Boltzmann brain
en.wikipedia.org
en.wikipedia.org
Can anyone explain this bit to me? The formation of biological brains was a multi-billion year climb against entropy. How would a brain form spontaneously without those random fluctuations tearing the constituent components apart?
I’m having trouble understanding the logic here. Random fluctuations don’t imply that any order from those fluctuations can be preserved. The higher order features like brains are path dependent on something resisting those random fluctuations to allow something stable to form, whether that’s an atomic particle, cell, organ, or organism.
IANAP and I don’t know what I’m talking about
A similar concept is how the first replicator RNA/DNA got created as the beginning of life. If RNA can exist in large numbers of random sequences, then a sequence that can replicate itself only has to "happen" once and then life is started and will never slow down but will grow in complexity, as long as the environment can support it.
It wouldn’t really resemble a brain in biological sense of the world because the only stimuli it can and will react to is its own disintegration. It’s hard to justify it even “existing” at all. A “virtual” brain in the sense of virtual particles perhaps, except it seems quantitatively useless.
So it's not necessarily about the "from pure empty space" version of it. This is all just a thought experiment and not intended to be taken literally.
I'll give it a try. This is very much a hand-wave.
tl;dr: Boltzman brains (Bb) from energy gradients: a "formless" high-energy fluctuation in a cold gas returns to thermal equilibrium through a Bb state.
The classical cartoon for a Standard Model of Particle Physics human Boltzmann brain (SMBb) is a cold (too cold for metabolism) Maxwell-Boltzmann gas or soup of atoms which in principle could condense into biological molecules via chains of endothermic and exothermic reactions. The gas is on average too cold for the endothermic parts, though, which essentially means no products comparable to those from anabolism.
From fluctuation theory randomly there will be high-temperature regions which allow for endothermy. In a hot bubble, which quickly cools by dissipation, complex molecules are (briefly) energetically favourable as their formation also lowers, locally, the temperature of the hot spot in which it's embedded.
The Boltzmann brain formed in this way is liable to be cooked apart by the heat of the hot spot outside the small region that cooled as the Bb condensed in it.
You've been wondering about how an SMBb might form. The starting point is a cold gas of photons. In that gas regions with vast amounts of gammas can fluctuate out of equilibrium: this is the hot spot. Particle pair productions and complicated decay chains serve to cool the hot spot (inelastically scattering gammas, among other processes), and consequently forming complex bound states embedded within the super-hot-but-rapidly-cooling spot is energetically favourable. Yes one has to have some luck (or some extra constraint or mechanism) in matter/antimatter asymmetry, which should be encoded in the grand canonical ensemble for interacting particles.
The SMBb will be torn apart by gammas and other radiation in the hot spot in which it is momentarily a cold spot.
One might compare this with a different extremely hot "hot spot" in which complicated states can form briefly. High-entropy pulsional pair-instability supernovae (PPISN) <https://online.kitp.ucsb.edu/online/stars-c17/woosley/pdf/Wo...> (see especially the graph on slide 5) are massive stars whose core rises to pair production temperatures. The pair-production cools the core of the very hot (~ 0.3 GK), very massive star; the cooling means less radiation supporting the star's bulk above the core. Gravitation from the sheer mass of the star itself drives a thermal runaway. However, during the runaway, there will be further cooling via nuclear processes that tend to generate a large neutrino flux. Soon however the star and all the heavy daughter products which condense during the pair-producing phase tend to be violently explosively disassembled.
The "hot spot" for a Standard Model Boltzmann brain might be several terakelvins hotter than a PPISN's core (the SMBb bubble ought to be gamma gas reaching QCD or even GUT temperatures), but won't be massive enough to self-gravitate. Animatter is the least of the SMBb's worries, given all the hotter radiation surrounding the cold spot formed by condensing into the brain itself.
If random event result is any real (i.e. not limited integers and fractions) number from interval 0-1, then no number will appear twice even after infinite number of throws.
Open question surely follows: Time and space, are they integer or real?
And the bizarre thing about this is you can't say "oh look, I've been in existence long enough to type this sentence, so I and my memories and reality must be real, and not just a random spontaneous formation of a brain", because at every single instant, you could be that brand-new Boltzmann brain, never before formed, and the bits where you thought "oh look, I've been in existence long enough..." are just the memories spontaneously implanted into that brain.
It's kinda wild. I'm not sure I buy it as a realistic possibility, but it can be fun (or terrifying) to think about.
