NASA Technosignatures: "Moderately advanced" technologies in transit
In, the thinking. The organizers, for inviting me to be here it's. I, feel, that I feel honored to be in this very exciting, meeting and have, the opportunity, to interact, with you all, thank. You also for they you thank, you also to the lunar and planetary Institute, organizing. It and also, NASA for, making this possible, I. Just wanted to mention that by. Supporting SETI, research. I, don't, know if you guys are NASA know this but. You're. Not only helping, the project you're funding but, also, elsewhere. In, the world this. Is very helpful for SETI, projects, I see. Claudio nodding back there do you agree with that so. Yeah, Thank You NASA for for this and, I'm, going to talk about. Moderately. Advanced technology, in transit I will, explain, what I mean by this in a minute but. First I wanted, to note that. Transit. And I think, in general in SETI it's, fair to say that we. Have a problem because the. Technology. That we have to observe to, try to observe what alien, civilizations are doing, is. Still very limited to the point that we wouldn't be able to detect ourselves. At interstellar, distances so. Our own tech nurses, will, not be detectable, by us interstellar. Distances I think. This is a fair. Statement. Unless, you get extremely lucky and. Something. Happens like the, aliens, message, to you or something like that but, if you're searching for something. We. Basically. Yeah. Like I said we don't have the technology to see ourselves interstellar. Distances but, this has. Improved. Over, over, the years because. Some. Decades ago in, the 60s Freeman, Dyson was thinking about really big things like. Dyson, spheres and. We. Were hoping. That the aliens, were building really really big things big. Enough that we could. See them right now we have better technology and we. Are still hoping that the aliens are big in build big. Things but, not as big as we were expecting, the sixth right now we are thinking about planetary. Scales. That's, the sort of things that we can see now so, this this has been improving this situation, and, so because of that I would like to what. I call to, show what I call their technology, balance equation, which is if you can parameterize the, technology, that we have. Basically. The, product, of our technology, times their technology, is a constant, as we improve our technology the, alien. Technology that we can detect goes down and so, I can define a proper, set of units in which these constants is unity. And, of course that the units in which we are able to see our techno, signatures at interstellar, distances, that's a unity okay so. By definition, our. Technology. Ranking here is smaller. Than 1 because, we are not yet at that point where we can see ourselves and, the, aliens, that we can. Hope to, detect. Have, higher. Than 1 okay so this may be another classification, of, alien. Civilizations I, like. To call it little brothers, and big brothers right. This. Means that when we make. Hopefully, some, time soon our, first contact we will be contacting, a big brother we will be contacting, a civilization. That has the capability to get. In contact with civilizations. That are more primitive, and. That's us, but. This. Is interesting because the these. Two types, of civilizations, have very different interests, and the philosophy, of SETI is very different for little brothers and big brothers the kind of questions, that you would ask is completely different and. I would argue in. A few minutes that, we are not far away from the transition, I think, in a matter of decades, centuries. Maybe, we. Will reach the, transition, between little, brother and big brother we, will start, being able to see ourselves at interstellar distances and, at. Some point in the future we will be able to detect, more, primitive, civilization. Excuse, me for using this crude, nomenclature. Of advanced and and and primitive, but I think you understand what I mean and so, we will become big brothers and that's a big responsibility, but.
There's This this. Interesting, fact I think apparently. The first contact of little brothers has. To be with big brothers and that's that may be a good thing because. Big. Brothers probably have. Already, passed the longevity filter. Which. Gives you higher chances, that maybe they'd learn to, live. A more sustainable, existence. So, so that might be a good thing. But. Anyway. They. Kind of transit, techno signatures, that we that. We have explored. So far more or less what we have here. In this line and Jason, has been talking, about Dyson. Spheres and some of the things the these planetary, sized objects. Of look Arnold. In. My talk here I was invited to talk about moderately. Advanced, technologies. And by, that I mean here, these, two, proposals. They, were by Eric. Korpela, and collaborators, were. Basically, you will have giant, mirrors in geostationary. Orbit, of a. Core rotating planet a tidally, locked planet. That. Basically, can help a civilization, to. To. Illuminate. Or to heat the dark side of a planet, and. Then I will I will talk about this. Clarke, EXO belt proposal. Mmm. And some derivatives, of that and. So I selected, this because this is the sort of technology that we. Its. Technology, comparable to the one that we have so we are talking here about putting. Satellites in orbit basically. Whether it's mirrors or the satellites that we are used to thinking about that's, the sort of devices. That we are talking about so it it's. Not really something that is out of our possibilities, in fact it's completely within our reach to develop. These these. Techno signatures right now maybe. We haven't, done. It we haven't had the motivation to build these mirrors or to. Create a very, densely populated Clark, EXO that or Clark Clark belt. So. Regarding, me well yeah. I forgot to mention something what. I'm going to discuss in this talk it actually applies to both of these techno markers right I'll be I'll, be using the Clark EXO belt as a reference, but most of what I'm going to say also applies to the decor. Nightside, mirror and. So. This is this is a paper about the Clarke XO belt it's very recent from from March so many of you probably. Are not aware of it but, I would like to invite you to take, a look at the paper you, know since I'm here you can ask me during the the, coffee breaks any.
