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In a universe that is very old and very large, anything that can occur will eventually happen somewhere. This includes the launching of interstellar self-repli

In a universe that is very old and very large, anything that can occur will eventually happen somewhere. This includes the launching of interstellar self-replicating von Neumann probes. All it takes is one civilization somewhere lobbing one sufficiently automated sublight probe, and in a few million years the galaxy is full of them for the rest of time. Either the galaxy is full of interstellar self-replicating probes, or empty of them. Their absence here is strong evidence that nobody, at least in our galaxy, has evolved a technical civilization, and that we are the first or only to approach that level.

TrevorJ 11y ago
I see what you are getting at, but in an infinitely large universe, those events may be infinitely distant from us.
- pklausler 11y ago
  In which case they might as well not exist, from our perspective. In our Local Group of galaxies, however, we can confidently conclude that nobody has ever launched self-replicating interstellar probes. Which means nobody has ever evolved a technical civilization slightly more capable than our own. Radio signals are ephemeral; probes are forever.
  - TrevorJ 11y ago
    Not necessarily, perhaps they choose not to use such technology, due to the obviously dangerous nature of it. Or maybe they will, at some point in the future, but haven't yet.
  - krapp 11y ago
    This assumes that all technical civilizations more capable than ours must launch self-replicating interstellar probes, and that said probes must be robust and perfectly efficient, because their mere existence guarantees the conversion of the galaxy into computronium. Perhaps the lack of probes means there is a fundamental flaw to the concept when applied to the actual, physical universe. Or that technologically advanced civilizations exist which aren't interested in sending self-replicating probes into interstellar space.
    - pklausler 11y ago
      No, it's nearly the opposite assumption: that it's not possible for advanced technical civilizations to prevent, forever, the launch of such a probe.
      - krapp 11y ago
        We don't even know that such probes are technologically feasible. The closest examples we have in the real world are forms of life which are incredibly power-hungry, fragile and prone to mutation. The more complex life is, it appears, the more fragile it becomes, so I would assume this would apply to probes as well, since they would essentially be life. It's entirely possible that, even if such probes exist, they inevitably fail due to entropy, inefficiency or lack of a stable source of fuel/replication mass over a few generations. Not every civilization capable of trying may retain such technological capability forever, either. Even if attempting the trick is relatively rare in the life cycle of civilizations, those that can may not care to do so within the window of their capabilities. You could just as well argue that it's not possible for a civilization exactly as advanced as our own to prevent the launch of a deadly bioweapon which leads to their extinction. You could argue any number of logically sound things which may simply not shake out due to chance in the real universe. Maybe only a few such civilizations have actually arisen, and by pure chance, none of them have done it.
        pklausler 11y ago
        Come on, it's not that much of a stretch from where we are today. We're basically talking about a 3-D printer capable of printing itself, solar panels, an ion engine, and whatever it takes to grind up asteroid surfaces to gather raw materials for the printer. In another comment, I described the odds of these probes arising as P(probes) = 1 - (1 - P(a civ can launch a probe)) ^ N(civ) and unless P(can launch) is zero, not just really small, I think that we can conclude that N(civ) is not a very large number.
        krapp 11y ago
        >We're basically talking about a 3-D printer capable of printing itself, solar panels, an ion engine, and whatever it takes to grind up asteroid surfaces to gather raw materials for the printer. ...and continuing to do so reliably for millions of years, somehow being able to efficiently fabricate arbitrary components of exceeding strength and complexity out of dust and ice, without any appreciable loss in quality of hardware or software, even in the radioactive environment of interstellar space. Just because a model is mathematically consistent doesn't mean it's practically feasible.