In terms of philosophy, what's here that can't be found in, say, Descartes or Hume?
It does give a technically detailed construction for how such a scenrio might come about though, as you say, so it can be interesting to think about.
That doesn't matter if BB is just a bridge for physicists to a deeper understand of philosophy. But I have a sneaking suspicion that BB is part of a basket of ideas in a kind of bubble category of "Philosophy for the Scientist." Similar to those "101 Jokes for Golfers" books-- I mean, fine, but if those are the only jokes you know you're probably insufferable at parties.
Rather, when you do the math on all the billion/trillion to one shots that are definitely happening, every second of every day, in physics - and look around at the universe as it appears to exist now and how many of those shots had to play out in a specific way - and then do the math on the probability of a BB spontaneously existing, then it’s really absurd that we aren’t somehow BB’s.
Landau and Lifshitz vol 5 <https://en.wikipedia.org/wiki/Course_of_Theoretical_Physics#...> is the standard textbook. There's an older copy on the Internet Archive <https://archive.org/details/landau-and-lifshitz-physics-text...>. (Having the background of L&L vol 9 makes a classroom demonstration even easier: a small handful of electronic parts for a resistive-capactive low-voltage DC electric dipole, a decent oscilloscope or other apparatus to measure and record fluctuating voltage, and a thermometer).
The probability of an out-of-equilibrium structure spontaneously fluctuating (briefly!) into existence depends on the complexity of the structure, and Boltzmann brains are much much much less complex than the whole Earth, solar system, Milky Way, or the early universe in which these structures' precursors originated. So therefore any theory compatible with statistical physics in which the early low-entropy state of the universe is a fluctuation in a higher-entropy "gas" is imperiled.
For the philosopher or two who wrote comments above in this thread, https://plato.stanford.edu/entries/statphys-Boltzmann/ is probably of interest.
I have studied and reflected on the subject and I really think Boltzman brains and Schröedinger cat are thought experiments that go way over the head of their pop sci/undergrad classroom interpretations.
Schrödinger or Schroedinger: it is just you on HN <<https://duckduckgo.com/?q=%22Schr%C3%B6edinger%22+site%3Anew...> who has used "öe", multiple times.
Boltzmann brains have nothing to do with Schrödinger: statistical mechanics works fully classically, and nobody treats Boltzmann brains in a quantum mechanical way because a Boltzmann brain is an unembodied ephemeral human brain. Natural human brains have a history of being warm and electrically noisy (any quantum features decohere faster than thought), while fluctuated-out-of-equilibrium human brains aren't around long enough to have their temperature measured, nor to produce much electrical noise.
A quantum-mechanical Boltzmann brain emerging from a gas of photons in (cold) equilibrium in which fluctuations take photons out of equilibrium and into the farrrr UV is going to be on the short-lived end of Boltzmann brains: things like annihilations and complicated decay chains will dissolve them away quickly. Which is the point. Boltzmann brains, unlike the bowl of petunias in The Hitchhiker's Guide to the Galaxy, should not have time to compose poetry.
Very hot thermal radiation is what destroys classical Boltzmann brains. They sort-of are a cool spot in an extremely violently hot bubble in an otherwise cold (colder than brains!) gas of almost everywhere uniform temperature.
> Yes I am familiar with the physics ...
> Quoting a university [physics] textbook on a philosophical argument
... which is philosophizing about actual physics ...
> is an interesting choice.
Well, what textbooks or other sources do you rely upon when philosophizing about fluctuation theory? What have you read or taught from?
> pop sci/undergrad classroom interpretations
?
Undergrad textbooks are not exactly cutting edge philosophy wise and you're giving me a "?" for using one in a philosophical argument and having it called pop sci/undergrad classroom interpretations, makes me doubt your reading comprehension entirely.
Descartes/Hume are saying that to even bootstrap our understanding of reality, we have a hard dependency on sensory perception. (I mention Hume because he points out that even Descartes' singular ground-truth can't lead anywhere else without linking sensory perception back into the mix.) And when I say "nearly anything" it includes our notions about the laws of physics. (Which, btw, cannot be derived from Descartes' singular ground-truth.)
At best, BB is a restatement of what I wrote with the philosophically irrelevant detail that the BB hypothesis relies on all the same laws of physics we have in common with our universe. But I imagine it's really meant commonly as a weaker claim-- one which takes the laws of physics as epistemological ground-truth to derive an ambiguity about the nature of our reality within that universe.
