Two things to bear in mind when thinking about the Fermi paradox:
1) The more important observation is that everything we see is a wilderness of apparently natural origins and processes, not that we have apparently not been visited.
2) No hypothesis involving choice that leads to failure to carry out self-replicating colonization can explain (1). All it takes is one small group in one sufficiently advanced species. This rules out wolves, berserkers, relinquishment, self-destruction, and so on and so forth.
Clearly something is missing or incorrect in how the pieces of the various sciences fit together to explain what we see. Some of the best reading on the subject is speculation on what it is that we don't know or the relative odds on where the present consensus is incorrect.
There remain some big tests, among them: Can we accumulate and release enough energy to take us to the stars without having a civilization-ending war with ultra-destructive directed energy weapons? Can we avoid mistakes in modifying life, and in nanotech, that would cover the planet in goo? Can we master germline modifications of humans without doing something that ends with no humans, and no post-humans? So plenty of filter to go yet. Never mind the smaller-scale "do we have way too many humans already to not overheat the planet we're on?" questions.
>Can we accumulate and release enough energy to take us to the stars without having a civilization-ending war
This is why, if I invented antimatter production, I would absolutely demand that it not be used on Earth until it had been used to send hundreds of human-bearing seed ships to other solar systems. The risk is too great.
There is a disconnect between these two statements:
"No alien civilizations have substantially colonized our solar system or systems nearby. Thus among the billion trillion stars in our past universe, none has reached the level of technology and growth that we may soon reach."
While the article is in a way all about exploring that disconnect, it's a bit strange to find it written down so explicitly in the conclusion. We can ascribe a very high level of confidence to hypothesis that neither our own nor any of the directly neighboring star systems have been colonized. But to postulate that therefore the universe has not yet produced a civilization as technologically sophisticated as our own is still a non-sequitur, at least in my opinion. The article also makes a lot of assumptions (it has to!), some plausible, some seemingly arbitrary, which might in the end not be important factors at all. For example, any consideration about radio communication must be on very shaky grounds, in particular when charting the absence of it.
The reason why we're not seeing alien neighbors or predecessors (which would be "neighbors" in time), might well be a combination of factors. While we can exclude certain scenarios, such as a cloud of Von Neuman Probes eating the galaxy, it still leaves room for a lot of little factors that can change the galactic stage for us in a fundamental way - especially if they work in conjunction.
For example, the average duration of the technologically recognizable phase a civilization goes through may be smaller, and there may well be less of them than expected. In addition, willful avoidance or isolation may well play a role; the zoo hypothesis is an extreme example of this, but in a sparse cosmos the measures you have to undertake in order to isolate an emerging civilizations become less heroic.
It's also worth mentioning that we ourselves are not past the Filter by any means. In fact, as time progresses, it seems to become less likely we'll ever move off the Earth as an exclusive habitat. Part of this is due to psychology, we could have made it happen by now but didn't. The best bet at becoming an interstellar civilization right now seems to be to wait until we're pure computer systems, unburdened by aging and the passage of time, but that development, too, might end up being something we never elect to actually pursue.
Luckily, this whole thing is a mystery we can solve over time, just by gathering data about what's out there.
The 'soonness' of our interplanetary colonization is really not safe to assume. The obstacles to self-sustaining life on other worlds are not insignificant -- in fact, they are the explanation for why there is no life there to begin with.
The problem is that if you exclude the scenarios that obviously didn't happen you are still left with no likely scenarios given the present consensus understanding of biology and physics.
The timescale for megascale engineering to occur throughout our galaxy as the result of the launch of one megascale engineering minded self replicating probe is small (1 million years) in comparison to the age of the galaxy (13 billion years). It is unlikely that we are sitting here while someone else is in the process of doing it; that's not the scenario to focus on.
All it takes, remember, is one small group in one sufficiently advanced culture to start this going. Some (post)human group will clearly do it at some point if we as a species continue. Why hasn't someone already done it, where "it" is visibly engineer the totality of the future light cone?
The problem is less one of why don't we see Dyson spheres and other similar type II projects within a few hundred light years of our position, and more one of why do we see no obviously altered galaxies among the hundreds of thousands cataloged to date. At this scale the zoo hypothesis looks stretched, and the simulation argument begins to look more plausible.
Your comment sparked an interesting question in my mind: If some entity is trying to colonize in every direction at near the speed of light what is the expected gap time between the light of the actions reaching us and them reaching and colonizing us?
A partial answer to the Fermi paradox by appeal to the anthropic principle: there is a very small fraction of time between being able to observe an alien species and being consumed by it.
