Some thoughts on the Fermi paradox

[WeepingElf]

Hallo!

I wish to share some thoughts on the Fermi paradox here. The question is basically, "If extraterrestrial civilizations exist, where are they? Why haven't they colonized us long ago?" I have repeatedly thought about this, and here are some points that occured to me.

1. Interstellar travel may be utterly infeasible. Space travel, we all know that, is expensive, and there is an awful lot of space to traverse to reach the next star. Estimations of the cost of an expedition to Alpha Centauri tend to yield figures that exceed the world's annual GDP by a few orders of magnitude; of course, more advanced civilizations will also be more prosperous (but to which extent? Planetary resources aren't infinite, and even with us, the ceiling is already in sight in some points). And that doesn't even take FTL travel into consideration. Some physicists say that things such as "wormholes" or "warp fields" were theoretically possible in this universe, but apart from knowing nothing about how to create them, we don't know whether they were actually useful - they seem to require immense amounts of energy, and the conditions inside them appear to be too extreme for a spacecraft to survive them.

2. Planetary biospheres are probably incompatible. There is little reason to assume that the kind of biochemistry we have here on Earth is the only one possible. So even if a group of settlers somehow manage to reach a habitable planet of a nearby star, they'll probably find that the local lifeforms are utterly inedible to them, and even crops they have brought along won't thrive in the alien soil. Thus, their colony would never become viable.

3. Terraforming probably won't work. A planetary biosphere is a very complex affair; we don't understand our own one enough to build one on another planet. (At least, Biosphere2 failed.) Of course, more advanced civilizations will understand theirs much better than we do. But there is a second problem with terraforming: Any inhospitable planet is inhospitable for some kind of reason, and most of these reasons (such as wrong distance from its sun, or insufficient mass to keep up a substantial atmosphere and magnetic field) should lie beyond what even a highly advanced civilization could fix. Hence, a colony on a previously lifeless planet won't become viable, either.

What do you think? Are these problems really so insurmountable? Or is my entire logic tarnished?

[Raphael]

Or is my entire logic tarnished?

No, sounds about right to me. My one issue is with your comment that Biosphere 2 failed. Yes, it did, but just because something failed in the past, it doesn't mean that it can't work in the future. If you search a bit on Youtube, you can find some pretty amusing videos of failed early attempts to build flying machines.

Another objection: what about self-replicating spacefaring machines?

[Pabappa]

the speed of light cannot be derived from any equation involving more fundamental concepts, so we shouldnt just assume that the c we know is the only one possible. If the speed of light is variable, all other problems will go away just from that.

That's the only theory that I can see that makes intergalactic travel feasible .... sure, wormholes might exist, but any society with the ability to construct a wormhole is probably capable of a lot of other things too and would have no need to seek out new planets unless it just was for fun ... in which case why bother making contact?

But yes, until we discover an equation that outputs the value of c from fundamental constants, i treat it like anything else, and we can only guess at whether it's a variable or a constant.

[zompist]

I think the biggest factor will be the maturity of possible spacefaring civilizations.

It took 4.5 billion years for one to develop here. (Insert many caveats about extrapolating from one instance.) The universe is 13.8 billion years old.

Just to narrow things down, let's assume that civilizations started appearing a billion years ago. Then spacefaring civilizations should be anywhere up to a billion years old. Now, you may think it takes forever for your computer to boot up, but a billion years is way longer than that.

Now, picture Civilization N, which has been around for, oh, 100 million years. They discovered Earth at some point, during the dinosaur era. Do they run in and conquer it?

Why would they bother? They are not conquistadors who need slave labor or silver or guano. A 100-million-year-old civilization is nearly unimaginable, but surely the worst way to imagine them is to extrapolate from the behavior of European nations from 1500 to 1950.

Once Earth developed an ecosphere, it was probably off limits as a nature preserve— and the nearby stars too.

[Raphael]

Why would they bother? They are not conquistadors who need slave labor or silver or guano. A 100-million-year-old civilization is nearly unimaginable, but surely the worst way to imagine them is to extrapolate from the behavior of European nations from 1500 to 1950.

