11 ms·

Grabby Aliens (2021)

92 points by noch 3y ago

simne 3y ago
I know two things. 1. We are now already using heat mask measures, even when we are very young civ in terms of Kardashev scale. We already use simple slit heat emitters in military tech (many Stealth planes have slit nozzles and for example, Leopard tanks also use slit exhaust for same reason). 2. Even we now know about possibility of laser heat, which could emit heat directly with very high focus. In conclusion, idea is, to surround whole civ with heat mask blanket, and make all heat exhausts directly focused on directions, where no observer expected. BTW this could be evidence of mature Civilization, when see strange space objects, which looks like Black Hole in most directions and extremely bright in some "featured" directions. Second, looks like our development now is very slow, because it should be on early stages (Kardashev scale), and old civ's should know this. And I now support theory, that we are fortunate to be far enough, so stronger civ's are not interested in spending resources to limit our development. I even consider might be exists some preservation pact between old Big civ's, to avoid touch young civ's, for some purposes like scientific, or arts. So yes, basically, I support Zoo theory.
- simne 3y ago
  And I also must add, interesting fact - I have not seen any idea, to explore void in works of our, terrestrial scientists. But for SETI it could be golden earth - if really waste heat emitting there, should be very different view (vs view from near some star). What if this is part of Drake equation which we missed?
fouc 3y ago
What I found most interesting about this model was the implication that humans are possibly one of the earliest sentient spacefaring species to have appeared so far. Which explains why we haven't seen any other signs of extraterrestrial intelligence yet.
- delichon 3y ago
  Expecting ourselves to be special has a poor track record. The same evidence is compatible with lots of loud aliens yelling on channels we can't hear yet.
  - distortionfield 3y ago
    That’s the exact opposite of the grabby alien’s hypothesis tho. The grabby aliens hypothesis says that we’re very much average but that life as a whole is still quite young in the universe.
    - deleted 3y ago
      [deleted]
    - delichon 3y ago
      The galaxy is around 100k light years across and 13 billion years old. For us to be among the first generation born within 10^5 years of each other after a gestation of 10^10 years, would make us special. Being among the first civilizations in the galaxy is less special than being the first civilization, but more special than being just another in an ongoing ecosystem.
      - tshaddox 3y ago
        Why is being first, or being among the first, “special”? To me “special” is different than just “specific.” If some civilization knew it was the 50th advanced civilization in the universe, 50 might seem like a very special number, but is it really more special than 1?
        deleted 3y ago
        [deleted]
      - Veserv 3y ago
        The hypothesis goes: I want humans to be casually interstellar and expand across the galaxy. I want this to occur in less than N years, N << 10^10. If humans are casually interstellar and expansionist, then we would colonize the galaxy in M years, M << 10^10. Humans are not special, therefore if another alien species existed in the past at current human tech levels, then they would do the same as humans would and colonize the galaxy within N + M << 10^10 years after achieving current human tech level. We believe we can detect such a civilization. Therefore, if we are more than N + M years after a another civilization with current human tech level, then we would see them. We do not detect any such civilizations. Therefore one of the assumptions must be wrong. 1. We can not detect a galactic civilization. 2. No alien civilization has reached current human tech level within N + M years of now. 3. Humans are special. Only humans would colonize the galaxy if they had casual interstellar travel. 4. Humans are not special, but we will never invent casual interstellar travel/spread to the stars. So, if you think humans are not special (3 is false) and you hope humans will spread to the stars in the future (hope 4 is false), then you hope the answer is 1 (humans are bad at detection) or 2 (humans are early). If you rule out 1 and 2, then 4 can only be true if 3 is true. If you rule out 3 as well, then you must conclude humanity will never spread to the stars for unknown reasons.
Arch485 3y ago
I might be missing something here, but why would alien (or any) civilizations continually expand at a constant rate? While I'm not an expert, it appears that by observing life on Earth (not just humans), groups of living things do not expand linearly, and eventually hit an upper limit (this happens at all scales, from colonies of bacteria to entire civilizations). Who's to say that other "loud" aliens haven't already expanded and begun spacefaring, but simply are not expanding out to where we are?
- LoganDark 3y ago
  Based on human history, wouldn't the rate of technological growth eventually start to skyrocket during/after some revolution? And with better technology comes better/more expansion.
  - Ancapistani 3y ago
    So far, it seems like the Industrial Revolution was the key accelerating factor for our civilization. Conditions for it were right (or very close) at the height of the Roman Empire. They were probably pretty close at the height of Chinese power, and the Islamic world before the Khans. …but we’re still a young civilization, and are extrapolating from very little data. It could be that we’ve yet to encounter most of those inflection points. Maybe the next one is “the Singularity” - but beyond that we really have no idea. All of this is consistent with humanity being very early on the timeline of the universe.
    - LoganDark 3y ago
      What I know is that technological progress was very slow, until suddenly there was a breakthrough and it rapidly accelerated. Now, we have enough of the fundamentals down that new technological breakthroughs are happening extremely rapidly. What a time to be alive, of course, but what suggests alien civilizations wouldn't follow the same trend of rapid acceleration rather than constant growth?
- geor9e 3y ago
  Constants are the simplest assumption. It's a "first round" of modeling that lets you start having philosophical thoughts on the implications. You can always increase the complexity of the model after. If you don't hold some parameters constant, the model quickly becomes too complex to be of much use for philosophical questions. In reality, a civilization can expand with exponential acceleration, deceleration, or shrink. I didn't even think this the worst of the assumptions. The fact that expansion stops as soon as a civilization meets another seems silly too. As we know, civilizations love nothing more than respecting borders and not conquering each other. But again, it can go either way, so they chose the middle assumption.
