Are UFOs Actually Aliens? Bayes’ Theorem Applied
Many photos released by the US military regarding unidentified flying object (UFO) sightings are blurry and vague, causing people to wonder: are these UFOs actually aliens? In the article, “UFOs: how to calculate the odds that an alien spaceship has been spotted,” Bayes rule is applied to assess the likelihood that these ‘UFOs’ could instead be extraterrestrial life.
Mathematically, we can express this likelihood as follows: the probability that the UFO is an alien given evidence is equal to the probability there is evidence given the UFO is an alien times the probability there are aliens divided by the probability of evidence. In other words, Pr(UFO is an alien|evidence) = [Pr(evidence|UFO is an alien)Pr(aliens exist)] / Pr(evidence). Since what we truly care about is if the evidence tells us whether we should believe in aliens compared to not believing in them, we can divide the equation by the chance the UFOs aren’t aliens: [Pr(UFO is an alien|evidence)/Pr(UFO isn’t an alien|evidence)] = [(Pr(evidence|UFO is an alien)/ Pr(evidence|UFO isn’t an alien]*[Pr(aliens are around)/Pr(aliens aren’t around)]. On the right side of the equation, the first bracket tells us how specific the evidence is for aliens versus no aliens while the second bracket tells us how likely we think aliens are.
As I was reading this article and before I jumped into Bayes’ theorem, I assumed this probably isn’t very likely. After all, people are irrational, and jump to conclusions all the time – for all we know, they could have seen ghosts or angels. But then again, these were my loose thoughts and no real math was applied. But, after the math, my thoughts seem more or less confirmed. For the first factor I discussed, the author thinks the factor wouldn’t be very different from 1 – and I agree. After all, a blurry image of something in the sky could be an alien, but it could also be a bunch of other things. The second factor, also seems unlikely – while there is strong evidence that intelligent life probably exists, based on previous research, there seems to be a little to no likelihood that that intelligent life would actually reach Earth.
https://theconversation.com/ufos-how-to-calculate-the-odds-that-an-alien-spaceship-has-been-spotted-162269