7 ms·

> Life on Titan would be slow and low metabolism compared to us (probably). On the other hand, maybe the chemistry there could be using less stable chemicals w

> Life on Titan would be slow and low metabolism compared to us (probably). On the other hand, maybe the chemistry there could be using less stable chemicals where less energy is needed to change them. It's at a much lower temperature, after all. I suspect we'll find nothing, though, due to Fermi. If two different Origin of Life events happen in the same system, OoL (of at least one of those kinds) must be common in the universe, and that would remove what I consider the big potential obstacle to abundant intelligence in the universe. Just an intuition without more data, of course.

kaibee 2y ago
Its wholly possible for the universe to be teeming with single-celled life, but I think the jump to multicellular, intelligent, civilization, and space-faring (at least signals wise) could still cut it to a factor 1/1000 stars. And we're relatively early in the life of the universe still.
- pfdietz 2y ago
  Cutting it to 1/1000 stars wouldn't be anywhere near enough to get around Fermi, by many orders of magnitude.
- JumpCrisscross 2y ago
  > could still cut it to a factor 1/1000 stars I’m a multicellular rare Earther. We’ve had on the order of 10^40 cells, ever [1]. Symbiogenesis occurred, from what we can tell, once [2]. (For comparison, there are 10^11 stars in the Milky Way [3] and 10^24 in the observable universe [4].) We might be able to argue that factor should be cut, since any late symbiogeneses would be outcompeted into oblivion. But that still, optimistically, puts us in the realm of the Milky Way’s star count. [1] https://www.cell.com/current-biology/abstract/S0960-9822(23)01286-1 https://www.cell.com/current-biology/abstract/S0960-9822(23)... [2] https://en.m.wikipedia.org/wiki/Symbiogenesis https://en.m.wikipedia.org/wiki/Symbiogenesis [3] https://en.m.wikipedia.org/wiki/Milky_Way https://en.m.wikipedia.org/wiki/Milky_Way [4] https://en.m.wikipedia.org/wiki/Observable_universe#Matter_and_mass https://en.m.wikipedia.org/wiki/Observable_universe#Matter_a...
  - api 2y ago
    The basic idea of rare Earth as an answer to Fermi is that if the frequency of advanced life is around 1 per galaxy per billion years or something like that then we'd likely never meet any aliens. Intergalactic travel is borderline impossible barring unknown physics or travel very close to the speed of light. Even at speeds like 0.5c (50% the speed of light) the trip would take so long you'd have problems like cosmic rays tearing you apart over such long spans of time, and in the vastness of intergalactic space there's no place to pitch a tent and chill and repair things. 0.5c would get you to the stars but not the galaxies. Intergalactic flight would require something more like 0.95c to 0.99c. The energy requirements for that are insane and possibly unachievable, and if you hit a dust particle at that speed the yield will be like a thermonuclear bomb. The cosmic microwave background also becomes a beam of hard gamma rays aimed at your head. All kinds of crazy extreme physics things happen. Lastly, why do it? Galaxies are huge and if you're alone then it's all yours. The only conceivable reason would be to flee some galactic-scale super-catastrophe like your galaxy's central black hole behaving badly and frying everything with gamma rays. Even for that it might be easier to burrow deeply into planetary bodies instead. Of course one can imagine ultra-far-future scenarios like: what if Andromeda hosts some galactic-scale super civilization by the time it hits the Milky Way which by then also hosts such a thing. That'd be a hoot.
    - pfdietz 2y ago
      > Intergalactic flight would require something more like 0.95c to 0.99c Why would it require speeds that high? Sure, it's going to take a very long time, but why is that an insurmountable obstacle? There are enough isolated stars in intergalactic space that one can even imagining making the trip in smaller steps, with colonization in between. At a stellar density nine orders of magnitude lower than our galaxy stars are still within thousands of light years of each other.
      - lazide 2y ago
        Because most people go nearly insane in solitary confinement? and that isn’t even really solitary. And gov’ts and social structures rarely last a few generations, let along 100 of them. Not to mention inbreeding. What makes you think any humans stuck in something the size of even the most generously sized starships won’t go full lord-of-the-flies and be unable to effectively maintain the ship long before it ever arrives?
- sqeaky 2y ago
