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Alien Supercivilizations Absent from 100k Nearby Galaxies (2015)

50 points by _Microft 3y ago

ggeorgovassilis 3y ago
"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 :-) [1] https://en.wikipedia.org/wiki/Star_Control_II https://en.wikipedia.org/wiki/Star_Control_II
_Microft 3y ago
This was submitted and discussed long ago (simply using the "past" search does not find this one without some additional tweaking of the query): https://news.ycombinator.com/item?id=9398836 https://news.ycombinator.com/item?id=9398836
- lucb1e 3y ago
  2015, for anyone else wondering
fullstackchris 3y ago
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
- dogma1138 3y ago
  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.
  - radicaldreamer 3y ago
    If they could do this, wouldn't they go to as much effort to cloak themselves?
    - ben_w 3y ago
      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. [0] https://youtu.be/7g77WN6obk4 https://youtu.be/7g77WN6obk4
    - dogma1138 3y ago
      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.
- sbierwagen 3y ago
  Tell me more about this power source that is immune to thermodynamics.
  - TheLoafOfBread 3y ago
    Just splitting matter into energy? Why would you ever use a Dyson Sphere, when you can just force decay your trash into pure energy.
    - sbierwagen 3y ago
      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.
      - TheLoafOfBread 3y ago
        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.
- HyperSane 3y ago
  A large black hole would be far superior power source than a dyson sphere.
_Microft 3y ago
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.
- throw1234651234 3y ago
  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.
dbingham 3y ago
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.
- dogma1138 3y ago
  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.
  - freehorse 3y ago
    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.
    - xwdv 3y ago
      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.
    - nverno 3y ago
      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.
- radicaldreamer 3y ago
  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.
jl6 3y ago
How sure are we that a galaxy’s worth of heat can’t be radiated in a single direction, calculated to avoid as many observers as possible?
- sbierwagen 3y ago
  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.
  - jl6 3y ago
    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?
    - sbierwagen 3y ago
      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 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.
      - Qem 3y ago
        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.
        sbierwagen 3y ago
        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.
throw1234651234 3y ago
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.
- AtlasBarfed 3y ago
  The assumption comes down to whether that fusion is cheaper than solar in space. Considering fusion or fission can't beat solar on the planet with solar being hamstrung by our atmosphere...
- zabzonk 3y ago
  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.
czbond 3y ago
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?
diziet 3y ago
Related: https://grabbyaliens.com/ https://grabbyaliens.com/
buggythebug 3y ago
If an Alien civilization has the means to visit us, they are beyond the point of needing more resources. Same reason an Alien spacecraft has never crash landed on Earth - Aliens don't crash the car.
- AtlasBarfed 3y ago
  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.
  - qayxc 3y ago
    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.
- P_I_Staker 3y ago
  Maybe they're drunk.
Woodi 3y ago
Maybe it's time to stop that sentiment and ack that we are the future Ancients ;) Or could be. But prospects are bleak so far...
- deleted 3y ago
  [deleted]
zh3 3y ago
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."
- axiom92 3y ago
  https://en.wikipedia.org/wiki/Dark_forest_hypothesis https://en.wikipedia.org/wiki/Dark_forest_hypothesis Also a major theme of https://www.amazon.com/Dark-Forest-Remembrance-Earths-Past/dp/0765386690 https://www.amazon.com/Dark-Forest-Remembrance-Earths-Past/d...
  - HTTP418 3y ago
    This was exactly what I was going to include. Seriously good book to see potential ramifications of this theory.
- giantrobot 3y ago
  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.
- P_I_Staker 3y ago
  I like a theory I don't hear much talked about. They just don't want to interfere. We don't interfere with un-contacted people for the most part. Could be that ethics and philosophy ends up dictating that you stay out of it. There's speculation that they've sent probes. Could be they have little to gain from contact, and prefer to leave us to our own devices. After all, it is the right thing to do.
notorandit 3y ago
> Where is everybody? When was everybody? 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.
borissk 3y ago
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.
- deafpolygon 3y ago
  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.
  - wlpu 3y ago
    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.
    - 3y ago
nmca 3y ago
“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.
garrisonj 3y ago
I always feel like these discussions are built upon extrapolating on assumptions based on speculation. How could we, a species that hasn’t progressed that far, know what advanced civilizations look like?
- deleted 3y ago
  [deleted]
contingencies 3y ago
Almost as if someone vacuumed them up.
exebook 3y ago
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.
- qwertyuiop_ 3y ago
  This is an incredible thought experiment. Is there any fictional basis for your thoughts ? I would love to explore fictional material in this area.
  - spacetime_cmplx 3y ago
    Yes, it's called Psilocybin
  - exebook 3y ago
    Are you an author? 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.
deleted 3y ago
[deleted]
8bitsrule 3y ago
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.
friend_and_foe 3y ago
It's such a simplistic mindset. 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.
- Maursault 3y ago
  > in a universe with infinite dimension, variation and depth. Poetic license? Not only are there not infinite dimensions, none of the three or four dimensions we know about are infinite.
- qwytw 3y ago
  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?).
- 3y ago
opportune 3y ago
This article predates a decent amount of research into Ultra-Diffuse galaxies: https://en.m.wikipedia.org/wiki/Ultra_diffuse_galaxy 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 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.
shashurup 3y ago
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.
Borrible 3y ago
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. https://www.mit.edu/people/dpolicar/writing/prose/text/thinkingMeat.html https://www.mit.edu/people/dpolicar/writing/prose/text/think... https://www.youtube.com/watch?v=T6JFTmQCFHg https://www.youtube.com/watch?v=T6JFTmQCFHg
HlessClaudesman 3y ago
"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.
- JustBreath 3y ago
  There's a rebuke to this argument in the article: > 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.
- matthewdgreen 3y ago
  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.
girafffe_i 3y ago
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
akomtu 3y ago
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.

