Eleven weird solutions to the Fermi paradox?

In my group at least half of these don’t count as weird at all.  Yet I had never thought of this one, “They’re All Hanging Out At the Edge of the Galaxy”:

This interesting solution to the Fermi Paradox was posited by Milan M. Ćirković and Robert Bradbury.

“We suggest that the outer regions of the Galactic disk are the most likely locations for advanced SETI targets,” they wrote. The reason for this is that sophisticated intelligent communities will tend to migrate outward through the Galaxy as their capacities of information-processing increase. Why? Because machine-based civilizations, with their massive supercomputers, will have huge problems managing their heat waste. They’ll have to set up camp where it’s super cool. And the outer rim of the Galaxy is exactly that.

Subsequently, there may be a different galactic habitable zone for post-Singularity ETIs than for meat-based life. By consequence, advanced ETIs have no interest in exploring the bio-friendly habitable zone. Which means we’re looking for ET in the wrong place. Interestingly, Stephen Wolfram once told me that heat-free computing will someday be possible, so he doesn’t think this is a plausible solution to the Fermi Paradox.

Once again, air conditioning really does influence location, at least if this is true (which I doubt).  The other ten are here, and the pointer is from George Dvorsky.


And evolutionary psychology gets accused of just-so stories!


At least these stories can be falsified. Someday. Maybe.

Given that the galaxy is a thin disc, wouldn't this theory suggest that life looking for the coolest region would simply go "up" or "down" on the axis of rotation of the galaxy? As in, centred but just "above" or "below" the core stars?

Perhaps the post-singularity ETIs would form two half-spheres, above and below the galaxies' core.

Sort of by the same reasoning shouldn't elephants have all migrated to the Arctic......

They did... Never heard of the woolly mammoth?

I never understand why we see so many complex explanations for the Fermi Paradox, when it could just be that A)interstellar travel is extremely difficult, B)tool-using intelligent civilizations are extremely rare, C)civilizations did come through earlier, it's just that we either didn't exist or were too primitive to monitor them, or D)all three.

Seriously, the fastest proposed starship that could theoretically be built with existing technology is Orion, and that gets you up to 3-5% of the speed of light at most assuming you want to actually slow down. And when I say "existing technology", I mean "a gigantic kilometers' wide pusher plate that would have to be assembled in space, along with a mobile nuclear bomb re-processing facility and your actual payload", so take it with a grain of salt.

And the worse thing is that the slower you go, the greater your danger of having a serious technical break-down in transit. So you either need to build starships that can last for centuries or millenia in interstellar space without any maintenance except from what they carry, or spend colossal amounts of energy to accelerate a ship faster (assuming it's possible technically).

The usual Fermi Paradox boils down to Von Neumann probes + a whole ton of time. Those aren't influenced by rarity of civilization, how far ago they existed, or interstellar travel taking a while.

It's more complicated than that. It's influenced by

1. Whether it's possible to actually build self-replicating probes capable of interstellar travel.
2. Whether those probes can survive long enough in transit to reach destinations where they can self-replicate
3. How far apart these civilizations sending them are
4. How much "impact" the probes have when they reach a solar system.

Just look at #4. If one of these probes passed through the solar system 50 million years ago, we'd never be the wiser.

How does that faster than light spaceship proposed by that Mexican physicist alter your calculations, Brett?

Warp Drive? It's almost certainly impossible. It requires "negative mass-energy", which can theoretically exist (nothing in the mathematics is against it), but which hasn't been observed except possibly in extremely short-lived particles coming out of black holes, and a tiny amount of negative pressure between two metal plates held very closely together (the Casimir Effect).

In case anyone was wondering, the Whack-a-Mole Hypothesis was named by yours truly.

Nobody was, thanks.

Nominated for the "Gratuitous Meanness Award"

Klaatu has been refuting these claims for years and years.

That's actually pretty cool, EY.

I don't really understand why it is a paradox. Maybe there are other potential civilizations, but we are the most advanced. The unconditional probability for this is infinitesimally small, but these are just priors. As each test we pursue reveals no contact, we should update our priors towards the belief that those unlikely explanations are more probable. So, maybe every other civilization is just not as advanced as us.

