Isn't arresting anti-war and dissident activists/protestors and then sending them to the front to gain leadership experience and a chance to b radicalize your army almost always a bad idea? — Count Timothy von Icarus

That was one mistake they did not repeat this time around. Reportedly, when Wagner and then MoD were recruiting fighters from prisons, political prisoners were strictly excluded.

Gee I bet the CIA and State Dept are breaking out popcorn. — Wayfarer

Don't you know? It's a CIA/State Dept/NATO coup! They are omnipresent and all-powerful. Nothing in the world happens but through their agency and intent. Nothing important, anyway.

Actually Putin referred to 1917 in his speech, so he is already using the dolchstoss argument. — ssu

He literally used the words "stab in the back" in his televised speech (and following him - a lineup of loyal politicians, including Chechen strongman Kadyrov, who had allied with Prigozhine on occasion).

To take a step back, I see the whole issue of determinism as a metaphysical one, not subject to empirical verification or falsification. It's a matter of point of view, not fact. I don't see it as a very useful way of thinking - it's misleading. — T Clark

I rather see it instrumentally, as a characteristic of specific theories or models that we adopt. And I mean not just scientific theories, but also our informal folk theories, including theories of mind. At the same time, I am not convinced that there is one true theory to rule them all at the bottom of creation. Which in turn makes it meaningless to ask whether the world is really deterministic or indeterministic.

The Paradox of Predictability concerns determinism. In particular, it concerns the idea that if determinism is true, then true predictions should be possible about the future state of the world (or people or subsystems therein). — NotAristotle

Predictability, in the sense that you employ in your thought experiment, is not usually part of the definition of determinism, nor does it follow as a necessary implication. The first paper that you cite gives a more conventional definition:

a universe U is deterministic when, for any arbitrarily chosen time t₀, there exists a law-like function f_L which maps the initial state of the universe U₀ at time t₀ in a unique manner onto the state of the universe U_t at any arbitrarily chosen later time t:

U_t = f_L(U₀) — Determinism and the Paradox of Predictability

Therefore, even if we accept the reasoning in your example, it does not logically follow that determinism is false. All that we can conclude is that not all of the assumptions can be true at the same time. Rather than determinism being false, it could be that predictability is not achievable under the specified conditions.

The first paper that you cited makes an important point about predictability right in the abstract, by drawing a distinction between external predictability and embedded predictability:

The inference from determinism to predictability, though intuitively plausible, needs to be qualified in an important respect. We need to distinguish between two different kinds of predictability. On the one hand, determinism implies external predictability, that is, the possibility for an external observer, not part of the universe, to predict, in principle, all future states of the universe. Yet, on the other hand, embedded predictability as the possibility for an embedded subsystem in the universe to make such predictions, does not obtain in a deterministic universe. — Determinism and the Paradox of Predictability

also made this point: a Laplacian demon might have the knowledge of the state of the world at a different time, but the demon, being external to the world, does not have to know its own state.

Another point concerns the possibility of prediction qua computation. It is one thing for the function f_L to exist in the abstract (and even for some hypothetical entity to have the knowledge of this function), but this is not the same as being able to compute this function given finite computational resources. Determinism, in its most general formulation, does not commit to computability. This, I think, is similar to the point made by

Socialists sort of promoting nationalist authoritatian oppressive degenerative capitalist Kremlin...? — jorndoe

They publish articles about the Ukraine war under the heading "US-NATO Conflict with Russia over Ukraine" That's quality journalism for you :roll: Their parroting of Russian official narrative is tactical, sort of like the Iran-Russia alliance in this war. Anything that can be used to poke the Big Satan in the eye will do.

These socialists' only concern is "the struggle," and they are indiscriminate about methods. Being truthful is not the objective; being correct - politically correct, in the older, unironic sense - is what it's all about.

The most likely culprit is of course Russia as it's totally logical for them to a) make the end of the Dnipro unpassable and b) then withdraw forces from there to plug the Ukrainian counterattack. The only thing now is that after WW2 blowing up dams has been a war crime. But obviously Russia doesn't give a damn. Or a dam. — ssu

Russian propaganda is also trying to play the cui bono card. Their western proxies amplify that narrative:

Although it is unclear who was responsible for the attack, last year, Ukrainian troops fired on the dam in an attempt to raise water levels downstream, and the military leadership had publicly contemplated destroying it altogether. — World Socialist Website

Militarily, it's not actually clear which side this benefits or hurts more. Ukrainian army wasn't likely to attempt crossing the Dnipro river there, except for amphibious incursions, which the flooding does not affect. For that reason, the Russians didn't have many forces defending the left bank. The flooding destroyed their first lines of defense, which, in theory, would make the crossing easier for the Ukrainians after the waters recede. But the Russians still hold positions on higher ground, which would make a full-scale assault across a half-kilometer wide river very problematic.

