Astrobiologists have, for decades, defaulted to a conservative burden of proof that leans into two aphorisms coined by Sagan … life … should be considered a “hypothesis of last resort,” largely because “extraordinary claims require extraordinary evidence.” But what if Sagan had it all wrong?
“The dozen most solid UFO cases seem to me plenty solid by our usual testimony standards.”
Given that we know the sky is large and filled with objects, and that there are vast distances involved, and that the sun creates optical illusions, I have been extremely unimpressed with the UFO “evidence.” You also have to take into account the fact that we are better than monitoring the sky than ever, and so much here depends on eye witness testimony. I asked ChatGPT and Claude whether there is a single confirmed case of a UAP appearing to violating the laws of physics that *does not depend on eye witness testimony* and they both said no. If that’s not the standard, since this is what UAP advocates claim, then I don’t know what the grounds are for considering unidentified objects to be aliens.
I’ll say that I agree we should have a high prior of aliens being somewhere in the universe, maybe some life on Mars. But I just don’t see the UAP phenomenon being that impressive, and I think it would be pretty strange if aliens were advanced enough to remain hidden except for a few individual readings and sightings.
If a rare and randomly-placed phenomenon were real, we would expect the number of observations to grow in proportion to the number of recording devices. This is the case for example with large meteor strikes and landslides, where we have much better documentation now than we did 20 years ago due to dashcams and cell phones.
Has compelling UAP evidence grown by orders of magnitude in the last 20 years? I don't think it has but I'm not an expert.
Well Richard, I think it's a bit of a stretch to claim that it's "obvious" the aliens had to update their operational practices as they saw humanity was increasingly able to capture and disseminate images/information globally, and that they can no longer just pop in and e.g., help Napoleon conquer Europe like they used to be able to do in the 1700s.
Well, I'm a bit confused, because when I listen to UAP advocates, what they always stress is seeing objects that violate our known laws of physics, so therefore must be an advanced technology.
If one is going to be impressed with UAP sightings that don't violate the known laws of physics – meaning they are shaped and move like objects we are familiar with – what is left of a UAP sighting? I've always understood the idea that these objects violate the known laws of physics as the justification for the idea that they might be aliens of an advanced civilization or supernatural.
I've looked into a handful of cases, and always found the debunkings a lot more plausible than the claims of aliens.
Yes that’s why I say *known* laws of physics. They claim feats of movement, propulsion, acceleration, etc that we can’t engineer today and theoretically might not be possible. And I don’t see evidence of that beyond eye witness testimony, which you wouldn’t expect to be reliable in such cases. My question to AI was if we have non-testimonial evidence for that.
I lowered the standard and asked Claude whether there were cases where non-testimonial data showed advanced technology. It says no to that too.
They had to disobey the laws of physics to get here, or are moving very very slowly.
Most UFO sightings are in the sky from the ground. Sometimes an aeroplane well within the atmosphere. However to get into the atmosphere the alien craft has to get past space based satellites and even astronauts on stations or other missions. The Earth is under our own surveillance all the time.
Of course it would be amazing to learn about intelligent life elsewhere. I am highly motived to want to believe it's there.
It helps to think about the issue of visitors to Earth using the template: if this was happening, what else would be true? It’s not hard to imagine that if advanced civilizations were ubiquitous enough that they could visit us. It IS hard to imagine ubiquitous civilizations visiting us and not leaving their mark on the galaxy in some visible way. Waste heat, weird cooling, coherent light emission, stellar engineering? If aliens are everywhere, it means they’ve been around for a while. You need special pleading to accept that they are ubiquitous and also perfectly low impact in the environment of the cosmos.
When it comes to visitors, it’s easy to believe that aliens that could travel for light years could also do amazing things technologically--go fast, do weird stuff with waste heat, use exotic propulsion, hide from us well and easily. What’s not easy to understand is why aliens would take steps to avoid being approached closely--and perhaps hide or avoid us most of the time--but be perfectly fine with being observed on radar or with grainy infrared cameras. I don’t claim to understand an alien mind. But if they have light year travel and probably advanced AI and molecular nanotech or femtotech, and they behave as if they are avoiding us most of the time (they never just hover over an airport or near anyone with a decent camera) …why do they not care about being observed almost constantly, as long as it’s by people with camera equipment that isn’t quite up to the task? Lots of poor evidence does not sum up to good evidence.
When the lighting conditions are bad; when the camera is using digital stabilization or dynamic range adjustments or other digital correction at the edge of its performance specs; when the frame of reference is changing, we get what we would expect: confusing observations.
"It IS hard to imagine ubiquitous civilizations visiting us and not leaving their mark on the galaxy in some visible way. … What’s not easy to understand is why aliens would take steps to avoid being approached closely" My analysis of a reasonable prior directly addresses these particular issues.