This should explain why it's a paradox:


The obvious solution is that interstellar travel is actually really difficult, even for civilizations with much higher technologies. E.g. the universe does not allow FTL or free energy or any such thing.

The whole premise of the Fermi Paradox is/allows slower-than-light travel.

Even with really slow-boating technologies, exponential colonization/spread could occur in galaxies.
You'd have to argue that it is so difficult that it isn't possible at all, not just exclude FTL.

ou’d have to argue that it is so difficult that it isn’t possible at all, not just exclude FTL.

I think that conjecture is invalid. It could be so resource intensive and take so long that it's very rare. Conjecture a slow boat that can drop off two sentient beings (will label them Adam and Eve) and it takes on average 100K years for the newly arrived pair to generate a civilization that can afford to send off another slow boat. Also, assume the average slow boat has a maximum range of 10 Light years. That's 10K per Light Year for the traveling wave front. Starting at one edge of a galaxy which is 100,000 LY's across it would take such a civilization 1 billion years to reach the other side of the galaxy assuming they encountered at least one inhabitable system every 10 Light years. That's only for travel within the galaxy. Travel or even communication between galaxies would be substantially more difficult.

Space is very big.

Von Neumann probes, not Adam and Eve.

They're just as speculative as interstellar travel.

A billion years is not a long time. Life on Earth is about 4 Ga old. The Sun is a bit older but the first stars on the Milky Way might have appeared as early as 15 Ga ago. Using your model, more than nough time to seed up the galaxy with probes 10 times over.

Compared with the time scale and the sheer number of stars, space is very small.

Von Neumann probes, not Adam and Eve.

Ok. But that doesn't really change the point. Von Neumann probes are self replicating, just like sentient beings. The conjecture was that the process can be possible but still time intensive enough that it fits the time scales involved. Calling them Von Neummann probes doesn't make the process less inherently difficult.

Using your model, more than nough time to seed up the galaxy with probes 10 times over.

Sure theoretically. At maximum possible rates, but we don't know any of the relative factors. How do you know when the process would have started? And yes life appeared on Earth billions of years ago, but algae doesn't build star ships.

The only facts we have to go on is the size of space (very big), the theoretical limits of space travel (relatively slow) and the known minimum time to create a technological civilization (that's us and it's about 5 billion years after the formation of the Earth). You can speculate that it should happen much faster, but you have absolutely no evidence to support your speculation.

Africans don't build starships and can't maintain modern civilizations. Look at inner-city slums in the United States and cities in Africa. Only a small percentage of the non-African people possess the intelligence to engineer high-technology. Intelligence is rare.

Apparently intelligence is so rare that even the comment section on economist Tyler Cowen's blog attracts imbeciles.

HBD detracts not a whit from the Fermi Paradox because it's premised upon intelligence and technological civilizations being exceedingly rare.

Similar to the Whack-a-Mole hypothesis, I read of one called (seriously!) the Mass Effect Hypothesis. Based on the video game, you see. A collection of Doomsday machines disguises its presence and every so often culls the nascent ETIs that are roaming the Galaxy for obscure reasons.

Upon further review, I must agree with Stan at 3:34 .

That is the same as the berserker hypothesis, I believe.

The reason intelligent aliens don't drop in too often is that the last one to do so was nailed to a cross.

Did you get that from Arthur C. Clarke?

That would be Douglas Adams.

All of these solutions are defeated by the scale of the universe. For example, even if nearly all civs decamp to the suburbs it doesn't make sense that they all do. It is the absolute lack of ANY sign that makes up the paradox. No, the simplest probability is that we just don't evolve into a star spanning civilization. We burn brightly and then [use up all our resources/kill ourselves off with WMDs/get snuffed by some environmental danger we don't know about yet/fill in the blank] and that happens inevitably to civilizations.

It just turns out that advanced civilizations contain the seed for their own distraction. We see the dangers all around....sooner or later one of them gets us.

