What do you think the Great Filter is?

The Great Filter is the idea that, in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.

https://en.wikipedia.org/wiki/Great_Filter

The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. As a 2015 article put it, "If life is so easy, someone from somewhere must have come calling by now."

https://en.wikipedia.org/wiki/Fermi_paradox

Personally I think it's photosynthesis. Life itself developed and spread but photosynthesis started an inevitable chain of ever-greater and more-efficient life. I think a random chain of mutations that turns carbon-based proto-life into something that can harvest light energy is wildly unlikely, even after the wildly unlikely event of life beginning in the first place.

I have no data to back that up, just a guess.

Carrolade ,

My guess would be self-replicating biological organisms capable of significant rates of mutation.

But then my preferred solution to the paradox as a whole is basically the "nobody tries" idea.

I don't think there's tremendous reason to try to make ones-self detectable at long distances. It's an expenditure of non-trivial resources for an uncertain result. Since there isn't really any robustly sound logic for making the attempt outside of dramatized sci fi stories, I imagine a vanishingly small percentage of occurrences of intelligent life would make a serious, high-powered attempt at any point.

Cryophilia OP ,

I don't really subscribe to the theory, but I think the idea that alien races are all like "go to SPACE? Why the fuck would we do that?? It sucks up there!" is definitely the funniest solution to the Fermi paradox.

HubertManne ,

I always thought of it as a series of tests or filters. Like a multistage filter. So like nukes is one, responsible environment management is another. Something like photosynthesis is more of a conditions for life to emerge thing to me really. If like can flourish to begin with then mutations are common enough that things like photosynthesis are inevitable.

Kolanaki ,
@Kolanaki@yiffit.net avatar

I always thought my Pür was great. /s

MrMobius ,
@MrMobius@sh.itjust.works avatar

There is a great video about the Great Filter by Kurzgesagt/In a Nut Shell. If I remember correctly, in it they say we can guess at which stage the filter is by how evolved extraterrestrial life forms are.
So it's actually great if we find a lot of bacteria or other primitive life forms, that would mean we probably already have overcome the Geat Filter on Earth.
On the other hand, if we find many alien ruins of several civilizations at or above our technological level... Well, our greatest challenge might be coming.

zout ,

I think that for a technological civilization to rise, you need some things to line up. First, life has to be evolved enough to have animals, beings with a brain. Then, a species has to evolve intellence to become a tool making species. This species also has to become the dominating species on the planet. Meanwhile, extinction events, ice ages, climate change and population bottlenecks are always influencing the evolution process.

This is for me the great filter, to have all these conditions line up perfectly for an intelligent, tool making species to evolve and thrive.

ShittyBeatlesFCPres ,

For a technological civilization like ours, I think it’s just that Earth/humans are weird and we’re past the main ones (like going from single-cell to multi-cellular organisms).

Having to overcome the physical obstacles on other planets rules out the type of spacefaring technological civilizations like ours. No matter how intelligent a civilization on a water world is, it’s not starting fires, much less building rockets. Just getting out of the water would be their space program. Even a totally Earth-like planet that’s a bit bigger and has an intelligent species wouldn’t be able to get to space with chemical rockets.

And also, humans are weird. It could be as basic as “we have hands for building complex tools.” We have a seemingly insatiable need to compete and explore, even beyond all logic—maybe no other intelligent species wants to strap someone to a rocket and send them to space because it sucks up there. We’re violent: without WWII and the Cold War, do we even have a space program?

So many things had to come together to create an intelligent, tool-building species with hands that lives on a planet with the right balance of land and water. As far as we know, it never even happened on Earth before and even then, we had thousands of years of civilizations before anyone was dumb enough to strap themselves to a rocket just to see what would happen.

