has inspired so many people to think about this problem, just like the Drake equation did. I mean an introductory astronomy textbook is almost guaranteed to have the Arecibo message in it for students to try and decipher and understand. But in that way, I think the Arecibo message was really for us. They didn’t have any expectation that they’d get a response, certainly not in their lifetimes, because they sent it to stars, as you say, that are thousands of light years away. And it was just one very brief message.

Jason Wright:And so they’d have to be listening to the Earth at just the right moment when that very weak signal arrived for them to know anything about us. So I do think that things like that, the Voyager records that Carl Sagan helped put together that are right now headed off into interstellar space, the plaques on the Pioneer probes headed into interstellar space with messages inscribed on them. I think it inspires humans to think about this problem, to think about what it would be like to actually contact other life. As far as whether we should do it because we’re trying to get a response, I think it’s very unlikely that we can do anything more obvious than we’re already doing with our radar and the pollution and the atmosphere and all of our other activities. I think all of that is much more obvious than any of these feeble little messages.

Jim Green:Yeah, actually I liked very much the way you said that and that is: those messages are for us.

Jim Green:So Jason, thanks so much for a really stimulating discussion on technosignatures and what they are.

Jason Wright:My pleasure, thanks for having me.

Jim Green:Well, join me next time as we continue our journey to look for life beyond Earth. I’m Jim Green and this is your “Gravity Assist.”

Credits:

Lead producer: Elizabeth Landau

Audio engineer: Manny Cooper