  - pc86 11y ago
    I take issue with the premise that a fleet of perfect self-replicating von Neumann probes is "slightly" beyond our current level of technical aptitude.
    - pklausler 11y ago
      Well, they don't have to be perfect replicators (and might actually spread more effectively given some variation on which selection may operate).
  - blacksmith_tb 11y ago
    Why can we be so confident? I assume the probes would use the most minimal amount of mass possible (and still propel themselves and replicate). Our instruments are capable of tracking fair-sized asteroids in our solar system, but not tiny objects (which could have been designed to be difficult to detect). Though it's possible that the extent of their 'probing' would just be to announce their arrival in the widest swath of EMF possible.
  - bradneuberg 11y ago
    Unless we ourselves are composed of self replicating probes. It's still a bit of a mystery how quickly life appeared on Earth itself. Perhaps Earth was seeded via panspermia, and the cells themselves are remnants of self replicating probes?
iamcurious 11y ago
I'm taking a moment to be thankful that today no army of self-replicating probes annihilated life on earth. On the other hand, we are surrounded by earthly self replicating probes and we seem to be doing fine.
Chathamization 11y ago
Not sure why you wouldn't just manufacture a bunch of probes in one system and then send them out en masse. You wouldn't need to worry about creating self-replication units, you'd get to each system more quickly (you wouldn't have to deal with multiple accelerations/decelerations or manufacturing time), you'd have more control (wouldn't have to worry about drone swarms and could inspect each probe before it's sent to its destination), you'd probably have quicker manufacturing (since it'd be done by specialist machines rather than hybrid manufacturer/probes), could probably give the probes a boost form the home system when you send them out, etc. Self replication doesn't seem to add much, but certainly takes away a lot. This is also assuming that aliens will want to scout out the universe, and that probes are the best way for an advanced civilization to do so. We might be like someone from the past who comes to the present and determines that we don't have any long distance communication because they don't see any smoke signals.
- pklausler 11y ago
  You missed the point. I'm not arguing that civilizations would be likely to launch self-replicating probes. What I am asserting is that the probes will be out there UNLESS every single actor capable of launching a self-replicating probe chooses to not do so, and that over billions of years and hundreds of billions of stellar systems in the Local Group, that probability is vanishingly small. All it takes is one launch; if it's possible, it'll happen. And it hasn't. So either there's never been a civilization that launched a self-replicating probe, or it's not possible, or we're the first or only civilization to approach that level.
  - Chathamization 11y ago
    I don't know about that. Even if we're talking about a large sample size, can we really say "that probability is vanishingly small"? It's kind of like saying, "Sure, I don't see any reason why someone would build an underwater city, but with a couple hundred countries in the world, and 7 billion people, the probability that no one is going to do that is tiny." But are we even dealing with a large sample size? Maybe there's "only" been several dozen large interstellar civilizations out there, and a few hundred small ones that never really got far beyond a handful of planets. Or maybe there were a couple of attempts, but they failed horribly. The problem with the "paradox" is that there seems to be a huge number of possible answers. It ends up being "how come this one scenario I'm thinking about hasn't happened."
Jeema101 11y ago
The von Neumann probe is an interesting thought experiment, but practically speaking, what reason would there be for anyone to ever create one (assuming it would ever be possible)?
- pklausler 11y ago
  Insanity, religion, and accident are all possible causes. The act need not be rational nor intentional, it just has to not be impossible.

