We define life as "what occurs on earth" and we expect to find it elsewhere in a universe with infinite dimension, variation and depth. Wolfram's principle of computational equivalence may very well be right, we could see life everywhere and not even know it. Maybe to recognize life we have to be related to it, maybe theres some sort of temporal entanglement going on or something, I don't know. All I do know is that a bug on my shirt doesn't know that I have a face, love my wife, talk to people on the internet, drive a car, look at pictures of mars or even that a planet exists, much less other planets. And we expect to be able to recognize higher intelligence when we see it? It's unrealistic, it's a simplistic mindset that shows a lack of understanding of even what it is this universe is doing here. And I don't claim to know that either, but I do see that theres infinite dimension no matter what resolution you look, everywhere, all the time, happening real time, and if its too big or too small I can't perceive it. Maybe the same is true everywhere for everything that can experience. Maybe observant entities that emerged completely separately are incapable of even perceiving each other.
Well you work with the data and evidence you have and make conclusions based on it. You could start hypothesizing about "higher" intelligence and infinite dimensions all you want but if you have no way to measure or detect those things it's not worth much and well.. your approaching SciFi territory at that point. Starting with simpler methods is not really a choice since there are no other options.
> lack of understanding
"Simplistic" understanding based on primitive evidence is still better than seeing "infinite dimensions" without any data to back it up. It's not obvious that any higher beings (compared to humans) even exist, they might they might not. So maybe we should focus on detecting any signs of any kind of intelligence or life in the first place (after even a bug should be able to tell a human apart from a rock when it bumps into one?).
I find your comment insulting to the people who spend time and resources in the search for life outside our planet.
You make it sound like they're unimaginative dolts.
It's not simplistic, it's simply practical. Either we search for life as we know it, or we don't search at all.
You can pontificate all you want about how incomprehensible extraterrestrial life could be, but where does that get us?
Further, I find that ant/human trope to be cerebral wankery.
Sure, ants can't comprehend what they've encountered, even as they crawl up our leg. But the gap between our intelligence levels is enormous.
I think it's much more likely that humans fall far enough right on the intelligence spectrum that we would be able to spot and recognize other forms of life in the universe, even if they happen to be 100x more intelligent than us.
Even a drunk under a lamp is capable of having a moment of realization that he may want to look in the dark carpark, as he was there earlier. That's within his realm of experience.
But please, tell me how we are to even begin looking for life as we don't know it? What are your suggestions?
This is just redefining life to include something we can’t interact with or even understand, but that defeats the purpose of the definition as understood by the public understanding such research funding.
The goal is to answer: “is there relatable life that has any change of interacting with the human mind somewhere in the nearby speck of our seemingly-infinite universe” this get’s phrased as “is there life out there” in common parlance.
"A star’s light would fade as it was encased in such a “Dyson sphere,” but Dyson noted the constructions could be detected by the mid-infrared glow of their radiated waste heat"
--
In Star Control II [1] the player meets an alien race which admits to having tampered with humanity's DNA to "alter its smell" so that other, hostile civilisations can't "smell" us. Maybe there's someone looking out for us and hid us in a quiet corner :-)
Maybe first thing super civilisation would do is to upgrade their bodies, I'd first thing get rid of 50-100 kg of useless meat, bones and blood, I guess then the entire consciousness, memory, emotional sphere can be fit in something size of a microchip die, next step might be finding a way to base consciousness on something like quarks, that would solve transportation, and each person would need tiniest amount of energy. Then I guess they just gather together and form a star. They normal day in life would be our microsecond. So possibly every star in the universe is already a super advanced civilisation, they just do not care to contact us, who would want to contact someone who is billion times larger, slower and depend on clumsy molecules.
Something like this indeed; imagine us in 1000 years (if we don’t blow ourselves up or something before that); we would have brain up/download, the tinniest and energy efficient chip-equivalent that can run your brain and photorealistic VR.
Even with those simple extrapolations, it’s easy to see that we can stick a few billion ‘humans’ (brains-on-chip) in a solar powered spaceship and just let it hang there for eternity or it could do a journey to somewhere. But what’s the point of a journey as inside this relatively tiny ship, these brains will live in a world (probably a clone of older earth) with a universe around it they can explore.