My speculation is that science-minded people think BB is the most potent thought experiment for the same reason non-musicians might think Pachelbel's Canon in D is the best ever-- they've heard it a lot at places filled with people they admire.
It showcases harmony and contrasting lines in the simplest, punchiest, most pleasing way. It's fundamentally "the good stuff", and untrained ears slurp it up like babies w pats of butter.
The Boltzmann brain is not making some grand statement on ground truth or perception. It's not about intrinsics or perception at all. Boltzmann discussed how the universe, even in a state of 100% thermodynamic equilibrium, may spontaneously end up in a state of non-equilibrium, reducing entropy. The Boltzmann brain was a concept developed by others in response to this theory.
In fact, many theories are such that a Boltzmann brain actually has a higher chance of occurring than all of the billions of years of coincidences which led up to me typing this message out to you.
It's purely an argument of entropy and spontaneous symmetry breaking. The sensory and perceptive states described by the Boltzmann brain only serve to illustrate the point, and are not the main subject of the problem.
Don't forget that philosophy was the first science, and viewing people as "science-minded" (and therefore not philosophy-minded) hurts the scientific legitimacy of philosophy, and also only serves to exclude. Many scientists also have deep philosophical grounding. Many also have deep musical grounding. You yourself are exhibiting a lack of domain knowledge regarding the Boltzmann brain, filtering it through your "philosophy-minded" perspective, so maybe we can dispense with these kinds of judgements and focus on the core argument.
The world is not so black and white, and there is no false dichotomy between people who are "science-minded" and "philosophy-minded". Both follow the same exact scientific method of inquiry.
Additionally, "the same reason non-musicians might think Pachelbel's Canon in D is the best ever" comes across as a strawman. Some people might prefer that piece overall, but it's not a crime for someone to enjoy it. But relatively few probably consider it "the best ever".
But also, who cares? Why judge? I have a lot of favorite modern pieces which are technically inferior to most classical pieces. But as a musician, not just an engineer, I consider sensory evocation to be equally as important as technicality.
Discounting Brain-in-a-Vat (because it's cognitively useless), the problem in a nutshell is that we inhabit a universe which appears (a) to have had a hot dense phase in approximate thermal equilibrium, (b) a future sparse phase in approximate thermal equilibrium, and (c) a whole bunch of structure in between those. Is the structure a fluctuation in (a)? Could (a) be a fluctuation in (b)? These are reasonable questions about which one can ask: is there astrophysical or laboratory evidence available to determine the answers?
One problem is that if (a) (early conditions) is a fluctuation in (b) (late conditions), wherein (a) simply evolves into (c) (complex structure with galaxies and so on) and then (b), what mechanisms could suppress simpler configurations than (a)?
A huge huge huge number of low-entropy Boltzmann brains fluctuating into existence is vastly more likley (on Boltzmann entropy grounds) than an early very-very-very-very-very-low-entropy universe compatible with the standard model of particle physics and the cosmic microwave background and galaxies all over the sky, in which there is a nonzero chance of human brains arising via evolutionary processes.
A tiny change in a Boltzmann brain as it fluctuates into existence could lead to a significant loss of false memory; a tiny change in a maximally-hot maximally-dense phase in the early universe could lead to completely different chemical elements (or none at all).
So Boltzmann brains highlight some metaphysical ratholes one can fall into with respect to the fine-tuning of the (a) state, and have provoked work on how (a) could be so generic an outcome that the evolution of (a)->(c) is "unsurprising". The hard part is coming up with observables which usefully compare a given hypothetical solution and our own sky.
The only reason we can generally agree on the nature of any object is our common evolution and generally the same sensory ability. (but that isn't universal and differs widely across species)
At some point it does boil down to faith that we aren’t in that scenario/it isn’t what is occurring. Philosophically, it’s hard/impossible to fully logic our way out of this kind of problem.
If I can determine a current point (I argue I can), with memories, then remain conscious for let’s say 2 seconds, the chance of me being a Boltzmann brain already dropped to almost 0.
At any point you could say false memories were planted, but this assumes that I am only conscious in an instant, and merely remember previous states. Both research and my own experience seem to indicate it’s not this coherent, and we have a much longer instant of consciousness or ‘moment’.