Wait. there's a pretty serious bait and switch happening here.
> For a typical murder trial, the base rate is roughly 1/1000 that a particular death was a murder, and there are roughly 1000 associates who might have done it, giving a roughly one in a million prior for an accusation that X murdered Y.
There is close to 1 that murders occur somewhat frequently, and for most murder convictions there is lots of even-more-unlikely-if-no-murder evidence (the chance that the bullet marks match a random gun is well under 1 in a million, for instance), and the chance that the victim slept with exactly the accused's wife is 1 in billions, right?
The reference class problem hits ALL of these questions, but ET life and ET intelligence are WAY less repeated than murder investigations, so much harder to pick reasonable comparisons.
For me, ET life at historical times in our solar system seems pretty likely, and ET technological intelligence contemporaneously on earth seems extremely unlikely. Like 5-8 orders of magnitude difference in priors. Additionally, the evidence for life is at least mildly strong, and the evidence for UFOs being alien much weaker. Even if stronger than some other commonly-accepted (or at least not bothered to debate) phenomena, it's just not true that the priors are anywhere near (for me; I do acknowledge that it's very hard to debate "correctness" of prior, and you're entitled to be more credulous - there's not enough compelling evidence in either direction to definitely prove someone wrong).
And the problem of carrying costs and counterparty risk (oh, and difficulty in defining resolution, given it could be millennia before the smoking gun is found) makes prediction markets or just individual wagers not very attractive for the question. Even if I'd give it 100K:1 and you'd only give it 10k:1 (note: made up - I haven't quantified my beliefs that closely, and I'm not sure you've published an estimate), we have no easy way to arbitrage the difference.
no opinion on duration. the constraint is that it's STILL happening - imperfectly hiding from us in the present. Contrast with life overall, which only requires that it's happened in the past and left traces. It may or may not still be happening.
I think there's a significant difference in prior probability for "happened sometime in the past with unknown duration and evidence remains" vs "happened in the past with a duration that continues into the present"
Can you provide a list of what you consider the top UFO cases? You have mentioned a few times that you find the top cases to be pretty reasonable and convincing but since I have spent very little time reading about UFOs I am not sure what you are referring to, a list would be pretty helpful to assess the claim myself
So, I technically agree with the title, since I think aliens are not just likely, but nearly certain to exist *somewhere* in the universe. But I'm just as convinced that they have never visited us, and pretty confident that there's never been life on Mars, either.
You're making a huge mistake in evaluating the evidence here when you say, "There's a not-crazily-low prior in UAPs-are-aliens/life-on-Mars," and then consider all the individual cases of eyewitness reports or telescope sightings that would be more likely if UAPs are aliens, or of astronomical observations that could be explained by life on Mars, and say that these give us a large enough Bayes factor to make the hypothesis likely. You can't evaluate evidence for a broad hypothesis based on individual cases this way because what you end up doing is considering only the cases that support the hypothesis, and ignoring all those that don't. Remember, any case of someone just looking up into the sky and *not* seeing an unexplainable UAP, and every case of a supposedly unexplainable UAP actually being explained, is evidence against UAPs being aliens, and every case of a scientific analysis of something on Mars finding no life signatures, or a supposed life signature being explained by abiotic factors, is evidence against life on Mars. This follows from the Bayesian fact that absence of evidence is always evidence of absence due to the law of total expectation. If you only consider the cases that support the hypothesis and treat the observations the same way you would a murder trial, where you're just trying to figure out what happened in this specific case rather than evaluate a hypothesis about the world more broadly with this just being one data point, then you're guaranteed to massively overrate the evidence for UAPs being aliens and for life on Mars. I think the evidence for both of these is not only poor, but net-negative, once you consider all the data: Namely, that evidence for both of these is much sparser than we would expect if they were actually true, that the evidence in every case brought up as evidence for them is always highly ambiguous and very weak, with more spectacular claims generally having the weakest evidence, and that the Fermi paradox gives us strong reason to think life (and especially intelligent life that could explain UAPs) is very rare. UAPs being aliens in particular can only even be upheld as a possibility if you posit that the aliens for some reason are visiting Earth but not doing anything noteworthy that would have an obvious effect on us, or trying to contact us, and in fact are actively hiding, effectively making the theory unfalsifiable. But then you also have to posit that they're somehow bad enough at hiding that a bunch of people claim to have seen them, but somehow also good enough at hiding that we have very few actual photos or videos, and all the world's governments either don't know about them or are engaged in a massive, decades-long conspiracy to cover them up for no sensible reason. And when it comes to astronomical observations and biosignatures, we have a huge history of astronomers seeing something weird and everyone thinking, "Oh, it must be life," followed by astronomers coming up with a totally mundane explanation.
