Struck with a belief in Alien presence

by [anonymous]1 min read11th Nov 2012113 comments

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Recently I've been struck with a belief in Aliens being present on this Earth. It happened after I watched this documenary (and subsequently several others). My feeling of belief is not particular interesting in itself - I could be lunatic or otherwise psychological dysfunctional. What I'm interested in knowing is to what extend other people, who consider themselves rationalists, feel belief in the existence of aliens on this earth, after watching this documentary. Is anyone willing to try and watch it and then report back?

Another question arising in this matter is how to treat evidence of extraordinary things. Should one require 'extraordinary evidence for extraordinary claims'? I somehow feel that this notion is misguided - it discriminates evidence prior to observation. That is not the right time to start discriminating. At most we should ascribe a prior probability of zero and then do some Bayesian updating to get a posterior. Hmm, if no one has seen a black swan and some bayesian thinking person then sees a black swan a) in the distance or b) up front, what will his a posterior probability of the existence of black swans then be?

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At most we should ascribe a prior probability of zero and then do some Bayesian updating to get a posterior.

I think you'd have to call that "Bayesian not-updating". If your priors include 0 or 1 those beliefs will not change through Bayesian updating.

The prior is P(A), which we have said is 0. The posterior is P(A|B), which happens to be a fraction with 0 as the numerator!

4[anonymous]8yI get it.

Prior to watching the video, I have a very low estimate of the probability of aliens on earth (intelligent aliens visiting within human history, p ≈ 0.0001, intelligent aliens sending probes of any kind to earth during human history, similar, anything of alien origin coming to Earth over it's entire history: p ≈ 0.1, though I could easily be persuaded of a higher or lower estimate).

We'll see what effect the video has on those estimates.

--After watching the first half hour, taking comments in a window to the side throughout--

"Halt and his team locate three indentations [dramatic pause] in the shape of a triangle" in a very authoritative voice.

"Over two days, 60 personnel reported that they had seen a UFO." How were they asked?

They really like triangles. "my wife and I saw three bright white lights [dramatic pause] in triangle formation". Triangle formation, as oppposed to a line? Either way, it would have sounded significant and ominous.

The original investigation is missing any confirmatory evidence--but that also means it lacks any disconfirmatory evidence. This is exactly what you would expect to see in unexplained cases if there actually was nothing ... (read more)

