3 ms·

Something like a fleet of von Neumann probes could expand across the entirety of the galaxy in a million years or so, and wouldn't care if the original civiliza

Something like a fleet of von Neumann probes could expand across the entirety of the galaxy in a million years or so, and wouldn't care if the original civilization had long since flamed out. Which is long time by our standards, but not too long on the cosmological scale. In theory there should have been lots of habitable places where life could have arisen in our galaxy long enough in the past that the whole place could be "colonized" in this manner. Of course, there could be plenty of these floating around our solar system and we wouldn't know. They could be quite small and the solar system is quite big, and most of the proposed use cases for a civilization wanting to do this would not require it be in constant contact, so they might not even be broadcasting on anything resembling a frequent basis. But in general there are a lot of theoretical technosignatures that we think we should be able to see if there was technological advanced life in the galaxy. (Should be able to see in that it is possible with our current technology - not that we would conclusively have seen it by this point.)

lazide 3y ago
It’s a nice idea in theory, but we’ve seen no evidence Von Neumann probes are even possible, or that any civilization would consider them worth investing in. If you do the math, unless there are the aforementioned ‘cheat codes’, they frankly just don’t pencil out as worthwhile. No FTL/subspace? No ‘infinite cheap energy’ hack? No ‘infinite self replicating yet controllable builder of anything’ molecule? No way to propagate, no way to energize, and no way to communicate at any real scale over the distances involved. Even gigawatt power, high efficiency, high precision aimed lasers aren’t going to have much luck at light year distances, and nothing is going to be useful for two way communication. It’s easy to speculate of course, but like ‘grey goo’ it runs up against real issues with thermodynamics and physics if we stop and think about it much. Worth investigating options of course, or talking about, but if physics is what it seems to be so far, that would perfectly explain the lack of us seeing them - they’re not useful/practical/worth the expense for anyone.
- cthalupa 3y ago
  Worthwhile to invest in I think is the bigger question - from a practical 'can we build a self replicating probe fleet that would eventually cover the galaxy', there's at least evidence that it's possible in the next hundred years or so. http://www.rfreitas.com/Astro/ComparisonReproNov1980.htm http://www.rfreitas.com/Astro/ComparisonReproNov1980.htm https://arxiv.org/ftp/arxiv/papers/2005/2005.12303.pdf https://arxiv.org/ftp/arxiv/papers/2005/2005.12303.pdf In general I do think it makes sense to not just contemplate interstellar visitors as living things making the trek or biological civilizations expanding, but there's a wide variety of artificial ~things~ that could end up in our solar system for whatever reason.
  - lazide 3y ago
    Uh, that isn't evidence? That's speculation on potential future technical advances. The only things we see self replicate are currently biological systems, and they can only do it under very specific circumstances and usually with a LOT of external help. Circumstances which do not exist in space, let alone under the variety of environments on just the handful of planets we see in our solar system - except one, of course. It's a very hard problem, and it isn't clear there is an actual answer that is economic to stick on the end of a rocket, even just to get to the moon. Something that survives 10k+ year journeys to unknown environments, and then does something useful? Even less clear. Gets there AND then has the level of success necessary to transmit any sort of signal, or propagate itself further? Even less so. Why we would do it, is also unclear. Hopefully we'll figure out something that makes it less fantastical at some point - all the things that make it realistic would also help us in many other ways too!
    - cthalupa 3y ago
      We've got a pretty good track record in predicting near-ish-future scientific/technological advances, which is what we would need for self replicating machines. To be clear, I'm not talking nanobots or similar - much more macro sized stuff. All the constituent pieces to make a self replicating mining robot or whatever are there today, and we already automate a lot of the processes required. There are some important gaps to fill, for sure, but none that we have any real reason to believe are insurmountable. We're in agreement that the 'why' is less clear, at least for probes exploring the galaxy. But there are some very clear reasons why this sort of tech in general is useful - mining the asteroid belt, building reflectors to better harness the energy of the sun, building all sorts of other infrastructure in space without having to use a rocket to get it there. At that point once we have the tech and are doing it - and I would be shocked if the human race is still around in 500 years and NOT doing that sort of thing - it's relatively cheap to kick off a bunch of probes doing similar things. I'm still not sure if it's worth it in that scenario, but it's conceivable that it could be. And that puts us again on the question of why we don't see it. We think there should be a lot of intelligent life out there. There's a lot of very important 'if's in all of this, but if we can think of it and and conceive of some potential reasons, and if other intelligent life has these capabilities that we believe will be possible, and if it becomes as resource/energy/time efficient to do as it should be, then it seems like someone, somewhere, should have been able to convince their government or corporation or whatever to do it, even if the results aren't necessarily going to be super apparent. The Pioneer plaque is obviously much cheaper, but we knew beforehand that the utility there is basically 0%. Like I said, I'm not necessarily arguing that these probes are out there. I'm guessing the answer is more likely "There's no compelling reason to colonize or even explore large swathes of the galaxy" and concerns around interstellar travel are on such large timescales that civilizations capable of interstellar travel would only care about their nearest neighbors. Maybe that changes as star formation spins down and the galaxy starts to slowly go dark and your local galactic resources are less and less abundant. I'm just saying that there are technosignatures that would indicate the presence of other intelligent life in the galaxy that have nothing to do with biological beings visiting us, and we would expect that some of these are possible for us to see now, if they're out there.