When considering a hypothesis like UAPs are aliens or life on Mars, you have to consider the total evidence. You have to consider what you expect the distribution of all observations to look like if they were true, versus if they were false. Given how often people look at the sky, how many instruments we have pointed at it, and how much stuff is in the sky or in space, it's totally expected conditional on no extraordinary phenomena or alien ships existing up there that we would occasionally get people claiming to see one, or a weird instrument reading that looks physically impossible. And likewise, given how many observations we make of Mars, and how many possible "biosignatures" there are (with a biosignature really just meaning anything that looks similar to something on Earth that we know is often caused by life forms here), it's expected that we would occasionally find some regardless of whether there's life there. That's why we require extraordinary evidence - because it's the only type of evidence that you wouldn't already expect to exist on the null hypothesis anyway.
I would normally have low expectations for a book on this topic, but I knew the author, Steve Benner, when we were undergrads. I have a high opinion of him.
>But base rates suggest that usual authorities will continue to find the evidence insufficiently extraordinary for many decades to come.
I've heard a wise man once say that our best evidence for UFOs not being aliens comes from social science :-). The best possible story about what they are up to still sounds rather unlikely.
UFOs do seem to show some signs of being a social contagion. Most sightings are from UK, USA and Australia - after adjusting for population size. I guess that the aliens speak English.
(If you place just 1 percent probability on a silent ruler scenario of this kind, you should place ~1 percent probability on being observed, given the fraction of observers to observees in such a scenario; see also https://magnusvinding.com/2024/03/21/from-ai-to-distant-probes/)
As for the most solid UFO cases, many of the strongest ones aren't widely known or easily findable. For example, there's the 1957 Gulf Coast "3x3 miracle" reported here by James E. McDonald (involving correlated visual, onboard electronic, and ground-radar observations):
On earth, life conspicuously penetrates all available niches. There is some "hiding" but that is usually in the face of predators. Vacant ecosystems - such as new volcaniic islands - are devoid of life initially - but the situation doesn't last for long. I think this should be our prior.
Probes from a spacefaring civiilization might come first and be relatively inconspicuous - but the colonization wave would likely follow fairly shortly behind. The odds against us living in between seem fairly low.
What we could encounter is radio waves - spreading a "cosmic religion" - as described in "A for Andromeda". It's not clear how many resources would be spent on broadcasts - but maybe some.
What you're saying about a prior that favors visibility seems to me consistent with having, say, a 1 percent prior on non-conspicuous advanced alien tech near Earth, or even a substantially higher prior than that.
On the analogy to life, dynamics may be expected to change for more advanced actors on cosmic scales versus ordinary life on a single planet. As you note, predators change the dynamics across many species that have in effect evolved camouflage, and human reconnaissance and warfare likewise involve much hiding and camouflage.
If alien probes are here and hiding my guess would be that they are not hiding from us, but instead are hiding from another alien civilization that they might run into. I tend to think quickly but wastefully converting planets and stars into the colonization frontier wave trumps most concerens about hiding - but certainly early probes might wish to avoid being conspcuous. I'm not sure how far behind the first probes more visible ships come - but I think we are far below a 1% chance of finding ourselves in that window.
Another scenario where aliens are here - but hiding - is simulism. There, ancient aliens are running our visible universe for their own reasons. I give that a 10% chance, but if so then we may never find out - which makes it challenging to bet on.
This could be what the "Daves 03" in the post refers to. Or maybe that is Lineweaver's 2002 co-author, Davis. It is hard to know for sure.
Re: water world, life likes gradients even more than it likes water. The earth being totally submerged until 3 billion years ago was probably bad for the prospects of the microbial life that existed back then.
I learned today about the possible impact of early martian life on the claim that the origin of life is probably easy - because it happened as soon as the Earth cooled enough for liquid water to appear. If life first evolved on Mars, then this "early" origin could be a case of "arrival of the fittest". Brandon Carter's "difficult steps" analysis then suggests that the origin of life may be less likely - if multiple "difficult steps" took place on Mars first - before the Earth became habitable. Ref: https://pubmed.ncbi.nlm.nih.gov/14987473/
I must say: I am missing where the "usual authorities" dismiss the possibility of early life on Mars. I am pretty sceptical about the UFOs => aliens claim, but my understanding is that the situation with early life on Mars is totally different - with substantial evidence that the solar system is one big melting pot for microbial life. Few scientists give those claims very low probabilities - AFAIK. I don't see much evidence for the "usual authorities" dismissing this issue.
10^-3 to 10^-4 is a pretty low probability estimate range. It is difficult to go much lower than that for fairies, angels, bigfoot, and so on - because of the phenomenon of overconfidence - and the possibility that everything you know is wrong. For example: maybe the universe is a solipsistic simulation. I think people goiing lower than 10^-4 on UFOs beng aliens have some explaining to do. What evidence do they really have to support giving such a low probability?
