14 ms·

Dissolving the Fermi Paradox

113 points by monort 8y ago

mchahn 8y ago
Can some tell me what the "{\em ex ante}" I see in several places means?
jpm_sd 8y ago
TL;DR - It's not a paradox, because we're probably alone. Kind of a letdown!
- amelius 8y ago
  > because we're probably alone ... in the observable universe.
  - mikeash 8y ago
    Which is another way of saying “within our light cone,” and anything outside it might as well not exist as far as we’re ckncerned.
- ssijak 8y ago
  How did you/they calculate that probability of being alone? Anybody who tries to slap some number on such things as the probability for life to emerge is dishonest at least.
  - mdpopescu 8y ago
    That's the whole point of Michael Crichton's rant in "Aliens caused global warming" [1] [1] https://www.heartland.org/publications-resources/publications/aliens-cause-global-warming-a-lecture-by-michael-crichton https://www.heartland.org/publications-resources/publication...
  - amelius 8y ago
    Imagine a two-dimensional grid of squares, where all the squares are randomly chosen to be either black or white. Imagine that somewhere in this grid there's the appearance of a smiley in a 12x12 rectangle. How would this smiley compute if it's alone in the grid, and how close the nearest other smiley can be expected to be?
- dosshell 8y ago
  And some numbers from the paper: > we find a substantial probability that we are alone in our galaxy, and perhaps even in our observable universe (53%–99.6% and 39%–85% respectively). > ’Where are they?’ — probably extremely far away, and quite possibly beyond the cosmological horizon and forever unreachable.
- jandrese 8y ago
  The Drake equation is the epitome of garbage in garbage out. Trying to draw a line using a single data point. There was recent news from NASA about the discovery of organic molecules on Mars and the possibility of life there at some point in the past. Discovery that life once existed on Mars would blow up the assumptions in the Drake equation. As for the Fermi paradox I'm still of the opinion that its solution is simple but depressing: Interstellar travel is so difficult that by the time you're capable of it you don't need it anymore, and even when you're capable of it you still don't get very far outside of your stellar neighborhood. Unlimited power systems, reactionless drives, and FTL travel (or even high-c travel) are depressingly impossible. And then the cold hand of entropy and the aggregate chance of disaster make it extremely dangerous to even attempt. Basically without Sci-Fi propulsion/power you end up traveling at an interstellar snail's pace, and the longer the trip the more likely it is that a random meteorite smashes through your vessel, or you simply run out of spare parts and materials to make them, and the amount of fuel you need to just keep the lights on becomes enormous. If you can build a starship that can travel between solar systems with our current understanding of physics, then you can build orbital colonies for basically unlimited living space much much easier. For one, they can be powered by solar cells instead of needing to carry fuel. It's not like we are going to run out of raw materials either. Even restricting yourself to the belt the amount of material available would last basically indefinitely. Worst case you can start breaking up moons. So even in a universe full of life everybody is alone. Especially if you think about how genetic algorithms tend to get hung up on local maxima, so lots of planets waste millions of years with dumb dinosaurs with no space program or radio telescopes.
  - TeMPOraL 8y ago
    Also, VR. I already fear the future of humanity is not exploring strange new worlds, but creating virtual ones, and converting the solar system into more computronium. (And the weird thing about that is that I feel it's a bad thing for some reason, but I can't articulate a coherent argument against it.)
    - greglindahl 8y ago
      There are a bunch of scifi novels that explore the issue, and most of them feature bad things that result.
transfire 8y ago
"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." There is no way we are alone.
- Buttons840 8y ago
  Every once in a while we see a headline that says something like "There are more planets than we previously thought", or "There are more galaxies than we previously thought". When people see these they often conclude that the odds that life exists elsewhere are greater than previously thought, but it's also perfectly logical to see those headlines and concludes that the odds of life forming are lower than previously thought, because (per Fermi) "Well then where is everyone?" Look at the math: odds of life existing elsewhere = (10^n planets) / (10^(-m) odds of life forming on a planet) We don't know what `n` and `m` are. It may be that `m` is much larger than than `n`. Yes, the number of planets is very large, but the odds of life forming is apparently very small. It may be that there is a very large number of planets, but a very very very very small chance that life would form on a planet.
  - bena 8y ago
    We're still working out how to get to Mars. Currently it will take close to a year. The longest time someone has spent in space has been just over a year. It is not easy. It is not quick. Even if we travel at the fastest possible speed, it takes 4 years to get to the next star. So, where are they? Too far away to reach. The assumption that these problems are possible to overcome is a big one.
- jobigoud 8y ago
  The Universe is old. Really old.
ISL 8y ago
If the argument stated above is correct, there is an awful waste of space. (Thanks, Carl!) There is nothing in physical law to suggest that here is substantially different from anywhere else in the universe. To believe that here is manifestly different from every other place in the universe is a really surprising claim.
- mdpopescu 8y ago
  First, we know with absolute certainty that here is substantially different from anywhere else: we know there's life here, we haven't found life anywhere else. (And the null hypothesis is that we haven't found it because it doesn't exist.) Second, it's a waste of space only if 1) it was created on purpose and 2) the purpose wasn't "to allow us space to expand". If either of those is false, I don't see how it can be called "a waste of space".
  - ISL 8y ago
    First, we know with absolute certainty that here is substantially different from anywhere else: we know there's life here, we haven't found life anywhere else. I'll take the other side of that bet. What odds are on offer (10^15:1? 10^80:1?)?
    - Anderkent 8y ago
      Wait, are you saying you'll take a bet where you pay 10^15 to 1 if we do not find life out there? I'll take you up on that for $0.01 on my side.
  - goatlover 8y ago
    > First, we know with absolute certainty that here is substantially different from anywhere else: we know there's life here, we haven't found life anywhere else. We haven't even ruled out life existing on Mars or under the ice of Europa, let alone X light years away.