Good points, but I'd like to offer some counter arguments to the megascale engineering idea, hopefully without sounding too pedantic.
The need for megascale projects is not as obvious as it's sometimes made out to be. There might well be reasonable limits beyond which the maximizing of habitat space and energy consumption tapers off in utility. Even if our civilization continues on its present course, it's not certain that we will get to the point where we (or some of us) feel the need to change the face of the galaxy. If you go one step down from the galactic stage, the detectability of solar system-scale megatech is also open to debate, especially as you move beyond a couple hundred light years from here.
You're right of course when you say all it takes is one civilization (or even one member of a sufficiently advanced society) to undertake projects that are liable to make all kinds of strange phenomena appear in our night sky. But the number if beings capable of doing so on a whim, multiplied by the chance they'd be interested in such things, might be very very small without breaking any of our current expectations about biology and physics.
Finally, I'd like to address the simulation argument. There are two extreme ends of the simulation scenario spectrum.
At the one extreme, we're talking about an artificial reality made especially for us, humans. This would be the popular "Matrix"-style simulation. No scientific argument I've heard so far makes it a convincing model for the reality we live in, except as a possible explanation for the Fermi paradox.
At the other end of the spectrum, we have a full simulated universe. It's hard to argue for or against that notion, simply because either way it fits with our observable reality. The catch is of course that it's a neutral proposition with no impact on us at all. This variant does not offer any explanation for the Fermi paradox.
As I see it, the simulation argument as pertinent to the Fermi problem offers two options, neither of which are intellectually appealing: one is a borderline-untenable just-so make-believe world where all rules are an illusion and anything can happen, and the other one is virtually undistinguishable from our "normal" world, up to and including an absence of any obvious explanation for the Fermi paradox.
I forgot who came up with the idea, but the great filter may not exist - it is just that an intergalactic civilisation wouldn't be using radio communication (due to the lag because of the slow speed of light).
Or the put it a bit different: unless the Culture want us to see it, we won't.
That is a really good question. The thing is that if they are powerful enough to actually do that, perhaps they have come up with something better?
I mean there could easily be a couple 1000 years between us, which means that the difference is at least as great as us and the Romans. The Romans might very well question why we weren't breeding more horses then, since we have such a huge need of transport and horses are the best way to do that.
Maybe it turns out Dyson spheres are a bad idea for some reason? Maybe Dyson spheres are out there, but constructed in such a way that they don't look obvious to a distant observer? Maybe the idea that advanced civilizations exponentially consuming energy as per the Kardashev Scale is a flawed and anthropocentric premise based entirely on what we know of our own civilization, and a lack of observable stellar engineering doesn't necessarily mean a lack of advanced life?
We suffer from hubris when we label it the "Fermi paradox": It implies that somehow we are interesting, worth visiting. If we are, it may well be as a cautionary tale or for tourism.
Consider the energy and material engineering necessary to achieve long-distance space transport of any sizable amount of people, equipment, and supplies. Regardless of whether the transport is subluminal or FTL, the energy requirements are tremendous and the engineering requirements for a durable vessel astounding.
My guess is that by the time our materials science and our energy production are up to the task, our interests may well have changed - because (and here I speculate wildly) science at engineering at that level will reveal so much about the fundamental nature of the universe and give us so much interesting practical technology that biochemical life clinging desperately to lucky rocks in the lucky zone won't be near so interesting anymore.
No one comes near because we have nothing to offer those able to come near and get home again to report what they found.
As to simply detecting signals, we have to consider how lucky we are to have so much ore so close to the surface: Metallurgy and eventually radiated communications were a natural for us.
Other civilizations may well start with fantastically engineered wood and eventually plastics, and go all-fibre, all line-of-sight, and have very, very different communications systems, systems undetectable at any remove.
Your argument is kind of contradictory. It assumes that we are not worthy of visiting but an argument like that suggests that they’ve already found us and interstellar travel is feasible. They’ve also solved all the logistic problems you’re referring to. Whether they like to make contact or not is somewhat irrelevant to this context.
For the sake of argument let’s linger on that assumption for a while. How for example did they found us when our civilization achieved radio signals transmission in the last couple of centuries? That means that they’re close by, unless FTL travel is feasible in which case we can safely assume the whole galaxy should be teeming with life. But if they’re close by shouldn’t we be able to spot them? And if they’re far away that means they should already have colonized half the galaxy before they decide to launch an expedition to a planet thousands of light years away.
The worrying factor relating to the “Fermi Paradox” is that it suggests that maybe life is extremely rare. We could very well be the only living souls in this part of the Universe and that’s kind of heart breaking considering the sheer size of the whole thing.