Naturally, the Ukrainians had even less cause to fear Russian attacks in this area. Ever since their retreat from the right bank, all that the Russians could do - and continue doing - is conduct chaotic shelling of Kherson and other settlements in the area to terrorize and punish the remaining civilian population. They have no force left to conduct a large-scale assault anywhere, let alone in such a difficult place. Hell, it took them nine months, tons of ammunition and suicidal human wave assaults just to grind down one town of little strategic significance - and that was their only "success story" in half a year of war.

In my opinion, Pattee makes the mistake of assigning human concepts to nature. — Wolfgang

This is precisely the issue that I have with this paragraph in your opening post:

A functioning organization is something that works according to certain rules, and those rules are made by someone in, say, a social organization. If we assume that there is nothing and no one who has developed rules for life, then it must be life itself that has developed these rules.
In addition to these rules, there must of course be an authority that monitors compliance with the rules and corrects them if necessary. — Wolfgang

Quite apart from the merits of the theory that you sketch further on, the problem here is that you run with the anthropomorphic metaphor without pausing to question its applicability out of its social context.

Must there be "an authority that monitors compliance"? That's not quite true even in human societies, where social rules, most of which are informal, are largely heeded out of habit and good will stemming from mutual interest, without needing any active control and enforcement. In any case, there is no prima facie reason to extend the metaphor of social organization to systems other than human societies. In the end, you may even be right to do so, but to get to that point requires a good deal of reflection. You cannot just assume that the metaphor applies based on suggestive language alone.

Cheers. Good stuff. I didn't realize there was a song to go with the instrumentals. That guitar dude's arrangement of the accompaniment is impressive as a technical and musical achievement, but without the song the overall effect is merely... nice.

Speaking of Baroque... Many years ago I heard this tune in a garish synth arrangement, in some indie sci-fi flick:



I had forgotten the movie, but somehow the tune impressed itself upon me. I had no idea what it was, and hadn't heard it since (except in my head once in a while). Until a couple of days ago, when I heard it on classical radio - this time with the title and composer's name attached.

And here it is, in all its Baroque ostinato glory:
Marin Marais - Sonnerie de Sainte-Geneviève (The Bells of St. Genevieve)


(Curiously, this recording is also from a movie soundtrack. I'm going to watch the movie when I get a chance.)

And a couple more affecting pieces by Marais, performed by the same stellar ensemble:

I am not a connoisseur or anything (I don't even know who Steely Dan is), but wow!

You can recognize Glass right from the first measure from his trademark arpeggios, but you need to keep in mind that this work was composed before he settled into his neo-Romantic groove. And indeed, while instantly recognizable, it doesn't sound stale to my ear.

A combination of “nu jazz” and “acid jazz” — javi2541997

I don't know much about “nu jazz” and “acid jazz”, but I like this. Will listen more!

https://xkcd.com/1732/ — Benkei

This is excellent.

We need the technology of 2065: fusion. — frank

I see what you did there :D

"Breaching 1.5C threshold" in a single year is meaningless, because there is no such threshold. — SophistiCat

Not meaningless, it signals that we are going above predicted deviations. — Manuel

What predictions are you talking about? Climatologists don't make predictions for individual years.

Eight of the past ten years were the warmest on record, and a similar trend held in preceding decades. That is meaningful. But a single-year record does not mean much on its own, and comparing it with a long-term average prediction is just ignorant.

While I share everyone's concern and have a feeling that things are indeed worse than expected, that Aljazeera headline is misleading if that's all you read. The article goes on to note:

But that did not necessarily mean the world would cross the long-term warming threshold of 1.5C above pre-industrial levels set out in the 2015 Paris Agreement. — Aljazeera

"Breaching 1.5C threshold" in a single year is meaningless, because there is no such threshold. Single-year averages can deviate widely from the long-term trend, and in an El Nino year that's expected.

We were talking about subjective probabilities, not actual probabilities — RogueAI

Any probability has to obey additivity and normalization axioms, otherwise it's not a probability. If you find that your subjective probabilities add up to more than 100%, then you are being inconsistent.

This is the basis for my suggestion that Boltzmann brains and human-life are equally likely to occur. Despite the latter's pattern being more complex. — Down The Rabbit Hole

You need to be careful about what exactly "equally likely to occur" means in this context. The way cosmologists might pose this question is: "Given an observer, is it more likely to be a regular observer (a human or a similarly evolved creature) or a freak observer like a Boltzmann Brain?" This is a tricky epistemological question involving concepts like reference class, self-location and self-selection.

And yes, infinite, or just very big worlds seem to present a general challenge to observations:

Big World theories, popular in contemporary cosmology, engender a peculiar methodological problem: because they say the world is very big and somewhat stochastic, they imply (or make it highly probable) that every possible human observation is made. The difficulty is that it is unclear how we could ever have empirical reasons for preferring one such theory to another, since they all seem to fit equally well with whatever we observe. — Nick Bostrom

Intuitively though it seems that simply adding "more of the same" to the world (more space or more time or more observers) should not make a difference to a generic observation made by a particular observer at a particular place at a particular time, so the challenge to epistemologists is to explain just how this challenge is only a seeming one. (Bostrom purports to meet it with his Self-Sampling Assumption, which he also uses elsewhere to analyze puzzles like Boltzmann Brains.)