It seems to be that in general people don't face up to the paradox. It is like the question that was raised about stars; why isn't the night white with their light if the universe is infinite? The answer is...it isn't. The answer to the question of where the aliens are is...there are no aliens to speak of. Clearly what aliens there are live the same existence we do. That is to say, civilizations live a relatively short lifetime huddled around a single star.

Or to put it another way, the sieve is still in the future.

Making some pretty large assumptions about alien psychology/size of the mindspace there.

why isn’t the night white with their light if the universe is infinite?

It is, however the light has redshifted, due to an expanding universe, into the infrared and as a result we can't see it with the naked eye.

Wait, so "we don't see any aliens because they all move out to the galactic suburbs", is implausible because it only take a tiny fraction non-suburbanite aliev civilizations to wreck the hypothesis. But, "we don't see any aliens because they all self-destruct very quickly on a cosmic timescale", is somehow plausible in spite of the fact that it would only take a tiny fraction of non-suicidal alien civilizations to wreck the hypothesis.

All of these solutions are indeed defeated by the scale of the universe. Including yours.

This is something that I wrote years ago, later learning that it's been explored in sci-fi literature. It seems strange to leave it out if you're compiling a long list. (pasted from Slashdot)

The fact that we haven't detected advanced life in all of our SETI searching, and the fact that our solar system has not been visited by an alien probe is some evidence that our galaxy has a "sterilizer civilization" - which is a pretty straightforward concept.

If two civilizations begin interstellar colonization in our galaxy, their spheres of expansion are bound to intersect in the future. As they will largely be competing for the same resources (sources of energy differential), some sort of conflict is inevitable. But a conflict at this scale would be so horrible that any reasonable civilization would want to avoid it at all costs. This reasoning makes me think that any suitably advanced, reasonable civilization will be a sterilizer civilization: For the moral purpose of preventing great suffering, they will sterilize any technological civilization before they begin their interstellar colonization. Being rational, they will do this in the most efficient way possible: They will send a robotic probe which will duplicate itself in our solar system, and this autonomous army will wipe out all technological life and monitor our system to make sure that none re-emerges. Since sending even a small payload at great interstellar distances requires great energy, the rational sterilizer civilization will choose a speed for the probe that will bring it to its target safely before their interstellar colonization phase begins, but not much earlier. It is quite possible that such a probe is on its way to us right now, but won't arrive for another thousand years.

So how should we react if there is a sterilizing probe on its way to get us? We have to begin our interstellar colonization before the probe gets here. I don't think it makes much sense to try to raise up a defense, because we can't even guess at the mechanism of such a probe. One thing it might do is to create a tiny black hole and drop it into the sun. (Or perhaps the probe just is a small black hole set to collide with the sun.) At this point, we are still a very vulnerable civilization, and will remain so until we have covered a substantial part of the galaxy. Also, we should be working hard on the technology for an effective sterilizer probe, just in case SETI does eventually reveal an alien civilization. I know it's "no fun" to kill aliens before we ever meet them, but the ethical costs of not doing so might turn out to be unacceptable.

You need to contact Paul Krugman.

I still like Tyler's "ETIs are functionally autistic" theory. The supposition that we should have encountered an ETI's signal by now relies on two premises, whereas it's normally stated as only relying on one. ETI's would require the means, yes, but also the motivation. There's no reason to think other intelligences have the same social-bent as us, and even if they start out as extroverts perhaps it means the singularity and mind emulation will result in total insularity, as we all fuck about in our simulated realities and quasi-pleasure machines.

The Great Silence was long ago rebroadened to 'or observe signs of their presence'. Think about how much humans have already put their stamp on the world, from atmospheric gas concentrations to permanent changes in radioisotope signatures to mass extinction events to radio emissions; now scale up to a galaxy wide civilization. We should observe *something* - stars occluded by non-gases, unstable configurations, supernovae where that should be utterly impossible, who knows? We don't see anything.

Regardless of whether they're 'autistic' and refuse to communicate.

I vote for #7.

