14 ms·

There Have Probably Been Aliens

229 points by rosser 10y ago

madaxe_again 10y ago
The most likely reason that nobody seems to be out there is the great filter. The author asks if our civilisation will last millenia or millions of years - but I think a more apt scale would be decades or centuries. It just seems pretty obvious that we have an ever increasing set of opportunities to extinct ourselves, and therefore the probability of a civilisation ending disaster only grows. All the aliens either blew themselves up, starved, or are the kind of incredibly boring, mind-numblingly conservative people you wouldn't invite to a local cluster cocktail party. Oh, either that or civilisations tend to disappear up their own simhole.
- sevenless 10y ago
  The Doomsday Argument implies we've got centuries or less left. https://en.wikipedia.org/wiki/Doomsday_argument https://en.wikipedia.org/wiki/Doomsday_argument
  - madaxe_again 10y ago
    Oh, I think we've decades or years rather than centuries. We always underestimate exponential growth. That's OK, at least it'll make for an interesting existence.
- XorNot 10y ago
  Conversely, by 2025 there might be living humans on Mars (if Elon Musk gets his way). And while that's not enough to form the basis of a backup civilization, I'm somewhat more interested in the effect on global zeitgeist it's likely to have. The feeling of the times is, I feel, an underestimated factor in how democracies pick their priorities - and the early 21st century has been very down on itself trying to figure out practical, post-conflict economic realities.
  - kirykl 10y ago
    The great filter could well be going from single to multi planetary, on a single planet our survival (quite) long term is zero.
  - sangnoir 10y ago
    > And while that's not enough to form the basis of a backup civilization Or that might accelerate the end of civilization due to our inherent tribalism - the US isn't quite a backup of Europe as a 16th century European would have imagined. Who is to say there won't be a Planetary Mutually Assured Destruction? The Expanse (books and TV series) explores some themes around planetary identity & politics in a fictional future where Mars and the outer solar system has been colonized and Earth is seen as a meddling 'old country' by some.
houseofshards 10y ago
Content of the article is pretty information, but worst clickbait title of the year. At the risk of alienating some fraction of HN community (no pun intended), I'm going to say this is what you get when trying to chase the likes of Gawker (again, no pun intended).
- rl3 10y ago
  The irony here is that Gawker's relevant clickbait is actually far superior: http://io9.gizmodo.com/11-of-the-weirdest-solutions-to-the-fermi-paradox-456850746 http://io9.gizmodo.com/11-of-the-weirdest-solutions-to-the-f...
  - mrob 10y ago
    I read a good short story recently about a weird Great Filter: http://www.begoodenough.com/the-great-filter/ http://www.begoodenough.com/the-great-filter/
    - amasad 10y ago
      The first movie that I think plays around with the idea of a Great Filter (not quite; but close) is The Forbidden Planet, a 1950s scifi. The basic idea without spoiling it is that enhancing their own intelligence also made powerful their lizard brain of sorts. I assume freudian psychoanalysis was big in the 50s so they called it the ID in the film.
- deleted 10y ago
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jstanley 10y ago
Title is mild clickbait. There's no evidence for the claim, just a persuasive argument that it's probably true. Interesting nonetheless.
- SonicSoul 10y ago
  it's not mild clickbait. it's the definition of click bait. it states a very controversial conclusion, as if the argument is finally settled, while the body has little new information and fudges around with statistic that "it's likely probable that there is or once was another species".
  - hudibras 10y ago
    Since this is published in a newspaper, the term that is generally used is "headline," not "click bait."
  - hudibras 10y ago
    Since this is published in a newspaper, the terms that are generally used are "headline" or "title," not "click bait."
    - pbhjpbhj 10y ago
      Their media kit claims 78 million online viewers vs. 5 million wealthy newspaper audience. I think more people click to read the article than turn a paper page to read it. Newspapers are online media companies now that happen to also produce limited paper versions. Perhaps I'm missing your point?
- dang 10y ago
  We added "probably" above.
andrewstuart2 10y ago
Probably. Assuming they're correct. Our planet is 12,742km in diameter, yet we've only drilled 12.262km deep [1] (and we were wrong about how hot it was gonna be), and sent a human down ~10.900km [2] (and we still can't decide how deep we've actually been). Do we really think we understand the probability of alien life on another planet that well, given the amount of data we have on those planets, and that we're constantly proven wrong on our own? And yet (either way) I'm not sure it really matters. No human has left our own planet for longer than 437.7 days [3]. Say they're right, though. If an alien race exists, we're still a ways from being able to do anything about it. Unless we can make it there in 1.198 years. If that alien race can make it here, awesome. Let's talk then. If they can make it here and are hostile, then it's been swell. See you on the other side. Probably. [1] https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole [2] https://en.wikipedia.org/wiki/Bathyscaphe_Trieste https://en.wikipedia.org/wiki/Bathyscaphe_Trieste [3] https://en.wikipedia.org/wiki/List_of_spaceflight_records https://en.wikipedia.org/wiki/List_of_spaceflight_records
- nielsbjerg 10y ago
  You got the units of the borehole wrong, it's in meters not kilometers.
  - andrewstuart2 10y ago
    Well, we've certainly drilled more than 12 meters. :-P (Note the decimal point: 12.262km; I just converted to km to keep it consistent with the other measurements I cited) Could be confusing if you're used to the inverse comma/period from what we use in the US (comma=thousands, period=decimal).
    - deleted 10y ago
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    - tluyben2 10y ago
      It is very confusing even though I know this to be the case. It is much harder to parse when the numbers are similar. I do not care which one, just wish everyone would use the same notation. In this case for me it would have been clearer if it said 12262km vs 12262m which is what I would have written. But he :) Interesting comment anyway.
dandare 10y ago
m - km, fix the units
dacompton 10y ago
There have been aliens -- and they don't care about us. To assume that a collection of beings which have obtained the ability to travel amongst the stars would focus their attention on a single species on a single planet is fundamentally selfish. What resources does our earth contain that are not (more easily) obtainable elsewhere? If Drake's equation "holds", then what novelty do _we_ provide?
- j-pb 10y ago
  > What resources does our earth contain that are not (more easily) obtainable elsewhere? If Drake's equation "holds", then what novelty do _we_ provide? Us. If the probability of an intelligent species developing are that low that there might only be a handful of intelligent species in our galaxy then making contact with each of them is extremely interesting if they are as curious as we are.
- Houshalter 10y ago
  There are many reasons alien races would interact with primitives. Morality - they might be utilitarian and desire to relieve the suffering of other sentient beings. Or force their weird alien morals onto them. Competition - we might not be a threat now, but given a sufficiently long time, we could evolve into one. If they really don't care about us, it would cost them very little to exterminate us early.
  - chipx86 10y ago