This seems all rather feasible given time and we would not seem very advanced from the outside; you would hardly be able to detect us at all and yet 100s of billions people live in perpetual paradise (or hell, but again; why would you make it bad if you don’t have to).
Exploration seems like a natural way for civilisation to live, but that's because exploration is needed to expand knowledge and grow more intelligent, we as a civilisation mostly became obsessed with intellect dozens generation ago, if not less, and gathering knowledge and exploring for us seems so important right now. It might be less important if important at all for species who have been intelligent for a long time and gathered orders of magnitude more knowledge than we do.
Related question is do species really need intellect at all and how much. It could be that the main purpose of intellect is to increase chances to survive, but what if civilisation already figured survival, will they even need to stay intelligent? Maybe their goal is to be happier or maybe have billion orgasms per second.
Another more obvious reason to explore the universe is lack of resources, at least Earth was mostly explored to be exploited. If resources are solved, one reason to explore less.
> Exploration seems like a natural way for civilisation to live, but that's because exploration is needed to expand knowledge and grow more intelligent, we as a civilisation mostly became obsessed with intellect dozens generation ago, if not less, and gathering knowledge and exploring for us seems so important right now. It might be less important if important at all for species who have been intelligent for a long time and gathered orders of magnitude more knowledge than we do.
Most of the financial impetus for exploration comes from the promise of access to scare resources. But if you have the technology to traverse the stars then your species is either able to harness unfathomable amounts of energy such that you can bend space-time or you've done some kind of wild genetic engineering/cybernetic enhancements to the point where it's not really bound by the limitations of whatever biology its planetary evolution set it up with.
In both cases, they would have the means to functionally be living in a post-scarcity society. Either their consciousness is stored in some kind of long-term solid-state storage that can survive millennia long trips through space or energy is so cheap and available that it's hard to imagine them needing to keep going and searching to find more stuff. After you've explored and catalogued a hundred planets it's hard to imagine any real impetus to keep going.
Human civilization is already projected to cap out in population at around 11 Billion, and that's driven primarily by cultural and economic factors deriving from technology around access to healthcare, education, and other sources of diversion/entertainment/fulfillment. The idea that an advanced civilization must necessarily keep growing and growing in size doesn't seem to hold up for our own experience on Earth.
Or, of course, if we manage to make infinite energy on earth, we don't even have to shoot anything into space; we can simply stack the earth full with these brainframes and stick it out until the sun starts to fail. Besides we ending humanity too early to get there, I find it hard to believe this will not, inevitably, happen.
>Then I guess they just gather together and form a star.
>So possibly every star in the universe is already a super advanced civilisation, they just do not care to contact us, who would want to contact someone who is billion times larger, slower and depend on clumsy molecules.
The Caleban have their own reasons for contacting organic sentient species. But be really careful about getting involved in any contracts with them.
no need to delete the flesh, just make living backups. Monitor them for "dangerous" thought like we do with LLM. Can run them in various environments, have them interact with "aliens" etc Most interesting would be the amount of variety in isolation, you know, the large mostly empty galaxy with everything impossibly far away. They can check out 1 or 2 planets and some moons to prevent excessive boredom in the later stages, if they are some how late extincting themselves. You get that kind of outliers if you run a lot of trials.
I have read the sci-fi short novel when I was a kid, and that was 80ies. The future earth have found signs of life on some distant planet and the science ship was sent to investigate, they got there but could not find anything on the empty rocky planet, the somewhat detective story leads them to realize the life is on the star of that system, not on the planet, and intelligent creatures are plasma based life forms. Unfortunately I barely remember this story, and cannot remember the name or author, I've read hundreds of sci-fi back then.
I also read some random popular science post about subatomic processes in cells, it gave some examples of which I recall one that fascinated me, it appears that there is a gate in a cell that opens or closes by a single electron to let a water molecule in or out I guess. This ignited my fantasy, what if there are more subatomic stuff going on in out bodies? How far it can go in reality and in fiction? What if our memory is subatomic? Could we build something on subatomic level, a logic gate for example? Can a life form be fully subatomic?
Also there is a galaxy on the Orion's belt, and the Orion is a cat, they briefly and somewhat humorously explored the idea in Men in Black which I watched many times.
