Boltzmann Brain
en.wikipedia.org
en.wikipedia.org
Instead, one way to address the confusion about whether you're a Boltzmann brain or not, is to realize that in the case you're a Boltzmann brain, none of your thoughts or decisions matter at all. Even if you admit there's some probability that you're a Boltzmann brain, there's no use factoring it into your decision processes besides as a curiosity. Your decisions only matter in the case that you're an actual human, so that's the only possibility worth considering while coming up with decisions. (Similarly, if a coin was going to be flipped in a moment, and a bunch of things depended on which way the coin landed, including that you were going to be immediately executed with no possibility of escape if the coin landed on heads, then all your plans for the future should be exactly the same as if you expected the coin to land on tails with 100% certainty. It's the only path that any of your decisions matter.)
In theory, just as it can be argued that it'd be more thermodynamically probable that a single brain would occur than an entire universe - what about a single quantum computer running a simulation of such a universe?
But why even necessitate the physical at all?
Could there simply be a Boltzmann simulation - a collection of abstract information and rules representing a multi-dimensional physical universe? In particular, if it contained techniques internally similar to procedural generation, a great deal of abstracted information could be represented by a much more compact collection of algorithms and rules.
Of course, some might even take the concept further, reducing from a Boltzmann simulation to simply a Boltzmann architect - a purely information based intelligence capable of creating and sustaining such a simulation without the need of any physicality at all, and spawning off child threads to extend that property of "consciousness."
Such a foundational basis for existence (in either the ontological spontaneous simulation or intelligent designer cases) might both be argued to be more likely to occur than the massive physical universe itself.
>Of course, some might even take the concept further, reducing from a Boltzmann simulation to simply a Boltzmann architect - a purely information based intelligence capable of creating and sustaining such a simulation without the need of any physicality at all, and spawning off child threads to extend that property of "consciousness."
I guess the concept of 'pure information' or 'abstracted information' is where I start to get confused. You'd still need that instantiated on some physical medium. A bunch of hydrogen atoms (or whatever) would have to jostle into place to represent the needed information, right? Unless this is a variant of a Kalam cosmological argument that takes minds to be different from, and simpler than, physical things? Or is this non-physical 'stuff', and if so, does that non-physical stuff get subjected to the random jostling the same way as physical stuff?
>and sustaining such a simulation without the need of any physicality at all, and spawning off child threads to extend that property of "consciousness."
And where are we here? I'm not clear what physical medium the intelligence/simulation/pure information is on, or if there's no physical medium, I'm not clear on what way the intelligence/simulation/pure information is popping into existence or what it means to spawn child threads. Maybe for your purposes physicalism is entirely assumed away at this point?
Then there's the 'foundational basis for existence' which I think departs from the terms of the original thought experiment, which presupposes that a certain kind of universe already got there, and that Boltzmann Objects are already busy poofing into and out of existence within it.
Though I take your more general points that (1) there's a whooole taxonomy of Boltzmann "objects" that can be imagined and (2) among those objects, some of them will be relatively simple and make for interesting considerations about what's most likely to poof into existence.
Why do you say that decisions matter if you're a human? At least, why would decisions matter more as a human than if you're a Boltzmann brain?
For example for a Boltzmann Brain with a similar chemical composition as ours the speed at which chemical reactions occur would limit the speed of experience.
For a Boltzmann Brain that simulates ours with a very different physical substrate the speed of light would still be a limit.
While probably not entirely in the spirit of your question, I would emphasize this part of the wiki article:
>Like any brain in such circumstances, it would almost immediately stop functioning and begin to deteriorate.
I think if you pause long enough to consider whether you're a Boltzmann brain, you've probably lasted longer than one and aren't one.
In other words, take a real human considering whether they are a Boltzmann brain and deciding that they are not. Any single moment in that human's existence can be simulated by a Boltzmann brain existing momentarily, including the moment where the human concludes that they are a real human, and the moment where the human reflects on its conclusion that it is not a Boltzmann brain.
But each variant of a boltzman brain that accounts for the passage of time, passes that 'test' at the cost of being less probable overall. Most boltzman brains won't pass that test, but some will. And then you throw in the other tests people have mentioned: a feeling that your memories are somehow internally coherent and consistent. Most won't pass that test either, but some will. And 'some' could be so many that, if you were picking out of a hat, they are still more likely than that your experiences have really happened.