Questions You might have about this. But. Just. Let me go through it very quickly this. Picture came, up before, in, Sara's. Presentation, and this. Is a representation, of, the satellites, orbiting, Earth right now. And. You can see that there's basically two types of satellites first of all we have these satellites, here orbiting. Very close to Earth this is the low Earth orbit, and it's basically the first thousand, kilometers, or so and then. Much further out we have the geosynchronous, well, the geostationary, in geosynchronous orbit, and and. The, forming. This, ring. Of, satellites let's. Call it belt. Because ring has other implications in, astrophysics. Which. Is often referred, to as the Clarke, belt. Because our. Thor see Clark was one of the pioneers. In developing. Or. In. Realizing, and doing work on. You. Know showing the importance, of these of, this orbit for, in. This case for telecommunications. But I think we'd learn over the years that this is useful not only for telecommunications. But for many other things. So. Technological. Civilizations, might have an interest in putting. Devices. Artificial, devices in geostationary, orbit and this. Is a very interesting technological that we can explore there's a very nice, thing about this technological it's oakum, friendly, and, this is very important, I don't, know if you've noticed but there is a conflicting. Relationship. Between SETI and now come to Razer right. Because. You. Know whenever. At. Some point you find some anomaly, that you think might be due, to some. Extraterrestrial. Intelligence, at work you. Always have to make sure that you have ruled out all other possible, natural explanations, first. And, Jason was talking about how hard that is there's. Lots of confounding, factors, and. You, know let's face it whenever you find an anomaly. There's. Many. Possible. Ways to explain it in due.
To Natural reasons. Now. This is one of the few things, that you can do if, you ever detect, if you can be sure that you've detected something. At. The geostationary, orbit. Of the planet then. You can be pretty, sure at least that the most or, the simplest explanation is, to. Assume that it's, artificial, right, so, it's one of the few techno markers that will actually be compatible, with Occam's, razor because. You, know there's no natural processes, that we know of that, will put rocks. In geostationary. Orbit however. Civilizations. Will probably have an interest in doing that. So. That's that's, interesting. This, animation, shows the, the concept we have in mind here when we talk about the cortex so well so. Basically we have an exoplanet, that's surrounded, by large number, of satellites, in this. Geostationary. Or geosynchronous orbit, and. This. Of course the, density here is exaggerated. A little bit, but. So. That so that we can see it but what I wanted to show, here is that there's, here, at the edges you can see this is a very very. Nice thing for us because. Of projection, effect even. If you have relatively, low density of, objects, here at the edge they, all by projection, that the projected, density becomes much higher on both on both edges right so, this means that even a relatively low populated. Load. Even. A belt with a low, density of, objects will, have these, distinctive. Features, at the edges which might be interesting, to observe in transit, so. You. Know you can imagine I really, like these animations, by the way I think they're really cool if, any of you is interested in having them for your outreach presentations, or whatever let me know but. You can see here how these edges, of the belt look really dark in, the transit, and this. Is one of the. The clues. That will give away the presence, of, something. Like this. It's. Kind of what we're looking for, if. You have, not. Very good observations, of this if you don't have enough signal-to-noise, ratio. When. You start looking at this you can think that you have a planet and a moon there's, a lot of people now looking for X and moons for, many reasons, and.