Or for a longer read, David Brin gives it an excellent and lengthy treatment in Existence [1]. He even works in an exhaustive analysis of the possible answers to the Fermi Paradox, as well as possible events constituting The Great Filter. I won't give spoilers but it's definitely worth reading.
"No one wants to talk to us" is not a sufficient explanation. We need to be able to explain why we don't observe any stellar engineering. Assuming alien civilizations they either 1) can't make use of the most prominent energy sources around, 2) choose not to for some reason, or 3) we can't detect what they're doing.
1 and 2 don't make sense if you assume that there are many alien civilizations older and more advanced than us. 3 implies that we're fundamentally misunderstanding a lot about (astro)physics.
Astrophysics is as solid as particle physics and plasma physics; it's the other laboratory used to confirm fundamental theory. The models are very good. There is a natural explanation for every well observed phenomenon that fits all known physics, and wherein the models match up to the observations. Astrophysics really isn't the place to be looking first for issues, I'd say.
I don't really know enough about physics to be able to judge, but what you say is nicely in accordance with my priors. I think we're in agreement here. I wouldn't argue that 3 was the place the argument most likely fails, merely that there is something here that we don't fully understand and which may be rather important -- hence it's reasonable to call it a paradox.
If space investment/exploration had continued in the 70s (with or without an Orion project) then by now, we would have lots of infrastructure outside the atmosphere.
I.e., a large subset of species around our level of industrial advancement ought to be close to "planetary breakout".
The point is, a Great Filter for intelligent species at our technology level would need to sterilize a whole solar system, not only on a planet. Otherwise it would miss, say, somewhere between one and ten percents of the civilizations.
So I'd guess we're past the filter.
Of course, possible filters that clean out a solar system do exist. Another species could soon wipe us out (any single galaxy just needs one early xenophobic and crazy species). Or e.g. unknown physics in a particle accelerator experiment will have very unexpected effects for the whole solar system, very soon...
We are provably not beyond the great filter. At least one great filter lies tangibly in front of us: ecological sustainability.
Barring several fairly large changes to our energy and resource systems, our civilization is mathematically and physically guaranteed to collapse within the next 200 years at most.
That's not a hypothetical filter. It's a real one that we can see, and we are not past it.
This is a great point – which I would paraphrase as, let's not worry about cosmic filters when we have a very tangible filter in front of us – but it doesn't follow that we're "provably not beyond the great filter".
The Great Filter is just the thing that explains most of why intelligent life is (or seems) so rare in the universe. It could be true, for example, that some cosmic event kills life before it becomes technological 99% of the time (= Great Filter), and also that, say, 60% of technological civilizations destroy themselves via destroying their environment.
Given that we have only one known example of intelligent life, we are the only thing we can base any predictions upon. Given that we have a provable filter in front of us, I think it's reasonable to assume that similar situations might occur elsewhere in the universe:
(1) An intelligence reaches a critical intellectual mass and begins to utilize the free resources that are present in its environment.
(2) In doing so it grows and develops exponentially.
(3) By the time it develops far enough intellectually to realize the problem -- exponential growth built on finite non-replenishable supply -- it's already too late.
We seem to have realized this problem around 1950-1970, and we have done very little about it so far. That's because huge complex systems are hard to change, and all the incentives point the wrong way.
Sure, but that's just a case for "ecological sustainability is a reasonable candidate for the GF based on what we know about ourselves." Which is a weaker statement than "we are provably beyond the GF". Provable implies strong evidence and certainty.
Painfully true. Human civilizations go back about 3000 years. Industrial civilization only goes back about 200. Being able to make a significant dent in the planet's natural resources goes back less than 100 years.
Few nonrenewable resources have a remaining supply measured in hundreds of years.
> We are provably not beyond the great filter. At least one great filter lies tangibly in front of us: ecological sustainability.
> Barring several fairly large changes to our energy and resource systems, our civilization is mathematically and physically guaranteed to collapse within the next 200 years at most.
Would you mind elaborating on this or posting some links with more evidence for this? As stated, your claim seems reminiscent to previous claims that humanity would soon not be able to grow enough food for the projected population. So far, unexpected scientific advances have managed to increase food yields substantially, and we can now effectively produce more than enough food to feed people (though we clearly have issues ensuring that food gets to everyone who needs it). So I wonder what is different now, that makes this looming catastrophe "provable" and "mathematically and physically guaranteed".
I agree that humanity is facing significant challenges (e.g., climate change), but I think the claim of "guaranteed collapse" is not as well established.