Cryophilia OP ,

I definitely subscribe to the "humans are insane" theory of galactic lifeforms

HaleHirsute ,

I like the “Dark Forest” theory I learned from the Three Body Problem books. Basically it’s dumb for civilizations to make a big footprint and reveal themselves because other civilizations won’t know how powerful and dangerous you might become, and so out of precaution they might just zap you. Ironic and over dramatic, but just because that’s a possibility it might be wise to keep a low profile and not invite trouble.

Lmaydev ,

Tbf we are noises as fuck. We've been sending so much out for decades.

HaleHirsute ,

Sure, but it’s just small game chatter. We start building a Dyson sphere powered starkiller cannon or some such nonsense we might pop up on somebody’s radar.

FaceDeer ,
@FaceDeer@fedia.io avatar

The problem for the Fermi paradox is that there's no reason to do stuff like that before we start colonizing other solar systems.

Also, how do you destroy a civilization that has a Dyson swarm already? That's not exactly an easy task, and if you insist on remaining stealthy yourself it's nigh impossible.

FaceDeer ,
@FaceDeer@fedia.io avatar

The "Dark Forest" is fine for a scary sci-fi series, but it has many flaws that make it unrealistic as a real solution to the Fermi paradox.

  • Earth has been quite obviously life-bearing for at least 2 billion years. We should have been wiped out long ago.
  • The book series made up fantasy magic tech for how exactly a civilization can be destroyed by another without giving away their own location. I've yet to see an explanation for how that would be done in reality that doesn't give away the attacker's location.
  • It doesn't explain why nobody has colonized the galaxy.
HaleHirsute ,

I think others wouldn’t bother with us until we started demonstrating likelihood of using dangerous tech or crazy exponential expansion.

I don’t remember well, but I think civilizations stationed their defensive or offensive tech away from their own civilizations, just dispersed around.

I think its explanation for why no one or anything has colonized the galaxy though is that if anyone shows signs of becoming that strong, they get zapped. Nobody wants to see a neighbor rise up into a behemoth, you get that bold you’re a threat.

My real preferred theory of why we don’t see other civilizations though is that I think they choose more inward, VR, computer-based evolution that doesn’t result in big mega structures.

FaceDeer ,
@FaceDeer@fedia.io avatar

I think others wouldn’t bother with us until we started demonstrating likelihood of using dangerous tech or crazy exponential expansion.

Why do you think that, though? It doesn't make sense, frankly - if you're worried about competition evolving you shouldn't wait until the last possible second to destroy it. That raises so many unnecessary risks of being slightly slow on the draw, and then it's too late. Why not do it at the earliest convenience, when it's super easy to do by comparison and there's an incredibly long margin of error if you somehow miss the first couple of tries?

I don’t remember well, but I think civilizations stationed their defensive or offensive tech away from their own civilizations, just dispersed around.

I think its explanation for why no one or anything has colonized the galaxy though is that if anyone shows signs of becoming that strong, they get zapped.

But they're already doing it, you just said they're putting outposts out there. If they can't do that secretly then the Dark Forest doesn't work in the first place. Placing a secret weapon base in another solar system is no different from placing a colony there.

My real preferred theory of why we don’t see other civilizations though is that I think they choose more inward, VR, computer-based evolution that doesn’t result in big mega structures.

As with many Fermi paradox solutions this one fails on account of requiring every single civilization (and every single subset of those civilizations) to all decide to do exactly the same thing, forever, with no exceptions. In a scenario like this what happens if a single subculture of a single advanced civilization decides for whatever reason that they prefer not to do that? They would be able to spread throughout the cosmos without opposition, everyone else is locked in their little dream boxes and therefore is basically irrelevant. It only needs to happen once, and the universe has been around for a very long time.

HaleHirsute ,

I agree, I don’t think they’d wait until the last possible moment when the civilization becomes super powerful or builds the mega weapon. I just mention it along the range of development to highlight the why.

I think they might let weaker civilizations keep going, though, just out of hope they wouldn’t be too mean. Also, zapping other civilizations when you don’t need to exposes yourself and your own aggression.