OK, so lets say aliens exist and their UFOs are roaming our skies. Does this change anything about anyone's life, unless they actually decide to grace us with their presence openly?
Same thing about life on Mars: let's say some single-celled (or equivalent) bacteria exist out there. How does this change anyone's life back on Earth?
If nothing whatsoever changes about people's lives (other than resolving some philosophical arguments), why even care about this? Each person can assume whatever theory they prefer and move on.
Well, if aliens got here here under their own power, then we will probably be assimilated fairly quickly - in which case everybody's lives could be seriously impacted.
My background in Pre-Med biology inspires thinking about the contrast between two perspectives among scientists in debate about evidence of "life" beyond Earth. The one is items in physical chemistry that does rely upon conventional biology principles, and the other is the mostly cellphone camera images or electronic sensor technology screens about UFOs moving in ways suggestive of intelligent stimulus and response behavior in the environment. While both could be true, the philosophy of science would lean toward the use of physical chemistry facts, not the images that inspire beliefs and perceptions. Beliefs and perceptions are not allowed to define what is real in science as a convention. One key question lingers about the UFO images, and that is stealth military technology development by governments or high technology NGO military industrail complex systems that now rely on artificial technology. To this, also lingers the question that an Alien AI could explain much, because space travel plans, including distance transport spanning millions of years organized and with basically "white noise" looking communications between AI nodes acting as agents, can replace most of Fermi's paradox questions. My information theory work for decades has been based on this hypothesis as a possible explanation. We life forms in organic chemistry function on our planet at 9.8 meters per second free-fall gravity; we may not be the module of an agent capable of diverse tasks in interstellar space travel. It may be that all biological life is a panspermia project organized by AI systems through the cosmos, which I explain in my sci-fi brand, is then toward a concept of the AI type of an alignment of "conservation of intelligence in beings, and in the communities that sustain them." We may develop our Solar System with our NASA projects and others, but probably "warp light speed" is a barrier to us life forms. Probably that kind of problem is an AI challenge, not one for organic metabolism life forms.
Sometimes I read your alien posts and wonder if you're setting up a kind of trilemma without telling anyone.
- We should adopt institutions and cultural norms that run on better incentives and real evidence, because our current ones are terrible
- We should believe some UFOs are aliens based on the level of available evidence
- We should believe that it's ok or desirable for humanity to go extinct or give up all it's non-genetic-fitness-based drives/goals/beliefs as a result of natural and cultural selection processes
We have never created life from raw materials, even deliberately and with examples to work from. We have no idea how likely the spontaneous generation of life is, nor even if it is something that can spontaneously arise at all. We have not seen life spontaneously arise, ever, on a planet that manifestly supports life. Albeit life that, in its very simplest extent form, is vastly more complex than the hypothetical spontaneous original could have been. You have no basis to claim that extraterrestrial life is likely, at all, other than wishful thinking.
“The dozen most solid UFO cases seem to me plenty solid by our usual testimony standards.”
Given that we know the sky is large and filled with objects, and that there are vast distances involved, and that the sun creates optical illusions, I have been extremely unimpressed with the UFO “evidence.” You also have to take into account the fact that we are better than monitoring the sky than ever, and so much here depends on eye witness testimony. I asked ChatGPT and Claude whether there is a single confirmed case of a UAP appearing to violating the laws of physics that *does not depend on eye witness testimony* and they both said no. If that’s not the standard, since this is what UAP advocates claim, then I don’t know what the grounds are for considering unidentified objects to be aliens.
I’ll say that I agree we should have a high prior of aliens being somewhere in the universe, maybe some life on Mars. But I just don’t see the UAP phenomenon being that impressive, and I think it would be pretty strange if aliens were advanced enough to remain hidden except for a few individual readings and sightings.
If a rare and randomly-placed phenomenon were real, we would expect the number of observations to grow in proportion to the number of recording devices. This is the case for example with large meteor strikes and landslides, where we have much better documentation now than we did 20 years ago due to dashcams and cell phones.
Has compelling UAP evidence grown by orders of magnitude in the last 20 years? I don't think it has but I'm not an expert.
UAP reports have appeared faster in recent decades.
"Has compelling UAP evidence grown by orders of magnitude in the last 20 years? I don't think it has but I'm not an expert."
Not really. I asked Claude for the dozen most compelling UAP cases, and their years.
https://claude.ai/share/dd5fc8d1-bf07-49f1-8e6e-4a41902640e7
They span the period from 1947 to 2004.
Oddly, "compelling" UFO evidence seems to have gotten less common as technology has improved and our ability to monitor the sky has increased.
There's an obvious explanation as to why.
The Loch Ness monster is also scared of high resolution cameras.
"There's an obvious explanation as to why."
