8 ms·

Bayesian methods to provide probablistic solution for the Drake equation (2019)

49 points by benbreen 3y ago

adastra22 3y ago
Interesting to see this show up. This was a very formative paper for me. If correct—and it certainly seems correct to me—then it completely dissolves the Fermi paradox. And yet nobody seems to be aware of it, and both the popular and scientific press continue with the “where are they?” Fermi paradox headlines. What I learned was that just figuring out the right answer is indifferent to change people’s minds, even in science.
- jwocky 3y ago
  What was the conclusion of this paper? The link's conclusion was truncated.
  - _a_a_a_ 3y ago
    It's in the abstrct, right at the top
    - _zoltan_ 3y ago
      You could have just stayed silent.
      - _a_a_a_ 3y ago
        Why, was there a joke I ruined or something?
    - yreg 3y ago
      It says only >That said, the results indicate that the probability we are alone (<1) in the galaxy is significant, while the maximum number of contemporary civilizations might be as few as a thousand. That's not very useful. The full paper is available on scihub though.
      - _a_a_a_ 3y ago
        Err, what exactly were you expecting, their telephone numbers? You got figures and probabilities in the conclusion and I can't see what else you could reasonably hope for.
        yreg 3y ago
        I (and I believe jwocky as well) expected some kind of rationale. There are no figures nor probabilities supporting the conclusion in the linked article. Of course if one pirates the paper they can learn more.
        _a_a_a_ 3y ago
        Ah, the 'method' part. Gotcha. You might email the author and ask for a copy. They're often surprisingly willing to hand out individual copies.
- _a_a_a_ 3y ago
  > What I learned was that just figuring out the right answer is indifferent to change people’s minds, even in science Seems too strong a conclusion.
  - ghaff 3y ago
    The Drake equation does let you model numbers you think you know with some certainty, numbers that known to be very large, and some known unknowns. But even leaving aside unknown unknowns, the modeling of some known unknowns can boil to making models that assume numbers that are very small but (obviously) not zero because we're sitting here.
- karpierz 3y ago
  > And yet nobody seems to be aware of it, and both the popular and scientific press continue with the “where are they?” Fermi paradox headlines. A reasonable explanation here is that the paper is not correct because it relies on unfounded priors, which is generally where most Bayesian work falls flat.
  - DennisP 3y ago
    So your prior is that Bayesian papers are likely to have unfounded priors. Now I'm wondering how well-founded your prior is.
  - _yb2s 3y ago
    You have it backwards- the traditional Drake equation relies on unfounded priors, and by using a Bayesian approach they have avoided that problem. Instead of making up terms from nothing like the Drake equation, they are able to represent only the data we actually have, and leave the rest uncertain. The priors are carefully encoding the actual information they have, and incorporating the extreme lack of prior knowledge as uniform or nearly uniform priors over an extremely wide range for the terms we have no data on. That is the basic takeaway here- with almost no knowledge about a large number of factors (as the Drake equation is constructed), there is an extremely high chance that once of those unknown factors is actually nearly zero, even when your expectation value for each (e.g. what would have been used in the traditional Drake equation) is relatively high. N (number of civilizations) therefore approaches zero, even if there is no single term that you are pretty sure is near zero. The Bayesian approach here allows for a rigorous representation of our (extreme lack of) knowledge and gets to the truth of the matter: civilizations face a huge number of possible bottlenecks, each of which we know almost nothing about the probabilities of. This means, there is a strong chance at least one of those is a massive filter, even if we don't know which.
    - vlovich123 3y ago
      While I agree with both the approach and result intuitively, the assumption of uniform unknown priors feels like it could be a huge source of errors
- narag 3y ago
  What I learned was that just figuring out the right answer is indifferent to change people’s minds, even in science. The further from experimental confirmation some question is, the bigger chance that people will ignore evidence in favour of their pet belief. There's a kind of people that likes to believe that we're too far away from our nearest neighbors, that we'll never spread to other stars, nobody will come and that we'll get extinct soon. Not sure why they think this way. What I do know is that somehow they find comfort believing that. Fermi paradox is music to their ears because it seems to confirm their mindset.
- kelseyfrog 3y ago
  It's ripe for YouTubers cum science communicators to jump on.
- JumpCrisscross 3y ago
  > yet nobody seems to be aware of it I'm a rare earthier. But I've never found the Drake equation useful for estimation. The knowns are drowned by the unknowns, which we do not know to even vast orders of magnitude. The probability of abiogenesis or multicellular life forming are simply beyond our present understanding of biochemistry. We know they are rare. But the entire equation turns on whether they are merely rare, or vanishingly so.
- goatlover 3y ago