"your claim seems reminiscent to previous claims that humanity would soon not be able to grow enough food for the projected population"
This is a cautionary tale about something that stock market traders know well: never try to call the top of a bubble. You'll just look like a fool, and if you bet on it you will lose all your money.
The "Population Bomb" crowd in the 70s and the peak oilers of today tried to do just that: to call the top. They were not wrong about the underlying realities, but they were absolutely wrong about the timing -- which is nearly always the case. Bubbles almost always go higher and further than anyone ever expects or imagines.
We're exponentially growing on the back of finite resources that we are consuming without replenishing. That's a bubble. I don't know when it will pop, but it will. Question is what happens then, and will we have enough alternatives available to keep going or not?
On the counterpoint side:
Life faced a similar situation prior to the advent of photosynthesis. It was growing exponentially and consuming chemical resources that would have been depleted. Had photosynthesis not evolved in time, life would have likely mostly died out and retreated to small colonies around a few hydrothermal vents.
That might have been one of the first great filters. We seem to be past that one.
The comment you were responding to wasn't referring to the 1970s, it was referring to the repeated cries of Malthusian catastrophes dating back to Malthus himself. The unexpected technology mentioned was a 50-fold increase in agricultural productivity per person working in agriculture. Several times in the last several hundred years, similar patterns were pointed out. All of them were solved with technology they had no way of knowing about.
All of them have been solved so far by using more fossil fuels. It's nice to have a line of credit, but we know neither the limit nor the interest rate.
Thanks. I had seen that calculation before, but had forgotten about it. It is good to remember that we will eventually come up against limits from basic physics.
Though, to be a bit picky, showing that we can't indefinitely sustain our current trajectory is a different argument than saying a collapse is inevitable.
If that's provably a great filter, you must have proof that there is only a tiny percent chance that we will have fairly large changes to our energy and resource systems. Is that what you are claiming?
There is absolutely no guarantee of collapse. Per capita, people live cleaner year by year whether they make "ecologically sound" signalling choices or not. Within the last 50 years, this has been very profound.
It's too early to say, but my money's on population crashing first. 100 years ago, you could see nearly anyplace a large population at something approaching the Malthusian limit; that's much reduced now.
The sore spots are worse but there are fewer of them. And something like a Haiti is extremely path dependent - it takes several improbable events conspiring to make one; so they can be unmade.
Jared Diamond's "Collapse" pretty much convinced me he was not just wrong but flat and 100% wrong. Through his writing , I learned to not only disapprove of apocolyptic narrative but how to counter it.
I would not be surprised of there were big, resource-oriented wars on the horizon but I doubt that'll lead to collapse, and I attribute those more to things like monetary policy and the odious politics of debt than human nature in the raw. It's difficult to explain just how violently wrong-headed people were in the 20th Century to create the big disasters.
I'm not talking about cleanliness. That's a quality of life factor but ultimately it's not what's important. The important thing is supply, mostly of energy.
(It's also important to note that to a great extent the West has cleaned up its environment by outsourcing polluting industries to Asia, Africa, and South America.)
Last I checked we still got more than 80% of our energy from fossil fuels. That has changed very, very little in the past 50 years. My grandparents drove a gasoline car, my parents drove a gasoline car, and I drive a gasoline car, and the power grid where I live is powered by 60% natural gas and 15% coal. Where I grew up it was almost 100% coal, same as it was three generations ago.
We were supposed to be driving EVs powered by fusion reactors by now.
If you're rich you can buy solar panels and an EV and convince yourself there is no problem, but until that stuff falls geometrically in price to the point that it achieves mass adoption it's a luxury toy that will make no impact. Either that or the future will require that 90% of humanity be reduced to medieval subsistence-level poverty. That's not quite the collapse some have predicted, but I highly doubt that sort of neo-feudal civilization is going to go to the stars. So it counts for the Fermi Paradox. The universe may be filled with such small, limited, planet-bound intelligences.
I'm slightly encouraged by an apparent Moore's Law in solar, but storage is now the bottleneck. I'm also very cynical about technological advancement outside of IT and a few other narrow areas. I agree with Peter Thiel that basically all major technological advancement outside of computers and some biotech stopped around 1970. Cars, planes, power plants, etc. are all basically the same today as they were then.
Fusion isn't something that we can simply order. People are working on it. I'm far from even ... ignorance on the state of the art there, but my guess would be that investing more would probably not produce it any faster.
Cleanliness - basic control of waterborne disease, the level of schmutz from power, control of pernicious trash - is huge. Queen Victoria's husband Albert died of this sort of disease 150ish years ago. This is vanishingly rare now if it exists at all.
