Sixty years ago, famed physicist Freeman Dyson theorized that advanced civilizations, in their ongoing quest to find more living space and energy, would convert their solar system into a megastructure enclosing their star. This came to be known as a "Dyson's Sphere," a concept that inspired countless variations and other megastructure concepts. In this week's episode, we delve into some of the more exotic ideas and how they could be searched for by SETI researchers.
Neil Blevins' artwork: http://neilblevins.com/
Centauri Dreams (Paul Glister): https://www.centauri-dreams.org/
Episode 105 - Megastructures (Part II)
The authors acknowledged that this podcast was recorded on the traditional unseated lands of the Lekwungen peoples. Hello and welcome back to Stories From Space. I'm your host, Matt Williams, and today I wanna pick up where we left off last time talking about mega structures.
To recap, a megastructure refers to the theoretical idea that advance civilization in its living space and energy would eventually create an artificial structure that could enclose part or all of its star system consistent with a type two civilization on the Kardashev scale.
The most well-known example being a Dyson sphere or Dyson structure named after physicist Freeman Dyson, who first proposed it in 1960. Rather than being just a interesting or fancy speculation, Dyson's purpose was to propose the kind of techno [00:01:00] signatures IE examples of technological activity that scientists could look for as part of the search for extraterrestrial intelligence or SETI.
And as I said in the previous episode, many, many variations have been suggested over time, ranging from Dyson swarms to Niven Rings. And in addition, there's a number of what we might call type one plus mega structures that have also been proposed over the years, and even a few that deal with a civilization that has advanced and progressed to the point where it's able to harness the energy of its entire galaxy.
So today we'll be getting into all that, and in the last episode, we talked about a Dyson Sphere and a Dyson Swarm concept known as the Matrioshka Brain. The Niven Ring. Proposed by Larry Niven as his own take on a mega structure that would enclose a star, [00:02:00] and how these concepts have been explored by SETI researchers and how they've also been represented in popular culture and science fiction. And as I promised today, would feature some of the more exotic concepts.
So without further ado, I bring you the Alderson disc, the next major megastructure in our series, our exploration here, and this one I'd find especially interesting because it seems a rather novel idea and there's all manner of questions about its practicality, but it is a pretty beautiful concept, and it's named for Dan Alderson, who is a scientist at NASA who wrote the software used to navigate the Voyager one and two probes, which are currently an interstellar space.
The concept also known as the disc world, and essentially it means a flat-out disk builty around the ecliptic of the star – so right around its equatorial region - [00:03:00] and at a distance where planets would typically orbit, that's where the disc begins.
There's a hole in the middle with the star. And then as you go throughout the disc, you are treated to environments that are increasingly hot towards the star and increasingly temperate, and then cold and frigid as you move out. And so the idea here is to simulate all of Earth’s natural environments. This is a good idea because of course, as we've learned from all of our studies of Earth's climate and its ecology, you need to have these different environments there in order for life to replenish itself, in order there to be the right kind of climate cycles that lead to the renewal of living systems.
In addition, because of around. [00:04:00] On the surface, both would be treated to perpetual twilight. And so here too, like with the Dyson sphere or other proposed mega structures, you'd need a series of solar shades that co orbit with the disc in order to simulate nighttime for one section or another as they're moving around night sweeps on the disc there.
It would probably be wise to have two solar shades, so that way you can darken two quadrants of it at any given time while the other two quadrant experience daytime. And like many mega structures I've talked about here, there are artistic concepts which are really quite breathtaking, not the least of which is by the artist Neil Blevins.
And I have the picture of the Alderson disc before me. And to describe it, you have what appears to be an inner ring where it's baron and the atmosphere is [00:05:00] picking up heat and moving outward and beyond that is the ring of, looks like desert. Gradually giving into grassland and temperate land with oceans intermixed.
And then at the outer edge you have a big ring where it's all icy and glacial. And the idea here is that on this disc, you could inhabit both sides of it, and the amount of living space would be exponentially greater than what we currently have on. And there would be barriers at either end in order to contain the atmosphere, but the atmosphere remains on the disc because the thickness of it ensures that it experiences gravity, which depending upon the thickness of the disc, could be as much as Perth gravity or whatever a species, an advanced species is building this whatever they consider to be normal.
And because the mechanical stresses on the disc, this is one sort of drawback or hold in the [00:06:00] theory, those stresses would be so intense that no known material would be able to bear them. So much of this disc, a foundation layer, if you will, would have to be created of some kind of super material, something akin to adamantium.
Uh, next up, as promised in our previous episode, you have the Shkadov Thruster. Now this concept is particularly interesting and appealing to me because it is science fiction gold. Though one could say the same about all megastructures, I find this one particularly fascinating.