pfdietz 3y ago
> Advanced aliens really are out there Stopped reading right there.
- behringer 3y ago
  You're missing out then. That's the assumption being made in the paper and they take it as far as they can while sticking to some semblance of reality. Very interesting ideas in here.
GavinB 3y ago
This is a compelling theory, especially the implication that humans are early. I do wonder whether we should see the evidence of spheres of growing alien influence out in the stars, but instead we see a highly uniform universe in all directions. This would indicate a few possibilities: 1. Expanding alien civilizations are relatively low impact and don't collect all of the energy of stars in ways that are visible to our current telescopes. 2. We are a very early civilization, civs are fairly rare, and we're relatively alone in the parts of the universe that we can see. Civs that are expanding in a grabby fashion started less recently in years than their distance in light years. 3. Aliens expand at close to the speed of light, so there are a lot out there but we won't see them until they're almost here. 4. Something that we have already noticed is actually evidence of grabby aliens, but it is happening in every direction so we assume that it is a natural phenomenon, because it is so uniform. At the very least, it seems likely that we either we are alone in the galaxy, or expansion is very slow. The idea of "expanding in a bubble of influence close to the speed of light" seems implausible to me, just because of the vast amounts of energy required to accelerate and decelerate to relativistic speeds, not to mention protecting the cargo in transit--when you're flying at .9c, almost every other piece of matter in the universe is flying towards you at you at .9c. Accelerating tiny nanomachine von Neumann probes might be a solution, but how would they decelerate enough to not be destroyed on arrival? It's all fascinating to think about, at least.
- JPLeRouzic 3y ago
  > 4. Something that we have already noticed is actually evidence of grabby aliens, but it is happening in every direction so we assume that it is a natural phenomenon, because it is so uniform * Brown dwarfs: These are objects with masses too small to ignite nuclear fusion in their cores and shine like stars. However, they are still warm enough to emit infrared radiation. * There are rogue planet candidates that do not belong to a solar system.
- idiotsecant 3y ago
  5. Grabby aliens do not exist because the universe is a dark forest and any detectable signs of life result in anonymous relativistic snowflake bombardment.
- 3y ago
gmuslera 3y ago
It feels like talking about religion. In a lot of them at the very least, there is an almighty, omniscient god, the alpha, the everyday, and the omega god, the one that maximizes knowledge, intelligence, power, whatever. And people following that religion know exactly how that entity thinks and behave. Because that entity should think like humans of the current culture does, no? With aliens, with a different culture, civilization if that concept applies, language or not, and enough technology to make interstellar travel, and all of that for thousands to millions of years, those aliens that are far beyond our imagination, well, somewhat we know how they think and should behave, now knowing the technology they should have, the knowledge about the universe they should have, philosophy or whatever. We don't even know if it will be ever practical interstellar travel, because we didn't reach that stage yet. In theory it should work... in theory I could climb stairs till reaching the moon too. People is too busy trying to figure out how advanced aliens should think, and didn't stopped to analyze how they are thinking.
- kiba 3y ago
  We don't even know if it will be ever practical interstellar travel, because we didn't reach that stage yet. In theory it should work... in theory I could climb stairs till reaching the moon too. People is too busy trying to figure out how advanced aliens should think, and didn't stopped to analyze how they are thinking By using our knowledge of physics, we can make reasonable speculation on what is possible and not possible, and what engineering we need to do to make these effort successful. Some people's work are so successful that they became foundational to our knowledge base today. Same as with aliens. We can make reasonable extrapolation on what we might see from the type of aliens that expand versus and aliens that don't. They are of course, guesses, and those guesses continued to be argued and refined. Note that the site doesn't assumed that all aliens are grabby, only that some are grabby aliens, and try to extrapolate on what it might look like if they are grabby.
  - pavel_lishin 3y ago
    > By using our knowledge of physics, we can make reasonable speculation on what is possible and not possible, and what engineering we need to do to make these effort successful Our speculation is only as good as our understanding of physics. Which is pretty good! But people in 1800s thought they had discovered just about everything to be discovered, and thought themselves at the end of physics, too.
Donaldobob 3y ago
[flagged]
pavel_lishin 3y ago
> that early deadline explains human earliness. I don't buy these statistical arguments. If only one sentient species is born before 20 billion years have passed since the big bang, and ten million sentient species are born after that time, yes - statistically, you're more likely to be one of the later species. But that early worm species still exists, and experiences its existence. If they thought to themselves, "obviously there's others out there, it's statistically certain!", then they are wrong.
- behringer 3y ago
  20 billion is a long time, and the universe is very big. And we're not the first galaxy to form within that 20 billion year time frame. It's very likely we're not the first in the universe and it's also likely we're not alone in coming to sentience at this very moment in the universes life.
  - MrScruff 3y ago
    What I don't understand is how we reasonably quantify the probability of sentient life evolving. Sure the universe is very big, but the probability could be very small. All the discussions I've seen make the assumption that there's nothing unusual about life on Earth and given similar conditions elsewhere we would expect to see life, but how does one conclude that from a sample size of 1?