  I agree with your sentiment but not your specific number. The leap from uni- to multi-cellular life might be a "great filter" in Fermi-paradox parlance. But I think it would need to be more like one in a million or one in a billion. I think even one civilization becoming a slow interstellar (less than 0.1C ships for their) civilization could colonize the galaxy in less than a million years. Consider what we could do if we could get a slow ship to Alpha Centauri in some absurd time like 1000 years and actually settle there. Maybe we try ever If us here on Earth and Sol could only do that once every thousand years and then if each colony could too. We would only be doubling the amount of stars we inhabit every thousand years. Presuming this slow pace we would also be adding 5~10 light years to our civilization in that time too. But in a million years that 5k to 10 light years would be a sphere with diameter about 10% to 20% the diameter of the galaxy. Allow those jumps to be 50ly and we could get a whole Milky Way galaxy in that time. That is all predicated on very slow stuff, no FTL, slow ships or project taking massive time. And since the dinosaurs died we had 65 such time periods and another 300 while the dinosaurs lived... And I could go on for hours about this stuff. But my point is that if unicellular life is common and there is a single great filter and that is the jump to multicellular life then the odds of that event dictate how often we would see other civilizations. A 1 in 1000 we would see civilizations all over the place. We would certainly be withing radio range of at least a few. So it would need to be much worse odds.
  - pfdietz 2y ago
    I don't think multicellularity is a plausible Great Filter, since it's easy to achieve in laboratory evolution experiments -- just get cells to stick together after fissioning. https://en.wikipedia.org/wiki/Multicellular_organism#Experimental_evolution https://en.wikipedia.org/wiki/Multicellular_organism#Experim...
  - silver_silver 2y ago
    The assumption that colonisation and endless population growth are inevitable goals of any intelligence is a flaw of the paradox, in my opinion. I see it as something we just haven’t outgrown yet as a species. That colonisation could of course be in the form of probes simply exploring, but there are timescale and resource issues with that which make me question if it would be worthwhile for a civilisation considering the limited energy in any given system and tremendous effort involved in getting to another once it runs out.
mtlmtlmtlmtl 2y ago
I'm highly sceptical of the Fermi paradox being a meaningful paradox at all. I don't think we have nearly enough data to make any conclusion at all about the frequency of intelligent life in our own galaxy, let alone the universe. We've only started finding exoplanets in the last few decades, and the frequency of exoplanet detection was very low for most of that time and is still growing today. The ability to learn much of anything about the environments of these planets is even more recent, just a few years since the launch of JWST, and still very limited. It's still only "reliable" for fairly large planets, mostly gas giants. And even for those planets our ability to model the data is an area of active, painstaking research. The number of planets whose atmospheres we have any data-backed information about is very very low. So it seems like the only real argument for the Fermi paradox(certainly back in the 50s when Fermi proposed it) is that we haven't been visited or received any communication. But even that's worthy of doubt. Indeed, our ability to detect and characterise very small objects in or passing through the solar system is fairly limited even today, and was practically non-existent before. It seems very plausible that alien probes could have visited our solar system many times without us noticing. It could for instance be the case that this is only possible by way of technologies that can't easily decelerate and so they've only passed through. We'd have to be pretty lucky to spot something like that, at the size it would likely be, passing through only for a short time(given the speed it would have to move at). As for radio signals, the amount of funding that goes into projects like SETI is not exactly earth-shattering and also hasn't been going on for very long. It's a pretty fringe area of research. The amount of interference from earth-based radio sources also makes this research quite difficult. I'm not some UFO nut, btw. I'm not arguing for conspiracy theories involving the US government, alien abductions, yadda yadda. I'm just asking what do we really know? Not very much, it seems to me.
- api 2y ago
  Obligatory XKCD: https://xkcd.com/638/ https://xkcd.com/638/ I completely agree. We haven't been looking very long and very hard and we're not even that sure what to look for or where to look. All we can say right now is that we do not see any unambiguous signs of ETI, but space is called space for a reason. We are also searching the vastness of time. I don't completely dismiss ET-origin UFOs. I don't think there's anywhere near enough evidence to make such a claim as anything more than a hypothesis, but remember that one possible answer to the Fermi paradox is that there isn't one.
exochrono 2y ago
obligatory reference to the dark forest hypothesis (https://en.wikipedia.org/wiki/Dark_forest_hypothesis https://en.wikipedia.org/wiki/Dark_forest_hypothesis) as an alternate explanation for the apparent rarity of life

kaibee 2y ago

Its wholly possible for the universe to be teeming with single-celled life, but I think the jump to multicellular, intelligent, civilization, and space-faring (at least signals wise) could still cut it to a factor 1/1000 stars. And we're relatively early in the life of the universe still.