If the universe is infinite, then there are infinitely many Boltzmann brains and infinitely many non-Boltzmann brains. Since the two sets are equal, the subjective probability that one is a member of either set is 50/50. — RogueAI

• If the universe is infinite, then there are infinitely many @RogueAI brains and infinitely many non-@RogueAI brains. So for any given brain, there is a 50% probability that it is a @RogueAI brain.
• If the universe is infinite, then there are infinitely many @Down The Rabbit Hole brains and infinitely many non-@Down The Rabbit Hole brains. So for any given brain, there is a 50% probability that it is a @Down The Rabbit Hole brain.
• If the universe is infinite, then any given brain is either a @RogueAI or a @Down The Rabbit Hole brain.

See the problem here? Probabilities don't work like that.

In any case, this is not relevant to the OP video, which was comparing the probabilities of a "Boltzmann Brain" fluctuation and a "Boltzmann Big Bang" fluctuation. You don't need an infinite domain with its measure problems to do that.

https://www.youtube.com/watch?v=OpohbXB_JZU

How can we defeat the Boltzmann brain paradox?

In an infinite duration, aren't all possible outcomes equally likely to occur? — Down The Rabbit Hole

The clip doesn't say that last bit. That said, it is more confusing than anything else. I only got what it was hinting and gesturing at because I've already read more about this topic. If you are interested, I would advise you to do the same.

would such a progression of linear time to a conscious being allow them to understand its infinite nature though not being able experience infinity itself due to their limited timespan — invicta

What are your criteria for understanding in this case? You have experienced living for N number of years. Can you understand the duration of N+1 years despite not having personally experienced it? You have seen a limited number of things in your life. Would this fact be an obstacle to you understanding some thing - a rock, a tree - that you have never seen and may never see?

You will impatiently respond with "yes, of course!" to these questions and then tell me that your question is different because infinity, etc. But this is why it is crucial to first understand - and be able to explain - what it is that you are asking. In philosophy this is the most - and often the only - important thing.

So, what sort of "understanding" are you after? What would satisfy you that you "understand" infinite time?

In a paper I wrote on the topic — Pierre-Normand

I would be interested in reading it - it sounds like an interesting take. I lean towards compatibilism, but I am sympathetic to some libertarian perspectives, particularly agent-causal.

I see this as a Sartrean-type dilemma where the ethical thing to do is to simply choose and take responsibility for our choice rather than try to justify it by any particular theory that would abstract us away from such responsibility and in any case could provide nothing more than arbitrary grounds for judgement when considered meta-ethically. — Baden

:up:

This highlights how we all choose selfishly every day based on proximity rather than ethics. — Baden

The only thing I disagree with is this opposition of "selfish" vs. "ethical." If you do as you say above - choose responsibly - that means you do what you think is the right thing to do (why else would you choose that course of action?) And that, by definition, is the ethical thing to do, theory or no theory. I don't see what selfishness has to do with that.

Hiya Paul!

The problem with putting initial conditions off limits is that virtually everything we observe in the universe is dependant on initial conditions. — Count Timothy von Icarus

If that is how the theory is structured, yes. But that's a feature, not a bug. You could alternatively explain initial conditions in terms of later features - that is essentially what anthropic explanations do.

That is, of the set of all physically possible things we could see, we shouldn't expect to see one universe more than the other. Thus, if we come to see "Christ is King," "Zeus wuz here," "Led Zeppelin rules!," scrawled out in quasars and galaxies at the far end of the cosmos, this shouldn't raise an eyebrow? Because, provided the universe is deterministic, such an ordering would be fully determined by those inscrutable initial conditions. — Count Timothy von Icarus

I am not sure what this fantastical hypothetical is supposed to argue.

When you think of the Big Bang, you just mean inflation, right? You're not adding a singularity to it, are you? — frank

Historically, the so-called Big Bang theory came first, and theor(ies) of inflation were developed later, around 1980s. Inflation pushes the Big Bang chronology a little further back, introduces some new theoretical posits, but in return it rather neatly explains some of the later features of the early universe.

As I was saying earlier, the informal name Big Bang is variously attached to different theories, periods and events. Sometimes it is even used to refer to the entire cosmological timeline, going back to time zero (which historically has been called "Big Bang singularity," although few believe in an actual singularity.)

In the context of the Past Hypothesis, again for historical reasons, we can take the initial state to be after the hypothetical inflation, perhaps somewhere around the beginning of nucleothynthesis, when hydrogen and helium ions formed. The precise cutoff is not important, because the same considerations can be extended to earlier periods.



The difficulty of applying 19th century equilibrium thermodynamics to the early universe becomes even more severe in earlier periods, however, because they are extremely brief and thermodynamically unstable.

Yes, I was going to post that. The really amazing thing is that the program provided fake references for its accusations. The links to references in The Guardian and other sources went nowhere. — T Clark

I am surprised that they haven't addressed the fake links issue. ChatGPT-based AIs are not minimalistic like AlphaChess, for example, where developers hard-code a minimal set of rules and then let the program loose on data or an adversarial learning partner to develop all on its own. They add ad hoc rules and guardrails and keep fine-tuning the system.