About the shift to VR /computer substrate worlds that wouldn’t have huge footprints, I agree that not all would do that, and it only takes one to go the big building and footprint route and it’s weird we don’t see it.

My guess then would be that maybe they do build big, but they just conceal well..? You get good enough tech at some point you can choose to be hard to see.

Cryophilia OP ,

I've never read the three body problem (started it but just couldn't finish...it was very slow paced and there were moments when the Chinese...I don't want to call it propaganda but more like promotion...took me out of it, like the supposedly international coalition of scientists where the non Chinese ones were just cardboard cutouts) but I can speak to this:

The book series made up fantasy magic tech for how exactly a civilization can be destroyed by another without giving away their own location. I’ve yet to see an explanation for how that would be done in reality that doesn’t give away the attacker’s location.

Relativistic missiles. Nothing moves faster than the speed of light. So if you can get a big rock to go 95% of the speed of light, we'd only be able to detect that it's coming right as it hits. Sure, you can calculate the origin of the missile after it obliterates its target, but it's almost impossible to form a counterattack especially if the attacker just yoinked an asteroid from a different star system than their own and strapped an engine on it. And ESPECIALLY if your civilization is still mostly planetbound.

And a rock moving at some appreciable fraction of the speed of light could obliterate the Earth.

FaceDeer ,
@FaceDeer@fedia.io avatar

Relativistic missiles. Nothing moves faster than the speed of light. So if you can get a big rock to go 95% of the speed of light, we'd only be able to detect that it's coming right as it hits.

This is a very common answer to "how", but it comes with lots of problems in the Dark Forest context.

  • If you actually calculate how much energy is required to boost a big rock up to that speed you run into lots of difficulties. It takes a lot, a heck of a lot. How does a civilization that is "hiding" accumulate that energy? How does it store it long-term?
  • How is that energy actually put into the rock? This is basically a starship accelerating up to that speed and getting a starship up to that velocity is not easy even if you have the energy available. Does it have a rocket? The rocket equation for getting up to near-lightspeed requires ridiculous amounts of propellant. Is it beam-propelled? You're not being at all stealthy that way. How much acceleration can you get out of your system? It takes a full year at one Earth gravity of acceleration to get up near lightspeed, and that's a really high acceleration - you generally trade acceleration for efficiency so the faster you want to get up to speed the more energy you need and the noisier you'll be.
  • It actually is possible to counter an RKV. It's much easier to hit and destroy an RKV than it is to launch it, all you need to do is get a pebble in its path. The key is detection, and the above points give some pretty good options for detecting it before and during launch. That gives you time to fire your countermeasures.

And ESPECIALLY if your civilization is still mostly planetbound.

Absolutely not guaranteed to be the case. Earth's civilization could have easily had offworld colonies by now if circumstances had been slightly different, so a Fermi paradox solution that requires reliably blowing up Earthlike civilizations before they can get offworld doesn't work. They're already too late.

As I said previously, Earth has been quite obviously life-bearing for at least 2 billion years. Why wait until something like an RKV is needed, and even that is not guaranteed? They could have destroyed life on Earth far easier, and thus far more stealthily, if they'd done it a billion years ago.

Cryophilia OP ,

I agree, either we've escaped detection or the dark forest theory is wrong.

Couldn't antimatter bursts get an object to extremely high speeds relatively cheaply?

FaceDeer ,
@FaceDeer@fedia.io avatar

Well, "relatively cheaply" is a hard standard to nail down. I would say "no", though. Antimatter is very expensive to manufacture and store and you're going to need a lot of it. All of the energy that comes out of an RKV hitting its target has to be put into it in the first place, probably several times over given the inefficiencies likely inherent in the process.

Cryophilia OP ,

Fair enough, guess it depends on how many resources they're willing to sink into first strike capability. Maybe a strongly expansionist civilization would have such a more efficient use of resources it would quickly catch up to a dark forest predator trying to wipe them out. Like a swarm of piranha eating a shark.

papertowels ,

Earth has been quite obviously life-bearing for at least 2 billion years. We should have been wiped out long ago.

