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Comment by rossdavidh | Hacker News Reader

This whole idea of "dissolving" the Fermi paradox seems to be missing the point. Everyone knows that we have, in fact, not observed an alien civilization, so one of the factors in the Drake equation (or one we should have put in) is responsible. But, is it that there is very little chance of life evolving, or intelligence? Or is it that intelligence tends to be short lived? Or is it because long-lived intelligence uses methods of communication we cannot observe, and is responsible enough not to colonize all the good planets? The consequences for us are large, depending on which one of those it is. Merely saying "well it's not that surprising that one of those factors is tiny" is not really relevant to the question of, which factor is it that is tiny?

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> so one of the factors in the Drake equation (or one we should have put in) is responsible

The paper exactly explains why this is not the case. This is demonstrated using undergraduate level Bayesian probability.

This response is one of many when this work comes up on HN that would benefit from a basic understanding of multivariate probability.

The paper doesn't explain anything at all. If we are alone in the galaxy - it tells us absolutely nothing about why this is the case, and certainly not that it's unrelated to the factors in the Drake equation, as you seem to claim. On the contrary - the "explanation" it offers relies precisely on the assumption that the factors of the Drake equation are responsible. The only thing it says is that we should incorporate our uncertainty of them when trying to make an estimate. It might be interesting, but it adds absolutely nothing new about why we might be alone, other than "because some factors could be lower than we think". Duh.

This is addressed in the paper.

They estimate that the greatest uncertainties lie in the past terms of the Drake Equation, ergo that there is no evidence of some great threat to the continued advancement of human civilization.

Here would seem to be the limit of Bayesian analytics bridging the causal gap.

No, what the article is saying is that when you rely on distributions of outcomes from the Drake equation rather than averages, it's much more likely that you'll get tiny results.

You don't need extremely low values in the Drake equation to end up with nearly no aliens. It's actually kind of likely that we're (close to) alone, even without a crazy complicated theory to justify one of the values being nearly zero.

This is missing the point that many people do treat the Fermi Paradox like it's a real paradox - like there's some kind of fundamental universal principle that has to almost universally block out all life or all communication.

The article is saying you don't need it. It's good enough to say "well, life might just be sort of uncommon, and even in that scenario we shouldn't be surprised that we got a very low roll."

That is a surprising conclusion. No, we don't know the exact cause, but it means that the Fermi Paradox might not be a paradox, in the sense that it doesn't directly contradict all of our priors.

Think of it like the difference between saying, "Trump won the election because we fundamentally don't understand how democracy works in practice", and "Trump won the election because he had a 1 and 5 chance of winning, and sometimes 20% chance events happen."

I read it as saying something a little more subtle, which is that there is a lot of uncertainty in a couple of our critical estimates, and given that uncertainty what we see (no other life in the galaxy) is not that surprising. (That is, if you take the mean and multiply, you get misleadingly-high intuition.)

Of course if we do some more experiments and find that in fact the probability of abiogenesis is better approximated by 10^{-3,-2} that would change the expectations dramatically. This happened recently: we now have much better science around the incidence of earth-ish planets in solar systems, and a better understanding of what seems to contribute to good life-favorable (at least as we understand it) conditions on those planets. So this uncertainty can change with good work.

It's just that at this point it's really quite fair (per the authors) to expect that with more research we might equally well discover that P(abiogenesis) < 10^-100, in which case it would be astounding if we weren't alone in the observable universe.

(Good talk slides: http://www.jodrellbank.manchester.ac.uk/media/eps/jodrell-ba...)

This was helpful. That wasn't the way that I was reading the original paper, but I think I see what you're saying.

There's one remaining subtlety that I don't see in his comment or in almost any of the comments in this thread, and it's the entire novel point of the paper.

If you give any particular term in the Drake Equation a value of some magnitude, say, P(abiogenesis) < 10^-100, then you're still treating it as a point estimate, and this is the flaw at the heart of all arguments about the Fermi Paradox.