A Boltzmann brain only makes sense for particular instants thermodynamically, coherency is as good as impossible
>> Over a sufficiently long time
The conjecture here is that a given volume of space must, at some point, randomly evolve into the quantum state you're interested. When the quantum fields align into the same state that a bunch of particles would represent, those particles appear out of the vacuum.
The trick that makes this work is that conservation laws don't apply on very small time scales. That's how virtual particles work after all. The energy can only be temporarily borrowed from the vacuum, unless you pay the energy cost to make that particle 'real' by destroying its virtual pair (see Hawking radiation).
You might imagine TV static, just random visual noise. There's no real reason the randomness can't line up to produce one single coherent frame before decohering. Just imagine that in 3 (or 11) dimensions.
I don't think an antiparticle pair is a strict requirement for virtual particles either. As long as energy is conserved on macro timescales, the universe doesn't really care what state the quantum fields are in.
Besides, even if you assume conservation of particle number, it only has to be eventual conservation. Suppose I borrow some energy from "over here" temporarily and accidentally assemble them into a perfect brain for a second, then they can disperse again, if they like.
A bigger question is, if energy were conserved globally, where exactly did those handy particles come from in the first place anyway?
Nucleated objects could be long-lasting, which blunts the Boltzmann brain (Bb) picture, as under fluctuation theory the Bb is ephemeral and time-reversible. On the other hand, it's historically been attractive to think of the nucleation of a inflating patch of spacetime (with low enough entropy that structure like galaxies might form as it expands and fragments gravitationally).
A Boltzman Brain is basically that but for a quantum system. In the far future, it's suspected the Universe will undergo heat death and eventaully reach thermodynamic equilibrium but that doesn't mean nothing happens on a quantum level. A chaotic system as otherwise thermodynamic equilibrium is still capable of having temporary, localized order without violating entropy.
So over any sufficiently long period of time (we're talking 10^100000+ years here), you'll get all sorts of interesting arranagements of matter. One of these is a localized reality where it or being in it are capable of sentience.. They won't have any conception of the Universe outside of this but, for a time, they will be able to contemplate their reality.
Think of it another way: take a bucket filled with random elements, mix it and tip it on the floor. Do this enough times and one of those bucket pours will be sentient life.
It's "books" are filled mostly with gibberish but theoretically, if running long enough, it will generate books that have not been written yet.
https://en.wikipedia.org/wiki/The_Library_of_Babel_(website)
Example: At random, 2x2x2cm ice cube in center of sun sized star. You can't get from here to their because an ice cube will never form next to heat.
In some alternate reality where atoms materialize in random configurations out of nothing maybe, but that's not our reality where atoms interact with other atoms and that interaction prevents the vast majority of combinations. It doesn't matter if time is infinite.
Quantum mechanics says that this reality. Look into virtual particles.
Of course nowadays the cosmic redshift, etc, make us think that the universe is not eternal but began a short few billion years ago and will end in a big crunch or big rip long before we expect a single Boltzman brain to arise through the random walk of particles.
Bbs are arguments against the early low-entropy state of the universe being a fluctuation out of thermal equilibrium, and of a future universe fluctuating out of the approximately de Sitter state of the far future.
Expanding steady state was an effort to capture the increasing evidence (including redshift relations) in favour of a Lemaître-style dense early universe, and to avoid several problems with ~static universes.
Since a steady-state cosmology has neither an early low-entropy configuration nor a late homogeneous equilibrium state (steady-state means homogeneity & isotropy in time as well as space: the "perfect cosmological principle"), I'm not sure how a BB argument arises in such a model. In an expanding steady-state model, is there some mechanism for making BBs other than to have them appear with the other components of new gas which under self-gravitation fragments into systems with negative heat capacity?
I don’t think we should expect to see them, though, because they are probably very far away in time and/or space.
Also the concept of a winning lottery ticket would seem to require the existence of a lottery game, which would seem to require some sort of society to play it. We are probably not the minimal working example of a society that is able to invent a lottery, but I bet that society is closer to us in complexity than it is to a scrap of paper.
This is the same with all solipsistic arguments, like simulation hypothesis. If the universe is, in fact, an illusion, then how do you truly know anything about the real world? Sure it could be a computer simulation, but there’s no way to know for sure. The parent universe could actually follow different laws entirely. It could be creating a ”simulation” through entirely different methods. Hell, for all you know it could be an evil demon using magic to trick us, because magic could be real in the parent universe. It’s all unfalsifiable.
So it's simply not meaningful to ask about the relative odds of these two positions.
