4 ms·

> If ETs are expected to be found, where are the Bracewell-von Neumann probes? Posing a question like "if [X] was expected, then how come we haven't found [ver

by Udo 10y ago

> If ETs are expected to be found, where are the Bracewell-von Neumann probes? Posing a question like "if [X] was expected, then how come we haven't found [very specific indicator of X]" does not make a lot of sense right now, neither from a logical point of view nor scientifically. First of all, the absence of detectable vN probes does not somehow retroactively change the expectation we had for the presence of alien life, because that expectation arose from a statistical perspective on environmental and biological factors. Until invalidated, this is still the default expectation. It may well turn out that expectation was based on faulty assumptions at some point, but the deciding factor will not be the absence of your favorite arbitrary indicator. It also makes no sense to stop looking based on the argument that we haven't found anything yet. Resolving the Fermi paradox is a higher stakes game than many people realize: Either we're just isolated from discovery for whatever reason (which would be fine as a class of explanations), or there is something fundamentally wrong about the universe. Based on the information we have right now, ET must be out there. If it turns out he definitely isn't, we'd better find out why, because it's one of the biggest areas in modern science where prediction dramatically mismatches observed reality. We can't afford to just call off the search because we haven't found probes.

pklausler 10y ago
Relax, I wasn't suggesting that we stop looking.
- Udo 10y ago
  Not trying to be polemic here, but what then was the point of asking the question that way? I apologize if I read too much into it. I think almost everybody agrees that looking for drones is a worthy endeavor, but it can't be the pivot point of the entire ET discussion for the simple reason that it's one more probability stacked on top of an already unknown probability (= the probability that any civilization will colonize the galaxy with a runaway drone program that can be easily detected). That's a very specific thing. Depending on where you're coming from, you may assign a big probability to it, but there is by far no consensus. So for now the best we can do is to look at as many possible indicators as we can.
  - pklausler 10y ago
    The grandparent of my comment was a suggestion that ETs should be an explanation of last resort for any unexplained phenomenon, which seems highly sensible to me and worthy of support. If you enjoy probabilistic arguments, then you'll appreciate why I think that B-vN probes are inevitable. P(probes) = 1 - P(no probes) = 1 - (1 - P(civ launches one probe))**Nciv If you believe that Nciv is large (and it's the number of tech civilizations up to now, not just at the moment), then you have to argue that P(civ launches one probe) is tiny if you agree that we haven't observed a probe here yet.
    - Udo 10y ago
      > If you enjoy probabilistic arguments, then you'll appreciate why I think that B-vN probes are inevitable. You seem to be under the impression that I wasn't familiar with that argument, even though I explicitly described it as "the probability that any civilization will colonize the galaxy with a runaway drone program that can be easily detected". I don't think there is a person in this thread who doesn't understand the basic assumption. Your claim of inevitability only applies to an infinite amount of time, so in our universe at this point in time the number can still be (and probably is) zero. So I'm trying to talk about a more refined model instead, namely one that tries to at least reserve room for factors such as the overall number of active civilizations, and the likelihood that we actually discover a drone. To start off with, we have no idea what the probability of a single civilization colonizing the galaxy with drones even is, and we're also making a lot of implicit assumptions about the nature of these drones. The argument that "one case is enough" is valid, but still the overall likelihood of that one very specific case may be too low. There is also the possibility of drones going by undetected. We don't know what the drones' navigation algorithm would look like, but it's at least conceivable that some solar systems might have been left out altogether. Finally, I'm not sure if we could necessarily detect moderate drone activity in the outer solar system at all.
    - mrow84 10y ago
      Shouldn't the expression be more like P(probes) = 1 - P(no probes) = 1 - (1 - (P(civ launches one probe)*P(probe reaches Earth)))**Nciv You can then simply argue that P(probe reaches Earth) is small, because you don't believe that Bracewell-von Neumann probes are effective.

by Udo 10y ago

pklausler 10y ago

Relax, I wasn't suggesting that we stop looking.

Udo 10y ago
Not trying to be polemic here, but what then was the point of asking the question that way? I apologize if I read too much into it. I think almost everybody agrees that looking for drones is a worthy endeavor, but it can't be the pivot point of the entire ET discussion for the simple reason that it's one more probability stacked on top of an already unknown probability (= the probability that any civilization will colonize the galaxy with a runaway drone program that can be easily detected). That's a very specific thing. Depending on where you're coming from, you may assign a big probability to it, but there is by far no consensus. So for now the best we can do is to look at as many possible indicators as we can.
- pklausler 10y ago
  The grandparent of my comment was a suggestion that ETs should be an explanation of last resort for any unexplained phenomenon, which seems highly sensible to me and worthy of support. If you enjoy probabilistic arguments, then you'll appreciate why I think that B-vN probes are inevitable. P(probes) = 1 - P(no probes) = 1 - (1 - P(civ launches one probe))**Nciv If you believe that Nciv is large (and it's the number of tech civilizations up to now, not just at the moment), then you have to argue that P(civ launches one probe) is tiny if you agree that we haven't observed a probe here yet.
  - Udo 10y ago
    > If you enjoy probabilistic arguments, then you'll appreciate why I think that B-vN probes are inevitable. You seem to be under the impression that I wasn't familiar with that argument, even though I explicitly described it as "the probability that any civilization will colonize the galaxy with a runaway drone program that can be easily detected". I don't think there is a person in this thread who doesn't understand the basic assumption. Your claim of inevitability only applies to an infinite amount of time, so in our universe at this point in time the number can still be (and probably is) zero. So I'm trying to talk about a more refined model instead, namely one that tries to at least reserve room for factors such as the overall number of active civilizations, and the likelihood that we actually discover a drone. To start off with, we have no idea what the probability of a single civilization colonizing the galaxy with drones even is, and we're also making a lot of implicit assumptions about the nature of these drones. The argument that "one case is enough" is valid, but still the overall likelihood of that one very specific case may be too low. There is also the possibility of drones going by undetected. We don't know what the drones' navigation algorithm would look like, but it's at least conceivable that some solar systems might have been left out altogether. Finally, I'm not sure if we could necessarily detect moderate drone activity in the outer solar system at all.
  - mrow84 10y ago
    Shouldn't the expression be more like P(probes) = 1 - P(no probes) = 1 - (1 - (P(civ launches one probe)*P(probe reaches Earth)))**Nciv You can then simply argue that P(probe reaches Earth) is small, because you don't believe that Bracewell-von Neumann probes are effective.