Dissolving the Fermi Paradox
slatestarcodex.com
slatestarcodex.com
They estimate that the greatest uncertainties lie in the past terms of the Drake Equation, ergo that there is no evidence of some great threat to the continued advancement of human civilization.
You don't need extremely low values in the Drake equation to end up with nearly no aliens. It's actually kind of likely that we're (close to) alone, even without a crazy complicated theory to justify one of the values being nearly zero.
This is missing the point that many people do treat the Fermi Paradox like it's a real paradox - like there's some kind of fundamental universal principle that has to almost universally block out all life or all communication.
The article is saying you don't need it. It's good enough to say "well, life might just be sort of uncommon, and even in that scenario we shouldn't be surprised that we got a very low roll."
That is a surprising conclusion. No, we don't know the exact cause, but it means that the Fermi Paradox might not be a paradox, in the sense that it doesn't directly contradict all of our priors.
Think of it like the difference between saying, "Trump won the election because we fundamentally don't understand how democracy works in practice", and "Trump won the election because he had a 1 and 5 chance of winning, and sometimes 20% chance events happen."
This is a great point. Still, if you say "we don't understand democracy because we don't understand that 20% chance events happen" then it seems like the points converge.
excuse me, but no. Our best-effort guesses might be the best we could literally do. But there is no need to be that literal, or literal at all. As long as the uncertainty range includes 0.5, it's OK, but merely a test of how much we know as a fact as opposed to intuitively. And at that, the equation can surely be blown up further. Why would it be optimal?
Of course if we do some more experiments and find that in fact the probability of abiogenesis is better approximated by 10^{-3,-2} that would change the expectations dramatically. This happened recently: we now have much better science around the incidence of earth-ish planets in solar systems, and a better understanding of what seems to contribute to good life-favorable (at least as we understand it) conditions on those planets. So this uncertainty can change with good work.
It's just that at this point it's really quite fair (per the authors) to expect that with more research we might equally well discover that P(abiogenesis) < 10^-100, in which case it would be astounding if we weren't alone in the observable universe.
(Good talk slides: http://www.jodrellbank.manchester.ac.uk/media/eps/jodrell-ba...)
If you give any particular term in the Drake Equation a value of some magnitude, say, P(abiogenesis) < 10^-100, then you're still treating it as a point estimate, and this is the flaw at the heart of all arguments about the Fermi Paradox.
What the authors do instead is give each term of the Drake Equation a range of magnitudes. When you multiply those ranges of magnitudes together, you get a ton of different possible outcomes. If you then look at those outcomes together, you find that in over half of them, we are alone in the universe.
This is the "multivariate probability" that a top comment referred to, that seems to be problematic for a lot of people (including me).
The authors point out that with this approach, even if we nail down the range of probabilities for some of the terms, the uncertainties of the remaining terms will still lead towards a > 40% chance of being alone in the universe.
It's a little bit like: in a poker game, I draw five cards. Each of my cards is a 2, 3, 4, 5, or 6. What is the probability that I drew a straight? To calculate that, you'd count the number of different possible card combinations, and then count the number of those combinations that resulted in a straight.
What everyone has been doing previously in this analogy is calculating the odds of drawing each individual card.
In the case of the Drake Equation, using a probability distribution approach to estimating the chances of being alone in the universe leads to a very different result than we expect.
I hope I didn't add to the confusion.
Since we do not really know, anything but P=0.5 should imply incorrect prior estimates. That might be more insightful than whether alien life exists or not.
The blog kind of references a situation where you'd have a high variance distribution but doesn't really describe it. There isn't any argument against the claim that the chance of a civilization on a given planet is independent of the chance of life on all the other planets in a given galaxy (modified by star-type but not by whether there's life nearby).
"In this example, the point estimate for each parameter is 0.1, so the product of point estimates is a probability of 1 in a billion. Given a galaxy of 100 billion stars, the expected number of life-bearing stars would be 100, and the probability of all 100 billion events failing to produce intelligent civilizations can be shown to be vanishingly small: 3.7×10 ^−44
[...]
However, the result is extremely different if, rather than using point estimates, we take account of our uncertainty in the parameters by treating each parameter as if it were uniformly drawn from the interval [0, 0.2]. Monte Carlo simulation shows that this actually produces an empty galaxy 21.45 % of the time."
I take this to mean that collapsing a range into a single point will artificially inflate that point, and instead you need to look at the number of possible outcomes, not the average of all outcomes.
From the related blog post:
"Imagine we knew God flipped a coin. If it came up heads, He made 10 billion alien civilization. If it came up tails, He made none besides Earth. Using our one parameter Drake Equation, we determine that on average there should be 5 billion alien civilizations. Since we see zero, that’s quite the paradox, isn’t it?"
That seems like a consistent reading to me. Maybe I'm wrong - I take it you would draw a different conclusion?