  "With so few concurrent civilizations, and such large distances, it is little surprise that the SETI project has not found that alien signal. Our nearest neighbor is 4 light years away, and there are under 100 stars within 50 light years, the total of the project's existence." That doesn't change Enrico Fermi's calculations on how long it might take an alien civilization to colonize the galaxy (max 100 million years). Or spam every solar system with Von Neumann probes. Or build giant radio emitters and send them out to various parts of the galaxy to ensure coverage. As long as there's a decent chance other alien civilizations have emerged before our own in the Milky Way, there is a paradox until we know why they aren't detectable. Or seeing Type 3 civilizations in other galaxies.
- yreg 3y ago
  >This was a very formative paper for me. If correct—and it certainly seems correct to me—then it completely dissolves the Fermi paradox. Could you please explain it then? Make the argument that dissolves FP.
  - adastra22 3y ago
    The paper shows that when multiplying seven unknown numbers together, the expected result is much, much less than multiplying seven fixed estimates together. Sagan et al come up with a long sequence of reasonable sounding estimates that when multiplied together result in, say, N=10000, that is ten thousand advanced civilizations in our own galaxy alone. But each one of the terms involved in that calculation was highly uncertain. This paper shows that if you multiply the probability distribution for N_a and N_b together and then sample, you get a value less than sampling N_a and N_b separately and then multiplying, as Drake, Sagan, et al do. If you perform the calculation properly using their very same estimated terms, but multiplying probability distributions instead of pre-sampling, you end up with an aggregate N value very close to 1. Meaning we should expect to be alone, and therefore no paradox.
smiley1437 3y ago
The takeaway: "That said, the results indicate that the probability we are alone (<1) in the galaxy is significant, while the maximum number of contemporary civilizations might be as few as a thousand." A thousand civs spread across a galaxy means there is a low probability of meeting live aliens, but does that mean xenoarchaeology could be a thing?
- hgsgm 3y ago
  Galaxy is impractically huge. 3-dimensions is infinitely bigger than 2
  - mcpackieh 3y ago
    > Galaxy is impractically huge. Yes, but also no... There are about 4x10^11 stars in the Milky Way galaxy, which from an exploration standpoint is massive. But 10^11 isn't exactly an inconceivably large number... let's suppose for the sake of argument that the development of complex multicellular life capable of creating and using radios is 'gated' by only two independent one in a million chances per star.. that's already 1 in 10^12. For 4x10^11 stars in a galaxy, that would mean the galaxy has a 2/3rds chance of not having even one star system with radio-capable life. (1 - 1/10^12) ^ (4x10^11) = 0.67
- PheonixPharts 3y ago
  > but does that mean xenoarchaeology My favorite "crazy theory" is that the Paleocene–Eocene Thermal Maximum (PETM) was caused by a previous industrial civilization that, like us, found a bunch of easy to access hydrocarbons, naively dug them up and reached the same climate change problem that we did, ultimately wiping them out. Of course there is 0 evidence for this at all, but it was also more than 50 million years ago. If you look into it basically nothing about an advanced industrial civilization would likely survive to make it into the geological record for us to observe. The only reason to even entertain this hypothesis is that the PETM also experience a very rapid increase in atmospheric CO2 and we aren't entirely sure why. Unfortunately this means that there's probably not much chance for a rich field of xenoarchaeology to exist since it's not even possible to do this on our own planet. What is an interesting thought experiment is: Suppose we realized we as a civilization were doomed and wanted to sent a message to future industrial civilization on Earth warning them about being too aggressive with hydrocarbon usage. To my knowledge there is no known method to ensure a message could be sent that far in the future, but it's fun to try to think of ways we could send a message to a future, essentially, alien civilization here on Earth.
wonderwonder 3y ago
We don't even know if there is life on the moons of planets in our solar system. If we find life on Europa, Enceladus, Ganymede or any of a handful of other potential relatively local moons then the odds of life being rampant in the galaxy are pretty high. We just haven't reached the technological level to know one way or another.
smif 3y ago
The paper seems to be paywalled so I have no clue about how they arrived here, but this: "That said, the results indicate that the probability we are alone (<1) in the galaxy is significant, while the maximum number of contemporary civilizations might be as few as a thousand." Doesn't seem to really answer anything. Isn't this just a really fancy way of saying "we don't know the solution to the Drake equation"? It could be a 99.999999...% (<100%) chance of being alone, it could be a 0% chance, or anything in between. Given the title of the paper, this is a very loose definition of "solution" for the Drake equation ("it could be anything!").
- adastra22 3y ago
  It shows that people doing Drake equation estimates we’re doing their math wrong, and using their own numbers but accounting for uncertainty correctly you get estimates much closer to N=1.

