[HN Gopher] Bayesian methods to provide probablistic solution fo...
___________________________________________________________________
Bayesian methods to provide probablistic solution for the Drake
equation (2019)
Author : benbreen
Score : 45 points
Date : 2023-07-20 17:28 UTC (2 days ago)
(HTM) web link (www.sciencedirect.com)
(TXT) w3m dump (www.sciencedirect.com)
| smiley1437 wrote:
| 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?
| goatlover wrote:
| Fermi's calculation was that it would take a civilization
| between and 1 and 100 million years to colonize a galaxy at
| sub-light speeds. There has been ample time for multiple
| civilizations to have done this. So where is everyone?
|
| If there's been on average a thousand civs spread across the
| Milky Way for the past 5 billion years, then we need something
| else to explain why none of them have colonized the galaxy.
| PheonixPharts wrote:
| > 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.
| brian_cloutier wrote:
| Why would they have left no traces? Dinosaurs lived ~200 M
| years ago and left enough traces for us to discover them.
| Wouldn't an industrial civilization 50 mya have left some
| kind of refined metallic artifacts? Even if _most_ traces are
| eroded away with time it seems difficult to imagine every
| trace of a global industrial civilization would disappear.
|
| There also don't appear to have been any spikes in
| atmospheric carbon dioxide during the relevant period: https:
| //en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_at...
|
| Though maybe you were looking at a data source with better
| resolution?
| dadoomer wrote:
| The answer is that the traces are not super easy to find,
| depending on how we characterize what traces are in the
| first place. The question posed is known as the "Silurian
| Hypothesis":
|
| https://www.scientificamerican.com/article/could-an-
| industri...
| secant wrote:
| > 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.
|
| I think you've reached this statement too eagerly but would
| be interested to discuss this point. Do you mean that the
| materials they used would have disintegrated and their
| (presumably carbon-based lifeform) bodies wouldn't have left
| any fossils?
|
| My main thoughts on this come from reading Vernor Vinge's [1]
| excellent Marooned in Realtime which discusses some of the
| condundrums resulting from transferring information over
| massive periods of time. I think part of it talks about
| subduction zones where everything is eventually riven back
| into the Earth's mantle, essentially lost to any kind of
| current archaelogical techniques.
|
| [1] https://en.wikipedia.org/wiki/Marooned_in_Realtime
| smiley1437 wrote:
| Good point! The longest-lived artifacts would probably have
| to be somewhere with much less weather and geological
| activity than the surface of the earth. Maybe if you put a
| structure in orbit or perhaps on the moon?
|
| Paradoxically, extending on your thought - I guess anywhere
| with living conditions similar to earth (oxygen atmosphere,
| water, weather, etc) would not be conducive to long term
| archival of civilization artifacts.
|
| So you'd have to look at 'dead' places if you want to find
| evidence of civilization. Or stumble across an derelict
| megastructure (dyson sphere\niven ring\etc)
| hgsgm wrote:
| Galaxy is impractically huge. 3-dimensions is infinitely bigger
| than 2
| mcpackieh wrote:
| > _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
| wonderwonder wrote:
| 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.
| adastra22 wrote:
| 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.
| karpierz wrote:
| > 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.
| UniverseHacker wrote:
| 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 wrote:
| 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
| UniverseHacker wrote:
| They are demonstrating a fundamental flaw in the logical
| reasoning behind the original Drake equation, that is
| robust to specific choices of distributions, or
| parameters to include or exclude.
|
| Anytime you multiply a large number of uncertain
| probability distributions, the resulting posterior will
| have most of the probability mass near zero. This result
| is not sensitive to which distribution or bounds you
| choose. The Drake equation is nonsense, because it is
| effectively assuming certainty about every single term-
| and that is the _only_ way to produce a result much
| higher than zero.
|
| When you are multiplying seven unknown together, you can
| be fairly certain that the result is close to zero
| without knowing the value of any of the terms, unless you
| have some real information that none of terms can be near
| zero.
| jncfhnb wrote:
| This is some dumb second order Bayesian reasoning. You're
| declaring a prior for arbitrary random variables as if
| their distributions themselves are sampled from a
| distribution. They are not.
|
| You cannot be certain that seven random things multiplied
| together is close to zero. That statement is very
| obviously wrong.
|
| Further "near zero" is a misleading term at best because
| it neglects to mention that we are multiplying it by a
| large number to get an expected value.
| mjburgess wrote:
| Distributions are sampled from distributions -- it is
| this problem which makes global scepticism an even
| minimally interesting problem.
|
| When faced with "global, recursive" epistemic problems
| one arrives at an extremely power-law asymmetric
| distribution where the "bayesian value" of almost all
| evidence is near zero.
|
| We live our entire lives in this "nero zero" range, and
| i'd suppose, this makes a "pure bayesian" solution to the
| problem of knowledge deficient. Since we succeed in
| knowing, so we succeed in making hyperfine
| determinations.
|
| This sort of "hyperfine epistemology" works globally to
| allow us to "know at all", but as you're sensing here --
| it's pretty much useless for any local problem.
|
| Perhaps this is just the single up-side of the bayesian
| approach to the drake eqn: it shows how impossible it is
| to state such an eqn, let alone evaluate it. We cannot, a
| priori, make such hyperfine determiniations on such
| circumstantial matters.
| jncfhnb wrote:
| This post is full of fancy word nonsense.
|
| "Distributions are sampled from distributions" is
| meaningless because you cannot define the meta
| distribution. But more importantly, the Drake equation is
| not a RANDOM SAMPLE from a population of distributions.
| So the idea of sampling distributions is irrelevant even
| if true. The naive math of multiplying them together is
| invalid.
| 3abiton wrote:
| [dead]
| karpierz wrote:
| There's the bonus problem of: even if you magically have
| correct priors, you still need to assume that Drake's
| Equation is a good model for the generation process of
| civilizations. If the equation is missing terms or has
| extra terms, no amount of Bayesian reasoning helps
| correct for that.
|
| It's like thinking that you can use Bayesian reasoning to
| determine the likelihood of Russell's Teapot existing.
| DennisP wrote:
| So your prior is that Bayesian papers are likely to have
| unfounded priors. Now I'm wondering how well-founded your
| prior is.
| narag wrote:
| _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 wrote:
| It's ripe for YouTubers cum science communicators to jump on.
| goatlover wrote:
| "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 wrote:
| >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.
| JumpCrisscross wrote:
| > _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.
| jwocky wrote:
| What was the conclusion of this paper? The link's conclusion
| was truncated.
| _a_a_a_ wrote:
| It's in the abstrct, right at the top
| _zoltan_ wrote:
| You could have just stayed silent.
| _a_a_a_ wrote:
| Why, was there a joke I ruined or something?
| yreg wrote:
| 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_ wrote:
| > 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 wrote:
| 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.
| smif wrote:
| 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!").
___________________________________________________________________
(page generated 2023-07-22 23:01 UTC)