I believe the theory is that as civilizations broadcast a signal indicating life exists strong enough such that it is picked up by other civilizations, the dark forest theory applies. Essentially we haven't broadcasted a signal loud enough to be picked up

FaceDeer ,
@FaceDeer@fedia.io avatar

But that's not actually true. We've been "broadcasting" the fact that there's life on Earth in the form of the spectrographic signature of an oxygen-rich atmosphere, which is a clear sign that photosynthesis is going on. There's no geological process that could maintain that much oxygen in the atmosphere. The Great Oxidation Event is when that started.

We have the technology to detect this kind of thing already, at our current level. Any civilization that could reach out and attack another solar system would be able to very easily see it.

papertowels ,

This is quickly becoming beyond my knowledge pool, but does this assume that all life is intrinsically linked to oxygen?

FaceDeer ,
@FaceDeer@fedia.io avatar

It's not specifically oxygen that's linked to life, it's chemical disequilibrium. Oxygen is highly reactive, there are lots of minerals that will bind it up and there aren't any natural geological processes that unbind it again in significant quantities. If you put an oxygen atmosphere on a lifeless planet then pretty soon all of the oxygen will be bound up in other compounds - carbon dioxide, silicon oxides, ferric oxides, and so forth. There has to be some process that's constantly producing oxygen in vast quantities to keep Earth's atmosphere in the state that it's in.

There are other chemicals that could also be taken as signs of life, depending on the conditions on a planet. Methane, for example, also has a short lifespan under Earthlike conditions. You may have seen headlines a little while back about the detection of "life signs" on Venus, in that case it was phosphine gas (PH3) that they thought they'd spotted (turns out it may have been a false alarm). These sorts of gasses can be detected in planetary atmospheres at interstellar distances, especially in the case of something like Earth where it's quite flagrant.

Even if these are sometimes false alarms, in a "Dark Forest" scenario it'd still be worth sending a probe to go and kill whatever planets exhibit signs like that. It's a lot cheaper and quieter than trying to fight an actual civilization. That's why I can't see why we wouldn't have already been wiped out aeons ago in this scenario.

papertowels ,

Thanks! That's a different way of looking at the problem that I hadn't considered.

intensely_human ,

The galaxy is a bowl of M&Ms. One
of every hundred M&Ms is poisoned and will
immediately kill you. It’s only a 1% chance you’ll die. Well maybe pike 5% if you eat a handful.

Most of the civilizations might even be moral enough not to destroy us, but all it takes is one.

HaleHirsute ,

Yep exactly. Who knows how murderous other civs might be, maybe they’re nice but maybe not.

FaceDeer ,
@FaceDeer@fedia.io avatar

How do they do it, though? It's not really a valid solution unless you can explain how it works, otherwise it's just "maybe some magic happens that kills civilizations."

Once a civilization has begun spreading to hundreds of other solar systems I have yet to hear of any plausible way to reliably "kill" it.

intensely_human ,

Guns? Bombs? Surely you can kill a civilization. Not sure why magic would be required.

FaceDeer ,
@FaceDeer@fedia.io avatar

I don't think you've thought through the logistics required for the sort of war where you'd just go around and shoot everyone who lives in hundreds of solar systems. Even assuming they do nothing at all to defend themselves, how do you even find them all?

Bishma ,
@Bishma@discuss.tchncs.de avatar

The way the news has been going I wouldn't be surprised if plastic is a candidate. After a little less than a century of rapid development in petrol-plastics we're starting to figure out the long term effects. But the next 1000 generations may be dealing with the fallout.

invertedspear ,

Petroleum may be both an accelerator and a filter. Filter in the form of plastic, like you’re saying, but maybe it’s weird that crude oil even exists in the first place. An era where plants die, but don’t decompose may be a rarity in itself. Then the geologic activity that buried that dead plant matter, but not too deeply for us to get to, seems like it could also be a rarity. So then we get this energy source that’s pretty energy dense and allows massive technical acceleration, but then poisons us and salts the earth behind us. Look how shortly we went from the first fixed wing flight to rocketing to the moon, amazing how short that time was. Hydrocarbons, allowing us to touch the greatness we could achieve, before smacking us back down.