There are only a limited amount of physical states possible in a given volume and given an infinite amount of time and space, all of them will happen an infinite amount of times.
While it is technically possible for that to happen, the probability of the intricacies that make up the iphone's circuits and screen, the chemicals that make up the battery, etc, assembling themselves into a complete and working phone, even on an infinite timeline, is not that high. And it could, in theory, never actually happen, since if there is still time that you can move forward into, there's still the chance that the moment the iphone assembles itself into a working phone lies somewhere in the future, and always will. It could just never happen before the heat death of the universe.
Possibility does not guarantee probability.
that all but guarantees that it would never happen imo... and also shows that we have no clue how the universe actually works, and likely never will
"Infinity" is not the same thing as a "really long time". You can't use ordinary conceptions of probabilities on infinite time scales. If you wait a Graham's number of years, you still haven't even started a small fraction on the way to infinity.
With a Boltzmann brain, there's no reason whatsoever to think that any senses are consistent from one moment to the next or that any action can predictably yield any reaction. It would all just be random.
But then, if we conclude that we must be a BB, there is no reason for the physics of the universe in which this BB exists to be the same as the physics of the universe we experience. Hence, the argument breaks down, because BB are only very likely in the 'simulated universe', but have no reason to be in the 'real universe' (which has no reason to abide by the same laws of physics).
In other words, the assumption that we are a BB, because they are so much more likely, invalidates the argument that BBs are much more likely.
Even if we assume that this universe we observe as BBs is as well the parent universe, it can produce not only human BBs obviously and not only coherent experiences. Complete nonsense is normal here too.
So if a universe allows for BBs (iow, spontaneous temporary observers with state that somehow produces the me-is-observing effect), it allows for all sorts of experiences, and given enough iterations could reconstruct itself and everything imaginable and unimaginable in a sequence of arbitrary length. “You’re certainly not”doesn’t follow here. It may be or it may be not. You’re a human, here, now.
Yet, I observe what appears to be consistency and rules. Randomness happening to manifest in a way that mimics consistency and rules is very very unlikely, probably more unlikely than there actually being consistency and rules.
However, the moment you assume that then it must mean that you yourself are a BB, the argument breaks down. Because the huge probability of BB applies only to the laws of physics of the universe you live in; if you are a BB, the laws of physics of your universe have no reason to be the same as the laws of physics in the actual universe, where the BB exists. Thus, you can make no prediction on the likelihood of a BB arising, since you don't know the physics of the actual universe.
It's not guaranteed we could do that, even in our universe it's not guaranteed, but it's also not ruled out.
It is worth reading the section "Modern reactions to the Boltzmann brain problem" in the article to understand why the Boltzmann Brain is a useful thought experiment.
The notion that one is a Boltzmann brain doesn't really change anything. If you are, there's absolutely nothing you can do about it. So the only sensible thing is to assume that you aren't, regardless of probabilities.
I must say, with Trump, Brexit, war, and more Trump: Well done, folks!
Also, there is at least a connection to experimental physics in that we can measure "virtual" particles (e.g. Casimir effect) and can calculate their probabilities etc. There's no such underlying experiment for God(s) that I'm aware of.
God itself can be supernatural, but feels like it can only affect a limited part of any universe due to the limitations in observer’s mind. If we could expand BB size indefinitely up to the size where it stays coherent (light milliseconds?) then that would basically cover everything that a consciousness itself could experience. This makes God infiniteness sort of redundant and unclear why it would be needed to generate a universe.
This echoes with my vague idea that hypothetical FGH-sized beings are indistinguishable from God(s) whose infinite part could actually create more issues than it might solve.
Iow, we have to define some Continuum of reality for God of omega+ size to operate on, not to mention Proper Class sized God. Our ancestors really overkilled this idea, but little did they know. So maybe we should take its infiniteness as “anything imaginable by an arbitrarily-sized BB” rather than its naive infinite meaning.
The reason I don't agree with the parent comment is because to truly believe in a Boltzmann brain would seem maximally nihilistic.
Many people truly believe in God/gods at their deepest level. While the Boltzmann brain is an interesting thought experiment, I don't think anyone really takes it to heart the same way a Christian believes in Jesus.
Even while I would probably give the Boltzman brain a far greater probability than most, people don't go around telling other people this is all just a momentary, random fluctuation.
As you said, it does not definitively tell us anything about the reality in which that simulation exists other than that it has the same property that we experience of being capable of hosting a nested reality sufficient for supporting consciousness.