49 points by benbreen 3y ago

Interesting to see this show up. This was a very formative paper for me. If correct—and it certainly seems correct to me—then it completely dissolves the Fermi paradox. And yet nobody seems to be aware of it, and both the popular and scientific press continue with the “where are they?” Fermi paradox headlines. What I learned was that just figuring out the right answer is indifferent to change people’s minds, even in science.

jwocky 3y ago
What was the conclusion of this paper? The link's conclusion was truncated.
- _a_a_a_ 3y ago
  It's in the abstrct, right at the top
  - _zoltan_ 3y ago
    You could have just stayed silent.
    - _a_a_a_ 3y ago
      Why, was there a joke I ruined or something?
  - yreg 3y ago
    It says only >That said, the results indicate that the probability we are alone (<1) in the galaxy is significant, while the maximum number of contemporary civilizations might be as few as a thousand. That's not very useful. The full paper is available on scihub though.
    - _a_a_a_ 3y ago
      Err, what exactly were you expecting, their telephone numbers? You got figures and probabilities in the conclusion and I can't see what else you could reasonably hope for.
      - yreg 3y ago
        I (and I believe jwocky as well) expected some kind of rationale. There are no figures nor probabilities supporting the conclusion in the linked article. Of course if one pirates the paper they can learn more.
        _a_a_a_ 3y ago
        Ah, the 'method' part. Gotcha. You might email the author and ask for a copy. They're often surprisingly willing to hand out individual copies.
_a_a_a_ 3y ago
> What I learned was that just figuring out the right answer is indifferent to change people’s minds, even in science Seems too strong a conclusion.
- ghaff 3y ago
  The Drake equation does let you model numbers you think you know with some certainty, numbers that known to be very large, and some known unknowns. But even leaving aside unknown unknowns, the modeling of some known unknowns can boil to making models that assume numbers that are very small but (obviously) not zero because we're sitting here.
karpierz 3y ago
> And yet nobody seems to be aware of it, and both the popular and scientific press continue with the “where are they?” Fermi paradox headlines. A reasonable explanation here is that the paper is not correct because it relies on unfounded priors, which is generally where most Bayesian work falls flat.
- DennisP 3y ago
  So your prior is that Bayesian papers are likely to have unfounded priors. Now I'm wondering how well-founded your prior is.
- _yb2s 3y ago
  You have it backwards- the traditional Drake equation relies on unfounded priors, and by using a Bayesian approach they have avoided that problem. Instead of making up terms from nothing like the Drake equation, they are able to represent only the data we actually have, and leave the rest uncertain. The priors are carefully encoding the actual information they have, and incorporating the extreme lack of prior knowledge as uniform or nearly uniform priors over an extremely wide range for the terms we have no data on. That is the basic takeaway here- with almost no knowledge about a large number of factors (as the Drake equation is constructed), there is an extremely high chance that once of those unknown factors is actually nearly zero, even when your expectation value for each (e.g. what would have been used in the traditional Drake equation) is relatively high. N (number of civilizations) therefore approaches zero, even if there is no single term that you are pretty sure is near zero. The Bayesian approach here allows for a rigorous representation of our (extreme lack of) knowledge and gets to the truth of the matter: civilizations face a huge number of possible bottlenecks, each of which we know almost nothing about the probabilities of. This means, there is a strong chance at least one of those is a massive filter, even if we don't know which.
  - vlovich123 3y ago
    While I agree with both the approach and result intuitively, the assumption of uniform unknown priors feels like it could be a huge source of errors
narag 3y ago
What I learned was that just figuring out the right answer is indifferent to change people’s minds, even in science. The further from experimental confirmation some question is, the bigger chance that people will ignore evidence in favour of their pet belief. There's a kind of people that likes to believe that we're too far away from our nearest neighbors, that we'll never spread to other stars, nobody will come and that we'll get extinct soon. Not sure why they think this way. What I do know is that somehow they find comfort believing that. Fermi paradox is music to their ears because it seems to confirm their mindset.
kelseyfrog 3y ago
It's ripe for YouTubers cum science communicators to jump on.
JumpCrisscross 3y ago
> yet nobody seems to be aware of it I'm a rare earthier. But I've never found the Drake equation useful for estimation. The knowns are drowned by the unknowns, which we do not know to even vast orders of magnitude. The probability of abiogenesis or multicellular life forming are simply beyond our present understanding of biochemistry. We know they are rare. But the entire equation turns on whether they are merely rare, or vanishingly so.
goatlover 3y ago
"With so few concurrent civilizations, and such large distances, it is little surprise that the SETI project has not found that alien signal. Our nearest neighbor is 4 light years away, and there are under 100 stars within 50 light years, the total of the project's existence." That doesn't change Enrico Fermi's calculations on how long it might take an alien civilization to colonize the galaxy (max 100 million years). Or spam every solar system with Von Neumann probes. Or build giant radio emitters and send them out to various parts of the galaxy to ensure coverage. As long as there's a decent chance other alien civilizations have emerged before our own in the Milky Way, there is a paradox until we know why they aren't detectable. Or seeing Type 3 civilizations in other galaxies.
yreg 3y ago
>This was a very formative paper for me. If correct—and it certainly seems correct to me—then it completely dissolves the Fermi paradox. Could you please explain it then? Make the argument that dissolves FP.
- adastra22 3y ago
  The paper shows that when multiplying seven unknown numbers together, the expected result is much, much less than multiplying seven fixed estimates together. Sagan et al come up with a long sequence of reasonable sounding estimates that when multiplied together result in, say, N=10000, that is ten thousand advanced civilizations in our own galaxy alone. But each one of the terms involved in that calculation was highly uncertain. This paper shows that if you multiply the probability distribution for N_a and N_b together and then sample, you get a value less than sampling N_a and N_b separately and then multiplying, as Drake, Sagan, et al do. If you perform the calculation properly using their very same estimated terms, but multiplying probability distributions instead of pre-sampling, you end up with an aggregate N value very close to 1. Meaning we should expect to be alone, and therefore no paradox.