Hugin ,

An alternative is we are among the first. Third generation stars are the ones that have planets with enough heavy elements to allow for complex chemistry. Sol (our star) is thought to be among the first batch of third generation stars in our gallexy.

Light speed does seem to be the upper speed limit for the universe. Talking that into account we probably haven't had a chance to see other early life as it would likely be spread pretty thin right now.

Cryophilia OP ,

Yeah, I have a gut feeling that a lot of the variables in the Fermi equation are a little too generous.

Kyrgizion ,

I do agree that in the grand scale of things we're actually very early. That alone would explain a lot.

sxan ,
@sxan@midwest.social avatar

This is my favorite, mainly because it's been well argued by some respectable scientists.

Another is that we're in a simulation, and aliens aren't part of it. There are also some very good statistics pointing to the simulation theory, from just sheer scale.

SwingingTheLamp ,

Honesty, I don't think that there is a Great Filter. The Fermi Paradox strikes me as not very well-reasoned. A whole hell of a lot of things would have to go exactly right for civilizations to make contact, rather than it being the default assumption. There are lots of filters, not just one Great one.

But the closest to a Great Filter is that space is really, really. stupendously big. The chances of even detecting each other across such distances is vanishingly small, much less traversing them. Add in the difficulty of jumping the metabolic energy gap to become complex life, and that could reduce the density of civilizations down to a level that they're just not close enough to each other in spacetime to admit even the possibility of contact. And we're hanging our hat on some highly-speculative concepts like alien mega-structures harnessing whole solar systems to allow detection.

I think a lot of persnickety, smaller filters combine to make interstellar contact between civilizations against long odds. Perhaps the best we'll get is spectral signatures from distant planets that are almost-conclusive proof of some sort of life.

Cryophilia OP ,

I think at some point, almost certainly not in our lifetimes, we'll detect the spectroscopic signatures of a planet that has an atmospheric makeup that HAS to be from life, but with no detectable signs of any civilization. Just nonsentient life. And we may never be able to get there.

Gradually_Adjusting ,
@Gradually_Adjusting@lemmy.world avatar

I think you're probably closest. There aren't "filters" so much as we live in a universe that can only support life on a highly contingent basis, entirely by accident, at random intervals. It's filters all the way down, really. None of us are getting out alive, might as well enjoy it while it lasts.

cynar ,

I don't think there is a single filter. My personal gut feeling however is that the jump to "specialised generalists" would be a major hurdle.

Early human civilizations are very prone to collapsing. A few bad years of rain, or an unexpected change of temperature would effectively destroy them. Making the jump from nomadic tribal to a civilisation capable of supporting the specialists needed for technology is apparently extremely fragile.

Earth also has an interesting curiosity. Our moon is extremely large, compared to earth. It also acts as a gyroscopic stabiliser. This keeps the earth from wobbling on its axis. Such a wobble would be devastating for a civilisation making the jump to technological. Even on earth, we are in a period of abnormal stability.

I suspect a good number of civilizations bottleneck at this jump. They might be capable of making the shift, but get knocked back down each time it starts to happen.

Cryophilia OP ,

Speaking of our moon, the fact that it's roughly the same size as the sun as seen from earth and the fact that this is a complete coincidence blows my mind. Like there's no reason for that to be the case. Total eclipses like ours (where you can see the corona) are very rare.

cynar ,

Even more so, the moon is slowly moving away from the earth. A couple of million years ago, it would have completely covered the sun. In a couple of million years, it will not fully cover the disc.

A million years is a long time for humanity, but a blink on the timescale of moons and stars. We didn't just luck out with the moon's large size, but also with the timing of our evolution.

