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In this sense, there's a variant of the Great Filter where the Filter isn't the existence of other civilizations, but over the probability mass they'll cross pa

by gfodor 6y ago

In this sense, there's a variant of the Great Filter where the Filter isn't the existence of other civilizations, but over the probability mass they'll cross paths with another and each can mutually grok the other exists. Arguably this is a much more grounded way to view the Filter theory, since it's less assumption-laden. It also surfaces the assumptions of the usual Filter theory more starkly. We only recently even became intelligent enough for the concept of us recognizing another civilization to even make sense.

krapp 6y ago
I think people intuitively perceive the universe as being roughly analogous to Earth's oceans. Obviously we know it isn't objectively true, but subjectively we're just not capable of comprehending the true scale and emptiness of space, of reconciling the Hubble Deep Field image[0] with the fact that less than 5% of the entire universe is physical matter. Even the distance between the Earth and Moon is mind-boggling on human scales, and humans have traveled it. So it seems reasonable that if any interstellar civilization were out there, one would have found us by now, or their presence would be obvious to us. After all, Rome knew of China, even if they never directly interacted, and Spain eventually stumbled across the New World. Von Neumann probes make sense because it doesn't occur to us that the chances of any arbitrary path along the universe intersecting with a star would be effectively zero. We look up at the night sky and we can see so many of them, and they seem so close together, obviously you'd run into one no matter which way you went, sooner or later. Right? It's more comforting to make up rationales as to why we might be alone than deal with the ramifications of being surrounded by life we may never see in a universe in which the entirety of physical reality amounts to a rounding error in a zero. [0]https://en.wikipedia.org/wiki/Hubble_Deep_Field https://en.wikipedia.org/wiki/Hubble_Deep_Field [1]https://www.theatlantic.com/technology/archive/2014/12/the-chance-of-a-collision-in-outer-space-is-practically-zilch/383810/ https://www.theatlantic.com/technology/archive/2014/12/the-c...
- bena 6y ago
  True, the one thing I keep trying to remind myself and other of is that we really don't appreciate the cosmic scale all that well. There's a point where it's all just "big". A million and a billion seem equally big. Even though, as it has been said before, that the difference between 1 billion and 1 million is about 1 billion. There are so many fundamentally difficult problems with deep space exploration, that it may never be logistically possible to over come them. And that's of the ones we know about.
- MiroF 6y ago
  We're not capable of comprehending the true scale/emptiness of space, sure - but it seems like many commentators are having difficulty comprehending the length of time the universe has been around for. If a single civilization in our galaxy made a machine capable of replicating itself and going to other star systems less than a billion years ago, we should have seen that. > it doesn't occur to us that the chances of any arbitrary path along the universe intersecting with a star would be effectively zero I fail to see how this is a strong critique of Von Neumann probes, maybe you can clarify.
  - krapp 6y ago
    >I fail to see how this is a strong critique of Von Neumann probes, maybe you can clarify. Allow me to attempt to clarify. Let's say a civilization creates Von Neumann probes. Ignore whether such devices are even technically feasible. It sends these Von Neumann probes out into the universe in all directions. The chances of any one of them ever encountering anything larger than a grain of dust before the heat death of the universe is practically zero. In almost all possible universes, all of the probes are swallowed up by the void. In almost all of the rest, one probe finds enough material to be able to replicate, and all of those are swallowed up into the void. The scenario whereby a stable chain of exponential reproduction and growth via interstellar transfer occurs lasting long enough for a significant amount of stellar matter to be consumed and for an obvious trace to be left which just happens to be visible to us, is not the most likely scenario in a universe where such devices exist, it is still so unlikely that its feasibility borders on requiring sorcery. Because the universe is just that empty. It's the sort of idea that only works on graph paper assuming a "perfectly spherical cow in a frictionless vacuum" kind of universe. The lack of a universe awash in Von Neumann probes is not a strong argument against the existence of life or advanced civilization in the universe, it is, itself, a strong argument against the feasibility of Von Neumann probes.
    - s1artibartfast 6y ago
      Why are you assuming that such a probe is not targeted? Targeting radically changes the results. An interesting middle ground to explore is untargeted probes taking gravity into account
- TheOtherHobbes 6y ago
  Rome and China were roughly at the same technological level, more or less. Given modern technology, we would be able to observe both without being noticed. It would be pretty trivial from space. It wouldn't be quite so trivial close up, but it would be possible. A time difference of ten thousand years? The invisibility would be rather more effortless, and might even include direct memory manipulation in the victims. A million years? Can anyone even imagine what a million year difference would look like? Never mind the technology - we can't even imagine what its motivations would be. So assuming an advanced civ is going to do what we'd do - build ships, colonise, hoard and transform resources - is more than a little naive and unimaginative. It's not unlike a protohominid assuming that life is about hunting, and any other two legged creature they meet is going to want to talk about flint knapping and these new arrowhead shapes.
  - MiroF 6y ago
    > So assuming an advanced civ is going to do what we'd do - build ships, colonise, hoard and transform resources - is more than a little naive and unimaginative. The assumption is weaker than you suggest. It's not that your typical advanced civ will do what we'd do, just that some proportion (perhaps extremely small) of civilizations will be expansionary.
    - saberdancer 6y ago
      But what is to make them expansionary. Space is so vast and resources plentiful that it is doubtful any run of the mill system would be interesting. After you are sufficiently advanced you probably do not need much resources at all.
      - MiroF 6y ago
        > After you are sufficiently advanced you probably do not need much resources at all. Any process that involves replication will eventually need more resources.
MiroF 6y ago
> Filter isn't the existence of other civilizations, but over the probability mass they'll cross paths with another and each can mutually grok the other exists The idea is that "probability mass they'll cross paths with another and each can mutually grok the other exists" is a monotonically increasing function of the number of other civilizations, which bridges the problem you've identified.

