Has the Fermi paradox been resolved?

Overall the argument is that point estimates should not be shoved into a Drake equation and then multiplied by each, as that requires excess certainty and masks much of the ambiguity of our knowledge about the distributions.  Instead, a Bayesian approach should be used, after which the fate of humanity looks much better.  Here is one part of the presentation:

Conclusion 2: the great filter is likely in the past

Given the priors and the Fermi observation, the default guess should be that the low -probability term(s) are in the past.

The conclusion can be changed if:

We reduce the uncertainty of past terms to less than 7 orders of magnitude

The distributions have weird shapes

Note that a past great filter does not imply our safety

(The stars just don’t foretell our doom)


Life only actually occurs 8% of the time

It is also noteworthy that most life on earth shares the same genetic system, implying it takes a long time for a particular kind of life, and also intelligence, to evolve.

Those slides are by Anders Sandberg, Eric Drexler & Toby Ord, “Dissolving the Fermi Paradox,” and the pointer is from Patrick Collison.

Whew!  That said, your rate of savings now ought to go up just a wee amount.


"The Fermi question is not a paradox: it just looks like one if one is overconfident in how well we know the Drake equation parameters."


LOL, that this post has 23 and me comments is funny. Nobody knows what they are talking about here, except at the 10k meter level. It's not that anybody can be an expert in this area, like with Obamacare for example.

I agree. The Drake equation was a way describe something we can never really know. This may be an improved description of something we can never know. Maybe it is fun for practitioners, but even they should accept the unknowingness.

Maybe there are intelligent space aliens, maybe there are none, but we haven't found them.

"23 and me comments"?

 It would be unjust to say that Antonelli, who has introduced into Rome a magnificent system of domestic espionage, on the model of the Russians, has not turned his attention to the improvement of the city police.

Galafredo declared that he never killed any one who did not offer him open resistance. On the other hand, he murdered every priest he came across, and this is a tragic feature which stands out from his life's history; while at the same time, it proves that the element of clericality and robbery are always in contact in Italy.
        Galafredo loved a girl in his youth, but, at the same time, suspected her of a liaison with a priest. He watched him, and, one fine day, stabbed him to the heart, as he was kissing the girl. Thereupon Galafredo fled to the mountains,

SN 1987A was discovered by Ian Shelton and Oscar Duhalde at the Las Campanas Observatory in Chile on February 24, 1987. The light from the new supernova reached Earth on February 23, 1987. The electromagnetic rays warmed up Mexican pizzas across the southern hemisphere.

The anthropic principle lives!

Joe at Donatos don't know what a sonata is?

Life only actually occurs 8% of the time

That is more than I would have guessed. But I am not sure how this is matters because the numbers are so large. The galaxy has something like 100 million stars and there may be 2 trillion galaxies? The important factor is Mars. If two planets in our system have/had life, that would imply life is extremely common. And while this is a nice piece of work that is the only context in which Bayesian analysis makes sense - we can update our assumptions when we have another planet to add to the study.

That said, your rate of savings now ought to go up just a wee amount.

Personally I find the idea that life is rare more terrifying than the idea that life is common. I don't see why anyone would take comfort in the idea that life has appeared once. Sure, we are saved from the Face Huggers, but it means we live in a vastly more hostile universe than we thought. The risks of a Dalek take-over is small under any circumstance but the risk of the universe killing us out of indifference and ignorance is not trivial even now.

@SMFS, your second idea about life being common is quite insightful.........wait, who are you and what have you done to him?

Personally I find the idea that life is rare more terrifying than the idea that life is common. I don’t see why anyone would take comfort in the idea that life has appeared once. Sure, we are saved from the Face Huggers, but it means we live in a vastly more hostile universe than we thought.

No, it would mean we live in a vastly more indifferent universe than we thought. That's what terrifies the secular alien hunters. Despite their protestations to the contrary, the secular types still want to believe the universe cares about them.

Unlike the secular alien hunters, the religious alien hunters see the world as it truly is.

If there is a technological way to hunt for alien civilizations, and you can get a grant, why not? Especially when radio telescopes are relatively inexpensive.

No one has to be intellectually or religiously committed.

"The galaxy has something like 100 million stars"

Actually the galaxy has a lot more stars than that.

