5 ms·

> None of this probabilistic reasoning matters in the face of the anthropic principle... In fact, the settings of our universe imply nothing. What a sad anthro

> None of this probabilistic reasoning matters in the face of the anthropic principle... In fact, the settings of our universe imply nothing. What a sad anthropic principle that would be! In fact, you can use the fact that humans exist to put (loose) constraints on this universe's parameters. For example, clearly the average temperature must be below one billion Kelvin. Making that kind of argument tighter and more precise actually leads to interesting results: bounds on spacetime black hole formation rate, limits on densitiy of dark energy, etc. The authors in OP's post take an interesting variant of this line of reasoning: If the universe is "really bad" at producing long strings of RNS, then humans must just be a fluke. In that case, maybe most life in the multiverse exists alone in its own observational bubble. They caculate with their model that self-replicating DNS is indeed hard to replicate. This also means that finding aliens would provide strong evidence against their model. The weakest form of anthropic argument is the tautological aspect you mention, but I wouldn't cut it so short.

titzer 5y ago
> to put (loose) constraints on this universe's parameters. I was referring to the fundamental constants of physics. A lot of argumentation has happened around whether they are "fine-tuned". In the sense that a small change has a radical effect on matter and spacetime, to the point where chemistry would not work at all to make any kind of biological entities, YES, YES, absolutely, our universe is fine-tuned for human life. Or vice versa. Human life is fine-tuned for exactly this universe, planet, climate (!), and time period! There are several traps that philosophers and cosmologists keep falling into, primarily around probability. Clearly we are not in an average universe, from the very get go. We have no idea how these constants get set, what set them, if there was a universe before that had different constants, if universes elsewhere have different constants. Even if we did know that other universes exist, we have no way to reason about the probability of our universe--we don't know the distribution. If we were to start positing that the constants are randomly chosen, then we're in a very special universe indeed. But somehow, when it comes to these constants, the "probabilistic thinking" just gets forgotten. Philosophers just blink and look away. These constants are special as hell. The next issue is that there is a huge philosophical problem in assuming that probability is even a thing, because every rando weird thing that has happened has fed into the stupidly improbable fact of our existence. The assumption that we are drawn from some kind of distribution is just a philosophical axiom that goes unstated. Maybe we aren't drawn from some probability distribution but are instead linked in causal chains impossibly long and intricate that using probability has a tool becomes meaningless. To understand what I mean there, just recall that the dinosaurs ruled the Earth for over a hundred million years. They were wiped out by an asteroid with a stupidly improbable chance of impact. The mass extinction that followed was so brutal that literally every single thing that survived pretty much made it by the skin of their teeth--including mammals. So every Tom, Dick, and Harry rabbit that managed to eek out survival on the blasted plains, carrying their painstakingly tuned genetic code, mattered. To the extent that many whole genera of life today depend on literally just a few individuals having survived this cataclysm. The Earth didn't mint new kinds genomes from nothing, they grew and branched off what survived. And it wasn't luck...they were better adapted to the new hellscape. Or was it? Sliced as finely as single individuals, we might be here because a single proto mammal survived a harsh winter or leaped out of the jaws of a predator at just the right time. Put odds on that one. But speaking of "luck", it wasn't "luck" that the asteroid hit at that moment. It hit because of orbital mechanics, a complex but completely predictable mathematical certainty of orbits and periods. Pretty much all the macro events that we observe as being to have led here to this moment with these funny barely space-faring apes yammering at each other through HN are deterministic, not stochastic events. And the next thought that pops into your head on how to reply won't be stochastic either. Reasoning about our universe using some Drake-equation-esque probability floundering is a complete waste of time. We got here by history and this whole freaking show is one giant example of selection bias. Average universe, my ass!
- dboreham 5y ago
  The probability for one asteroid hitting earth is low, but the probability that some asteroid will hit in a billion year time window is extremely high.
  - titzer 5y ago
    The specific asteroid that hit the Earth was not produced by a stochastic process, but a deterministic one. You are mistaking the tool (probability modeling) for reality. In reality, had that particular asteroid not hit at that time, yes, sure one would eventually have, but it might have been tens or hundreds of millions of years later....that a different asteroid hit, at which time the ecosystem of non-dominant species could have been completely different, and mammals would not have come out on top (and led to us). So when you actually look at reality and the casually-related events, you have to keep taking on massive amounts of zeroes to come up with probabilities for how things happened in exactly just the right way (this way)--we are talking thousands, maybe hundreds of thousands of zeroes, like 10^-1000000. That's exactly the problem with probability going wonky; so many things are not independent random variables. The whole analysis is wrong. But that's just part of what I am saying. The odds are low, yes, but everything is distorted because of survivorship bias. Since the odds of our reality looking (exactly) like this are astronomically low, it is by definition not the case that we are in an average scenario, we're in a super rare scenario; but moreover, we are survivors in that scenario, and literally everything we look back at is hugely biased by the fact that we exist. So we are absolutely not in an average case, because the selection bias of surviving is inescapable. Put another way, there could be a process that rolls a die every second and 99.99% of the time, destroys the universe. In the .01% of time, we survive and don't even notice. We keep perceiving those .01%, and multiplied together, the odds of surviving even a single minute are astronomically low. In the average universe in this scenario, everyone is dead! But we can't perceive universes in which we are dead; we wouldn't even be able to discover this process exists! So the whole business with universes randomly chosen from a distribution is just a bad model, as clearly our existence cannot be explained that way. Philosophers and cosmologists keep assuming that this is going on and that we must be in some average scenario. Uh, no.