Edit: No, thinking about it more and reading some other posts, I kind of get what you're saying. I'm still not really sure I'd call that a paradox though. It still seems to suggest to me that we may not need to rely on any of the really big theories to describe why we don't see life.
The article and blog's meta-argument involves choosing components over a random distribution of universes and saying "well, there's a good chance you wind-up in a universe with small". But reasoning about random universes is debatable, introducing unnecessary metaphysics but even so, if you wind-up in a universe with a small chance of an advanced civilization, you will wind-up in a universe with Drake's components also small. Which is to say the whole reasoning does nothing but "muddy the waters".
The only way the "randomly chosen universe" argument matters is if we're jumping from universe to universe or if there's a force that inherently keeps us from reasoning about the why of the Drake components - but neither of those conditions are met.
A good place to start is Project Blue Book however, it has years worth of information that was reported by members of the public etc that the government looked in to. I don't believe it was conclusive in proving the existence of these objects, but rather proof that the government was taking some level of interest in it.
https://www.archives.gov/research/military/air-force/ufos.ht...
Even Moses might not have been that impressed by merely a talking, burning bush.
People in ancient times doesn't know much about the earth either.
The paper exactly explains why this is not the case. This is demonstrated using undergraduate level Bayesian probability.
This response is one of many when this work comes up on HN that would benefit from a basic understanding of multivariate probability.
When you consider UFOs as a manifestation of ET civilization, the Fermi paradox does not exist.
my sides!
The right answer to this question must remove the logical contradiction, and this is what we are interrested in. The answer that the ETs are visiting earth and reported through ufological sighting would be a valid one, but it is systematically ignored or discarded when considering the Fermi paradox.
That is, in my opinion, the only paradox.
PS regarding the downvote, Hackenews is not Facebook with its like button. On Hackernews, downvotes are for people who don't respect the rules.
The Fermi Paradox hasn't been "dissolved" in any way. It's a response to the idea that the universe is teaming with life. The paradox remains unchanged until we find a credible signal, or we create life in a lab under naturalistic conditions.
I do think it's a fair inference that there can be life elsewhere, and even that there is life elsewhere.
Also, the Fermi paradox is about advanced lifeforms. The universe may be teeming with primitive life forms. If we can't find any primitive life elsewhere in the Solar system, then we might not find out until we develop interstellar travel, and even then, "find out" would mean on time scales longer than a single lifespan.
Pointing out that we can only speculate seems... given that this is obvious... unnecessary. Perhaps you meant that we should not speculate?
The Fermi Paradox has been dissolved in the sense that there is no longer any paradox; that is, there's no contradiction between what we've observed (no life so far) and what some people expected from doing a rough calculation.
So yes, we still don't know if there's other life in the universe or not and there's no new evidence. But, at least for some theorists who accept this answer, a logical puzzle is no longer a puzzle.
They use Bayes to update their estimates based on the lack of evidence so far (which is, itself, evidence for lack of advanced stellar civilizations).
It has been dissolved in that they've pointed out a fundamental error in the logic that leads to the paradox, and have used statistics and a review of available literature to illustrate this error.
The paper goes into this starting on page 12. After establishing estimates based on a variety of factors, they then adjust the results by pointing out that "there were no Type III Kardashev civilizations using more than 85% of the starlight in 10^5 surveyed galaxies" and that "the lack of observable settlement provides a strong bound on extraterrestrial intelligence".
They proceed to offer approximations for Bayes conditional probabilities with different formulae for no stars having been observed to have civilizations, no civilizations within a detectable distance, and no settlements within nearby spacetime.
After putting all of this together, they conclude in section 4.0 that, "The Fermi observation thus raises our 52% credence for being alone in the galaxy to somewhere between 53% and 99.6%, depending on the type of evidence considered. It likewise raises our 38% credence for being alone in the observable universe to somewhere between 39% and 85%."
Essentially, they're saying that if the probability of detection is some value if there are intelligent civilizations in the observable universe, then how does it change the model that they haven't been observed? I am not a knowledgeable enough mathematician to judge whether this is an appropriate use of Bayes or not, but I would expect that someone would have already pointed it out if it weren't.
They then conclude section 4.1 with, "...unless one assigns a very strong prior to [a systematic failure to detect observable civilizations], our qualitative conclusions still hold."
The only thing Drake can possibly estimate is the number of civilisations similar enough to our own to be recognisable.
There's an assumption that every civilisation will pass through a stage where can recognise it - but of course there's no good reason to be confident this is true.
So in fact the L term is unknowable.
There's also the fact that not all civs will transmit, but some would be visible to better spectroscopic tools. Generally, as our technology evolves you would expect our detection skill to increase too.
This isn't included in the original equation.
Yes it is. You may be confusing 'evidence' for 'proof', but here's a proof that absence of evidence is indeed evidence of absence. (How much? That depends.) http://kim.oyhus.no/absence/index.html
Well, I don't see any evidence of light, but that isn't evidence for the absence of light. So I guess I just can't know.