There is quantum realm in the Ant-Man series. If it existed I guess super civilisation would try to go there or stay there to be more energy efficient.
There is also dr Manhattan, whose blue body I believe is photons. Imagine he was not the only one in that experiment, and our entire human race followed him, what would our civilisation be? No buildings, no machines, no crops, no transportation, would we even stay on the planet? What we would do freed from servicing our fragile bodies most of our time? I guess we would just gather together, have fun, party, make new life, teach each other endlessly. So maybe that's what stars are, each just have trillion of dr Manhattan offsprings and that's why we cannot see any signs of life cause we're looking for meatballs.
As someone concerned about resource usage on Earth, it seems to me that the absolute last thing a super advanced civilization would do would be the galactic equivalent of strip mining or mountain top removal. I would think a civilization would have to develop more wisdom about how it interacts with and uses the natural world to even reach a stage where it could consume resources in that scale, and by then it would know better.
It's actually quite comforting that we didn't seem to find any "type 3" by this definition. If we did, that would be a civilization with no respect for life beyond its own, and thus, would be one to fear.
The enigma is that if civilization is common, we should see evidence of mass colonization even if only a single "spreader" civilization developed. Among the millions of civilizations out there, are we assuming that none of them were expansionary?
The conclusion: civilization is uncommon OR we are unable to detect civilizations for some reason OR there is something intrinsic about civilization that prohibits the development of "spreaders".
I might go with option that interstellar spreading is just impossible. There might not be ways around physics and sufficient energy budgets might not just be possible.
Or maybe it's just too impractical. Communication alone is a pretty compelling argument against "galactic civilisations". If the speed of light is indeed the ultimate limit for information exchange, then it would be completely pointless to have a "colony" more than a handful of light years away.
It'd be practically impossible to even just have a meaningful information exchange between worlds that are hundreds or even thousands of light years apart. Trading goods would be useless - it'd take thousands of years for a one way trip. Messages would be obsolete the moment they're sent, because the receiver would only be able to detect them after hundreds or thousands of years.
All those fantasies rely on FTL or basically unchanging civilisations that stagnate for aeons.
Also, wouldn't any type of generation ship be culturally resource constrained, maybe not energy, but at least in all meaningful raw materials. As such the initial start might be expansionist, but the spawns would have spend long time with very real limits, likely in all aspects of normal living. And with communication being what it is, they might be extremely unhappy about being sent away too...
If space travel were performed only by robots (and really, why would anyone do it any other way) then large scale “colonization” need not even make sense: the robots could travel around at sunlight speed doing whatever research is of interest to the aliens and gathering whatever resources are needed for people on or near the home planet. “People” might have long enough lifespans that the time taking by the robots to travel around might not feel significant, especially as it would mostly be happing in background.
Strip mining gravitational wells is a dumb thing anyway used for ali n invasion plot devices.
There's probably plenty of resources for even extensive interstellar civilizations in asteroids.
Once you can cart around a solar system pretty easily, it's probably far less resource intensive to mine Asteroids and not have to deal with gravity wells, atmospheres, and chemically reactive environments.
If you dropped in the solar system needing rare earths would you conquer humanity, extract the resources from our metal poor crust, and drag them up to orbit, or park your ship next to that asteroid with sixteen quintillion dollars of rare earths?
Even mercury or a host of moons would be far easier.
And if you had sufficient technology and time, couldn't you well just blow up the planets, wait for sufficient time and comeback to collect resources. Planets are inefficient in mass to surface ratio anyway...
If you can do everything in space, why even bother with planets anymore.
The Kardashev scale is most likely a misconception anyway: the factor representing capability is power density, not total energy.
It is useless to generate huge amounts of power thinly dispersed over galactic scales.
A society capable of high power densities, like direct energy-conversion fusion for starters, can realize fantastic feats, as opposed to somebody collecting sunlight over vast volumes of space, but lacking adequate portable storage.
On the other hand it could also mean that can civilizations never reach that stage and there is still a great and possibly even final filter a head of us.
Or we ourselves are a filter, destroying any form of intelligent life that could do anything different before it can evolve so, before our own self-destruction. Maybe we have already done it and we do not even know it.