  - gnaritas 8y ago
    > First, we know with absolute certainty that here is substantially different from anywhere else: we know there's life here, we haven't found life anywhere else No we do not. We haven't looked anywhere else, we don't yet really have that ability. There's no reason at all to believe this place is special.
light_hue_1 8y ago
It's "papers" like this by people that are either clueless or malicious that make everyone pine for the pre-arxiv days. Everyone considered this option. From the very first day the paradox was posed. We don't know the parameters well, it's within our margin of error that no one else is out there, so it's an option. This is such an absurd claim to take as your own that it's literally on the wikipedia page! It's also extremely shortsighted in order to get media attention. This resolves nothing about the paradox. What about the universe prevents other intelligent species from existing nearby? Sure, it's within our margin of error, but where is this coming from? Too few planets, too little abiogenesis, etc? Many factors or a single one? Is our existence simply a consequence of the fact that we're here therefore the dice must have landed well for us? Or is there something fairly unique about our solar system / planet / species / etc. That's the real scientific question that keeps people up at night.
- jawns 8y ago
  > This is such an absurd claim to take as your own that it's literally on the wikipedia page! Confirmed: https://en.wikipedia.org/wiki/Fermi_paradox#Extraterrestrial_life_is_rare_or_non-existent https://en.wikipedia.org/wiki/Fermi_paradox#Extraterrestrial...
- mirimir 8y ago
  Agreed. This is just picking parameters consistent with no detection of extraterrestrial civilizations. The point of the Fermi paradox is that it's a stretch to assume such parameters. It's not prediction about extraterrestrial civilizations collapsing or whatever. It's just an alternative to consider. And perhaps a warning about shouting at the Universe. Although it's probably too late to fret too much about that.
  - jerf 8y ago
    The article is not about picking parameters. The article is one meta layer up from that; they examine the distribution of parameters. I can't guarantee this is novel paper in general, but it's not something I've seen treated this formally before. I mean, it roughly conforms to what I've been saying for a while, but I only worked the math very intuitively and in a manner that could have been flawed, so I get no credit. They've worked it formally and put it on a solid basis. Plus as we adjust our probability ranges in the future, the analysis can be re-run with new numbers easily and produce concrete, or at least, concretely-vague answers, instead of vaguely-vague intuitions.
shawn 8y ago
It has always seemed arrogant to think that aliens exist anywhere within our galaxy. Look at how many galaxies are out there. Now realize that the universe extends far beyond our Hubble sphere. We can’t hope to colonize even a fraction of 1% of our galaxy, even with wildly futuristic technology. There is one option, though: Become our own aliens. If we set up colonies separated by time and distance, we will culturally diverge within a century, and genetically within a few millennia-ish.
- Cthulhu_ 8y ago
  What if we are the aliens though?
  - ballade 8y ago
    Panspermia?
    - mirimir 8y ago
      Maybe, but not necessarily even that. The flow of chemical evolution that leads to carbon-based life is just so highly likely. We see some key molecules just about everywhere we look out there. And various simulations (physical, not virtual) create nucleic acids, amino acids, fatty acids, carbohydrates, etc. So there's no reason to think that the Earth is special.
      - pbhjpbhj 8y ago
        Something I don't get, people say something along those lines -- that with earth-like conditions, blah-blah, earth-like planets, ... then life! But also experts claim life only arose once on Earth. So, in a place with perfect conditions, the perfect distance from the sun, the perfect atmosphere, perfect trigger, perfect environmental conditions, life only started once! Doesn't that make it so infinitesimally unlikely that even with millions, billions, of planets with the right conditions we still shouldn't expect abiogenesis to occur. The same arguments that make for extraterrestrial life surely stand against the uniqueness of anything. We know things that are unique. Seems like it's mostly faith based assertion.
not_a_moth 8y ago
How can we be expected to take seriously a probability estimate of life being "out there"? Only 10 years ago we discovered how many Earth-like planets are likely in our galaxy (I didn't see this aspect mentioned in the paper...), and they are also calculating a probability of abiogenesis (emergence of life), which, while I'm not an expert, seems highly speculative.
- Anderkent 8y ago
  Why can't you estimate probability of something speculative? Of course it must be speculative if you're talking probabilities; otherwise you'd just know if the life is out there or not. If the assumptions are very speculative, you just end up with very wide probability distributions, which is exactly what the paper argues for.
carry_bit 8y ago
Related slides: http://www.jodrellbank.manchester.ac.uk/media/eps/jodrell-bank-centre-for-astrophysics/news-and-events/2017/uksrn-slides/Anders-Sandberg---Dissolving-Fermi-Paradox-UKSRN.pdf http://www.jodrellbank.manchester.ac.uk/media/eps/jodrell-ba...
poppingtonic 8y ago
The conclusion of this paper is, paraphrasing, "We should stop using point estimates for what should be distributions. When we do that, we get much lower bounds and have a better chance at being more precise, whether or not we are alone." It opens up avenues for more questions, which is the correct stance given how little we know.
PaulHoule 8y ago
Ecosystems are limited by the availability of water, not sunlight. Also there are more "habitable" places in the universe which are underground oceans (the default condition outside the frost line) as opposed to a tiny fraction of rock worlds which have to parametrically fine tuned to have water -- ex. there are 10-20 worlds that have underground oceans in our own solar system. Why would a spacefaring civilization care about dry worlds inside the frost line? The most absurd thing about "Battle: Los Angeles" is not that aliens would come to Los Angeles (as opposed to Detroit) to steal water, but that they would come to a planet which has a thin layer on the surface as opposed to being just a run-of-the-mill dwarf planet or asteroid or comet or whatever you call it that is closer to 50% water. If civilizations of the dark had deuterium fusion they might see very little reason to mess around with the puny resources to be found close to a star. It's entirely plausible that a generation "starship" could live off the land and hop from comet to comet to the next star in 10,000 years but probably the crew would lose interest long before the first millenium.
- TeMPOraL 8y ago