"The Milky Way is estimated to contain 100–400 billion stars."

Life existing in another galaxy is almost unnoticeable to us. Even if both sides had an agreed-upon protocol it's tough to say how they would communicate across intergalactic distances. (Although galaxies do travel through each other periodically, so life could jump galaxies that way.)

So the question is really just about the Milky Way. And we don't see any life. So something, by definition, must be stopping us from seeing other life, most likely that there isn't any. So what is the Great Filter that stops life from spreading across the galaxy? That's the question at stake.

There are some amazing things in Earth's past wrt development that might mean life like ours is super rare. Life might have developed on Earth, got blasted to Mars and developed further, and then blown back. (This isn't known but it fits evidence of no intermediate fossils between very eearly life and some slightly more complex life forms, that may have evolved as needed to survive both the Martian environment and the interplanetary void.) Perhaps its the frequent disasters we've had that have kept life moving forward by just the right amount.

Not sure how this isn't getting cited:


"It is also noteworthy that most life on earth shares the same genetic system..."

Wait, what form of earthly life is *not* based on DNA?

Well some viruses like measles and hepatitis C just have RNA. But that is probably not weird enough to count.

How about prions? Do they count?

Yes, those words are confusing.

To understand this mess is necessary to read about Last Universal Common Ancestor (LUCA) theory and viruses. After sequencing DNA from lots of organisms and comparing it statistically, it was found that Bacteria, Archaea and Eukaryota (Animals, Plants, etc) share a lot of genes. What the authors from slides describe colloquially as " shares the same genetic system".

The huge question mark are viruses. Evolutionary biologists don't know where and when viruses appeared in life history. It does not mean they're alien, it's just their DNA is not related to all other life on Earth. Hypothesis says there should be a pre-LUCA thing that evolved into viruses and bacteria, but research is still ongoing to prove or reject this hypothesis.

LUCA https://en.wikipedia.org/wiki/Last_universal_common_ancestor
Tree of life http://tolweb.org/Life_on_Earth/1

An idea that has gained support is that viruses derive from stripped-down bacteria. Some newly discovered viruses are very large and begin to blur the line with bacteria.

newly discovered as in "new to exist" or "we just found out about them"?


"""Pithovirus measures approximately 1.5 µm (1500 nm) in length and 0.5 µm (500 nm) in diameter, making it the largest virus yet found. It is 50% larger in size than the Pandoraviridae, the previous largest known viruses,[3] is larger than Ostreococcus the smallest eukaryotic cell. ... was discovered in a 30,000-year-old sample of Siberian permafros ... findings were published in the Proceedings of the National Academy of Sciences in March 2014."""

None but it might mean life is a 'one way trap'....once lift develops it doesn't go away and it dominates the environment. All life on earth shares common descent, so whatever the biogenesis event was that produced the first living thing, it was never repeated.

Or, early life quickly altered the environment such that the chemical precursors to biogenesis were no longer common.

Or, it occurred several times, but one lineage outcompeted the others into irrelevance.

It could be that new forms of life are appearing all the time along ocean vents or similar areas of dynamic chemical soups, but that the resulting life is quickly eaten or otherwise lost among the teeming hordes of "our" type of life.

Or maybe there were many biogenesis events, but all life shares the same Creator, which accounts for the similarities. https://en.m.wikipedia.org/wiki/Intelligent_design

and the Creator was just out of ideas ?

Of course not, but how should He change things for the sake of changing them? Fish have gills because they need them, they do not need different nucleic acids.

Sam Harris's recent podcast guest made an interesting point. Life as we know it has used particular methods to overcome some problems but that doesn't exhaust the possible ways to solve that problem. For example, nature has used a few different methods to achieve flight. But when humans wanted to invent mechanical flight they tried some of nature's solutions (flapping wing machines) but opted instead for a method not used by any living thing in nature (fixed wing combined with generating thrust).

If living things on earth had multiple biogenesis events, there's no particular reason to expect all living things to appear to be from common descent. Also I suspect as we get deeper into synthetic life we are going to find it is possible to have life forms not DNA/RNA based or based on things other than carbon.