I don't buy "90% in medieval subsistence level poverty" because medieval subsistence level poverty doesn't scale. It went obsolete even with the potato as a base food crop in the early 19th Century - I'd accuse the Irish potato famine of ending anything remotely like it. If there's feudalism again, then it's because we can't organize ourselves in anything more efficient than that.
I can't say that some sort of Malthusian equilibrium is impossible, only that it seems unlikely. Historically, we had two notable examples in the 20th Century - the Ukrainian famine post the Bolshevik Revolution, and the Chinese Great Leap Forward. Both were, paradoxically, caused by belief systems grounded in Malthusian predictions. Now that's largely inductive predicting on my part, but we just know better now.
There's a heck of a lot of muddling through between going to the stars and a continuous Malthusian crisis. I'd say "going to the stars" has more than anything else failed to capture at least the popular imagination.
Maybe intelligent ife is the universe is in fact quite abundant, but having followed the trajectory we are on and exhausted all its natural resources that would support becoming extra-solar civilisations, they collapse back to simpler, less technological agrarian societies?
Another argument against the great filter, and one I'm surprised it's not considered more often, is the relativity of the space and time. We assume, long story short, that the colonization explosion is rare because we can't see it, but what if all that we can observe in terms of space and time is a incredibly "microscopic" slice compared to all that there is/has been/will be out there? The way I see it it looks like we've concluded water must be commonplace on earth, but then we act puzzled when we can't find a lake down the street and assume water must be rarer than we thought.
The terms we know in the Drake equation make it very difficult to say it is unlikely for intelligence to arise more than once. ~100 billion stars * ~100 billion galaxies in the observable universe. Exoplanet surveys seem to be suggesting at least one planet per star on average. In addition, chemical self replication seems to happen fairly easily given the right chemical conditions, which don't appear to require much more than liquid water.
Among other comments here, there is the question of why? Why does a civilization need to expand? Why should it? We can already see in our world where the birthrates start to decline in societies that have a certain level of technology and quality of live. When we reach a point where our whims are catered for and energy is cheap. Reproduction doesn't seem very cost effective.
It makes sense that we'd expect to observe civilizations that are good at growing and have in fact already grown, right? Same reason we observe animals with a strong sense of self-preservation. These hypothetical expanding civilizations might be awful or unnecessary by our standards but that doesn't change how memetic/biological/whatever selection processes generally work. This is why the Fermi Paradox is interesting in the first place!
Expansion can be due to a lot more than mere birthrates. First and foremost expansion will happen only when there is means to do so. And, 'means' can be driven by a combination of curiosity and necessity. On earth people have gone somewhere far off (migrated), because there was the place to go and the means to get there. In many cases that (migration) was the option over having to fight (or find some form of accommodation) within the local social & political system.
If this is why an intelligence can spread out on a planet, couldn't other intelligences (if they exist) spread out for similar reasons in the galaxy.
There is a review in the FT today of "The Future of Violence" a book in which the authors apparently (I haven't read it) assert that as technology improves the risk of a violent individual to society increases (because that person has more leverage).
This raises an interesting problem : to make it as a society may require a high level of dynamism and aggression. To cope as a society (as technology becomes more potent) passivity and sensitivity may be necessary. It may be that there is no balance, and that if you have enough vim to create a technical society you will reach a point where progress becomes impossible due to progress so far.
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[ 2.9 ms ] story [ 122 ms ] thread1) The more important observation is that everything we see is a wilderness of apparently natural origins and processes, not that we have apparently not been visited.
2) No hypothesis involving choice that leads to failure to carry out self-replicating colonization can explain (1). All it takes is one small group in one sufficiently advanced species. This rules out wolves, berserkers, relinquishment, self-destruction, and so on and so forth.
Clearly something is missing or incorrect in how the pieces of the various sciences fit together to explain what we see. Some of the best reading on the subject is speculation on what it is that we don't know or the relative odds on where the present consensus is incorrect.
This is why, if I invented antimatter production, I would absolutely demand that it not be used on Earth until it had been used to send hundreds of human-bearing seed ships to other solar systems. The risk is too great.
"No alien civilizations have substantially colonized our solar system or systems nearby. Thus among the billion trillion stars in our past universe, none has reached the level of technology and growth that we may soon reach."