The most likely explanation is that the percentage chance of technological civilizations evolving and enduring is less likely than we imagine. So we are the first (or close to the first) in this Galaxy. After all, there are 100 Billion+ galaxies. It's quite possible a lot of the other galaxies are teeming with sentient star cruising civilizations, engaged in valiant battles to save the Republic. ;)

It's certainly possible. Look at the Earth- there's been a grand total of one technologically advanced civilization capable of spaceflight in its 4.6 billion years that evolved out of its entire biosphere. And it's not clear how "heavily" we're going to expand into space.

I guess we could be the first. Somebody has to be, after all.

Am I the only one who finds the whole premise that advanced civilizations will still be relying on monstrously heat-emitting supercomputers odd?

Also, even if there are new frontier-seeking colonies undergoing exploration, won't *some* of the rest of the population stay back at home - wherever home is?

It's not as if our landing on the moon required that all mankind go.

Global warming, feh. Galactic warming credits.

Purely in the interest of speculation, I proffer solution 5A. or 5.1: the Solipsist Solution.

Proponents of the "simulation solution" heretofore have argued that the purpose is to generate a civilization or some global enterprise capable of or intent upon "mastering the Universe". Alternatively: if the Whomever responsible for generating the simulation has the functional equivalent of infinity at his disposal, the simulation can be run (whether sequentially or simultaneously being almost entirely beside the point) for EACH INDIVIDUAL OBSERVER WITHIN THE SIMULATION. Any observer can be placed into any locality, any "contemporaneity". Each observer apparently has some assessment or some determination to make, although to what end is not given to any observer to "know". Each observer's "contemporaries" offer alternative perspectives, but the entire simulation is run for only one observer at a time. Id est and e.g.: what the Planck anisotropy probe is now revealing about the composition of this "known" universe is data for only one person's consumption right now, whichever one of us that could be.

Obviously, this could also be an adjunct to the Directed Panspermia idea.

Couple of points, some already raised:

(1) The 2001 A Space Odyssey hypothesis, that advanced civilizations already have visited earth but put up a burglar alarm around the perimeter of earth until such time we become more advanced and set off the alarm, and,

(2) the proof in the Christian Bible, that indeed extraterrestrial life exists. Unless you believe, literally, that JC is talking about preaching to sheep (Baa!). That passage is: John 10:16 - "I have other sheep that are not of this sheep pen. I must bring them also. They too will listen to my voice, and there shall be one flock and one shepherd". It's also possible that this is talking about civilizations outside Judea, but the more romantic version is that it's referring to other planets.

No no no, that's rubbish! The proof is the first chapter of Ezekiel, dummy!

Surely it would be proof of the extraterrestrial life if JC was literally talking to sheep? It only makes sense to assume He is sort of human if we assume the sheep are meant metaphorically. If He meant it literally, then, well, at some point, He will be back for the Big Round Up and Short Truck Journey that ends in Judgement. And sausages.

I like the obvious explanation ""I agree one hundred percent. What's there to say? 'Hello, meat. How's it going?'"

#2 requires accepting the Bible's claims about Jesus (because how would he know about aliens otherwise), and yet still thinking there is a Fermi's paradox. The Bible is premised on the idea that life does not just evolve spontaneously, which kind of makes the paradox go away.

The aliens are engaged in a vast war of all against all, with concomitant radio silence and blackouts. The distances over the battlefield give great advantage to tactical defense, making the war perpetual. Peace is impossible because the necessary modicum of trust is inter-specifically unattainable. Centuries ago, a battle squadron passed this way and left us as a pyramid-obsessed cargo cult. A few smugglers and outlaws still visit us, but understandably keep a low profile.

David Weber's take on that concept is quite interesting: http://en.wikipedia.org/wiki/Mutineers%27_Moon

I think Wittgenstein identified the problem, " If a lion could talk, we would not understand him." On earth, we have trouble understanding other H. saps and speak poorly to dogs, elephants, and the most intelligent bioforms on our planet, the cetaceans. The silicon-fluoride lifeforms of Aldebaran are sending out telepathic messages, but there are no receivers here. The carbon based forms of Fomalhaut are sending their messages at such a high speed that we mistake them for noise. The thought concepts of the Emperire of Andromeda are expressed in nontranscendental numbers that no human can understand. Etc.