A rule to prevent the AI from generating fake links would seem like a low-hanging fruit in this respect. Links are clearly distinguished from normal text, both in their formal syntax and in how they are generated (they couldn't be constructed from lexical tokens the same way as text or they would almost always be wrong). And where there is a preexisting distinction, a rule can readily be attached.

Historically, the line of reasoning has gone in the opposite direction. One of the most compelling arguments for the Big Bang was that, in an eternal universe of the sort people thought existed in the late 19th and early 20th centuries, the conditions we observed in the universe seemed highly unlikely based on statistical mechanics. That is, we accept such a starting point for observable existence, in part, because of arguments about the likelihood of entropy levels in the first place. An eternal universe could produce such phenomena, it just is unlikely too. — Count Timothy von Icarus

The Big Bang theory grew out of General Relativity, which allowed it as one of its general solutions, and astronomical observations that made it increasingly likely, until there was little room for alternatives. That this also solved the problem of entropy was a welcome bonus. But the plausibility of the theory was not evaluated by entropy calculations of the kind that are performed to justify the thesis about the improbability of the initial state.

Before GR and Big Bang, in the Newtonian cosmology of the day, the most natural scientific picture of the world was that of an infinite, past-eternal universe. (Not because of some anti-religious bias, as some claim, but simply because it's hard to justify or even imagine a Newtonian universe whose timeline abruptly ends for no apparent reason some finite time in the past.) But that presented a challenge as people came to realize that many, if not all things in this world could not be past-eternal. The Sun, for example, which was thought to be a burning ball, could not have an infinite supply of fuel. Same for all the other stars in the sky. Who was lighting them up for all eternity?

The development of thermodynamics posed that problem especially acutely. Clearly, in a closed universe that is not in thermodynamic equilibrium entropy must have had a minimum a finite time in the past. This is where Boltzmann came up with the idea of a gigantic entropy fluctuation giving rise to the observable universe. In an infinite, eternal universe such a fluctuation would be almost inevitable, so its improbability was not an issue as such. However, brilliant man that he was, Boltzmann also thought of a worrying problem with this conjecture: the one we now know as the Boltzmann Brain. And even now, as you noted further on, as updated versions of Boltzmann fluctuation conjecture are being proposed to explain the origin of Big Bang, that problem still keeps cosmologists awake at night.

Anyway, all this is irrelevant to the question of the "probability" of the true initial state of the Big Bang universe, i.e. a state that comes with no known history and no theory of its origin. Boltzmann's entropy fluctuation was posited not as an initial state (that would be a contradiction of terms) but as an event in a Newtonian universe. In that context the calculation of probability can be meaningfully performed. Not so for a true initial state.

I'm still not quite sure what your objection was because my original point was that claiming that there is no reason to think the universe would have low entropy (agreeing that it appears to be unlikely), and then invoking the anthropic principle to fix that issue, reduced explanations to the triviality that all possible things happen and so whatever is observed MUST occur. If you don't think the Past Hypothesis or Fine Tuning Problem needs an answer then there is no reason to invoke the Anthropic Principle in the first place. — Count Timothy von Icarus

Anthropic reasoning and fine tuning worries arise in the context of the origins of the universe, when theories such as Eternal Inflation are discussed. Such theories must explain the Past Hypothesis as a matter of course (or they would not match observations), but they raise other questions. Absent a theory though, worrying about the "specialness" or "improbability" of the initial state makes no sense, in my view.

You fight your superficiality, your shallowness, so as to try to come at people without unreal expectations, without an overload of bias or hope or arrogance, as untanklike as you can be, sans cannon and machine guns and steel plating half a foot thick; you come at them unmenacingly on your own ten toes instead of tearing up the turf with your caterpillar treads, take them on with an open mind, as equals, man to man, as we used to say, and yet you never fail to get them wrong. You might as well have the brain of a tank. You get them wrong before you meet them, while you're anticipating meeting them; you get them wrong while you're with them; and then you go home to tell somebody else about the meeting and you get them all wrong again. Since the same generally goes for them with you, the whole thing is really a dazzling illusion empty of all perception, an astonishing farce of misperception. And yet what are we to do about this terribly significant business of other people, which gets bled of the significance we think it has and takes on instead a significance that is ludicrous, so ill-equipped are we all to envision one another's interior workings and invisible aims? Is everyone to go off and lock the door and sit secluded like the lonely writers do, in a soundproof cell, summoning people out of words and then proposing that these word people are closer to the real thing than the real people that we mangle with our ignorance every day? The fact remains that getting people right is not what living is all about anyway. It's getting them wrong that is living, getting them wrong and wrong and wrong and then, on careful reconsideration, getting them wrong again. That's how we know we're alive: we're wrong. Maybe the best thing would be to forget being right or wrong about people and just go along for the ride. But if you can do that—well, lucky you. — Philip Roth, American Pastoral

Just finished that book :heart:

And now, after an abortive foray into another book that I didn't really like...