While the article is in a way all about exploring that disconnect, it's a bit strange to find it written down so explicitly in the conclusion. We can ascribe a very high level of confidence to hypothesis that neither our own nor any of the directly neighboring star systems have been colonized. But to postulate that therefore the universe has not yet produced a civilization as technologically sophisticated as our own is still a non-sequitur, at least in my opinion. The article also makes a lot of assumptions (it has to!), some plausible, some seemingly arbitrary, which might in the end not be important factors at all. For example, any consideration about radio communication must be on very shaky grounds, in particular when charting the absence of it.
The reason why we're not seeing alien neighbors or predecessors (which would be "neighbors" in time), might well be a combination of factors. While we can exclude certain scenarios, such as a cloud of Von Neuman Probes eating the galaxy, it still leaves room for a lot of little factors that can change the galactic stage for us in a fundamental way - especially if they work in conjunction.
For example, the average duration of the technologically recognizable phase a civilization goes through may be smaller, and there may well be less of them than expected. In addition, willful avoidance or isolation may well play a role; the zoo hypothesis is an extreme example of this, but in a sparse cosmos the measures you have to undertake in order to isolate an emerging civilizations become less heroic.
It's also worth mentioning that we ourselves are not past the Filter by any means. In fact, as time progresses, it seems to become less likely we'll ever move off the Earth as an exclusive habitat. Part of this is due to psychology, we could have made it happen by now but didn't. The best bet at becoming an interstellar civilization right now seems to be to wait until we're pure computer systems, unburdened by aging and the passage of time, but that development, too, might end up being something we never elect to actually pursue.
Luckily, this whole thing is a mystery we can solve over time, just by gathering data about what's out there.
The timescale for megascale engineering to occur throughout our galaxy as the result of the launch of one megascale engineering minded self replicating probe is small (1 million years) in comparison to the age of the galaxy (13 billion years). It is unlikely that we are sitting here while someone else is in the process of doing it; that's not the scenario to focus on.
All it takes, remember, is one small group in one sufficiently advanced culture to start this going. Some (post)human group will clearly do it at some point if we as a species continue. Why hasn't someone already done it, where "it" is visibly engineer the totality of the future light cone?
The problem is less one of why don't we see Dyson spheres and other similar type II projects within a few hundred light years of our position, and more one of why do we see no obviously altered galaxies among the hundreds of thousands cataloged to date. At this scale the zoo hypothesis looks stretched, and the simulation argument begins to look more plausible.
A partial answer to the Fermi paradox by appeal to the anthropic principle: there is a very small fraction of time between being able to observe an alien species and being consumed by it.
The need for megascale projects is not as obvious as it's sometimes made out to be. There might well be reasonable limits beyond which the maximizing of habitat space and energy consumption tapers off in utility. Even if our civilization continues on its present course, it's not certain that we will get to the point where we (or some of us) feel the need to change the face of the galaxy. If you go one step down from the galactic stage, the detectability of solar system-scale megatech is also open to debate, especially as you move beyond a couple hundred light years from here.
You're right of course when you say all it takes is one civilization (or even one member of a sufficiently advanced society) to undertake projects that are liable to make all kinds of strange phenomena appear in our night sky. But the number if beings capable of doing so on a whim, multiplied by the chance they'd be interested in such things, might be very very small without breaking any of our current expectations about biology and physics.
Finally, I'd like to address the simulation argument. There are two extreme ends of the simulation scenario spectrum.
At the one extreme, we're talking about an artificial reality made especially for us, humans. This would be the popular "Matrix"-style simulation. No scientific argument I've heard so far makes it a convincing model for the reality we live in, except as a possible explanation for the Fermi paradox.
At the other end of the spectrum, we have a full simulated universe. It's hard to argue for or against that notion, simply because either way it fits with our observable reality. The catch is of course that it's a neutral proposition with no impact on us at all. This variant does not offer any explanation for the Fermi paradox.
As I see it, the simulation argument as pertinent to the Fermi problem offers two options, neither of which are intellectually appealing: one is a borderline-untenable just-so make-believe world where all rules are an illusion and anything can happen, and the other one is virtually undistinguishable from our "normal" world, up to and including an absence of any obvious explanation for the Fermi paradox.
Or the put it a bit different: unless the Culture want us to see it, we won't.
I mean there could easily be a couple 1000 years between us, which means that the difference is at least as great as us and the Romans. The Romans might very well question why we weren't breeding more horses then, since we have such a huge need of transport and horses are the best way to do that.
Consider the energy and material engineering necessary to achieve long-distance space transport of any sizable amount of people, equipment, and supplies. Regardless of whether the transport is subluminal or FTL, the energy requirements are tremendous and the engineering requirements for a durable vessel astounding.