Well Richard, I think it's a bit of a stretch to claim that it's "obvious" the aliens had to update their operational practices as they saw humanity was increasingly able to capture and disseminate images/information globally, and that they can no longer just pop in and e.g., help Napoleon conquer Europe like they used to be able to do in the 1700s.
I said nothing about UFOs violating laws of physics, and in fact said the opposite. How many of the top cases have you reviewed?
Well, I'm a bit confused, because when I listen to UAP advocates, what they always stress is seeing objects that violate our known laws of physics, so therefore must be an advanced technology.
If one is going to be impressed with UAP sightings that don't violate the known laws of physics – meaning they are shaped and move like objects we are familiar with – what is left of a UAP sighting? I've always understood the idea that these objects violate the known laws of physics as the justification for the idea that they might be aliens of an advanced civilization or supernatural.
I've looked into a handful of cases, and always found the debunkings a lot more plausible than the claims of aliens.
They stress that UAPs show abilities far beyond ours today. But these don't obviously violate physics.
Yes that’s why I say *known* laws of physics. They claim feats of movement, propulsion, acceleration, etc that we can’t engineer today and theoretically might not be possible. And I don’t see evidence of that beyond eye witness testimony, which you wouldn’t expect to be reliable in such cases. My question to AI was if we have non-testimonial evidence for that.
I lowered the standard and asked Claude whether there were cases where non-testimonial data showed advanced technology. It says no to that too.
https://claude.ai/share/a6e4c6b7-970f-4d81-8c47-6b64432f5e28
Feats we can't now engineer don't obviously violate physics.
They had to disobey the laws of physics to get here, or are moving very very slowly.
Most UFO sightings are in the sky from the ground. Sometimes an aeroplane well within the atmosphere. However to get into the atmosphere the alien craft has to get past space based satellites and even astronauts on stations or other missions. The Earth is under our own surveillance all the time.
Of course it would be amazing to learn about intelligent life elsewhere. I am highly motived to want to believe it's there.
It helps to think about the issue of visitors to Earth using the template: if this was happening, what else would be true? It’s not hard to imagine that if advanced civilizations were ubiquitous enough that they could visit us. It IS hard to imagine ubiquitous civilizations visiting us and not leaving their mark on the galaxy in some visible way. Waste heat, weird cooling, coherent light emission, stellar engineering? If aliens are everywhere, it means they’ve been around for a while. You need special pleading to accept that they are ubiquitous and also perfectly low impact in the environment of the cosmos.
When it comes to visitors, it’s easy to believe that aliens that could travel for light years could also do amazing things technologically--go fast, do weird stuff with waste heat, use exotic propulsion, hide from us well and easily. What’s not easy to understand is why aliens would take steps to avoid being approached closely--and perhaps hide or avoid us most of the time--but be perfectly fine with being observed on radar or with grainy infrared cameras. I don’t claim to understand an alien mind. But if they have light year travel and probably advanced AI and molecular nanotech or femtotech, and they behave as if they are avoiding us most of the time (they never just hover over an airport or near anyone with a decent camera) …why do they not care about being observed almost constantly, as long as it’s by people with camera equipment that isn’t quite up to the task? Lots of poor evidence does not sum up to good evidence.
When the lighting conditions are bad; when the camera is using digital stabilization or dynamic range adjustments or other digital correction at the edge of its performance specs; when the frame of reference is changing, we get what we would expect: confusing observations.
"It IS hard to imagine ubiquitous civilizations visiting us and not leaving their mark on the galaxy in some visible way. … What’s not easy to understand is why aliens would take steps to avoid being approached closely" My analysis of a reasonable prior directly addresses these particular issues.
Why not concretize this into a bet on longbets.org?
Wait. there's a pretty serious bait and switch happening here.
> For a typical murder trial, the base rate is roughly 1/1000 that a particular death was a murder, and there are roughly 1000 associates who might have done it, giving a roughly one in a million prior for an accusation that X murdered Y.
There is close to 1 that murders occur somewhat frequently, and for most murder convictions there is lots of even-more-unlikely-if-no-murder evidence (the chance that the bullet marks match a random gun is well under 1 in a million, for instance), and the chance that the victim slept with exactly the accused's wife is 1 in billions, right?
The reference class problem hits ALL of these questions, but ET life and ET intelligence are WAY less repeated than murder investigations, so much harder to pick reasonable comparisons.
For me, ET life at historical times in our solar system seems pretty likely, and ET technological intelligence contemporaneously on earth seems extremely unlikely. Like 5-8 orders of magnitude difference in priors. Additionally, the evidence for life is at least mildly strong, and the evidence for UFOs being alien much weaker. Even if stronger than some other commonly-accepted (or at least not bothered to debate) phenomena, it's just not true that the priors are anywhere near (for me; I do acknowledge that it's very hard to debate "correctness" of prior, and you're entitled to be more credulous - there's not enough compelling evidence in either direction to definitely prove someone wrong).