  > The most absurd thing about "Battle: Los Angeles" is not that aliens would come to Los Angeles (as opposed to Detroit) to steal water, Hey, they landed near all major coastal cities; the movie was just following one group of soldiers fighting off one part of the invasion force. > but that they would come to a planet which has a thin layer on the surface as opposed to being just a run-of-the-mill dwarf planet or asteroid or comet or whatever you call it that is closer to 50% water. Fair enough. Disclaimer: I really liked the movie and wish there was a sequel made. EDIT: My guess would be that the alien military tech was running off water (probably hydrogen/oxygen), so they started the invasion on the coasts to have essentially unlimited supply of water, but the actual purpose for the invasion was something else entirely. The "aliens need our water" hypothesis was AFAIR proposed by some talking head in the movie, not stated as in-universe fact.
  - PaulHoule 8y ago
    I liked the movie too, not so much as science fiction but in how the relationship is developed between the staff sergeant and the junior officer.
psychometry 8y ago
Does anyone else find this question totally uninteresting? There's no discussion to be had about this paradox that doesn't devolve into an N=1 predictive model.
- goatlover 8y ago
  I find it interesting because if N=1, then we're an incredibly statistical fluke, and yet there's no reason to suppose that our solar system or planet is that much of an anomaly.
  - vertexFarm 8y ago
    I feel like this is about the same as wandering out into the antarctic pole of inaccessibility, whispering "is anyone out there" one time in 1974, waiting a couple minutes, and then pondering on how it's such an incredible statistical fluke that nobody has responded.
  - psychometry 8y ago
    Maybe for me the issue is that since N=1, we have nowhere near enough information to construct reasonable priors on the equation's parameters. This makes the variance in the outcome explode. The ballpark is so huge that basically any interpretation is fair game.
gmuslera 8y ago
The reasoning seem to be "as we don't have enough data, lets conclude whatever I want". The Fermi paradox assumes that if there are aliens more advanced than us somewhere for a long time, they should be here by now. Maybe more advanced technology enables interstellar travel (maybe not, maybe is not practical at all), maybe they may not have all our motivations (expansion, technological advancement in our own focus, exponential growth, etc), maybe they don't want to expand or announce themselves because they went cyber or try to pass unnoticed in the dark forest, or things that we can't even imagine yet, as we are not advanced enough. We just don't have enough data to give a meaningful answer. And maybe never will. The only way to decide if we are alone in the universe or not is actually finding someone else. But with so much outside our physical or practical line of sight we can't just say that there is no one else because we didn't see anything.
- jobigoud 8y ago
  When talking about the Fermi Paradox it's not about what this or that extra-terrestrial civilization might do. It's about what none of them is doing. When you say "maybe they don't want to expand", if you want this to explain the paradox, you actually mean "none of them want to expand". Because if just one did, we would see it.
  - gmuslera 8y ago
    Is not "none of them" but "all the ones that reached certain knowledge level", after you know something, you avoid expanding or showing yourself. The dark forest idea comes from Liu Cixin Three Body Problem trilogy, if you show yourself you risk being destroyed by even more powerful civilizations that are hidden in the dark. And they are hidden because are afraid that the same happens to them, with a third one or with the one they destroyed after they advanced enough. It is not the only possible reason, just one of the possible things that we don't know (or even don't know that we don't know) that can disprove or at least atenuate enough the paradox hypothesis. Can be like explaining a caveman why you can't make a building high enough to reach the moon, so far he knows would be doable and even desirable for us, so why we didn't built one yet?
  - 8y ago
btilly 8y ago
I have trouble calling it a paradox, because there is nothing that needs explaining in my view. Just throw in the fact that known fudge factors are important, and throw in the fact that there are more fudge factors that we don't know. For example the traditional Drake equation doesn't include as a major factor "large moon that stabilizes the axial tilt over evolutionary time". And yet that seems to be needed and at least somewhat rare. The traditional Drake equation doesn't include as a major factor "life not wiped out by a supernova over evolutionary time". And yet per http://earthsky.org/astronomy-essentials/supernove-distance http://earthsky.org/astronomy-essentials/supernove-distance there are estimates that this might happen on average once per 15 million years. From the Cambrian explosion to the present is around 540 million years. The odds of that forbearance is on the order of 7 billion to 1 against. How much does THAT change the Drake equation?
- jobigoud 8y ago
  It doesn't have to include these specifics. They are just sub-factors contributing to higher level factors. Your first is covered by "fl, the fraction of those planets that actually develop life", and your second is covered by "fi, the fraction of planets bearing life on which intelligent, civilized life, has developed". What you are saying seems to be the same as OP. It's not a paradox because the chances are insignificant, so we are indeed alone.
- stephenwinter2 8y ago
  I agree, I also can't see a paradox in terms of nature. And I would like to add an aspect of sociology (sociology is rarely discussed at this topic): Given mankind's industrialization period and decline of the ecosystem is normal it takes longer to get to an exoplanet than to ruin it. - So, what interstellar space travel really would be is this: The living mankind on Earth gives up itself and its home planet to spread the genes of those who plan its demise. http://www.hashsign.eu/html/blog/dominance/hadfield-hawking-eugenics-and-interstellar-space-colonization.html http://www.hashsign.eu/html/blog/dominance/hadfield-hawking-... My answer to the Fermi Paradox is this: These bastards shouldn't get away with it.
jackconnor 8y ago
I feel like if aliens come they might keep themselves hidden, rather than announce their presence. If so, it could be Fermi was right, we just haven't seen the evidence of it yet, since the Fermi Paradox presupposes that their should be intelligent life and the we actually can point to evidence of it.
sbensu 8y ago
Related recommendation: this podcast episode[1] was very good, covered many solutions to the Fermi Paradox, and discussed the OP's article. [1] http://rationallyspeakingpodcast.org/show/rs-203-stephen-webb-on-where-is-everybody-solutions-to-the-f.html http://rationallyspeakingpodcast.org/show/rs-203-stephen-web...