titzer 5y ago

> to put (loose) constraints on this universe's parameters. I was referring to the fundamental constants of physics. A lot of argumentation has happened around whether they are "fine-tuned". In the sense that a small change has a radical effect on matter and spacetime, to the point where chemistry would not work at all to make any kind of biological entities, YES, YES, absolutely, our universe is fine-tuned for human life. Or vice versa. Human life is fine-tuned for exactly this universe, planet, climate (!), and time period! There are several traps that philosophers and cosmologists keep falling into, primarily around probability. Clearly we are not in an average universe, from the very get go. We have no idea how these constants get set, what set them, if there was a universe before that had different constants, if universes elsewhere have different constants. Even if we did know that other universes exist, we have no way to reason about the probability of our universe--we don't know the distribution. If we were to start positing that the constants are randomly chosen, then we're in a very special universe indeed. But somehow, when it comes to these constants, the "probabilistic thinking" just gets forgotten. Philosophers just blink and look away. These constants are special as hell. The next issue is that there is a huge philosophical problem in assuming that probability is even a thing, because every rando weird thing that has happened has fed into the stupidly improbable fact of our existence. The assumption that we are drawn from some kind of distribution is just a philosophical axiom that goes unstated. Maybe we aren't drawn from some probability distribution but are instead linked in causal chains impossibly long and intricate that using probability has a tool becomes meaningless. To understand what I mean there, just recall that the dinosaurs ruled the Earth for over a hundred million years. They were wiped out by an asteroid with a stupidly improbable chance of impact. The mass extinction that followed was so brutal that literally every single thing that survived pretty much made it by the skin of their teeth--including mammals. So every Tom, Dick, and Harry rabbit that managed to eek out survival on the blasted plains, carrying their painstakingly tuned genetic code, mattered. To the extent that many whole genera of life today depend on literally just a few individuals having survived this cataclysm. The Earth didn't mint new kinds genomes from nothing, they grew and branched off what survived. And it wasn't luck...they were better adapted to the new hellscape. Or was it? Sliced as finely as single individuals, we might be here because a single proto mammal survived a harsh winter or leaped out of the jaws of a predator at just the right time. Put odds on that one. But speaking of "luck", it wasn't "luck" that the asteroid hit at that moment. It hit because of orbital mechanics, a complex but completely predictable mathematical certainty of orbits and periods. Pretty much all the macro events that we observe as being to have led here to this moment with these funny barely space-faring apes yammering at each other through HN are deterministic, not stochastic events. And the next thought that pops into your head on how to reply won't be stochastic either. Reasoning about our universe using some Drake-equation-esque probability floundering is a complete waste of time. We got here by history and this whole freaking show is one giant example of selection bias. Average universe, my ass!

dboreham 5y ago
The probability for one asteroid hitting earth is low, but the probability that some asteroid will hit in a billion year time window is extremely high.
- titzer 5y ago
  The specific asteroid that hit the Earth was not produced by a stochastic process, but a deterministic one. You are mistaking the tool (probability modeling) for reality. In reality, had that particular asteroid not hit at that time, yes, sure one would eventually have, but it might have been tens or hundreds of millions of years later....that a different asteroid hit, at which time the ecosystem of non-dominant species could have been completely different, and mammals would not have come out on top (and led to us). So when you actually look at reality and the casually-related events, you have to keep taking on massive amounts of zeroes to come up with probabilities for how things happened in exactly just the right way (this way)--we are talking thousands, maybe hundreds of thousands of zeroes, like 10^-1000000. That's exactly the problem with probability going wonky; so many things are not independent random variables. The whole analysis is wrong. But that's just part of what I am saying. The odds are low, yes, but everything is distorted because of survivorship bias. Since the odds of our reality looking (exactly) like this are astronomically low, it is by definition not the case that we are in an average scenario, we're in a super rare scenario; but moreover, we are survivors in that scenario, and literally everything we look back at is hugely biased by the fact that we exist. So we are absolutely not in an average case, because the selection bias of surviving is inescapable. Put another way, there could be a process that rolls a die every second and 99.99% of the time, destroys the universe. In the .01% of time, we survive and don't even notice. We keep perceiving those .01%, and multiplied together, the odds of surviving even a single minute are astronomically low. In the average universe in this scenario, everyone is dead! But we can't perceive universes in which we are dead; we wouldn't even be able to discover this process exists! So the whole business with universes randomly chosen from a distribution is just a bad model, as clearly our existence cannot be explained that way. Philosophers and cosmologists keep assuming that this is going on and that we must be in some average scenario. Uh, no.