Or, civilizations have become so advanced they mastered higher dimensional movement and are now occupying positions in time and space that we cannot see, and no matter where we hide they can always see us without being detected.
Organisms competing with other organisms is what has created intelligent life. I think more of that competition would only lead to even more intelligent life.
At a very large scale, changes like a mountain removal or temperature increase of a few degrees are fully negligible. Even humanity should be able to reverse those if it decided to actually do it.
Will we actually do so? It's not too likely.
It's possible that advanced civilizations actually become more energy efficient over time. I'm thinking about how cities are much more energy efficient per capita than less dense environments.
Most of a galaxy would be lifeless. A super civilization could terraform millions of planets and moons. It could convert other matter into digital simulations.
I think it makes more sense that very advanced aliens would live in VR paradises they created. Anyone who has read Diaspora by Greg Egan knows what I am talking about.
Freshwater, sufficient land devoted to biodiversity and a functional species food web, topsoil erosion, meat production scaling for carbon and necessary feedstock land.
Simply consider the scaling involved if China and India want US style resource conservation per capita.
China in India are roughly 10 times the amount of people as the US.
Daily reminder that supercivilizations likely wouldn't need or even consider the concept of a dyson sphere, but have ways of generating power (from our eyes) out of seemingly thin air
Should still be visible if a super civilization gets to a point where it needs to harness the power equivalent of an entire star (or even far sooner) then even if they don’t do it via a dyson sphere the waste heat alone should still be detectable.
If they can summon enough power to not need or want a galaxy worth of Dyson swarms, then either (1) they are powerful enough to not need or care to hide, or (2) they're hiding because there is something out there that makes a galaxy's worth of Nicoll-Dyson beams seem trivial and insignificant as a weapon.
For reference, a K3 civilisation worth of Nicoll-Dyson beams can gravitationally unbind[0] 10^9 Earthlike planets in just under 26 days.
Unless we’re talking about breaking the laws of physics as we know it completely it think it would be pretty hard to mask the waste heat from a civilization with an energy consumption of a star yet alone multiple stars.
I am confused. If nuclear fission/fusion was perfectly efficient, which it isn't, the energy produced still ends up as heat. The second law. A hundred watts of power, after being used, eventually ends up as heat. It doesn't disappear. This survey was looking for that waste heat.
E=mc^2, all matter is just energy. We only don't know how to release it. Sure you can claim that does not violate laws of thermodynamics, but eradicates concept of Dyson spheres as useless.
Is a Dyson Sphere worth the up-front cost if a civilization has fusion? If not, then maybe that's the answer, even without exotic power generation methods we haven't even imagined yet.
And yes, I understand that fusion is "always 10 years away" even with Helion, but it does seem like it's coming within the next 100 years sometime.
well, on my understanding the output of a fusion power plant is about the same as a fission plant, but possibly cheaper and/or cleaner. that isn't much compared with the energy radiated by a star.
Space is a very large place. But spacetime is doubly so.
On earth it takes a few tents thousands years to have a civilization vanish. Put 1 million and even the most advanced civilization will become unrecognizable dust.
I always liked the idea and think O'Reagan's short is the best take on it.
A black and white version set in Les Deux Magots, Sartre and Beauvoir at a table in the background, would be nice.
It is always possible of course, that most civilizations are not terribly concerned with power, control, possession, expansion ... that they might have completely overcome similar problems of physical existence, become extremely efficient and long-lived, found delightful ways and places to live quiet, harmonious and peaceable lives, and never yearned to amass something visible across the galaxy.
Heck, it's even possible that such civilizations once existed on this planet.
Makes the Fermi paradox even more interesting and the hypothesis of a great filter more likely.
IMHO there's a fair chance we're past such a filter. The origin of life from simple organic matter (abiogenesis) may be extremely unlikely (although most researchers currently working on this say it was probably not that complicated). Or the origin of big, energy rich cell life (eucaryotes) was a very rare event (it did require colossal changes in a very short time frame). Or maybe the origin and survival of intelligence is the hard part.