    - qnleigh 3y ago
      I guess the argument is something like 'if life is unlikely to evolve, then it is surprising to find ourselves existing so early in the history of the universe. If life is likely to evolve, then how do we explain being apparently alone?' and then the grabby aliens theory tries to answer the second question. I don't find the argument convincing though (per my other comment)
      - pfdietz 3y ago
        But we are not "so early" in the history of the universe. Something like 95% of all the stars that will ever be formed have already been formed. It's actually rather late in the day.
eightysixfour 3y ago
> While the current date is 13.8 billion years after the Big Bang, the average star will last over five trillion years. That does not seem right. Isn't the lifespan of a star between 100m and 100b years or so?
- eschaton 3y ago
  I think it depends on what you mean by “last,” a star might “last” even longer than 5×10^12 years before the last component nucleons of its remnant evaporate. If you consider how long a star lasts to be how long it emits around the same amount of energy until becoming another class of object the time will be shorter. Sol will grow large and red in another 4×10^9 years or so, then after that phase it’ll leave a stellar remnant like a brown dwarf or neutron star, which will last another period of time. How long did Sol last?
  - brazzy 3y ago
    No, it doesn't depend on any such interpretation. The key word is "average". A majority of stars are red dwarves, and those do in fact last for trillions of years without significant change.
dang 3y ago
Related: Grabby Aliens: A Resolution to the Fermi Paradox - https://news.ycombinator.com/item?id=33402628 https://news.ycombinator.com/item?id=33402628 - Oct 2022 (334 comments) Grabby Aliens - https://news.ycombinator.com/item?id=26502232 https://news.ycombinator.com/item?id=26502232 - March 2021 (176 comments) A Simple Model of Grabby Aliens - https://news.ycombinator.com/item?id=26045731 https://news.ycombinator.com/item?id=26045731 - Feb 2021 (80 comments)
ck2 3y ago
the fantastic PBS Space Time on the subject https://www.youtube.com/watch?v=uTrFAY3LUNw https://www.youtube.com/watch?v=uTrFAY3LUNw
mapmeld 3y ago
My go-to counterargument for this is that galaxies are really far apart (from us to Andromeda is 25x the diameter of the Milky Way). If you haven't developed FTL travel, it's a long haul with very little benefit on the way.
- a_wild_dandan 3y ago
  Your "counterargument" is a presumption in Fermi paradox models. The alternative isn't particular interesting.
Animats 3y ago
Actual article: [1] "We estimate that loud alien civilizations now control 40%–50% of universe volume, each will later control ∼ 10^5 to 3 × 10^7 galaxies, and we could meet them in ∼200 Myr–2 Gyr." Those numbers seem inconsistent. "Ours is a model of grabby aliens, who by definition (a) expand the volumes they control at a common speed, (b) clearly change the look of their volumes (relative to uncontrolled volumes), (c) are born according to a power law in time except not within other GC volumes, and (d) do not die unless displaced by other GCs." That's an interesting set of assumptions. Kind of a 1960s science fiction model. If we now have a reasonable understanding of physics, you get a different model. No FTL, radio works at light speed, Technological civilizations may not last all that long. Human civilization is about 6,000 years old. Heavy industrial civilization is about 200 years old. Most mineral resources already are past the point where the easy stuff has been mined. The USGS tracks total worldwide mineral resources.[2] On a scale of years, things look good. On a scale of centuries, not good. On a scale of millennia... [1] https://iopscience.iop.org/article/10.3847/1538-4357/ac2369/pdf https://iopscience.iop.org/article/10.3847/1538-4357/ac2369/... [2] https://www.usgs.gov/publications/mineral-commodity-summaries-2024 https://www.usgs.gov/publications/mineral-commodity-summarie...
- cryptonector 3y ago
  The speed of light is a tremendous limitation. W/o FTL there's no such thing as "loud alien civilizations" that can "control 40%-50% of [the] universe['s] volume".
  - XorNot 3y ago
    Rather depends on other factors though: you can perfectly well run an interstellar empire with very long communication times and people going into suspended animation for transit. Control strategy simply has to adapt accordingly: i.e. a message probably comes with a fleet sufficient to ensure its obeyed. This was one of the ideas in the Doom novelizations: that the aliens had spent so long travelling that there was little chance of victory because of you attacked a place you took along everything needed for overwhelming victory.
brazzy 3y ago
This kind of thing always has the same weakness: it's extrapolating from a sample size of one. It of course tries to account for that by adding large error margins based on what we know, but for some of them it's pure guesswork that could easily wrong.
qnleigh 3y ago
I'm confused by the argument here; is the argument that 'humanity could not arise once the universe has been taken over by grabby aliens, so a possible explanation of finding ourselves existing so early in the history of the universe is that this will be the only opportunity'? But if the universe will soon be filled with gajillions of grabby aliens, who's to say that we couldn't have been born as grabby aliens instead of humans? In fact if there will be so many of them, isn't the fact that we're not grabby aliens ourselves evidence that there will be no grabby aliens? I feel like there is some implicit assumption about 'who you are likely to be born as' that I'm not getting here. Do I need to assume that I could only have been born as a human for the argument to go through?
- ben_w 3y ago
  It's saying there's a good chance we'll be one of the grabby civilisations. Or at least, it doesn't rule it out. Non-grabby aliens aren't visible in this model; given the distances, "grabby" is the only way to change the environment enough for current human tech to even notice something unusual.
  - qnleigh 3y ago
    But if we'll become a grabby civilization, then there will presumably be at least trillions of humans born in the distant future who will live all throughout the universe. Isn't it that an extraordinary coincidence to find oneself born among the first few billion? Incidentally, Carl Sagan used the above line of reasoning as a sign that human civilization was going to collapse before a few more doubling times.
    - ben_w 3y ago