    I see these mentioned a lot, and sci-fi is big on the latter. The one I rarely see come up is "entertainment." If we were traveling amongst the stars today, with our values and morality as they currently are, and happened upon a world of what we'd consider to be primitive life, we'd probably scoop some up and put them in a zoo, or broadcast them on TV. We'd want to study them, learn what makes them tick, maybe try to see if communication was possible, but in the end, we'd get entertainment value from them. Even if we left them be and studied from a distance, the human race would be fascinated. New life! A new place! We like new things. The news would cover these creatures ("Are they a threat to humanity? News at 11."), they'd be woven into stories and shows and movies in one form or another. If we could safely bring them back, people would want to see them in person. We'd get a lot of entertainment value out of these new creatures. We're a curious race who manages to get bored of spectacular things quickly, which is a large reason we continue to innovate and push forward. There's no way to know for sure what would motive another intelligent race to advance to the point where they'd reach for the stars, but if any of them shared a degree of curiosity, I doubt they'd pass us up if they found us. We'd be something new for them. Maybe we'd end up in their stories, their drawings, their videos, or even their zoos. Maybe they'd be interested in how we smell, or the way we dress and decorate ourselves, or the things that we watch on TV. Our languages, our fights, our culture. Or maybe just the way we go about our business, missing some big cosmological truth that's so obvious to them, as if we're adorable little children. Maybe we'd provide just enough entertainment value to be worth a quick trip. Or a long stay.
apsec112 10y ago
"In other words, given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational." This is terribly silly. It reminds me of the Onion talks: "Step 1: Devise an idea to create a car that runs on compost. Step 2: Create the car. We’ve already completed Step 1. We’re half way there." Increased certainty on three of the seven factors is irrelevant, because 99% of the uncertainty is concentrated in the other four. Specifically, the odds of abiogenesis are ~1/2^n, where n is the complexity in bits of the smallest self-replicator. n is bounded below by ~100 or so (or it would have happened in a lab somewhere), and is bounded above by ~1 million (the smallest existing bacteria), so we know it's somewhere in there. But where? We have only the vaguest guesses. "Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first." "One in 10 billion trillion" sounds like a very large number, and it's put in italics for emphasis, but in information-theoretic terms it's tiny. log2(10^22) is just 73 bits. If all that we know about a number is that it's somewhere between a hundred and a million, saying that X would imply it's higher than 73 (well technically 73 + log2(#incidences of molecular combination), so probably a few hundred) is not a disproof of X, nor really even much evidence against X.
- reso 10y ago
  I had a similar intuition reading the article. I don't think we understand much at all about the probabilities of life forming even under the ideal circumstances. The events that took place on earth could still be one in a billion, or they could be one in an incomprehensibly high number. Nevertheless the progress on the other factors in the Drake equation is very interesting and impressive.
  - raverbashing 10y ago
    > . The events that took place on earth could still be one in a billion, or they could be one in an incomprehensibly high number. I disagree with this. It seems that, from what happened to other planets on the solar system, that nothing happened on Earth too much out of the ordinary. Mars had a similar story (except for the whole Moon coming out of a giant collision), and had water. But maybe it was too small to keep warm for enough time Earth had 5 mass-extinctions, that "reset the game" before we got to humans. Doesn't seem too far fetched to me I really don't buy that Earth is one in a billion unless Mars is one in a billion as well. Maybe one in 1000? One in 100000? And that's limiting intelligent life to what we know. Yes, maybe the ideal speed of chemical reactions (for intelligent life) happen around 273K, or maybe there's another way
jkeler 10y ago
> a probability for civilizations to form of one in 10 billion per planet was considered highly pessimistic I think people underestimate how low probabilities can really be. According to wiki the shortest self-replicating RNA is 165-bases long. Even if you convert all observable universe in RNA this is still not enough for this RNA to form by chance (4^165 is much larger than number of atoms in observable universe).
- jkeler 10y ago
  For people who want an alternative view on this problem: http://biologydirect.biomedcentral.com/articles/10.1186/1745-6150-2-15 http://biologydirect.biomedcentral.com/articles/10.1186/1745...
- perlgeek 10y ago
  > Even if you convert all observable universe in RNA this is still not enough for this RNA to form by chance (4^165 is much larger than number of atoms in observable universe). Which kinda suggests there is either a mechanism that promotes that, or there are other, easier paths to get self replication. Otherwise we mostly likely wouldn't be here.
- qaq 10y ago
  Given enough time anything can form out of random fluctuations if it has >0 probability no matter how small.
  - Houshalter 10y ago
    "Enough time" can easily be longer than the age of the universe. A million monkeys typing on keyboards will eventually write shakespeare. But it will be longer than the universe before they even type a single sentence of it correctly.
    - qaq 10y ago
      It sure can be, but as long as it is less than the expected lifetime of the universe it will still happen. A million monkeys - given that Hamlet contains such long sentences as "He." it will take far less then a minute for them to type a single sentence correctly.
SFJulie 10y ago
No they have not been any aliens until proven so... Science requires a theory and experimental validation. The existence of aliens has been postulated by a crazy monk that also invented the concept of monads. It is much more metaphysics (religious thinking) than physics. It strikes me as odd that most of flawed science is coming with the same flaws as religious thinking.
- coldtea 10y ago
  >Science requires a theory and experimental validation. You'd be surprised. That's 19th century thinking about science, and not really how science works in practice most of the time.
  - SFJulie 10y ago
    Well, that is at least what made relativity and quantum mechanic successful. And yes there has been a lot of flawed science in the XIXth I am aware of it ... like the theory of the ether that Einstein dispelled through experimentation, or the superiority of some "races", or the morpho-psychology...
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throwaway_yy2Di 10y ago
If you parse the article carefully, the entire argument is summarized as "There are more than 10^22 planets, therefore ETI probably exists[ed] if P(intelligent life|planet) > 10^-22". Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first. [...] In other words, given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational.
- ekianjo 10y ago
  That was extremely shallow from the nytimes.
- someguydave 10y ago
  Indeed. Furthermore, the NYT tells us that we are apparently irrational if we believe the probability of advanced life appearing is less than 10^-22.
theaeolist 10y ago
I enjoy these quasi statistical arguments. Can anyone remind me what is the probability that God exists, or that we live in a computer simulation?
- venomsnake 10y ago
  God in the religious sense probably does not exist. On the other hand the existance of type II creatures (that can manage and direct the energy of whole galactic clusters) would not surprise me the least. Their interference with human evolution and deeds would not be shocking too. The quantum machanics behave disturbingly close to lazy evaluation - so this would not be surprising too. Everyone of us is a god to a colony of ants.
  - amasad 10y ago
    Apparently physicists don't agree with the 'lazy evaluation' analogy. I vaguely remember something about the wave function being continuos and computationally expensive and not really an optimization
- qaq 10y ago
  Define God?
  - givan 10y ago
    https://en.wikipedia.org/wiki/Wuji_(philosophy) https://en.wikipedia.org/wiki/Wuji_(philosophy) https://en.wikipedia.org/wiki/Purusha https://en.wikipedia.org/wiki/Purusha
- Houshalter 10y ago