Cryophilia OP ,

That's nuts. In two million years, humans will be sighing and saying wistfully "if I had a time machine, I'd want to go back to the time of the full eclipses, like 2024"

Asafum ,

Earth also has an interesting curiosity. Our moon is extremely large, compared to earth. It also acts as a gyroscopic stabiliser. This keeps the earth from wobbling on its axis. Such a wobble would be devastating for a civilisation making the jump to technological. Even on earth, we are in a period of abnormal stability.

There seem to be so many coincidences that make our solar system unique that it's really upsetting lol It's like we are so perfect for stability because of things like Jupiter keeping the inner system "clean" of large impactors, our part of the galaxy being more "quiet" than typical as far as supernovae, stuff like that which makes it seem even less likely for life to exist anywhere else. :(

cynar ,

Life will almost certainly be fairly common, given the right conditions. On earth, it seems to have appeared not long after conditions made it possible. We either won the lottery on the first week, or the odds aren't actually that bad.

The problem is, we can't detect life right now. We can only see potential communicating civilisations. These are a lot rarer. We currently know of 1, humanity. That will change in the next few years. We have telescopes being designed/built capable of detecting the gasses in the atmosphere of an earth sized planet. While we won't recognise all life types this way, a lot will show up in abnormal gasses, e.g. free oxygen. This should help bound the possibilities a lot.

RealFknNito ,
@RealFknNito@lemmy.world avatar

Hard to determine with what we know. We haven't met any other intelligent species which suggests we've passed the filter. Yet, making that conclusion before knowing there are no others to meet is too presumptuous. But, if I were to guess, I'd think the filter is adaptability.

We're superior to animals for being able to use tools, live in radically different climates, and shape every spot on earth into a livable climate. Even on Mars, the moon, and space. How else would a species venture through space if they can't adapt?

That might be too general a concept for the question though.

doctordevice ,

We haven't progressed far enough to be detectable by intelligent life in other star systems, even the closest ones. The filter can easily be in front of us. It could just simply be that interstellar space travel is too infeasible, so intelligent species never reach beyond their home system.

RealFknNito ,
@RealFknNito@lemmy.world avatar

Yet we haven't even found other planets with complex dumb life, much less ones with intelligence, communicative life. Nothing like what we have on Earth, not even close. Either space is too big or we're past the filter.

doctordevice ,

We are nowhere near advanced enough to say that life, complex or intelligent, doesn't exist anywhere near us. There is no reason to believe an intelligent spacefaring race would make themselves so obviously detectable that us stupid primates could see them. And for non-intelligent life, we've been able to confirm mere thousands of planets. We have a very long way to go before we can start talking about the meaningfulness of a lack of life signatures in the atmosphere.

weeeeum ,

I think it would be nuclear warfare. Nuclear fission is a universal development for any advanced civilization. It would be easy to construct a nuclear bomb in an advanced civilization. Once a few rogue/pariah states start making them, everyone's screwed.

Making nukes is easy, the only reason we don't see more nuclear states on earth is because of the international backlash. With a couple more Iran and North Korea's we'll likely meet the filter ourselves.

Nutteman ,
@Nutteman@lemmy.world avatar

I personally find the kardashev scale a pretty terrible way to measure the success of a civilization. Maybe the most successful life forms don't become technologically obsessed materialists determined to colonize everything habitable and drain the resources of everything else, yknow?

Melvin_Ferd ,

I mean then how did they become a life form

Nutteman ,
@Nutteman@lemmy.world avatar

I wasn't clear enough I don't think when I wrote that. I meant that as in the most successful intelligent life forms don't separate themselves from their ecosystems nor disrupt it in the way we do.

theywilleatthestars ,

Either multicellular life or that societies that are bent on expansion at any cost tend to destroy their planet's ecosystem before they can establish themselves outside of it.
Not making a definitive claim on either, obvs. We have an extremely low sample size after all.

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