      > Isn't it that an extraordinary coincidence to find oneself born among the first few billion? The weakness of the mediocrity principle is we're in a lot of categories, and we can't be near the middle of all of them at the same time. This paper makes one particular assumption about what's a good set of things to be mediocre about; I think that's the weakest part because it's so easy for intuition to mislead there. So I could invert your surprise: No more so than finding yourself in the last of a few trillion things that evolved into humans.
Towaway69 3y ago
My thinking is that the universe is full with life and communicating life. However communication is only possible with the right technology. What is that technology? Technology that can only be created by a harmonious society working together to share ideas and combine ideas from everyone in a non competitive manner. In that way the universe ensures peace and harmony ensures knowing that warring civilisation aren't able to leave their home base nor communicate with the universe. It might sound slightly esoteric and spiritual but there many ways to societally live together in harmony with all humans. After all not one individual can completely understand the universe, how can one nation hope to reach out to a non understandable universe.
- 8jef 3y ago
  The idea of global harmonious cooperation represent the main evolutionary threshold appearing before us all. This should be our future, if We all individually find enough trust in ourselves, and let us collectively evolve in such direction. And as We, I do not foresee only human beings, but more broadly the Living, as We, interspecies from Earth. Finding a way to unite individualities should include ways to establish communication channels with so-called wildlife individuals. The idea of considering such a path being esoteric is a way to get distrustful people on board, which may be a waste of time and resources. We should focus on uniting everyone who already think this is the new normal.
  - Towaway69 3y ago
    Well said and thank you for saying it. And yes, we should start at home and begin communicating with our surroundings. Be it the planet or the species with whom we share this spaceship earth.
- yreg 3y ago
  How can a particular technology have a non-competitive harmonious society as a hard requirement for it's discovery?
  - Towaway69 3y ago
not_the_fda 3y ago
I think there is a great filter. The trait that makes a species grabby is also the trait that leads to its downfall. They end up destroying their home ecosystem before they can achieve inter-solarsystem travel, wiping themselves out.
bonzaidrinkingb 3y ago
This theory is itself grabby, and grabs itself at that. > Furthermore, we should believe that loud aliens exist, as that’s our most robust explanation for why humans have appeared so early in the history of the universe. But if loud aliens will soon fill the universe, and prevent new advanced life from appearing, that early deadline explains human earliness. Even furthermore, we should believe that Big Foot Medusas exist, as that's our most robust explanation for why humans have not seen these yet and are still alive. Since Big Foot Medusas turn everything alive into stone upon observation, and we are still here, it suggests we are early in our explorations and observations of Big Foot Medusas. Anyway, a loud grabby alien civilization expanding is "first come, first serve". Perhaps we have not seen grabby aliens, because the first grabby aliens became quiet, and make new grabby aliens impossible, or they finally became superrational and realized they need more than one civilizations to have an economy, cooperation, cosmodiversity, or competition: If aim is to win at tennis, you can't play tennis alone. As for earth specifically, it was probably already grabbed, and humans are the terraforming organisms put in service of the grabbies to make our planet habitable. Or the grabbies are in such a zeal to expand and get the most of our galaxy that they focus on planets that are close to the horizon, after which they will be moving away at faster than light speeds due to accelerating expansion of the universe. Only after that will they get around to Earth (first building a Dyson Sphere around the universe to harness its energy).
- Veserv 3y ago
  Of course it makes no sense if you are answering the wrong question. The question being asked is not: "Why do we not see grabby aliens?" The question being asked is: "Under what circumstances can humanity become grabby aliens that colonize the galaxy in reasonable time given that we do not see grabby aliens?" The simplest circumstances that would allow humanity to become grabby aliens in the future is that becoming grabby aliens is easy for a modern human-like society. However, grabby aliens that colonize the universe in reasonable time preclude humanity from existing if we intersect with their existence. That means there must either be something else special about our existence, or that we are unlikely to ever become grabby aliens. That is the entire point of the thought exercise, figuring out if there is a hope that humanity will become grabby aliens (Star Trek).
gcanyon 3y ago
In case anyone is interested in how grabby aliens (or we!) could travel the galaxy, Kurzgesagt has an excellent video on building a stellar engine to move our solar system at up to 50 light years per million years. Setting aside considerations of whether we'll survive the next few decades as a technological civilization, let alone the next few millions of years, the Caplan engine would let us colonize a significant fraction of the galaxy within a billion years or so. https://www.youtube.com/watch?v=v3y8AIEX_dU https://www.youtube.com/watch?v=v3y8AIEX_dU
jojohohanon 3y ago
Why are we now? https://www.ox.ac.uk/news/science-blog/why-are-we-now https://www.ox.ac.uk/news/science-blog/why-are-we-now It’s early here, but it think the gist of it is using Bayes to quantify: Given that the universe would seem to get more hospitable at older ages, why are we alive now? IIUC the most likely explanation is some secondary force (aliens) to modify the future hospitality.
- deleted 3y ago
  [deleted]
flenserboy 3y ago
Ecosystems on Earth might be a better way of thinking about this. Notice how we do not see one organism or type of organism squeeze out all the others, or work to take in all energy available to them; this is also true of human settlements, whether rural or urban. There is a clear diversity of energy extraction methods, & singular dominance (think algae-clogged lakes) tends to lead to stagnation & death. Mechanical expansion might look grabby (as in Von Neumann probes), but life expanding through the universe could instead follow biological & human-settlement patterns.

