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Notes -
Ahem :
And even before the SETI article:
Need I remind you that we shouldn't be looking for "just" a single Dyson swarm candidate? A civilization with the technology to build even one should be in the process of a Grabby Alien takeover of the lightcone. You'd want to see a roughly spherical wave of expansion, perhaps including swarms-in-progress.
When the technosignatures, scrutinized closely, overwhelmingly tend to turn out to be well explained by natural phenomena? Yeah. We ought to check, because it's cheap and possibly quite important if we detect something real, but expectations should be very, very low if you're modeling things sensibly.
I think the natural phenomena explanation is more likely. (Like I said, I don't think we've actually spotted Dyson swarms.) But the truth is more complicated than "oh well we would know if they were out there." The fact that we might know if someone built a Dyson sphere tells you something about how much we don't know.
Maybe - I don't actually think Dyson sphere are very likely to be built, even by an advanced spacefaring civilization. Swarms are slightly more likely, but even then I don't think the fact we haven't spotted them. And I don't actually think the scenario where Grabby Aliens start making Dyson Swarms in the entire galactic neighborhood is a given, either.
You've found one paper arguing that one candidate is explained by natural phenomena. I think it is most likely all of them are explained by natural phenomena but, again, what sort of argument is this?
"We can say confidently there's no aliens because we looked for one extremely difficult to build megastructure of questionable plausibility, found multiple potential matches and we're pretty sure one of them is explained by a natural occurrence" is just a bad argument. I would bet every single one of these SETI findings is due to some natural occurrence, but that doesn't make the argument good!
The real argument, at least the one I have implicitly and explicitly made, is that we need a good explanation for why there's such an abundance of untapped negentropy in the wider universe, which would be extremely unlikely if there was a civilization out there with even a minor (in geological terms) headstart on us.
As any good Bayesian will tell you, an absence of evidence constitutes evidence of absence. It's not "proof" of absence (that nonsense is for Popperians), but the more you should reasonably expect to see something and then not see it, the more questions that raises.
You should know very well that even STL interstellar colonization is well within the reach of civilizations not that much more energetically or technologically advanced than us. We don't see it. Every single candidate we look at closer turns out to be a bust. I've shared a few examples, but that's not an exhaustive overview, there are other discussions I didn't link to. The point is that "almost certainly not aliens" is clearly true for technosignature claims. If there are any examples where we haven't conclusively proven otherwise so far, it's exceedingly likely that there's a boring explanation. Not aliens.
There's no shortage of such good explanations, such as the Dark Forest Theory, the Aestivation Hypothesis, and of course Greg Fodor's Intraterrestrial Hypothesis (which of course if expanded universe-wide would explain very neatly the lack of mega-engineering.) "Grabby aliens" is just one model of how advanced alien species might behave based, essentially, on pre-modern human behavior.
The Dark Forest is a terrible explanation. Others have written on the matter before, and I'd advise you look that up first.
If not, I will address that in detail.In fact, I've written it upThe Dark Forest theory just doesn't make sense on its own terms.
A civilization with access to exponential self-replicating probes is very hard to eradicate. The offense and defense equations change drastically when the latter have massive advantages in mass as well as the ability to disperse.
Further, it doesn't take imaging technology much better than ours to spot biosignatures from the other side of the galaxy. An inferometric telescope maybe an AU across in terms of effective lens size would work just fine. With better modeling, you could simply predict which planets are likely to be habitable, and then RKV the fuck out of them a few hundred million years before they develop multicellular life.
You can launch from distant outposts, outside the galactic plane even, a delay of decades or centuries means nothing on those time scales. No need to make your own system the obvious target. But in return, any civilization close to a Type 2 in terms of energy budget has the ability to sterilize the galaxy and barely notice the expense. They're also likely so dispersed and decentralized with off world outposts and robotic manufacturing and infrastructure that simply blowing up their home planet or razing it with a Nicoll-Dyson beam would only be a mild inconvenience. And there's no way to hide when you have one of those, that we know of.
If there were highly advanced and malevolent civilizations lurking out there, barring truly out there technologies and an implausible ability to cover their tracks in terms of emissions and signatures from before they knew how to start hiding or even the ability to do so, then there is simply no sense in trying to hide.