TrevorJ 11y ago

I see what you are getting at, but in an infinitely large universe, those events may be infinitely distant from us.

pklausler 11y ago
In which case they might as well not exist, from our perspective. In our Local Group of galaxies, however, we can confidently conclude that nobody has ever launched self-replicating interstellar probes. Which means nobody has ever evolved a technical civilization slightly more capable than our own. Radio signals are ephemeral; probes are forever.
- TrevorJ 11y ago
  Not necessarily, perhaps they choose not to use such technology, due to the obviously dangerous nature of it. Or maybe they will, at some point in the future, but haven't yet.
- krapp 11y ago
  This assumes that all technical civilizations more capable than ours must launch self-replicating interstellar probes, and that said probes must be robust and perfectly efficient, because their mere existence guarantees the conversion of the galaxy into computronium. Perhaps the lack of probes means there is a fundamental flaw to the concept when applied to the actual, physical universe. Or that technologically advanced civilizations exist which aren't interested in sending self-replicating probes into interstellar space.
  - pklausler 11y ago
    No, it's nearly the opposite assumption: that it's not possible for advanced technical civilizations to prevent, forever, the launch of such a probe.
    - krapp 11y ago
      We don't even know that such probes are technologically feasible. The closest examples we have in the real world are forms of life which are incredibly power-hungry, fragile and prone to mutation. The more complex life is, it appears, the more fragile it becomes, so I would assume this would apply to probes as well, since they would essentially be life. It's entirely possible that, even if such probes exist, they inevitably fail due to entropy, inefficiency or lack of a stable source of fuel/replication mass over a few generations. Not every civilization capable of trying may retain such technological capability forever, either. Even if attempting the trick is relatively rare in the life cycle of civilizations, those that can may not care to do so within the window of their capabilities. You could just as well argue that it's not possible for a civilization exactly as advanced as our own to prevent the launch of a deadly bioweapon which leads to their extinction. You could argue any number of logically sound things which may simply not shake out due to chance in the real universe. Maybe only a few such civilizations have actually arisen, and by pure chance, none of them have done it.
      - pklausler 11y ago
        Come on, it's not that much of a stretch from where we are today. We're basically talking about a 3-D printer capable of printing itself, solar panels, an ion engine, and whatever it takes to grind up asteroid surfaces to gather raw materials for the printer. In another comment, I described the odds of these probes arising as P(probes) = 1 - (1 - P(a civ can launch a probe)) ^ N(civ) and unless P(can launch) is zero, not just really small, I think that we can conclude that N(civ) is not a very large number.
        krapp 11y ago
        >We're basically talking about a 3-D printer capable of printing itself, solar panels, an ion engine, and whatever it takes to grind up asteroid surfaces to gather raw materials for the printer. ...and continuing to do so reliably for millions of years, somehow being able to efficiently fabricate arbitrary components of exceeding strength and complexity out of dust and ice, without any appreciable loss in quality of hardware or software, even in the radioactive environment of interstellar space. Just because a model is mathematically consistent doesn't mean it's practically feasible.
- pc86 11y ago
  I take issue with the premise that a fleet of perfect self-replicating von Neumann probes is "slightly" beyond our current level of technical aptitude.
  - pklausler 11y ago
    Well, they don't have to be perfect replicators (and might actually spread more effectively given some variation on which selection may operate).
- blacksmith_tb 11y ago
  Why can we be so confident? I assume the probes would use the most minimal amount of mass possible (and still propel themselves and replicate). Our instruments are capable of tracking fair-sized asteroids in our solar system, but not tiny objects (which could have been designed to be difficult to detect). Though it's possible that the extent of their 'probing' would just be to announce their arrival in the widest swath of EMF possible.
- bradneuberg 11y ago
  Unless we ourselves are composed of self replicating probes. It's still a bit of a mystery how quickly life appeared on Earth itself. Perhaps Earth was seeded via panspermia, and the cells themselves are remnants of self replicating probes?

iamcurious 11y ago

I'm taking a moment to be thankful that today no army of self-replicating probes annihilated life on earth. On the other hand, we are surrounded by earthly self replicating probes and we seem to be doing fine.

Chathamization 11y ago

Not sure why you wouldn't just manufacture a bunch of probes in one system and then send them out en masse. You wouldn't need to worry about creating self-replication units, you'd get to each system more quickly (you wouldn't have to deal with multiple accelerations/decelerations or manufacturing time), you'd have more control (wouldn't have to worry about drone swarms and could inspect each probe before it's sent to its destination), you'd probably have quicker manufacturing (since it'd be done by specialist machines rather than hybrid manufacturer/probes), could probably give the probes a boost form the home system when you send them out, etc. Self replication doesn't seem to add much, but certainly takes away a lot. This is also assuming that aliens will want to scout out the universe, and that probes are the best way for an advanced civilization to do so. We might be like someone from the past who comes to the present and determines that we don't have any long distance communication because they don't see any smoke signals.

pklausler 11y ago
You missed the point. I'm not arguing that civilizations would be likely to launch self-replicating probes. What I am asserting is that the probes will be out there UNLESS every single actor capable of launching a self-replicating probe chooses to not do so, and that over billions of years and hundreds of billions of stellar systems in the Local Group, that probability is vanishingly small. All it takes is one launch; if it's possible, it'll happen. And it hasn't. So either there's never been a civilization that launched a self-replicating probe, or it's not possible, or we're the first or only civilization to approach that level.
- Chathamization 11y ago
  I don't know about that. Even if we're talking about a large sample size, can we really say "that probability is vanishingly small"? It's kind of like saying, "Sure, I don't see any reason why someone would build an underwater city, but with a couple hundred countries in the world, and 7 billion people, the probability that no one is going to do that is tiny." But are we even dealing with a large sample size? Maybe there's "only" been several dozen large interstellar civilizations out there, and a few hundred small ones that never really got far beyond a handful of planets. Or maybe there were a couple of attempts, but they failed horribly. The problem with the "paradox" is that there seems to be a huge number of possible answers. It ends up being "how come this one scenario I'm thinking about hasn't happened."

Jeema101 11y ago

The von Neumann probe is an interesting thought experiment, but practically speaking, what reason would there be for anyone to ever create one (assuming it would ever be possible)?

pklausler 11y ago
Insanity, religion, and accident are all possible causes. The act need not be rational nor intentional, it just has to not be impossible.