In any case, this concept takes its name from the Russian aeronautical engineer Dr. Leonid Shkadov, who provided a description in a study he published in 1987. Called the possibility of controlling solar system motion in the galaxy. But in fact, the idea itself was mentioned prior to that by a Swiss scientist and [00:07:00] astronomer, Fritz Zwicky, who during a lecture at Oxford University in 1948 talked about how human beings could accelerate:
“[T]he sun to higher speeds. For instance, 1000 kilometers a second directed towards alpha cent A in whose neighborhood our descendants might arrive a thousands years hence.”
However the credit does go to, because his treatment was more detailed and of course it was published, tends to be the way that works. And so the explained his concept in his paper. He said:
“It is shown that if a screen reflecting solar rays is positioned stationary, it's at some distance from the sun, the central radiation in the sunscreen system will be violated and a force disturbing the sun motion will.”
So in essence, the idea is to build a Dyson structure, but it would enclose only one half of the star. And [00:08:00] meanwhile, you'd have another structure that extends at the back, which is designed to focus the Sun's energy and direct it. And that would most likely be away from the ecliptic, away from its equatorial region, whereas the structure would sit on top relative to its North pole axis, and all the planets could orbit within this big volume.
And as he said, it would be reflective on the inside. So this would allow the sun to push this massive structure, but given that this structure itself is so big and the sun would be gravitationally bound to it. Everything moves. The entire solar system moves with the megastructure through space, and as Vicki described, yes, this would be a concept for transporting our whole solar system and our people to the neighboring star Alpha Centauri.
Now he estimated that that would take a thousand years, which is a, a decent estimate there. But of course, this [00:09:00] structure, unless the reflective surface can turn off and the sun's rays are no longer being focused on it in such a way as to propel it. The structure could just keep accelerating. So it could be a means of exploring the galaxy or even the universe at large, because relativistic speeds a fraction of the speed of light would actually be possible over time.
And of course, you would have the ability to live on your home planet within this, but at the same time, you could have a living spaces created on the mega structure, not in the reflective part that's being hit by all those solar arrays. But around the rim of the structure and that kind of volume coupled with the planets inside could allow for billions or even trillions of members of a species to travel through.
This proposal is especially interesting because astronomers have detected several [00:10:00] Hypervelocity stars in recent years. In recent decades, and these were stars that were essentially kicked out of our galaxy due to interaction with its supermassive black hole at the center, Sagittarius A. Which may have been the result of a binary system that got gravitationally perturbed, and one star was spun off and thrown out.
And as Professor Loeb at Harvard University, as he proposed in a paper back in, I believe it was 2016, where he said that. Hypervelocity stars could retain their gravitationally bound planets, thus being able to transport life, assuming there are any habitable planets within the system. Being able to transport life from one galaxy to the next.
So this could be a means for which intergalactic panspermia takes place, as I said, fascinating. Now in terms of how you might search for these. [00:11:00] As Dyson said in his original proposal paper that such a structure could be searched for by looking specifically for large sources of infrared radiation that otherwise had no business being there.
And as we addressed last time, basically that would be the result of heat being radiated outward from the shell that enclosed the entire star and/or star system and astronomers would be able to discern that, assuming they had the proper instruments. Something sensitive to infrared radiation, something akin to the James Telescope. Dedicated to looking at our galaxy.
It is for a Niven Ring. I regret that I didn't get into this last time much. That would be much harder to detect. Now, it would be possible to seek out thermal emissions that could correspond to a mega structure, a ring-like structure. But [00:12:00] I think the best bet would probably be. If you're catching that system edge on where the ring is essentially wrapped around the sun's ecliptic or in a halo configuration, not referring to the video game, but rather orbiting pole to pole.
So if it's perpendicular to the sun's ecliptic. That would cause the star to dim by an appreciable factor. The only problem is you wouldn't have anything to compare it to because it's not like the ring structure is passing in front of the star and then not, however, it all comes down to the orbit of the ring itself.
But there might be options if you could image the system directly, you would see a disc there, a very thin disc that was luminous. So something like that may someday turn up when surveys are looking at stars to try and discern if they have debris disks, which [00:13:00] astronomers are doing right now with Webb to capture early solar systems.
So these would not likely exist. Niven rings around young stars. And that's exactly where we're looking young stars to see debris, discs so that we can catch a planetary system in the early stages of formation. And as always, it's a very, very long shot to say this, but maybe we have detected a ring-like structure that we thought was a debris disc but isn't, and simply didn't know it.
As for. They would be particularly difficult to discern because if we're talking about a shell that constitutes just layer upon layer of computing material, then yes, it would be the same as looking for a Dyson sphere. Look for the radiated heat. But if we're talking about a massive series of fogs, right, [00:14:00] nanotechnology or even smaller Femto PCO technology that are all gravitationally bound together.