But i think more likely the filter is ahead of us. Less than a century ago we invented nuclear weapons. Already had a few near misses on a civilization ending nuclear war. More and more countries are acquiring such weapons. And this is provided we got extremely lucky that separating weapon grade isotope of uranium from the naturally occurring ores on Earth surface is very hard. If it was easier for small dictatorships and organizations like Isis to get nukes we'd be probably back to stone age by now. And with the scientific and technological progress going faster than ever, sooner or later we will invent even more powerful weapons, that are easier to produce - which will make the survival of the human race problematic.
Honestly - I feel the filter is ahead of us, too. We have to contend with two major issues right now, that may determine the fate of our planet (and subsequently, the human race): climate change, and nuclear war. And soon, maybe AI? But I feel we are still quite a ways off for that.
Perhaps it's already here. In reference to a different thread about Japan's population decline, it is supposed there that advanced economies lead to population decline (via below replacement birthrates) and require immigration to sustain them. The problem is that those immigrants who choose to remain are that they or their decendents will eventually suffer the same below replacement birthrate. If everywhere becomes an advanced economy, then in theory, everywhere would suffer the same fate, and the great filter has won. But it's just a supposition, right.
This is a relatively easy problem to solve, give families more and more incentives to have kids. Personally I view this as a non-issue. If a population decline reaches a truly severe level, we'll just implement a more comprehensive solution
Yeah, I was gonna say, I think catastrophes are a simpler example. Good chance of that or supervolcano, or any of the above.
There could be that if you bundle together all of these major events that either kill all, or set us back, that it takes more than 5-10 billion years to produce a civilization that can advance far beyond their planet.
The dinosaurs were close to 0.1 billion years ago, and they existed for 0.165 billion years. So repeat 100 tries and your luck runs out. Sorry if there's math or other mistakes.
Of course we haven't had 0.1 billion years of intelligent life, but 0.003 billion... I believe there were more than one extinction event in the 0.165B years of dinosaurs.
Are we stuck in creativity jail? Like that analogy of us waiting for flying cars, but we already have them and they are called planes, they just aren't how we kept picturing them. What are they looking for when they look for Dyson spheres? Just intermittent flashes?
I shared a lab with an instructor at my university who made photovoltaics that absorbed the non visible spectrum but allowed visible light to pass through.
I'm sure these are thought of already but I don't know how/if they are looking for all of these
* Absence of a star (fully engrossed in a Dyson structure)
-- this seems like how a black hole.would be identified by circling bodies around nothing
* A visible star, but it has some part of its em spectrum clipped because it's totally encased by a sphere that only absorbs a portion of the em spectrum
* The Dyson sphere is large enough to encase many galaxies (including us)
* there's Dyson sphere s but they don't rotate so we don't see any sharp change in luminosity
* There's a binary star, but one is a Dyson sphere and appears as a planetary body
The universe is isotropic and homogeneous. You could certainly avoid the nearest neighbor but your beam of heat would hit some other galaxy within a few dozen megaparsecs. Given ships that can survive coasting intergalactic distances at high c that would still put your galaxy under threat with current assumptions about the lifespan of the universe.
It might not be a perfect cloaking device, but if it can reduce visibility to that one galaxy a few dozen megaparsecs away, perhaps it’s enough to evade the survey that the article covers?
The PDF says they used the data from the WISE all-sky infrared survey to find the 100,000 galaxies, of which a "significant population" had a redshift z of over 2. https://arxiv.org/pdf/1504.03418.pdf
Depending on the Hubble constant, a z of 2 is more than 8000 mpc, 27 billion light years. That's a big search volume, and they didn't find anything obviously artificial.
Due to the finite speed of light, for many of those galaxies the images are a snapshot of several billion years ago. So we have no idea of what is thriving there today.
Okay, but that makes it worse. You can spend a million years beaming your waste heat at an apparently-dead galaxy, only to have one of its indigenous species bootstrap up a technological civilization in a blink of an eye (a mere thousand years) and launch an invasion fleet.
If it's the Dark Forest scenario then it's simply not safe to show any technosignatures at all, ruling out megastructures entirely.
I always liked the idea that there's a reason not to be visible; pretty sure I saw it mentioned on HN first, it went something along the lines of us sending out messages and getting one back that says "SHH! They'll hear you."