2[anonymous]8y"The original investigation is missing any confirmatory evidence--but that also means it lacks any disconfirmatory evidence. This is exactly what you would expect to see in unexplained cases if there actually was nothing unexplainable going on." Apropos what one would expect to see, let me quote from Wikipedia on a US military study: "35% of the excellent cases were deemed unknowns, as opposed to only 18% of the poorest cases. This was the exact opposite of the result predicted by skeptics, who usually argued unknowns were poorer quality cases involving unreliable witnesses that could be solved if only better information were available." http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14 [http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14]
2Giles8yOK, this one's tough to analyse - big interplay of factors here. Basic classification of events: * Hallucinations - only one observer. Likely to be classified as low quality/crackpot or low quality/unknown * Seeing the moon etc. and thinking it's a spaceship - pretty much same as hallucination * Foreign military craft - Not clear whether these would be classified as "unknown" or "inconclusive". Skew towards high quality as more likely to be flying around military bases & hence seen by military personnel (also more likely to be seen by radar) * Undiscovered weather phenomenon etc. - probably classified as "unknown", no bias towards high or low quality reports * Alien spaceship - likely classified as "unknown". Plausible bias towards high quality as again we might expect to find more of them around military bases. * Poor quality hoax - likely classified as poor quality and miscellaneous. * Elaborate hoax - plausibly classified as high quality (can get multiple witnesses) and unknown. The following factors might further skew how many events get reported or how they are classified: * Military personnel more likely to report everything unexplained that they see, ordinary people more likely to only report really weird stuff. Bias towards low quality/unknown * Opposite effect may be in play - ordinary people get spooked by anything, military personnel more used to seeing odd stuff from time to time. Bias away from low quality/unknown * When UFO gets reported, a bunch of people phone in saying they've seen the same thing when really they haven't. Increases apparent number of witnesses - so adds noise to high/low quality but doesn't skew known/unknown classification * Self-disbelief: people won't report very unusual sightings unless they are military or have other witnesses or have corroborating evidence. Bias towards high quality/unknown * Ridicule, refusing to accept reports etc. - same effect as self-disbel
2Desrtopa8yI'm not sure why we would expect that. If I were constructing a model of what I would expect of alien visitations, I don't think that would be part of it. If I were constructing a model of what I would expect from alien visitations though, I doubt it would resemble any of the recorded observations at all; I suspect that they would be either completely open and unambiguous, or totally unnoticed (if a race with the technology for casual interstellar travel wanted to avoid attention, I expect that they could avoid it completely.)
1[anonymous]8yYou forgot swamp gas. What you just did is suggest a series of hypothesis as to what could explain the evidence. That is a part of the scientific method, but it is not all of the scientific method. The scientific method also includes testing the various hypothesis against the evidence, for each and every case. You forgot to do that.
1Kingoftheinternet8yIf you want that to happen then you're going to need to do it yourself. Nobody else here is interested enough in this subject.
1[anonymous]8yThey already did it! You just say "whatever" to their effort.
4Kingoftheinternet8yYou mean in the History channel documentary and other videos on Youtube, or something else? I don't usually like consuming knowledge in documentary form because it's 1. slower than reading and 2. much easier to make emotion-based/nonsensical arguments without your audience noticing. Perhaps you could provide us with a summary of what happened when people tested Giles' explanations? If there's good text-based discussion you can link to us then I'd also be interested in that.
0faul_sname8yThis confuses me. I'll have a look at the report. Do you know what proportion of the unknowns are poor cases as opposed to excellent cases (I would guess there are far more poor cases than excellent cases).
2[anonymous]8yI like your approach to this. (no joking) --- update: --- Good thoughts. Many of your points are not primary evidence though. Primary evidence would be eg. a flight track log for an airliner showing that the airliner passed by right where some people simultaneously were having a sighting of an unidentified flying object. If you didn't find the first half hour convincing you probably won't find the rest convincing either. What fuels my current belief is the sheer mass of observations. There are many documentaries and they portray many cases: http://www.youtube.com/playlist?list=PLjEhkqEuqXzEDEWQ3aQhqT8ToAZJ1mLmU [http://www.youtube.com/playlist?list=PLjEhkqEuqXzEDEWQ3aQhqT8ToAZJ1mLmU] Eyewitnesses can be error prone but can thousands of them be 100% erroneous? That's not how we usually treat our sensory input. Normally we attribute at least some value to it (this reasoning isn't primary evidence either). I wish I had geographic data, but I don't.
7TimS8yIn short, yes [http://www.innocenceproject.org/understand/Eyewitness-Misidentification.php]. In a country of hundreds of millions of people, finding thousands of people with any shared characteristic is not surprising. As faul_sname said, I would expect at least hundreds of thousands of people to be eyewitnesses to anything happening over a major city. Independently, our current knowledge of physics strongly suggests that interstellar travelers arriving in this solar system would be visible (during deceleration) to any serious observation of the night sky, whether Mayan, Ptolemaic, Galilean, or modern. The absence of any record that suggests arrival is strong evidence against interstellar aliens. Primary evidence includes eyewitnesses. And even if it didn't, the secondary evidence is so strong that total absence of relevant primary evidence is irrelevant. You asked elsewhere why you are getting downvotes, and the brief answer is that you are dramatically over-weighing the strength of the relevant evidence.
2[anonymous]8y"In short, yes. In a country of hundreds of millions of people, finding thousands of people with any shared characteristic is not surprising." Do we really have a parallel here? I'm sure you could find a rather large number of people with horrible eye-witness quality. But with UFO-sightings that's not what is happening. Those people who observe UFOs does so by chance, not because they have previously been selected for their fallibility. Indeed there are many pilots (both civil and military) among the witnesses. The link you point to says this: "Eyewitness misidentification is the single greatest cause of wrongful convictions nationwide, playing a role in nearly 75% of convictions overturned through DNA testing." I guess it is mostly the cases that have previously been screened for being likely overturning candidates that are actually brought to court to get overturned. Even more selection arises in the courts decision to overturn or not. Thus, only looking at cases that actually got overturned will give us a highly distorted view. We need statistics on the eye witness quality of random persons. "As faul_sname said, I would expect at least hundreds of thousands of people to be eyewitnesses to anything happening over a major city" Countering secondary evidence with secondary evidence I could suggest: 1. It was at evening time and dark outside. Most people would be inside at that time and from inside it can be hard to see whats outside when it is dark outside and there are many other point-lights out there. There was no sound associated with the incident. 2. According to Wikipedia (article named 'Phoenix Lights') "thousands of people" saw the object/lights. Probably not all of them reported the incident to the authorities. 3. Some people probably wanted to avoid ridicule and thus didn't talk about what they saw.
1TimS8yThere's no particular reason to think this is true. Availability of DNA evidence or eyewitness evidence is relatively independent. Thus, it is reasonable to treat the DNA & eyewitness (DNA+e) cases as representative of all eyewitness cases. In the DNA+e cases where DNA is inconsistent with guilt, either the DNA or the eyewitness must be wrong. And we have independent reasons to think DNA is more reliable than eyewitnesses. If DNA really is a representative sample of cases, and DNA+e is a representative sample of DNA cases, the wikipedia statistic you cited suggests that 75% of eyewitness testimony is wrong. As an aside, the research is pretty clear that there is a substantial difference in eyewitness accuracy based on whether or not the witness knew the perpetrator. Now, there are reasons to believe the DNA cases are not a random sample of crime, particularly because certain kinds of crimes are more likely to leave analyzable DNA (eg. rape vs. bank robbery). But that doesn't suggest that they aren't representative of eyewitness cases.
2[anonymous]8yBut at least the court outcome will skew the selection. Also we have plenty good statistics for eye witness reliability when it comes to UFO sightings and these statistics give a very different conclusion: "Only 1.5% of all cases were judged to be psychological or "crackpot" cases" http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14 [http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14] Shouldn't we use the most relevant statistics?
4Desrtopa8y98.5% "non crackpot" cases is very different from 98.5% non-false positive. I'm using a hotel lobby computer right now, and can't rewatch the video for confirmation, but I believe that this [http://www.youtube.com/watch?v=T69TOuqaqXI] video contains a highly relevant anecdote (as well as being generally relevant.) The author of the video was witness to a phenomenon which his host believed could only be accounted for by ghost activity. The author of the video realized that the phenomenon was, in fact, caused by a fan being on which his host didn't notice. But if he hadn't been there, his host could have conveyed the story as a phenomenon that could only be explained by ghost activity, and the relevant detail, the fan, that was the real explanation of the phenomenon, would have been omitted from the account. Nobody hearing the secondhand account could have known the real explanation, only lumped it in with the expanse of possible answer space. And a normal, non-crazy person who believes they witnessed ghost activity, would most likely deny that there had been a fan on that they had failed to notice, and indeed take offense at the very suggestion, because they would interpret it as an attack on their credibility. If a phenomenon has a real incidence rate of zero, but any false positive rate at all, then all accounts will be false positives. Suppose that the real incidence of alien visitations of earth is zero, but 0.1% of the population has experiences they interpret as signs of alien visitation, for which they cannot come up with alternative explanations. That would account for hundreds of thousands of reports of alien visitation in America, all of which would be false positives.
2[anonymous]8y"98.5% "non crackpot" cases is very different from 98.5% non-false positive." I fully agree, and indeed most observations turns out to be easily explainable. The interesting question is not "can eye witness reports be fallible?" Of course they can. The interesting question is "is every single ufo observation completely unreliable?" The science says that 22% of thousands of observations of ufos are truly explainable by any phenomenom we now. Thus the answer to the latter question is an unevoquivally "NO". source: http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14 [http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14] "If a phenomenon has a real incidence rate of zero, but any false positive rate at all, then all accounts will be false positives. Suppose that the real incidence of alien visitations of earth is zero, but 0.1% of the population has experiences they interpret as signs of alien visitation, for which they cannot come up with alternative explanations. That would account for hundreds of thousands of reports of alien visitation in America, all of which would be false positives." There's a trick here. Were not interested in eyewitnesses own ideas about whether they saw an alien spaceship or not. Were interested in the subsequent analysis performed by expert scientists and the like. All we want from the eyewitnesses are their accounts of size, shape, flight path, lights etc. Then we corroborate this with radar data and see if we can find a plausible earthly explanation. Also your scenario simply does not explain all the cases that involve radar trackings, videos and photos. The latter can be faked but it is rare that we hear about military personnel faking radar data before handing it over to their superiors, just for fun.
3Desrtopa8yThere's a huge difference between "we can't think of a plausible earthly explanation" and "alien visitation is more likely than an explanation we haven't thought of yet." In the case of the "ghost" experience, if we were hearing a secondhand account from the original witness, we would have "no earthly explanation," because they wouldn't convey the information that would actually make it explainable. Sometimes reports might be due to things that are kept secret for good reason, like the test flights of the B-2 "Spirit" bomber, which looks for all the world like a flying saucer, and was classified by the military. Others might be due to physical phenomena that are not yet understood, and some may be due to priming and erroneous pattern recognition causing people to exaggerate observations that are not particularly out of the ordinary. These are all events that we should expect to happen in the absence of any sort of extraterrestrial activity. But attributing the sorts of events described in these reports to intelligent life forms from different star systems travelling all the way to the vicinity of Earth and making such vague and dubious appearances is a profound case of privileging the hypothesis.
2[anonymous]8yFine, with our current knowledge knowledge of physics the Alien trick would be almost impossible. But shouldn't we rather estimate the probability that future physicists would discover something radically new? And isn't this proposition significantly harder to estimate? Making your secondary evidence less strong? "You asked elsewhere why you are getting downvotes, and the brief answer is that you are dramatically over-weighing the strength of the relevant evidence." That's why I said that my belief was not of much interest :) The topic of this thread really shouldn't be about my belief. It would be just as interesting as discussing the aesthetic merits of my left little toe.
1Kingoftheinternet8yBeliefs don't exist outside of people (and other animals). If we want to talk about beliefs, we have to point inside at least one person's head.
1[anonymous]8yI hoped the “yes” link was to http://xkcd.com/718/ [http://xkcd.com/718/] ...
1[anonymous]8y"Independently, our current knowledge of physics strongly suggests that interstellar travelers arriving in this solar system would be visible (during deceleration) to any serious observation of the night sky, whether Mayan, Ptolemaic, Galilean, or modern. The absence of any record that suggests arrival is strong evidence against interstellar aliens." Just curious: Does human kind has in place 24/7 surveillance of every part of the sky around the globe? Citation?
2Decius8yClose enough [http://en.wikipedia.org/wiki/History_of_supernova_observation] to see the kind of effect that would be present from decelerating from interstellar speeds, assuming that aliens noticed us sometime after we made electromagnetic fields that exceeded background noise in orbit.
1[anonymous]8yAs I'm not sure whether you will be notified on new comments to the original post (including my new fancy comment to the original post) I give you the permalink to it here: http://lesswrong.com/lw/ffd/struck_with_a_belief_in_alien_presence/7t4i [http://lesswrong.com/lw/ffd/struck_with_a_belief_in_alien_presence/7t4i]