92 points by noch 3y ago

I know two things. 1. We are now already using heat mask measures, even when we are very young civ in terms of Kardashev scale. We already use simple slit heat emitters in military tech (many Stealth planes have slit nozzles and for example, Leopard tanks also use slit exhaust for same reason). 2. Even we now know about possibility of laser heat, which could emit heat directly with very high focus. In conclusion, idea is, to surround whole civ with heat mask blanket, and make all heat exhausts directly focused on directions, where no observer expected. BTW this could be evidence of mature Civilization, when see strange space objects, which looks like Black Hole in most directions and extremely bright in some "featured" directions. Second, looks like our development now is very slow, because it should be on early stages (Kardashev scale), and old civ's should know this. And I now support theory, that we are fortunate to be far enough, so stronger civ's are not interested in spending resources to limit our development. I even consider might be exists some preservation pact between old Big civ's, to avoid touch young civ's, for some purposes like scientific, or arts. So yes, basically, I support Zoo theory.

simne 3y ago
And I also must add, interesting fact - I have not seen any idea, to explore void in works of our, terrestrial scientists. But for SETI it could be golden earth - if really waste heat emitting there, should be very different view (vs view from near some star). What if this is part of Drake equation which we missed?

fouc 3y ago

What I found most interesting about this model was the implication that humans are possibly one of the earliest sentient spacefaring species to have appeared so far. Which explains why we haven't seen any other signs of extraterrestrial intelligence yet.

delichon 3y ago
Expecting ourselves to be special has a poor track record. The same evidence is compatible with lots of loud aliens yelling on channels we can't hear yet.
- distortionfield 3y ago
  That’s the exact opposite of the grabby alien’s hypothesis tho. The grabby aliens hypothesis says that we’re very much average but that life as a whole is still quite young in the universe.
  - deleted 3y ago
    [deleted]
  - delichon 3y ago
    The galaxy is around 100k light years across and 13 billion years old. For us to be among the first generation born within 10^5 years of each other after a gestation of 10^10 years, would make us special. Being among the first civilizations in the galaxy is less special than being the first civilization, but more special than being just another in an ongoing ecosystem.
    - tshaddox 3y ago
      Why is being first, or being among the first, “special”? To me “special” is different than just “specific.” If some civilization knew it was the 50th advanced civilization in the universe, 50 might seem like a very special number, but is it really more special than 1?
      - deleted 3y ago
        [deleted]
    - Veserv 3y ago
      The hypothesis goes: I want humans to be casually interstellar and expand across the galaxy. I want this to occur in less than N years, N << 10^10. If humans are casually interstellar and expansionist, then we would colonize the galaxy in M years, M << 10^10. Humans are not special, therefore if another alien species existed in the past at current human tech levels, then they would do the same as humans would and colonize the galaxy within N + M << 10^10 years after achieving current human tech level. We believe we can detect such a civilization. Therefore, if we are more than N + M years after a another civilization with current human tech level, then we would see them. We do not detect any such civilizations. Therefore one of the assumptions must be wrong. 1. We can not detect a galactic civilization. 2. No alien civilization has reached current human tech level within N + M years of now. 3. Humans are special. Only humans would colonize the galaxy if they had casual interstellar travel. 4. Humans are not special, but we will never invent casual interstellar travel/spread to the stars. So, if you think humans are not special (3 is false) and you hope humans will spread to the stars in the future (hope 4 is false), then you hope the answer is 1 (humans are bad at detection) or 2 (humans are early). If you rule out 1 and 2, then 4 can only be true if 3 is true. If you rule out 3 as well, then you must conclude humanity will never spread to the stars for unknown reasons.

Arch485 3y ago

I might be missing something here, but why would alien (or any) civilizations continually expand at a constant rate? While I'm not an expert, it appears that by observing life on Earth (not just humans), groups of living things do not expand linearly, and eventually hit an upper limit (this happens at all scales, from colonies of bacteria to entire civilizations). Who's to say that other "loud" aliens haven't already expanded and begun spacefaring, but simply are not expanding out to where we are?

LoganDark 3y ago
Based on human history, wouldn't the rate of technological growth eventually start to skyrocket during/after some revolution? And with better technology comes better/more expansion.
- Ancapistani 3y ago
  So far, it seems like the Industrial Revolution was the key accelerating factor for our civilization. Conditions for it were right (or very close) at the height of the Roman Empire. They were probably pretty close at the height of Chinese power, and the Islamic world before the Khans. …but we’re still a young civilization, and are extrapolating from very little data. It could be that we’ve yet to encounter most of those inflection points. Maybe the next one is “the Singularity” - but beyond that we really have no idea. All of this is consistent with humanity being very early on the timeline of the universe.
  - LoganDark 3y ago
    What I know is that technological progress was very slow, until suddenly there was a breakthrough and it rapidly accelerated. Now, we have enough of the fundamentals down that new technological breakthroughs are happening extremely rapidly. What a time to be alive, of course, but what suggests alien civilizations wouldn't follow the same trend of rapid acceleration rather than constant growth?
geor9e 3y ago
Constants are the simplest assumption. It's a "first round" of modeling that lets you start having philosophical thoughts on the implications. You can always increase the complexity of the model after. If you don't hold some parameters constant, the model quickly becomes too complex to be of much use for philosophical questions. In reality, a civilization can expand with exponential acceleration, deceleration, or shrink. I didn't even think this the worst of the assumptions. The fact that expansion stops as soon as a civilization meets another seems silly too. As we know, civilizations love nothing more than respecting borders and not conquering each other. But again, it can go either way, so they chose the middle assumption.

pfdietz 3y ago

> Advanced aliens really are out there Stopped reading right there.

behringer 3y ago
You're missing out then. That's the assumption being made in the paper and they take it as far as they can while sticking to some semblance of reality. Very interesting ideas in here.