Sniffnoy 8y ago
I'm going to repost the same comment I made on Reddit: This is quite interesting. It certainly sounds like this does dissolve the Fermi paradox, as they say. However, I think the key idea in this paper is actually not what the authors say it is. They say the key idea is taking account of all our uncertainty rather than using point estimates. I think the key idea is actually realizing that the Drake equation and the Fermi observation don't conflict because they're answering different questions. That is to say: Where does this use of point estimates come from? Well, the Drake equation gives (under the assumption that certain things are uncorrelated) the expected number of civilizations we should expect to detect. Here's the thing -- if we grant the uncorrelatedness assumption (as the authors do), the use of point estimates is entirely valid for that purpose; summarizing one's uncertainty into point estimates will not alter the result. The thing is that the authors here have realized, it seems to me, that the expected value is fundamentally the wrong calculation for purposes of considering the Fermi observation. Sure, maybe the expected value is high -- but why would that conflict with our seeing nothing? The right question to ask, in terms of the Fermi observation, is not, what is the expected number of civilizations we would see, but rather, what is the probability we would see any number more than zero? They then note that -- taking into account all our uncertainty, as they say -- while the expected number may be high, this probability is actually quite low, and therefore does not conflict with the Fermi observation. But to my mind the key idea here isn't taking into account all our uncertainty, but asking about P(N>0) rather than E(N) in the first place, realizing that it's really P(N>0) and not E(N) that's the relevant question. It's only that switch from E(N) to P(N>0) that necessitates the taking into account of all our uncertainty, after all! [Note afterward: Over on Reddit, hxka points out that that should be P(N>1), not P(N>0). Or really it should be P(N>1|N>0)...]
carapace 8y ago
We're in quarantine. To other life forms humans look like H.R. Giger's xenomorph aliens from the movies. We're obviously intelligent, yet we absolutely refuse to communicate with other life forms. we're not even interested in the possibility. We consume other organisms with rapacious abandon, converting them into more of ourselves as fast as we can. We are strip-mining the oceans of protein, our chattel livestock out-mass all other land animals by several times, and still we consume. We clearcut forests leaving patterns visible from space. We cover everything with asphalt and concrete to create huge sprawling nests that are inimical to life other than our own (and a few species that can live with us.) Again, this is clearly visible from space. From orbit we look just like a disease. There's a place in Washington (state), a lake, where the UFOs take off and land (underwater) and the cheeky fuckers will wave back at you from windows in the ships. We're not alone. We just suck.
- taylorswift_ 8y ago
  where is this lake in WA state? have you been there? are you reptilian?
  - carapace 8y ago
    > where is this lake in WA state? I' don't know. Even if I knew I wouldn't say in a public forum like this, it would be irresponsible. > have you been there? No. If I wanted to talk to aliens I wouldn't go rubbernecking at them like a yokel. > are you reptilian? We're all reptilian. ;-) https://en.wikipedia.org/wiki/Triune_brain https://en.wikipedia.org/wiki/Triune_brain https://en.wikipedia.org/wiki/Recapitulation_theory https://en.wikipedia.org/wiki/Recapitulation_theory The "reptilian" thing is a human psychological issue, there are no reptile aliens secretly ruling Earth.
    - taylorswift_ 8y ago
      but how do you know it exists if you've never been there? who told you? > there are no reptile aliens secretly ruling Earth. perhaps not ruling it...
jl2718 8y ago
I would rephrase the question as: What are reasonable bounds on the number of intelligent civilizations, given that we have observed exactly one in the archeological record of our own planet, and no others elsewhere with current technology? So, tiny sliver of time over billions of years, and communications technology that only reaches to a few nearby stars. Trying to use probability of certain chemistry is, I think, highly subject to errors and failure to consider some alternative possibilities. Life itself, however, is a totally different equation because it’s nearly as old as the earth. This might suggest that there is a lot of it out there.
8bitsrule 8y ago
expectation that the universe should be teeming with >intelligent life<. It's only a paradox if you're capable of entertaining such an expectation. Based on my life experience, I'd estimate the probability is about the same as finding a bottle of my favorite drink sitting on the doorstep.
FreekNortier 8y ago
They are here just not in a way most people would think. When you are ready to know you will know.
chmike 8y ago
In my opinion, takling the ET existence using the drake equation is not efficient because it boils down to estimate or guessing values. I favor the following reasonning. For simplification, let consider the universe as homogene. Now, let p be the probability that life emerges in one unit of time and space. (1-p) is the probability that life does not emerge in the unit of volume and space. If v is the number of volume units in the universe and t the age of the universe in unit of time, then the probability that life never emerges in the universe is (1-p)^(v * t). If p is bigger than zero, this probability will tend to 0 with a growing v and t, regardless of the magnitude of p. This always converges to 0. Soon or later, life will emerge in the universe as long as it can emerge spontaneously. What is the probaility that our solar system is the only place in the universe where life emerged. Let s be the volume of our solar system. That probability is (1-p)^((v-s) * t). Since s is very small relative to v, that probability is very close to the above probability. And with growing v and t this probability tend to zero. In other words the probability that life emerges elsewere in the universe after removing the volume of our solar system is not much affected. It still tends toward 1. This should give you the idea. The only unknown variable is p. But even if we don't know it's value, we can draw two important conclusions from this. 1) it doesn't matter how small p is, soon or later life will emerge. 2) the probability that we are alone in the universe is tending toward 0 with increasing t and v. Could we be the most advanced ? Why discarding the ufological data ? It's time this non-sense and ostrich attitude stops.
tachkotic 8y ago
The time span of human civilization is too small to witness the emergence and extinction of intelligent civilization elsewhere. Universe is really very vast in terms of distance and time.