That's the inherent problem with only having one example of something. For all we know, our current way of being is fundamentally closing off our perception that would allow us the knowledge that intelligence exists beyond our own. Even our own thought patterns could be fooling us.
For example, we could very well visit a planet in another star system and be like...
"Wow, this whole planet is covered in rust. What a wasteland! Let's get out of here."
And we might not even think that the rust is actually an intelligence. We might figure out that it's living, after years of stomping on it or trying to mine base elements out of it, but we might never know that it's actually much more intelligent than we are because it doesn't have the innate human drive to spread out, conquer, explore, etc., all of which are not necessarily indications of intelligence.
The most basic building blacks just happen. The minor assemblies seem to be easy. The smallest key pieces seem to involve a bit of luck in the beginning - it may take a handy bit of inorganic scaffolding, some weather and something like tides to build the first self-replicators, but one you have them, the scaffolding isn't needed anymore. Getting from there to proper cells - replicating, metabolizing and homeostatic - takes a considerably bigger collection of chance meetings of chemistry and environment, which may take just a bit longer than we've been trying so far, and a much bigger lab. Even if replicators are common, "real" life might not be.
And then there was a little more than a three-billion-year wait for cells to stay stuck together and cooperating in the only successful experiment we know of. Multicellular life may be rare, even if life is common. Tool-using, highly intelligent life that has harnessed fire to its will doesn't necessarily follow, and that's pretty much a sine qua non of a civilisation capable of interstellar communication, let alone interstellar travel.
No matter how easy the first 500 million years or so of the formation of life on Earth may be, the assumption that what happened over the next 4 billion years is somehow a straight shot is one hell of an assumption. Almost nothing happened for about three billion of those years, and the catalyst for multicellularity may have been an exceedingly rare, even unique, set of circumstances.
The universe, the galaxy, may indeed be teeming with life, but it's much, much more likely to be little green slime-covered mud mounds than little green men.
Lately, some of the time I see this as a metaphor for 'what is the dilemma with broadening horizons?'
There could be alien life, there could not be. It's interesting to think about for a while but sometimes I think it is talking about something deeper than the existence of aliens and outer space. Philosophical question about the nature of existence.
Even if only a fraction of a fraction of a fraction of all life make it to what we could call "intelligence", then those beings are most likely millions or billions of years "ahead" of us, or won't be intelligent for millions or billions of years from now.
At those timescales, even things millions of light-years away are "within reach" of some kind of contact, unless there is something making it impossible (like all intelligent life snuffs itself out given enough time).
This is easily one of my favorite things to just think about.
The question makes no sense because there is no plausible model: he may willingly decide to guess wrong, for example, or the trick may consist in making you forget the card or any other thing.
Assigning probabilities without a real model is just hubris, no more.
Personally, I think the chance of encountering another civilization is exactly [0,1]. Pending data to adjust that range.
They would look like infrared point sources. Sadly none detected yet:
https://medium.com/starts-with-a-bang/dyson-spheres-the-ulti...
[0] http://www.astrosurf.com/luxorion/qsl-mars-communication3.ht...
He pretty much handwaves away one of the biggest problems: material. Saying "we'll harvest Mercury" is such a "world hunger solution"* that I can't take anything further seriously.
*World hunger solution: A solution presented in such a way to seem simple but instead hides many more problems just under the surface. e.g. The best solution to world hunger is to simply give everyone enough food. True, that would solve the problem, but we don't know how to do that.
And saying that "advanced civilizations" will be able to do it is pretty much going into the Giorgio Tsoukalos camp. "Aliens" is not an answer. It still ignores the how. What are the costs of harvesting an entire planet? What are the energy requirements to send mining equipment there, mine the planet, and ship the materials back here to be processed into something useful?
Why do you assume that that level of technology will be cheap and readily available in the future?
Also, what options do you have if you're out of real estate? There is no faster than light travel. Slower than light interstellar travel is certainly not going to be cheap or easy. Of course the other option is for your civilization to stop growing, but who knows if all aliens would go for that.
It doesn't tell us why there are no Dyson spheres.
> Of course the other option is for your civilization to stop growing, but who knows if all aliens would go for that.
You act like this is a choice. What if it's not a choice? What if the initial cost to build a Dyson sphere is too great to overcome? Whether in time, material, energy, or another thing. What if it's just not feasible?
Where does that leave you?
You've basically reframed your statement. You find it convincing because you think it seems physically possible. But how? We're just getting to Mars and you think a significant mining operation on an alien planet to be something we're technologically capable of.
We've skipped straight to 3) Profit and forgot to flesh out step 2).
There's no reason to think we won't reach that level of technology - assuming we have a demand for space industry for some reason, like running low of key materials on Earth, or a population that keeps growing.