Perhaps this is a restatement of the paradox: It is impossible for humans to perceive that of which we cannot conceive.

Most people seem be proposing technological limitations, thinking in far mode (although most of the universe is pretty far.) We have plenty of historical evidence to suppose that this is a political problem. In the Ming Dynasty, Zheng He's ships were more than capable of exploration further and further afield. However the need for funds for domestic defense took greater precedent and exploration was cancelled. (The fact that he had political enemies didn't help but that is perhaps incidental.) If we look at the U.S. in the modern day, our ability to travel into space has actually decreased, again as a matter of political will and allocation of funds. Anyway you slice it there is going to be a scarcity of resources. Even a civ of disembodied consciousnesses may demand MORE ENERGY FOR WIREHEADING NOW. And some coalition that puts resources towards exploration will find themselves poorer with regards to political or military defense, allowing anti-exploration coalitions to take over.

One objection to this is that it only takes the creation of one von Neumann probe for the universe to be explored. While Columbus was turned down several times he eventually found one European state to support his exploration. However, if one civilization starts exploration and is partially successful in increasing the size of its shell, they essentially turn into a new large imperial China; this means there are less "European" smaller civilizations, and as political will is centralized we have fewer independent chances of success. And depending on the future cost of capital, and these sapients discount rates, and the speed in which von Neumann probes create value, this new "Chinese" civ that holds sway over some region may decide it is better to bring the probes back and scrap them for whatever reason, as our politicians have done. And before you object that that technological progress will have made these probes cheap/free/value creating, technological progress may also have made the alternative uses even more productive.

So maybe the Fermi Paradox is solved by some horribly depressing universal law of political/economic capture that happens to all sufficiently advanced civilizations/sentiences.

Even launching a single "probe" at a decent interstellar speed is going to require enormous energy - look at the Orion Project. It's quite possible that most civilizations just don't bother to commit that much energy and resources to sending probes beyond the nearest stars, if at all.

Plus, if you want to explore space, being good at interplanetary-level space travel means you can probably build some incredibly awesome arrays of space telescopes.

History is not on your side in this example, because Columbus's discovery sparked a competitive frenzy of exploration and colonization. China clearly looks like the exception rather than the rule.

We don't have to leave the planet to mitigate supercomputer heating, we just have to wait (and survive). The earth's orbital geometry dictates long +100,000 year ice ages punctuated by brief +15,000 interglacial warm periods (like the current Holocene). The planet is already descending a several thousand year trend toward North American glaciation. AGW may extinguish us humans before most of the land is under glaciers, but the computers should be fine.

I can think of plenty. The universe is not that old and only had H and He at the start. That alone is worth half the age of the universe. Add another third for intelligent life. Galactic cores are rather depleted and nasty environments, so are not the most conducive environments. The threat from colonization may out weigh the advantages, especially if they are not integrated within the same civilization. If you are worried about hostile alien life, you should be really worried about hostile non alien life because they have much more in common. Nor should we assume the nearest civilization would have any interest in our planet. It may be too small, too large, too dim, too bright, too dry, too wet, too exposed, too remote, etc. i agree intelligent life is relatively uncommon or we would already be them, but I disagree space is small and that a billion years is enough time to colonize a galaxy. If you conclude it is uncommon, you are also concluding there are relatively few desirable locations and they are relatively distant.

If we are in speculation make-anything-up world, why can't we just assume that they have discovered some super-powerful "quantum air conditioner" (because it's not speculative pseudo-science unless we expropriate the world quantum!)

I don't think it helps that 2) and 6) are the same thing: each civilization independently decides to hide its presense.