  The probability that God exists depends entirely on your priors. After all we have no observable evidence to consider. I would give it a very low prior, because it's such a weirdly specific belief, considering all the possible origins of the universe. The probability we are in a simulation depends on a bunch of assumptions. Assuming specifically we are asking about a "historical simulation", that the parent universe is identical to ours, we can change the question. Instead ask what is the probability we will someday create historical simulations of our past. Technology certainly seems to advance over time, and the upper limits on computational power are extremely generous. So it's possible we could someday have the technology to do it. Assuming that, then it just depends on the probability you think we will want to make simulated beings. Something about that seems kind of sick and immoral, so I am skeptical of that assumption. But if it is true, then the probability you are in a simulation is extremely high. Because the number of simulated beings could easily be orders of magnitude higher than the number of actual 2016 Earth inhabitants. Provided that many different simulations are run.
sktrdie 10y ago
By pure probability, if we're the first intelligent species here on earth (that is able to build radio communicators) out of what, ~4 billion species that ever existed, what are the odds of us being the first in the entire universe? My logic is that intelligence (as defined above) is clearly rare here on earth where life is prolific, hence by no means a certain development of evolution. I wouldn't be surprised if we're the first in the universe where the conditions are certainly less hospitable for life. This game of probability doesn't only depend on the sample size, but also on what you're looking for. For instance, you can say that if you find a purple grain of sand, and you know there are trillions of other grains, then you'll be sure to find other purple grains. But what if the purple grain has written on it "hello how are you" by sheer chance. You'd probably never find another grain of sand with that same writing. And then you can say, "us being the first is egocentric". Well, but we're the first (on earth) when it comes to building radio stations, so we clearly won that lottery big time. Is it such a stretch to say we won the lottery in the universe as well?
- coldtea 10y ago
  >And then you can say, "us being the first is egocentric". Well, but we're the first when it comes to building radio stations, so we clearly won that lottery big time. Who told you we're "the first when it comes to building radio stations"? There could be 200 other explanations for "radio silence" from advanced civilizations (if they exist).
  - sktrdie 10y ago
    First on earth out of billions of species. That was my hole point... I edited it to make it clearer.
    - coldtea 10y ago
      >First on earth out of billions of species That's par for the course. That's how evolution works. And we're also gonna be the last on earth (we or our evolved successors), because we have the evolutionary upper hand. But that doesn't say much for other planets. We expect them too to have billions of species and a race to produce an intelligent being too.
Houshalter 10y ago
>unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.... the degree of pessimism required to doubt the existence... of an advanced extraterrestrial civilization borders on the irrational. After working with probability theory and combinatorics a bit, you realize probabilities much smaller than this occur naturally all the time. It might be hard for people not familiar with that to appreciate this, and be wowed by such a small number. The thing is that independent probabilities multiply together, and so approach 0 exponentially fast. The probability of winning the lottery is of course very small. But there are so many people, that someone wins a lottery every day. But the probability of winning the lottery twice is really small. The set of people that have won twice is a very small set indeed. And the probability of winning 3 times is so small that we should expect it to be a sure sign of corruption of the lottery, or intervention by supernatural forces. It's also about 1 in 10 billion trillion. It seems to me that the evolution of intelligent life from nothing, also requires many things to go right. We don't know what all these things are, and we can only guess what their probability is. But if even a few of them have relatively small probabilities, then the probability of all of them happening could easily be much lower than "1 in 10 billion trillion". There are many candidates for this so called "great filter". Some ideas I think are plausible are the evolution of multicellular life. The Earth was around a very, very long time before multicellular life formed. And it's believed to have required some weird coincidences like a parasite evolving into mitochondria. Another candidate is the evolution of intelligence itself. Most animals aren't intelligent. Intelligence doesn't actually seem to be very correlated with fitness beyond a certain point - and reducing brain size is actually beneficial. Animals with brains were around for a very, very long time before anything like humans appeared. Some scientists believe that humans required a really weird set of conditions to evolve. There are theories that we are a case of accidental runaway sexual selection, like the peacock's feathers. And there are many other factors we can't possibly know, that might be unique to Earth and rare on other worlds. We also don't know a huge amount about the evolution of early life. Getting from RNA self replicators to the complicated machinery of the most recent ancestor was no small feat.
skissane 10y ago
The universe is so big, that I think it's very likely that somewhere out there are, there are many other intelligent civilisations, in distant galaxies–but so far away we'll never be able to visit them, never be able to communicate with them, we'll likely never even know of their existence (not in a million years–and I mean that literally.) In the long-run (of millions of years), the two most likely outcomes for humanity are extinction or galactic colonisation. If we do colonise the galaxy, we'll prevent any other intelligent species from evolving within it (by fully occupying that ecological niche.) If we go extinct, we'll leave that niche open for another species to maybe one day occupy as we would have failed to do. The galaxy is likely a natural hard limit for our species, since while interstellar travel is difficult it is arguably possible (not with present day technology and economics, but potentially within a few centuries from now), but intergalactic travel is likely never going to be possible. Even if these authors are right that other intelligent life once existed in this galaxy, it's almost surely extinct by now. If that's true, it makes their conclusion profoundly pessimistic – the more ruins of dead civilisations this galaxy contains, the greater the likelihood that we'll meet the same fate as they did. I think we'll always be alone in the universe. And it's probably better that way.
- chmike 10y ago
  Why do you believe it is surely extinct by now ? Why do you believe that colonisation of the galaxy means eliminating all other advanced civilisations and life form ? Are you russian ;) Your reasonning is based on many assumptions. Look at us. When did we discover how to fly ? When did we landed on the moon ? Human evolution in science and technology mastering is evolving exponentially. Things can happen much faster than we thought. Another question is why is the UFO phenomenon consistently discarded in the reasoning ?
  - skissane 10y ago
    I'm not suggesting our species will go on a genocidal rampage through the galaxy. Rather, I'm suggesting that if we manage to spread through the galaxy, we won't encounter any other intelligent life, and our galactic colonisation will prevent any other intelligent species from evolving in this galaxy since we'll be fully occupying that ecological niche, just as being the dominant species on this planet makes it much less likely that other species (such as chimpanzees) will evolve to our intelligence level. (Galactic colonisation might plausibly result in speciation of homo sapiens, however.) It's extremely unlikely for two intelligent species to evolve within a single galaxy at the same time; if other intelligent life ever exists in this galaxy, it is almost certainly many millions of years older or younger than us. Any civilisation following our present trajectory is likely to colonise the galaxy within a few million years. Since we are here, no species before us has successfully colonised this galaxy, which implies either we are the first, or the others have already gone extinct before reaching that level. I discount UFOs because I believe the alternative explanations–such as natural atmospheric phenomena, secret testing of military aircraft, confusion, hallucination and delusion–are collectively much more probable than the hypothesis that extraterrestrials have visited us.