by gfodor 6y ago

krapp 6y ago

I think people intuitively perceive the universe as being roughly analogous to Earth's oceans. Obviously we know it isn't objectively true, but subjectively we're just not capable of comprehending the true scale and emptiness of space, of reconciling the Hubble Deep Field image[0] with the fact that less than 5% of the entire universe is physical matter. Even the distance between the Earth and Moon is mind-boggling on human scales, and humans have traveled it. So it seems reasonable that if any interstellar civilization were out there, one would have found us by now, or their presence would be obvious to us. After all, Rome knew of China, even if they never directly interacted, and Spain eventually stumbled across the New World. Von Neumann probes make sense because it doesn't occur to us that the chances of any arbitrary path along the universe intersecting with a star would be effectively zero. We look up at the night sky and we can see so many of them, and they seem so close together, obviously you'd run into one no matter which way you went, sooner or later. Right? It's more comforting to make up rationales as to why we might be alone than deal with the ramifications of being surrounded by life we may never see in a universe in which the entirety of physical reality amounts to a rounding error in a zero. [0]https://en.wikipedia.org/wiki/Hubble_Deep_Field https://en.wikipedia.org/wiki/Hubble_Deep_Field [1]https://www.theatlantic.com/technology/archive/2014/12/the-chance-of-a-collision-in-outer-space-is-practically-zilch/383810/ https://www.theatlantic.com/technology/archive/2014/12/the-c...

bena 6y ago
True, the one thing I keep trying to remind myself and other of is that we really don't appreciate the cosmic scale all that well. There's a point where it's all just "big". A million and a billion seem equally big. Even though, as it has been said before, that the difference between 1 billion and 1 million is about 1 billion. There are so many fundamentally difficult problems with deep space exploration, that it may never be logistically possible to over come them. And that's of the ones we know about.
MiroF 6y ago
We're not capable of comprehending the true scale/emptiness of space, sure - but it seems like many commentators are having difficulty comprehending the length of time the universe has been around for. If a single civilization in our galaxy made a machine capable of replicating itself and going to other star systems less than a billion years ago, we should have seen that. > it doesn't occur to us that the chances of any arbitrary path along the universe intersecting with a star would be effectively zero I fail to see how this is a strong critique of Von Neumann probes, maybe you can clarify.
- krapp 6y ago
  >I fail to see how this is a strong critique of Von Neumann probes, maybe you can clarify. Allow me to attempt to clarify. Let's say a civilization creates Von Neumann probes. Ignore whether such devices are even technically feasible. It sends these Von Neumann probes out into the universe in all directions. The chances of any one of them ever encountering anything larger than a grain of dust before the heat death of the universe is practically zero. In almost all possible universes, all of the probes are swallowed up by the void. In almost all of the rest, one probe finds enough material to be able to replicate, and all of those are swallowed up into the void. The scenario whereby a stable chain of exponential reproduction and growth via interstellar transfer occurs lasting long enough for a significant amount of stellar matter to be consumed and for an obvious trace to be left which just happens to be visible to us, is not the most likely scenario in a universe where such devices exist, it is still so unlikely that its feasibility borders on requiring sorcery. Because the universe is just that empty. It's the sort of idea that only works on graph paper assuming a "perfectly spherical cow in a frictionless vacuum" kind of universe. The lack of a universe awash in Von Neumann probes is not a strong argument against the existence of life or advanced civilization in the universe, it is, itself, a strong argument against the feasibility of Von Neumann probes.
  - s1artibartfast 6y ago
    Why are you assuming that such a probe is not targeted? Targeting radically changes the results. An interesting middle ground to explore is untargeted probes taking gravity into account
TheOtherHobbes 6y ago
Rome and China were roughly at the same technological level, more or less. Given modern technology, we would be able to observe both without being noticed. It would be pretty trivial from space. It wouldn't be quite so trivial close up, but it would be possible. A time difference of ten thousand years? The invisibility would be rather more effortless, and might even include direct memory manipulation in the victims. A million years? Can anyone even imagine what a million year difference would look like? Never mind the technology - we can't even imagine what its motivations would be. So assuming an advanced civ is going to do what we'd do - build ships, colonise, hoard and transform resources - is more than a little naive and unimaginative. It's not unlike a protohominid assuming that life is about hunting, and any other two legged creature they meet is going to want to talk about flint knapping and these new arrowhead shapes.
- MiroF 6y ago
  > So assuming an advanced civ is going to do what we'd do - build ships, colonise, hoard and transform resources - is more than a little naive and unimaginative. The assumption is weaker than you suggest. It's not that your typical advanced civ will do what we'd do, just that some proportion (perhaps extremely small) of civilizations will be expansionary.
  - saberdancer 6y ago
    But what is to make them expansionary. Space is so vast and resources plentiful that it is doubtful any run of the mill system would be interesting. After you are sufficiently advanced you probably do not need much resources at all.
    - MiroF 6y ago
      > After you are sufficiently advanced you probably do not need much resources at all. Any process that involves replication will eventually need more resources.

MiroF 6y ago

> Filter isn't the existence of other civilizations, but over the probability mass they'll cross paths with another and each can mutually grok the other exists The idea is that "probability mass they'll cross paths with another and each can mutually grok the other exists" is a monotonically increasing function of the number of other civilizations, which bridges the problem you've identified.