GavinB 3y ago

This is a compelling theory, especially the implication that humans are early. I do wonder whether we should see the evidence of spheres of growing alien influence out in the stars, but instead we see a highly uniform universe in all directions. This would indicate a few possibilities: 1. Expanding alien civilizations are relatively low impact and don't collect all of the energy of stars in ways that are visible to our current telescopes. 2. We are a very early civilization, civs are fairly rare, and we're relatively alone in the parts of the universe that we can see. Civs that are expanding in a grabby fashion started less recently in years than their distance in light years. 3. Aliens expand at close to the speed of light, so there are a lot out there but we won't see them until they're almost here. 4. Something that we have already noticed is actually evidence of grabby aliens, but it is happening in every direction so we assume that it is a natural phenomenon, because it is so uniform. At the very least, it seems likely that we either we are alone in the galaxy, or expansion is very slow. The idea of "expanding in a bubble of influence close to the speed of light" seems implausible to me, just because of the vast amounts of energy required to accelerate and decelerate to relativistic speeds, not to mention protecting the cargo in transit--when you're flying at .9c, almost every other piece of matter in the universe is flying towards you at you at .9c. Accelerating tiny nanomachine von Neumann probes might be a solution, but how would they decelerate enough to not be destroyed on arrival? It's all fascinating to think about, at least.

JPLeRouzic 3y ago
> 4. Something that we have already noticed is actually evidence of grabby aliens, but it is happening in every direction so we assume that it is a natural phenomenon, because it is so uniform * Brown dwarfs: These are objects with masses too small to ignite nuclear fusion in their cores and shine like stars. However, they are still warm enough to emit infrared radiation. * There are rogue planet candidates that do not belong to a solar system.
idiotsecant 3y ago
5. Grabby aliens do not exist because the universe is a dark forest and any detectable signs of life result in anonymous relativistic snowflake bombardment.
3y ago

gmuslera 3y ago

It feels like talking about religion. In a lot of them at the very least, there is an almighty, omniscient god, the alpha, the everyday, and the omega god, the one that maximizes knowledge, intelligence, power, whatever. And people following that religion know exactly how that entity thinks and behave. Because that entity should think like humans of the current culture does, no? With aliens, with a different culture, civilization if that concept applies, language or not, and enough technology to make interstellar travel, and all of that for thousands to millions of years, those aliens that are far beyond our imagination, well, somewhat we know how they think and should behave, now knowing the technology they should have, the knowledge about the universe they should have, philosophy or whatever. We don't even know if it will be ever practical interstellar travel, because we didn't reach that stage yet. In theory it should work... in theory I could climb stairs till reaching the moon too. People is too busy trying to figure out how advanced aliens should think, and didn't stopped to analyze how they are thinking.

kiba 3y ago
We don't even know if it will be ever practical interstellar travel, because we didn't reach that stage yet. In theory it should work... in theory I could climb stairs till reaching the moon too. People is too busy trying to figure out how advanced aliens should think, and didn't stopped to analyze how they are thinking By using our knowledge of physics, we can make reasonable speculation on what is possible and not possible, and what engineering we need to do to make these effort successful. Some people's work are so successful that they became foundational to our knowledge base today. Same as with aliens. We can make reasonable extrapolation on what we might see from the type of aliens that expand versus and aliens that don't. They are of course, guesses, and those guesses continued to be argued and refined. Note that the site doesn't assumed that all aliens are grabby, only that some are grabby aliens, and try to extrapolate on what it might look like if they are grabby.
- pavel_lishin 3y ago
  > By using our knowledge of physics, we can make reasonable speculation on what is possible and not possible, and what engineering we need to do to make these effort successful Our speculation is only as good as our understanding of physics. Which is pretty good! But people in 1800s thought they had discovered just about everything to be discovered, and thought themselves at the end of physics, too.

Donaldobob 3y ago

[flagged]

pavel_lishin 3y ago

> that early deadline explains human earliness. I don't buy these statistical arguments. If only one sentient species is born before 20 billion years have passed since the big bang, and ten million sentient species are born after that time, yes - statistically, you're more likely to be one of the later species. But that early worm species still exists, and experiences its existence. If they thought to themselves, "obviously there's others out there, it's statistically certain!", then they are wrong.

behringer 3y ago
20 billion is a long time, and the universe is very big. And we're not the first galaxy to form within that 20 billion year time frame. It's very likely we're not the first in the universe and it's also likely we're not alone in coming to sentience at this very moment in the universes life.
- MrScruff 3y ago
  What I don't understand is how we reasonably quantify the probability of sentient life evolving. Sure the universe is very big, but the probability could be very small. All the discussions I've seen make the assumption that there's nothing unusual about life on Earth and given similar conditions elsewhere we would expect to see life, but how does one conclude that from a sample size of 1?
  - qnleigh 3y ago
    I guess the argument is something like 'if life is unlikely to evolve, then it is surprising to find ourselves existing so early in the history of the universe. If life is likely to evolve, then how do we explain being apparently alone?' and then the grabby aliens theory tries to answer the second question. I don't find the argument convincing though (per my other comment)
    - pfdietz 3y ago
      But we are not "so early" in the history of the universe. Something like 95% of all the stars that will ever be formed have already been formed. It's actually rather late in the day.