So, When you look at this your first natural, explanation, may be to, say well yeah there's a moon I found, them on you get excited because because. Moons are rare, but. Then you see there's you get the moon then you get the planet, and then. Behind. The planet there's another, moon and that's, that's, kind of weird you have this two, moon symmetrically, located on, both sides of a planet and then you realize you work out the math and you look at the altitude this moon you realize that that moon is exactly, at the, Clark. Altitude. And that's, when it hits you that's, no moon. It's. An artificial device. Hopefully. It's not a planet busting, in Space Station but it's certainly, some artificial device, so. That will be the hope. So. I did some very simple modeling. Very. Simple modeling of what this would look like to compute some light, curves and things like this and. There. Are some results in the paper. About. What you. Know humanity's, belt might look like from other stars or what. We might be able to observe, in other, stars. Just. To answer well. Try to answer the question can we. See these, belts and, turns. Out I tend, to be definite, answer because it depends, again of the, technology. Balance so, for any given. Stellar. System, we. Have of course our technology, is fixed but. Depending. On how their. Technology, in this case means how many devices, they have in this in this Clarke belt. It. Can be detectable or not so. The. Ballpark, lives with these simple simulation so you need something in the order of ten to the minus five, ten to the minus four. Filling. Fraction, of the belt, area in order for us with our current technology to. Be, able to detect these. This. Kind of structures. So. That that's more or less the ballpark is, it reasonable, to assume that a, civilization will, get. A belt that is so highly, populated, I don't, know I have no idea. Quite. Frankly I don't think anybody, knows so we just have to look and see what we get. But, another interesting derivative. Of this is if, we go the other way around and we try to think. What we look like from other stars. You, can try, to compute. The signature of humanity's, clark belt and, right. Now it's it's very very sparsely. Populated but, if you look at the data in the last couple of decades. The, blue line here shows the, population. Of our clark belt and this, is a logarithmic scale okay, so, the orange line is a fit to an exponential, increase. Right. So. What this is showing is, that even. Though we're not using radio communications, as much, as we used to as heavily as we used to somehow. We are still finding these Clark orbit interesting, and we're populating it more and more the. Interesting thing is that if you extrapolate this.
Into, The future and. I don't know if it makes sense to do this extrapolation, or not but if you do it then, you get into this 10 to the minus 4 ballpark, by the Year 2200. Okay. So. This means that if, this trend continues. By. This time we would be easily, observable, from nearby systems with our current technology not. With technology, of the 23rd, century with. Yeah. With current technology. And. This has implications for many of course because it's controversial, whether or not we should be sending messages to other civilizations. Well. We should be aware that by populating, our belt of satellites we, are sending, a message it's. Just a matter of you. Know what kind of technology they have to. To. You. Know whether they can they can observe us or not so this is something that should be kept. In mind in this context. I mentioned. Earlier that Nature has no preference for geostationary, orbits. So. This is a very good indicator that, that you have something artificial. The. Question. Is can. We determine for a given exoplanet, what is the de Klerk altitude. And. This is the formula right, this is the radius of the Clarke orbit and, it depends on the planet mass and the rotation, period a very. Nice feature of this. Formula, is that you can see that the radius goes as mass to the power of 1/3, that. Means it's, very weakly dependent on, the mass and this is a very nice thing because for many transiting, exoplanets. We only have a rough idea about the mass we don't know it exactly but, we know the size of the planet and. Rocky. Planets, cannot have an arbitrary density, there is a range of densities, that rocky planets have, and. The spread if you look at the solar system, between different planets, is roughly 40% right. It's not it's not that much actually I think it's 30 something percent, and. If you take the cubic. Root of that that. Means without. Knowing any other thing, without any radial velocity, measurements or anything like that you, can estimate this, altitude. With, an air of of, roughly. 10% so. That that's pretty good. The. Rotation period. Influences. The park radius, as, a power of 2/3 it's. Still less than linear but, but it's more sensitive so you want to have a good measurement of that so. Rotation, is is difficult it. Takes really. Large telescope, there's a couple of papers one by that. Lana birdy Gina and Jeff Cohen who spoke, yesterday but, about, heat anomalies, but. They also have a paper about how you, could use a telescope like the James Webb to, measure the rotation period of an exoplanet. Like. I said it's difficult it takes a lot of time several. Hours on something like the t g WS t but, they, nice the good news is that if you can determine it it's very very accurate. And. I think if you have a good candidate, and, you want to determine this rotation period because you have a candidate, for planet with, a possible, clerking, so well then, I think it's justified to they'll, give you time. Probably, in any, of the big telescope to go, and make these observations, so. That will help you or that, will allow you to confirm, that, you're actually observing, something, in.