My guess is that by the time our materials science and our energy production are up to the task, our interests may well have changed - because (and here I speculate wildly) science at engineering at that level will reveal so much about the fundamental nature of the universe and give us so much interesting practical technology that biochemical life clinging desperately to lucky rocks in the lucky zone won't be near so interesting anymore.
No one comes near because we have nothing to offer those able to come near and get home again to report what they found.
As to simply detecting signals, we have to consider how lucky we are to have so much ore so close to the surface: Metallurgy and eventually radiated communications were a natural for us.
Other civilizations may well start with fantastically engineered wood and eventually plastics, and go all-fibre, all line-of-sight, and have very, very different communications systems, systems undetectable at any remove.
For the sake of argument let’s linger on that assumption for a while. How for example did they found us when our civilization achieved radio signals transmission in the last couple of centuries? That means that they’re close by, unless FTL travel is feasible in which case we can safely assume the whole galaxy should be teeming with life. But if they’re close by shouldn’t we be able to spot them? And if they’re far away that means they should already have colonized half the galaxy before they decide to launch an expedition to a planet thousands of light years away.
The worrying factor relating to the “Fermi Paradox” is that it suggests that maybe life is extremely rare. We could very well be the only living souls in this part of the Universe and that’s kind of heart breaking considering the sheer size of the whole thing.
By the way, your assumption is called the "Zoo Hypothesis" http://en.wikipedia.org/wiki/Zoo_hypothesis
Oh, and while we're in this scenario I'd urge everyone to read the following SF short. http://www.terrybisson.com/page6/page6.html
1 and 2 don't make sense if you assume that there are many alien civilizations older and more advanced than us. 3 implies that we're fundamentally misunderstanding a lot about (astro)physics.
If space investment/exploration had continued in the 70s (with or without an Orion project) then by now, we would have lots of infrastructure outside the atmosphere.
I.e., a large subset of species around our level of industrial advancement ought to be close to "planetary breakout".
The point is, a Great Filter for intelligent species at our technology level would need to sterilize a whole solar system, not only on a planet. Otherwise it would miss, say, somewhere between one and ten percents of the civilizations.
So I'd guess we're past the filter.
Of course, possible filters that clean out a solar system do exist. Another species could soon wipe us out (any single galaxy just needs one early xenophobic and crazy species). Or e.g. unknown physics in a particle accelerator experiment will have very unexpected effects for the whole solar system, very soon...
Barring several fairly large changes to our energy and resource systems, our civilization is mathematically and physically guaranteed to collapse within the next 200 years at most.
That's not a hypothetical filter. It's a real one that we can see, and we are not past it.
The Great Filter is just the thing that explains most of why intelligent life is (or seems) so rare in the universe. It could be true, for example, that some cosmic event kills life before it becomes technological 99% of the time (= Great Filter), and also that, say, 60% of technological civilizations destroy themselves via destroying their environment.
(1) An intelligence reaches a critical intellectual mass and begins to utilize the free resources that are present in its environment.
(2) In doing so it grows and develops exponentially.
(3) By the time it develops far enough intellectually to realize the problem -- exponential growth built on finite non-replenishable supply -- it's already too late.
We seem to have realized this problem around 1950-1970, and we have done very little about it so far. That's because huge complex systems are hard to change, and all the incentives point the wrong way.
Few nonrenewable resources have a remaining supply measured in hundreds of years.
> Barring several fairly large changes to our energy and resource systems, our civilization is mathematically and physically guaranteed to collapse within the next 200 years at most.
Would you mind elaborating on this or posting some links with more evidence for this? As stated, your claim seems reminiscent to previous claims that humanity would soon not be able to grow enough food for the projected population. So far, unexpected scientific advances have managed to increase food yields substantially, and we can now effectively produce more than enough food to feed people (though we clearly have issues ensuring that food gets to everyone who needs it). So I wonder what is different now, that makes this looming catastrophe "provable" and "mathematically and physically guaranteed".
I agree that humanity is facing significant challenges (e.g., climate change), but I think the claim of "guaranteed collapse" is not as well established.
This is a cautionary tale about something that stock market traders know well: never try to call the top of a bubble. You'll just look like a fool, and if you bet on it you will lose all your money.
The "Population Bomb" crowd in the 70s and the peak oilers of today tried to do just that: to call the top. They were not wrong about the underlying realities, but they were absolutely wrong about the timing -- which is nearly always the case. Bubbles almost always go higher and further than anyone ever expects or imagines.
We're exponentially growing on the back of finite resources that we are consuming without replenishing. That's a bubble. I don't know when it will pop, but it will. Question is what happens then, and will we have enough alternatives available to keep going or not?