I guess the interesting question is whether you can collect together enough 'tests' that filter out BBs, that you can pare down the range of possible BBs that pass the tests, to the point that they become a less probable explanation than the actual spontaneous emergence of life in the universe.
And of course probability doesn't matter for events that occur only once in the universe. This isn't a scientific theory.
And if we've thrown that core reference frame out the window we've stepped entirely outside of the rules that are the basic structure of the whole boltzman brain thought experiment.
If it is infinitely more likely that I am a Boltzmann Brain than not, isn’t it also extremely more likely that I’d be one with any number of random memories rather than a group of memories that form a more or less coherent whole?
Why do you think that? A Boltzmann brain will immediately start to degrade but that does not mean there is zero time for thought.
If I were a Boltzmann brain, I would spend most if not all of my existence dwelling, contemplating, ruminating over the things that took me to my current point in space and time. Then I would quickly type something up and post it on a forum to confirm that I
Of this range of possibilities, ones giving you a seemingly coherent and ordered timeline of experiences, or one that is disordered but close enough to order that it can be readily can be interpreted as ordered, would appear to be more improbable.
>on that small of a timescale, your existence is really just a single instantaneous snapshot of a state of mind, and there’s no time to recall a sequence of memories or think through logical propositions.
I think this is very true. Even being around long enough to pose the question to yourself gives you reasonably strong confidence that you've 'tested out' of being a boltzman brain. Though I think that consideration is being momentarily set aside for purposes of this variant of the thought experiment.
Coherent memories are the convergent result.
> my memories are chronological and all feature me as the self
I’m not sure exactly what you mean by this, but the way I read it, I disagree with this as a description of human memory.
All my memories point to be me being not just human, but a particular human. In every memory I have, I am male, human, on Earth, live in the United States, live between the period of my birth and now. Speak English. Have the same number of siblings. etc. There's a more or less consistent story there.
And the story is chronological. You could argue that the timeline of events is arbitrary and my brain is just remembering them in the order of that makes sense. But I also have memories of remembering things, and in each one of those, I am remembering things that happened before the time I am remembering them.
The odds against a Boltzmann Brain having even two random memories that relate at all are incredibly small. The ratio of ordered:non-ordered Boltzmann Brains would be roughly on the order of actual Brain:ordered Boltzmann Brain. That's true even if we include a little wiggle room for the way the brain deals with memory.
The likeliest scenario is then that we are not Boltzmann Brains and any explanation of the universe that includes the probability that we are Boltzmann Brains is probably wrong in some way.
I often have perfectly clear memories that don't fit into any cohesive story. I reject them under the assumption that they're a dream leaking into my waking subconscious, or neurons going crazy, or whatever. (If this were a sci-fi movie, they might be critical foreshadowing!)
I wouldn't describe memories as inherently chronological. They're an unordered heap, with various indexes. Time is one such index, but a weak and incomplete one. I often misremember the age (or relative age) of events. Location and mood are much stronger indexes.
I haven't had any memories of being a Martian, true, but given that there seems to be some automatic filter already (most dreams don't become memories), it doesn't sound unreasonable that my brain has a GC of sorts. Perhaps my filter threshold is set too low, but still high enough to reject the Martian memories.
I agree that Boltzmann Brains are not the most likely explanation, but reflecting on how my memory works doesn't seem to be a good argument against that scenario.
My memories aren't entirely internally consistent. Memories fade over time, too, so even if they formed perfectly, I certainly misremember many events. The earliest ones are from when I was a kid, when I didn't understand the world, so I naturally place the least faith in their accuracy.
When I do have conflicting memories, I use logic and common sense to try to figure out which is correct, and hedge my bets against memories which might be false.
So if I were an intelligent brain formed with random memories, over time my natural tendency, in order to remain sane, would be to correct my memories to be internally consistent, as much as needed, and not examine the rest too closely.
If you're allowed to put more weight on specific extremely-improbable sequences of Boltzmann brains, then you can propose all sorts of nonsense scenarios like "Imagine the series of Boltzmann brains where if one thinks of a purple elephant, then the next Boltzmann brain experiences the subsequent thought but also a lot of pain. Should you avoid thinking of purple elephants because of the fact this unordered sequence will happen eventually in an infinite universe?".
I think in order to really reason about this sort of thing, you need to start considering theories of the universe like UDASSA (https://news.ycombinator.com/item?id=20119513, http://fennetic.net/irc/finney.org/~hal/udassa/), which provides a framework for how we should expect to anticipate different events, and Boltzmann brains and especially specifically-selected sequences of Boltzmann brains have so little measure compared to other things including our human selves that they're not worth considering, even if their decisions actually did have a causal effect on some part of a world (which would also have minuscule measure compared to ours).