Call me Ishmael.

:)

Kremlin rhetoric regarding NATO expansion has been all over the place. To start with, NATO expansion was presented to the West as the main excuse for going to war. Putin's war ultimatum issued in the run-up to the Ukraine invasion demanded the roll-back of NATO to the Soviet-era status quo, and when these impossible demands were not accepted, that was given as a casus belli in his war speech. Later, when Finland and Sweden announced their intention to join NATO, while Russia's war against Ukraine was floundering, Putin sheepishly brushed that aside as nothing to worry about. All that hysterical rhetoric about NATO missile flight time was already forgotten. Now they aren't sure how to react. Peskov mumbles: oh noes, NATO expansion not good. Putin just pouts.

Thermodynamics isn't the only global asymmetry either. There is wave asymmetry in electromagnetism, the jury is out on of this reduces to the thermodynamic arrow; there is radiation asymmetry, etc. — Count Timothy von Icarus

As an aside, if you mean the retarded/advanced wave asymmetry, @Kenosha Kid had a thread here about Cramer's Transactional Interpretation of quantum mechanics, which eliminates this asymmetry.

Not to mention there is an overarching microlevel problem. Observed wavefunction collapse only happens in one direction. This is a fundemental level asymmetry that is probably the most vetted empirical results in the sciences. — Count Timothy von Icarus

The usual formulations of quantum mechanics are indeed time-asymmetric, but QM can be equivalently formulated in a time-neutral manner, so that any time asymmetry is a matter of interpretation.

It doesn't seem like thermodynamics can be exactly what we mean by time because if the thermodynamic arrow were to reverse, it doesn't seem like it would throw time in reverse. — Count Timothy von Icarus

I never said that thermodynamics is what we mean by time; rather, what we mean by phenomenal time asymmetry (the so-called arrow of time) is explained by the thermodynamic asymmetry on a large scale, which in turn is explained by the asymmetry of boundary conditions. The forward direction of time tracks the direction of increasing entropy in our observable universe. But I am not sure what you mean by the thermodynamic arrow reversing.

If time reversed when the thermodynamic arrow reversed, we should expect that, when the very last area of the universe that is out of equilibrium and not contracting reaches equilibrium, particles should suddenly have their momentum reverse and begin backtracking. — Count Timothy von Icarus

You lost me here.

Indeed, we can well imagine sticking an observer in a tank with a Maxwell's Demon and having them watch the isolated system they sit in reduce in entropy over time. Global entropy would reduce, but that says nothing about the observer subsystem and how it experiences time. — Count Timothy von Icarus

If your region of the universe that undergoes a uniform thermodynamic evolution is large enough, you won't notice anything, because your perception of time will track the direction of increasing entropy. Talking about biological arrow of time, you will always remember entropy being lower in the "past," and you will not remember the "future."

If nothing can be said about likeliness vis-á-vis the early universe how do you vet any scientific theories about it? How can you say "this explanation is more likely to be the case than this one?" — Count Timothy von Icarus

The same way we vet all other theories? All theories have some brute facts, some givens in them: equations, constants, boundary conditions. There is nothing special about the initial conditions of the Big Bang theory in that respect.

As you point out, it is now commonly accepted that a period of cosmic inflation preceded the Big Bang. — Count Timothy von Icarus

Yes, but you are now talking about a different theory, or rather an extension of the Big Bang theory. What is taken to be the initial state in Big Bang is no longer the initial state in Inflation. Inflation leads up to the hot Big Bang, thus giving it a causal explanation, but raising questions of its own. (I think the Banks paper deals with those questions, but like I said, I cannot follow it.)

A major piece of evidence in favor of inflation is that patterns of light from the early universe are consistent with proposed inflation and unlikely under other existing models. — Count Timothy von Icarus

Yes, and that (the bolded parts) is just like the Big Bang theory, and every other scientific theory, gets its justification.

But you said it yourself: likely or unlikely under some model. The Big Bang theory doesn't model its own initial conditions - how could it? So to talk about the likelihood of Big Bang's initial state by converting dubious entropy into bogus probability makes little sense. You can talk about Big Bang's initial state in the context of the Inflation theory, and if you find that it predicts those conditions with a low probability, then that's a problem for Inflation.

This seems as much of a mixup to me as when people claim "nothing can come before the Big Bang because time and cause are meaningless past that point." — Count Timothy von Icarus

If there is a mixup here, it is a mixup of terminology. When people say Big Bang, they can mean t = 0 in the Big Bang chronology (the theoretical singularity in the classical relativistic model on which Big Bang theory is based), or they can mean the earliest period where the Big Bang theory is applicable, which comes a little bit after t = 0 (and which would be preceded by Inflation), or they can even mean the entire period from there till now and beyond (the Big Bang universe). The worry about time ending or becoming physically meaningless as it approaches t = 0 is not unfounded, for although we know little about that earliest period, there is reason to think that physical clocks that give time its meaning beyond a mathematical formalism may no longer work there.

