16 ms·

60 years later, is it time to update the Drake equation?

62 points by elorant 5y ago

Grustaf 5y ago
No, it's time to scrap it, since it never made any sense. You can't talk about probabilities when there's only a single trial, the sample size is 1 and you have no possible way to determine the parameters in the first place.
- Out_of_Characte 5y ago
  While true that the last parameters are completely unknown (IE, wether a planet with life has intelligent life, and wether they have radio transmission capabilities) the other parameters are something we can most certainly estimate. The absense of precision in this case is why it was written in the first place. "As I planned the meeting, I realized a few day[s] ahead of time we needed an agenda. And so I wrote down all the things you needed to know to predict how hard it's going to be to detect extraterrestrial life. And looking at them, it became pretty evident that if you multiplied all these together, you got a number, N, which is the number of detectable civilizations in our galaxy. This was aimed at the radio search, and not to search for primordial or primitive life forms." So the sample size isn't 1 and there are known ways to detect all but 2 or 3 parameters of the drake equation.
  - jcranmer 5y ago
    > So the sample size isn't 1 and there are known ways to detect all but 2 or 3 parameters of the drake equation. Actually, only 2 or 3 parameters of the Drake equation are estimable. (It depends on how you want to define "planets that can potentially support life"--you can argue that the answer is anywhere between 1 and 5 in our own solar system). Everything that talks about the possibility of life evolving, let alone speculating about how it will evolve or the xenosociology of what that life will try to do, is pure conjecture: that's the last 4 values of the equation, more than half of it.
  - Grustaf 5y ago
    Ok, you can say that the sample size is the number of planets, but there’s only 1 trial. EDIT: If you go through the factors, only the first three even make sense to talk about. And the third, about "number of planets per star that can potentially support life" can only be discussed in terms of our particular form of life. We have no idea at all what other types of life there could be, much less under what conditions that might happen. The others are completely unknowable. For example: f_i: The fraction of planets with life that actually go on to develop intelligent life (civilizations)" I'm embarrassed even writing it out. How can anyone even start to think that they could come even with 10 orders of magnitude of the right answer, if it's even a well defined probability, which I doubt. We know of exactly one planet with life, and it has intelligent life that emits radio waves. Is that an inevitability, or a one in a trillion fluke? But what bother me the most is how you even think you can talk about probabilities when there's only one trial, and for the later factors, the sample size is most definitely 1. It's just inane.
- kelnos 5y ago
  You absolutely can talk about probabilities, and it's an interesting thought experiment. You just can't -- yet -- plug in meaningful numbers derived from experimental data.
  - Grustaf 5y ago
    Yet? How could you ever hope to be able to say anything about the last five factors until you find another civilisation? By which time you have the answer anyway.
- pitched 5y ago
  You can’t really get any precision out of it but I think the size of the error bars is interesting, where recent estimates come out somewhere between 10^-13 and 10^8. That makes it a bit more likely that we’re alone than not. https://en.m.wikipedia.org/wiki/Drake_equation#Estimates https://en.m.wikipedia.org/wiki/Drake_equation#Estimates
mvzvm 5y ago
The Drake Equation always felt like gibberish to me. How can you have an equation "used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy" when we have nothing to test it with?
- vimacs2 5y ago
  I have to disagree. It is useful to be able to quantify the exact state of ignorance that we currently have and as our observational reach expands, the values of the variables in the equation should become less and less fuzzy. The problem isn't with the Drake equation, it's with the pop science articles that extrapolated things from it way beyond the original intent or scope.
  - treeman79 5y ago
    Several sets of unknown on an infinite universe, so we know know nothing. However thanks to speed of light the data set is not infinite, just absurd. So we know almost nothing. Given time the expansion of the universe will push all galaxies and stars away from us. The data set will be 1. We now know everything. As expansion continues all hydrogen items will eventually break apart. All life has ended. Nothing now knows us.
- kelnos 5y ago
  You can certainly have it, you just can't use it with any sense of accuracy until you have more data.
- nend 5y ago
  Take a look at the article: "Rather than being an actual means for quantifying the number of intelligent species in our galaxy, the purpose of the equation was meant to frame the discussion on SETI. In addition to encapsulating the challenges facing scientists, it was intended to stimulate scientific dialog among those attending the meeting. As Drake would later remark:..." Then follows a video of Drake speaking.
- delecti 5y ago
  It's a thought experiment meant to highlight known unknowns. If we could perfectly measure each field, we would necessarily have an idea of the number of intelligent civilizations. Each term raises interesting questions, even if they can't be precisely measured (or even guessed at with any confidence).
optimalsolver 5y ago
Learned about this equation from the late Michael Crichton's book "Sphere". A really great first contact science fiction story.
- blacktriangle 5y ago
  Mandatory to mention when talking about Sphere: read the book first, then watch the movie if you feel so inclined. The book is very very good, the movie is okay but so much of the book takes place in the characters' heads that most of the plot is lost in the film.
lordnacho 5y ago
I'm a bit surprised at the criticism. I always thought of it as more of an equation template than a very specific equation. Of course if you take a specific version of it, there are things it won't capture that we discover over time. But the idea that we can take a very large number and whittle it down seems reasonable.
- _rpd 5y ago
  Yes, it's inspired a lot of investigations and discussions, which was exactly its purpose. See also: 'solutions' to the Fermi Paradox. https://en.wikipedia.org/wiki/Fermi_paradox https://en.wikipedia.org/wiki/Fermi_paradox
jawns 5y ago