113 points by monort 8y ago

mchahn 8y ago

Can some tell me what the "{\em ex ante}" I see in several places means?

jpm_sd 8y ago

TL;DR - It's not a paradox, because we're probably alone. Kind of a letdown!

amelius 8y ago
> because we're probably alone ... in the observable universe.
- mikeash 8y ago
  Which is another way of saying “within our light cone,” and anything outside it might as well not exist as far as we’re ckncerned.
ssijak 8y ago
How did you/they calculate that probability of being alone? Anybody who tries to slap some number on such things as the probability for life to emerge is dishonest at least.
- mdpopescu 8y ago
  That's the whole point of Michael Crichton's rant in "Aliens caused global warming" [1] [1] https://www.heartland.org/publications-resources/publications/aliens-cause-global-warming-a-lecture-by-michael-crichton https://www.heartland.org/publications-resources/publication...
- amelius 8y ago
  Imagine a two-dimensional grid of squares, where all the squares are randomly chosen to be either black or white. Imagine that somewhere in this grid there's the appearance of a smiley in a 12x12 rectangle. How would this smiley compute if it's alone in the grid, and how close the nearest other smiley can be expected to be?
dosshell 8y ago
And some numbers from the paper: > we find a substantial probability that we are alone in our galaxy, and perhaps even in our observable universe (53%–99.6% and 39%–85% respectively). > ’Where are they?’ — probably extremely far away, and quite possibly beyond the cosmological horizon and forever unreachable.
jandrese 8y ago
The Drake equation is the epitome of garbage in garbage out. Trying to draw a line using a single data point. There was recent news from NASA about the discovery of organic molecules on Mars and the possibility of life there at some point in the past. Discovery that life once existed on Mars would blow up the assumptions in the Drake equation. As for the Fermi paradox I'm still of the opinion that its solution is simple but depressing: Interstellar travel is so difficult that by the time you're capable of it you don't need it anymore, and even when you're capable of it you still don't get very far outside of your stellar neighborhood. Unlimited power systems, reactionless drives, and FTL travel (or even high-c travel) are depressingly impossible. And then the cold hand of entropy and the aggregate chance of disaster make it extremely dangerous to even attempt. Basically without Sci-Fi propulsion/power you end up traveling at an interstellar snail's pace, and the longer the trip the more likely it is that a random meteorite smashes through your vessel, or you simply run out of spare parts and materials to make them, and the amount of fuel you need to just keep the lights on becomes enormous. If you can build a starship that can travel between solar systems with our current understanding of physics, then you can build orbital colonies for basically unlimited living space much much easier. For one, they can be powered by solar cells instead of needing to carry fuel. It's not like we are going to run out of raw materials either. Even restricting yourself to the belt the amount of material available would last basically indefinitely. Worst case you can start breaking up moons. So even in a universe full of life everybody is alone. Especially if you think about how genetic algorithms tend to get hung up on local maxima, so lots of planets waste millions of years with dumb dinosaurs with no space program or radio telescopes.
- TeMPOraL 8y ago
  Also, VR. I already fear the future of humanity is not exploring strange new worlds, but creating virtual ones, and converting the solar system into more computronium. (And the weird thing about that is that I feel it's a bad thing for some reason, but I can't articulate a coherent argument against it.)
  - greglindahl 8y ago
    There are a bunch of scifi novels that explore the issue, and most of them feature bad things that result.

transfire 8y ago

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." There is no way we are alone.

Buttons840 8y ago
Every once in a while we see a headline that says something like "There are more planets than we previously thought", or "There are more galaxies than we previously thought". When people see these they often conclude that the odds that life exists elsewhere are greater than previously thought, but it's also perfectly logical to see those headlines and concludes that the odds of life forming are lower than previously thought, because (per Fermi) "Well then where is everyone?" Look at the math: odds of life existing elsewhere = (10^n planets) / (10^(-m) odds of life forming on a planet) We don't know what `n` and `m` are. It may be that `m` is much larger than than `n`. Yes, the number of planets is very large, but the odds of life forming is apparently very small. It may be that there is a very large number of planets, but a very very very very small chance that life would form on a planet.
- bena 8y ago
  We're still working out how to get to Mars. Currently it will take close to a year. The longest time someone has spent in space has been just over a year. It is not easy. It is not quick. Even if we travel at the fastest possible speed, it takes 4 years to get to the next star. So, where are they? Too far away to reach. The assumption that these problems are possible to overcome is a big one.
jobigoud 8y ago
The Universe is old. Really old.

ISL 8y ago

If the argument stated above is correct, there is an awful waste of space. (Thanks, Carl!) There is nothing in physical law to suggest that here is substantially different from anywhere else in the universe. To believe that here is manifestly different from every other place in the universe is a really surprising claim.

mdpopescu 8y ago
First, we know with absolute certainty that here is substantially different from anywhere else: we know there's life here, we haven't found life anywhere else. (And the null hypothesis is that we haven't found it because it doesn't exist.) Second, it's a waste of space only if 1) it was created on purpose and 2) the purpose wasn't "to allow us space to expand". If either of those is false, I don't see how it can be called "a waste of space".
- ISL 8y ago
  First, we know with absolute certainty that here is substantially different from anywhere else: we know there's life here, we haven't found life anywhere else. I'll take the other side of that bet. What odds are on offer (10^15:1? 10^80:1?)?
  - Anderkent 8y ago
    Wait, are you saying you'll take a bet where you pay 10^15 to 1 if we do not find life out there? I'll take you up on that for $0.01 on my side.
- goatlover 8y ago
  > First, we know with absolute certainty that here is substantially different from anywhere else: we know there's life here, we haven't found life anywhere else. We haven't even ruled out life existing on Mars or under the ice of Europa, let alone X light years away.
- gnaritas 8y ago
  > First, we know with absolute certainty that here is substantially different from anywhere else: we know there's life here, we haven't found life anywhere else No we do not. We haven't looked anywhere else, we don't yet really have that ability. There's no reason at all to believe this place is special.