An unidentified flying object is just that: unidentified. Not "identified as alien". The argument is isomorphic to "God in the gaps", for which I think there are few takers here.

1[anonymous]8yI agree. Just observing with your eyes, camera, military ground radar and nose radar a huge yellow-ish glowing object with the diameter of two aircraft carriers, in front of your Boing 747, tracking you as you go, over a long distance, and even following you around in a 360 degree turn is not evidence of little green men. But where do we go from there? There are a limited amount of possible explanations, all which is eliminated as plausible by any one involved (air traffic control personnel, the pilots, military radar stations, meteorologists). It would be a leap of faith to conclude "aliens", but would it be a bigger step than concluding any hypothesis' already deemed implausible? (eg. weather balloons). Using your curiosity, investigate these cases and decide what hypothesis will provide the smallest leap of faith. You can start by reading the wikipedia-article on the incident: http://en.wikipedia.org/wiki/Japan_Air_Lines_flight_1628_incident [http://en.wikipedia.org/wiki/Japan_Air_Lines_flight_1628_incident]but there are many many more cases: "An Air Force major is ordered to approach a brilliant UFO in his Phantom jet over Tehran. He repeatedly attempts to engage and fire on unusual objects heading right toward his aircraft, but his missile control is locked and disabled. Witnessed from the ground, this dogfight becomes the subject of a secret report by the U.S. Defense Intelligence Agency. In Belgium, an Air Force colonel investigates a series of widespread sightings of unidentified triangular objects, and he sends F-16s to attempt a closer look. Many hundreds of eyewitnesses, including on-duty police officers, file reports, and a spectacular photograph of an unidentifiable craft is retrieved and analyzed. Here at home, a retired chief of the FAA’s Accidents and Investigations Division reveals the agency’s response to a thirty-minute encounter between an aircraft and a gigantic UFO over Alaska, which occurred during his watch and is documented on radar." fr
2RichardKennaway8yHow about concluding "I don't know"?
1[anonymous]8yThat's a very good conclusion. I would be satisfied by just sticking to that. That being said, having all sorts of pilots and radars report flying objects in the sky, crossing air space boundaries as they like, going close to both civilian and military crafts, really should provoke massive investigation and massive public awareness. It doesn't!
5Desrtopa8yWhy? We don't have evidence that it's causing a lot of aviation accidents. If you have a high prior for the observations being caused by some sort of extraterrestrial activity, then it probably merits serious investigation, but if you just file it with all the other "I don't know" phenomena, there's nothing to single it out as meriting massive public awareness. We don't know what causes ball lightning [http://en.wikipedia.org/wiki/Ball_lightning]. It's weird and mysterious, and it's been observed for hundreds of years or more, and we really don't know what's up with that. If we figure out what causes it, it'll lay a longstanding mystery to rest, but it probably won't revolutionize the way we live, we'll just be less confused. As a scientifically inclined individual, I'm curious about lots and lots of stuff. I'd certainly like to know about the reasons for some of these allegedly extraterrestrial observations, which I don't know how to explain. But one thing that's incredibly frustrating is when people fixate on particular unexplained observations, and insist in the absence of good evidence that the explanations must be revolutionary and life changing. When people read about things like the faster-than-light neutrino observations at CERN, or unexplained observations in the night sky, and act like anything short of a paradigm shift in our basic picture of the universe would be a ripoff, it's really disheartening, because most unexplained observations just don't turn out that way, and it's sad to see people refusing to be satisfied by the way reality actually works [http://lesswrong.com/lw/or/joy_in_the_merely_real/].