I don't have any philosophic objections to the existence of extraterrestrial life, but what does bug me is when people claim that simply because the universe is so big, that somehow makes it not only likely but practically certain that life has developed on other planets or in other solar systems or galaxies. That kind of thinking presumes some very important information that we just don't have. We are currently unable to enter any coherent value into the portion of the Drake Equation that pertains to how frequently life arises from non-life. We have an admittedly very limited knowledge of events outside of our own planet, but so far as we know, abiogenesis has occurred only once, and from that one event, all life on Earth proceeded. (It's possible that abiogenesis occurred independently multiple times during the beginning of life on Earth, but I don't think we yet have a compelling argument that it must have happened more than once.) My favorite analogy: Suppose you see a number with this pattern: 0.1001000101001000101001000___ What would you say is the likelihood that a 1 is the next number in the sequence? Not that hard to compute a probability, is it? But suppose you see a number with this pattern: 0.1000000000000000000000000___ What is the likelihood that a 1 is the next number in the sequence? You could say the odds are 1-in-25, but that doesn't takes into account the clear pattern we see in the sequence. Unless and until we start to see some more ones pop up, it's reasonable to assume that this is a sequence of infinite zeroes, or at the very least that it could perfectly well be a sequence of infinite zeroes. Suppose the sequence goes on for many trillions of numerals. No one's going to say, "Well, if there are trillions of 0s, it's highly unlikely that there won't be some 1s sprinkled in there somewhere."
- kadoban 5y ago
  If there are no more 1s, then we need to answer why our position in the universe is unique. That seems like a hard question to answer. It just seems like a _much_ better bet that we aren't the only 1.
  - Smithalicious 5y ago
    This reasoning seems flawed, how is it that an answer that doesn't lead to difficult questions is more likely (rather than simply more convenient)?
  - 5y ago
29athrowaway 5y ago
Drake equation needs to take in consideration more factors, for sure. Stars have lifecycles, and they can only support life in a stable manner in some stages of that lifecycle. I guess Drake just assumed that stars lifecycles have such a slow progression that for the purposes of determining alien life we can just assume it is constant.
- ProAm 5y ago
  > Stars have lifecycles, and they can only support life in a stable manner in some stages of that lifecycle. That is what the 'L' is in the formula
jfengel 5y ago
The Drake equation is an example of a more general issue in science: what are we going to spend money on? The Drake equation is treated as fodder for late-night Cheetos-driven college sophomore discussions. But we use it, and siblings, to estimate the inestimable: how much value do we get out of a dollar put towards actually investigating this? No matter what the field, it's always all over the map. Do we want to spend gigabucks on an LHC successor in the hopes of a vast payoff? Do we want to spend megabucks on this specific line of cancer research? Or should we spend the same money on thousands of kilobuck experiments in everything from economics to psychology to polymer chemistry? It's even harder when there isn't actually a dollar value attached. Even if we discover alien life, what's the merit of that? Economically, perhaps nothing, other than sales of "I wanted to believe/and I was right" tee shirts. But in terms of satisfaction, perhaps more than all of the movies and video games ever made put together. That's why we spend so much effort trying to estimate priors that we know are too wild to be of actual value in that calculation. Playing with the Drake equation is fun. That's all. But it does also ultimately inform the expenditure of some resources, even if we don't actually do the math.
- redis_mlc 5y ago
  > late-night Cheetos-driven college sophomore Welcome to HN! > starfaring civilization Reinforces the point - fanbois confusing scifi with reality.
- s1artibartfast 5y ago
  Why do anything? Any questions of resource allocation ultimately come down to a question individual and social values, or merit, as you phrased it. Merit is inherently arbitrary. Some people can and do think answering the question of the existence of extraterrestrial life has intrinsic merit and is the single most important society could do. More important than improving global prosperity or even continuation of the species.
ud_0 5y ago
I think (hope?) the Drake equation was never intended as a tool for making realistic estimations, I always thought it was more of a first approximation of how one might go about thinking about modeling when all you have is a sample of one. Specifically the rate of star formation has always been dubious, because there is such an enormous lag between star formation and the emergence of intelligent life (even if we turn out to be an extremely slow outlier), making it unsuitable for estimating the amount of civilizations active at a specific point in time. My personal drake equation would include only factors that are based on the current state of the galaxy. But that's the Drake equation doing its job: making people think about cosmic odds. It doesn't need an update, because I argue it shouldn't be taken literally in the first place. A few times a year, authors put out "new" estimations of the number of galactic civilizations, and to do that there is really not much alternative to chaining together these kinds of probabilities. While they sometimes may or more often may not use the actual Drake equation to do it, its value lies in the basic structure, not in its specific implementation.
- ghaff 5y ago
  One of the challenges (I won't say problems) with the Drake Equation is we have some sense for some numbers and they're very very large. Which encourages people to use formulations for some of the other terms like "even if we assume this is one in a billion" and this is "one in a million," you still come up with a significant number of civilizations. When, in fact, some other term may be so vanishingly small that it's only happened once. (Or there may be something else, e.g. a great barrier, that's not being taken into account.) But, as others have written, it's not really intended to be used that way.
- derekp7 5y ago
  Is it valid to take a data point of one, combined with a time element to get an estimate? For example Earth started gaining life shortly (in geological time) after it was able to sustain it. That would indicate that either life arises easily, or that it pre existed the Earth and got seeded (panspermia). Then at the opposite end of the scale is the long time that it took for life to go multi-cellular, and for a space program to be formed by an instance of that life.
paxys 5y ago
> This would come to be known as the "Drake equation," which is considered by many to be one of the most renowned equations in the history of science. Uh, this might be a tad bit hyperbolic. Does anyone even consider it serious science?
- labster 5y ago
  Of course it’s serious science, it’s just thinking about statistics. Of course most of the values are unknown right now, as we are just starting our survey of exoplanets. But it raises lots of questions, and those are good for science.
  - paxys 5y ago
    I don't see how it meets even a single step of the scientific method. You can call it a somewhat scientific thought experiment, if such a thing even exists, but that's about it.
    - s1artibartfast 5y ago
      It is pretty easy to use it generate and test hypotheses, which is frequently done and published in the literature. Common examples include radio and other EM surveys for extraterrestrial signals.
    - bpodgursky 5y ago
      By your definition, "Calculus" is highly unscientific.
      - analog31 5y ago
