6 ms·

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 (

by 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?
      - pixl97 2y ago
        Of course I see this as a conflation of life versus intelligence. Do I suspect we'll see life commuting between galaxies, seems unlikely life as is fragile compared to how damned harsh space is. But intelligence is a completely different story. We send rudimentary intelligences to space and have racked up billions of miles on them. It seems far more likely that any space faring civilization would look like the following. 1. They would ship the instruction to build life when the reach the destination they are heading too. Machines with error correction seem much more resilient would be much more likely to reach a destination if they had enough energy for the trip so they could refurbish themselves over time. 2. Getting rid of the bodies/life part in the first place. Who cares if it's a million years if you can just pause yourself? Of course the fact the entire universe isn't filled with Von Neumann probes (at least that we see) points out that this hasn't happened yet.
        lazide 2y ago
        1) that seems to be a lot harder than it seems. Entropy is a nightmare, and data corruption is a big problem. And having a general purpose system capable not only adapting to all the various situations and challenges likely to be faced, that also would have the reserves to deal with them usefully AND reproduce is something we can only hope for in our dreams right now. And until such a thing exists, it’s only speculation it wouldn’t have similar types of problems, eh? Humans are the most adaptable and intelligent anything we have yet run across, and we still regularly struggle to solve the problems we run across even in our comfy and well known existing biosphere which is right here, and that we’re quite well adapted to. And that is assuming a one way trip. Energetically, what could it hope to return to us that would be worth the cost we’d sink into it to try? Panspermia/species wide genetic reproductive drive, maybe - but then sending a robot doesn’t scratch that itch does it? 2) opportunity cost of time is a thing. Some would argue even that time itself is the most valuable thing we have. Pausing yourself for a million years while your competitors don’t, could be a real problem. Also, think of all the new TV shows you’d miss! Agree on the von neumann probe problem. The lack of them doesn’t lend credence to it actually being straightforward or even possible solution for sure. But hey, maybe all the UFO folks are onto something, warp drives/wormholes exist and are cheap, etc. In which case, disclose it already assholes so we can start doing cool stuff with it!
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.

by kaibee 2y ago

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?
    - pixl97 2y ago
      Of course I see this as a conflation of life versus intelligence. Do I suspect we'll see life commuting between galaxies, seems unlikely life as is fragile compared to how damned harsh space is. But intelligence is a completely different story. We send rudimentary intelligences to space and have racked up billions of miles on them. It seems far more likely that any space faring civilization would look like the following. 1. They would ship the instruction to build life when the reach the destination they are heading too. Machines with error correction seem much more resilient would be much more likely to reach a destination if they had enough energy for the trip so they could refurbish themselves over time. 2. Getting rid of the bodies/life part in the first place. Who cares if it's a million years if you can just pause yourself? Of course the fact the entire universe isn't filled with Von Neumann probes (at least that we see) points out that this hasn't happened yet.
      - lazide 2y ago
        1) that seems to be a lot harder than it seems. Entropy is a nightmare, and data corruption is a big problem. And having a general purpose system capable not only adapting to all the various situations and challenges likely to be faced, that also would have the reserves to deal with them usefully AND reproduce is something we can only hope for in our dreams right now. And until such a thing exists, it’s only speculation it wouldn’t have similar types of problems, eh? Humans are the most adaptable and intelligent anything we have yet run across, and we still regularly struggle to solve the problems we run across even in our comfy and well known existing biosphere which is right here, and that we’re quite well adapted to. And that is assuming a one way trip. Energetically, what could it hope to return to us that would be worth the cost we’d sink into it to try? Panspermia/species wide genetic reproductive drive, maybe - but then sending a robot doesn’t scratch that itch does it? 2) opportunity cost of time is a thing. Some would argue even that time itself is the most valuable thing we have. Pausing yourself for a million years while your competitors don’t, could be a real problem. Also, think of all the new TV shows you’d miss! Agree on the von neumann probe problem. The lack of them doesn’t lend credence to it actually being straightforward or even possible solution for sure. But hey, maybe all the UFO folks are onto something, warp drives/wormholes exist and are cheap, etc. In which case, disclose it already assholes so we can start doing cool stuff with it!

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.