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Dealing with unknown unknowns is bad for "precise" math. The great filter may be the point where civilizations realize that spreading around the galaxy is not f

Dealing with unknown unknowns is bad for "precise" math. The great filter may be the point where civilizations realize that spreading around the galaxy is not feasible nor necessary, and as we didn't reached that point, we assume that everyone should be spreading around like crazy. Or anything else, that in our current stage and culture we couldn't consider as a possibility. Assuming things based in our lack of knowledge, and deducing that there are no keys because we can't find yet any under this narrow streetlight are my biggest concerns on the paradox. Why "insufficient data for meaningful answer" is not an option? And this paper takes the paradox hypothesis as granted and just tune for the worse some variables.

nerdponx 9y ago
The point of this presentation is to attempt to make those unknowns more precise using Bayesian probability modeling.
mikeash 9y ago
Where does anyone deduce that there are no keys? The point of the Fermi Paradox is simple: according to our best knowledge, the sky should be full of alien civilization. It's not. Therefore, something we know is wrong. The point of the linked document is likewise simple: if you properly account for the unknowns in our knowledge, it's actually consistent with a lack of alien civilizations in the sky. There's nothing wrong with declaring "insufficient data" and moving on. But there's also nothing wrong with analyzing the data that's available and coming up with the best answer you can.
- TheOtherHobbes 9y ago
  It doesn't account for the unknowns in our knowledge. All it does is replace best guess single value estimates with probability distributions - which is a useful exercise, but is still statistical hand-waving. The last four terms in the Drake equation are completely unknown. There's no point even trying to estimate them, because we simply have no clue how to estimate realistic distributions. We don't even have good data yet on the frequency of earth-like planets throughout the galaxy, because our planet-hunting techniques aren't sensitive enough to provide useful accuracy. We have some idea how many rocky planets exist in habitable zones, but there's no way to get from there to an accurate estimate of truly habitable planets. The third term is only slightly more amenable to estimation. What does "life" mean? Clearly for Drake it means life that can send signals we might pick up after a scientific search. But it life sends something so completely unexpected that we're not only not looking for it, but likely to overlook it, then we won't see it - for many possible reasons. What's the distribution? No one knows. So in fact, there are no useful priors for most of the equation. As the over-used phrase says, absence of evidence is not evidence of absence. It's evidence of absence of evidence, and it's unwise to be too dogmatic about drawing further conclusions.
  - ghaff 9y ago
    The Drake equation ends up mixing some terms we think we know fairly well and are either large or suggest something is not that uncommon with terms that are, as you say, completely unknown. Then throw in that, based on human experiences and intuition, one in a trillion or whatever is an incredibly rare event. But that isn't a fair estimation for an event that may be truly rare.
- Chathamization 9y ago
  > The point of the Fermi Paradox is simple: according to our best knowledge, the sky should be full of alien civilization. It's not. But this statement isn't true. We've looked at a tiny fraction of the galaxy for radio signals and didn't find any in that small area that looked like they came from an intelligent origin (actually, we found one, the Wow! signal). But from what I've read - using the equivalent of the Arecibo dish, even the closest star to earth wouldn't be able to pick up our general transmissions. So first we have to assume that civilizations use radio transmissions for a very, very long period of time, and don't replace it with some other tech (so the earth wasn't only receiving them from, say 200,000 BC to 150,000 BC or 1200 BC - 200 AD before the civilization moved on to gamma burst communication). Then we need to assume that these signals are much stronger than the ones we're currently emitting. And then hope we get lucky and look in the right spot for them. So after a small amount of searching we haven't yet been able to find one specific type of civilization using one specific type of technology in a very particular way (not even in the way we use it). Even if the universe is teaming with life, there's nothing paradoxical about that.
  - aaroninsf 9y ago
    This. I have never found the 'paradox' convincing for exactly this reason. The presumptive extrapolation in its formalization is breathtaking. It is primarily useful IMO for posing an estimate to answer a different question from the one people believe it does, which is simply, 'what is the incidence of life, much as we know it...?' ...where 'as we know it' is extremely narrow and rests upon the equally narrow 'physics as we know it.' We are smart monkeys, but while we have learned a breathtaking amount in the last couple centuries, our overconfidence in what we think we know remains constant. You can hold most of the assumptions constant and still come up with many reasons for the 'silence' of the skies, none of which reflect upon the incidence of intelligent life or advanced civilization... :P
  - ralfd 9y ago
    It is not radio alone. We also didn't find any alien megastructures dimming stars. Though Tabby's star is strange. http://www.popularmechanics.com/space/deep-space/a26575/something-weird-is-happening-to-the-alien-megastructure-star/ http://www.popularmechanics.com/space/deep-space/a26575/some... Subreddit devoted to the star: https://www.reddit.com/r/KIC8462852/ https://www.reddit.com/r/KIC8462852/
Robotbeat 9y ago
>...The great filter may be the point where civilizations realize that spreading around the galaxy is not feasible nor necessary... Relevant xkcd, especially the alt-text: "The universe is probably littered with the one-planet graves of cultures which made the sensible economic decision that there's no good reason to go into space--each discovered, studied, and remembered by the ones who made the irrational decision." https://m.xkcd.com/893/ https://m.xkcd.com/893/

nerdponx 9y ago

The point of this presentation is to attempt to make those unknowns more precise using Bayesian probability modeling.