This is similar to the premise behind the novel Permutation City, except that it’s not just one brain, but an entire virtual world.
They weren't running "on dust", they were running in the simulation of some being that's particularly interested in universes that embed simulations of sapient beings. Such as their own, and then later the "experiment"...
And you could reason that because you observe your reality, then the only series of boltzmann brains that could comprise you are those that sequentially form consciousness.
You would never experience any other configuration.
I think this finally explains current pop music to me.
Justin Beibers pooping into existence...
> Typically, a quantum Boltzmann brain would suddenly appear from the vacuum (alongside an equivalent amount of virtual antimatter), remain only long enough to have a single coherent thought or observation, and then disappear into the vacuum as suddenly as it appeared.
Could a consciousness comprise of just a single, false perception— that there are further memories and perceptions? What would it take for such a "mind" to manifest in our universe?
Probably almost nothing; I can't imagine the difference between this and an inert object, or even an instantaneous event. It has no real memory, so it doesn't need to exist for more than an instant.
(Uh, you can stop reading here if you want. Just a warning.)
This has some parallels to Bill Gosper's "HashLife", an implementation of Conway's Game of Life that effectively hashes every event at every scale and timescale. The simulation accelerates rapidly by skipping events whose cause and effect are already coded into those of larger events, and so on, up and up and up; every portion of the simulation ends up being a key for a value in the cosmic hash table. So who's to say what in the simulation is real, and what is symbolic of something more complex?
I’ve always found any participation in this debate to be meaningless for reasons that last Thursdayism illustrates, but kinda misses at the same time.
Any debate has to take place within an agreed upon set of axioms, if you don’t have that then any point raised by the other side is simply invalid no matter what. “Earth came to be naturally billions of years after the Big Bang” and “God created earth 6000 years ago” or “Earth came to be last Thursday” clearly don’t share any axioms on which to found a meaningful debate, it’s simply impossible.
I also think it’s not necessary. If you believe earth was created last Thursday, instantaneously summoned into existence in a predetermined state (something you would expect an omnipotent being to be capable of), then studying the state of the universe is a still perfectly valid exercise. You can study what present day information reveals about points in time prior to creation, without compromising your faith that the universe was created last Thursday. In fact a th(ursday)eologian might argue that such study could further resolve your faith by revealing the intricacies of last Thursday’s creation.
Another point (though not directly related to the young earth variety of creationist) is that if you have an omnipotent being, then you would expect such a being to be able to both: Summon the universe into existence in any state it wanted to, or if it preferred, initiate a Big Bang with the precise conditions required to eventually lead to any exact state (for instance the details of Islam’s creation story describe the latter scenario, according to some interpretations).
Having axioms is not a problem if the parties are prepared to reconsider them. At the time Omphalos was published, there were people who were genuinely prepared to change their minds -- Darwin himself started as a creationist (interestingly, his grandfather Erasmus Darwin, an influential scholar in his own right, was an evolutionist, and drew the analogy between domestication and evolution that was helpful for Charles) -- and the fact that Gosse was ridiculed by creationists suggests that the debate had not ossified. These days, all the arguments have been made, and the only sensible course would be to agree to differ. I think most evolutionists, aside from Dawkins and a few others, would be happy to leave it at that, if it were not for the repeated attempts by creationists to subvert education.
More specifically, “Earth came to be naturally billions of years after the Big Bang” is not an axiom, it is a conclusion drawn from evidence, and the axiom is more like "physical evidence never lies (even if it can be misconstrued)." The creationist axiom is more like "This book never lies", and “Earth came to be last Thursday” appears to be a tongue-in-cheek and apparently counterfactual claim made to trigger debate.
> These days, all the arguments have been made, and the only sensible course would be to agree to differ.
Perhaps, but I’d say we just understand enough today to know when different ideas are trying to answer different questions. If you generalise science to be a method of explaining the nature of the universe, as we observe it, then I don’t think it’s a contentious point to say that religion generally attempts to answer a completely different set of questions, ones that cannot be explained with science. A religious answer to a scientific questions is equally as irrelevant as a scientific answer to a religious one, and even when they’re in contention, the contention is really only superficial. If you believed the universe was created last Thursday, that wouldn’t necessarily have any impact at all on the nature of the universe we observe today.
they share a lot - for example both agree that currently there is "earth" which is the point where the "Boltzmann Brain", "Rene Descards malicious demon" and all other variants of "simulated reality" theorems come in. Those refute the existence of earth, and share the "consciousness in a box" idea, yet they can still argue with the aforementioned creationists and evolutionists, because all sides have the common believe that there is, at least, a consciousness that thinks that there is "earth".