        Calculus owes some of its development to its use in scientific theories, but also stands alone as a branch of math. One can approach it as a pure exercise in symbol manipulation (as I did as a student). Without trying to precisely define scientific methodology, I think it always needs some connection to empirical evidence. This is the problem with the Drake equation, but also with some other speculative fields like string theory. So I'd say that the Drake equation is scientific in the sense that it's motivated by scientific speculation, but has not yet found a form that can be tested.
jcadam 5y ago
Personally, I'm starting to lean toward the Rare Earth hypothesis. I do, however, like the "solution" posited in the short story "The Crystal Spheres": https://en.wikipedia.org/wiki/The_Crystal_Spheres https://en.wikipedia.org/wiki/The_Crystal_Spheres
- hackeraccount 5y ago
  Everything I've read makes me think life almost certainly exists outside of the Earth, I'm even open to the idea that it exists within the solar system. Complex eukaryotic type life? I'd be that's a lot more rare - consider that prokaryotes look to have popped almost as soon was possible but then it apparently to several billion years for eukaryotes.
cletus 5y ago
"Equation" is an unfortunate name because some view that like the Drake Equation is meant to produce a quantifiable number. It isn't and never was. It's a thought experiment and a way to frame the problem (the article states this explicitly). What has changed is the assumptions about how we would detect a starfaring civilization. 60 years ago we were assuming radio communications because that seemed to be where our future was and, by extension, what we might expect other civilizations to do. Obviously the values in the equation are unknown. We use such things to frame problems that involve unknowns like this. A good example: the anthropic principle [1]. Anyway, the more prevalent line of thinking now is that starfaring civilizations are likely to end up building Dyson swarms. This is a long and complex discussion. There are many objections but those objections tend to suffer from the problem that, if that objection is true, there should be more not less starfaring life (eg any form of FTL). If matter is the ultimate limiter to civilizations then it makes sense that civilizations will try and amass as much of it as possible. It doesn't matter if not every civilization goes this route because even one such galaxy-spanning civilization within a million light years will stand out (based on the IR signature). Even without that it probably wouldn't take more than about 10M years for humanity to colonize the Milky Way. [1]: https://en.wikipedia.org/wiki/Anthropic_principle https://en.wikipedia.org/wiki/Anthropic_principle
- LatteLazy 5y ago
  Wait, do people actually think Dyson swarms are a thing? The amount of time and energy needed to build them always seemed ridiculous to me. Especially as all you gain is energy (which hasn’t proven limiting) and you lose almost everything else (gravity and atmosphere for a start)...
  - mgolawala 5y ago
    I am not at all well informed about this but I imagined a Dyson swarm would sort of grow and evolve organically over time. Not as an end goal in themselves. For example, if you start building space habitats (even if they are enclosed cylinders such that they hold an atmosphere and provide gravity via rotation) you need to put them somewhere. It makes sense to throw them in orbit around the star at some optimal distance (for example at 1AU +/- some amount), if you continue to put more and more such habitats around a star in similar orbits over time, in sufficient numbers, wouldn't they start to resemble a Dyson swarm?
myfavoritedog 5y ago
It seems odd to be conducting the search for extraterrestrial intelligence by looking for radio signals from distant planets. Maybe we should figure out what all these UFOs are here first. https://www.washingtonpost.com/nation/2021/05/17/ufo-sightings-navy-ryan-graves/ https://www.washingtonpost.com/nation/2021/05/17/ufo-sightin...
- jodrellblank 5y ago
  I can't read that past the paywall, but what's your answer to https://xkcd.com/1235/ https://xkcd.com/1235/ ?
  - myfavoritedog 5y ago
    I love the relevance of an XKCD as much as the next guy, but a clever graph doesn’t compare to the admissions of the military and US government that these videos are not faked. They can’t explain these craft that seem to be propelled in ways that are entirely unfamiliar to airforce personnel who are themselves familiar with cutting edge earthling aircraft. https://www.cbsnews.com/news/ufo-military-intelligence-60-minutes-2021-05-16/ https://www.cbsnews.com/news/ufo-military-intelligence-60-mi... [edited for grammar]
    - jodrellblank 5y ago
      And... now? https://old.reddit.com/r/videos/comments/ngwc3h/the_newest_pentagon_confirmed_uap_is_just_bokeh/ https://old.reddit.com/r/videos/comments/ngwc3h/the_newest_p... and https://old.reddit.com/r/videos/comments/ngwc3h/the_newest_pentagon_confirmed_uap_is_just_bokeh/gytokt7/ https://old.reddit.com/r/videos/comments/ngwc3h/the_newest_p...
      - myfavoritedog 5y ago
        That is a good explanation for one of the videos, but it certainly doesn't address others. It also doesn't address first-person sightings by military observers, as interviewed in the video I linked to.
TheOtherHobbes 5y ago
There's a missing term: "How much of our potential budget are we spending trying to fill in the other estimates?" SETI is incredibly poorly funded compared to other science. For a long time it was barely funded at all. There's been an uptick recently, but a project like Breakthrough Listen runs on $10m/yr and gets ridiculously constrained access to telescope time. The remaining SETI projects get by on less than $5m/yr. So SETI as a whole gets about as much funding as one episode of The Mandalorian. No wonder we haven't found anything. We're barely even looking.
- denton-scratch 5y ago
  Why would we allocate ginormous budgets to a project like SETI? Suppose we detected a radio signal from a location outside the solar system, that seemed to bespeak intelligence. That means it must be at least 1.5 LY away. But we haven't yet detected an exoplanet around Alpha Centauri, let alone one with goldilocks properties. But for the sake of argument, let's suppose that we detect a radio signal from Alpha Centauri, and a matching exoplanet. I suppose that would make it reasonable to conclude that (a) we have neighbours, and (b) that they're probably common. But we have only highly-speculative and fantastically expensive ideas about how we might get a human to Alpha Centauri. It would, for example, require a Generation spaceship. I suppose we could imagine exchanging scientific knowledge with the beings of Alpha Centauri, over a radio link - with a ping time of 3 years. And the bandwidth isn't going to be that impressive, either. I totally believe that there is other intelligent life in the Universe; but I simply don't believe that, if they are really intelligent, they would burn their resources on a project that might not be complete before they become extinct. I doubt they're anything like as close as Alpha Centauri, and therefore I doubt that we'll ever encounter them physically. From that point of view, it doesn't make much difference to anything whether they exist or not.
deleted 5y ago
[deleted]
marze 5y ago
I think next year would be a better time to update the equation.
mFixman 5y ago