Ideology. Religion. Material greed isn't the only powerful motivator in the universe.

[WeepingElf]

Thank you for your replies and objections. My initial post was not meant as a statement of facts; it was meant as a seed for discussion. Indeed, the Colonial Era is no good model for interstellar colonization, as none of my points apply to it: not only was intercontinental travel feasible even at the lower prosperity and technology level of those years, also, it all happened within a single planetary biosphere, so bio-incompatibility and terraforming were no issues.

But indeed, we can't say what civilizations millions of years ahead of us can do. That Biosphere2 failed just means that we can't do it now; a more advanced civilization will understand their biosphere better and may be able to replicate it. We also don't know how prosperous they can be; yet, it seems to me as if a planetary economy can't grow infinitely. The limits of growth can already be felt, regarding some resources, on Earth now. An optimistic estimate is perhaps an annual $100,000 per capita (about twice the level of the most prosperous countries now) with a population of 10 billion, which makes for an annual planetary GDP of $10¹⁵. So there will be an economic limit to what a planetary civilization can achieve. Of course, prosperity is not really a physical quantity...

But perhaps, it is the exact opposite, and possible (and feasible) colonization targets are so plentiful that we haven't been molested yet because there are more than enough better options elsewhere. After all, the presence of a technological civilization like ours on a planet is a valid reason not to try colonizing that planet! Space is big, after all.

[zompist]

Why would they bother? They are not conquistadors who need slave labor or silver or guano. A 100-million-year-old civilization is nearly unimaginable, but surely the worst way to imagine them is to extrapolate from the behavior of European nations from 1500 to 1950.

Ideology. Religion. Material greed isn't the only powerful motivator in the universe.

As a motivator for expansion, religion mostly just puts a warm blanket around naked power. The European colonialists, from all countries, talked about spreading Christianity, which is approximately precisely zero use in explaining their actions. What they actually did was grab resources, grab territory, grab slaves.

This isn't to say a religion can't be spread for non-material reasons; perhaps the best example is Buddhism. India got no material benefit from spreading its spirituality to China. (SE Asia is a more complicated case, as there was trade and at least some settlement. But it was still the locals who ultimately benefited from Indian ideas, including Hinduism this time.)

Personally, I don't think a civ can get much past our level of development without calming down quite a bit. Psychopathic civilizations will destroy themselves early. Dystopias are not more efficient, nor are they ruthlessly unstoppable.

[Raphael]

If you don't buy the idea of traditional religions as a replacement, rather than a cover, for material motivations, then how about something a bit more modern, such as Marxism? A major culture might be convinced that all societal models except its own are oppressive, and that it therefore has an obligation to "liberate" all lifeforms living under other societal models from their "oppression". (Since this thread is a part of the Conlangery forum, I'll point out that something like this might be a motivating factor for my own Péchkizhénk.)

Also, a lust for sheer power might extend beyond the amount of power that's really necessary to meet a group's material needs.

[Ares Land]

That's a very good subject for discuession.

On colonization: first, would an alien civilization need that much real estate? It seems that we humans tend to regulate population growth as soon as we get the means to do it. (to wit: the demographic transition).
Any civilization that has figured out interstellar travel has figured out a way to keep its population in check. (Unless magic dilithium crystals happen to be a thing, interstellar travel looks abysmally difficult and expensive. By the time a civilizations figures out a civilization, it has either gone extinct or figured out a way to be content with its own planet.)

That said, what if our aliens want that real estate anyway? Well, then, how about space habitats?
I've always been quite fascinated by the concept. The idea is to build large space stations (a few kilometers wide should do the trick) and live there. It sounds insane, but in fact, it's no worse than settling Mars or Venus. The thing is, a Mars colony would be a huge space station anyway. So why not build it directly in space, using asteroid material? That way you get 24/7 solar power, you can build close to Earth, take advantage of zero gravity, and you don't have to bother with the damn Martian dust.
In terms of resources, it's a sound strategy in the very long run : there's enough material for trillions of humans in the Solar System.