pfdietz 2y ago
Cutting it to 1/1000 stars wouldn't be anywhere near enough to get around Fermi, by many orders of magnitude.
JumpCrisscross 2y ago
> could still cut it to a factor 1/1000 stars I’m a multicellular rare Earther. We’ve had on the order of 10^40 cells, ever [1]. Symbiogenesis occurred, from what we can tell, once [2]. (For comparison, there are 10^11 stars in the Milky Way [3] and 10^24 in the observable universe [4].) We might be able to argue that factor should be cut, since any late symbiogeneses would be outcompeted into oblivion. But that still, optimistically, puts us in the realm of the Milky Way’s star count. [1] https://www.cell.com/current-biology/abstract/S0960-9822(23)01286-1 https://www.cell.com/current-biology/abstract/S0960-9822(23)... [2] https://en.m.wikipedia.org/wiki/Symbiogenesis https://en.m.wikipedia.org/wiki/Symbiogenesis [3] https://en.m.wikipedia.org/wiki/Milky_Way https://en.m.wikipedia.org/wiki/Milky_Way [4] https://en.m.wikipedia.org/wiki/Observable_universe#Matter_and_mass https://en.m.wikipedia.org/wiki/Observable_universe#Matter_a...
- api 2y ago
  The basic idea of rare Earth as an answer to Fermi is that if the frequency of advanced life is around 1 per galaxy per billion years or something like that then we'd likely never meet any aliens. Intergalactic travel is borderline impossible barring unknown physics or travel very close to the speed of light. Even at speeds like 0.5c (50% the speed of light) the trip would take so long you'd have problems like cosmic rays tearing you apart over such long spans of time, and in the vastness of intergalactic space there's no place to pitch a tent and chill and repair things. 0.5c would get you to the stars but not the galaxies. Intergalactic flight would require something more like 0.95c to 0.99c. The energy requirements for that are insane and possibly unachievable, and if you hit a dust particle at that speed the yield will be like a thermonuclear bomb. The cosmic microwave background also becomes a beam of hard gamma rays aimed at your head. All kinds of crazy extreme physics things happen. Lastly, why do it? Galaxies are huge and if you're alone then it's all yours. The only conceivable reason would be to flee some galactic-scale super-catastrophe like your galaxy's central black hole behaving badly and frying everything with gamma rays. Even for that it might be easier to burrow deeply into planetary bodies instead. Of course one can imagine ultra-far-future scenarios like: what if Andromeda hosts some galactic-scale super civilization by the time it hits the Milky Way which by then also hosts such a thing. That'd be a hoot.
  - pfdietz 2y ago
    > Intergalactic flight would require something more like 0.95c to 0.99c Why would it require speeds that high? Sure, it's going to take a very long time, but why is that an insurmountable obstacle? There are enough isolated stars in intergalactic space that one can even imagining making the trip in smaller steps, with colonization in between. At a stellar density nine orders of magnitude lower than our galaxy stars are still within thousands of light years of each other.
    - lazide 2y ago
      Because most people go nearly insane in solitary confinement? and that isn’t even really solitary. And gov’ts and social structures rarely last a few generations, let along 100 of them. Not to mention inbreeding. What makes you think any humans stuck in something the size of even the most generously sized starships won’t go full lord-of-the-flies and be unable to effectively maintain the ship long before it ever arrives?
sqeaky 2y ago
I agree with your sentiment but not your specific number. The leap from uni- to multi-cellular life might be a "great filter" in Fermi-paradox parlance. But I think it would need to be more like one in a million or one in a billion. I think even one civilization becoming a slow interstellar (less than 0.1C ships for their) civilization could colonize the galaxy in less than a million years. Consider what we could do if we could get a slow ship to Alpha Centauri in some absurd time like 1000 years and actually settle there. Maybe we try ever If us here on Earth and Sol could only do that once every thousand years and then if each colony could too. We would only be doubling the amount of stars we inhabit every thousand years. Presuming this slow pace we would also be adding 5~10 light years to our civilization in that time too. But in a million years that 5k to 10 light years would be a sphere with diameter about 10% to 20% the diameter of the galaxy. Allow those jumps to be 50ly and we could get a whole Milky Way galaxy in that time. That is all predicated on very slow stuff, no FTL, slow ships or project taking massive time. And since the dinosaurs died we had 65 such time periods and another 300 while the dinosaurs lived... And I could go on for hours about this stuff. But my point is that if unicellular life is common and there is a single great filter and that is the jump to multicellular life then the odds of that event dictate how often we would see other civilizations. A 1 in 1000 we would see civilizations all over the place. We would certainly be withing radio range of at least a few. So it would need to be much worse odds.
- pfdietz 2y ago
  I don't think multicellularity is a plausible Great Filter, since it's easy to achieve in laboratory evolution experiments -- just get cells to stick together after fissioning. https://en.wikipedia.org/wiki/Multicellular_organism#Experimental_evolution https://en.wikipedia.org/wiki/Multicellular_organism#Experim...
- silver_silver 2y ago
  The assumption that colonisation and endless population growth are inevitable goals of any intelligence is a flaw of the paradox, in my opinion. I see it as something we just haven’t outgrown yet as a species. That colonisation could of course be in the form of probes simply exploring, but there are timescale and resource issues with that which make me question if it would be worthwhile for a civilisation considering the limited energy in any given system and tremendous effort involved in getting to another once it runs out.