Then some amount of visible light might still escape, and you'd also have the radiated heat on top of that. So it would be a very faint optical signature. So very, very faint, invisible light, and very difficult to see, but more visible in terms of infrared. So it may appear in our data as a very faint red, giant star.
So that too, it would be interesting to see that in fact, there are examples of such really faint red giants out there, which could possibly another huge long shot be interpreted as a matrika brain or Dyson swarm. And similarly Dyson swarms that are rigid structures like a series of islands in space, as I spoke about last time, those would be rather interesting to look for because [00:15:00] they would appear to optical telescopes like a variable star, which astronomers have already cataloged countless examples of.
However. Period would correspond to a very natural orbit of large scale structures. So the cause of the dimming would not be immediately evident. Scientists would be able to say with relative confidence that's not a Cepheid variable or a RR RA variable. The dimming period would still be very, very regular, meaning that it would occur at certain intervals, which could lead scientists to predict them quite accurately.
Which brings us finally to the curious case of Tabitha Star. Orian Star, and for those who are not familiar with this very interesting story. [00:16:00] It was in 2016 that Tabby Star, which had been known to astronomers since the late 19th century. It was at this time that the star began to dim noticeably. And its variability is something that had been noted before, but at this point in time, it was a team led by Tabitha Boian, which earned the star of the nickname Tabby's Star or Boyajian's Star.
They noticed that it was fluctuating in terms of its brightness, rather curiously, and this led to a whole chain of speculation. There was no explanation for why this was happening. Certainly nothing within the realm of, well, it's a type of variable star. This is predictable and so forth. Rather, astronomers were noticing from 2016 onward that the variability, the dimming and brightening [00:17:00] again, was not something that they could explain by means of natural causes, and several attempts were made.
Much like the case of UA mua, nothing really seemed to fit. Nothing seemed to resolve the behavior, the patterns, at least not perfectly, you know, at least not completely. And so this did lead to speculation that perhaps just perhaps. What we were seeing was the result of a extraterrestrial intelligence that had built a megastructure around tab star and that it was transiting and therefore causing these patterns.
Now, of course, as I mentioned before, if in fact a mega structure orbiting the star, if it was a Dyson structure, it would have an orbital period that was predictable. Something that would be subject to [00:18:00] repetition and therefore scientists could say, yeah, no, that's definitely something's there. If not a planet, then something else.
But suppose an alien mega structure was derelict that it was still orbiting a star, still bound to the gravity, but it was no longer orbiting in a controlled fashion. It was just. Subject to the eddies and tidal forces of the stars gravity and say, solar, wind, then perhaps that would explain what we were seeing there.
Now, of course, that was always considered the absolute long shot, the remote possibility, but it was one which to this day cannot be fully ruled out and we're not saying it's aliens, we're saying can't rule out that possibility.[00:19:00]
There is fluctuations in their luminosity, which doesn't appear to be the result of their just natural variable nature, and given the fact that dips and luminosity of a star, these are used for the purpose of detecting exoplanets for one thing that is so-called transit method, which basically describes how a planet passes in front of its star relative to the observer.
That being us. That is seen as a possible indication that a planet is passing in front of its star, and if it's regular, if it has a discernible period, yes, we can conclude that that is in fact a planet. And based on the extent to which the luminosity drops, we can say with within a fair degree of accuracy, exactly how big that planet is.
But of course the fun and [00:20:00] fascinating thing about all that is if we were seeing an artificial structure pass in front of the sun, then it too would be causing the same type of dimming pattern. It's just that there would be other techno signatures involved there. We would be able to discern certain indications of technological activity.
And Tabitha Star is one where follow-up investigations were conducted by Breakthrough Listen, that massive set program that's been conducted since 2016 by Breakthrough Initiatives. They did look at Tabitha Star and they discern no evidence of radio transmissions or any kind of artificial electromagnetic phenomenon that would indicate that yes, these are not naturally occurring things.
Somebody is modulating this type of energy, these frequencies there in order to communicate or what have you. That for a, and the [00:21:00] types. That's a very interesting case right there because what we would see, what astronomers would see with their instruments would vary depending upon our position relative to it, basically whether or not we got an inside look at it.
So if we're seeing it where the star is facing towards us and its mega structure is beyond it, we would get a very, very convoluted signature. We would be seeing quite a bit of energy in the thermal range. We'd also be seeing lots in the optical range, so it would be very, very difficult for scientists to really untangle these signals and for them to conclude that they were, in fact seeing both a star and a mega structure in its system planets there in between.
That would take some incredible detective work on behalf of astronomers. More to the point, they'd have to [00:22:00] assume that they were looking at something like this. It would be really hard for them to untangle those signals unless they already knew what they were looking at or assumed what they were looking at.