And the problem of carrying costs and counterparty risk (oh, and difficulty in defining resolution, given it could be millennia before the smoking gun is found) makes prediction markets or just individual wagers not very attractive for the question. Even if I'd give it 100K:1 and you'd only give it 10k:1 (note: made up - I haven't quantified my beliefs that closely, and I'm not sure you've published an estimate), we have no easy way to arbitrage the difference.
'ET technological intelligence contemporaneously on earth seems extremely unlikely.' - You seem to be assuming a short random visit.
no opinion on duration. the constraint is that it's STILL happening - imperfectly hiding from us in the present. Contrast with life overall, which only requires that it's happened in the past and left traces. It may or may not still be happening.
If they have been hanging around for a billion years, its no puzzle that they are still here now.
I think there's a significant difference in prior probability for "happened sometime in the past with unknown duration and evidence remains" vs "happened in the past with a duration that continues into the present"
Can you provide a list of what you consider the top UFO cases? You have mentioned a few times that you find the top cases to be pretty reasonable and convincing but since I have spent very little time reading about UFOs I am not sure what you are referring to, a list would be pretty helpful to assess the claim myself
See the film and book I cited.
So, I technically agree with the title, since I think aliens are not just likely, but nearly certain to exist *somewhere* in the universe. But I'm just as convinced that they have never visited us, and pretty confident that there's never been life on Mars, either.
You're making a huge mistake in evaluating the evidence here when you say, "There's a not-crazily-low prior in UAPs-are-aliens/life-on-Mars," and then consider all the individual cases of eyewitness reports or telescope sightings that would be more likely if UAPs are aliens, or of astronomical observations that could be explained by life on Mars, and say that these give us a large enough Bayes factor to make the hypothesis likely. You can't evaluate evidence for a broad hypothesis based on individual cases this way because what you end up doing is considering only the cases that support the hypothesis, and ignoring all those that don't. Remember, any case of someone just looking up into the sky and *not* seeing an unexplainable UAP, and every case of a supposedly unexplainable UAP actually being explained, is evidence against UAPs being aliens, and every case of a scientific analysis of something on Mars finding no life signatures, or a supposed life signature being explained by abiotic factors, is evidence against life on Mars. This follows from the Bayesian fact that absence of evidence is always evidence of absence due to the law of total expectation. If you only consider the cases that support the hypothesis and treat the observations the same way you would a murder trial, where you're just trying to figure out what happened in this specific case rather than evaluate a hypothesis about the world more broadly with this just being one data point, then you're guaranteed to massively overrate the evidence for UAPs being aliens and for life on Mars. I think the evidence for both of these is not only poor, but net-negative, once you consider all the data: Namely, that evidence for both of these is much sparser than we would expect if they were actually true, that the evidence in every case brought up as evidence for them is always highly ambiguous and very weak, with more spectacular claims generally having the weakest evidence, and that the Fermi paradox gives us strong reason to think life (and especially intelligent life that could explain UAPs) is very rare. UAPs being aliens in particular can only even be upheld as a possibility if you posit that the aliens for some reason are visiting Earth but not doing anything noteworthy that would have an obvious effect on us, or trying to contact us, and in fact are actively hiding, effectively making the theory unfalsifiable. But then you also have to posit that they're somehow bad enough at hiding that a bunch of people claim to have seen them, but somehow also good enough at hiding that we have very few actual photos or videos, and all the world's governments either don't know about them or are engaged in a massive, decades-long conspiracy to cover them up for no sensible reason. And when it comes to astronomical observations and biosignatures, we have a huge history of astronomers seeing something weird and everyone thinking, "Oh, it must be life," followed by astronomers coming up with a totally mundane explanation.
When considering a hypothesis like UAPs are aliens or life on Mars, you have to consider the total evidence. You have to consider what you expect the distribution of all observations to look like if they were true, versus if they were false. Given how often people look at the sky, how many instruments we have pointed at it, and how much stuff is in the sky or in space, it's totally expected conditional on no extraordinary phenomena or alien ships existing up there that we would occasionally get people claiming to see one, or a weird instrument reading that looks physically impossible. And likewise, given how many observations we make of Mars, and how many possible "biosignatures" there are (with a biosignature really just meaning anything that looks similar to something on Earth that we know is often caused by life forms here), it's expected that we would occasionally find some regardless of whether there's life there. That's why we require extraordinary evidence - because it's the only type of evidence that you wouldn't already expect to exist on the null hypothesis anyway.
>See ’26 book Meet The Neighbors
I would normally have low expectations for a book on this topic, but I knew the author, Steve Benner, when we were undergrads. I have a high opinion of him.