If the universe did not expand after the Big Bang, it would have stayed as it was shortly after the Big Bang: a hot, dense, uniform plasma. — SophistiCat

Sure, but this is speculative. It implies that you can get the "Big Bang," under highly different conditions. — Count Timothy von Icarus

And that's my point. When you ask why something is this way and not the other way - for example, why the Big Bang universe has a time asymmetry - the implication is that it could have been otherwise. That is obviously problematic with things like laws, constants and boundary conditions, unless we already have a reductive theory in mind. If that is not available, then all we can do is imagine an alternative world. We can't say anything more, and we can't attach probabilities to these imaginary alternatives, because that would imply that we know more than we actually do.


I don't have time now to discuss thermodynamics and the arrow of time, but I'll try to get back to this later.

One can choose to be moral or immoral, but one cannot chose what is moral and what is immoral. — unenlightened

Is there a difference in your mind between choosing and deciding? Are you associating choice with something arbitrary or capricious? That's not how we generally make choices, especially about things that we deem to be important.

The beginning of time had to be an entropy minimum, since entropy can only increase. That's the least surprising thing here - we've known this since the 19th century. As for Big Bang being an entropy fluctuation, that was actually an idea first proposed by Boltzmann. It is still speculative though.

I think the important point made there is about the relation between entropy and the direction of time ("the arrow of time"). Time on the global scale owes its existence to the fact that the entropy of the universe on a large scale increases, and the forward direction of time tracks the direction of that entropy increase. If the universe did not expand after the Big Bang, it would have stayed as it was shortly after the Big Bang: a hot, dense, uniform plasma. There would be no large-scale changes - only microscopic, time-symmetric changes as particles bump into each other. (Well, there would be helium synthesis for a while, but eventually that process would saturate and reach equilibrium.) Therefore, time arrow as a global direction of change would not exist; time would not have a preferred direction. Things would look pretty much the same if you rolled time forwards or backwards.

https://www.hindawi.com/journals/complexity/2022/9956885/ — Pantagruel

This is an interesting paper - thanks!

Yeah, I had a look, but as one might expect from such a vid, it has just a short soundbite concerning the topic under discussion here.

Yes this I don't understand then I suppose, because isn't equilibrium necessarily maximum entropy... If entropy always increases, it can only be in equilibrium if max entropy has been reached no? — ChatteringMonkey

Yes, entropy reaches its maximum at equilibrium. But the universe was never actually at equilibrium, because it was and still is quickly expanding. ("Quickly" has a technical meaning here: if it was expanding slowly enough - quasi-statically - then the maximum entropy would stay the same. Expansion as such does not increase entropy, but irreversible expansion does.) Still, if you consider very short timespans at which expansion can be neglected, then you could say that the early universe was indeed at its maximum entropy.

The space that is currently occupied by the observable universe was at a much lower entropy 14 billion years ago — SophistiCat

The space or the matter in that space is at lower entropy? That is what is confusing to me. How can space itself be measured entropically. Isn't that just the condition that sets the degrees of freedom for matter in that space to be in, determining the range of entropy? — ChatteringMonkey

Sorry, yes, I meant the matter encompassed by that space.

Yes unlikely by definition maybe isn't true for initial conditions, I can see the reasoning there. It still is an observation (and a condition for our universe to like it is) that the universe was in a low entropic state, it could have been otherwise I suppose... — ChatteringMonkey

Yes, but could have been otherwise can mean many things. It could have been a bowl of petunias, for all we know! There is just no sensible way to ask a question in ignorance.

The relationship with the Past Hypothesis is that it is exceedingly combinatorically unlikely to have a low entropy universe. Borrowing Penrose's math, to observe a universe with our level of entropy is to observe a system that is occupying 1/10^10^123 of the entire volume in phase space (possible arrangements of the universe). It's like standing in a room full of coherent texts in the Library of Babel.

https://accelconf.web.cern.ch/e06/papers/thespa01.pdf

Or also relevant for the summary: https://arxiv.org/pdf/hep-th/0701146.pdf — Count Timothy von Icarus

I read the Penrose paper up to that oft-quoted 10^10^123 number and the discussion of gravitational degrees of freedom; I don't know enough to understand the rest. (The Banks paper is too advanced for me to follow.) I don't get Penrose's point. He is comparing the entropy of a region in the early universe with the entropy of a black hole with the same number of baryons. Why? How is this comparison relevant? The universe in the first few minutes after the Big Bang was a hot, dense plasma, so energetic as to preclude gravitational clustering. Lumping a gigantic black hole into the same macrostate makes no sense: that state was not accessible to the early universe (indeed, to the best of our knowledge, it is not a possible state of the universe at any time after the Big Bang). The same goes for the so-called gravitational degrees of freedom, which he infers prospectively from the later emergence of stars and galaxies. To treat those clumpy states, which only become available after the universe has cooled and expanded, as unused gravitational degrees of freedom in the early universe, one must treat the entire block universe as one timeless macrostate, which also makes no sense.