On the other hand, if you're viewing it edge on, you are getting, again, both, but the optical signal would be limited and the thermal signature would also would be much larger and they would appear to be. Almost right next door to each other and also overlapping. So that too would be very, very interesting to see.
And of course, if you're seeing it from the front end or the uh, top end, however you wanna put it, if you're seeing only the mega structure, the star is beyond it and therefore not immediately visible, then you're getting a big thermal signature, at which point scientists might assume yet again that yes, that is a Dyson.
And they would be partly right. It's like it's a Dyson structure, but it's also moving. And the fact that it's moving [00:23:00] right either towards us or away from us, that would have an effect on the wavelength of the light that's coming to reach us. It would be Redshift. And since Scada thrusters can get up to relativistic speeds, a fraction of the speed of light, it would be not hugely redshift, but certainly enough to to be noticeable.
But what's really gonna make your noodle here is what if this star and this mega structure were actually passing by the solar system, right? At one point, astronomers are seeing it looking directly at the mega structure itself, and it's like, yeah, there's a big thermal signature, and the infrared readings we're getting, this is coming closer to us, which would immediately set off a million alarms.
And would of course, fuel speculation almost immediately that, oh my God, this is an artificial structure. Most likely, perhaps at least [00:24:00] that would be one theory, but it would be difficult really to explain otherwise. The only other object that would produce such a signature would be a brown dwarf, visible only in the thermal and in infrared, and given the size of the signature of Brown Dwarfs are very, very small.
Whereas something capable of encompassing an entire star system is huge. And if it were a red giant, it would be producing an optical signature. Still just a faint one, but still visible. But as it drew closer to the solar system and eventually made a fly by. You would start to see it edge on and suddenly the signal would be rather confused again.
It's like we're getting both an optical signal and an infrared signal, and yes, there's the overlap and they're both kind of there. And then as it went on its way, as it made its way past our solar system and was retreating off into the distance, we would now be getting the optical signature on top of [00:25:00] the big thermal signature.
That thermal signature being produced by the inner part of the mega structure of the thruster and its reflective surface. And so that is an idea I intend to write about someday. Just the possibility that such an event would be happening and it's not a stellar fly by scientists would determine that pretty quickly.
But as to what it really was, that would be something that would keep us just, it would have our wrapped attention for as long as it took for it to make its fly by. And then of course, well, much like a, there would be all these proposals to send a mission should we ever see one again. Hopefully such an event could take place at a time where a mission is already ready to go.
It's like we've got a ship here that's capable of rendezvous with interstellar objects and this one's gonna be passing beyond the edge of the solar system. Hopefully far enough away that it's not perturbing the solar system and any objects in the [00:26:00] outer reaches of it. 'cause that could be catastrophic for us.
But yes, a ship that could immediately head off and run with it as it's swinging by. And then we'd have a mission to say, oh my God, are you seeing this back home? We are witnessing a massive feed of engineering from clearly a very highly advanced species. And are any of them actually here, are any of them residing on the mega structure itself or on any of the planets that are contained in the system?
Oh, we intend to find out truly the stuff of science fiction dreams like rendezvous with Rama, but taken to another level. And so as I said before, these are all examples of type two mega structures, the kind of things that a civilization would be capable of once they have mastered their entire star system and have the ability to harness all of their son's energy.
And as [00:27:00] hoped, this means that type one mega structures or type one plus mega structures. The types that have been suggested in more recent years, and which are just very, very numerous and very interesting and also very fun to think about. It does give one a sense of this is something that humanity could also create someday.
Although, whereas Dyson structures are something, be a very far off. Type one plus mega structures is something that could be done conceivably within a few centuries from now. And so a little bit more down to earth, although we're talking about mega structures. So that's a very, very relative statement, and that will be the subject of our next episode.
So thank you for listening in. I hope to include as many visuals as possible with this episode so that people are able to see exactly what I'm referencing. But as noted, [00:28:00] you can find examples of artwork that envisions what these structures would look like and offer a bit of a primer, a bit of an explainer about them. And two very good sources.
There's Neil Bleviens. He's a graphic artist and he's done a whole series on megastructures. And he's got galleries you can access online.
Also Paul Glister. He does not do the artwork, but he has through his websites, Centauri Dreams, lots of very, very good detailed posts on all of them, what they are, and information on how scientists have actually looked for some of these, how they've gone through archival data looking for, say, infrared signatures that could be indicative of a Dyson structure.
So all very, very interesting reading and I will include their websites, the, ULS for them in the show notes. In the meantime, thank you for listening. Stay tuned for part three [00:29:00] on this mega structure series, and as always, I'm Matt Williams, and this has been Stories from Space.