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noiv 10y ago
ITT, people start with the assumption live is something incredibly special. Another way of thinking assumes live emerges everywhere an energy gradient and some matter exists. Maybe we are not special at all. https://www.quantamagazine.org/20140122-a-new-physics-theory-of-life/ https://www.quantamagazine.org/20140122-a-new-physics-theory...
- drjesusphd 10y ago
  So where is everyone? If intelligent life is at all likely, there ought to be many civilizations that have had millions of years technological head start on us. Given one species with galactic ambitions, but technology only modestly beyond ours, it would only take them one million years to colonize the entire galaxy. So why do we not see any evidence whatsoever? This is the Fermi Paradox.
  - noiv 10y ago
    Well, maybe intelligent does not necessarily include expansive.
lumberjack 10y ago
What I always don't get about this, is the omission of the probability of life emerging. We know it's possible but do we know how likely it is?
ulmus 10y ago
In estimating a probability for the occurrence of life in the universe, the authors essentially claim to know the probability of their own existence. For me, that's a red flag. I can't know the probability of a phenomenon which my existence depends on just by observing my existence alone, because I can't observe all of the cases where the phenomenon does not occur and I do not exist.
- lisper 10y ago
  The quantity of interest in any probability problem can always be re-cast as the conditional probability of the event given that the person asking the question exists, which is necessarily 1.
  - ulmus 10y ago
    Pardon me, but I'm not sure what you mean by quantity of interest. If the quantity of interest can always be re-cast as a value which is necessarily 1, isn't "quantity of interest" the same for all probability problems?
    - lisper 10y ago
      Sorry, I wasn't very clear. > the authors essentially claim to know the probability of their own existence The "quantity of interest" is the probability of aliens, but not the probability of aliens in all possible worlds, but rather the probability of aliens in this world. In this world, the probability that the authors exist is 1.
      - ulmus 10y ago
        I respectfully disagree. I claim the probability of human existence could have been less than 1, just as the probability of heads when tossing a fair coin is less than one, even when heads is observed as an outcome. We simply can't observe "tails" in this case.
        10y ago
Udo 10y ago
It's true that so far every step of the way we have found environmental factors that are generally in favor of life. However, there are still many factors we don't know anything about. Somewhere between the possibility of one of these remaining factors being extremely unfavorable to life and us just being in a very isolated location, there should be an explanation for the Fermi paradox we're actually experiencing. Sensationalist title aside, the article actually plays it extremely safe, by asserting a very high probability of extraterrestrial civilizations having been existed somewhere in the past. But even so, there are potential problems where that might conflict with observation. I'm not generally a fan of these "alien civilizations must construct huge machines and must have a huge energy output" assertions, however, all it would take is one of the previous civilizations to have built something we can recognize. Sadly, nothing has been found, neither artefacts such as probes, nor radiological evidence in the sky. Now, there are many possible reasons for why we haven't found anything yet, first and foremost being that the galaxy is vast in both time and space. But if I forced myself to be especially pessimistic, I would say that the probability of abiogenesis might be way smaller than even our bleakest estimates.
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wtbob 10y ago
> Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first. And … nothing is provided to indicate that said probability is higher than that.
JoeAltmaier 10y ago
So you can publish papers by making up numbers?
logicallee 10y ago
Protip: if the greatest possible discovery in astrobiology is confirmed scientifically, you won't hear it first in a New York Times article whose title is "Yes, there have been aliens"...
sleepychu 10y ago
I'll agree that aliens might exist far away from us in space &|time, but so what? I'd argue there's no practical difference between being alone in the universe and our local galaxies.
- chmike 10y ago
  Why do you believe there is non difference ? Do you believe they didn't vist earth yet ?
twright 10y ago
Here's a Drakes Equation visualizer I made. I know it doesn't address certain factors but it's fun to play with as a thought experiment. Even with some optimistic numbers there's not that much out there. https://tristaaan.github.io/ngDrakesEquation/ https://tristaaan.github.io/ngDrakesEquation/
dmfdmf 10y ago
If you are interested in these issues a great book to read is called "Rare Earth:Why Complex Life is Uncommon in the Universe" by Peter Ward and Donald Brownlee. They make a convincing argument (to me anyway) that bacteria and simple life forms are probably common in the universe but animals and complex life with intelligence might be exceedingly rare. We, quite possibly, could be the only intelligent life in the universe.
ChuckMcM 10y ago
I can't recommend "The Vital Question" by Nick Lane enough for people who are really interested in the question of life elsewhere. It does such a wonderful job of show how mechanically "life" can be started as a way of simply reacting chemicals to a lower energy state. It neatly ties together biochemistry and geochemistry in a very plausible (and testable) way. Given the analysis, I would expect that bacteria and archaea, are present on any world with liquid water and a threshold amount of heat. Which would include Mars, Europa, and probably Io as well. There are a number of forms of bacteria living in the ionosphere which could be dropped on to Mars and they would do just fine there. The odd bit comes from the origin of eukaryotes. Which, according to Lane, might arise if archaea were endosymbiotically living inside bacteria. That works but he doesn't offer any suggestion of what caused it to happen the first time. And he makes a reasonably good case that what ever it was that caused it, happened exactly once in the 4+ billion years of the planet and 3+ billion years of bacterial life roaming around.
- Lost_BiomedE 10y ago
  I read his book 'power sex suicide'. Here is a good summary: http://ronbarak.tumblr.com/post/25996121029/life-is-it-inevitable-or-just-a-fluke-by-nick http://ronbarak.tumblr.com/post/25996121029/life-is-it-inevi... In the book he expanded on what was needed to make the jump to complex life and his opinion on how unlikely it was. He made a case for how only a relatively small time window was available for it to happen at all. I second the rec!
bufo 10y ago
About Drake's equation: https://xkcd.com/384/ https://xkcd.com/384/
ommunist 10y ago
What these guys clearly omitting is that our planet could be the host of not only human civilization. At least in the past.
imh 10y ago
One in 10^22 seems really easy odds to beat. Basically anything should happen more often than that, right? But if we choose a random 16 letters, the odds that they spell "unscientifically" is less than that. If we gave 16 letters to each of the 10^22 stars, we expect the word to happen on only one star, if even that. It's not too hard to argue that life is more difficult to get by random chance than the word "unscientifically", so we can't simply argue that "of course life will happen with those odds!"
slowmovintarget 10y ago
No cookies, no article. Couldn't read. Comments seem sufficient for me to realize I needn't have bothered.
artur_makly 10y ago
i love u guys. really great discourse. thank u.