That's just not possible. Light has been bouncing off biosignatures on Earth for as long as life has existed here. We can't hide those. We also can't hide the spectra bouncing off air pollutants. There's an ever expanding bubble of spectra racing through the galaxy announcing the Industrial Revolution.
Radio emissions are actually much harder to detect because they're weaker than all the light bouncing off the planet. Aliens aren't picking up TV or radio broadcasts. Those become undetectable a little outside the solar system. The signal strength fades (due to the inverse square law) to under natural radio background a little into the Oort Cloud. Only very deliberate high power and highly directional signals can be detectable at interstellar ranges.
The Dark Forest theory is just silly and I'd go so far as to say pseudoscience. It just doesn't make any sense if you think about it for a few minutes.
“If Loud Aliens Explain Human Earliness, Quiet Aliens Are Also Rare” by Robin Hanson, Daniel Martin, Calvin McCarter, and Jonathan Paulson, September 7th, 2021
Is what you want to read if you're interested in the fermi paradox.
Where all this energy from a dyson sphere is supposed to go? Most of the energy we produce finally ends up heating the atmosphere. This doesn't seem to be the case for a supercivilization. The energy may be turned into matter but from efficiency standpoint it is simpler to convert existing matter to whatever you want.
A bunch of smart bipods, who have just discovered electromagnetism and gravity, believe that they know everything there is to know and claim that there is no life in nearby galaxies because their highly precise instruments and highly sophisticated minds see nothing.
Are we looking at the definition of what "success" would be for a civilization? Could civilizations use localized, smaller scale nuclear reactors & highly efficient battery or grid storage?
Obviously, a civilization in need of stellar expansion in order to address population expansion needs would probably be very detectable on sky surveys, but the notion that geometric expansion wouldn't result in extensive stellar colonization because of resource needs seems pretty naive.
One of the interesting concerns about being an interstellar civilization kind of related to the great ant war that I think was documented in a Kurgesstz video about the relentless expanding invasive army ants around the world.
They used to not attack neighboring colonies because they all shared the same smell. At some point one of the species diverged and had as a different smell and now the unopposed growth of the one species now fights in huge battle between their own species that just smell slightly different.
Likewise, if you have a large distance between two stellar colonies. There's going to be a smell evolution over time.
Humans fight a lot of intraspecies wars but not nearly to the extinctive ferocity that a war between two different species results in.
How long before you send individuals to another star do they consider themselves another species?
I mean look at what happened with Hitler and other genocidal actions.
I consider this to be another great argument against the existence of "galactic civilisations". Every colony would necessarily become a the seed for a different civilisation and species in a comparatively short amount of time.
Isolation due to the communication delay (e.g. ~8 years round-trip in case of Earth to Alpha Cen) and the likely need for adaptation to the new world (be that by means of evolution or genetic engineering) would drive both home world and colonies apart quickly.
What else has been ruled out? I remember something about vessels travelling at relativistic speeds having a particular signature that we have not detected either.
The fact of the matter is that we wouldn't even be able to detect radio signals from the closest star Alpha Centauri 4 ly away, so this "ruling out" is pretty much made up - we haven't ruled out anything. The Great Filters, "there is nothing out there", this article, etc all make it seem like we did rule something out, but re-read the first sentence - it really puts into perspective how little we know.
This article predates a decent amount of research into Ultra-Diffuse galaxies: https://en.m.wikipedia.org/wiki/Ultra_diffuse_galaxy. These curiously tend to either have way more or less dark matter than normal. And, dark matter just means matter that’s not visually observable, it doesn’t mean all dark matter is the exact same kind of thing, so it seems reasonable that Dyson spheres could present as dark matter. So I like to think that UDG galaxies are candidates for type2 civilizations or evidence of intergalactic resource extraction/technology that distorts the ratio of regular matter to dark matter, though most likely they’re observational quirks. A full list of justifications for them suggesting advanced civilizations:
UDG galaxies have low levels of interstellar matter. A type 2 civilization would likely prefer to have all matter either generating/capturing energy or to be used for their own pursuits.
UDG galaxies tend to be older. It seems reasonable that type 2 civilizations would be in older galaxies where they had lots of time to develop.