I think you may be confused by an oversimplification of Occam's Razor: "Extraordinary claims require extraordinary evidence." That's not actually how you derive a prior - the very word "extraordinary" implies that you already have experience about what is ordinary and what isn't. If we really throw out all evidence that could tell us how likely aliens are, we end up with a probability which (by the usual method of generating priors), depends on the information-theoretic complexity of the statement "There are aliens on earth."... (read more)

1[anonymous]8y"I don't think that generic aliens should be considered especially improbable a priori - before the evidence is considered. I think that they are unlikely a posteriori - based on the fact that we don't see them" Citation? There's plenty of evidence for non-man made, non-hoaxed, non-astronomical, non-weatherrealated unidentified flying objects according to studies made by the US and French military: http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14 [http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14] most important highlights: http://lesswrong.com/lw/ffd/struck_with_a_belief_in_alien_presence/7t4i [http://lesswrong.com/lw/ffd/struck_with_a_belief_in_alien_presence/7t4i] The black swan example was just a general pondering. "I don't think that generic aliens should be considered especially improbable a priori - before the evidence is considered. I think that they are unlikely a posteriori - based on the fact that we don't see them. I think that any intelligent space-faring life would be busy building spheres around stars (if not outright disassembling the stars) as quickly as they spread out into the cosmos. So we'd notice them by the wake of solar systems going dark. At the very least, there's no reason to think that they would hide from us, which is what these scenarios tend to require" This is very speculative to me. I don't think we can use it as evidence for or against.
2aaronde8yEven if you could rule out man-made and weather-related causes for some UFOs, that wouldn't imply that they were caused by an extra-terrestrial civilization either. Some UFOs may still be unexplained, but all that means is that we don't know enough about them to say what they are. That said, I don't think you can rule out weather and human craft. Others have already explained why I find the "primary" evidence unconvincing. Let me put it this way. My guess of what an interstellar civilization would look like makes predictions about what it would be like to encounter that civilization. Those predictions are not satisfied. This is strong evidence that no extra-terrestrial civilization (as I understand the term) has made it anywhere near us. One of the reasons you were downvoted is that you asked us to evaluate evidence for "Aliens". But that is impossible until you explain what you mean by "Aliens". Obviously, there is something about these UFO sightings that makes you think they are more likely to be caused by aliens than by weather. Which implies that you think you know something about aliens that makes them a better explanation. So what is it that you think you know about these "Aliens"?
1[anonymous]8y"Even if you could rule out man-made and weather-related causes for some UFOs, that wouldn't imply that they were caused by an extra-terrestrial civilization either." I agree. But in the cases of grey beings emerging from UFOs we can at least conclude that grey beings can occupy UFOs, if we trust primary evidence. This would be a massive discovery in itself, so why don't we hear about it? We don't have to conclude they come from outer space - who knows, they maybe live underground. Lets not speculate on that as we have plenty of interesting observations to delve into already - little gray men emerging from airborn thingies is HUGE in itself. "So what is it that you think you know about these "Aliens"?" It's not that I know anything about aliens. It's that more earthly explanations are completely implausible in many cases. "That said, I don't think you can rule out weather and human craft." In which cases? Just all cases, a priory? Or did you go through all previous sightings and came to that conclusion in every one case? Maybe others did the study for you, so you could provide a reference?
4aaronde8yUm, no. A short guy in a grey suit stepping off a helicopter is a little grey man emerging from an airborn thingy. No. I don't see the point in digging through all the reports, when the reports I have heard about have been so underwhelming. I was skipping around, watching bits and pieces of the video you linked, until Manfred pointed this out: So they basically lied. I actually haven't ever held a geiger counter, so I had no way of knowing this. If asked to explain it, I would have had to admit that something weird was going on that I couldn't explain. Except there's a perfectly mundane explanation, and the only reason I was confused is because I was misled about the significance of the reading in the first place. After that I didn't see the value in watching the rest of the documentary. So I have a better idea. You tell me what you think is the single most convincing incident, and I will tell you, * How convincing I find the report on its own, and * How convincing it would be, assuming that there were thousands of similar, equally reliable reports.
1[anonymous]8yAs mentioned elsewhere, this kind of reasoning: "I don't think that generic aliens should be considered especially improbable a priori - before the evidence is considered. I think that they are unlikely a posteriori - based on the fact that we don't see them. I think that any intelligent space-faring life would be busy building spheres around stars (if not outright disassembling the stars) as quickly as they spread out into the cosmos. So we'd notice them by the wake of solar systems going dark. At the very least, there's no reason to think that they would hide from us, which is what these scenarios tend to require (though I haven't watched the documentary)." is at best secondary evidence and thus shouldn't be weighted as high as primary evidence such as sightings or knowledge of time+space-correlating weather balloon flights.

Watched the first 15 minutes, didn't seem super convincing, so I stopped - have to put bread in the oven soon. Anyhow, it's really easy to just make shit up on television - by which I don't (just) mean lying, making things up is just a natural consequence of rationality failure. The unreliability of eyewitness testimony and all that. The only things in the first 15 minutes that weren't eyewitness were the picture and the geiger counter reading. If you go back and look at the picture, it's a shitty non-equilateral triangle made out of two things that loo... (read more)