You're basically just doing that same thing as the OP, claiming "nuh uh" without backing that up either. To which I say "uh uh".
You claim there's no reason to think we won't reach that level of technology. What's the basis for that claim?
> just some solar panels floating in space an attached to something useful (e.g. our communications satellites)
You realize that a lot of our communications satellites already have solar panels attached to them, right?
And you do realize that a Dyson anything is an engineering project that far exceeds anything we have yet attempted. If your plan begins with strip mining a planet 48 million miles away with an army of self-replicating robots, you've obviously skipped a few steps of the process.
Using "science-y" words to describe your pipe dream doesn't make it any less of a fantasy.
I mean, we're still wondering if we can make a car drive itself reliably. That we may not be able to overcome some very basic limitations. And all of a sudden we get to assume we can build a probe that can travel to Mercury, mine it, process the raw material into something useful, assemble those materials into more probes, panels and habitats, then place those bits into orbit around the Sun in a way that it won't get smashed by other satellites, fly off, or get pulled in.
Reducing those concerns to "nuh uh" isn't doing you any favors. You're simply refusing to engage. You're asking skeptics to prove that we will never reach that level of technology rather than answer the question of why do you think we will. You're the one with the actual claim here, back it up.
Hence why I said (e.g. our communications satellites), which in English means communications satellites are examples of useful things with solar panels attached "floating" in space...
> And you do realize that a Dyson anything is an engineering project that far exceeds anything we have yet attempted. If your plan begins with strip mining a planet 48 million miles away with an army of self-replicating robots, you've obviously skipped a few steps of the process.
I already mentioned that's a strawman. A Dyson swarm is an orbiting collection of artificial satellites, orbiting the sun. It captures all or a good deal of the energy radiating away from the sun - but it's built incrementally and a single satellite can be the start of a Dyson swarm - so we have the tech now.
> You're asking skeptics to prove that we will never reach that level of technology rather than answer the question of why do you think we will. You're the one with the actual claim here, back it up.
You're deluded if you think you can get random people on HN to defend their statements to a level you'd be happy with. Honestly I don't have the time, and even if I did I don't care.
But since you've got me to engage this far, here goes: we have the tech to build solar powered satellites and launch them into orbit around the sun. So we could start building a Dyson swarm today.
The reason we don't is because it's very expensive, and we suffer a chicken-and-egg problem. There's not much demand for industry in space because we don't build anything in space. The inputs and outputs would have to come from and return to Earth. There's no demand for habitations in space because there's no supporting infrastructure, food, water, jobs, etc. Not to mention the long term health effects of living in space seem problematic to say the least. But it's not unforeseeable that something could change that situation, be it overcrowding on earth, demand for space mining, demand for zero-g manufacturing, space war, government programs, etc.
What you actually said was:
> You don't need to build the entire thing, just some solar panels floating in space an attached to something useful (e.g. our communications satellites) fit the bill.
Where the implication is that we'd attach these solar panels to something useful and that an example of something useful is the communication satellite. Whereas you wanted to infer that communications satellites were the entire enchilada, a solar panel attached to something useful. Which is also a bit disingenuous as the panel is a part of the satellite, the power source, not an add-on. Which pretty much led to the confusion.
> A Dyson swarm is an orbiting collection of artificial satellites, orbiting the sun.
That's a reduction as to what it actually is. A big part of the Dyson architecture is to capture and use the energy provided by a star. Simply having a satellite orbiting the Sun would not fit the bill.
And a space based solar power satellite does not exist. Because it's more expensive to launch and implement than it would return. All current solar power on satellites provide enough power to power themselves. That's it. What you are asking for is something different.
NASA themselves says that a SBSP satellite is decades away at the earliest. And any proposition to be speculative at best.
And yes, necessity is technically the mother of invention but it can't change the laws of physics. It can't change the cost of what's necessary.
> You're deluded if you think you can get random people on HN to defend their statements to a level you'd be happy with.
This is just a dodge. You've done nothing but say "It's not unforeseeable" and "It's inevitable". You haven't actually provided a reason as to why you think that. I'd be happy with anything more than a handwave in the general direction of the actual issues facing building a Dyson swarm.
> Honestly I don't have the time, and even if I did I don't care.
You do care, you just don't really have any answers besides the blind faith of "technology". Which is no better than blind faith in anything. Believing technology will get better doesn't actually make it better.
Why? I know it's a staple of SF that, on a long enough timespan, we will surely eventually build stuff like Dyson swarms and interstellar ships, but the more I observe actual humans, the less convincing I find this argument. Even assuming great advances in technology, Dyson swarms will be ridiculously expensive to build, especially relative to the benefits they provide, and human grumbling about costs and taxes will probably kill the project instead.