If there's a huge number of possible ways to get living things, then there wouldn't seem to be any reason why an intelligent designer who wanted a diversity of living things on earth wouldn't have opted to make use of the full library of possible designs but if you are going to consider a 'trickster creator' who wants to hide his fingerprints or not let his creations figure out what happened then all bets are off.

octopusies have three hearts , why would the Creator do that ?

read about the story of the giraffes laryngeal nerve, why would the Creator do that ?


How many hearts you wanted octopusies to have? If it had one, you complain it is not original. Yet giraffes do not speak, only people speak.

The hell you say!

I think there are good reasons to believe God exists. So did our forefathers. Brazil's Constitution's Preamble acknowledges God's existence and, according to famous 17 th Century Portuguese writer Father Vieira, Saint Thomas founded Brazil.

I cannot ever remember being led astray by Brazil's Constitution.

Neither do I. It strikes the right balance between the rights of the individual and the interests of society, the needs of the many and the needs of the few or the one. It has been considered the second greatest Constitution of the history of the Western world.

On the other hand, an increase in the odds that the great filter is behind us should also increase the odds that AI could be a real big deal. Not sure how that affects your rate of savings.

Saving is less important than investing. Gotta own those AIs!

I am likely missing something, but does this not just suggest that the evolution of intelligent life and civilization on earth is exceedingly low odds? How does this avoid being some sort of fine tuning argument?

Low odds aren't a problem. If you buy enough lottery tickets at some point winning will go from being extremely lucky to almost guaranteed. The full universe is quite possibly infinite so any odds that are above zero guarantee something will eventually happen somewhere

Yes but if that "somewhere" is a few dozen galaxies away (and who knows how many light years) there could be intelligent life with a thriving civilization but they're too far away for us to ever be aware of their existence. Even inventing interstellar transportation only enables them to travel in the tiny local neighborhood of their galaxy. Heck, even the USS Enterprise could not travel to even the next galaxy.

My intuition tells me that there are plenty of planets with life scattered around the universe -- but almost all of them are too far away from each other to ever be aware of each other's existence.

Of *course* this is from the future of humanity institute. Those guys wouldn't want anything to get in the way of their singularity now would they? That place really does produce some world class bumf.

Judging by the work of Sandberg on his brain emulations I don't know if I'll read this.

As a child and young adult (i.e. when I was even more clueless than I am today), I appreciated the Drake Equation for both its simplicity and for its apparent universality. A couple of decades later, when I reviewed it critically I found it full of unsupported assumptions and flaws. The most obvious problem is that P_total is not equal to Pa*Pb if a and b are correlated (or "anti-correlated") and they certainly are, at least in principle. (The original Drake eqn's 1st 2 terms are Star formation and planet formation of those stars. Question: Is planet formation rate independent of the composition of the star? In a Universe consisting only of hydrogen will stars form? Yes. How about rocky planets? No. As I see it, the Drake equation needs to use integrals over time and space, and we just don't know what they are. Other (obvious) problems: there's no definition of "life", there's no definition of "intelligence" and only unsatisfactory ones (imho) for "civilization" and "communication technology". Finally: is it true that all life on Earth derived from a single common ancestor? Is it true that life only 'started' once on Earth? (started once = a single abiogenetic origin) We just don't know. Falsify the following:1) ancestral DNA migrated to the Solar System as one of the components forming the protostellar disk. 2) Life arose 41 times on Earth prior to the current version. 3) There are small subterranean pockets of life which do not (principally) use the L-amino acids. 4) There are small subterranean life-forms which do not use RNA. Or how about this one: The reason that we've not heard from them, is that they've nothing to say to us. Take a look at a typical morning on a Manhattan sidewalk. Remove the commerce. The only "intelligent life" talking to strangers is either deranged or hostile. So, the Drake equation lacks a term for "the number of technical civilizations which are deranged enough to bother".

Re typical Manhattan morning, I hear ya. But...

Flirting, displays of status, humor, virtue signaling (and what I've left out)-- all done via communication that can in theory be neither deranged nor hostile.

Anyone know if there a video or audio that accompanies the slide show? Thanks

What makes us think theres only one filter, and that its sooooo great?

Make filters great again!

I think Fermi's question was: If life is everywhere in the universe, where are they (shouldn't somebody have developed flying saucers by now)?"