smiley1437 3y ago

The takeaway: "That said, the results indicate that the probability we are alone (<1) in the galaxy is significant, while the maximum number of contemporary civilizations might be as few as a thousand." A thousand civs spread across a galaxy means there is a low probability of meeting live aliens, but does that mean xenoarchaeology could be a thing?

hgsgm 3y ago
Galaxy is impractically huge. 3-dimensions is infinitely bigger than 2
- mcpackieh 3y ago
  > Galaxy is impractically huge. Yes, but also no... There are about 4x10^11 stars in the Milky Way galaxy, which from an exploration standpoint is massive. But 10^11 isn't exactly an inconceivably large number... let's suppose for the sake of argument that the development of complex multicellular life capable of creating and using radios is 'gated' by only two independent one in a million chances per star.. that's already 1 in 10^12. For 4x10^11 stars in a galaxy, that would mean the galaxy has a 2/3rds chance of not having even one star system with radio-capable life. (1 - 1/10^12) ^ (4x10^11) = 0.67
PheonixPharts 3y ago
> but does that mean xenoarchaeology My favorite "crazy theory" is that the Paleocene–Eocene Thermal Maximum (PETM) was caused by a previous industrial civilization that, like us, found a bunch of easy to access hydrocarbons, naively dug them up and reached the same climate change problem that we did, ultimately wiping them out. Of course there is 0 evidence for this at all, but it was also more than 50 million years ago. If you look into it basically nothing about an advanced industrial civilization would likely survive to make it into the geological record for us to observe. The only reason to even entertain this hypothesis is that the PETM also experience a very rapid increase in atmospheric CO2 and we aren't entirely sure why. Unfortunately this means that there's probably not much chance for a rich field of xenoarchaeology to exist since it's not even possible to do this on our own planet. What is an interesting thought experiment is: Suppose we realized we as a civilization were doomed and wanted to sent a message to future industrial civilization on Earth warning them about being too aggressive with hydrocarbon usage. To my knowledge there is no known method to ensure a message could be sent that far in the future, but it's fun to try to think of ways we could send a message to a future, essentially, alien civilization here on Earth.

wonderwonder 3y ago

We don't even know if there is life on the moons of planets in our solar system. If we find life on Europa, Enceladus, Ganymede or any of a handful of other potential relatively local moons then the odds of life being rampant in the galaxy are pretty high. We just haven't reached the technological level to know one way or another.

smif 3y ago

The paper seems to be paywalled so I have no clue about how they arrived here, but this: "That said, the results indicate that the probability we are alone (<1) in the galaxy is significant, while the maximum number of contemporary civilizations might be as few as a thousand." Doesn't seem to really answer anything. Isn't this just a really fancy way of saying "we don't know the solution to the Drake equation"? It could be a 99.999999...% (<100%) chance of being alone, it could be a 0% chance, or anything in between. Given the title of the paper, this is a very loose definition of "solution" for the Drake equation ("it could be anything!").

adastra22 3y ago
It shows that people doing Drake equation estimates we’re doing their math wrong, and using their own numbers but accounting for uncertainty correctly you get estimates much closer to N=1.