(Sure, it would be nice to settle a nice Earthlike planet instead... But, let's face it, interstellar travel would need huge revolutionary breakthroughs in science and technology, and is a problem that could possibly take millenia to solve... Whereas building a space habitat is just a matter of engineering.
My favourite pet peeve is the generation ship. Dude, if you can build a huge ship that could sustain a sizeable population for millennia... Why bother getting the ship to another planet? Just leave it parked in orbit and live there!)
And then, assuming our aliens have exhausted their own system or are unhappy with it for some reason, they just need to start building habitats in the next uninhabited system over. (Red dwarfs are probably great for this: not very suitable for the evolution of life, but very stable in the long term and full of material.)

Our nearest alien neighbours, assuming they're carbon-based and breathe oxygen at tall, very likely have a biochemistry incompatible with ours, and to prefer a different temperature range. So why bother with an uncomfortably cold/hot hellworld like Earth where everything is toxic.


Now, my own take on Fermi's paradox:

First, I don't believe Earth or humans are exceptional in any way. If life appeared on Earth, it probably appears whenever the conditions are right. Sentience certainly looks like a successful evolutionary strategy. Given the size of our galaxy, and a time span of several hundred million years... Yep, there definitely are intelligent aliens out there.
Regarding interstellar travel: well, the difficulty and the cost are unbelievable. And yet... a hundred years of science fiction have already produced a good amount of workarounds. Now imagine a few millions years of speculation! Of course civilizations have figured that one out.
It's not going to look like Star Trek of course, and in fact I have no idea what possible forms this could take. Starships running on pure technobabble? Mechanical replicators? Wormholes? Spores sent at very low velocity? Who knows? The point is, they exist and they have some mean of getting there, or at least of finding out what we're up to.

Perhaps, as it's been suggested, aliens just aren't interested. I don't think that's the case. We would be interested and why should human beings be exceptional in that respect? Besides, curiosity is a survival factor and probably a precondition for sentience.
Maybe some species are hermits by nature, but again, given a scale of a few hundred million years and the size of the galaxy, there must be some that are interested.

So why don't they show up?

a) They already did. Except it was thousands of years ago, or millions of years ago, or they just were prudent enough to not let themselves be seen. In any case, I think likely, myself, that either us or our ancestors have featured in the local equivalent of National Geographic somewhere in the galaxy.
b) They just haven't gotten around to it. Which is possible. Given some values of the Drake equation, maybe there just are three or four species able and willing to visit us, and given the sheer size of the galaxy, they just haven't found the time to do so.

More dire explanations:
c) Civilizations inevitably end up destroying themselves, as soon as they figure out nuclear power, fossil fuels, conspiracy theories or internet porn. I suspect that's just moral panic. Even assuming a 15° increase in temperatures, several global pandemics and large scale thermonuclear war, there'd be survivors at the North Pole or something ready to take over civilization more or less where we left it.
d) The Dark Forest Hypothesis. The argument goes, it's trivially easy to destroy a civilization at interstellar range. (Hurl a relativistic projectile at the exoplanet of your choice) Besides, civilizations tend to destroy each other as soon as they hear about them, just in case the other side shoots first. The end result is that everyone in the Galaxy lies low, terrified to be found out and destroyed by their neighbours. Now I can't really disprove the Dark Forest Hypothesis. But I don't think that paranoia is conducive to long term survival of a species, and if you can hurl an asteroid at 99% c to kill your neighbours, you can figure out a prisoner's dilemma.

Ideology. Religion. Material greed isn't the only powerful motivator in the universe.

Good point. As we've seen, material greed is out, but how about ideology?
Some ideas:
a) Maybe ideology and religion don't cross the species barrier very well. For instance, how would an eusocial species react to Christianity? 'Love thy neighbour as thyself' is as natural as breathing, and they understand very well the idea of the sacrifice of a single individual for the salvation of many: they call it 'Tuesday'. Likewise, many awkward moment when the bug-eyed preacher goes on and on about the virtue of polygyny and the importance of not eating reproducing male before they had a chance to mate.
b) Aliens figure out that imposing ideologies and religions by force just plain doesn't work. That may be optimistic, on the other hand, after millenia or millions of years of going through the equivalent of the Iraq War, you probably figure some things out.
c) Same as before, and just like in a Culture novel, they figure out that it's better to influence ideology covertly. We're already part of the Galactic empire; we just don't know it yet and through the discreet actions of alien agents in a couple of millenia we'll all be proud pyramid-going Zorgists.
d) The Lovecraftian hypothesis: the aliens are temporarily occupied elsewhere, their ideology is utterly beyond good and evil, and they don't terribly care about humans. Give it a few million years and humanity will be destroyed in a routine pest control.