What I never understood about the Drake equation and the search for intelligent alien life is why people assume that "intelligence" is something special and not something inherently human. There's no reason to see human-like intelligence as one of the infinite amount of properties a life form can have. "Two possibilities exist: we are either the only things in the Universe that regularly speak Swedish or we are not. Both are equally terrifying".
- lovemenot 5y ago
  Yes, I have been saying something like this for years. I believe this is the first time I have seen someone else make the same point here. My dog is looking for signs of extraterrestrial super-olfaction.
c-smile 5y ago
Are we still looking for other forms of life on this very planet? Are we sure now that DNA-based life and only of those four bases is the only form of life that was born here? If "yes" then it means that it is highly probable that other forms of life are also DNA based, no?
xutopia 5y ago
Even with speed of light the farthest message we could have sent would barely peak out of our cosmic neighborhood. We need a powered probe that accelerates outwards sending a message for any chance of being heard out there in any reasonable time.
- behringer 5y ago
  The speed limit of the universe is light speed. If you were to send a powered probe into the universe at almost the speed of light, and then send a light speed signal out on top of that, it would still be sent at the speed of light. Eg, no signal sent from any probe will ever get as far as our first radio signals sent into the universe, unless we find a faster than light solution. This is what Einstein discovered for us, which is called the theory of relativity.
  - kortex 5y ago
    I read it to mean "probe that is moving hella fast and also radiating in every direction." So there is a "contact cone" rather than a "contact sphere," increasing the amount of space interacted with (even if only briefly)
    - behringer 5y ago
      I think if you were to radiate out from any point inside of an enlarging circle, enlarging at the same speed as that circle, I can't see how it would radiate away from that bubble. That said, the signal would be much stronger if you tuned it for specific regions of space.
lamontcg 5y ago
Nope. It seems to be working just fine to spur discussion and though. The replacement seems much less useful. The fact that some of the factors may be close to 1.0 or may be unknowable directly is not a bug.
denton-scratch 5y ago
"by multiplying uncertain variables, the level of uncertainty grows exponentially" No it doesn't. It grows geometrically. "the number of confirmed exoplanets has grown exponentially" That implies that the rate of discovery of exoplanets is proportional to the number already discovered. I've no reason to think that's the case; and it seems really improbable. When a science journalist uses the word "exponential" to mean "very fast", I conclude that I'm reading some kind of low-grade popsci from a lazy writer who thinks fancy words make them look clever. Well, it might to some people; to me, it just makes them look ignorant.
denton-scratch 5y ago
"But considering that the payoff will be the single greatest discovery in the history of humanity" Oh, my goodness. Hyperbole much? Detecting signs of life is all very well; but most (all?) such signals will have come from so far away that either we'll have evolved, or they'll have evolved. The chances that we'll ever meet such beings is minute. I would expect the greatest discovery ever to actually make practical difference to something. The tiny bandwidth and enormous turnaround time for any electromagnetic signal over (say) 20LY will stymie any attempt to transfer useful amounts of information. Probes are more promising; but note that Voyager 1 has travelled just over 1/1,000 of a light-year so far. To travel 20LY, it would need to survive in deep space for 40,000 years. Humans have never built a machine that could survive in working order for more than about 200 years. For such a probe to tell us anything interesting, we'd be faced again with the bandwidth problem; or the probe would have to come back. By the time we got information back, it would be 40,000 years in the future. We know barely anything about human culture 40,000 years ago; if we had launched an interstellar probe 40,000 years ago, we'd have zero cultural memory of that fact by now. So this "greatest discovery" is most likely to fall into the "gosh, that's quite interesting" category, rather than the "most important ever" category.
- w0de0 5y ago
  What’s the bandwidth problem? Could we modulate the light coming from our star just so?
  - denton-scratch 5y ago
    https://space.stackexchange.com/questions/6207/what-bitrates-are-currently-achievable-for-communication-with-interplanetary-spa https://space.stackexchange.com/questions/6207/what-bitrates... The greater the distance, the more the signal is attenuated, so the harder it becomes to distinguish signal from background-noise, so the slower you have to send. 'Modulate the light from our star': Not sure how one might set about that. As things stand, we need extremely sensitive instruments to detect the starlight-modulation caused by orbiting exoplanets. A planetary-scale modulator would give you a bandwidth in the order of one bit per orbit. Supposing we could construct a device that could modulate sunlight, it would need to be big - orders of magnitude bigger than anything humans have ever made. Our interstallar probe would have to deploy such a device on arrival, in order to 'call home'. I suppose it's conceivable, as an idea; but the cost of such a project would be unimaginable, and the benefit would be useless information: e.g. "There is life on this planet; but you have no chance of getting here, and they have no chance of getting to you". That's not actionable information. And you'll be getting the signal 20,000 years after launching the probe; that's the span of all of human civilisation. There's every chance that humans 20,000 years in the future would not be very interested in a signal from a probe launched by their 'primitive' ancestors. That's if they had any cultural memory from their ancestors that there ever was such a probe; but how much do we know about the culture of humans 20,000 years ago? If they had launched a probe, we would have to learn that from fossilised bones, which seems far-fetched.
juancn 5y ago
I think the chance of detecting another civilization right now is rather slim. Maybe in a couple thousand years. I'll try to explain my reasoning. First, a few assumptions: - Life and intelligence are physical processes. Given the starting conditions of the universe, they'll eventually pop up somewhere. - Where it pops up, is random and relatively uniformly distributed in space (as for the density, I don't know) - Humans are an average civilization - For most civilizations it takes about the same time than us from the start of the universe to reach our current level of advancement (given that we presume that we're average). Under these assumptions, we have been detectable for roughly the last 100 years. So we can assume, that it's about the same for an average civilization out there. Even if they're plentiful, it's unlikely that the signals from the close ones would have reached us yet. So everything looks dark. It wouldn't surprise me if in a few thousand years, the sky starts lighting up with signals from other worlds, as the signals from the ones that are reaching detectability start getting to us.