You should aim to get as big as possible, as fast as possible, if your Von Neumanns arrive at a system that's actually home to a hiding super-civilization, well they'd have found you first, but that's a problem tens of thousands of light years away. If they RKV you, so fucking what, you've got outposts past the Oort and can amass teratons of fuck-you in return. Your best bet is signaling that you're too big to fuck with, and the only way to get there is to grow.
Thankfully it seems that we're alone in the galaxy or even the cluster, unless there's very good reason why civs would have access to energy sources even more abundant than nuclear fusion and also coincidentally ignore all the lovely stars left free to waste theirs.
You can't hide. You can run. You can make them regret it. If you spot techno signatures across the galaxy, better be sure they won't be capable of sending RKVs back, but that's an acceptable cost, and in the meantime you need to rush for all the empty real estate.
Aestivation makes sense if you've already collected all the resources you can, tidied them up for longterm storage, and can sit tight till the universe cools down and you can exploit the Landauer limit in peace. If you see the stars still burning, that ain't working. You'd expect widespread star-lifting or intentional gravitational engineering. Aestivation without collecting resources? That's like putting $5 in the bank when you're a child and then hoping that works as your retirement fund. You need a job, or you should have a job.
Fodor's take is braindead. Yeah, sure, we can digitize and live in VR. Doesn't stop space probes and VNRs from being sent out. That is the default expectation.
Grabby Aliens is enormously parsimonious and makes minimal claims about motivations. All you need to accept is that STL interstellar colonization is possible, and that most species would want more resources, especially if they're easy to acquire. The beautiful thing is that you can turn the knobs and make things way more expensive or slow, and that doesn't change the bigger picture. There's been plenty of time to start the grab, and there's no evidence that even one civilization in the entire visible cosmos has started the process. All it takes is one.
You just made a big long argument that RKVs are so cheap that you could sterilize the entire universe but also that RKVs aren't cheap enough to destroy every possible outpost made by a civilization that made something as obvious as a Dyson sphere.
Now, setting aside the fact that this does actually explain the Fermi paradox (a prior civilization targeted every planet that was then capable of supporting life) you completely failed to address the downsides of spamming RKVs in universe where there may be civilizations that can produce RKVs: they are 1. likely noticeable because of the heat signature produced by relativistic speeds, even against interstellar particles, and 2. very easy to intercept with other RKVs or lightspeed weapons, and 3. not likely to be reliable against targets at long ranges because any minute error (including errors introduced by unexpected gravitational forces during the intervening travel time) will cause it to miss.
There are ways to mitigate these problems but RKVs are not good weapons against any civilization that might be able to shoot back in the next [distance away in light years] years. Since it is more energy-efficient to defend against them than to attack with them, we would not expect them to be utilized en masse among peer civilizations.
Why would you collect resources when the universe will do it for you? Stars won't be very energy rich near the heat death of the universe, but Sagittarius A* isn't going anywhere, and will likely continue to grow until after the stars burn out (remember, black holes can grow from cosmic background radiation), until the expansion of the universe places all objects and radiation beyond its gravitational reach forever. You could park yourself in orbit and run calculations off of a black hole (which emits tremendous amounts of radiation as it consumes matter, and tiny amounts as Hawking radiation) for an
infinitely long amount of time. This would likely be more efficient than building Dyson spheres throughout the universe; Sagittarius A* has the mass of about 4 million stars and is growing. Right now it would take vastly longer than the age of the universe for Sagittarius A* to evaporate due to Hawking radiation. And because Hawking radiation grows as the size of the black hole gets smaller, it seems arguably perfect for such a plan, since you will be maximizing energy collected at a point when the universe is the coldest. As time goes on and the universe grows colder and your calculations grow more efficient, you also gain more energy to calculate with.The main objection to this plan is that the Hawking radiation output on a supermassive black hole is too negligible to power anything, but I am not sure this holds true if we are orbiting near the event horizon with our Dyson swarm, due to time dilation. (Also you get fried with gamma radiation when the black hole collapses, but whatever, surely you've finished your big math problem or whatever by then.)