More to the point - and this is the question to which I keep returning - what is the meaning of whatever magic number that you calculate for the initial state of the universe? What does it mean to say that it was special or improbable? For it to be special there has to be some generic way for it to be. Whence the idea of the generic initial state? For it to be improbable there has to be a stochastic model of the initial state, which for the present purposes we do not consider.

By contrast, here is an example where such notions make good sense. The generic state for the air in your room is to be uniformly distributed throughout the room, as opposed to, for example, being condensed in one corner. That is easy to understand, given that in a stable environment air molecules have plenty of time to cycle through myriads of configurations. Only a tiny fraction of those configurations correspond to special states, which means that seeing those special sates is generically unlikely on human timescales. But that reasoning is inapplicable to the initial state. There is nothing generic about the initial state. It is unique. It has no history and no mechanism of formation.

I am not sure what criticisms to the Principle of Indifference you are referring too. The ones I have seen are arguments about model building and the need to implement Bayesian methods when there is not a case of total stochastic ignorance , which is not the case vis-á-vis the Past Hypothesis. — Count Timothy von Icarus

It's not the criticisms of the PoI as such (although there are some, e.g. Norton, "Ignorance and Indifference") but of its thoughtless or even nefarious application. In hypothesis testing we are supposed to compare the predictions of the new and improved theory to the current consensus - the null hypothesis. Picking unrealistic distributions as representing the null hypothesis amounts to strawmaning.

In the case of the Past Hypothesis the situation is even worse, because there is nothing even to strawman. We do have stochastic ignorance if we bracket out theories that go beyond the established Big Bang theory, such as Inflation, since that is the context in which the question was originally posed.

If you encounter a phenomenon of which you have no previous knowledge, what are you supposed to do? — Count Timothy von Icarus

It depends - see my previous reply.

Right. So did the expansion take place in order to facilitate the evolutionary process? Or was the initial state itself actually metastable? Perhaps the idea of a closed system is inapplicable? — Pantagruel

The initial state was unstable due to the structure of spacetime - that's how the theory goes. The universe was set to expand from the get-go. It is (assumed to be) causally closed, but the interesting thing about relativistic spacetime is that as it expands, its energy content increases. This is a point of disanalogy with the expanding vessel.

I am wary of elaborate analogies given in lieu of an argument. Give me the argument straight, then illustrate it with an analogy if you like, and I'll be the judge of how relevant and helpful the analogy is. So, I'll be honest, I skipped to the end first to see what the moral of that analogy was supposed to be, and then went back to read it.

My problem with this is that it consigns areas begging for inquiry to the bucket of things we just accept for the trivial reason that it is clearly possible for what we observe to exist. Our aliens might never figure out they are seeing a language, let alone what the messages they observe mean, but I certainly think they can find something out about these "brute facts," which presupposes that they be analyzable using probabilities. — Count Timothy von Icarus

And... I am afraid I am still not getting your point, even after reading the alien story.

A puzzling phenomenon found in the world is not a good parallel to what we have been discussing. Such a thing would invite the same sort of analysis as we apply to everything else: that is to say, we would try to put it in the context of our accumulated knowledge about the world and try to reduce it to some aspects of that knowledge. (I am loath to get into an argument over an analogy, but briefly, one problem with it is that it biases the story by stipulating that the phenomenon is literally "out of this world" and causally inexplicable. But your hypothetical aliens would have no reason to assume that.)

By contrast, the initial conditions of the Big Bang universe are necessarily inexplicable within the context of the Big Bang theory. Note that I am not saying that they are necessarily inexplicable tout court. It's just that if you have a causal theory, then the very structure of the theory dictates that it unspools backwards from the present observations into the past, and its initial conditions (or conditions at infinity, as the case may be) are where the theory runs up against its limits. Here be dragons. Here be the explanatory terminus. Here be brute facts.

A theory that goes beyond the Big Bang (and we have several candidates, starting with Inflation, which by now is almost as established as the Big Bang) would explain the Big Bang conditions, but it would in turn run up against its own limits.

You could also posit an explanatory terminus somewhere besides the structure and its boundary conditions. Indeed, you could posit the existence of observers as an explanation of some features of the structure and the boundary conditions, rather than the other way around, as in a traditional causal theory. This approach has an idealist ring to it: our own existence is the one thing we are most certain about, so why not put that at the foundation? I do not endorse this approach, but I think it has a right to exist.

Would it be fair here for the aliens to assume that the arrangement they observe is extremely unlikely barring some sort of underlying logic to the portal's outputs? — Count Timothy von Icarus

I don't see how. Under the "null hypothesis" that the symbols are drawn randomly with a uniform probability from a pool that includes all and only the symbols that they have observed - yes. But what would be the reason to posit this null hypothesis? (Don't say "principle of indifference" - that's an epistemic technique, not a scientific or a metaphysical principle.) And yes, I am aware that in experimental science significance testing often resorts to positing a uniform distribution as the null hypothesis, but this practice is justly criticized.

I mean, I get the underlying intuition: you observe patterns, as opposed to chaos - you hypothesize a causal mechanism that would neatly explain your observations and integrate that explanation at a minimal cost into your noetic structure. That's how science generally works. OK, so how does this relate to the Past Hypothesis?