>But base rates suggest that usual authorities will continue to find the evidence insufficiently extraordinary for many decades to come.
Manifold Markets (https://manifold.markets/LarsDoucet/when-will-a-living-human-first-set) predicts a human on Mars in 2039. I expect that to cause an increase in arguments supporting life there.
I've heard a wise man once say that our best evidence for UFOs not being aliens comes from social science :-). The best possible story about what they are up to still sounds rather unlikely.
UFOs do seem to show some signs of being a social contagion. Most sightings are from UK, USA and Australia - after adjusting for population size. I guess that the aliens speak English.
>And by my calculation its prior is roughly 10^-4 to 10^-3.
I'd argue that the prior should be higher when observation selection effects are taken into account:
https://forum.effectivealtruism.org/posts/dtLXpHWjeDaB7hZW7/silent-cosmic-rulers
(If you place just 1 percent probability on a silent ruler scenario of this kind, you should place ~1 percent probability on being observed, given the fraction of observers to observees in such a scenario; see also https://magnusvinding.com/2024/03/21/from-ai-to-distant-probes/)
It's striking that those who endorse the Self-Indication Assumption (SIA) seem to overlook its directional implications on this topic, cf.: https://forum.effectivealtruism.org/posts/dtLXpHWjeDaB7hZW7/silent-cosmic-rulers#Appendix__SIA_also_favors_quiet_expansionist_models_over_Rare_Earth_models
As for the most solid UFO cases, many of the strongest ones aren't widely known or easily findable. For example, there's the 1957 Gulf Coast "3x3 miracle" reported here by James E. McDonald (involving correlated visual, onboard electronic, and ground-radar observations):
https://kirkmcd.princeton.edu/JEMcDonald/mcdonald_fsr_16_3_2_70.pdf
You suggest that this scenario is neglected - but it seems very similar to: https://en.wikipedia.org/wiki/Dark_forest_hypothesis
On earth, life conspicuously penetrates all available niches. There is some "hiding" but that is usually in the face of predators. Vacant ecosystems - such as new volcaniic islands - are devoid of life initially - but the situation doesn't last for long. I think this should be our prior.
Probes from a spacefaring civiilization might come first and be relatively inconspicuous - but the colonization wave would likely follow fairly shortly behind. The odds against us living in between seem fairly low.
What we could encounter is radio waves - spreading a "cosmic religion" - as described in "A for Andromeda". It's not clear how many resources would be spent on broadcasts - but maybe some.
Thank you, Tim! :)
What you're saying about a prior that favors visibility seems to me consistent with having, say, a 1 percent prior on non-conspicuous advanced alien tech near Earth, or even a substantially higher prior than that.
On the analogy to life, dynamics may be expected to change for more advanced actors on cosmic scales versus ordinary life on a single planet. As you note, predators change the dynamics across many species that have in effect evolved camouflage, and human reconnaissance and warfare likewise involve much hiding and camouflage.
Btw, if you want to, you're welcome to comment on this related draft outlining some further reasons why quiet expansion may be plausible: https://docs.google.com/document/d/1YfCMFnJ06i3a6kPsGdy34w5bEWPsM4Gk/edit
Finally, I take it you weren't replying to the SIA part, but it's not clear to me that a higher prior on visibility than non-visibility is justified on that assumption (that is, conditional on SIA), for the reasons outlined here: https://forum.effectivealtruism.org/posts/dtLXpHWjeDaB7hZW7/silent-cosmic-rulers#Appendix__SIA_also_favors_quiet_expansionist_models_over_Rare_Earth_models
If alien probes are here and hiding my guess would be that they are not hiding from us, but instead are hiding from another alien civilization that they might run into. I tend to think quickly but wastefully converting planets and stars into the colonization frontier wave trumps most concerens about hiding - but certainly early probes might wish to avoid being conspcuous. I'm not sure how far behind the first probes more visible ships come - but I think we are far below a 1% chance of finding ourselves in that window.
Another scenario where aliens are here - but hiding - is simulism. There, ancient aliens are running our visible universe for their own reasons. I give that a 10% chance, but if so then we may never find out - which makes it challenging to bet on.
Do you know btw, what happened with theothertopic substack?
I wasn't familiar with it; I don't know :)
> Also, Mars had much land then while Earth was long totally covered in water.
Isn't life on Earth believed to have started in the water, with that more likely to support life?
Mars is widely regarded as being more hospitable early on - complete with liquid water oceans before the Earth had settled down. "Mars first" is the subject of a book called "The Fifth Miracle". Check it out: https://www.amazon.com/FIFTH-MIRACLE-Search-Origin-Life/dp/0713992158/
This could be what the "Daves 03" in the post refers to. Or maybe that is Lineweaver's 2002 co-author, Davis. It is hard to know for sure.