However, this is only the second-best plan involving black holes. By creating a small black hole and feeding it mass, you now have an extremely efficient method of both energy production and propulsion. You could (in theory, if you can do the math right) travel around the entire universe at relativistic speeds and feed 100% of the mass into your black hole, directly converting about 25% of it into energy to run your calculations with.
Since our entire point is hibernating until the universe is colder to do the math, the best time to crunch the numbers and figure out how to do this is after the universe is already dying. You'd only need a small "bootstrap" energy source (which might even be something as trivial as a fusion reactor) to run your calculations at that point. Of course, you wouldn't want to gamble on this unless you were pretty sure a black hole starship was possible.
Fodor explicitly discusses this, which tells me you've dismissed his take as "braindead" without bothering to read it (which you can do here). Even if he was wrong about the space probes, it's pretty clear that a society that virtualized at, say, 2200 levels of human technology wouldn't really need to expand to have all the energy they could ever need, and any probes they sent would be much less conspicuous than a DYSON SPHERE.
I would argue that you actually have to accept that most species will pursue ~limitless resources that they don't need, which is a harder pill to swallow. If we assume as a default that most species have no access to contraceptives, this makes sense. But if something like the human experience is the default, we can expect most species to grow slowly if at all by the time they need to colonize other worlds because they will be able to control their own reproduction, and they will not maximize the pursuit of energy resources simply for its own sake (we certainly do not do this on Earth). They will have zero reason to construct anything like Dyson sphere, as they will have no need for the energy. Furthermore, colonizing other star systems without cracking the lightspeed barrier is a very dangerous idea, for obvious reasons: your first concern shouldn't be aliens, but members of your own species developing their own culture in a technologically advanced parallel socio-political environment. No sane species would permit this by default without some sort of constraints. We should expect most species to, at least while their star is still burning, to centralize their civilization around their star system, which will have enough resources for practically limitless numbers of their society without anything besides modest engineering (such as space habitats), and actively inhibit attempts to leave by would-be splinter societies.
Sterilizing planets is cheap. Particularly if you focus on potentially habitable planets, preferably before they show signs of intelligent life.
A K1+ civilization is a little more resistant to bleach. They can pack their bags and move to lower-rent neighborhoods like the local Oort, and which makes total eradication a real pain.
You are no longer aiming for a single planet in a system, assuming your terminal guidance allows for that. Now you've got to kill every asteroid, every orbital, every stealthed facility running cold, probably every rogue planet in the vicinity. Good fucking luck if they're multi-system. And if they've got VNRs, AGI/ASI? Sorry. You'll need to really up the budget or send your own berserkers.
To illustrate. Let's assume a civilization 200 ly away picks up Hitler's broadcast and decides they don't like the mustache. They fire an RKV at 99.9% of c. It'll get to Earth, at the earliest, somewhere past 2340. The solar system will look very different by them, assuming we haven't exterminated ourselves.
I am extremely confused by accusations that I haven't addressed the downsides of indiscriminate RKV spam, particularly if you're targeting systems with budding civilizations or near-peers. Given the speed of light is a rather hard limit, there's every chance they've grown up in the span of time between detection and terminal effect. That gap could be anywhere from decades to millennia, depending on fast the RKVs are.
Hang on a moment. You are quite possibly the first person who has told me that it's "very easy" to intercept RKVs. Citations please. As I've mentioned elsewhere, a sufficiently fast RKV will appear barely any time after the light that came off it. There's scope for (minor) evasive maneuvers, better versions of MIRVs, just going fuck it and exploding early to turn into a macron gun.
In particular, point 3 assumes zero terminal guidance, which is... a bold demand to make. It's hard to steer relativistic projectiles, of course, but not impossible.
And then there are Nicoll-Dyson beams. If you can build one, GG to whoever tries to block them. You can reach across a whole galaxy with ease.
Also, if someone was sterilizing every potential life bearing planet in the Milky Way, I think we wouldn't be having this conversation. At the bare minimum, we haven't been hit.
Uh... What about all the photons that stars are busy wasting right now? At the bare minimum, you should harvest that. Maybe make kugelblitzes with a Nicoll-Dyson beam, if you're more inclined towards civilian applications. Dyson swarms can be dual use.