There are all sorts of interesting things to consider here. Given the aliens can never know the origin of the patterns, that they are separated from that knowledge by an epistemic (and maybe ontological) barrier, would it be fair for them to assume said patterns are just brute facts? — Count Timothy von Icarus

That's not really a question, is it? The answer is given in the premise.

Would it be justifiable to posit that the observed phenomena was some sort of language? — Count Timothy von Icarus

You could hypothesize this, sure. A computational linguist could probably say more.

I used that thought experiment because I think it's a neat idea. More to the point though, there are tons of areas where we essentially have no clue what sort of frequency we should expect for variables. The early universe is in no way epistemicaly unique here. Keynes was thinking of just this sort of scenario when he developed the principle, and Jayne's was thinking of similar cases we he expanded on it with the Principal of Maximum Entropy.

Maybe someone will pull a Quine on these ideas, but these seem grounded in mathematical logic, not the particularities of any particular observation. So, I would apply the concept here. — Count Timothy von Icarus

OK, can you say more - specifically, in relation to the Past Hypothesis? What is the meaning of probability in this context? What conclusions could we draw from it?

Russia has been and one can argue is still a colonizer: there are parts that it annexed through force in the 19th Century just as other European colonizers were doing (starting with Chechnya, that was occupied as late as 1859). China has had some ports colonized, but never has been colonized (the Mongol Horde didn't have colonies). — ssu

Russia has been an empire since before there was The Russian Empire, and through all its name changes. It continued expanding its domain through 1940s, when it swallowed up some lands to the west and effectively colonized others. And then the empire collapsed in 1980s-1990s, when first the Warsaw Pact countries broke off, followed by the Soviet Union republics. (It should be noted that Russia, led by Yeltsin, was the main driver of the Soviet Union's demise. But that sentiment didn't last, and soon ressentiment prevailed.)

Now Russia is fighting a classic imperialist war of aggression. Empire nostalgia is rife in the Russian public sphere, and Putin likes to compare himself (favorably) to Catherine and Peter, and revels in his territorial conquests.

I remember seeing a broadcast of Putin at some meeting answering questions from his fawning underlings. One of them, a retired prosecutor, had a rather long and convoluted question with a self-serving proposal wrapped inside. Putin, looking bored and distracted, obviously wasn't paying attention. But he perked up at the mention of "new territories," and when it came his turn to speak, he latched on to that. With a twinkle in his eye, he remarked how the Sea of Azov was now Russia's inner sea, an achievement that eluded even Peter the Great.

From a systems perspective, subsystems leech energy (negentropy) from their parent systems. So if entropy were ever at a "universal maximum" it would be theoretically impossible for any subsystem ever to emerge. Since cosmic evolution is manifestly systemic evolution (concurrent with the emergence of new dominant laws) entropy would have to be at an initial minimum. Either that, or the entropy of the universe would have to change over time. — Pantagruel

Here is a rough analogy from school thermodynamics. Consider an insulated vessel filled with gas at a thermal equilibrium. This system will remain stable forever and nothing interesting will happen there, as you rightly note (barring Boltzmann brains and such). Now suppose that the walls of the vessel expand outward. The vessel is no longer at equilibrium, even though it started out in an apparent equilibrium state (that is, if we don't take expansion into account).

You seem to be disagreeing with the past hypothesis, in that it wasn't low entropy, but maximum entropy? — ChatteringMonkey

I am not disagreeing with the low(er) entropy part. The space that is currently occupied by the observable universe was at a much lower entropy 14 billion years ago (it had better be!) Was it at a maximum entropy? That's a trick question. I would say that, in a limited sense, it was.

I guess the question is not whether it was likely or not, but whether it was low entropy or not (low entropy is unlikely by definition) — ChatteringMonkey

Ah, see, I actually don't agree that "low entropy is unlikely by definition." That is true of closed systems that have been evolving for some time. As per the 2nd Law of Thermodynamics, the entropy of such systems should be increasing over time. But we are talking about the initial state, which does not have a history. In response to this @Count Timothy von Icarus invoked the principle of indifference. I object that we cannot get a free lunch from the principle of indifference: it cannot teach us anything about the physical world. And conclude that statements about how probable/special/surprising the early universe was are not meaningful absent a theory of the universe's origin that would inform our expectations.

Added to that, (as also notes), the fact that, in absolute terms, the entropy of the early universe was much lower than it is now doesn't tell us all we need to know: there are other factors to consider. And the elephant in the room is that, although we typically assume that the universe is thermodynamically closed, the undisputed fact is that it was never stable: it has been constantly expanding. And that changes everything.

And if it was the first case (the universe itself explanding) than the past hypothesis isn't "matter was in a low entropy configuration", but "the universe was small". Is a small universe likely or unlikely, without another frame of reference, who knows... so I guess I would agree with you. Probabilities only make sense if you have relevant information. And since we don't, it doesn't. What is the likelihood of drawing the ace of spades out of an undefined amount of cards and with undefined types of cards in the deck? — ChatteringMonkey

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