Fermi didn't have HD TV; he didn't even have SD TV; not even B&W. Extrapolate another 100 years of communications progress, why would anyone fling their mortal coil across the light years when everything can be experienced without leaving home? A rose is a rose no matter who deconstructs/constructs its DNA.

PS. In our planetary neighborhood, every 26 million years for the last 260 million (no fossil record before that) there is a mass die off -- suggesting maybe a roving star (tentatively called Nemesis) tosses our comet cloud out of order and sends many diving towards Earth. Two die offs back the Dinosaurs checked out, making way for our furry night dwelling ancestors whose mammal brains integrated a little bit of light info with a little bit of smell, a little bit of touch, hearing. Made way in other words for intelligent life.

Possibly intelligent life wouldn't arrive so soon -- half way through the life of a 10 billion year start -- via purely random drift mutation. Surely there's lots of life out there -- but maybe very little intelligent life. ???

> Extrapolate another 100 years of communications progress, why would anyone fling their mortal coil across the light years when everything can be experienced without leaving home?

Because intelligent civilizations aren't immune to the pressures of evolution. There's a reason why continuous happiness is an elusive mirage, and we're always greedy, hungry, horny or pissed off. Every lineage whose brain was a little too generous with the dopamine just kind of sat around with smug self-satisfaction and died off. They either got devoured, starved to death, or didn't shower enough to get a girlfriend. End of the genetic line.

Now with modern technology, we've figured out how to hack dopamine. Video games, drugs, social media, and porn. Do you think the end-result will be any different? The cultures and genes most prone to surrendering to hedonism will sit in their basements plugged into to their VR systems, while the world passes them by. The neo-puritans and psychopaths who are resistant to these temptations will keep acquiring more wealth and power.

Eventually interstellar colonization will enter the realm of economic and technological feasibility. And the same type of people who need to own and dominate everyone in the room will also need to do the same for Alpha Centauri. The opiate-addicted cretins will whine and complain, but Lloyd Blankfein's descendants will tell them they either have to get on the colonist ship or pay their student loans. So, off to the stars they go.

Re: Eventually interstellar colonization will enter the realm of economic and technological feasibility.

Count me as extremely skeptical, unless some revolutionary new physics is found, allowing us to surmount the velocity of light barrier. Star Trek, Star Wars and all the other interstellar space operas are pure fantasy in this regard-- and it may well be the fact that there is no way to overcome the universe's speed limit and we are forever stuck in our own solar system, and other possible advanced civilizations are stuck in theirs too.

There is no need to assume warp to colonize the galaxy. A society that is rich enough could launch a colony ship to a nearby star at a reasonable fraction of the speed of light using present-day physics (although it is beyond present-day engineering).

Yes, exactly! I said as much in another comment: interstellar probes are totally possible, indeed they're possible right now just excruciatingly slow. Intergalactic travel is a whole other ball of wax. Even Star Trek didn't claim that intelligent life could travel between galaxies. There could be millions of intelligent civilizations out there, and we'll never encounter them because they're in different galaxies.

That strikes me as the most plausible and likely "outcome" of the Drake equations and Fermi filter: millions of intelligent civilizations, but except for the handful that happen to be located within the same galaxy, they'll never be aware of each other's existence.

You explain "why most people don't cross great distances" but you still have to answer "why no people cross great distances." Colonization has never been about a majority of people moving. It's always been a tiny tiny number.

I don't know if Elon Musk will be able to get enough money to colonize Mars, but if not him then eventually someone else will accumulate both the drive and capital necessary. Unless there is something prohibiting him from doing it.

Two unrelated thoughts on the current debate from a philosophy professor:

1. What does Bayes contribute to this? "Given the priors..." WHERE DID THOSE PRIORS COME FROM? People are just making guesses, pure and simple. But if you express your guess in the form of a number (just call it a subjective credence) and do some math, it becomes science? The level of mathematical precision in this presentation is comical given that this is all pure speculation.

Not that I'm opposed to pure speculation - I'm a philosophy professor, after all. But I am opposed to the use of empty formalism to make speculation look like proof.