My own theory on the subject: aliens exist, they're not interested in our resources. They observe us but they're not terribly interested in contact, and when they do contact us we don't understand much of what's going on. Our relationship with the alien observers that show up every million year or so is akin to that between Jane Goodall and the chimpanzees, or even an anthropologist and an ant colony.
Or (and I think that's very likely), there's a note on us that reads, basically 'Species #4899323, very bland proto-sentient species, follows all the classic patterns, check again in ten millions years in case
they come up with anything interesting.")

[zompist]

Ares Land's point about space habitats is very good. A few sf writers have realized this too, notably Iain Banks, whose Culture mostly lives on space habitats. Charles Stross likes to write about humans converting the entire non-stellar mass of the solar system into computronium, though he's not too good at explaining why we'd bother.

The "aliens with Marxism" thing has been done too— see Banks again, or Stapledon's Star Maker, which I reviewed here. Stapledon posits that each civ works out a utopia— but there's a shitload of trouble when some of the utopias try to convert all the others.

Note that "what makes good SF" is a very different question than "what's happening in our universe"! There's nothing wrong with writing space opera if you like.

The Fermi problem with Earth isn't, I believe, that we have a sentient species; it's that we have an ecosphere. I think the "hands off" signs went up 400 million years ago. Messing with ecospheres is surely one of the first things a long-lasting species learns not to do, both for practical and moral reasons. (How much study is required before an alien ecosphere is determined to be quite safe? I don't buy the Star Trek "wave a tricorder around for five seconds" methodology.)

[sasasha]

I do love Iain Banks, but my personal fave Fermi explanations are more down the line of The Matrix: either civilizations get so absorbed in their internal simulated universes that their only use for the material universe is to provide the power to keep the servers running; or this universe is an ironically geocentric simulation simulated only so carefully as to make it look like it should be filled with aliens.

These are only my faves in the sense that I personally believe they're more likely than the more corporeal theories, because I think the ability to create realistic (hyperrealistic, even) simulated universes is a logical extrapolation of sentient creativity, exponential technological wizardry, and the kind of profound boredom and ennui that could only come from artificially extremely lengthened life-spans or recyclable consciousnesses. Either someone's already done it (and we're in it), or everyone else is busy doing it - or both.

Space opera is more fun, I know. But I think once it becomes true that every feature of your civilization can go virtual to bespoke specifications, and undergo every possible type of optimization - including having all kinds of fun aliens to play with, if that's what you want - it's inevitably going to happen. What need have they then for us or our measly analog planet? We're more likely to feature in their entertainment than in their political, military or economic activites.

Of course, there's probably a fair bit of time separating the onset of the space-age and the ability to realistically simulate universes, in which advanced civilizations might come across each other. But, our universe is not just big. It's fricking enormous. I wouldn't be surprised if the chances of coterminous civilizations ever bumping up against each other were boringly close to zero. And if they did, I would expect the "nature reserve" or "subconsciously assimilate" approaches to be selected in all but the most unbelievably extreme scenarios.

[WeepingElf]

Good points. Why take the trouble travelling to a faraway planet, which will not offer ideal conditions anyway, if you can build space habitats closer to home at a fraction of the cost? And why take the trouble building space habitats, which need moving large amounts of raw materials, if you can set up a virtual dream world, again at a fraction of the cost? MMORPG addiction is already a social problem now. Of course, the latter still requires someplace to put your bodies, but perhaps mind uploading works at a sufficient level of technology, so this last problem falls by the wayside, too.