eightysixfour 3y ago

> While the current date is 13.8 billion years after the Big Bang, the average star will last over five trillion years. That does not seem right. Isn't the lifespan of a star between 100m and 100b years or so?

eschaton 3y ago
I think it depends on what you mean by “last,” a star might “last” even longer than 5×10^12 years before the last component nucleons of its remnant evaporate. If you consider how long a star lasts to be how long it emits around the same amount of energy until becoming another class of object the time will be shorter. Sol will grow large and red in another 4×10^9 years or so, then after that phase it’ll leave a stellar remnant like a brown dwarf or neutron star, which will last another period of time. How long did Sol last?
- brazzy 3y ago
  No, it doesn't depend on any such interpretation. The key word is "average". A majority of stars are red dwarves, and those do in fact last for trillions of years without significant change.

dang 3y ago

Related: Grabby Aliens: A Resolution to the Fermi Paradox - https://news.ycombinator.com/item?id=33402628 https://news.ycombinator.com/item?id=33402628 - Oct 2022 (334 comments) Grabby Aliens - https://news.ycombinator.com/item?id=26502232 https://news.ycombinator.com/item?id=26502232 - March 2021 (176 comments) A Simple Model of Grabby Aliens - https://news.ycombinator.com/item?id=26045731 https://news.ycombinator.com/item?id=26045731 - Feb 2021 (80 comments)

ck2 3y ago

the fantastic PBS Space Time on the subject https://www.youtube.com/watch?v=uTrFAY3LUNw https://www.youtube.com/watch?v=uTrFAY3LUNw

mapmeld 3y ago

My go-to counterargument for this is that galaxies are really far apart (from us to Andromeda is 25x the diameter of the Milky Way). If you haven't developed FTL travel, it's a long haul with very little benefit on the way.

a_wild_dandan 3y ago
Your "counterargument" is a presumption in Fermi paradox models. The alternative isn't particular interesting.

Animats 3y ago

Actual article: [1] "We estimate that loud alien civilizations now control 40%–50% of universe volume, each will later control ∼ 10^5 to 3 × 10^7 galaxies, and we could meet them in ∼200 Myr–2 Gyr." Those numbers seem inconsistent. "Ours is a model of grabby aliens, who by definition (a) expand the volumes they control at a common speed, (b) clearly change the look of their volumes (relative to uncontrolled volumes), (c) are born according to a power law in time except not within other GC volumes, and (d) do not die unless displaced by other GCs." That's an interesting set of assumptions. Kind of a 1960s science fiction model. If we now have a reasonable understanding of physics, you get a different model. No FTL, radio works at light speed, Technological civilizations may not last all that long. Human civilization is about 6,000 years old. Heavy industrial civilization is about 200 years old. Most mineral resources already are past the point where the easy stuff has been mined. The USGS tracks total worldwide mineral resources.[2] On a scale of years, things look good. On a scale of centuries, not good. On a scale of millennia... [1] https://iopscience.iop.org/article/10.3847/1538-4357/ac2369/pdf https://iopscience.iop.org/article/10.3847/1538-4357/ac2369/... [2] https://www.usgs.gov/publications/mineral-commodity-summaries-2024 https://www.usgs.gov/publications/mineral-commodity-summarie...

cryptonector 3y ago
The speed of light is a tremendous limitation. W/o FTL there's no such thing as "loud alien civilizations" that can "control 40%-50% of [the] universe['s] volume".
- XorNot 3y ago
  Rather depends on other factors though: you can perfectly well run an interstellar empire with very long communication times and people going into suspended animation for transit. Control strategy simply has to adapt accordingly: i.e. a message probably comes with a fleet sufficient to ensure its obeyed. This was one of the ideas in the Doom novelizations: that the aliens had spent so long travelling that there was little chance of victory because of you attacked a place you took along everything needed for overwhelming victory.

brazzy 3y ago

This kind of thing always has the same weakness: it's extrapolating from a sample size of one. It of course tries to account for that by adding large error margins based on what we know, but for some of them it's pure guesswork that could easily wrong.

qnleigh 3y ago

I'm confused by the argument here; is the argument that 'humanity could not arise once the universe has been taken over by grabby aliens, so a possible explanation of finding ourselves existing so early in the history of the universe is that this will be the only opportunity'? But if the universe will soon be filled with gajillions of grabby aliens, who's to say that we couldn't have been born as grabby aliens instead of humans? In fact if there will be so many of them, isn't the fact that we're not grabby aliens ourselves evidence that there will be no grabby aliens? I feel like there is some implicit assumption about 'who you are likely to be born as' that I'm not getting here. Do I need to assume that I could only have been born as a human for the argument to go through?

ben_w 3y ago
It's saying there's a good chance we'll be one of the grabby civilisations. Or at least, it doesn't rule it out. Non-grabby aliens aren't visible in this model; given the distances, "grabby" is the only way to change the environment enough for current human tech to even notice something unusual.
- qnleigh 3y ago
  But if we'll become a grabby civilization, then there will presumably be at least trillions of humans born in the distant future who will live all throughout the universe. Isn't it that an extraordinary coincidence to find oneself born among the first few billion? Incidentally, Carl Sagan used the above line of reasoning as a sign that human civilization was going to collapse before a few more doubling times.
  - ben_w 3y ago
    > Isn't it that an extraordinary coincidence to find oneself born among the first few billion? The weakness of the mediocrity principle is we're in a lot of categories, and we can't be near the middle of all of them at the same time. This paper makes one particular assumption about what's a good set of things to be mediocre about; I think that's the weakest part because it's so easy for intuition to mislead there. So I could invert your surprise: No more so than finding yourself in the last of a few trillion things that evolved into humans.