62 points by elorant 5y ago

No, it's time to scrap it, since it never made any sense. You can't talk about probabilities when there's only a single trial, the sample size is 1 and you have no possible way to determine the parameters in the first place.

Out_of_Characte 5y ago
While true that the last parameters are completely unknown (IE, wether a planet with life has intelligent life, and wether they have radio transmission capabilities) the other parameters are something we can most certainly estimate. The absense of precision in this case is why it was written in the first place. "As I planned the meeting, I realized a few day[s] ahead of time we needed an agenda. And so I wrote down all the things you needed to know to predict how hard it's going to be to detect extraterrestrial life. And looking at them, it became pretty evident that if you multiplied all these together, you got a number, N, which is the number of detectable civilizations in our galaxy. This was aimed at the radio search, and not to search for primordial or primitive life forms." So the sample size isn't 1 and there are known ways to detect all but 2 or 3 parameters of the drake equation.
- jcranmer 5y ago
  > So the sample size isn't 1 and there are known ways to detect all but 2 or 3 parameters of the drake equation. Actually, only 2 or 3 parameters of the Drake equation are estimable. (It depends on how you want to define "planets that can potentially support life"--you can argue that the answer is anywhere between 1 and 5 in our own solar system). Everything that talks about the possibility of life evolving, let alone speculating about how it will evolve or the xenosociology of what that life will try to do, is pure conjecture: that's the last 4 values of the equation, more than half of it.
- Grustaf 5y ago
  Ok, you can say that the sample size is the number of planets, but there’s only 1 trial. EDIT: If you go through the factors, only the first three even make sense to talk about. And the third, about "number of planets per star that can potentially support life" can only be discussed in terms of our particular form of life. We have no idea at all what other types of life there could be, much less under what conditions that might happen. The others are completely unknowable. For example: f_i: The fraction of planets with life that actually go on to develop intelligent life (civilizations)" I'm embarrassed even writing it out. How can anyone even start to think that they could come even with 10 orders of magnitude of the right answer, if it's even a well defined probability, which I doubt. We know of exactly one planet with life, and it has intelligent life that emits radio waves. Is that an inevitability, or a one in a trillion fluke? But what bother me the most is how you even think you can talk about probabilities when there's only one trial, and for the later factors, the sample size is most definitely 1. It's just inane.
kelnos 5y ago
You absolutely can talk about probabilities, and it's an interesting thought experiment. You just can't -- yet -- plug in meaningful numbers derived from experimental data.
- Grustaf 5y ago
  Yet? How could you ever hope to be able to say anything about the last five factors until you find another civilisation? By which time you have the answer anyway.
pitched 5y ago
You can’t really get any precision out of it but I think the size of the error bars is interesting, where recent estimates come out somewhere between 10^-13 and 10^8. That makes it a bit more likely that we’re alone than not. https://en.m.wikipedia.org/wiki/Drake_equation#Estimates https://en.m.wikipedia.org/wiki/Drake_equation#Estimates

mvzvm 5y ago

The Drake Equation always felt like gibberish to me. How can you have an equation "used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy" when we have nothing to test it with?

vimacs2 5y ago
I have to disagree. It is useful to be able to quantify the exact state of ignorance that we currently have and as our observational reach expands, the values of the variables in the equation should become less and less fuzzy. The problem isn't with the Drake equation, it's with the pop science articles that extrapolated things from it way beyond the original intent or scope.
- treeman79 5y ago
  Several sets of unknown on an infinite universe, so we know know nothing. However thanks to speed of light the data set is not infinite, just absurd. So we know almost nothing. Given time the expansion of the universe will push all galaxies and stars away from us. The data set will be 1. We now know everything. As expansion continues all hydrogen items will eventually break apart. All life has ended. Nothing now knows us.
kelnos 5y ago
You can certainly have it, you just can't use it with any sense of accuracy until you have more data.
nend 5y ago
Take a look at the article: "Rather than being an actual means for quantifying the number of intelligent species in our galaxy, the purpose of the equation was meant to frame the discussion on SETI. In addition to encapsulating the challenges facing scientists, it was intended to stimulate scientific dialog among those attending the meeting. As Drake would later remark:..." Then follows a video of Drake speaking.
delecti 5y ago
It's a thought experiment meant to highlight known unknowns. If we could perfectly measure each field, we would necessarily have an idea of the number of intelligent civilizations. Each term raises interesting questions, even if they can't be precisely measured (or even guessed at with any confidence).

optimalsolver 5y ago

Learned about this equation from the late Michael Crichton's book "Sphere". A really great first contact science fiction story.

blacktriangle 5y ago
Mandatory to mention when talking about Sphere: read the book first, then watch the movie if you feel so inclined. The book is very very good, the movie is okay but so much of the book takes place in the characters' heads that most of the plot is lost in the film.

lordnacho 5y ago

I'm a bit surprised at the criticism. I always thought of it as more of an equation template than a very specific equation. Of course if you take a specific version of it, there are things it won't capture that we discover over time. But the idea that we can take a very large number and whittle it down seems reasonable.