And finally, any sufficiently advanced civilization will have learned to limit population growth, use the limited resources of their home world in a sustainable way such that they never run out, and live with each other in peace, because otherwise they wouldn't be so advanced. So the pressure to take land elsewhere will approach zero. They'd of course still be curious because otherwise they won't have science and technology, so they'd at least send probes anywhere they can, but that doesn't mean that they will try settling there, especially if the problems I mentioned in my opening post actually exist. (Tourism will still be a motivation for travelling, but even that can be satisfied by virtual enviroments based on the data from the probes.)

[Pabappa]

Good points all but it makes me smile to see people here telling alien societies that unchcked population growth is harmful as if we know more than they do. We are like dogs chained in the yard, knowing very well how things work in our own little world, but unaware and incapable of understanding what goes on beyond our sight. We bark whenever a car comes by because we know that they're out to get us and that's why we're so proud of ourselves when the car drives off without causing us any harm.

Im sure there's been at least 99999999 comic strips and cartoons about small children where they talk amongst each other and are proud of themselves for figuring out some basic fundamental concept of the adult world, blissfully unaware that adults follow totally different rules. If not, we dont need cartoons because it happens in real life .... I knew a young girl whose parents both worked outside the home, and i realized later on that she assumed I had a job like theirs, just because I had a job. Yet her understanding of both her parents' jobs and my own was comically naive, as she had never seen an office and pictured it as being much like a preschool where people get to play around and do fingerpainting. Alas, it was not to be.

[WeepingElf]

The fun with the Fermi paradox is that there are so many solutions to it that not all can be true but each of them suffices to explain why they aren't here yet It is rather that quite a few assumptions must be met for alien intelligences to colonize us, including some quite unlikely ones - if just one of them is false, they don't.

[zompist]

We are like dogs chained in the yard, knowing very well how things work in our own little world, but unaware and incapable of understanding what goes on beyond our sight.

Yes, of course. That's one reason I find, as I said, sf writers' speculations about post-Singularity entities unconvincing. As a narrative device, when you posit beings who are fundamentally inscrutable, then they no longer work as narrative devices.

Still, though all of our guesses are wild extrapolations, I think it's useful to recognize what we're extrapolating. E.g. Lovecraft's gibbering horrors are just extrapolating our more unpleasant natural experiences. It's not a law of the universe that unpleasant things are more likely to be true.

The whole point about the Fermi paradox is that we do have one data point. This planet hasn't been colonized by omnipresent slavering alien imperialists over the last hundred million years. We can't be confident of any conclusion we draw from this. But it does suggest that they're not so omnipresent or not so slavering as we fear.

[Moose-tache]

Let's say the Earth's annual consumption doubles every ten years, and colonizing another planet will double our available resources. That would mean that colonization only buys us ten years before we're in the same predicament, but twice. So I think it's fair to say that any civilization that has survived for millions of years has long since learned to be self-sufficient, or at least develop beyond the model of constant expansion of resources. So the lack of alien conquistadors doesn't exactly cry out for explanation. Wonder why aliens haven't taken our Neodymium yet is like cavemen watching a transaction at the bank and wondering why the customers don't just club the teller and take all the square leaves for themselves to eat later. I always marvel at sf aliens who can travel faster than light but can't make do with the resources in their own solar system.

Also, since it's been mentioned, Biosphere 2 only "failed" because they made a stupid mistake of not including their farm in their calculations. The "natural" part was in careful equilibrium, but nobody bothered to hire a soil scientist to look at their farm. To maximize yield they stuffed the ground full of fertilizer; they were basically farming in compost. So of course it started outgassing. The carbon merged with the free oxygen, got absorbed by water and concrete, and thus trapped the oxygen they needed for breathing. The only thing they needed to do differently was let the science team in charge of planning the ecosystem inside the dome spend five seconds looking at their farm, and the whole thing would have gone differently. This is not a mistake anyone will make again, especially since astro-colonists are unlikely to consider their farm plot outside the natural ecosystem.

[Raphael]

Regarding the point some have made about how aliens might already know about us and have chosen not to make contact yet, I'm reminded of Justin B. Rye's point that, the fewer sentient species there are in the known universe, the more talking to us becomes a rare opportunity, and the more sentient species there are, the more independent actors must be convinced or forced to follow the same policy of not talking to us.

