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gwern comments on 2013 Survey Results - Less Wrong
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There are (very probably around) 1.7x10^11 galaxies in the observable universe. So I don't understand how can P(Aliens in Milky Way) be so closed to P(Aliens in observable universe)? If P(Aliens in an average galaxy) = 0.0000000001, P(Aliens in observable universe) should be around 1-(1-0.0000000001)^(1.7x10^11)=0.9999999586. I know there are other factors that influence these numbers, but still, even if there's a only a very slight chance for P(Aliens in Milky Way), then P(Aliens in observable universe) should be almost certain. There are possible rational justifications for the results of this survey, but I think (0.95) most people were victim of a cognitive bias. Scope insensitivity maybe? because 1.7*10^11 galaxies is too big to imagine. What do you think?
I wonder how many people cooperated only (or in part) because they knew the results would be correlated with their (political) views, and they wanted their "tribe"/community/group/etc. to look good. Maybe next year we could say that this result won't be compared to the other? So if less people cooperate, then it will indicate that maybe some people cooperate for their 'group' to look good. But if these people know that I/we want to compare the results we this year in order to verify this hypothesis, they will continue to cooperate. To avoid most of these, we should compare only the people that will have filled the survey for the first time next year. What do you think?
I think you shouldn't have corrected anything. When I assign a probability to the correctness of my answer, I included a percentage for having misread the question or made a data entry error.
Would some people be interested in answering 10 such questions and give their confidence about their answer every month? That would provide better statistics and a way to see if we're improving.
Perhaps this is explainable with reference to why the Great Silence / Fermi paradox is so compelling? That even with very low rates of expansion, the universe should be colonized by now if an advanced alien civilization had arisen at any point in the past billion years or so. Hence, if there's aliens anywhere, then they should well have a presence here too.
Intergalactic travel is much harder than intragalactic. It's conceivable that even civilizations that colonize their galaxy might not make it further.
Why would you think so?
If the speed of light is the limit, both are impractical. If it is not, I don't see why do you assume that physical distance matters at all.
Both are wildly impractical (at least, by modern-human-technology standards), but intergalactic is several orders of magnitude more so. The speed of light really isn't much of an obstacle within a single galaxy; travel at .01c or less is plenty to populate every solar system in "only" a few million years.
It's believable that a technologically advanced society can cross a galaxy by star hopping and colonization of successive planets, maybe even without generation ships or cryopreservation. E.g. after taking into account relativistic effects, constant acceleration/deceleration at 1g gets us from Earth to Alpha Centauri and back well within a human lifetime. But you can't star hop between galaxies. There's nowhere to pick up supplies aside from maybe hydrogen and helium. Even at full lightspeed you need ships that are capable of running for 100,000 years to reach even the nearest galaxy. Is it feasible to build a fire-and-forget colony ship that could survive 10E5 years in space and arrive in working shape? Maybe if you did it with some really robust panspermia or something, and were willing to lose 99% of the the ships you sent out. I.e. just maybe you could transmit biology, but I very much doubt intergalactic civilization is feasible.
100,000 years from the perspective of outside observers, the amount of subjective time can be made arbitrarily small.
Yes, but the closer you get to lightspeed the bigger problem you have with any collision with any small particle.
You assumption holds if constant acceleration/deceleration at 1g is vastly easier to achieve than generation ships or cryopreservation. If you assume the opposite, then you suddenly can colonize the entire universe, only very-very slowly. :-)
No, not really. Even if generation ships or cryopreservation are easier to achieve than 1g over intragalactic distances, it still doesn't seem likely that it's possible to make them work over the 100,000 lightyears minimum between galaxies. To plausibly ship living beings between galaxies you either have to invent science fictional fantasies like Niven's stasis fields or figure out how to send a lot of seeds very cheaply and accept that you'll lose pretty much all of them. I'm not sure even that's possible.
To me it seems likely that if if you can cryopreserve someone for a 1000 years, you can cryopreserve someone more or less indefinitely.
This discussion is pointless. What seems likely to me or you now has no connection to actual likelihood of the technology.
Entropy is a thing. Keeping a machine running for 10 years without regular maintenance is challenging. 100 years is very hard but within the realm of feasibility. 1000 years might be doable with advanced enough self-repairing technology and access to sufficient fuel. 100,000 years? There's no way any moving part of any kind is going to keep going for that long. maybe if you can figure out a way to eliminate all moving parts of any kind; but even then I suspect random radiation and micrometeorites might erode any ship beyond hope of recovery. Perhaps there's little enough of that in the intergalactic void that intergalaxy travel is possible, but I wouldn't rate it as likely.
To grab another idea from Niven (specifically the Puppeteers), gravity manipulation to get a small traveling solar system would probably work, though it would take an enormous amount of time. I'm not an astrophysicist, but you could get solar wind to keep protecting you from small stray objects and presumably could watch the path ahead to protect yourself from other collisions.