7[anonymous]8yIt's especially easy to do so on TV. Anyone interested should check out this video [http://www.youtube.com/watch?v=07NMglQX6gE]. I have a high prior that the documentaries that the OP links to use the same sort of tricks described therein.
4wesley8yWow. I predict that this will significantly increase my skepticism of TV interviews. I already knew this sort of thing could be done with quotes, but was completely ignorant of how imperceptible good audio edits can be, and of the cut-away technique.
2faul_sname8yThat is... slightly terrifying. Also extremely interesting. Thank you for pointing that out.
2[anonymous]8y"Anyhow, it's really easy to just make shit up on television - by which I don't (just) mean lying, making things up is just a natural consequence of rationality failure. The unreliability of eyewitness testimony and all that." The Wikipedia-article on reliability of eye witness testimony only mentions this statistics: "The Innocence Project reports eyewitness misidentification occurs in approximately 75% of convictions that are overturned" Unfortunately this statistics will be very hard to generalize, as argued by me in another comment: "I guess it is mostly the cases that have previously been screened for being likely overturning candidates that are actually brought to court to get overturned. Even more selection arises in the courts decision to overturn or not. Thus, only looking at cases that actually got overturned will give us a highly distorted view. We need statistics on the eye witness quality of random persons." Source: http://lesswrong.com/lw/ffd/struck_with_a_belief_in_alien_presence/7t4w [http://lesswrong.com/lw/ffd/struck_with_a_belief_in_alien_presence/7t4w] We need statistics that can explain why every single person among thousands of witnesses has consistently fumbled in their eye-sight roll. Also we need to forget the fact that this US military report on UFOs only attributes 1,5% of sightings as being caused by psychological factors: "Only 1.5% of all cases were judged to be psychological or "crackpot" cases" http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14 [http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14]
3Manfred8yLooks like they mean psychological as in hallucination, not psychological as in mistaking something that actually exists for a UFO and then making stuff up because you're not being rational - if you mistake the moon for a UFO (seriously happens [http://www.telegraph.co.uk/news/newstopics/howaboutthat/8854717/999-caller-mistakes-moon-for-UFO.html] ), and say "it's moving this way, it has all these lights all over it" (which is the sort of thing I mean by "making stuff up"), that would be "86% of the knowns were aircraft, balloons, or had astronomical explanations." By witnesses you mean, every person who later went on to claim that they saw a ufo, while the people who think they just saw the moon don't get interviewed on the news? "Shocking expose, local woman sees moon." The unreliability of eyewitness testimony was originally an experimental psychology effect [http://heinonline.org/HOL/LandingPage?collection=journals&handle=hein.journals/juraba15&div=37&id=&page=] . I shouldn't have just linked to wikipedia without checking it more - here's [http://www.simplypsychology.org/Eyewitness%20Testimony.pdf] some [http://www.simplypsychology.org/loftus-palmer.html] experimental stuff [http://www.psychology.iastate.edu/~glwells/Wells_articles_pdf/Eyewitness_Testimony_Ann_Rev.pdf] .
2[anonymous]8y"Looks like they mean psychological as in hallucination, not psychological as in mistaking something that actually exists for a UFO and then making stuff up because you're not being rational - if you mistake the moon for a UFO (seriously happens), and say "it's moving this way, it has all these lights all over it" (which is the sort of thing I mean by "making stuff up"), that would be "86% of the knowns were aircraft, balloons, or had astronomical explanations."" Sure, most observations are just ordinary things. But the report didn't leave it to the eye witnesses to judge whether an observation was of ordinary stuff or not. They did their own analysis of of the observations and found 22% to be genuinely unknown, according to very strict criteria. So we know that objects fly around and that they do it in ways that man made things cannot do. That's a very interesting conclusion in itself - we don't have to say "it is aliens" to make it very interesting. This conclusion really should spark enormous scientific investigation. "By witnesses you mean, every person who later went on to claim that they saw a ufo, while the people who think they just saw the moon don't get interviewed on the news? "Shocking expose, local woman sees moon."" This sentence has several problems: 1. You didn't really comment on my proposition that ALL eye witnesses has to fumble. 2. The scenario you describe is very far from how the most serious cases have unfolded. Do your research. 3. I'm not interested in whether the observer says "it's a UFO". I am talking about post observation analysis of observations by experts. You knew that perfectly well as I had just linked to the Wikipedia article on the study. Please be serious.
3Desrtopa8yHe did. It's not necessary for all eyewitnesses to be mistaken. If 600 people report something that sounds like possible extraterrestrial activity, but there were 60,000 people there to see it, only 1% have to "fumble their eyesight roll," and if they're given opportunity to converse with each other beforehand, a few people who think they saw something strange may be able to convince many other people to revise their memories so they also believe they saw something strange. This sort of thing happens all the time, and almost certainly accounts for a proportion of eyewitness accounts even if we assume that there really are genuine cases of people witnessing extraterrestrial activity.
2Decius8yIt's pretty clear that most eyewitness accounts of observations with ordinary explanations is correct. What we are left with is a tiny minority of people who observed an ordinary event and concluded that it was an extraordinary event. A tiny percentage of witnesses, multiplied by the large population and large number of ordinary events, yields a number roughly consistent with the numbers experienced. Lights in a triangular formation is pretty typical for aircraft; each type has several different possible configurations of light, and almost all of them involve three or more lights that aren't in a line. Without anything to create perspective, it is basically impossible to tell the distance of an aircraft by eye even in the day (experienced people can identify the type, know the size, and do the trig to convert degrees of arc or elevation and altitude to distance, but those people typically recognize aircraft lights as aircraft lights). Three lights in a triangular formation, perceived as distant and far apart and with no audible noise, is roughly what one would expect to experience if a Cessna Caravan was making a nonstandard approach to a nearby airport. If the airport lacks an operating control tower (like most municipal airports in the middle of the night), it is reasonable that air traffic never communicated with the aircraft. Further, it is perfectly legal for such an aircraft to fly without an installed transponder, meaning that the radar track (if observed) will show something there that cannot be proven to be an aircraft. Think you don't have a municipal airport near a given witness? The US has about 13179 public and private use airfields, roughly one for every 300 square miles.

Another question arising in this matter is how to treat evidence of extraordinary things. Should one require 'extraordinary evidence for extraordinary claims'? I somehow feel that this notion is misguided - it discriminates evidence prior to observation. That is not the right time to start discriminating. At most we should ascribe a prior probability of zero and then do some Bayesian updating to get a posterior.

As ParagonProtege noted below, if your prior is 0, then your posterior is also zero no matter how compelling the evidence you observe. As I unde... (read more)

Should one require 'extraordinary evidence for extraordinary claims'? I somehow feel that this notion is misguided

Extraordinary just means low probability. So if some claim is extraordinary (in this case, aliens) then it has a low probability. Similarly, you would need extraordinary evidence to update the prior to the "ordinary" range. If you look at the simple version of Bayes Theorem, it is P(H | E) = P(E | H)P(H) / P(E). If both P(E) and P(H) are low (i.e. extraordinary) then they will sort of cancel each other out and P(H | E) will be clos... (read more)

Another question arising in this matter is how to treat evidence of extraordinary things.

Dealing with extraordinary claims has not gotten the attention it deserves, IMO.

It gets to the distinction between an explanation, and a predictive model. Explanations assuage mental anxiety over the unknown. Predictive models, in general, allow you to do something. If, in some particular case, the predictive model associated with an explanation doesn't allow me to do something, it is not a useful model.

Let's assume some advanced alien intelligence is patrolling t... (read more)

0mwengler8yThis MIGHT argue against putting much resources into refining your estimate of what is really going on with these aliens. It hardly argues for the validity of the hypothesis. I think the continuing novelty of the world, the fact that the world continues to unfold in a way consistent with their being just gobs and gobs more you don't know than that you do know, argues for assuming that there is very much knowledge that you, or perhaps your children or your children's children, won't be able to do something with eventually. What of knowledge of aliens among us who may or may not be much more intelligent than us, who may or may not have motives that are hostile to us, that are essentially much more unknown than unknowable? I can think of millions of ways this might be useful, to me as an individual, to my family in contrast to the rest of humans, and so on. If nothing else, I will be better prepared to act if/when the aliens are exposed or if/when they expose themselves, while my more skeptical friends will be caught flat footed and will wind up in the test kitchens.
[-][anonymous]8y 2

What about this: A piece of shrapnel, found at the Roswell crash site, that doesn't have the isotopic composition that earthly metals has:

" Kimbler says the isotope work is so important because the ratios are “very much like our fingerprints.” Certain concentrations of elements on earth are unique to Earth. So if you know isotopic ratios for magnesium, it will be the same for anything on earth with magnesium, but if it is not from Earth, it will have a different ratio. For instance meteorites have different ratios because they are not from Earth. Isot... (read more)

6faul_sname8y...really? Here is the data they found. Isotope | Measured | Background --------+----------+------------ Mg-24: | 79.1±0.5 | 78.6 Mg-25: | 10.1±0.5 | 10.1 Mg-26: | 10.8±0.5 | 11.3 You will note that the natural background concentrations fall within the error bars of the measurements. Meaning no significant difference. When you plot it on a graph with no error bars, it looks like the measurement is really anomalous. When you notice that the error bars are as large as they are and the measurement errors are in opposite directions, it becomes quite obvious why that measurement falls so far from the line he plotted. Consider that the error bars are 0.5% in either direction, and the graph is only 1% on a side. That means you would expect a measurement of a sample from Earth to fall... somewhere on the graph. Not any more specific than that though. It is things like this that make us skeptical of supernatural claims. If the aluminum compound actually came from space, we would expect a much higher concentration of Al-26 (extremely high levels, in fact, whereas material on Earth has effectively none), and that would constitute much stronger evidence than slightly anomalous but not significant differences in Magnesium isotope ratio. It's not that there are no observations that could persuade us, it's that we don't see any persuasive observations. If they had found high concentrations of Al-26, that would have been news (in fact, since Al-26 has a half-life of 720,000 years, anyone who wanted to could see if they could find any Al-26 at the Roswell site even now, and if they could, that would be strong evidence that the craft was extraterrestrial in origin). In fact, you could go now and perform those tests. But you already know what the result would be. You're already making excuses in your mind for why you won't find any Al-26 at the site, like any alien craft would be shielded (in which case, why would the Magnesium concentrations be off). You
0drethelin8yWhat can you use space aluminum for? Is it harder? Lighter? Does it float when you shine a red light on it?
[-][anonymous]8y 2

Maybe this talk by Stanton Friedman will be of more interest to this audience, than a history channel documentary: http://www.youtube.com/watch?v=uOAvL1O3DyM

[-][anonymous]8y 2

I might watch it later. (I'm not reading the other comments yet because I don't want to be primed.)

[-][anonymous]8y 2

I have gotten 6 private messages as reply to this post (that has also been posted in this thread). Previously I've experienced the same. Why don't people just post in this thread only? Is it a culture thing?

3[anonymous]8yThe yellow/orange envelope notifies you that someone has responded to your comment in a thread. Those "private messages" you are seeing aren't really private messages - just a feed of others' replies to you. But I can see how that would be confusing, since that same icon also lights up when someone sends you a PM. (I trust someone more awake that I am can make this anecdote into a nice illustration for why we have low confidence in the reliability of eye-witness testimony about aliens.)
0mwengler8yOoops, misunderstood point of origial comment.
0ArisKatsaris8yYou didn't read loldrup's comment correctly. He says that the "private messages" were also posted in this thread. As others have explained, loldrup just misunderstood the meaning of the "INBOX" which doesn't include just private messages, but also the responses made to the thread.
0mwengler8ythanks.
0[anonymous]8yYour inbox shows all replies to you, not just personal messages. It's a convenience thing.
[-][anonymous]8y 2

Thanks for the informative replies.

Just for learning: why the downvotes?

3Manfred8yProbably just a way of saying "lurk moar [http://seemslegit.com/_images/33b92c9babd92d1ebdcae7817b3fa122/2661%20-%20b%204chan%20lurk-moar.jpg] ."
3[anonymous]8ySo it basically means "don't be a noob"?
3faul_sname8yApproximately. 4 downvotes is not a large number, so basically it's saying "this should go in an open thread, or you should spend a little more time editing before posting."
1Manfred8yWell, there are a lot of skills that go into not being a noob here, and only some of them will affect downvotes. But at least partially, yes.
3[anonymous]8ySo in this case, how could I have shaped my original post so as to not be downvoted?
2Manfred8yExternal shaping without changing anything else would be working on only one or two of those non-noob skills. So I'll give you some different advice: check out ye olde list of articles [http://wiki.lesswrong.com/wiki/Sequences] and spend some time reading whatever looks interesting - the "mysterious answers to mysterious questions" sequence probably being the most useful.
1[anonymous]8yIf people down vote out of a prior idea that alien visits just don't happen, then it seems a bit like prejudging. What i present here is huge amounts of evidence from government military studies, and people who hasn't studied the case starts by downvoting? How is that not prejudging?
1faul_sname8yIf there was a huge amount of evidence, it would be unjustified to reject the idea. But there isn't. It's possible to make a convincing case that there is evidence, but when you ask for the solid, unambiguous evidence (i.e. data that would be hard to fake), it's just not there. And you would expect any civilization that is capable of interstellar travel to be able to remain undetected by humans if they wanted to, or if not, you would expect those with the best instruments to detect them first. Mile-across, fast moving objects should show up, not just on military radar, but also on Doppler radar (what they use for looking at rainfall). Fragments from a crash-landed spaceship should have a significantly different isotope ratio than alloys on Earth. For that matter, you would expect a highly advanced civilization to have done some interesting stuff with Carbon (nanotubes, etc), not for them to still be using Aluminum. Basically, there are a bunch of things we would expect to see if there actually was a highly advanced civilization present and detectable. And we don't see those things.
0Kingoftheinternet8yIn your original post, you just presented Youtube videos. People here have very low expectations for videos about aliens on Youtube. If you'd linked to just that Blue Book report first then I bet people would've been much more receptive to what you have to say.
[-][anonymous]8y 1

Due to low karma i can't reply in the relevant comment thread, so I do it here:

Desrtopa wrote:

If you think there's an inconsistency in people's dismissal of UFO eyewitness accounts, I think you may not have grasped the principles of Bayesian reasoning yet.