What the authors do instead is give each term of the Drake Equation a range of magnitudes. When you multiply those ranges of magnitudes together, you get a ton of different possible outcomes. If you then look at those outcomes together, you find that in over half of them, we are alone in the universe.

This is the "multivariate probability" that a top comment referred to, that seems to be problematic for a lot of people (including me).

The authors point out that with this approach, even if we nail down the range of probabilities for some of the terms, the uncertainties of the remaining terms will still lead towards a > 40% chance of being alone in the universe.

It's a little bit like: in a poker game, I draw five cards. Each of my cards is a 2, 3, 4, 5, or 6. What is the probability that I drew a straight? To calculate that, you'd count the number of different possible card combinations, and then count the number of those combinations that resulted in a straight.

What everyone has been doing previously in this analogy is calculating the odds of drawing each individual card.

In the case of the Drake Equation, using a probability distribution approach to estimating the chances of being alone in the universe leads to a very different result than we expect.

I hope I didn't add to the confusion.

> If you then look at those outcomes together, you find that in over half of them, we are alone in the universe.

Since we do not really know, anything but P=0.5 should imply incorrect prior estimates. That might be more insightful than whether alien life exists or not.

I find the notion that we have enough information to even guess at where life is let alone that we can assume there is none downright laughable to the point of obscenity. We know a lot less about this universe than it takes to make even sensible guesses as to generalizations about the nature of life in the universe.

Our best-effort guesses are literally the best we can do. Pretty much by definition, dismissing them because "we know so little" means taking a view that's worse than that guess.

> literally

excuse me, but no. Our best-effort guesses might be the best we could literally do. But there is no need to be that literal, or literal at all. As long as the uncertainty range includes 0.5, it's OK, but merely a test of how much we know as a fact as opposed to intuitively. And at that, the equation can surely be blown up further. Why would it be optimal?

My thoughts exactly, I always think: perhaps in 10 years we find an alternative to radio based communication which is far superior and then we find the galaxy teaming with communicating life forms... Or not. Who's to say? This whole thing seems to me an exercise in quantifying unknowns. We don't know the size of the categories we don't even know we don't know anything about. This can still be a fun exercise of course and it can give you an idea of the assumptions to prove or disprove but still... the value (beside the entertainment value) is pretty small imho.

Yep. Or maybe we’re all wrong about quantum mechanics or any of a number of theories. There’s a huge portion of the universes mass that we can’t explain. The unknowns are far too large to extrapolate.

Wait, no, I just actually look at the blog and the article. And ultimately, the article is saying more or less the same as the GP but with more detailed math. And blog essentially admits this.

The blog kind of references a situation where you'd have a high variance distribution but doesn't really describe it. There isn't any argument against the claim that the chance of a civilization on a given planet is independent of the chance of life on all the other planets in a given galaxy (modified by star-type but not by whether there's life nearby).

From the original paper:

"In this example, the point estimate for each parameter is 0.1, so the product of point estimates is a probability of 1 in a billion. Given a galaxy of 100 billion stars, the expected number of life-bearing stars would be 100, and the probability of all 100 billion events failing to produce intelligent civilizations can be shown to be vanishingly small: 3.7×10 ^−44

[...]

However, the result is extremely different if, rather than using point estimates, we take account of our uncertainty in the parameters by treating each parameter as if it were uniformly drawn from the interval [0, 0.2]. Monte Carlo simulation shows that this actually produces an empty galaxy 21.45 % of the time."

I take this to mean that collapsing a range into a single point will artificially inflate that point, and instead you need to look at the number of possible outcomes, not the average of all outcomes.

From the related blog post:

"Imagine we knew God flipped a coin. If it came up heads, He made 10 billion alien civilization. If it came up tails, He made none besides Earth. Using our one parameter Drake Equation, we determine that on average there should be 5 billion alien civilizations. Since we see zero, that’s quite the paradox, isn’t it?"

That seems like a consistent reading to me. Maybe I'm wrong - I take it you would draw a different conclusion?