229 points by rosser 10y ago

The most likely reason that nobody seems to be out there is the great filter. The author asks if our civilisation will last millenia or millions of years - but I think a more apt scale would be decades or centuries. It just seems pretty obvious that we have an ever increasing set of opportunities to extinct ourselves, and therefore the probability of a civilisation ending disaster only grows. All the aliens either blew themselves up, starved, or are the kind of incredibly boring, mind-numblingly conservative people you wouldn't invite to a local cluster cocktail party. Oh, either that or civilisations tend to disappear up their own simhole.

sevenless 10y ago
The Doomsday Argument implies we've got centuries or less left. https://en.wikipedia.org/wiki/Doomsday_argument https://en.wikipedia.org/wiki/Doomsday_argument
- madaxe_again 10y ago
  Oh, I think we've decades or years rather than centuries. We always underestimate exponential growth. That's OK, at least it'll make for an interesting existence.
XorNot 10y ago
Conversely, by 2025 there might be living humans on Mars (if Elon Musk gets his way). And while that's not enough to form the basis of a backup civilization, I'm somewhat more interested in the effect on global zeitgeist it's likely to have. The feeling of the times is, I feel, an underestimated factor in how democracies pick their priorities - and the early 21st century has been very down on itself trying to figure out practical, post-conflict economic realities.
- kirykl 10y ago
  The great filter could well be going from single to multi planetary, on a single planet our survival (quite) long term is zero.
- sangnoir 10y ago
  > And while that's not enough to form the basis of a backup civilization Or that might accelerate the end of civilization due to our inherent tribalism - the US isn't quite a backup of Europe as a 16th century European would have imagined. Who is to say there won't be a Planetary Mutually Assured Destruction? The Expanse (books and TV series) explores some themes around planetary identity & politics in a fictional future where Mars and the outer solar system has been colonized and Earth is seen as a meddling 'old country' by some.

houseofshards 10y ago

Content of the article is pretty information, but worst clickbait title of the year. At the risk of alienating some fraction of HN community (no pun intended), I'm going to say this is what you get when trying to chase the likes of Gawker (again, no pun intended).

rl3 10y ago
The irony here is that Gawker's relevant clickbait is actually far superior: http://io9.gizmodo.com/11-of-the-weirdest-solutions-to-the-fermi-paradox-456850746 http://io9.gizmodo.com/11-of-the-weirdest-solutions-to-the-f...
- mrob 10y ago
  I read a good short story recently about a weird Great Filter: http://www.begoodenough.com/the-great-filter/ http://www.begoodenough.com/the-great-filter/
  - amasad 10y ago
    The first movie that I think plays around with the idea of a Great Filter (not quite; but close) is The Forbidden Planet, a 1950s scifi. The basic idea without spoiling it is that enhancing their own intelligence also made powerful their lizard brain of sorts. I assume freudian psychoanalysis was big in the 50s so they called it the ID in the film.
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jstanley 10y ago

Title is mild clickbait. There's no evidence for the claim, just a persuasive argument that it's probably true. Interesting nonetheless.

SonicSoul 10y ago
it's not mild clickbait. it's the definition of click bait. it states a very controversial conclusion, as if the argument is finally settled, while the body has little new information and fudges around with statistic that "it's likely probable that there is or once was another species".
- hudibras 10y ago
  Since this is published in a newspaper, the term that is generally used is "headline," not "click bait."
- hudibras 10y ago
  Since this is published in a newspaper, the terms that are generally used are "headline" or "title," not "click bait."
  - pbhjpbhj 10y ago
    Their media kit claims 78 million online viewers vs. 5 million wealthy newspaper audience. I think more people click to read the article than turn a paper page to read it. Newspapers are online media companies now that happen to also produce limited paper versions. Perhaps I'm missing your point?
dang 10y ago
We added "probably" above.

andrewstuart2 10y ago

Probably. Assuming they're correct. Our planet is 12,742km in diameter, yet we've only drilled 12.262km deep [1] (and we were wrong about how hot it was gonna be), and sent a human down ~10.900km [2] (and we still can't decide how deep we've actually been). Do we really think we understand the probability of alien life on another planet that well, given the amount of data we have on those planets, and that we're constantly proven wrong on our own? And yet (either way) I'm not sure it really matters. No human has left our own planet for longer than 437.7 days [3]. Say they're right, though. If an alien race exists, we're still a ways from being able to do anything about it. Unless we can make it there in 1.198 years. If that alien race can make it here, awesome. Let's talk then. If they can make it here and are hostile, then it's been swell. See you on the other side. Probably. [1] https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole [2] https://en.wikipedia.org/wiki/Bathyscaphe_Trieste https://en.wikipedia.org/wiki/Bathyscaphe_Trieste [3] https://en.wikipedia.org/wiki/List_of_spaceflight_records https://en.wikipedia.org/wiki/List_of_spaceflight_records

nielsbjerg 10y ago
You got the units of the borehole wrong, it's in meters not kilometers.
- andrewstuart2 10y ago
  Well, we've certainly drilled more than 12 meters. :-P (Note the decimal point: 12.262km; I just converted to km to keep it consistent with the other measurements I cited) Could be confusing if you're used to the inverse comma/period from what we use in the US (comma=thousands, period=decimal).
  - deleted 10y ago
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  - tluyben2 10y ago
    It is very confusing even though I know this to be the case. It is much harder to parse when the numbers are similar. I do not care which one, just wish everyone would use the same notation. In this case for me it would have been clearer if it said 12262km vs 12262m which is what I would have written. But he :) Interesting comment anyway.

dandare 10y ago

m - km, fix the units

dacompton 10y ago

There have been aliens -- and they don't care about us. To assume that a collection of beings which have obtained the ability to travel amongst the stars would focus their attention on a single species on a single planet is fundamentally selfish. What resources does our earth contain that are not (more easily) obtainable elsewhere? If Drake's equation "holds", then what novelty do _we_ provide?