_rpd 5y ago
Yes, it's inspired a lot of investigations and discussions, which was exactly its purpose. See also: 'solutions' to the Fermi Paradox. https://en.wikipedia.org/wiki/Fermi_paradox https://en.wikipedia.org/wiki/Fermi_paradox

jawns 5y ago

I don't have any philosophic objections to the existence of extraterrestrial life, but what does bug me is when people claim that simply because the universe is so big, that somehow makes it not only likely but practically certain that life has developed on other planets or in other solar systems or galaxies. That kind of thinking presumes some very important information that we just don't have. We are currently unable to enter any coherent value into the portion of the Drake Equation that pertains to how frequently life arises from non-life. We have an admittedly very limited knowledge of events outside of our own planet, but so far as we know, abiogenesis has occurred only once, and from that one event, all life on Earth proceeded. (It's possible that abiogenesis occurred independently multiple times during the beginning of life on Earth, but I don't think we yet have a compelling argument that it must have happened more than once.) My favorite analogy: Suppose you see a number with this pattern: 0.1001000101001000101001000___ What would you say is the likelihood that a 1 is the next number in the sequence? Not that hard to compute a probability, is it? But suppose you see a number with this pattern: 0.1000000000000000000000000___ What is the likelihood that a 1 is the next number in the sequence? You could say the odds are 1-in-25, but that doesn't takes into account the clear pattern we see in the sequence. Unless and until we start to see some more ones pop up, it's reasonable to assume that this is a sequence of infinite zeroes, or at the very least that it could perfectly well be a sequence of infinite zeroes. Suppose the sequence goes on for many trillions of numerals. No one's going to say, "Well, if there are trillions of 0s, it's highly unlikely that there won't be some 1s sprinkled in there somewhere."

kadoban 5y ago
If there are no more 1s, then we need to answer why our position in the universe is unique. That seems like a hard question to answer. It just seems like a _much_ better bet that we aren't the only 1.
- Smithalicious 5y ago
  This reasoning seems flawed, how is it that an answer that doesn't lead to difficult questions is more likely (rather than simply more convenient)?
- 5y ago

29athrowaway 5y ago

Drake equation needs to take in consideration more factors, for sure. Stars have lifecycles, and they can only support life in a stable manner in some stages of that lifecycle. I guess Drake just assumed that stars lifecycles have such a slow progression that for the purposes of determining alien life we can just assume it is constant.

ProAm 5y ago
> Stars have lifecycles, and they can only support life in a stable manner in some stages of that lifecycle. That is what the 'L' is in the formula

jfengel 5y ago

The Drake equation is an example of a more general issue in science: what are we going to spend money on? The Drake equation is treated as fodder for late-night Cheetos-driven college sophomore discussions. But we use it, and siblings, to estimate the inestimable: how much value do we get out of a dollar put towards actually investigating this? No matter what the field, it's always all over the map. Do we want to spend gigabucks on an LHC successor in the hopes of a vast payoff? Do we want to spend megabucks on this specific line of cancer research? Or should we spend the same money on thousands of kilobuck experiments in everything from economics to psychology to polymer chemistry? It's even harder when there isn't actually a dollar value attached. Even if we discover alien life, what's the merit of that? Economically, perhaps nothing, other than sales of "I wanted to believe/and I was right" tee shirts. But in terms of satisfaction, perhaps more than all of the movies and video games ever made put together. That's why we spend so much effort trying to estimate priors that we know are too wild to be of actual value in that calculation. Playing with the Drake equation is fun. That's all. But it does also ultimately inform the expenditure of some resources, even if we don't actually do the math.

redis_mlc 5y ago
> late-night Cheetos-driven college sophomore Welcome to HN! > starfaring civilization Reinforces the point - fanbois confusing scifi with reality.
s1artibartfast 5y ago
Why do anything? Any questions of resource allocation ultimately come down to a question individual and social values, or merit, as you phrased it. Merit is inherently arbitrary. Some people can and do think answering the question of the existence of extraterrestrial life has intrinsic merit and is the single most important society could do. More important than improving global prosperity or even continuation of the species.

ud_0 5y ago

I think (hope?) the Drake equation was never intended as a tool for making realistic estimations, I always thought it was more of a first approximation of how one might go about thinking about modeling when all you have is a sample of one. Specifically the rate of star formation has always been dubious, because there is such an enormous lag between star formation and the emergence of intelligent life (even if we turn out to be an extremely slow outlier), making it unsuitable for estimating the amount of civilizations active at a specific point in time. My personal drake equation would include only factors that are based on the current state of the galaxy. But that's the Drake equation doing its job: making people think about cosmic odds. It doesn't need an update, because I argue it shouldn't be taken literally in the first place. A few times a year, authors put out "new" estimations of the number of galactic civilizations, and to do that there is really not much alternative to chaining together these kinds of probabilities. While they sometimes may or more often may not use the actual Drake equation to do it, its value lies in the basic structure, not in its specific implementation.

ghaff 5y ago
One of the challenges (I won't say problems) with the Drake Equation is we have some sense for some numbers and they're very very large. Which encourages people to use formulations for some of the other terms like "even if we assume this is one in a billion" and this is "one in a million," you still come up with a significant number of civilizations. When, in fact, some other term may be so vanishingly small that it's only happened once. (Or there may be something else, e.g. a great barrier, that's not being taken into account.) But, as others have written, it's not really intended to be used that way.
derekp7 5y ago
Is it valid to take a data point of one, combined with a time element to get an estimate? For example Earth started gaining life shortly (in geological time) after it was able to sustain it. That would indicate that either life arises easily, or that it pre existed the Earth and got seeded (panspermia). Then at the opposite end of the scale is the long time that it took for life to go multi-cellular, and for a space program to be formed by an instance of that life.

paxys 5y ago

> This would come to be known as the "Drake equation," which is considered by many to be one of the most renowned equations in the history of science. Uh, this might be a tad bit hyperbolic. Does anyone even consider it serious science?

labster 5y ago
Of course it’s serious science, it’s just thinking about statistics. Of course most of the values are unknown right now, as we are just starting our survey of exoplanets. But it raises lots of questions, and those are good for science.
- paxys 5y ago
  I don't see how it meets even a single step of the scientific method. You can call it a somewhat scientific thought experiment, if such a thing even exists, but that's about it.
  - s1artibartfast 5y ago
    It is pretty easy to use it generate and test hypotheses, which is frequently done and published in the literature. Common examples include radio and other EM surveys for extraterrestrial signals.
  - bpodgursky 5y ago
    By your definition, "Calculus" is highly unscientific.
    - analog31 5y ago
      Calculus owes some of its development to its use in scientific theories, but also stands alone as a branch of math. One can approach it as a pure exercise in symbol manipulation (as I did as a student). Without trying to precisely define scientific methodology, I think it always needs some connection to empirical evidence. This is the problem with the Drake equation, but also with some other speculative fields like string theory. So I'd say that the Drake equation is scientific in the sense that it's motivated by scientific speculation, but has not yet found a form that can be tested.