light_hue_1 8y ago

It's "papers" like this by people that are either clueless or malicious that make everyone pine for the pre-arxiv days. Everyone considered this option. From the very first day the paradox was posed. We don't know the parameters well, it's within our margin of error that no one else is out there, so it's an option. This is such an absurd claim to take as your own that it's literally on the wikipedia page! It's also extremely shortsighted in order to get media attention. This resolves nothing about the paradox. What about the universe prevents other intelligent species from existing nearby? Sure, it's within our margin of error, but where is this coming from? Too few planets, too little abiogenesis, etc? Many factors or a single one? Is our existence simply a consequence of the fact that we're here therefore the dice must have landed well for us? Or is there something fairly unique about our solar system / planet / species / etc. That's the real scientific question that keeps people up at night.

jawns 8y ago
> This is such an absurd claim to take as your own that it's literally on the wikipedia page! Confirmed: https://en.wikipedia.org/wiki/Fermi_paradox#Extraterrestrial_life_is_rare_or_non-existent https://en.wikipedia.org/wiki/Fermi_paradox#Extraterrestrial...
mirimir 8y ago
Agreed. This is just picking parameters consistent with no detection of extraterrestrial civilizations. The point of the Fermi paradox is that it's a stretch to assume such parameters. It's not prediction about extraterrestrial civilizations collapsing or whatever. It's just an alternative to consider. And perhaps a warning about shouting at the Universe. Although it's probably too late to fret too much about that.
- jerf 8y ago
  The article is not about picking parameters. The article is one meta layer up from that; they examine the distribution of parameters. I can't guarantee this is novel paper in general, but it's not something I've seen treated this formally before. I mean, it roughly conforms to what I've been saying for a while, but I only worked the math very intuitively and in a manner that could have been flawed, so I get no credit. They've worked it formally and put it on a solid basis. Plus as we adjust our probability ranges in the future, the analysis can be re-run with new numbers easily and produce concrete, or at least, concretely-vague answers, instead of vaguely-vague intuitions.

shawn 8y ago

It has always seemed arrogant to think that aliens exist anywhere within our galaxy. Look at how many galaxies are out there. Now realize that the universe extends far beyond our Hubble sphere. We can’t hope to colonize even a fraction of 1% of our galaxy, even with wildly futuristic technology. There is one option, though: Become our own aliens. If we set up colonies separated by time and distance, we will culturally diverge within a century, and genetically within a few millennia-ish.

Cthulhu_ 8y ago
What if we are the aliens though?
- ballade 8y ago
  Panspermia?
  - mirimir 8y ago
    Maybe, but not necessarily even that. The flow of chemical evolution that leads to carbon-based life is just so highly likely. We see some key molecules just about everywhere we look out there. And various simulations (physical, not virtual) create nucleic acids, amino acids, fatty acids, carbohydrates, etc. So there's no reason to think that the Earth is special.
    - pbhjpbhj 8y ago
      Something I don't get, people say something along those lines -- that with earth-like conditions, blah-blah, earth-like planets, ... then life! But also experts claim life only arose once on Earth. So, in a place with perfect conditions, the perfect distance from the sun, the perfect atmosphere, perfect trigger, perfect environmental conditions, life only started once! Doesn't that make it so infinitesimally unlikely that even with millions, billions, of planets with the right conditions we still shouldn't expect abiogenesis to occur. The same arguments that make for extraterrestrial life surely stand against the uniqueness of anything. We know things that are unique. Seems like it's mostly faith based assertion.

not_a_moth 8y ago

How can we be expected to take seriously a probability estimate of life being "out there"? Only 10 years ago we discovered how many Earth-like planets are likely in our galaxy (I didn't see this aspect mentioned in the paper...), and they are also calculating a probability of abiogenesis (emergence of life), which, while I'm not an expert, seems highly speculative.

Anderkent 8y ago
Why can't you estimate probability of something speculative? Of course it must be speculative if you're talking probabilities; otherwise you'd just know if the life is out there or not. If the assumptions are very speculative, you just end up with very wide probability distributions, which is exactly what the paper argues for.

carry_bit 8y ago

Related slides: http://www.jodrellbank.manchester.ac.uk/media/eps/jodrell-bank-centre-for-astrophysics/news-and-events/2017/uksrn-slides/Anders-Sandberg---Dissolving-Fermi-Paradox-UKSRN.pdf http://www.jodrellbank.manchester.ac.uk/media/eps/jodrell-ba...

poppingtonic 8y ago

The conclusion of this paper is, paraphrasing, "We should stop using point estimates for what should be distributions. When we do that, we get much lower bounds and have a better chance at being more precise, whether or not we are alone." It opens up avenues for more questions, which is the correct stance given how little we know.

PaulHoule 8y ago

Ecosystems are limited by the availability of water, not sunlight. Also there are more "habitable" places in the universe which are underground oceans (the default condition outside the frost line) as opposed to a tiny fraction of rock worlds which have to parametrically fine tuned to have water -- ex. there are 10-20 worlds that have underground oceans in our own solar system. Why would a spacefaring civilization care about dry worlds inside the frost line? The most absurd thing about "Battle: Los Angeles" is not that aliens would come to Los Angeles (as opposed to Detroit) to steal water, but that they would come to a planet which has a thin layer on the surface as opposed to being just a run-of-the-mill dwarf planet or asteroid or comet or whatever you call it that is closer to 50% water. If civilizations of the dark had deuterium fusion they might see very little reason to mess around with the puny resources to be found close to a star. It's entirely plausible that a generation "starship" could live off the land and hop from comet to comet to the next star in 10,000 years but probably the crew would lose interest long before the first millenium.