[zompist]

Regarding the point some have made about how aliens might already know about us and have chosen not to make contact yet, I'm reminded of Justin B. Rye's point that, the fewer sentient species there are in the known universe, the more talking to us becomes a rare opportunity, and the more sentient species there are, the more independent actors must be convinced or forced to follow the same policy of not talking to us.

I think that assumes that all those species are independent actors-- that is, that they are all at similar stages of development. That seems impossible; sentient species should range from thousands to billions of years. I don't think it takes long to learn "What the billion-year-old species says, you listen to."

(Again, the caveat applies that we just don't know. But "a bunch of species of equal level" requires making some very strained assumptions, like sentient species all dying off young. It seems more parsimonious to assume a wide variety of ages.)

One thing we haven't discussed much is the possibility that sentient species are actually pretty rare. There are some astrophysical reasons to suppose this: bright stars burn out too fast; red stars may not have stable planets. If the nearest nice planet is 50 light years away rather than 5, colonization is even more of an unlikely project. It doesn't make for very exciting sf though...)

[WeepingElf]

Regarding the point some have made about how aliens might already know about us and have chosen not to make contact yet, I'm reminded of Justin B. Rye's point that, the fewer sentient species there are in the known universe, the more talking to us becomes a rare opportunity, and the more sentient species there are, the more independent actors must be convinced or forced to follow the same policy of not talking to us.

I think that assumes that all those species are independent actors-- that is, that they are all at similar stages of development. That seems impossible; sentient species should range from thousands to billions of years. I don't think it takes long to learn "What the billion-year-old species says, you listen to."

(Again, the caveat applies that we just don't know. But "a bunch of species of equal level" requires making some very strained assumptions, like sentient species all dying off young. It seems more parsimonious to assume a wide variety of ages.)

Yes - this is an issue neglected by most SF authors. Different sapient species will have hugely different ages. Of course, there may be factors that limit the lifetime of such species, such as very old species either degenerating (perhaps due to complacency when they have achieved everything they could) or "transcending" to something utterly unfathomable to younger species.

One thing we haven't discussed much is the possibility that sentient species are actually pretty rare. There are some astrophysical reasons to suppose this: bright stars burn out too fast; red stars may not have stable planets. If the nearest nice planet is 50 light years away rather than 5, colonization is even more of an unlikely project. It doesn't make for very exciting sf though...)

Perhaps habitable planets are common but sapient species are rare. Earth hadn't had a sapient species for most of the time, and our existence seems to depend on quite a few coincidences. Also, if the lifetime of sapient species is limited (as suggested above), there will be quite a few planets who have had their sapient species, but don't have one now.

It seems, though, as if a sapient species that masters interstellar travel will have learned before that how to limit their growth, in both biological and economic senses, thus eliminating the need to take other planets under their plough. Or if they don't manage to limit their growth, they'll collapse before they ever attain mastership of interstellar travel. Just look at us: we already know how to limit our growth, it just lacks political and economic will to do so, while interstellar travel appears to require breakthroughs in science that are not foreseeable now. Interstellar travel is thus harder than living sustainably on a single planet, so you (fortunately) won't get interstellar locust plagues moving from one exhausted planet to the next.

[Pabappa]

humans, dolphins, elephants and some bird species are all arguably sapient, and dolphins may be more intelligent than we are since they can mimic our languages but we can't mimic theirs. We got lucky in that we evolved both high intelligence and a body type suitable for handling tools. It may well be, in fact, that it's harder to evolve hands than to evolve high intelligence. but elephants can grasp tools with their trunks, so it's possible that any animal that evolves intelligence will at least do what it can with the anatomy it has. dolphins are out of luck since they live in the worst possible environment for any species that wants to modify its environment.

this is an idea that has probably come up before in science fiction but Im making it up independently:
Imagine a planet where the most intelligent form of life is some seal-shaped animal with no mobility, barely able to move around on land, and is symbiotic with a relatively stupid but more agile form of life where each is dependent on the other. in a sense thats humans & dogs, but exaggerated ... if humans did not have hands to build weapons, we'd need some strong animal like a dog just to get us the food we need.