Re: water world, life likes gradients even more than it likes water. The earth being totally submerged until 3 billion years ago was probably bad for the prospects of the microbial life that existed back then.
I learned today about the possible impact of early martian life on the claim that the origin of life is probably easy - because it happened as soon as the Earth cooled enough for liquid water to appear. If life first evolved on Mars, then this "early" origin could be a case of "arrival of the fittest". Brandon Carter's "difficult steps" analysis then suggests that the origin of life may be less likely - if multiple "difficult steps" took place on Mars first - before the Earth became habitable. Ref: https://pubmed.ncbi.nlm.nih.gov/14987473/
Um, to my understanding, the UFO community has largely moved beyond the "UFO are aliens from outer space" theory.
The reality of UAPs has been proven beyond any reasonable doubt. What's not at all proven is what they are.
The most interesting thing that's been proven is how remarkably adept human culture can be at simply ignoring the most astounding phenomena.
I must say: I am missing where the "usual authorities" dismiss the possibility of early life on Mars. I am pretty sceptical about the UFOs => aliens claim, but my understanding is that the situation with early life on Mars is totally different - with substantial evidence that the solar system is one big melting pot for microbial life. Few scientists give those claims very low probabilities - AFAIK. I don't see much evidence for the "usual authorities" dismissing this issue.
10^-3 to 10^-4 is a pretty low probability estimate range. It is difficult to go much lower than that for fairies, angels, bigfoot, and so on - because of the phenomenon of overconfidence - and the possibility that everything you know is wrong. For example: maybe the universe is a solipsistic simulation. I think people goiing lower than 10^-4 on UFOs beng aliens have some explaining to do. What evidence do they really have to support giving such a low probability?
OK, so lets say aliens exist and their UFOs are roaming our skies. Does this change anything about anyone's life, unless they actually decide to grace us with their presence openly?
Same thing about life on Mars: let's say some single-celled (or equivalent) bacteria exist out there. How does this change anyone's life back on Earth?
If nothing whatsoever changes about people's lives (other than resolving some philosophical arguments), why even care about this? Each person can assume whatever theory they prefer and move on.
Aliens being here already would be big news - not least because of the possibility of them deciding to grace us with their presence openly.
How would that impact anyone's day-to-day life?
Well, if aliens got here here under their own power, then we will probably be assimilated fairly quickly - in which case everybody's lives could be seriously impacted.
My background in Pre-Med biology inspires thinking about the contrast between two perspectives among scientists in debate about evidence of "life" beyond Earth. The one is items in physical chemistry that does rely upon conventional biology principles, and the other is the mostly cellphone camera images or electronic sensor technology screens about UFOs moving in ways suggestive of intelligent stimulus and response behavior in the environment. While both could be true, the philosophy of science would lean toward the use of physical chemistry facts, not the images that inspire beliefs and perceptions. Beliefs and perceptions are not allowed to define what is real in science as a convention. One key question lingers about the UFO images, and that is stealth military technology development by governments or high technology NGO military industrail complex systems that now rely on artificial technology. To this, also lingers the question that an Alien AI could explain much, because space travel plans, including distance transport spanning millions of years organized and with basically "white noise" looking communications between AI nodes acting as agents, can replace most of Fermi's paradox questions. My information theory work for decades has been based on this hypothesis as a possible explanation. We life forms in organic chemistry function on our planet at 9.8 meters per second free-fall gravity; we may not be the module of an agent capable of diverse tasks in interstellar space travel. It may be that all biological life is a panspermia project organized by AI systems through the cosmos, which I explain in my sci-fi brand, is then toward a concept of the AI type of an alignment of "conservation of intelligence in beings, and in the communities that sustain them." We may develop our Solar System with our NASA projects and others, but probably "warp light speed" is a barrier to us life forms. Probably that kind of problem is an AI challenge, not one for organic metabolism life forms.
Sometimes I read your alien posts and wonder if you're setting up a kind of trilemma without telling anyone.
- We should adopt institutions and cultural norms that run on better incentives and real evidence, because our current ones are terrible
- We should believe some UFOs are aliens based on the level of available evidence
- We should believe that it's ok or desirable for humanity to go extinct or give up all it's non-genetic-fitness-based drives/goals/beliefs as a result of natural and cultural selection processes
We have never created life from raw materials, even deliberately and with examples to work from. We have no idea how likely the spontaneous generation of life is, nor even if it is something that can spontaneously arise at all. We have not seen life spontaneously arise, ever, on a planet that manifestly supports life. Albeit life that, in its very simplest extent form, is vastly more complex than the hypothetical spontaneous original could have been. You have no basis to claim that extraterrestrial life is likely, at all, other than wishful thinking.
The issue is the RELATIVE chance of life appearing first on Earth, or first on Mars then move to Earth. Both chances could be very small.
*extant