The Clarke orbit. Important. There is a. This. This search is free so we are we are looking about. Transiting. Signatures. We. Have, space. Missions, that are looking for transits, we have lots of projects, there's, a lot of interesting observing, exoplanet. So, the. Transit data are there we, just need to sort. Of you. Know do better modeling, do more effort, trying to predict. What are the features that we will need to observe in these light curves maybe, work on machine learning algorithms. Which are proving, to be very helpful in trying to get signals out of the noise to, sort, of identify. Interesting. Candidate, and. Also do simulations, to identify what are the optimal conditions because like, we, talked about this yesterday, my. Conclusion, from, from the similar, using my paper is that red words are good. Conditions, in terms of detect ability, but. We. Shouldn't put, all of our eggs on that in that basket because we don't know me it may, be the case that red words are bad for life we're not sure so, you have, to balance all the all these factors, and and the uncertainties. But. One nice thing I would like to reiterate is, that. Not. Only Clark absorbers but they need your synchronous. Artifact. Observation. It's. Always the SAT, antagonism, with Occam's razor and, that that's that's. A good, thing. Another thing is that you know we have this synchronicity. Problem, right when we are looking for other civilizations the. Synchronicity, problem means that we both have to be active at the same time in order to communicate. But. Some techno signatures, are actually very long-lived. Like. I don't know Dyson, Sphere for instance I yeah. I don't know I don't know how you make it - it items fear but you, can imagine that something so big in scale, is. Probably very robust, certainly. Robust to planetary, perturbations. In that system and so, you will expect there will be some that will be there for I don't know millions of years. So. It might well happen that someday, you detect, something like that and it turns out that the civilization built, it is not, there anymore right or maybe. Maybe, they began extent or maybe they moved away going somewhere else or, maybe they've gone beyond the technology, horizon. And we cannot perceive the technology. Anymore. Some, other techno markers are short-lived and so, that. Has the well. I forgot to mention so there's advantages and disadvantages, of both short, and long leave that the advantage of a long live techno marker such as Dyson spheres is that it's more likely that you find them because, there will be more of them but. The disadvantage. Is that it doesn't, necessarily. Indicate, the presence of an active civilization, there on. The other hand the short leave the techno markers they, will point. To an active civilization. But. There you, know they will be less likely you have the synchronicity, problem you we. Both will have to be alive at the same time. And. These kind of geosynchronous. Artifacts. Are sort of intermediate, they're. Not as long-lived, they're not going to live for millions of years but. Depending. On the details of the planetary, system how stable they are they, can live for maybe centuries or thousands, of years in the. Case of Earth. But. Also I would like to reiterate these there's, a lot of synergies between this kind of research and extra, moon and EXOR in science, which is very interesting, right now in astrophysics, so. We can we can take advantage of that. There's. One thing that I didn't. Realize when I wrote my paper I don't, take flower cakes of Eltham fortunately which, is that there, was a lot of discussion, about core, rotating planets the Clarke EXO belt of the planet that is tidally locked to, its star.