Edit: No, thinking about it more and reading some other posts, I kind of get what you're saying. I'm still not really sure I'd call that a paradox though. It still seems to suggest to me that we may not need to rely on any of the really big theories to describe why we don't see life.

I agree that Fermi isn't a paradox but if the chance of an advanced civilization on a given star is independent from the chance of one on another, then the components of Drake's equation exist and to have the chance be small, the components must be small, for suitable definition of small.

The article and blog's meta-argument involves choosing components over a random distribution of universes and saying "well, there's a good chance you wind-up in a universe with small". But reasoning about random universes is debatable, introducing unnecessary metaphysics but even so, if you wind-up in a universe with a small chance of an advanced civilization, you will wind-up in a universe with Drake's components also small. Which is to say the whole reasoning does nothing but "muddy the waters".

The only way the "randomly chosen universe" argument matters is if we're jumping from universe to universe or if there's a force that inherently keeps us from reasoning about the why of the Drake components - but neither of those conditions are met.

"Trump won the election because we fundamentally don't understand how democracy works in practice", and "Trump won the election because he had a 1 and 5 chance of winning, and sometimes 20% chance events happen."

This is a great point. Still, if you say "we don't understand democracy because we don't understand that 20% chance events happen" then it seems like the points converge.

Or is it just because we have limit observation of the universe.

People in ancient times doesn't know much about the earth either.

When you say "we have not observed alien civilization", you are dismissing all the ufological data we have without valid justification. I can't agree with that unjustified data point set exclusion.

When you consider UFOs as a manifestation of ET civilization, the Fermi paradox does not exist.

And when you consider them as a manifestation of mental illness and jumping to conclusions, it exists again!

A paradox is a logical contradiction. That is what motivated the question of Fermi "They should be here, where are they ?".

The right answer to this question must remove the logical contradiction, and this is what we are interrested in. The answer that the ETs are visiting earth and reported through ufological sighting would be a valid one, but it is systematically ignored or discarded when considering the Fermi paradox.

That is, in my opinion, the only paradox.

PS regarding the downvote, Hackenews is not Facebook with its like button. On Hackernews, downvotes are for people who don't respect the rules.

> ufological data

my sides!

"Zoo theory". Even the Air Force now admits they've seen odd craft-like things in the sky that baffle the h8ll out of them. ET may be here but just don't want us to know it.

I wonder how advanced drone technology would need to be to be able to fake such a UFO as being from an alien.

A helium balloon made from plastic pipes was adequate in Delft in 1979, but the Japanese paper firebombs from WWII suggest that you don't need anything more than helium, paper, and lacquer, substituting hydrogen or methane for the helium in a pinch. So maybe drone technology of around 1770.

https://vimeo.com/50850893

That's getting close to impossible now. We've reached the point in technological development in which we can fake almost anything (and we can fake absolutely anything on photos/recording) - which calls into doubt any apparently supernatural event that would happen from now on. That is, given current technology level, were I found myself in front of a talking, burning bush, I wouldn't think "God", I'd think "a gas vent and a speaker".

"There the angel of the LORD appeared to him in flames of fire from within a bush. Moses saw that though the bush was on fire it did not burn up." - Exodus 3:2 (NIV)

Even Moses might not have been that impressed by merely a talking, burning bush.

Drones and balloons cannot make 100g turns.

Do you know where can I find more information on this?

In 2017/2018 the Air Force released a video of fa/18 pilots intercepting 'objects', which is rather interesting.

A good place to start is Project Blue Book however, it has years worth of information that was reported by members of the public etc that the government looked in to. I don't believe it was conclusive in proving the existence of these objects, but rather proof that the government was taking some level of interest in it.

https://www.archives.gov/research/military/air-force/ufos.ht...

A lot of that was diversionary noise, to help maintain secrecy of stealth aircraft development.

I think you're right, from what I've read about it. I know there's a lot of resources out there on the topic, but it's hard to post links on HN with a straight face knowing that 99.9999% of it is white noise.

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