You forget that you can extract rotational energy from existing black holes with remarkable efficiency (compared to most power sources). It's easy. You just have to drop mass in the right way. Plenty of papers on black hole farming out there. You don't even need to make one yourself, you can happily appropriate the closest one if you can get to it.
You don't have to wait till they shrink and emit significant Hawking radiation. If you do, you're waiting a very, very long time. The Aestivation hypothesis fails because you don't see any of the infrastructure work you need before that wait makes sense.
I have read it. I found a Medium post. I still think it has severe hypoxic brain damage.
Oh god. I'm genuinely disappointed, and I don't say this for the sake of insulting you. You really, really underestimate how important selection pressure or exponential growth is. Consider humanity. All it takes is a single person with a dream, like Elon Musk, to move forward timelines by decades. VNRs are trivial to the kinds of civilizations we're discussing. Nominal population doesn't matter, especially when we consider robotics or AGI.
Your argument must be true for every civilization.For its entire history till the present. One defector, in one galaxy a million ly away? They'd have eaten the whole thing and sent probes and VNRs our way.
Even a very, very low rate of growth can take over galaxies in what is the barest fraction of the time that has passed since the universe formed, even counting since the earliest plausible eras for life to form - when metallicity was sufficient. We have billions of years to work with.
You demand that every civilization convergently decides to become a hermit. They is really not a good argument.
Either RKVs are dangerous enough that you should expand out in space as quickly as possible to defend yourself against them because people will fire them off indiscriminately, or they aren't actually all that dangerous and so there's no rush to expand. We both seem to agree that firing off RKVs isn't actually all that great of a strategy, so it doesn't make sense to try to be grabby specifically to survive RKVs.
This sufficiently fast RKV will never arrive, because it will hit a piece of interstellar dust and vaporize. If you're worried this won't happen, you can make sure of it pretty trivially as a defensive measure by creating armor belts of small high-density particles, which is going to be considerably easier and cheaper than making an RKV kill chain.
Any RKVs that travel at a more leisurely pace to avoid obliterating itself will likely be detected by any "peer" civilization and intercepted by another RKV of some kind, or a high-energy laser or particle weapon that will ablate it and push it off course.
None of these defenses are technically hard; some of them could be probably be accomplished by civilizations below K1 on the Kardashev scale. (For reference, the interplanetary dust cloud - which is thick enough that dust strikes are routine on spacecraft - has less mass than a relatively unexceptional asteroid).
Why? If you've decided to wait until the end of the universe to crunch numbers then you might as well just wait until then to do everything.
Uhhh, here's what I in fact said:
I think you may have just skipped over my most interesting proposal for an Aestivation civilization. Sad! I thought it was neat.
Sure, and this might have already happened and we just don't happen to know it!
VNRs are considerably more complex and far-fetched than solar-sails, and, just like separatist expeditions into space, an inherently dangerous technology that a smart civilization would think twice before launching.
Not at all, my argument (which I am mostly making for the case of intellectual honesty since I too am skeptical that life elsewhere in the universe is abundant if it exists at all) is that there are a multitude of reasons why there might be aliens in the universe that we have not observed, and thus the inference from not seeing them is not especially strong.
Including, hilariously, that they've already converted most of the galaxy to Dyson swarms and we don't know that because they routinely divert a tiny fraction of their energy into masking their position from any planet with biosignatures. You say it would be pretty trivial to detect those planets via inferential telescopic means at ludicrous ranges and take seriously the idea of a Nicoll-Dyson beam; very well, I find those sorts of megastructures very far-fetched but if you're going to the trouble of making one and have the technical means to do it, you likely also have the technical means to trivially prevent planets you've detected with biosignatures from noticing via selective emissions or laser masking.
"Grabby aliens" is only one path out of thousands for a society to take, and the fact that we have not observed it being taken is not particularly strong evidence that it hasn't happened, let alone that the other thousands of options have not been pursued.
That is a very false dichotomy. RKVs are existentially threatening to a planet-bound civilization in a way they simply aren't to a K1+ one, both because the latter has its own countermeasures and deterrence, and because dispersing across enough volume makes comprehensive eradication prohibitively expensive.