Only. Later I realized, that there's, a problem with that scenario because, the, Clarke altitude, for a correlating, planet, is. Also. The the Lagrange point altitude, and that. Means that you now have to deal with the three-body problem because, the. Gravitational. Influence of the star is as important, as a planet, and that means that the belt is not, stable. On long time scales okay, I didn't realize that when I when I wrote the paper. And. What that means is that it's. Not impossible that you have a clerk XO belt but it would involve that those devices those satellites or whatever should, have some. Form of propulsion in order to stay in that orbit otherwise, it will not be stable and. Again it's not impossible especially, I mean if you're thinking in satellites, maybe, not. So much but if you're thinking of cities, for example where, they have space elevators, bringing, things up and down then, they might have such propulsion, system but it clearly, the whole scenario becomes less appealing. Because. Of this instability. However. There's. Another interesting perspective, is that we call. Rotating planet the Lagrange points are obviously very interesting. The. L1, and l2 points, I mean, l2 is a perfect place for these mirrors, that will illuminate the dark side, l1 could, be a good place to put a shade. To. You. Know reduce the the solar, the. Stellar irradiance. On the day side whatever so. You might think that the these will be very special point where day civilizations, will put lots of satellites. And. Then in that case I, have. Done some some work on trying to figure out the problem of. The. Program that you have with this Lagrange, point is that it might be interesting to look at but, at some point they plan it during. The transit will occult the Lagrange, point before. You. Get a transit, from the Lagrange point right so this will be the limiting situation, is, the Lagrange where, the Lovgren devices are and this will be the planet, in, this situation the planet, will, obscure. This. This. Lagrange. Spot. During. The transit so you will not see it that's, what I'm trying and, so. The. Conditions, in which these points, are visible it is an important thing it. Turns out when you do the math it you. Have to take into account geometry. And also astrophysics, which is because the size and the, mass of the star is relevant here turns, out that for a tiny. If, the size of the Loranger.
Let's. Call it swarm or whatever if, this size tends to zero. Then it's only going to be visible for big stars like bigger than 1.6, times the Sun. But. Anyway we cannot, see really tiny things we are saying that we need to for. Something to be detectable, it has to be planetary. Scale. Sizes. So. If you have something that is a fraction, of the planets size then, you can see it for lower. And lower stars, so. That's a limitation but you need to to, consider that and, then, it's very interesting because the light curve, Jason. Was talking about things. That change form or change size, during. The transit this is exactly what would happen here if, you have I, don't, know something, big a city or a swarm of objects, here what you will see is that during, the ingress. This. Will look like a big structure because you'll have the, Legrand's. Thing and the planet and then, as the planet covers, the background spot, then. You lose it you only see the size of the planet so you will see a planet that is bigger at the ingress and it becomes smaller and then, during the egress it becomes bigger again that will be the signature of a. Planet, we fit very. Densely. Populated. Part. And. Then some configurations, about rings this. Is just to say that the, Rings rings. Are very important we have observe over 3800. Exoplanets, none of them have rings right, and there is a big question why why. That is the case and. So. It might be actually, if you look at their own solar system you realize, that all the outer planets, have raised and, even some of the minor bodies, but none of the inner planets have rings and so, there's a there's, a hypothesis, by by head man who proposed that maybe, rings need eyes and, he has an explanation why, that needs to happen you, need eyes to form rings, and, that would explain because our exoplanet, search is biased towards planets. Close to their star so, that will explain why we don't have rings but. Rings. Are very interesting, because it tells you about the inner dynamics, of the planet. This. Is my last slide. There, is an intriguing thing, with a new class of planets that are being found in transit. And. This. She said Neptune's these are big. Planets, that has anomalously. Low density. And we're finding it big, class. Of these, and Anthony. Pyres suggest in a recent paper that this could be actually rocky planets with rings maybe we don't, have the resolution to see these rings and we misinterpret them, as puffy, big planet. But. Many, thing what about you, know I mentioned these lower. Orbit. Satellites, here that they're very difficult to see but, actually this is what they would do this low orbit, satellites, will make. Your planet look bigger than it actually it, actually is, without increasing, its mass so I wonder, if, you. Know maybe this is right also - that. Not. Saying it's aliens but we should check just in case thank you very much. We. Have time for one very quick question and we'll start the transition to the next speaker. Hi. Great great talk -. Two comments one maybe. It's Larry Nivens Ringworld. That.
Would Really give you a second. Luminosity. Of Earth is leakage. Radiation, of Earth has been, essentially. Invisible to, the stars to date when, star, shot what's the project that's underway is, built it, would be farm, many. Many orders of magnitude brighter. Than anything before it'll be visible anywhere in the galaxy I hope, I can talk about that tomorrow because. I think power, beaming leakage, is going to be the most visible thing, techno, signature, that a civilization, will produce right. But that's a focus in one direction. That. Those are beams that, go in one direction they're not isotropic so, that's why I said you you have to be incredibly lucky to, be. So. You'll be detectable in that direction. That's. True and of course that's true a planetary, radars too. Great. Thank You Hector.