Because of how dark matter works, it seems inexplicable for it to not cluster with regular matter at galactic scales/during the formation of a galaxy. Even weirder is that instead of a normal distribution or spectrum of regular matter to dark matter, almost every galaxy has it at a 1:5 ratio, except UDGs which are either at one extreme (~no dark matter) or another (1:90+ for https://en.m.wikipedia.org/wiki/Dragonfly_44). This disequilibrium, similar to disequilibria on Earth, suggests life. But since this is occurring at galactic scale it suggests a galaxy spanning civilization.
The existence of UDGs at both extremes could be explained by some process (that discriminates between regular and dark matter) by which matter is transferred between galaxies or even converted between the two forms. Whether this happens seems to be yes/no which at galactic scales seems explainable as “has an advanced civilization”. And perhaps in some cases this is due to a galaxy spanning civilization doing some kind of resource extraction from one to another.
Finally, for UDGs with almost all matter being dark, this may represent an almost-complete conversion of the galaxy to a type 2 civilization. As expected, these are very rare because the time to convert a galaxy to this state should be very small compared to the beginning of the transition and end of it.
This whole article rests on the notion that Dyson spheres will eliminate waste energy through black body radiation in a way that’s observable to us, but an advanced culture capable of building these things could likely think of workarounds. I mean, I’m sitting on my couch and I think you could probably figure out a way to direct this in a certain direction that would be invisible from most perspectives. And maybe whatever technology helps manipulate dark matter or convert between regular and dark matter would help you radiate dark matter instead of EM.
While it’s true that not all dark matter has to be exactly the same thing, it’s also true that no large portion of it can be ordinary baryonic matter at low temperatures. What we know about dark matter is that it is weakly interacting, which means that it just doesn’t interact with ordinary matter and ordinary energy. This automatically rules out building a machine made of ordinary matter that creates or manipulates dark matter on any large scale. We might conceivably build a giant machine that _detects_ a particle or two of dark matter every year, but so far all our attempts have failed. Thus dark matter cannot just be a waste product of some advanced civilization, and even if it were you cannot just magic up a way to avoid creating waste heat.
"Strange, why can't we detect any Dyson spheres in this area of space?"
Is the astrological equivalent of:
"Strange, why can't we detect any shambling ghouls in this area of the graveyard?"
Perhaps we should stop wasting time and money confirming that reality does not correspond to our fiction.
I offer my solution to the Drake equation, which can be neatly expressed by the notion of opportunity cost: We don't see Dyson spheres because at every order of scale and complexity there are an almost infinite variety of possible time and resource consuming projects, the overwhelming majority of which will be not be encoded as light emitted from a distant star.
> In some sense it doesn’t matter how a galactic civilization gets or uses its power because the second law of thermodynamics makes energy use hard to hide. They could construct Dyson spheres, they could get power from rotating black holes, they could build giant computer networks in the cold outskirts of galaxies, and all of that would produce waste heat. Wright’s team went right to the peak of the curve for where you’d expect to see any sort of waste heat, and they’re just not seeing anything obvious.
In any case their funding came from The Templeton Foundation and all they did was look at existing imagery.
Either way, I'd rather live in a world where we looked and didn't find anything than one where we didn't bother looking.
The other answer is excellent, but also: waste heat from star-system-scale processes is what we can rule out with existing tech, so that's what we're ruling out.
We define life as "what occurs on earth" and we expect to find it elsewhere in a universe with infinite dimension, variation and depth. Wolfram's principle of computational equivalence may very well be right, we could see life everywhere and not even know it. Maybe to recognize life we have to be related to it, maybe theres some sort of temporal entanglement going on or something, I don't know. All I do know is that a bug on my shirt doesn't know that I have a face, love my wife, talk to people on the internet, drive a car, look at pictures of mars or even that a planet exists, much less other planets. And we expect to be able to recognize higher intelligence when we see it? It's unrealistic, it's a simplistic mindset that shows a lack of understanding of even what it is this universe is doing here. And I don't claim to know that either, but I do see that theres infinite dimension no matter what resolution you look, everywhere, all the time, happening real time, and if its too big or too small I can't perceive it. Maybe the same is true everywhere for everything that can experience. Maybe observant entities that emerged completely separately are incapable of even perceiving each other.