RKVs are also not made equal, any more than a Stinger and an ICBM are interchangeable because they're both missiles. You can go from planet-killer to whatever the limit of your launch infrastructure allows. You can modulate speed, switch from a single projectile to a macron gun, have the projectile intentionally disintegrate, switch to MIRV mode at terminal phase, etc etc. You're also not limited to RKVs or Nicoll-Dyson beams. Ultrarelativistic electron beams are perfectly nasty in their own right.
So yes, they're dangerous enough that you'd want to grow, and a sufficiently advanced civilization can also harden itself. Both can be true.
I don't dispute that more advanced civilizations can substantially harden themselves. That's half my argument. I do dispute that a dust shield is anything close to insurmountable, because, as I mentioned, a macron gun is literally relativistic dust. Seriously. The defenses that make a "durable" interstellar craft viable apply right back: laser sweeps, sacrificial forward drones, extended Whipple shields, etc. Disintegrating an incoming RKV is also not a guaranteed solution; it depends on how far out you intercept and how massive and fast the projectile is. It's worse than trying to blow up an asteroid with a nuke, because the debris cone can do nearly as much damage as the intact projectile.
I know about black holes as propulsion mechanisms and as power plants. My point was that you don't need to make one yourself; you can just co-opt one if it's close enough. If.
The whole content of GAH is that it predicts visible, persistent signatures. "It already happened invisibly" collapses straight back into the masking argument and inherits the same thermodynamic problem, so let me deal with both at once.
I have grave reservations about this being feasible at scale, and you're getting an awful lot for free here. A Dyson swarm has to dump waste heat somewhere. To mask it, you'd need either to redirect that heat away from every potentially-observing system in real time (which fails on light-cone delay alone, since you can't react to observers you don't yet know exist), or to eat leakage that scales with swarm size. At galactic scale that gets prohibitive fast. Selective emission masking also presupposes tracking every civilization in your light-cone with biosignatures, in advance, which is strictly harder than detecting them in the first place.
Project Hephaistos is actually informative here, and you're the one who mentioned it as a technosignature candidate in the first place. The fact that we can flag mid-IR excess candidates around individual M-dwarfs at galactic distances, and that the follow-up work suggests background Hot DOGs explain the contamination rather than masking failures, all of which tells you the detection floor is low. Hiding swarm-scale waste heat isn't a free lunch you can hand-wave. That is a ridiculous amount of engineering effort, for not very good reason. We don't hide the ISS from uncontacted tribes in the Amazon, even though we are actively trying not to contact them.
GAH only needs one civilization, anywhere, in the entire history of the observable universe, to launch them. If 99.9% of species are too cautious or too sensible or too risk-averse, the remaining 0.1% fills the lightcone. That was my "all it takes is one defector" point earlier, and it applies equally hard here. You're implicitly demanding universal restraint without admitting that you are, and "every species coordinates on the same restraint forever" is the part of your argument that I or anyone else familiar with Hanson would strenuously object to.
Pointing out that it's "one path out of thousands" is sloppy reasoning. There are an unbounded number of paths from my bed to the living room. I could climb out the window. I could head out the front door, catch a flight to Singapore, then another to Djibouti, come back in a bus and grab lunch on the way. But what would I actually do? Walk there. It's 10 seconds away.
The strength of GAH is that the absence of the signatures it predicts genuinely is strong evidence, because the assumption set is minimal. All you need is: STL interstellar travel is possible, and at least some civilizations will use available resources over geological timescales. That's it. Non-trivial amounts of time have passed since metallicity was sufficient for life to form. So either nobody is out there, or every single civilization in the lightcone independently converged on some elaborate restraint or hiding strategy.
The speed of light allows for cross-temporal sampling. We know what's happened in our galaxy in the last few tens of thousands of years, and we can see billions of years back. That's a lot of data.
The alternatives all require multiple, often jointly held assumptions about alien psychology, technology, or coordination. Aestivation needs everyone to also forgo currently available resources while they wait. Dark Forest needs a workable hiding strategy plus universal adoption. Fodor's intraterrestrials need every civilization to virtualize and also forgo probes. Masking needs a thermodynamic miracle plus universal adoption plus advance detection of every observer. The fewer joint assumptions, the better the explanation, and "no one is here yet" is just the cheapest fit.
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