Although we can't specify particular aspects of that reality, we are capable of mathematically representing potential properties of universes that have the capability to host a nested simulation. None of this provides certainty, but it provides a basis of exploring possibilities, and actual understanding requires methods beyond the hypothesis of a larger reality.
Physics provides us a lot of ideas about the potential for the nature of reality and methods for testing and falsifying them but is not in itself sufficient. We don't need to find all the answers in one line of inquiry. The holographic principle of string theory is one example of a type of simulation existing inside a larger reality but far from the only one.
Models like the holographic principle can be tested both mathematically and through experiment. Full tests are beyond our current capabilities but not unfalsifiable in theory.
This is like writing code to run a VM to detect if your code is being run inside a VM.
If the answer is no or yes it doesn't really say anything about whether the parent machine is running a VM with your code inside.
The results of the experiment wouldn't say anything about the simulation hypothesis.
The simulation hypothesis follows a similar logic with one less data point. Knowing that experienced reality could in theory be nested inside a superstructure but not knowing the actual deployment of such nested experiences, we would guess that our experienced laws of physics probably exist inside a superstructure.
What the properties of that superstructure are beyond the hypothesis itself because we don’t have the same knowledge of virtualization of physics as we do of OSs.
String theory is one attempt to describe that structure based on mathematical reasoning. The simulation hypothesis just states that physics is likely to be virtualized inside another system and that it’s worth exploring physics at its limits to understand the properties of that virtualization.
It’s falsifiable through the development of analytical methods that don’t fully exist yet but not theoretically unfalsifiable.
I've chosen not to care; if I'm a BB, or even just a character in a simulation, my life and choices still have meaning to me -- whatever I actually am -- and that's what I've decided is important.
I'll be happy if it happens, but squint-eyes a little that it did.
That might make it unscientific (in Popper's philosophy), but not impossible or implausible.
> As unlikely as it is for a BB to form at all, it’s drastically more unlikely for additional things to simultaneously form around it. And even if additional things did form around the BB, it is not especially likely they will be the kind of stable and sensible objects a brain could even perceive. Therefore, the evidence we have is more likely supposing we are OOs than supposing we are BBs.
which doesn't ring true to me. Assuming that universe is indeed dominated by BBs, it's not at all clear to me that any observations we could possibly make "is more likely supposing that we are OOs". While the number of BBs "with decorations" would be dwarfed by the number of BBs without, it is still entirely feasible that there are many more such BBs than there are OOs.
I also found their argument as to why all observations shouldn't be considered hallucinations (including "over time", "history of" etc) as a matter of probability to be incomprehensible.
So for example the ontological argument putatively argues for the existence of a Perfect Being but it would seem to work even if you restricted the domain somewhat to something smaller than “all beings”, and so presumably also argues for the existence of a perfect Toaster.
Similarly here, the claim is that in a BB universe, even though countlessly more brains see the exact same stuff as you, there is something about the Bayesian update factor that you all have where you all still should conclude you are not the Boltzmann Brains and the evidence is never enough.
How do you look at that description, and not conclude that according to that argument, Bayesian reasoning is just strictly wrong? Like everyone (more or less) is “it” and everyone (more or less) says “it’s not me!” and everyone (more or less) is wrong and here is our philosopher dusting their hands saying ‘yep! sounds good, solved the problem!’
I believe you're conflating epistemics with decision theory. Sure, the measure of all minds experiencing your current mind-state may be dominated by Boltzmann Brains, with observations that do not correspond to any local state of the world, and which will dissipate momentarily.
But, since your decisions as one of those BB's have no effect, you should make decisions based on the fraction of minds-like-you which are living in a persistent world where those decisions have effects which can, in principle, be predicted.
Boltzmann wrote treatises on philosophy such as "On the question of the objective existence of processes in inanimate nature" (1897). He was a realist. In his work "On Thesis of Schopenhauer's", Boltzmann refers to his philosophy as materialism and says further: "Idealism asserts that only the ego exists, the various ideas, and seeks to explain matter from them. Materialism starts from the existence of matter and seeks to explain sensations from it."