lazide 3y ago

It’s a nice idea in theory, but we’ve seen no evidence Von Neumann probes are even possible, or that any civilization would consider them worth investing in. If you do the math, unless there are the aforementioned ‘cheat codes’, they frankly just don’t pencil out as worthwhile. No FTL/subspace? No ‘infinite cheap energy’ hack? No ‘infinite self replicating yet controllable builder of anything’ molecule? No way to propagate, no way to energize, and no way to communicate at any real scale over the distances involved. Even gigawatt power, high efficiency, high precision aimed lasers aren’t going to have much luck at light year distances, and nothing is going to be useful for two way communication. It’s easy to speculate of course, but like ‘grey goo’ it runs up against real issues with thermodynamics and physics if we stop and think about it much. Worth investigating options of course, or talking about, but if physics is what it seems to be so far, that would perfectly explain the lack of us seeing them - they’re not useful/practical/worth the expense for anyone.

cthalupa 3y ago
Worthwhile to invest in I think is the bigger question - from a practical 'can we build a self replicating probe fleet that would eventually cover the galaxy', there's at least evidence that it's possible in the next hundred years or so. http://www.rfreitas.com/Astro/ComparisonReproNov1980.htm http://www.rfreitas.com/Astro/ComparisonReproNov1980.htm https://arxiv.org/ftp/arxiv/papers/2005/2005.12303.pdf https://arxiv.org/ftp/arxiv/papers/2005/2005.12303.pdf In general I do think it makes sense to not just contemplate interstellar visitors as living things making the trek or biological civilizations expanding, but there's a wide variety of artificial ~things~ that could end up in our solar system for whatever reason.
- lazide 3y ago
  Uh, that isn't evidence? That's speculation on potential future technical advances. The only things we see self replicate are currently biological systems, and they can only do it under very specific circumstances and usually with a LOT of external help. Circumstances which do not exist in space, let alone under the variety of environments on just the handful of planets we see in our solar system - except one, of course. It's a very hard problem, and it isn't clear there is an actual answer that is economic to stick on the end of a rocket, even just to get to the moon. Something that survives 10k+ year journeys to unknown environments, and then does something useful? Even less clear. Gets there AND then has the level of success necessary to transmit any sort of signal, or propagate itself further? Even less so. Why we would do it, is also unclear. Hopefully we'll figure out something that makes it less fantastical at some point - all the things that make it realistic would also help us in many other ways too!
  - cthalupa 3y ago
    We've got a pretty good track record in predicting near-ish-future scientific/technological advances, which is what we would need for self replicating machines. To be clear, I'm not talking nanobots or similar - much more macro sized stuff. All the constituent pieces to make a self replicating mining robot or whatever are there today, and we already automate a lot of the processes required. There are some important gaps to fill, for sure, but none that we have any real reason to believe are insurmountable. We're in agreement that the 'why' is less clear, at least for probes exploring the galaxy. But there are some very clear reasons why this sort of tech in general is useful - mining the asteroid belt, building reflectors to better harness the energy of the sun, building all sorts of other infrastructure in space without having to use a rocket to get it there. At that point once we have the tech and are doing it - and I would be shocked if the human race is still around in 500 years and NOT doing that sort of thing - it's relatively cheap to kick off a bunch of probes doing similar things. I'm still not sure if it's worth it in that scenario, but it's conceivable that it could be. And that puts us again on the question of why we don't see it. We think there should be a lot of intelligent life out there. There's a lot of very important 'if's in all of this, but if we can think of it and and conceive of some potential reasons, and if other intelligent life has these capabilities that we believe will be possible, and if it becomes as resource/energy/time efficient to do as it should be, then it seems like someone, somewhere, should have been able to convince their government or corporation or whatever to do it, even if the results aren't necessarily going to be super apparent. The Pioneer plaque is obviously much cheaper, but we knew beforehand that the utility there is basically 0%. Like I said, I'm not necessarily arguing that these probes are out there. I'm guessing the answer is more likely "There's no compelling reason to colonize or even explore large swathes of the galaxy" and concerns around interstellar travel are on such large timescales that civilizations capable of interstellar travel would only care about their nearest neighbors. Maybe that changes as star formation spins down and the galaxy starts to slowly go dark and your local galactic resources are less and less abundant. I'm just saying that there are technosignatures that would indicate the presence of other intelligent life in the galaxy that have nothing to do with biological beings visiting us, and we would expect that some of these are possible for us to see now, if they're out there.