j-pb 10y ago
> What resources does our earth contain that are not (more easily) obtainable elsewhere? If Drake's equation "holds", then what novelty do _we_ provide? Us. If the probability of an intelligent species developing are that low that there might only be a handful of intelligent species in our galaxy then making contact with each of them is extremely interesting if they are as curious as we are.
Houshalter 10y ago
There are many reasons alien races would interact with primitives. Morality - they might be utilitarian and desire to relieve the suffering of other sentient beings. Or force their weird alien morals onto them. Competition - we might not be a threat now, but given a sufficiently long time, we could evolve into one. If they really don't care about us, it would cost them very little to exterminate us early.
- chipx86 10y ago
  I see these mentioned a lot, and sci-fi is big on the latter. The one I rarely see come up is "entertainment." If we were traveling amongst the stars today, with our values and morality as they currently are, and happened upon a world of what we'd consider to be primitive life, we'd probably scoop some up and put them in a zoo, or broadcast them on TV. We'd want to study them, learn what makes them tick, maybe try to see if communication was possible, but in the end, we'd get entertainment value from them. Even if we left them be and studied from a distance, the human race would be fascinated. New life! A new place! We like new things. The news would cover these creatures ("Are they a threat to humanity? News at 11."), they'd be woven into stories and shows and movies in one form or another. If we could safely bring them back, people would want to see them in person. We'd get a lot of entertainment value out of these new creatures. We're a curious race who manages to get bored of spectacular things quickly, which is a large reason we continue to innovate and push forward. There's no way to know for sure what would motive another intelligent race to advance to the point where they'd reach for the stars, but if any of them shared a degree of curiosity, I doubt they'd pass us up if they found us. We'd be something new for them. Maybe we'd end up in their stories, their drawings, their videos, or even their zoos. Maybe they'd be interested in how we smell, or the way we dress and decorate ourselves, or the things that we watch on TV. Our languages, our fights, our culture. Or maybe just the way we go about our business, missing some big cosmological truth that's so obvious to them, as if we're adorable little children. Maybe we'd provide just enough entertainment value to be worth a quick trip. Or a long stay.

apsec112 10y ago

"In other words, given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational." This is terribly silly. It reminds me of the Onion talks: "Step 1: Devise an idea to create a car that runs on compost. Step 2: Create the car. We’ve already completed Step 1. We’re half way there." Increased certainty on three of the seven factors is irrelevant, because 99% of the uncertainty is concentrated in the other four. Specifically, the odds of abiogenesis are ~1/2^n, where n is the complexity in bits of the smallest self-replicator. n is bounded below by ~100 or so (or it would have happened in a lab somewhere), and is bounded above by ~1 million (the smallest existing bacteria), so we know it's somewhere in there. But where? We have only the vaguest guesses. "Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first." "One in 10 billion trillion" sounds like a very large number, and it's put in italics for emphasis, but in information-theoretic terms it's tiny. log2(10^22) is just 73 bits. If all that we know about a number is that it's somewhere between a hundred and a million, saying that X would imply it's higher than 73 (well technically 73 + log2(#incidences of molecular combination), so probably a few hundred) is not a disproof of X, nor really even much evidence against X.

reso 10y ago
I had a similar intuition reading the article. I don't think we understand much at all about the probabilities of life forming even under the ideal circumstances. The events that took place on earth could still be one in a billion, or they could be one in an incomprehensibly high number. Nevertheless the progress on the other factors in the Drake equation is very interesting and impressive.
- raverbashing 10y ago
  > . The events that took place on earth could still be one in a billion, or they could be one in an incomprehensibly high number. I disagree with this. It seems that, from what happened to other planets on the solar system, that nothing happened on Earth too much out of the ordinary. Mars had a similar story (except for the whole Moon coming out of a giant collision), and had water. But maybe it was too small to keep warm for enough time Earth had 5 mass-extinctions, that "reset the game" before we got to humans. Doesn't seem too far fetched to me I really don't buy that Earth is one in a billion unless Mars is one in a billion as well. Maybe one in 1000? One in 100000? And that's limiting intelligent life to what we know. Yes, maybe the ideal speed of chemical reactions (for intelligent life) happen around 273K, or maybe there's another way

jkeler 10y ago

> a probability for civilizations to form of one in 10 billion per planet was considered highly pessimistic I think people underestimate how low probabilities can really be. According to wiki the shortest self-replicating RNA is 165-bases long. Even if you convert all observable universe in RNA this is still not enough for this RNA to form by chance (4^165 is much larger than number of atoms in observable universe).

jkeler 10y ago
For people who want an alternative view on this problem: http://biologydirect.biomedcentral.com/articles/10.1186/1745-6150-2-15 http://biologydirect.biomedcentral.com/articles/10.1186/1745...
perlgeek 10y ago
> Even if you convert all observable universe in RNA this is still not enough for this RNA to form by chance (4^165 is much larger than number of atoms in observable universe). Which kinda suggests there is either a mechanism that promotes that, or there are other, easier paths to get self replication. Otherwise we mostly likely wouldn't be here.
qaq 10y ago
Given enough time anything can form out of random fluctuations if it has >0 probability no matter how small.
- Houshalter 10y ago
  "Enough time" can easily be longer than the age of the universe. A million monkeys typing on keyboards will eventually write shakespeare. But it will be longer than the universe before they even type a single sentence of it correctly.
  - qaq 10y ago
    It sure can be, but as long as it is less than the expected lifetime of the universe it will still happen. A million monkeys - given that Hamlet contains such long sentences as "He." it will take far less then a minute for them to type a single sentence correctly.

SFJulie 10y ago

No they have not been any aliens until proven so... Science requires a theory and experimental validation. The existence of aliens has been postulated by a crazy monk that also invented the concept of monads. It is much more metaphysics (religious thinking) than physics. It strikes me as odd that most of flawed science is coming with the same flaws as religious thinking.

coldtea 10y ago
>Science requires a theory and experimental validation. You'd be surprised. That's 19th century thinking about science, and not really how science works in practice most of the time.
- SFJulie 10y ago
  Well, that is at least what made relativity and quantum mechanic successful. And yes there has been a lot of flawed science in the XIXth I am aware of it ... like the theory of the ether that Einstein dispelled through experimentation, or the superiority of some "races", or the morpho-psychology...

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throwaway_yy2Di 10y ago

If you parse the article carefully, the entire argument is summarized as "There are more than 10^22 planets, therefore ETI probably exists[ed] if P(intelligent life|planet) > 10^-22". Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first. [...] In other words, given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational.

ekianjo 10y ago
That was extremely shallow from the nytimes.
someguydave 10y ago
Indeed. Furthermore, the NYT tells us that we are apparently irrational if we believe the probability of advanced life appearing is less than 10^-22.

theaeolist 10y ago

I enjoy these quasi statistical arguments. Can anyone remind me what is the probability that God exists, or that we live in a computer simulation?