jcadam 5y ago

Personally, I'm starting to lean toward the Rare Earth hypothesis. I do, however, like the "solution" posited in the short story "The Crystal Spheres": https://en.wikipedia.org/wiki/The_Crystal_Spheres https://en.wikipedia.org/wiki/The_Crystal_Spheres

hackeraccount 5y ago
Everything I've read makes me think life almost certainly exists outside of the Earth, I'm even open to the idea that it exists within the solar system. Complex eukaryotic type life? I'd be that's a lot more rare - consider that prokaryotes look to have popped almost as soon was possible but then it apparently to several billion years for eukaryotes.

cletus 5y ago

"Equation" is an unfortunate name because some view that like the Drake Equation is meant to produce a quantifiable number. It isn't and never was. It's a thought experiment and a way to frame the problem (the article states this explicitly). What has changed is the assumptions about how we would detect a starfaring civilization. 60 years ago we were assuming radio communications because that seemed to be where our future was and, by extension, what we might expect other civilizations to do. Obviously the values in the equation are unknown. We use such things to frame problems that involve unknowns like this. A good example: the anthropic principle [1]. Anyway, the more prevalent line of thinking now is that starfaring civilizations are likely to end up building Dyson swarms. This is a long and complex discussion. There are many objections but those objections tend to suffer from the problem that, if that objection is true, there should be more not less starfaring life (eg any form of FTL). If matter is the ultimate limiter to civilizations then it makes sense that civilizations will try and amass as much of it as possible. It doesn't matter if not every civilization goes this route because even one such galaxy-spanning civilization within a million light years will stand out (based on the IR signature). Even without that it probably wouldn't take more than about 10M years for humanity to colonize the Milky Way. [1]: https://en.wikipedia.org/wiki/Anthropic_principle https://en.wikipedia.org/wiki/Anthropic_principle

LatteLazy 5y ago
Wait, do people actually think Dyson swarms are a thing? The amount of time and energy needed to build them always seemed ridiculous to me. Especially as all you gain is energy (which hasn’t proven limiting) and you lose almost everything else (gravity and atmosphere for a start)...
- mgolawala 5y ago
  I am not at all well informed about this but I imagined a Dyson swarm would sort of grow and evolve organically over time. Not as an end goal in themselves. For example, if you start building space habitats (even if they are enclosed cylinders such that they hold an atmosphere and provide gravity via rotation) you need to put them somewhere. It makes sense to throw them in orbit around the star at some optimal distance (for example at 1AU +/- some amount), if you continue to put more and more such habitats around a star in similar orbits over time, in sufficient numbers, wouldn't they start to resemble a Dyson swarm?

myfavoritedog 5y ago

It seems odd to be conducting the search for extraterrestrial intelligence by looking for radio signals from distant planets. Maybe we should figure out what all these UFOs are here first. https://www.washingtonpost.com/nation/2021/05/17/ufo-sightings-navy-ryan-graves/ https://www.washingtonpost.com/nation/2021/05/17/ufo-sightin...

jodrellblank 5y ago
I can't read that past the paywall, but what's your answer to https://xkcd.com/1235/ https://xkcd.com/1235/ ?
- myfavoritedog 5y ago
  I love the relevance of an XKCD as much as the next guy, but a clever graph doesn’t compare to the admissions of the military and US government that these videos are not faked. They can’t explain these craft that seem to be propelled in ways that are entirely unfamiliar to airforce personnel who are themselves familiar with cutting edge earthling aircraft. https://www.cbsnews.com/news/ufo-military-intelligence-60-minutes-2021-05-16/ https://www.cbsnews.com/news/ufo-military-intelligence-60-mi... [edited for grammar]
  - jodrellblank 5y ago
    And... now? https://old.reddit.com/r/videos/comments/ngwc3h/the_newest_pentagon_confirmed_uap_is_just_bokeh/ https://old.reddit.com/r/videos/comments/ngwc3h/the_newest_p... and https://old.reddit.com/r/videos/comments/ngwc3h/the_newest_pentagon_confirmed_uap_is_just_bokeh/gytokt7/ https://old.reddit.com/r/videos/comments/ngwc3h/the_newest_p...
    - myfavoritedog 5y ago
      That is a good explanation for one of the videos, but it certainly doesn't address others. It also doesn't address first-person sightings by military observers, as interviewed in the video I linked to.

TheOtherHobbes 5y ago

There's a missing term: "How much of our potential budget are we spending trying to fill in the other estimates?" SETI is incredibly poorly funded compared to other science. For a long time it was barely funded at all. There's been an uptick recently, but a project like Breakthrough Listen runs on $10m/yr and gets ridiculously constrained access to telescope time. The remaining SETI projects get by on less than $5m/yr. So SETI as a whole gets about as much funding as one episode of The Mandalorian. No wonder we haven't found anything. We're barely even looking.

denton-scratch 5y ago
Why would we allocate ginormous budgets to a project like SETI? Suppose we detected a radio signal from a location outside the solar system, that seemed to bespeak intelligence. That means it must be at least 1.5 LY away. But we haven't yet detected an exoplanet around Alpha Centauri, let alone one with goldilocks properties. But for the sake of argument, let's suppose that we detect a radio signal from Alpha Centauri, and a matching exoplanet. I suppose that would make it reasonable to conclude that (a) we have neighbours, and (b) that they're probably common. But we have only highly-speculative and fantastically expensive ideas about how we might get a human to Alpha Centauri. It would, for example, require a Generation spaceship. I suppose we could imagine exchanging scientific knowledge with the beings of Alpha Centauri, over a radio link - with a ping time of 3 years. And the bandwidth isn't going to be that impressive, either. I totally believe that there is other intelligent life in the Universe; but I simply don't believe that, if they are really intelligent, they would burn their resources on a project that might not be complete before they become extinct. I doubt they're anything like as close as Alpha Centauri, and therefore I doubt that we'll ever encounter them physically. From that point of view, it doesn't make much difference to anything whether they exist or not.