Really well put-together and careful main line of argumentation IMO
You do not need to worry about the argument that you are a Boltzmann brain - https://news.ycombinator.com/item?id=41031300 - July 2024 (1 comment)
Boltzmann Brain - https://news.ycombinator.com/item?id=22079253 - Jan 2020 (149 comments)
Boltzmann Brain - https://news.ycombinator.com/item?id=12152658 - July 2016 (17 comments)
Boltzmann brain - https://news.ycombinator.com/item?id=6999074 - Jan 2014 (18 comments)
The reasonable things that continue happening each day in our universe would be extremely unlikely if we are just Boltzman brains. Every bit of sensible reality would be coincidental. The very continuance of that reality is an experiment constant proving the falsehood of Boltzman brains, at a rate of oh maybe millions of sigmas of confidence per second.
Now, if you believe the universe came to an initial state due to pure thermodynamic coincidence, millions of sigmas per second is laughably small compared to the chance that a whole universe outside your brain popped into existence, so Boltzman brains are the most believable thing and you should believe in them.
This completes a pretty direct argument: Believing the initial state of the universe was a thermodynamic coincidence forces you to believe in Boltzman brains, Boltzman brains force you to believe reality should collapse immediately, and reality does not collapse immediately. Therefore you simply can't believe the first assumption, that initial state of the universe was a thermodynamic coincidence.
Accepting this is often called the "Past Hypothesis". It's spoken of in deferential terms and said that it can't ever be proven... But to me this is rock-solid proof, with more sigmas of evidence than any other scientific discovery and increasing by the second! Can't we just call it the Past Theorem already?
> and reality does not collapse immediately
How do you know that reality does not collapse immediately? At any given instant you could be a fresh brain that just came into existence, all your previous memories which imply a life lived up to this point also formed in that same instant.
i.e. a time stepped simulation, absent external reference, doesn't know how long it's been between the actual steps - could be seconds, could be hours, could be years.
EDIT: Like the real issue with "death" is that it's not "eons on darkness" - which is why I think people get afraid of it (or one of the reasons) - but that actual, literal non-existence is inconceivable even though we all did it - 13 billion years of not-existing in the universe, then suddenly you.
So after you die the same problem re-emerges: the conscious experience of "you" ends...but then from the subjective blink of an eye if something happens to restart that information process just right, suddenly again, you - and it has to be you, and no one else, because if it wasn't then well, it would be someone else - i.e. why am I me, and not my wife or son for example?
You could even live kind of a "life" by randomly popping into existence once every million years in some differrent galaxy, experiencing one planck time and collapsing (and the only thing that connects the instances to each other is that the next instance by random chance has memories consistent with the previous instance).
They could even appear in non-chronological order.
I don't think it's likely, but it's more likely than having the one randomly generated brain experience stuff "in real time".
For a Boltzmann brain there is no real past or future - your reality does indeed collapse immediately and you'll never know it; the idea that 'reality doesn't collapse immediately' is not a verifiable fact, because the only evidence you have to the contrary is encoded in and perceived by your brain...
So if the argument is we're most likely to be such brains, then we are most likely to exist in a haze of incoherence. We don't. Right now I have an experience of a coherent historic memory, intentionality, sensory experiences, all of which make sense in the instant. If I am a random Bolzmann brain none of that should be true.
So we'd have to have a reason to suppose that the minuscule fraction of coherent, consistent random Bolzmann brains are more likely than the occurrence of environments that generate 'actual' brains, each of which may generate many, many such brains.
The runners up are brains in jars and simulation theory.
I feel like a Boltzmann brain knowing that it’s a Boltzmann brain is too good to be true. Might as well make the god of Abraham out of entropy - if you can get a regular Boltzmann brain, why not get the most powerful Boltzmann? Maybe it will take trillions of attempts over trillions of universe births and deaths. But you only need it to work the once.
https://www.preposterousuniverse.com/podcast/2022/06/06/200-...
However, if something fluctuates somewhere eternally, then I'd say that it's possible that this random fluctuation causes a very simple computer to form which is able to update it's state based on some simple rules, which results in complexity, i.e. our universe. This way you wouldn't need complexity to pop up spontaneously, but just a simple thing which is able to simulate a complex thing.
All these numbers are somewhere on the number line. In fact, the slideshow of every creature is on the number line.
Is anything real? Because being instantiated in matter is just another way of animating the slideshow where physics takes care of the transition function.
There are unfortunately no insights to be had in this endeavor.
The article does not go over here the time that such a brain could last for, but given that it's quantum mumbo jumbo, we can again assume something in the times of 10^-43s to 10^109 yr. Which, again, means that such a brain can hardly be said to have ever have existed in the first place compared to the time of it's formation probability. And yes, that means our current universe is in the same 'meh, just round it off' bucket.