venomsnake 10y ago
God in the religious sense probably does not exist. On the other hand the existance of type II creatures (that can manage and direct the energy of whole galactic clusters) would not surprise me the least. Their interference with human evolution and deeds would not be shocking too. The quantum machanics behave disturbingly close to lazy evaluation - so this would not be surprising too. Everyone of us is a god to a colony of ants.
- amasad 10y ago
  Apparently physicists don't agree with the 'lazy evaluation' analogy. I vaguely remember something about the wave function being continuos and computationally expensive and not really an optimization
qaq 10y ago
Define God?
- givan 10y ago
  https://en.wikipedia.org/wiki/Wuji_(philosophy) https://en.wikipedia.org/wiki/Wuji_(philosophy) https://en.wikipedia.org/wiki/Purusha https://en.wikipedia.org/wiki/Purusha
Houshalter 10y ago
The probability that God exists depends entirely on your priors. After all we have no observable evidence to consider. I would give it a very low prior, because it's such a weirdly specific belief, considering all the possible origins of the universe. The probability we are in a simulation depends on a bunch of assumptions. Assuming specifically we are asking about a "historical simulation", that the parent universe is identical to ours, we can change the question. Instead ask what is the probability we will someday create historical simulations of our past. Technology certainly seems to advance over time, and the upper limits on computational power are extremely generous. So it's possible we could someday have the technology to do it. Assuming that, then it just depends on the probability you think we will want to make simulated beings. Something about that seems kind of sick and immoral, so I am skeptical of that assumption. But if it is true, then the probability you are in a simulation is extremely high. Because the number of simulated beings could easily be orders of magnitude higher than the number of actual 2016 Earth inhabitants. Provided that many different simulations are run.

sktrdie 10y ago

By pure probability, if we're the first intelligent species here on earth (that is able to build radio communicators) out of what, ~4 billion species that ever existed, what are the odds of us being the first in the entire universe? My logic is that intelligence (as defined above) is clearly rare here on earth where life is prolific, hence by no means a certain development of evolution. I wouldn't be surprised if we're the first in the universe where the conditions are certainly less hospitable for life. This game of probability doesn't only depend on the sample size, but also on what you're looking for. For instance, you can say that if you find a purple grain of sand, and you know there are trillions of other grains, then you'll be sure to find other purple grains. But what if the purple grain has written on it "hello how are you" by sheer chance. You'd probably never find another grain of sand with that same writing. And then you can say, "us being the first is egocentric". Well, but we're the first (on earth) when it comes to building radio stations, so we clearly won that lottery big time. Is it such a stretch to say we won the lottery in the universe as well?

coldtea 10y ago
>And then you can say, "us being the first is egocentric". Well, but we're the first when it comes to building radio stations, so we clearly won that lottery big time. Who told you we're "the first when it comes to building radio stations"? There could be 200 other explanations for "radio silence" from advanced civilizations (if they exist).
- sktrdie 10y ago
  First on earth out of billions of species. That was my hole point... I edited it to make it clearer.
  - coldtea 10y ago
    >First on earth out of billions of species That's par for the course. That's how evolution works. And we're also gonna be the last on earth (we or our evolved successors), because we have the evolutionary upper hand. But that doesn't say much for other planets. We expect them too to have billions of species and a race to produce an intelligent being too.

Houshalter 10y ago

>unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.... the degree of pessimism required to doubt the existence... of an advanced extraterrestrial civilization borders on the irrational. After working with probability theory and combinatorics a bit, you realize probabilities much smaller than this occur naturally all the time. It might be hard for people not familiar with that to appreciate this, and be wowed by such a small number. The thing is that independent probabilities multiply together, and so approach 0 exponentially fast. The probability of winning the lottery is of course very small. But there are so many people, that someone wins a lottery every day. But the probability of winning the lottery twice is really small. The set of people that have won twice is a very small set indeed. And the probability of winning 3 times is so small that we should expect it to be a sure sign of corruption of the lottery, or intervention by supernatural forces. It's also about 1 in 10 billion trillion. It seems to me that the evolution of intelligent life from nothing, also requires many things to go right. We don't know what all these things are, and we can only guess what their probability is. But if even a few of them have relatively small probabilities, then the probability of all of them happening could easily be much lower than "1 in 10 billion trillion". There are many candidates for this so called "great filter". Some ideas I think are plausible are the evolution of multicellular life. The Earth was around a very, very long time before multicellular life formed. And it's believed to have required some weird coincidences like a parasite evolving into mitochondria. Another candidate is the evolution of intelligence itself. Most animals aren't intelligent. Intelligence doesn't actually seem to be very correlated with fitness beyond a certain point - and reducing brain size is actually beneficial. Animals with brains were around for a very, very long time before anything like humans appeared. Some scientists believe that humans required a really weird set of conditions to evolve. There are theories that we are a case of accidental runaway sexual selection, like the peacock's feathers. And there are many other factors we can't possibly know, that might be unique to Earth and rare on other worlds. We also don't know a huge amount about the evolution of early life. Getting from RNA self replicators to the complicated machinery of the most recent ancestor was no small feat.

skissane 10y ago

The universe is so big, that I think it's very likely that somewhere out there are, there are many other intelligent civilisations, in distant galaxies–but so far away we'll never be able to visit them, never be able to communicate with them, we'll likely never even know of their existence (not in a million years–and I mean that literally.) In the long-run (of millions of years), the two most likely outcomes for humanity are extinction or galactic colonisation. If we do colonise the galaxy, we'll prevent any other intelligent species from evolving within it (by fully occupying that ecological niche.) If we go extinct, we'll leave that niche open for another species to maybe one day occupy as we would have failed to do. The galaxy is likely a natural hard limit for our species, since while interstellar travel is difficult it is arguably possible (not with present day technology and economics, but potentially within a few centuries from now), but intergalactic travel is likely never going to be possible. Even if these authors are right that other intelligent life once existed in this galaxy, it's almost surely extinct by now. If that's true, it makes their conclusion profoundly pessimistic – the more ruins of dead civilisations this galaxy contains, the greater the likelihood that we'll meet the same fate as they did. I think we'll always be alone in the universe. And it's probably better that way.

chmike 10y ago
Why do you believe it is surely extinct by now ? Why do you believe that colonisation of the galaxy means eliminating all other advanced civilisations and life form ? Are you russian ;) Your reasonning is based on many assumptions. Look at us. When did we discover how to fly ? When did we landed on the moon ? Human evolution in science and technology mastering is evolving exponentially. Things can happen much faster than we thought. Another question is why is the UFO phenomenon consistently discarded in the reasoning ?
- skissane 10y ago
  I'm not suggesting our species will go on a genocidal rampage through the galaxy. Rather, I'm suggesting that if we manage to spread through the galaxy, we won't encounter any other intelligent life, and our galactic colonisation will prevent any other intelligent species from evolving in this galaxy since we'll be fully occupying that ecological niche, just as being the dominant species on this planet makes it much less likely that other species (such as chimpanzees) will evolve to our intelligence level. (Galactic colonisation might plausibly result in speciation of homo sapiens, however.) It's extremely unlikely for two intelligent species to evolve within a single galaxy at the same time; if other intelligent life ever exists in this galaxy, it is almost certainly many millions of years older or younger than us. Any civilisation following our present trajectory is likely to colonise the galaxy within a few million years. Since we are here, no species before us has successfully colonised this galaxy, which implies either we are the first, or the others have already gone extinct before reaching that level. I discount UFOs because I believe the alternative explanations–such as natural atmospheric phenomena, secret testing of military aircraft, confusion, hallucination and delusion–are collectively much more probable than the hypothesis that extraterrestrials have visited us.