mikeash 9y ago

Where does anyone deduce that there are no keys? The point of the Fermi Paradox is simple: according to our best knowledge, the sky should be full of alien civilization. It's not. Therefore, something we know is wrong. The point of the linked document is likewise simple: if you properly account for the unknowns in our knowledge, it's actually consistent with a lack of alien civilizations in the sky. There's nothing wrong with declaring "insufficient data" and moving on. But there's also nothing wrong with analyzing the data that's available and coming up with the best answer you can.

TheOtherHobbes 9y ago
It doesn't account for the unknowns in our knowledge. All it does is replace best guess single value estimates with probability distributions - which is a useful exercise, but is still statistical hand-waving. The last four terms in the Drake equation are completely unknown. There's no point even trying to estimate them, because we simply have no clue how to estimate realistic distributions. We don't even have good data yet on the frequency of earth-like planets throughout the galaxy, because our planet-hunting techniques aren't sensitive enough to provide useful accuracy. We have some idea how many rocky planets exist in habitable zones, but there's no way to get from there to an accurate estimate of truly habitable planets. The third term is only slightly more amenable to estimation. What does "life" mean? Clearly for Drake it means life that can send signals we might pick up after a scientific search. But it life sends something so completely unexpected that we're not only not looking for it, but likely to overlook it, then we won't see it - for many possible reasons. What's the distribution? No one knows. So in fact, there are no useful priors for most of the equation. As the over-used phrase says, absence of evidence is not evidence of absence. It's evidence of absence of evidence, and it's unwise to be too dogmatic about drawing further conclusions.
- ghaff 9y ago
  The Drake equation ends up mixing some terms we think we know fairly well and are either large or suggest something is not that uncommon with terms that are, as you say, completely unknown. Then throw in that, based on human experiences and intuition, one in a trillion or whatever is an incredibly rare event. But that isn't a fair estimation for an event that may be truly rare.
Chathamization 9y ago
> The point of the Fermi Paradox is simple: according to our best knowledge, the sky should be full of alien civilization. It's not. But this statement isn't true. We've looked at a tiny fraction of the galaxy for radio signals and didn't find any in that small area that looked like they came from an intelligent origin (actually, we found one, the Wow! signal). But from what I've read - using the equivalent of the Arecibo dish, even the closest star to earth wouldn't be able to pick up our general transmissions. So first we have to assume that civilizations use radio transmissions for a very, very long period of time, and don't replace it with some other tech (so the earth wasn't only receiving them from, say 200,000 BC to 150,000 BC or 1200 BC - 200 AD before the civilization moved on to gamma burst communication). Then we need to assume that these signals are much stronger than the ones we're currently emitting. And then hope we get lucky and look in the right spot for them. So after a small amount of searching we haven't yet been able to find one specific type of civilization using one specific type of technology in a very particular way (not even in the way we use it). Even if the universe is teaming with life, there's nothing paradoxical about that.
- aaroninsf 9y ago
  This. I have never found the 'paradox' convincing for exactly this reason. The presumptive extrapolation in its formalization is breathtaking. It is primarily useful IMO for posing an estimate to answer a different question from the one people believe it does, which is simply, 'what is the incidence of life, much as we know it...?' ...where 'as we know it' is extremely narrow and rests upon the equally narrow 'physics as we know it.' We are smart monkeys, but while we have learned a breathtaking amount in the last couple centuries, our overconfidence in what we think we know remains constant. You can hold most of the assumptions constant and still come up with many reasons for the 'silence' of the skies, none of which reflect upon the incidence of intelligent life or advanced civilization... :P
- ralfd 9y ago
  It is not radio alone. We also didn't find any alien megastructures dimming stars. Though Tabby's star is strange. http://www.popularmechanics.com/space/deep-space/a26575/something-weird-is-happening-to-the-alien-megastructure-star/ http://www.popularmechanics.com/space/deep-space/a26575/some... Subreddit devoted to the star: https://www.reddit.com/r/KIC8462852/ https://www.reddit.com/r/KIC8462852/

Robotbeat 9y ago

>...The great filter may be the point where civilizations realize that spreading around the galaxy is not feasible nor necessary... Relevant xkcd, especially the alt-text: "The universe is probably littered with the one-planet graves of cultures which made the sensible economic decision that there's no good reason to go into space--each discovered, studied, and remembered by the ones who made the irrational decision." https://m.xkcd.com/893/ https://m.xkcd.com/893/