Like, we get caught up in the minutiae of this thing's mind, it's perceptions, it's sanity, it's soul (?). But if anything the absurdist thought experiment ends as just a mirror aimed at ourselves, with the void now creeping in behind our hats. What am I? What is perception? What is time? Can any of this ever possibly matter compared to these might-as-well-be infinities? Oh God!
I've put numbers up here, they are very poor estimates mostly. And then I tell you that these numbers are so huge that, very literally, nothing that will ever exist in our universe can be made to understand that far future in which this absurd quantum brain comes out of. That time ceases to have any meaning at all in this not quite so empty quantum vacuum.
So, having looked into this mirror, I don't know what tell you. I'm going for a walk, enjoy the season here, hug the fam, have a coffee, laugh, run, play. The universe has spared us this moment.
The misunderstanding comes from the common, but fundamentally wrong belief, that an infinite universe means infinite possibilities.
Great; these two things are seemingly inconsistent. Which means one must be false. But if either of these is false, it's surprising! Because one is based on our direct experience of ourselves, as you have pointed out, and the other is based on well-established science. So what's interesting about Boltzmann brain (and similar) is that it shows that one part of our body of knowledge must be false. And this ought to motivate us to investigate exactly what it is that we have wrong.
What I want to know is this: will BBs exist in the immeasurably far future? If they will exist, how fast could they possibly think, how long could they last, and what is the limit on their intelligence? Could they comprehend their own existence from first principles? In the short instants that they exist, would they realize how short their life expectancy is?
>Two - based on well-accepted science - is that it is MUCH more likely for you to be a boltzmann brain than not.
We're not each individual BBs (and you're not a lonely BB imagining the rest of us). It's closer to the truth that our entire universe is one big BB that just blipped into existence one moment billions of years ago. If we accept the concept of a Boltzmann Brain at all, then it must be that some configurations of one where parts of the brain are disconnected from each other and each spawns and intelligence... or even just unintelligent matter/machinery. Scale that up to a few billion light years wide, and that's us.
The problem is that if you start with the reasonable assumption that you objectively exist and that your observations are valid, the model of the universe derived from those observations (or at least some otherwise viable models) includes prevalence of Boltzmann brains.
And if you were a BB, you probably wouldn't know it, and how you experience yourself is irrelevant. That's kinda the point. The problem with the BB thought experiment is that it isn't falsifiable, at least not with techniques we have now.
I think there's more and more evidence that we're instead in a 3D reality that's the manifold (surface) of an Event Horizon. We're neither inside nor outside a black hole, but on the boundary of one.
All Black Holes form from matter "falling in" rather than stuff "exploding out", and that's how our universe formed (as a Black Hole, one dimension higher up than normal 2D black holes we see). The general rule is that any N-dimensional reality is on an Event Horizon and will have contained/embedded within it (N-1)-dimensional other black holes (it's a hierarchy).
The JWT also just showed our universe is expanding at a rate that's also inconsistent with our current Big Bang theory, and is off by a whopping 8%. I think the reason we see the expansion is not because of Dark Energy (which likely doesn't even exist), but is because the surface of all Event Horizons only expands over time, or in the case of a 3D (excluding time dimension) Universe we see more and more of volumetric space forming, because it's a volumetric expansion for us, rather than the "area" (2d) expansion on conventional 2D Black Holes.
I also think the surface normal vector (perpendicular) vector, at any point on such a manifold (Event Horizon) will be experienced as a "time" dimension. That's why time is a "special" variable. Thus time only moves forward whenever the event horizon "grows" (due to matter falling in from outside it)
This guy did tho... (he gets into the good part right at about halfway thru)
I think the main issue is that the event horizon of a black hole only exists relative to an observer. They're not physically 'real' objects but just theoretical mathematical limits we can calculate. They're 'where the escape velocity becomes c'. As an observer approaches a black hole the apparent event horizon shrinks away from them, in a way directly analogous to a geographical horizon.
The fact that CMB lines up with an explosion theory may simply be that Black Holes are mathematically similar to explosions (i.e. starting small, and growing spherically)
Regarding Event Horizon surface, I say there's something like wave-particle duality going on with this observer v.s. observed paradox. The EH is both a 'surface' and 'not-a-surface' depending on your perspective. Physics is odd enough for these kinds of paradoxes, when there's equal evidence for both viewpoints.