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noiv 10y ago

ITT, people start with the assumption live is something incredibly special. Another way of thinking assumes live emerges everywhere an energy gradient and some matter exists. Maybe we are not special at all. https://www.quantamagazine.org/20140122-a-new-physics-theory-of-life/ https://www.quantamagazine.org/20140122-a-new-physics-theory...

drjesusphd 10y ago
So where is everyone? If intelligent life is at all likely, there ought to be many civilizations that have had millions of years technological head start on us. Given one species with galactic ambitions, but technology only modestly beyond ours, it would only take them one million years to colonize the entire galaxy. So why do we not see any evidence whatsoever? This is the Fermi Paradox.
- noiv 10y ago
  Well, maybe intelligent does not necessarily include expansive.

lumberjack 10y ago

What I always don't get about this, is the omission of the probability of life emerging. We know it's possible but do we know how likely it is?

ulmus 10y ago

In estimating a probability for the occurrence of life in the universe, the authors essentially claim to know the probability of their own existence. For me, that's a red flag. I can't know the probability of a phenomenon which my existence depends on just by observing my existence alone, because I can't observe all of the cases where the phenomenon does not occur and I do not exist.

lisper 10y ago
The quantity of interest in any probability problem can always be re-cast as the conditional probability of the event given that the person asking the question exists, which is necessarily 1.
- ulmus 10y ago
  Pardon me, but I'm not sure what you mean by quantity of interest. If the quantity of interest can always be re-cast as a value which is necessarily 1, isn't "quantity of interest" the same for all probability problems?
  - lisper 10y ago
    Sorry, I wasn't very clear. > the authors essentially claim to know the probability of their own existence The "quantity of interest" is the probability of aliens, but not the probability of aliens in all possible worlds, but rather the probability of aliens in this world. In this world, the probability that the authors exist is 1.
    - ulmus 10y ago
      I respectfully disagree. I claim the probability of human existence could have been less than 1, just as the probability of heads when tossing a fair coin is less than one, even when heads is observed as an outcome. We simply can't observe "tails" in this case.
      - 10y ago

Udo 10y ago

It's true that so far every step of the way we have found environmental factors that are generally in favor of life. However, there are still many factors we don't know anything about. Somewhere between the possibility of one of these remaining factors being extremely unfavorable to life and us just being in a very isolated location, there should be an explanation for the Fermi paradox we're actually experiencing. Sensationalist title aside, the article actually plays it extremely safe, by asserting a very high probability of extraterrestrial civilizations having been existed somewhere in the past. But even so, there are potential problems where that might conflict with observation. I'm not generally a fan of these "alien civilizations must construct huge machines and must have a huge energy output" assertions, however, all it would take is one of the previous civilizations to have built something we can recognize. Sadly, nothing has been found, neither artefacts such as probes, nor radiological evidence in the sky. Now, there are many possible reasons for why we haven't found anything yet, first and foremost being that the galaxy is vast in both time and space. But if I forced myself to be especially pessimistic, I would say that the probability of abiogenesis might be way smaller than even our bleakest estimates.

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wtbob 10y ago

> Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first. And … nothing is provided to indicate that said probability is higher than that.

JoeAltmaier 10y ago

So you can publish papers by making up numbers?

logicallee 10y ago

Protip: if the greatest possible discovery in astrobiology is confirmed scientifically, you won't hear it first in a New York Times article whose title is "Yes, there have been aliens"...

sleepychu 10y ago

I'll agree that aliens might exist far away from us in space &|time, but so what? I'd argue there's no practical difference between being alone in the universe and our local galaxies.

chmike 10y ago
Why do you believe there is non difference ? Do you believe they didn't vist earth yet ?

twright 10y ago

Here's a Drakes Equation visualizer I made. I know it doesn't address certain factors but it's fun to play with as a thought experiment. Even with some optimistic numbers there's not that much out there. https://tristaaan.github.io/ngDrakesEquation/ https://tristaaan.github.io/ngDrakesEquation/

dmfdmf 10y ago

If you are interested in these issues a great book to read is called "Rare Earth:Why Complex Life is Uncommon in the Universe" by Peter Ward and Donald Brownlee. They make a convincing argument (to me anyway) that bacteria and simple life forms are probably common in the universe but animals and complex life with intelligence might be exceedingly rare. We, quite possibly, could be the only intelligent life in the universe.

ChuckMcM 10y ago

I can't recommend "The Vital Question" by Nick Lane enough for people who are really interested in the question of life elsewhere. It does such a wonderful job of show how mechanically "life" can be started as a way of simply reacting chemicals to a lower energy state. It neatly ties together biochemistry and geochemistry in a very plausible (and testable) way. Given the analysis, I would expect that bacteria and archaea, are present on any world with liquid water and a threshold amount of heat. Which would include Mars, Europa, and probably Io as well. There are a number of forms of bacteria living in the ionosphere which could be dropped on to Mars and they would do just fine there. The odd bit comes from the origin of eukaryotes. Which, according to Lane, might arise if archaea were endosymbiotically living inside bacteria. That works but he doesn't offer any suggestion of what caused it to happen the first time. And he makes a reasonably good case that what ever it was that caused it, happened exactly once in the 4+ billion years of the planet and 3+ billion years of bacterial life roaming around.

Lost_BiomedE 10y ago
I read his book 'power sex suicide'. Here is a good summary: http://ronbarak.tumblr.com/post/25996121029/life-is-it-inevitable-or-just-a-fluke-by-nick http://ronbarak.tumblr.com/post/25996121029/life-is-it-inevi... In the book he expanded on what was needed to make the jump to complex life and his opinion on how unlikely it was. He made a case for how only a relatively small time window was available for it to happen at all. I second the rec!

bufo 10y ago

About Drake's equation: https://xkcd.com/384/ https://xkcd.com/384/

ommunist 10y ago

What these guys clearly omitting is that our planet could be the host of not only human civilization. At least in the past.

imh 10y ago

One in 10^22 seems really easy odds to beat. Basically anything should happen more often than that, right? But if we choose a random 16 letters, the odds that they spell "unscientifically" is less than that. If we gave 16 letters to each of the 10^22 stars, we expect the word to happen on only one star, if even that. It's not too hard to argue that life is more difficult to get by random chance than the word "unscientifically", so we can't simply argue that "of course life will happen with those odds!"

slowmovintarget 10y ago

No cookies, no article. Couldn't read. Comments seem sufficient for me to realize I needn't have bothered.

artur_makly 10y ago

i love u guys. really great discourse. thank u.