Re: Self replicating probes. Estimates range somewhere between half a million and 3 million years to cover the galaxy (400 billion stars, diameter: 100,000 light years). NB: The initial civ does not need to survive. Some of the original calcs for this were done by scientists who were studying migration patterns of islanders in the Pacific (Finney & Jones etc..). If a space going civilisation arose at sometime during the last billion years, then decided to build such things, its surely likely that there would be a small probe sitting quietly somewhere in our cosmic neighborhood. Anyone doubt that 'we' might attempt to do this too, further down the line?

Maybe we just aren't very bright?

can DNA be your self-replicating probes that are scattered throughout the galaxy?

I've just read another solution. The book is "Starseeds" by Alfeld. Advanced civilisations communicate via asynchrony information spreading that does not depend upon the fortuitous presence of neighbouring intelligences occupying the same tiny slice of galactic time.

This assumes the probes weren't already here spreading single cell or multicellular organisms.

Most of the linked solutions (and a lot of the comments here) are missing the core of the paradox. It's not enough to say "they're all at the edge of the galaxy" or "they all stayed home." the reason it's a paradox is because it would only take ONE to decide not to do this, and to instead do the von Neumann probe thing or some other exponential form of expansion, and they would be here. The notion that out of potentially millions of civilizations, EVERY SINGLE ONE would all opt out of this is astronomically unlikely. "They're staying silent and "we can't communicate" have the same problem. So does "they kill themselves off". It only takes one.

The two types of answers that are immune to this are:
1) some form of "we are first, or near first, in our galaxy", e.g. luck, God, phase transition, our priors on the difficulty are way too low, etc.
2) some form of "someone is hiding it from us", e.g. whack a mole, zoo, simulation

Best explanation: There is a great stagnation in technology after a while for all civilizations. We are there. Technology never solves the scale of the universe problem in terms of long distance travel or communications. We are there. There is nothing really important left to discover that affects this. We are there.

The great stagnation does not explain the great silence.

The most advanced civilizations hanging out on the edge of the galaxy and beyond is the plot of Vernor Vinge's A Fire in the Deep. The reason is different (heat dissipation here and changing laws of physics in Vinge), but the basic idea is the same.

I personally vote for the "we're not capable of seeing the evidence that's there" option, since current human technology can't even see our own emissions above the interstellar noise, even as close as the edge of our own solar system. The only reason the Voyager probes know that Earth has civilization on it is that they know exactly where to look in the sky, and which frequencies to look at, and because we are sending focused beams to exactly where they are.

But Vinge's universe has some attraction. Any advanced civilization will be using quantum computers, not the clunky silicon based junk we deal with now. And there's plenty of mysterious quantum physics that might make some galactic radius a threshold for a new computational capability. For example, Roger Penrose has proposed that gravitational intensity drives the collapse of the quantum wavefunction, which would imply that the extremely flat spacetime near intergalactic space would allow for correspondingly extended quantum coherence durations, permitting levels of intelligence that would amount to supernatural capability in deeper regions of the gravity landscapes. Not to mention quantum entanglement and dark matter....

Another Fermi Paradox thread. Oh yummy. Time for everyone to come up with their pet theories again. So here's mine;
Indisputably we are closer to AI than starships. We might be only 20 years to AI if Moores law continues to hold. I am not too personally worried about a programmed AI, afterall when did your vacuum cleaner try to destroy you? What I am worried about is uploaded human intelligence. I know humans that are pretty evil. If I get uploaded I going to become pretty keen to make sure they don't get uploaded as well. Which means I must become an evil paranoid SOB. There will be pretty fast evolution once we get uploading, and the most evil SOB wil survive, and no one else. So this is what the intelligent life of the universe consists of. These entities are super intelligent, super paranoid and very dangerous. I would guess that we would be ignored by these things, unless we start to present a threat, say by starting to develop AI. In which case things will get ugly. I hope I am wrong.

So long as there are reasonable numbers that can be plugged into the Drake equation resulting in a value approximating one, there is no paradox. There's just numbers.

There are many big unknowns in the Drake equation. For example, we really have no idea how likely it is for life to wind up evolving into complex, intelligent, social beings. I think it's possible that microbial life is all over the place, but that the number of intelligent space-faring civilizations within range of detection may be on the order of one.

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