On the counterpoint side:
Life faced a similar situation prior to the advent of photosynthesis. It was growing exponentially and consuming chemical resources that would have been depleted. Had photosynthesis not evolved in time, life would have likely mostly died out and retreated to small colonies around a few hydrothermal vents.
That might have been one of the first great filters. We seem to be past that one.
I'm not the GP, but I suspect api has in mind something like this [0]. The money quote from that article is this:
"At that 2.3% growth rate, we would be using energy at a rate corresponding to the total solar input striking Earth in a little over 400 years."
The obvious first-order thermodynamic consequences of that fact for the temperature of the surface of the earth are pretty undeniable.
[0] http://physics.ucsd.edu/do-the-math/2012/04/economist-meets-...
Though, to be a bit picky, showing that we can't indefinitely sustain our current trajectory is a different argument than saying a collapse is inevitable.
It's too early to say, but my money's on population crashing first. 100 years ago, you could see nearly anyplace a large population at something approaching the Malthusian limit; that's much reduced now.
The sore spots are worse but there are fewer of them. And something like a Haiti is extremely path dependent - it takes several improbable events conspiring to make one; so they can be unmade.
Jared Diamond's "Collapse" pretty much convinced me he was not just wrong but flat and 100% wrong. Through his writing , I learned to not only disapprove of apocolyptic narrative but how to counter it.
I would not be surprised of there were big, resource-oriented wars on the horizon but I doubt that'll lead to collapse, and I attribute those more to things like monetary policy and the odious politics of debt than human nature in the raw. It's difficult to explain just how violently wrong-headed people were in the 20th Century to create the big disasters.
I'm not talking about cleanliness. That's a quality of life factor but ultimately it's not what's important. The important thing is supply, mostly of energy.
(It's also important to note that to a great extent the West has cleaned up its environment by outsourcing polluting industries to Asia, Africa, and South America.)
Last I checked we still got more than 80% of our energy from fossil fuels. That has changed very, very little in the past 50 years. My grandparents drove a gasoline car, my parents drove a gasoline car, and I drive a gasoline car, and the power grid where I live is powered by 60% natural gas and 15% coal. Where I grew up it was almost 100% coal, same as it was three generations ago.
We were supposed to be driving EVs powered by fusion reactors by now.
If you're rich you can buy solar panels and an EV and convince yourself there is no problem, but until that stuff falls geometrically in price to the point that it achieves mass adoption it's a luxury toy that will make no impact. Either that or the future will require that 90% of humanity be reduced to medieval subsistence-level poverty. That's not quite the collapse some have predicted, but I highly doubt that sort of neo-feudal civilization is going to go to the stars. So it counts for the Fermi Paradox. The universe may be filled with such small, limited, planet-bound intelligences.
I'm slightly encouraged by an apparent Moore's Law in solar, but storage is now the bottleneck. I'm also very cynical about technological advancement outside of IT and a few other narrow areas. I agree with Peter Thiel that basically all major technological advancement outside of computers and some biotech stopped around 1970. Cars, planes, power plants, etc. are all basically the same today as they were then.
Cleanliness - basic control of waterborne disease, the level of schmutz from power, control of pernicious trash - is huge. Queen Victoria's husband Albert died of this sort of disease 150ish years ago. This is vanishingly rare now if it exists at all.
I don't buy "90% in medieval subsistence level poverty" because medieval subsistence level poverty doesn't scale. It went obsolete even with the potato as a base food crop in the early 19th Century - I'd accuse the Irish potato famine of ending anything remotely like it. If there's feudalism again, then it's because we can't organize ourselves in anything more efficient than that.
I can't say that some sort of Malthusian equilibrium is impossible, only that it seems unlikely. Historically, we had two notable examples in the 20th Century - the Ukrainian famine post the Bolshevik Revolution, and the Chinese Great Leap Forward. Both were, paradoxically, caused by belief systems grounded in Malthusian predictions. Now that's largely inductive predicting on my part, but we just know better now.
There's a heck of a lot of muddling through between going to the stars and a continuous Malthusian crisis. I'd say "going to the stars" has more than anything else failed to capture at least the popular imagination.
Is it? How do we know it is?
Loosing this rock or our star essentially equals the extinction of our species.
If this is why an intelligence can spread out on a planet, couldn't other intelligences (if they exist) spread out for similar reasons in the galaxy.
This raises an interesting problem : to make it as a society may require a high level of dynamism and aggression. To cope as a society (as technology becomes more potent) passivity and sensitivity may be necessary. It may be that there is no balance, and that if you have enough vim to create a technical society you will reach a point where progress becomes impossible due to progress so far.