Baysian reasoning says to treat all evidence equal. The prior may be low, say 0.01, but that's all. There is no weight of the prior that can change. Thus if we see new evidence the update of the probability isn't affected by some magic weight that could diminuize the size of the update arbitrarily muc... (read more)

2[anonymous]8yIn short: Desrtopa was right and I was wrong: all evidence is not equal.
2[anonymous]8yThis is the original comment from Desrtopa: If you think there's an inconsistency in people's dismissal of UFO eyewitness accounts, I think you may not have grasped the principles of Bayesian reasoning yet. Eliezer's introduction is here, but to add some subject relevant commentary: Eyewitness reports of unfamiliar things tend to be much less reliable than eyewitness reports of familiar ones. If a person witnesses someone they already recognize committing a crime, for instance, their description of the perpetrator is likely to be highly accurate, whereas a person who witnesses someone they don't recognize committing a crime is likely to give a description that's extremely unhelpful, and often worse than useless. So as a general principle, people reporting on unfamiliar phenomena tends to be weaker evidence than people reporting on familiar ones. If your girlfriend says she saw an eagle by the creek, and she often sees eagles and is well equipped to recognize them on sight, then her report is stronger evidence than that of a tourist who thinks they know what eagles look like, and saw a bird which fit their idea of what an eagle is supposed to look like, so they're pretty sure that's what it was, which is in turn stronger evidence than a report from someone who doesn't know what eagles look like at all, but saw a bird which they think fit the description of an eagle which they heard after seeing it. This is in addition to the fact that the single standard of Bayesian evidential reasoning demands larger amounts of evidence to raise less probable events to the point of likelihood. If seeing an eagle over the creek has a prior of .02, your girlfriend's say-so is more than enough evidence to accept the proposition, unless she's unusually dishonest. If she claims to have seen a gremlin, on the other hand, the prior is going to be much, much lower; if gremlins exist at all, they must be awfully rare and elusive to have avoided reliable observation thus far. So the like

An idea with more acceptance on this board is that we are more likely in a simulation than in the real world. This is more accepted at least in the sense that posts that support this hypothesis are not vote-bombed down.

An interesting thing to ponder is that in a simulated world we would be very likely to have what would be essentially aliens among us. The intelligences running the simulation would have not particular reason not to intervene in the simulation when and how they felt like it in ways that violated the physics of the simulation. These inte... (read more)

[-][anonymous]8y 1

So here are descriptions of some more scientific studies, conducted by the US and the French military:

http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14

It's interesting how the conclusion in the US report is at odds with their own data. If you read the section please read it thoroughly to get the details.

Okay I'm simply going to put (part of) the section out here (hope its okay). I have emphasized some places:

"In late December 1951, Ruppelt met with members of the Battelle Memorial Institute, a think tank based in... (read more)

This thread has mostly taken the form of "LessWrong tells loldrup why he is wrong," which has the unfortunate side effeect of making it very difficult to admit you are wrong, even if you later encounter evidence that you would have otherwise considered convincing.

What would you consider good evidence that there are no aliens on Earth?

1[anonymous]8ygood question. What would make me think black swans didn't exist if I had already seen one? The thing is, its hard to prove that something doesn't exist - you would at least have to turn every stone and every cloud on the planet.
0maia8ySo, just to clarify: For you to be 100% convinced that there are no aliens on Earth, you would have to examine or be convinced that someone else had examined every stone and cloud on the planet, and found nothing that appeared to be non-Earthly in origin. Is that right?
2Kindly8yThat would be true of a lot of people, so how about we set the weaker standard of being 99.99% convinced?
2[anonymous]8yI'm writing a bayesian calculation on this. I will come back when I'm done. It will help me and others assess the probability of aliens on earth.
[-][anonymous]8y 0

Just curious: why did the comment quoted below get down voted? While it may be a bit a bit colorful it raises an issue that is relevant in this case: do we discriminate between evidence a priori?

"Also, remember to apply even standards to evidence. If you flat out deny ufo eye witness accounts as being without epistemic value, also do this for all other eye witness accounts:

Your girlfriend says she saw an eagle over the creek? Didn't happen. And don't investigate any further.

Your friends talk about the beautiful yacht that left the harbor this morning?... (read more)

0[anonymous]8yThis was the follow up comment. Is it too colorful as well? "The same goes for radar: Today air traffic controllers attribute epistemic value to radar data on the question of determining size and movement of objects in the sky. However, they really should ditch their equipment as we attribute zero epistemic value to the radar signals if the objects it detects move in ways that current man made objects cannot or if the objects are larger than current man made objects (say, with a diameter of two aircraft carriers. Right?"
[-][anonymous]8y -1

also take a look at this:

http://www.youtube.com/watch?v=Hh1jDZoj2xs

It describes a case where a village sustains a long period of attacks by hot columns of light emerging from objects in the sky. The village is panicked and the military dives in and make a lengthy report.

If aliens are on earth their behavior is indistinguishable from no aliens being on earth. If I flip the switch in my head from believing that aliens are on earth to aliens not being on earth, what will I do differently?