2. The great filter is obviously the existence of replicators in any form.

Evolution cannot account for the existence of replicators. Evolution by natural selection ASSUMES the existence of replicators. The story of replication by natural selection requires things to be able to copy themselves in a fairly high- fidelity way.

All life on earth replicates in the same way, at a biochemical level. Nucleic acids serve as the "blueprints" for life containing the blueprints for proteins. Biological processes read the string of acids in a DNA/RNA strand, and build a protein out of those instructions. But those biological processes are performed by molecules that are... proteins! Nucleic acids and proteins are an epic biological chicken and egg. To have a biological replication system of the kind that exists on Earth, you need both. So what are the odds of both of these kinds of molecules arising, by chance, in nature, given that these molecules could not have evolved? Keep in mind, of course, that I'm not just asking how ANY chains of nucleic or amino acids could come into existence. We need the specific patterns that can replicate when they form a system with one another.

What are the odds of THAT happening by pure chance?

The best argument for the existence of God doesn't involve the fine tuning of physical constants, but the existence of the complex molecules required for evolution to even begin to occur.

Ultimately, I think this is a bad argument for the existence of God - the universe is truly vast - infinite, probably - so it's not crazy to say that this could happen by chance once or twice. But it was very silly for Fermi to wonder why we hadn't encountered any aliens. I would be genuinely shocked if we ever do. I'm amazed that life exists anywhere in the universe.

One the one hand, yes, spectacularly rare. On the other, it's a recondition for our existence and therefore certain. We all won the lottery being the only winner of a lottery of hundreds of millions of sperm. But how could it be otherwise?

Maybe the universe has exploded and collapsed trillions of times before this.

"1. What does Bayes contribute to this?"

This is the future of humanity institute, which at times seems like an intellectual offshoot of lesswrong.com, which is itself the internet's #1 spot for all your Bayes related needs, whether applying bayes in the situation at hand makes any sense or not.

Both quotes from https://en.wikipedia.org/wiki/Fermi_paradox
"There are two parts of the Fermi paradox that rely on empirical evidence—that there are many potential habitable planets, and that we see no evidence of life. The first point, that many suitable planets exist, was an assumption in Fermi's time that is gaining ground with the discovery of many exoplanets, and models predicting billions of habitable worlds in our galaxy.[35]"

We Fermi was certainly making the assumption but I wonder how much different that application of models such as these really differ from the orgianal assumption. True, we now have some type of empirial data that says planets are there -- not really sure we've actually seen them yet -- but...

"The second part of the paradox, that we see no evidence of extraterrestrial life, is also an active field of scientific research. This includes both efforts to find any indication of life,[36] and efforts specifically directed to finding intelligent life. These searches have been made since 1960, and several are ongoing.[37]"

I often wonder if we would be able to recognize the EM signals from other civilation. For instance, if they have good cryptography won't those signal just look like noise? We assume the we can recognize language but I think that's also due to the fact we often know something alive is making the sounds. If we didn' know whales and dolphines existed in the oceans but could hear the sounds what would our explanation be?

As I recall, the original Fermi discussion involved "intelligent life capable of interstellar travel." Detecting and interpreting signals from a planet millions of light-years away (of necessity, this means signals from millions of years ago) is not precluded by Fermi's discussion, but that is something less than most SETI enthusiasts are hoping for.

My favorite book on the theological/psychological implications is Walker Percy's Lost in the Cosmos. He works through some thought experiments about first contact (like Li Zhi asked above, mightn't aliens find our confused species too deranged to bother with?) The way he phrases the alternative is haunting: "What if there is no man Friday and we really are alone?"

"Has the Fermi paradox been resolved?"

Never attempt to draw a trend from 1 data point.

Over-science at work here I think. The basic logic of the Fermi paradox remains; hundreds of billions of planets around similar number of suns, and in theory several billions of years mean that even with low chance on each planet, the odds are very high that life will spontaneously occur.

My explanation for the paradox is the multi-universe one. If the idea of a multiverse is correct then each and every intelligent life form that chooses to travel to the stars will find itself the first in it's own light cone, for the simple reason that it doesn't exist if it is the second, because the available planets have already been colonised long before it has a chance to form. Its sort of like we don't expect monkeys to evolve now in a human controlled biosphere on earth, there just isn't an ecological niche for semi-intelligent monkeys to evolve into. If plant earth had been colonised in dinosaur times, humans wouldn't be wondering where all the aliens were.