More generally, given the conflict between "fund and build this highly exotic and expensive thing now" vs. "don't bother, thus keeping taxes low", humans will always choose the latter in the absence of some kind of external motivation beyond "for science!", or even our own survival. Americans only agreed to spend the zillion dollars to go to the moon because we were in a dick-waving contest with the Soviets, and a lot of the necessary technology was already in existence thanks to money spent on ICBMs.
I think it's more likely than not that we will keep kicking the can down the road vis-a-vis the current problems of our population growth, and then just go extinct when they finally catch up to us. Or, even if you're not that pessimistic, that we just stay on Earth because no one wants to bother with the difficulties of going elsewhere. It's totally possible that the same thing happens to most other intelligent species and so there are no Dyson swarms.
Just think, a military entity with the population and resources of NATO or the Warsaw Pact would have been totally inconceivable just a few hundred years ago.
Worse, in such a civilization, it's pretty likely that even small organizations would have the kind of tech you'd need to induce a nuclear winter on a given planet. After all, you just have to crash an asteroid on the right spot, then you have a mass extinction that human civilization would definitely not survive.
The Fermi problem is a speculative theory based on extrapolating human civilization's use of energy to stellar levels (various hypothetical civilization "types" etc). It's plausible life at the scale of earth could be common, based on the principle of our natural non-uniqueness. So the simplest explanation is the speculative extrapolation to stellar energy uses is wrong - human already are more destroying themselves with excess energy use than preparing for any next stage, just as one datum.
It's not much weirder than things humans get up to, and if spacefaring civilizations that can build such probes are common at all (even if short-lived), you might expect at least one of them to have initiated such a project and been successful enough to have built a giant "we wuz here" radioactive pyramid on the moon. Evidently, none of them did- and depending on how many there were, this is either unsurprising or deeply unlikely.
That YouTube channel is awesome by the way. Say goodbye to the rest of your afternoon!
* How many habitable planets are out there? We're just now starting to get data on this, there might be a lot
* Of those, how many develop life?
* Of those that develop life, how many develop intelligent life?
* Of those that develop intelligent life, how many advance to the point where they're capable of interstellar travel? How many are interested in interstellar travel?
* What if FTL travel is simply not possible? STL interstellar travel could basically be a one-way trip. Maybe most (or all) alien civilizations are unwilling to explore beyond a few light years.
* What is the lifetime of a space faring civilization? maybe all the alien civilizations just died out before they explored very far.
What if another species has figured out a way around death? What if the idea of a single "life" isn't really a thing, and alien lifeforms instead live as a single "consciousness" among them all forever alive. Then the idea of spending millions or billions of years traveling around the universe isn't necessarily a "one way trip".
But to answer your question, absolutely the first. That way, if we are more benevolent than the Machiavellian necessity, we will either pioneer an improbable United Federation of Planets or be eradicated due to our idealism and naivete.
There's no "intuitively" about it. We know from the data available that the probability of machine-building general intelligence of the kind that is unique to humans on Earth is fantastically unlikely to arise. It depends on a confluence of completely unrelated selective pressures: one on tool-making, one on social cooperation, and one on continuous mate competition/selection. There is good evidence that all of those forces are important to specifically human--not dolphin or bird or whatever--intelligence on Earth, and without any one of them we'd still be fairly handy monkey-creatures banging rocks around.
As well as a theoretical understanding, we have empirical data. We can ask, "If something is at all probable how many times will it have evolved on Earth?"
Eyes, for example, have evolved independently multiple times, based on differences in retinal biochemistry. Wings and fins and legs have also evolved many times across an incredible diversity of species. This tells us that things that are easy to evolve have evolved multiple times in Earth's history.
Specifically human, machine-building intelligence has evolved exactly once. This is strong evidence that it has an enormously low probability.
Once you've realized that one of the parameters in the Drake equation is incredibly small, the Silent Universe is no longer surprising. And both empirically and theoretically, the probability of evolving specifically human, machine-building intelligence is incredibly small.
However, I have never met anyone enamoured of Fermi's Paradox who gives any credence to this, which is why no attempt to resolve the paradox will ever have any effect on the discussion. This is in general the case with so-called paradoxes: no matter how many times they are clearly and simply resolved, people who want there to be paradoxes will pretend the resolution doesn't exist, or will deliberately misrepresent it as a non-solution. Or they will present some other non-solution as more compelling, even when the solution presented makes those non-solutions unnecessary.
Highly recommended.
The 3 body problem is masquerading as hard SF but isn’t. The author totally misunderstands physics, astronomy, and space faring technology. I hated the books, personally, and don’t see why they are so hyped.
Anyone that's read even the intro section of the Fermi paradox Wikipedia page already has: "There have been many attempts to explain the Fermi paradox ... suggesting that intelligent extraterrestrial life is extremely rare". The paper just formalizes that by demonstrating we can arrive at low enough expected numbers of aliens (namely 0) with reasonable inputs to the drake equation.