6Vladimir_Nesov8y(Human-like level of intelligence) aliens imply many things, like reduced intelligence explosion risk and presence of alien-related risk. You might want to shift donations or research focus accordingly. (Getting outside the intent of your thought experiment, there is also the problem that just as a belief has implications, it has considerations that would sustain it, so an isolated incorrect belief won't survive on its own, you need systematic change in a lot of related knowledge (perhaps including some anti-epistemology) for it to take. Even if two beliefs have identical implications, they may have different causes, which is sufficient to distinguish them.)
3[anonymous]8ywell if there were absolutely no cues of evidence I would definitely see your point.
0drethelin8yAll the evidence is functionally useless. None of it says anything about what should be done or can be done.
2[anonymous]8yWhat's the link between evidence of what is, and prescription of what should be done? I think I could come up with a suitable prescription in the case of alien presence on earth: Try to contact them. Thus, now we have a prescription, but does that make the available evidence more or less convincing?
1drethelin8yBasically, the evidence, if it points to aliens, points to aliens who I can't touch or interact with, who ignore all human attempts at communication, and who can convincingly hide enough so that almost no one believes they exist. The Aliens are like an invisible dragon
0[anonymous]8yWell if there were absolutely no cues of evidence they would indeed be like the invisible dragon. So actually I think we agree. By the way, the reports also include conversations with them (obviously I can't know whether these reports are authentic). Also by the way: how can you so easily dismiss thousands of eyewitness reports as evidence? The studies does not align with that conclusion: http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14 [http://en.wikipedia.org/wiki/Project_Blue_Book#Project_Blue_Book_Special_Report_No._14]
2quiet8yThe study itself dismissed thousands of eyewitness reports. ~2200 of the 3600 cases were outright solved. Dismissing eyewitness testimony wouldn't be so easy if eyewitness testimony weren't so comically unreliable. In the absence of physical evidence, it seems plainly silly to mutate "we couldn't trace this vague claim back to any FFA scheduled flight plans" into "high tech alien visitation." Assuming these people actually saw something, how can we make the leap to aliens? The interpretive jump from [some kind of light] to Alien Space Ship seems no different to me than deciding that a toast burn/water stain/oddly shaped tree knot is an apparition of Jesus Christ Our Lord and Savior. Neither conclusion would be proposed in absence of a preconceived bias toward it. I don't know; therefor Aliens.
0[anonymous]8ySeriously, is this the level of discussion: "the study discarded some eye witness reports, so I am fully justified in discarding the rest as well" ? "Assuming these people actually saw something, how can we make the leap to aliens? " As discussed elsewhere you are completely right. In the cases where we just see something on the sky that cannot be explained by anything we know, we cannot just jump to the aliens conclusion. But it leaves a massive phenomena to be explained, which should spark massive scientific investigation. Also this resolution doesn't account for the cases where little grey men actually emerge from these objects. They may not be from another planet, but alternative hypothesis's aren't really a dime a dozen here.
5quiet8yThe trend is for these mysteries to have boring solutions. Eyewitness testimony is known to be unreliable. There is no physical evidence. All that is left is a very small amount of people who claim to have seen something that they don't understand; color me unimpressed. I would imagine that the number of eyes and instruments aimed upwards would be at an all-time high already. Satellites are recording images of our planet from every angle. What, exactly, should scientists be studying? What evidence is there to pour over? How can new evidence be gathered? Have little grey men actually emerged from objects? Or is that just what people have claimed? There is a significant difference between those two statements and your choice of phrasing indicates an unjustified bias. A personal note: I suffer from chronic sleep paralysis and regularly have wild, terrifying hypnagogic hallucinations, many of which take on the form of the standard alien abduction scenario. An unintended consequence of my childhood obsession with The X-Files, no doubt. I have seen demons, elder gods, and greys with my own wide open eyes and I believe in none of them. When confronted with an unknown, it is possible for the mind to run amok with myth and fantasy. We're all susceptible to this and cannot be cautious enough about what we accept as truth.
-1[anonymous]8y"The trend is for these mysteries to have boring solutions. Eyewitness testimony is known to be unreliable." As discussed elsewhere in this thread this is not the same as saying they all are 100% fallible. By far, as stated in the Project Blue Book Special Report No. 14. "There is no physical evidence. All that is left is a very small amount of people who claim to have seen something that they don't understand;" Where did you get these statements from? Thin air? Any references on it? You obviously hasn't looked into this. "Have little grey men actually emerged from objects? Or is that just what people have claimed? There is a significant difference between those two statements and your choice of phrasing indicates an unjustified bias." As said in the original post my belief is utterly uninteresting - I could be lunatic. What matters is the arguments and references I can come up with.
1quiet8yNo disagreement here. Where we seem to disagree is whether or not the 22% remaining unknowns qualify as positive evidence towards anything. I assumed that if there was physical evidence then you would have used it to bolster your argument. Is there any? I read the wiki article you linked to. I came out believing that the study concluded that 22% of cases could not be explained. This, apparently, means a lot more to you than it does to me. No big deal.
0thomblake8yTo quote, prefix a line with a greater-than sign >. For more tips, click the 'Show help' button on the bottom-right of the edit box.
-1mwengler8yIs drethelin an alien trying to throw us off the scent? (it was worth the negative karma so go ahead.)
-1mwengler8yAre you not familiar with the typical epistemological process of discovering something and then investigating it further?
1mwengler8yThat is actually NOT what you already know unless you have assumed the conclusion, that there are not currently aliens on earth. What we know right now is we see what we see, and what we see is what we see whether there are aliens here or not.
0mwengler8yHistorically, humans from one group have succeeded in infiltrating humans of other groups,and all without superior intelligence or technology beyond what we all know about (or could if we read the internet). I think what we already know is that if there are aliens, they are either relatively smart with relatively good tech, or they are biologically similar enough to us to pass the relative cursory inspections that most of us give most of the rest of us while going about our normal lives. Or both.

Ascribing a prior probability of zero for these claims is like saying we should ignore all previous evidence and start over from scratch. But this is inappropriate; there is a long history of "aliens on Earth"-type claims that have been made over the years, and they've all been shown to be insufficient. So when a new "aliens on Earth"-type claim arises (like your linked video, which I have not yet clicked on), it is entirely appropriate to assign it a low prior.

6[anonymous]8yIt's actually worse than that. Assigning a prior of 0 means that no amount of evidence can allow for an update to a non-zero posterior probability.
2aaronde8yWait, what? Bayesians never assign 0 probability to anything, because it means the probability will always remain 0 regardless of future updates. And "prior probability", by definition, means that we throw out all previous evidence.
3[anonymous]8yYes. This name for this is Cromwell's rule. Not quite. The prior probability is the probability of the hypothesis and the background information, independent from the evidence we are updating on. This includes previous evidence. We usually write the "prior probability" as P(H), but it should really be written as P(H.B), where "H" is hypothesis and "B" is background information. For example, let's say I am asking you to update your belief that Julius Caesar existed given a recently discovered, apparently first-hand account of Caesar's crossing the Rubicon. Your prior probability should NOT exclude all previous evidence on whether Caesar actually existed - e.g. official Roman documents and coins with his face. Ideally, your prior probability should be your posterior probability from your most recent update.
0aaronde8yRight. What I want to do is calculate the probability that a random conscious entity would find itself living in a world where someone satisfying the definition of Julius Caesar had existed. And then calculate the conditional probability given the evidence, which is everything I've ever observed about the world including the newly discovered account. Obviously that's not what you do in real life, but the point remains that everything after the original prior (based on Kolmogorov complexity or something) is just conditioning. If we're going to talk about how and why we should formulate priors, rather than what Bayes' rule says, this is what we're interested in.
0[anonymous]8yBut that's not what I'm talking about. I was specifically responding to your claim that: So far as I can tell, that's not part of the accepted definition. For example, Jaynes' work [http://bayes.wustl.edu/etj/articles/prior.pdf] on prior probabilities explicitly invokes prior information: I don't mean to come off as a dick for nit-picking about definitions. But rigorous mathematical definitions are really important, especially if you are claiming to argue something is true by definition - and you were.
3aaronde8yYes, I was wrong. I was explaining why I got so focused on the blank-slate version of the prior.
1[anonymous]8yOh, gotcha.
[-][anonymous]8y -4

I'd think we'd all spend our time better reviewing evidence, rather than just discussing UFOs a priori. After all, a priori speculation can't really determine the presence of aliens.

Here's another database of sightings: http://www.nuforc.org/webreports.html

and here are the editors picks from it: http://www.nuforc.org/CBBest.html

Judge from these instead of from speculation ( this principle has a name: http://en.wikipedia.org/wiki/Empiricism ).

[+][anonymous]8y -7