TeMPOraL 8y ago
> The most absurd thing about "Battle: Los Angeles" is not that aliens would come to Los Angeles (as opposed to Detroit) to steal water, Hey, they landed near all major coastal cities; the movie was just following one group of soldiers fighting off one part of the invasion force. > but that they would come to a planet which has a thin layer on the surface as opposed to being just a run-of-the-mill dwarf planet or asteroid or comet or whatever you call it that is closer to 50% water. Fair enough. Disclaimer: I really liked the movie and wish there was a sequel made. EDIT: My guess would be that the alien military tech was running off water (probably hydrogen/oxygen), so they started the invasion on the coasts to have essentially unlimited supply of water, but the actual purpose for the invasion was something else entirely. The "aliens need our water" hypothesis was AFAIR proposed by some talking head in the movie, not stated as in-universe fact.
- PaulHoule 8y ago
  I liked the movie too, not so much as science fiction but in how the relationship is developed between the staff sergeant and the junior officer.

psychometry 8y ago

Does anyone else find this question totally uninteresting? There's no discussion to be had about this paradox that doesn't devolve into an N=1 predictive model.

goatlover 8y ago
I find it interesting because if N=1, then we're an incredibly statistical fluke, and yet there's no reason to suppose that our solar system or planet is that much of an anomaly.
- vertexFarm 8y ago
  I feel like this is about the same as wandering out into the antarctic pole of inaccessibility, whispering "is anyone out there" one time in 1974, waiting a couple minutes, and then pondering on how it's such an incredible statistical fluke that nobody has responded.
- psychometry 8y ago
  Maybe for me the issue is that since N=1, we have nowhere near enough information to construct reasonable priors on the equation's parameters. This makes the variance in the outcome explode. The ballpark is so huge that basically any interpretation is fair game.

gmuslera 8y ago

The reasoning seem to be "as we don't have enough data, lets conclude whatever I want". The Fermi paradox assumes that if there are aliens more advanced than us somewhere for a long time, they should be here by now. Maybe more advanced technology enables interstellar travel (maybe not, maybe is not practical at all), maybe they may not have all our motivations (expansion, technological advancement in our own focus, exponential growth, etc), maybe they don't want to expand or announce themselves because they went cyber or try to pass unnoticed in the dark forest, or things that we can't even imagine yet, as we are not advanced enough. We just don't have enough data to give a meaningful answer. And maybe never will. The only way to decide if we are alone in the universe or not is actually finding someone else. But with so much outside our physical or practical line of sight we can't just say that there is no one else because we didn't see anything.

jobigoud 8y ago
When talking about the Fermi Paradox it's not about what this or that extra-terrestrial civilization might do. It's about what none of them is doing. When you say "maybe they don't want to expand", if you want this to explain the paradox, you actually mean "none of them want to expand". Because if just one did, we would see it.
- gmuslera 8y ago
  Is not "none of them" but "all the ones that reached certain knowledge level", after you know something, you avoid expanding or showing yourself. The dark forest idea comes from Liu Cixin Three Body Problem trilogy, if you show yourself you risk being destroyed by even more powerful civilizations that are hidden in the dark. And they are hidden because are afraid that the same happens to them, with a third one or with the one they destroyed after they advanced enough. It is not the only possible reason, just one of the possible things that we don't know (or even don't know that we don't know) that can disprove or at least atenuate enough the paradox hypothesis. Can be like explaining a caveman why you can't make a building high enough to reach the moon, so far he knows would be doable and even desirable for us, so why we didn't built one yet?
- 8y ago

btilly 8y ago

I have trouble calling it a paradox, because there is nothing that needs explaining in my view. Just throw in the fact that known fudge factors are important, and throw in the fact that there are more fudge factors that we don't know. For example the traditional Drake equation doesn't include as a major factor "large moon that stabilizes the axial tilt over evolutionary time". And yet that seems to be needed and at least somewhat rare. The traditional Drake equation doesn't include as a major factor "life not wiped out by a supernova over evolutionary time". And yet per http://earthsky.org/astronomy-essentials/supernove-distance http://earthsky.org/astronomy-essentials/supernove-distance there are estimates that this might happen on average once per 15 million years. From the Cambrian explosion to the present is around 540 million years. The odds of that forbearance is on the order of 7 billion to 1 against. How much does THAT change the Drake equation?

jobigoud 8y ago
It doesn't have to include these specifics. They are just sub-factors contributing to higher level factors. Your first is covered by "fl, the fraction of those planets that actually develop life", and your second is covered by "fi, the fraction of planets bearing life on which intelligent, civilized life, has developed". What you are saying seems to be the same as OP. It's not a paradox because the chances are insignificant, so we are indeed alone.
stephenwinter2 8y ago
I agree, I also can't see a paradox in terms of nature. And I would like to add an aspect of sociology (sociology is rarely discussed at this topic): Given mankind's industrialization period and decline of the ecosystem is normal it takes longer to get to an exoplanet than to ruin it. - So, what interstellar space travel really would be is this: The living mankind on Earth gives up itself and its home planet to spread the genes of those who plan its demise. http://www.hashsign.eu/html/blog/dominance/hadfield-hawking-eugenics-and-interstellar-space-colonization.html http://www.hashsign.eu/html/blog/dominance/hadfield-hawking-... My answer to the Fermi Paradox is this: These bastards shouldn't get away with it.

jackconnor 8y ago

I feel like if aliens come they might keep themselves hidden, rather than announce their presence. If so, it could be Fermi was right, we just haven't seen the evidence of it yet, since the Fermi Paradox presupposes that their should be intelligent life and the we actually can point to evidence of it.

sbensu 8y ago

Related recommendation: this podcast episode[1] was very good, covered many solutions to the Fermi Paradox, and discussed the OP's article. [1] http://rationallyspeakingpodcast.org/show/rs-203-stephen-webb-on-where-is-everybody-solutions-to-the-f.html http://rationallyspeakingpodcast.org/show/rs-203-stephen-web...