> Imagine we knew God flipped a coin. If it came up heads, He made 10 billion alien civilization. If it came up tails, He made none besides Earth.
This occludes a lot more than it illuminates. Although the end section of the paper uses the bayesian inference Sniffnoy hinted at, the graphs SSC used (and his analysis of the papers results) come from the earlier section of the paper that still use the "chance of aliens per star" model. Even the bayesian part merely refines this probability based on observations; it's hardly "the wrong way to think about it" as SSC claims.
In summary, the traditional approach to the Drake Equation has been to assign fixed values to each polynomial, sometimes an ass-pull and sometimes based off of best estimates from the observable universe. i.e., "0.1 x 0.1 x 0.1 x 0.1..."
What these researchers did instead is try to account for the uncertainty of various parameters. They gave each polynomial values in the range of [0, 0.2] for example, ran Monte Carlo simulations on that, and came up with an empty universe 21.45% of the time.
To put it another way: we consider it a certainty that some worlds will bear life, and a certainty that some of that life will develop into intelligent civilizations, and a certainty that some of those intelligent civilizations will explore their local system, and a certainty that some of those explorers will develop into massive hyper-intelligent, technologically-advanced, galaxy-spanning species. But we haven't got enough information to be certain about any of those within any reasonable order of magnitude. The probability of any one of those may in fact lie so close to 0 that it solves the Fermi Paradox.
FWIW (and it's worth basically nothing), this has been my preferred solution to the Fermi Paradox for a long time now, and it's nice to have this paper to cite when it comes up in the future. I figured that it took Earth 4.5 billion years to produce humans, and humans are only barely space-faring at this point and I'm not certain we'll ever make it out of our solar system. Countless species have appeared and gone extinct in the meantime. It seems far from certain, to me, that evolution necessarily leads to intelligent life, and if I remember right, the latest thinking from evolutionary biologists supports this -- suggesting that modern human intelligence is largely accidental, rather than a byproduct of evolution.
The age of the universe would seem to suggest that there's been time for at least a few other worlds to develop intelligent life even at very slow, unlucky paces, but then again, at astronomical time scales the universe has been too violent up until recently to foster that kind of development.
The Fermi Paradox seems to have captured a lot of interest from people who like sci-fi and want to think about all kinds of fantastic ideas on why we appear to be alone. Is there a Great Filter? Is this a simulation? Are we in some kind of super-advanced stellar nursery? It's like nerd sniping (https://www.xkcd.com/356/) for a particular sort of nerd.
I know you're really not supposed to tell people they need to read the article on HN, but the paper underlying the article may be the least understood primary source I've ever seen posted to Hacker News. (This beats out the previous record holder, monad tutorials based around an actively incorrect metaphor.) This is not just a standard reiteration of the Fermi Paradox with somebody's new numbers pulled out of the air. It is a legitimately interesting analysis of the problem as a whole.
Read the article and/or the underlying paper, carefully, before just reciting the Standard Cant Against the Fermi Paradox, OK? (And downvoting the only person giving a decent explanation of it.) The Standard Cant is encompassed and superseded by the paper in question, with mathematics.
If you accept this paper’s conclusions, all the rest of the discussion here is about science fiction. There’s nothing about the theory or evidence that demands either explanation or refutation.
And the one person who actually lays that out is being downvoted for, what, being too explainy? This is bizarre.
The Drake equation stops at simply releasing detectable signals into space.
The Fermi paradox assumes that interstellar travel will be cheap enough and fast enough to make traversing the galaxy a given. Yes, given a few million years, Von Neuman probes can span the galaxy.
Ok. And? We, as a species, have a hard time thinking beyond a handful of years. Now we're talking about projects that have a time scales orders of magnitude in duration than anything we've even thought about doing before.
I can't really get further than that on the Fermi paradox (or a couple of related ones) because I don't buy the premise to start with. Like the probability that we're in a simulation being likely. It assumes that we will have the power/understanding to simulate reality. I question that assumption. I don't think it's a given.
https://pchiusano.github.io/2018-04-21/evolutionary-methods....
So intelligence isn’t a fluke adaptive trait, it’s something that evolution tends toward. While I think it’s possible for evolution to get stuck (and perhaps this is very common on other planets or even on earth if we could replay the tape), it does have an arrow pointing in the direction of intelligence.
There is no evidence in biology (as of yet) that evolution tends towards human-like intelligence. There have been complex life forms on Earth for hundreds of millions of years now, but humans are the first and only species to begin approaching a Kardashev Type I civilization -- and we're still less than 75% of the way there.
Looking at it purely statistically, that gives you 1 intelligent species out of about a billion over our planet's history.
Another really neat way to look at it is in terms of time. If you were to choose any random moment in Earth's history up til now, what are the chances that you would find anything resembling an industrial civilization? About 1 in 20,000,000. Which is to say, as a first-order approximation, we might need to closely examine 20 million extrasolar Earth-like planets before we find one with evidence of a civilization like our own.