mtlmtlmtlmtl 2y ago

I'm highly sceptical of the Fermi paradox being a meaningful paradox at all. I don't think we have nearly enough data to make any conclusion at all about the frequency of intelligent life in our own galaxy, let alone the universe. We've only started finding exoplanets in the last few decades, and the frequency of exoplanet detection was very low for most of that time and is still growing today. The ability to learn much of anything about the environments of these planets is even more recent, just a few years since the launch of JWST, and still very limited. It's still only "reliable" for fairly large planets, mostly gas giants. And even for those planets our ability to model the data is an area of active, painstaking research. The number of planets whose atmospheres we have any data-backed information about is very very low. So it seems like the only real argument for the Fermi paradox(certainly back in the 50s when Fermi proposed it) is that we haven't been visited or received any communication. But even that's worthy of doubt. Indeed, our ability to detect and characterise very small objects in or passing through the solar system is fairly limited even today, and was practically non-existent before. It seems very plausible that alien probes could have visited our solar system many times without us noticing. It could for instance be the case that this is only possible by way of technologies that can't easily decelerate and so they've only passed through. We'd have to be pretty lucky to spot something like that, at the size it would likely be, passing through only for a short time(given the speed it would have to move at). As for radio signals, the amount of funding that goes into projects like SETI is not exactly earth-shattering and also hasn't been going on for very long. It's a pretty fringe area of research. The amount of interference from earth-based radio sources also makes this research quite difficult. I'm not some UFO nut, btw. I'm not arguing for conspiracy theories involving the US government, alien abductions, yadda yadda. I'm just asking what do we really know? Not very much, it seems to me.

api 2y ago
Obligatory XKCD: https://xkcd.com/638/ https://xkcd.com/638/ I completely agree. We haven't been looking very long and very hard and we're not even that sure what to look for or where to look. All we can say right now is that we do not see any unambiguous signs of ETI, but space is called space for a reason. We are also searching the vastness of time. I don't completely dismiss ET-origin UFOs. I don't think there's anywhere near enough evidence to make such a claim as anything more than a hypothesis, but remember that one possible answer to the Fermi paradox is that there isn't one.

exochrono 2y ago

obligatory reference to the dark forest hypothesis (https://en.wikipedia.org/wiki/Dark_forest_hypothesis https://en.wikipedia.org/wiki/Dark_forest_hypothesis) as an alternate explanation for the apparent rarity of life