Sniffnoy 8y ago

I'm going to repost the same comment I made on Reddit: This is quite interesting. It certainly sounds like this does dissolve the Fermi paradox, as they say. However, I think the key idea in this paper is actually not what the authors say it is. They say the key idea is taking account of all our uncertainty rather than using point estimates. I think the key idea is actually realizing that the Drake equation and the Fermi observation don't conflict because they're answering different questions. That is to say: Where does this use of point estimates come from? Well, the Drake equation gives (under the assumption that certain things are uncorrelated) the expected number of civilizations we should expect to detect. Here's the thing -- if we grant the uncorrelatedness assumption (as the authors do), the use of point estimates is entirely valid for that purpose; summarizing one's uncertainty into point estimates will not alter the result. The thing is that the authors here have realized, it seems to me, that the expected value is fundamentally the wrong calculation for purposes of considering the Fermi observation. Sure, maybe the expected value is high -- but why would that conflict with our seeing nothing? The right question to ask, in terms of the Fermi observation, is not, what is the expected number of civilizations we would see, but rather, what is the probability we would see any number more than zero? They then note that -- taking into account all our uncertainty, as they say -- while the expected number may be high, this probability is actually quite low, and therefore does not conflict with the Fermi observation. But to my mind the key idea here isn't taking into account all our uncertainty, but asking about P(N>0) rather than E(N) in the first place, realizing that it's really P(N>0) and not E(N) that's the relevant question. It's only that switch from E(N) to P(N>0) that necessitates the taking into account of all our uncertainty, after all! [Note afterward: Over on Reddit, hxka points out that that should be P(N>1), not P(N>0). Or really it should be P(N>1|N>0)...]

carapace 8y ago

We're in quarantine. To other life forms humans look like H.R. Giger's xenomorph aliens from the movies. We're obviously intelligent, yet we absolutely refuse to communicate with other life forms. we're not even interested in the possibility. We consume other organisms with rapacious abandon, converting them into more of ourselves as fast as we can. We are strip-mining the oceans of protein, our chattel livestock out-mass all other land animals by several times, and still we consume. We clearcut forests leaving patterns visible from space. We cover everything with asphalt and concrete to create huge sprawling nests that are inimical to life other than our own (and a few species that can live with us.) Again, this is clearly visible from space. From orbit we look just like a disease. There's a place in Washington (state), a lake, where the UFOs take off and land (underwater) and the cheeky fuckers will wave back at you from windows in the ships. We're not alone. We just suck.

taylorswift_ 8y ago
where is this lake in WA state? have you been there? are you reptilian?
- carapace 8y ago
  > where is this lake in WA state? I' don't know. Even if I knew I wouldn't say in a public forum like this, it would be irresponsible. > have you been there? No. If I wanted to talk to aliens I wouldn't go rubbernecking at them like a yokel. > are you reptilian? We're all reptilian. ;-) https://en.wikipedia.org/wiki/Triune_brain https://en.wikipedia.org/wiki/Triune_brain https://en.wikipedia.org/wiki/Recapitulation_theory https://en.wikipedia.org/wiki/Recapitulation_theory The "reptilian" thing is a human psychological issue, there are no reptile aliens secretly ruling Earth.
  - taylorswift_ 8y ago
    but how do you know it exists if you've never been there? who told you? > there are no reptile aliens secretly ruling Earth. perhaps not ruling it...

jl2718 8y ago

I would rephrase the question as: What are reasonable bounds on the number of intelligent civilizations, given that we have observed exactly one in the archeological record of our own planet, and no others elsewhere with current technology? So, tiny sliver of time over billions of years, and communications technology that only reaches to a few nearby stars. Trying to use probability of certain chemistry is, I think, highly subject to errors and failure to consider some alternative possibilities. Life itself, however, is a totally different equation because it’s nearly as old as the earth. This might suggest that there is a lot of it out there.

8bitsrule 8y ago

expectation that the universe should be teeming with >intelligent life<. It's only a paradox if you're capable of entertaining such an expectation. Based on my life experience, I'd estimate the probability is about the same as finding a bottle of my favorite drink sitting on the doorstep.

FreekNortier 8y ago

They are here just not in a way most people would think. When you are ready to know you will know.

chmike 8y ago

In my opinion, takling the ET existence using the drake equation is not efficient because it boils down to estimate or guessing values. I favor the following reasonning. For simplification, let consider the universe as homogene. Now, let p be the probability that life emerges in one unit of time and space. (1-p) is the probability that life does not emerge in the unit of volume and space. If v is the number of volume units in the universe and t the age of the universe in unit of time, then the probability that life never emerges in the universe is (1-p)^(v * t). If p is bigger than zero, this probability will tend to 0 with a growing v and t, regardless of the magnitude of p. This always converges to 0. Soon or later, life will emerge in the universe as long as it can emerge spontaneously. What is the probaility that our solar system is the only place in the universe where life emerged. Let s be the volume of our solar system. That probability is (1-p)^((v-s) * t). Since s is very small relative to v, that probability is very close to the above probability. And with growing v and t this probability tend to zero. In other words the probability that life emerges elsewere in the universe after removing the volume of our solar system is not much affected. It still tends toward 1. This should give you the idea. The only unknown variable is p. But even if we don't know it's value, we can draw two important conclusions from this. 1) it doesn't matter how small p is, soon or later life will emerge. 2) the probability that we are alone in the universe is tending toward 0 with increasing t and v. Could we be the most advanced ? Why discarding the ufological data ? It's time this non-sense and ostrich attitude stops.

tachkotic 8y ago

The time span of human civilization is too small to witness the emergence and extinction of intelligent civilization elsewhere. Universe is really very vast in terms of distance and time.