The latest anthropological research is finding ways to measure the intelligence of our prehistoric ancestors through the size of their carotid arteries (http://theconversation.com/how-our-species-got-smarter-throu...). Other research has linked the development of hominid intelligence to meat consumption (https://www.berkeley.edu/news/media/releases/99legacy/6-14-1...) and the development of civilization to cheese and dairy consumption (https://www.motherjones.com/environment/2015/04/cheese-envir...).
It's not clear that these changes were driven by evolution, i.e. that "evolution made us smart". Rather, there appears to be a confluence of environmental and genetic factors that developed intelligence as a side-effect.
Up until very recently (say 70,000 years ago), intelligence wasn't even a trait that afforded us any special advantages over our environment. If you follow the Toba theory, there was a massive ecological disaster that applied a significant selection pressure on early humans, and the use of tools and fire may have enabled some members to survive while others died out. And even then, we didn't really start to subjugate our environment until about 12,000 years ago.
So I think we have some survivorship bias in our thinking about the evolution of intelligence. When someone says that evolution naturally leads to intelligent species, I just don't see the evidence for it. Evolution had over a hundred million years of complex, highly-adapted, large fauna to work with, but the dinosaurs didn't build skyscrapers.
Something that I don’t think is well known is how likely it is that evolution will get stuck or reach equilibrium (how often will the pebble get stuck), but I think it’s wrong to say there is no long term tendency.
Also see this other post which talks more about this, see the Getting Stuck section - https://pchiusano.github.io/2018-04-14/intelligence.html
On an intergalactic timescale humanity has only been around for the blink of an eye. So probably not long enough for a civilization that operates on cosmic scale heartbeats to have noticed us yet. When they do though, they might cast off a gamma ray burst in our direction and sentence us to death, checking back to see the carnage several lightyears later, just like they have done with so many other planets teeming with life.
They have made a critical error though: they are entirely too late. They should have done it when we were little more advanced than the beasts who graze on the grasslands. We are now on the brink of exponential technological advancement. By the time they fire off their attack we’ll see them coming and have time to prepare. They will have given away their position, and by the time they look for the dust of what was once our home they will find a hundred new starships and space stations, expanding rapidly away but a great portion moving closer in an ominous pattern.
Then they will realize what they have done. This time, they messed with the wrong species. And then our message will arrive.
As they look at each other right to left and left to right with some alien expression of panic, a malevolent vibration will carry the voice of humanity unified in a way that it has never been before. This will not be the peaceful, optimistic greeting of our Voyager. This will be something unmistakable in it’s intent, something that can only be promised by a civilization that’s been killing itself and nearly killing it’s own planet for all it’s existence, and now thirsting for revenge with a rage handed down from generation to generation. Whenever these beings sleep, if they must sleep, they will be haunted with echoes of our message, still ringing in their heads loud and clear: "We’re coming for you—motherfuckers."
We slowly make empirical progress on the ranges. For one thing, we now know how many stars in the immediate neighborhood have planets: the vast majority. We now know that the prospects for water/organic based “life” look pretty good in our neighborhood: there are in the range of half a dozen prospects in our solar system. We might nail that one down a bit more within a few decades. We just need one hit on Enceladus, Europa, or Mars.
Until contact is confirmed, it seems the question comes down to two big problems: (1) It took 3-4 billion years for life on earth to evolve from first replicating molecules to “intelligent life.” Our species is ≈ 200,000 years old. That represents 1/23000th the age of the earth.
(2) We have had “radio” (radiotelegraphy) for a little more than one century. That represents 1/46 millionth the life of the planet.
Assuming humans survive for quite a while longer, what are the chances that another species—say, within 1000 light years of us—will be using “radio” (EM communication) at the same time? Even if our two species each survive a million years, the chances we appear at the same time are slim. A million years represents 1/4600th the life of our planet.
On a positive note, there are in the range of 16 million stars within 1000 light years of earth.
The Fermi Paradox presumes much: intelligent life is destined to evolve on suitable planets; intelligent life survives the filters (my doomsday money is on human pollution, ye olde shite problem); EM communication or star travel is a logical outcome of intelligent life. All of these seem a bit dubious to my limited mind.
On the other hand, almost by definition, a starship is immortal. If humans ever achieve a viable industrial infrastructure, at say, Jupiter, we will have already overcome many of the obstacles of traveling to Alpha Centuri. A self-contained, self-repairing, self-propulsing “vehicle” has to avoid collision, of course.
Here, my money bets first contact will be, or has been with machines.
[1] http://adsabs.harvard.edu/abs/1985Icar...62..518F [2] https://en.wikipedia.org/wiki/Fermi_paradox#Criticism_of_log...