Towaway69 3y ago

My thinking is that the universe is full with life and communicating life. However communication is only possible with the right technology. What is that technology? Technology that can only be created by a harmonious society working together to share ideas and combine ideas from everyone in a non competitive manner. In that way the universe ensures peace and harmony ensures knowing that warring civilisation aren't able to leave their home base nor communicate with the universe. It might sound slightly esoteric and spiritual but there many ways to societally live together in harmony with all humans. After all not one individual can completely understand the universe, how can one nation hope to reach out to a non understandable universe.

8jef 3y ago
The idea of global harmonious cooperation represent the main evolutionary threshold appearing before us all. This should be our future, if We all individually find enough trust in ourselves, and let us collectively evolve in such direction. And as We, I do not foresee only human beings, but more broadly the Living, as We, interspecies from Earth. Finding a way to unite individualities should include ways to establish communication channels with so-called wildlife individuals. The idea of considering such a path being esoteric is a way to get distrustful people on board, which may be a waste of time and resources. We should focus on uniting everyone who already think this is the new normal.
- Towaway69 3y ago
  Well said and thank you for saying it. And yes, we should start at home and begin communicating with our surroundings. Be it the planet or the species with whom we share this spaceship earth.
yreg 3y ago
How can a particular technology have a non-competitive harmonious society as a hard requirement for it's discovery?
- Towaway69 3y ago

not_the_fda 3y ago

I think there is a great filter. The trait that makes a species grabby is also the trait that leads to its downfall. They end up destroying their home ecosystem before they can achieve inter-solarsystem travel, wiping themselves out.

bonzaidrinkingb 3y ago

This theory is itself grabby, and grabs itself at that. > Furthermore, we should believe that loud aliens exist, as that’s our most robust explanation for why humans have appeared so early in the history of the universe. But if loud aliens will soon fill the universe, and prevent new advanced life from appearing, that early deadline explains human earliness. Even furthermore, we should believe that Big Foot Medusas exist, as that's our most robust explanation for why humans have not seen these yet and are still alive. Since Big Foot Medusas turn everything alive into stone upon observation, and we are still here, it suggests we are early in our explorations and observations of Big Foot Medusas. Anyway, a loud grabby alien civilization expanding is "first come, first serve". Perhaps we have not seen grabby aliens, because the first grabby aliens became quiet, and make new grabby aliens impossible, or they finally became superrational and realized they need more than one civilizations to have an economy, cooperation, cosmodiversity, or competition: If aim is to win at tennis, you can't play tennis alone. As for earth specifically, it was probably already grabbed, and humans are the terraforming organisms put in service of the grabbies to make our planet habitable. Or the grabbies are in such a zeal to expand and get the most of our galaxy that they focus on planets that are close to the horizon, after which they will be moving away at faster than light speeds due to accelerating expansion of the universe. Only after that will they get around to Earth (first building a Dyson Sphere around the universe to harness its energy).

Veserv 3y ago
Of course it makes no sense if you are answering the wrong question. The question being asked is not: "Why do we not see grabby aliens?" The question being asked is: "Under what circumstances can humanity become grabby aliens that colonize the galaxy in reasonable time given that we do not see grabby aliens?" The simplest circumstances that would allow humanity to become grabby aliens in the future is that becoming grabby aliens is easy for a modern human-like society. However, grabby aliens that colonize the universe in reasonable time preclude humanity from existing if we intersect with their existence. That means there must either be something else special about our existence, or that we are unlikely to ever become grabby aliens. That is the entire point of the thought exercise, figuring out if there is a hope that humanity will become grabby aliens (Star Trek).

gcanyon 3y ago

In case anyone is interested in how grabby aliens (or we!) could travel the galaxy, Kurzgesagt has an excellent video on building a stellar engine to move our solar system at up to 50 light years per million years. Setting aside considerations of whether we'll survive the next few decades as a technological civilization, let alone the next few millions of years, the Caplan engine would let us colonize a significant fraction of the galaxy within a billion years or so. https://www.youtube.com/watch?v=v3y8AIEX_dU https://www.youtube.com/watch?v=v3y8AIEX_dU

jojohohanon 3y ago

Why are we now? https://www.ox.ac.uk/news/science-blog/why-are-we-now https://www.ox.ac.uk/news/science-blog/why-are-we-now It’s early here, but it think the gist of it is using Bayes to quantify: Given that the universe would seem to get more hospitable at older ages, why are we alive now? IIUC the most likely explanation is some secondary force (aliens) to modify the future hospitality.

deleted 3y ago
[deleted]

flenserboy 3y ago

Ecosystems on Earth might be a better way of thinking about this. Notice how we do not see one organism or type of organism squeeze out all the others, or work to take in all energy available to them; this is also true of human settlements, whether rural or urban. There is a clear diversity of energy extraction methods, & singular dominance (think algae-clogged lakes) tends to lead to stagnation & death. Mechanical expansion might look grabby (as in Von Neumann probes), but life expanding through the universe could instead follow biological & human-settlement patterns.