Fascinating but not wholly convinced on the multi-universe light cone scarcity concept. The 'development path' along a light cone is a rather large thing and the amount of time to traverse it (much less colonize it), even near the speed of light, is likely longer than many intelligent societies need to start, develop, and die/disperse/transform -- even assuming that cultures could not overlap or were restricted to the same type of planetary conditions, which likely change over the eons anyway.

My answer (which takes the more cynical and psychological/sociological bent) to the Fermi Paradox, which I interpret in the simplest notion of 'why haven't we detected any other alien species': is that when a 'culture' gets to a certain level of technological development where they can reliably detect, communicate to (if not with), and have the means to physically travel/ interact to the location of that evidence, that a society is very likely to have achieved a level of transcendence when each entity no longer requires/desires to be part of a common 'physical culture' nor seek out others short of information-gathering. At that stage, there is likely negligible scarcity and negligible death (or otherwise permanent dissolution of the entity's identity). This means that a planetary or multi-planetary identity really isn't that compelling. The vision is that each entity takes its own path with virtually unlimited access to knowledge and experiences (and communications) to occupy itself. Why would one want to be limited to the discomfort and pedantic challenges of a planet surface when the ability to travel throughout forever, without discomfort, beckons? The only value worth pursuing is to develop a truly unique experience path - which means scattering endlessly to the cosmos. So the answer to the Fermi is that alien life is spread thinly everywhere and nowhere - all-seeking but without interest in taking the time/risk in being known. Further, super-societies with advanced Kardashev numbers and great super structures (dyson spheres, etc) and their requisite energy demands will not form. It seems sad in a way, but the planetary mindset is a short and fleeting one.

Excess Certainty.
Those two words describe not only the instant issue but the larger world of economic science.
Economics could incorporate some credibility tools by explicit acknowledgement of just how firm, or not, the various pronouncements are and what qualifications, limitations or other caveats may be used, transparently or not.
Don't pretend that everything has an R-squared of 1 when it doesn't.

Could it be that life was easy (because there are signs of it that are very old) but that eukaryotes were hard enough that they only happened once?

Nick Lane argues for that point pretty well in The Vital Question: Why is Live the Way it is.

...or we could just embrace the findings, avenues of research being followed, and our own technological progress of creating a more viable presence above LEO.
The Fermi is just navel gazing writ cosmic. Enjoy the almost-outward journey through the proliferation of papers and experiments such as:


A fascinating excerpt:

"... thoughts on cosmic modesty ring true. We’ve been able to extract some statistical conclusions from the Kepler instrument’s deep stare that let us infer there are more Earth-mass planets in the habitable zones of their stars in the observable universe than there are grains of sand on all the Earth’s beaches. Something to think about as you read this on your beach vacation..."

Obligatory xkcd reference:

The 'B' stands for Bayes!

The hydrogen hypothesis for the origin of the Eukaryota is likely the great filter.

Somewhat off topic, I'd really love to have you interview Eric Drexler about the current state and future of atomically precise manufacturing. The US Department of Energy has apparently agreed in the last few months to throw a few million dollars to research Drexler's vision of atomically precise manufacturing.

I second that interview choice. The Engines of Creation was the first book I read in college in Sep 1987 before classes began. I got the gist of it and Compute! magazine gave a 10 to 30 year prediction when nanotech applications would be widely used. I thought too soon so said 2030 - the year I'd be 60 and really, really old if still around.

> Life only actually occurs 8% of the time

This is a misquote of the slides, and suggests a meaning pretty different from the real quote!

The actual quote in the slides is: "'Life only once' actually occurs 8% of the time." Note the "only once" -- the context makes clear that most of the time (according to one particular calculation), you'd expect life to arrive *more* than once (in more than one solar system) in a given universe.

See also Brian Lacki's arxiv posts:
"Type III Societies (Apparently) Do Not Exist" https://arxiv.org/abs/1604.07844
"The Log Log Prior for the Frequency of Extraterrestrial Intelligences" https://arxiv.org/abs/1609.05931

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