We are outsider ones in this Fermi Paradox extrapolation. We are very far from being able to do interstellar travel, specially in scale, tripulated, or thinking in some way of colonization, even for our closest star system. Like with the weddings, we are extrapolating without knowing anything about how it is really in practice interstellar travel and colonization, specially in big scale.
And more than just about physics, it assumes more things about intra/inter alien culture. They must expand as much as they can, and they must do visible for everyone things (dark forest? nah), and interstellar travel/colonization is possible and desirable... those, besides the Drake equation, are the axioms of it. And they may not be true or at least give another big factor to consider in the Drake equation.
Not knowing is not equal to knowing that not. You must leave space for things that you don't know that you don't know.
this makes no sense at all: whether or not there is a fermi paradox absolutely depends on the parameters "we can argue about"
IMHO the Fermi paradox has one flawed assumption: that interstellar travel for the purposes of colonization would be possible and desirable. If this is not the case then there is no paradox, everybody is in their solar system happily doing whatever it is they do all day.
Is it even worth it?
As to self replicating probes that's freaking dangerous. Get something wrong and the universe becomes a very hostile place.
PS: In terms of cost consider the % of humanity's GDP spent on SETI projects. Now consider those at least have the possibility of some benefit in your lifetime. Extra Solar probes are unlikely to get much in the way of resource investment from most civilizations.
That means sending people out.
We would be sending people on one-way trips, for better or worse. You'd likely never hear from them again.
As to just sending out Bracewells to say "Hi", why? Once again, the return on a response is very long and not guaranteed. And without a response, what's the point?
The point was that the galaxy should be filled with whomever figured out how to colonize distant star systems, even if it takes a 10,000 years for a colony world to get to the point where it can send out the next wave of interstellar colonizers, that's a drop in the bucket for a galaxy that is billions of years old.
Which requires the probe to return information.
> because it's interesting to learn about others
Which requires the probe to return information.
> to trade technology, philosophy, science, and media
All of which, and say it with me, requires the probe to return information.
At the speed of light, that return will take four years from the nearest star.
> If just one alien civilization sent out a Bracewell probe a century but started back when the dinosaurs were around they could have launched a million probes by now.
And if 'if' were a skiff, we'd all take a boat ride.
What is the benefit of launching one such probe? Especially knowing that your next launch is in 100 years. Voyager, after about 40 years, is just barely out of our solar system.
Voyager is broadcasting at 19 watts and we're barely getting that signal here. And it takes 16 hours.
So instead of contemplating what would happen if hypothetical civilizations with hypothetical technology would do for hypothetical reasons, think about what we can and would do right now with our technology.
"People" can be made pretty small if all you're sending is DNA and robots to grow them.
"If aliens exist, they would send tight-beam radio communications on this exact frequency (because that's the one that we'd choose!), in a format that we could recognize as an attempt to communicate (probably English, because we all speak English! Or maybe Morse code), and keep spending resources doing it for however many thousands or millions of years it took for us to notice." Even we don't even do that. Most of our radio transmissions now are short-range bluetooth, wifi, cellular, or satellites pointed at the planet. Our broadcast signals, though some might be strong, are attenuating in cubic space and all mixed together containing all channels and stations - white noise and static at best. We just assume that if they're not speaking our language in our formats, they're not really civilized/advanced.
"If aliens exist, they would have conquered the entire galaxy by now, because that's what we'd do!" I've lived here for years and haven't tried to conquer my neighbors and have no intention of doing so. Yet we assume any sufficiently-advanced aliens must be violent.
"If we couldn't conquer it straight away, we'd at least send self-replicating robots to claim every planet! So if aliens existed, of course they would have done that!" They may not be self-replicating, but any of us could buy drones and send them to claim undeveloped plots of land that we couldn't use. Yet we don't. It'd be pointless. But we assume any sufficiently-advanced aliens must be selfish.
"We've been ripping every resource out of the planet as fast as we can and polluting as much as possible to maximize profits and shareholder value. If aliens exist, they would do the same and even go as far as creating Dyson spheres!" Well yes, we do destroy our environment. But some of us have realized that it is a bad idea to do that and we should probably ramp it down, rather than go to the full extreme of destroying our entire solar system. Yet we assume any sufficiently-advanced aliens must be greedy.
I don't really think it's a paradox mainly because I don't have that underlying assumption that all aliens must act like the noisiest, greediest, most violent and self-absorbed humans of the 20th century. Perhaps the paradox is that we expect all civilized life in the rest of the universe to be as bad as the worst of us, and it's just not, and we don't have an explanation for that yet.
From all the life that has evolved on earth, from bacteria to trees (to clever octopus) to humans, a very small percentage of that life evolved to create a signal that is detectable far away (humans/radio waves).
I don't really know how to factor this into the paradox, but based on the above, it seems so possible to me that life widely exists but it is simply a miniscule % that has evolved in such a way to use electromagnetic energy in a way that is detectable by us today.