50 points by _Microft 3y ago

"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 :-) [1] https://en.wikipedia.org/wiki/Star_Control_II https://en.wikipedia.org/wiki/Star_Control_II

_Microft 3y ago

This was submitted and discussed long ago (simply using the "past" search does not find this one without some additional tweaking of the query): https://news.ycombinator.com/item?id=9398836 https://news.ycombinator.com/item?id=9398836

lucb1e 3y ago
2015, for anyone else wondering

fullstackchris 3y ago

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

dogma1138 3y ago
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.
- radicaldreamer 3y ago
  If they could do this, wouldn't they go to as much effort to cloak themselves?
  - ben_w 3y ago
    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. [0] https://youtu.be/7g77WN6obk4 https://youtu.be/7g77WN6obk4
  - dogma1138 3y ago
    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.
sbierwagen 3y ago
Tell me more about this power source that is immune to thermodynamics.
- TheLoafOfBread 3y ago
  Just splitting matter into energy? Why would you ever use a Dyson Sphere, when you can just force decay your trash into pure energy.
  - sbierwagen 3y ago
    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.
    - TheLoafOfBread 3y ago
      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.
HyperSane 3y ago
A large black hole would be far superior power source than a dyson sphere.

_Microft 3y ago

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.

throw1234651234 3y ago
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.

dbingham 3y ago

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.

dogma1138 3y ago
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.
- freehorse 3y ago
  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.
  - xwdv 3y ago
    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.
  - nverno 3y ago
    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.
radicaldreamer 3y ago
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.

jl6 3y ago

How sure are we that a galaxy’s worth of heat can’t be radiated in a single direction, calculated to avoid as many observers as possible?

sbierwagen 3y ago
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.
- jl6 3y ago
  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?
  - sbierwagen 3y ago
    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 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.
    - Qem 3y ago
      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.
      - sbierwagen 3y ago
        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.

throw1234651234 3y ago

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.

AtlasBarfed 3y ago
The assumption comes down to whether that fusion is cheaper than solar in space. Considering fusion or fission can't beat solar on the planet with solar being hamstrung by our atmosphere...
zabzonk 3y ago
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.

czbond 3y ago

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?

diziet 3y ago

Related: https://grabbyaliens.com/ https://grabbyaliens.com/

buggythebug 3y ago

If an Alien civilization has the means to visit us, they are beyond the point of needing more resources. Same reason an Alien spacecraft has never crash landed on Earth - Aliens don't crash the car.

AtlasBarfed 3y ago
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.
- qayxc 3y ago
  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.
P_I_Staker 3y ago
Maybe they're drunk.

Woodi 3y ago

Maybe it's time to stop that sentiment and ack that we are the future Ancients ;) Or could be. But prospects are bleak so far...

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zh3 3y ago

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."

axiom92 3y ago
https://en.wikipedia.org/wiki/Dark_forest_hypothesis https://en.wikipedia.org/wiki/Dark_forest_hypothesis Also a major theme of https://www.amazon.com/Dark-Forest-Remembrance-Earths-Past/dp/0765386690 https://www.amazon.com/Dark-Forest-Remembrance-Earths-Past/d...
- HTTP418 3y ago
  This was exactly what I was going to include. Seriously good book to see potential ramifications of this theory.
giantrobot 3y ago
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.
P_I_Staker 3y ago
I like a theory I don't hear much talked about. They just don't want to interfere. We don't interfere with un-contacted people for the most part. Could be that ethics and philosophy ends up dictating that you stay out of it. There's speculation that they've sent probes. Could be they have little to gain from contact, and prefer to leave us to our own devices. After all, it is the right thing to do.

notorandit 3y ago

> Where is everybody? When was everybody? 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.

borissk 3y ago

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.

deafpolygon 3y ago
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.
- wlpu 3y ago
  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.
  - 3y ago

nmca 3y ago

“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.

garrisonj 3y ago

I always feel like these discussions are built upon extrapolating on assumptions based on speculation. How could we, a species that hasn’t progressed that far, know what advanced civilizations look like?

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contingencies 3y ago

Almost as if someone vacuumed them up.

exebook 3y ago

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.

qwertyuiop_ 3y ago
This is an incredible thought experiment. Is there any fictional basis for your thoughts ? I would love to explore fictional material in this area.
- spacetime_cmplx 3y ago
  Yes, it's called Psilocybin
- exebook 3y ago
  Are you an author? 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.

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8bitsrule 3y ago

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.

friend_and_foe 3y ago

It's such a simplistic mindset. 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.

Maursault 3y ago
> in a universe with infinite dimension, variation and depth. Poetic license? Not only are there not infinite dimensions, none of the three or four dimensions we know about are infinite.
qwytw 3y ago
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?).
3y ago

opportune 3y ago

This article predates a decent amount of research into Ultra-Diffuse galaxies: https://en.m.wikipedia.org/wiki/Ultra_diffuse_galaxy 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 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.

shashurup 3y ago

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.

Borrible 3y ago

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. https://www.mit.edu/people/dpolicar/writing/prose/text/thinkingMeat.html https://www.mit.edu/people/dpolicar/writing/prose/text/think... https://www.youtube.com/watch?v=T6JFTmQCFHg https://www.youtube.com/watch?v=T6JFTmQCFHg

HlessClaudesman 3y ago

"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.

JustBreath 3y ago
There's a rebuke to this argument in the article: > 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.
matthewdgreen 3y ago
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.

girafffe_i 3y ago

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

akomtu 3y ago

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.