deleted 5y ago

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marze 5y ago

I think next year would be a better time to update the equation.

mFixman 5y ago

What I never understood about the Drake equation and the search for intelligent alien life is why people assume that "intelligence" is something special and not something inherently human. There's no reason to see human-like intelligence as one of the infinite amount of properties a life form can have. "Two possibilities exist: we are either the only things in the Universe that regularly speak Swedish or we are not. Both are equally terrifying".

lovemenot 5y ago
Yes, I have been saying something like this for years. I believe this is the first time I have seen someone else make the same point here. My dog is looking for signs of extraterrestrial super-olfaction.

c-smile 5y ago

Are we still looking for other forms of life on this very planet? Are we sure now that DNA-based life and only of those four bases is the only form of life that was born here? If "yes" then it means that it is highly probable that other forms of life are also DNA based, no?

xutopia 5y ago

Even with speed of light the farthest message we could have sent would barely peak out of our cosmic neighborhood. We need a powered probe that accelerates outwards sending a message for any chance of being heard out there in any reasonable time.

behringer 5y ago
The speed limit of the universe is light speed. If you were to send a powered probe into the universe at almost the speed of light, and then send a light speed signal out on top of that, it would still be sent at the speed of light. Eg, no signal sent from any probe will ever get as far as our first radio signals sent into the universe, unless we find a faster than light solution. This is what Einstein discovered for us, which is called the theory of relativity.
- kortex 5y ago
  I read it to mean "probe that is moving hella fast and also radiating in every direction." So there is a "contact cone" rather than a "contact sphere," increasing the amount of space interacted with (even if only briefly)
  - behringer 5y ago
    I think if you were to radiate out from any point inside of an enlarging circle, enlarging at the same speed as that circle, I can't see how it would radiate away from that bubble. That said, the signal would be much stronger if you tuned it for specific regions of space.

lamontcg 5y ago

Nope. It seems to be working just fine to spur discussion and though. The replacement seems much less useful. The fact that some of the factors may be close to 1.0 or may be unknowable directly is not a bug.

denton-scratch 5y ago

"by multiplying uncertain variables, the level of uncertainty grows exponentially" No it doesn't. It grows geometrically. "the number of confirmed exoplanets has grown exponentially" That implies that the rate of discovery of exoplanets is proportional to the number already discovered. I've no reason to think that's the case; and it seems really improbable. When a science journalist uses the word "exponential" to mean "very fast", I conclude that I'm reading some kind of low-grade popsci from a lazy writer who thinks fancy words make them look clever. Well, it might to some people; to me, it just makes them look ignorant.

denton-scratch 5y ago

"But considering that the payoff will be the single greatest discovery in the history of humanity" Oh, my goodness. Hyperbole much? Detecting signs of life is all very well; but most (all?) such signals will have come from so far away that either we'll have evolved, or they'll have evolved. The chances that we'll ever meet such beings is minute. I would expect the greatest discovery ever to actually make practical difference to something. The tiny bandwidth and enormous turnaround time for any electromagnetic signal over (say) 20LY will stymie any attempt to transfer useful amounts of information. Probes are more promising; but note that Voyager 1 has travelled just over 1/1,000 of a light-year so far. To travel 20LY, it would need to survive in deep space for 40,000 years. Humans have never built a machine that could survive in working order for more than about 200 years. For such a probe to tell us anything interesting, we'd be faced again with the bandwidth problem; or the probe would have to come back. By the time we got information back, it would be 40,000 years in the future. We know barely anything about human culture 40,000 years ago; if we had launched an interstellar probe 40,000 years ago, we'd have zero cultural memory of that fact by now. So this "greatest discovery" is most likely to fall into the "gosh, that's quite interesting" category, rather than the "most important ever" category.

w0de0 5y ago
What’s the bandwidth problem? Could we modulate the light coming from our star just so?
- denton-scratch 5y ago
  https://space.stackexchange.com/questions/6207/what-bitrates-are-currently-achievable-for-communication-with-interplanetary-spa https://space.stackexchange.com/questions/6207/what-bitrates... The greater the distance, the more the signal is attenuated, so the harder it becomes to distinguish signal from background-noise, so the slower you have to send. 'Modulate the light from our star': Not sure how one might set about that. As things stand, we need extremely sensitive instruments to detect the starlight-modulation caused by orbiting exoplanets. A planetary-scale modulator would give you a bandwidth in the order of one bit per orbit. Supposing we could construct a device that could modulate sunlight, it would need to be big - orders of magnitude bigger than anything humans have ever made. Our interstallar probe would have to deploy such a device on arrival, in order to 'call home'. I suppose it's conceivable, as an idea; but the cost of such a project would be unimaginable, and the benefit would be useless information: e.g. "There is life on this planet; but you have no chance of getting here, and they have no chance of getting to you". That's not actionable information. And you'll be getting the signal 20,000 years after launching the probe; that's the span of all of human civilisation. There's every chance that humans 20,000 years in the future would not be very interested in a signal from a probe launched by their 'primitive' ancestors. That's if they had any cultural memory from their ancestors that there ever was such a probe; but how much do we know about the culture of humans 20,000 years ago? If they had launched a probe, we would have to learn that from fossilised bones, which seems far-fetched.

juancn 5y ago

I think the chance of detecting another civilization right now is rather slim. Maybe in a couple thousand years. I'll try to explain my reasoning. First, a few assumptions: - Life and intelligence are physical processes. Given the starting conditions of the universe, they'll eventually pop up somewhere. - Where it pops up, is random and relatively uniformly distributed in space (as for the density, I don't know) - Humans are an average civilization - For most civilizations it takes about the same time than us from the start of the universe to reach our current level of advancement (given that we presume that we're average). Under these assumptions, we have been detectable for roughly the last 100 years. So we can assume, that it's about the same for an average civilization out there. Even if they're plentiful, it's unlikely that the signals from the close ones would have reached us yet. So everything looks dark. It wouldn't surprise me if in a few thousand years, the sky starts lighting up with signals from other worlds, as the signals from the ones that are reaching detectability start getting to us.