> if you have an omnipotent being
you can really piss of creationists by sharing their believe in the existence of a creating entity, but refuting the idea of it being "omni-scient/omni-potent" or even the least bit competent. Think about it: there is ample evidence that life, the universe and everything else was created as a sixth year school project and has since been abandoned by its creator.
I think a very short conversation with any physicist could straighten that one out for you. Go and google any examples of constants put forward to support a fine-tuned universe theory, and tell me how many sixth graders you think could conceive their own set of physical laws that would create a stable, life supporting universe.
You are completely missing the point O.o any such discussion would take hours and drive any physicist to the brink of insanity because at some point we get them to admit that they just might be a Boltzmann Brain.
To clarify: i am talking a god like sixth grader and about annoying creationists by ridiculing their believes, why would i even want to talk to a physicist about that?
Yet to entertain the point made: fine tuning is only relevant if the universe existed for longer then last thursday, which it did not, and "fine tuning to support life" is only perceived locally by fragile creatures who, by virtue of not having any other sane option, must believe that the current state they exist in is stable. That is the Boltzmann Brain thing: it leads no where if you assume you are a Boltzmann Brain. In the same way physicists believe that the universe is stable, because everything they do is completely pointless if the rules could change at any moment.
Look at the galactic scale: the universe seems to be degrading rapidly. How is that "stable and life supporting"? An A+ universe would not degrade towards lower entropy. This is a C- universe at best! Then there is that "stuff that randomly starts existing" due to quantum, we are talking about brains phasing in and out of existence by mere chance, does that look "fine tuned" to you? That's just the stupid randomness a sixth grader would create. And then there is the "Elitzur–Vaidman bomb tester" that pretty much shows the math is qwirky.
And finally you tell me, because you believe that your garden eden today looks like you remember it looking wednesday (stable and life supporting) that somehow the universe must be finely tuned? You are a Boltzmann Brain floating in mid space arguing for empiricism :D
However you almost got me with the claim that "physicists believe that constants were put forward to" - that is a sneaky one.
I dunno.
> degrade towards lower entropy
Entropy is increasing, justifying our everywhere-observed second law of thermodynamics. The observable universe is the ultimate closed system, much more so than any laboratory, or our planet, even or our galactic cluster (which, after all, shines brightly). The expansion of the universe is as far as we can measure an adiabatic process.
Although when one thinks of increasing entropy one usually thinks about structures dissipating away from something well-ordered, like a book, to something much less well-ordered like ashes and gas when you burn the book, the universe's entropy is growing somewhat differently. Visible structure is mostly increasing in complexity in the few billion years on either side of "today": gas clouds are collapsing into stars, some with planetary systems, and so on, even as the universe's entropy is growing enormously. How can that be?
The largest sources of entropy growth in the known universe are empty space and black holes. Space has enormous entropy: you can take a million cubic centimetres of space (one cubic metre) and rearrange them in an enormous number of practically identical ways. By comparison, if we start moving cubic centimetres around within you, like a cm^3 of air in your lung and a cm^3 of your heart, most of the time that kills you fairly quickly. Entropy is thus a relationship between the contents of a volume and the number of ways we can rearrange those contents and not make a significant difference: the more ways we can safely rearrange, the higher the entropy.
Modern CPUs are very low-entropy; a sandy beach is much higher entropy. The space between Earth and the Moon is much higher entropy still; and the space between galaxy clusters has enormous entropy. The metric expansion of space creates more space, and that space is also emptier. Thus, most entropy in the universe is being created far from galaxies.
Black holes hide what's inside them according to the no hair conjecture; even if the conjecture is not precisely true, it does an excellent job of hiding what has fallen into a black hole over billions of years, and likely will keep hiding everything but its macrostates of mass and angular momentum (the various possible charges, like the electric charge, tending to neutralize quickly) for trillions of years to come. Looking at a black hole we cannot tell if it was formed from just hydrogen, or hydrogen with some helium, or hydrogen and helium and other elements. We can't tell if it was just gas, or gas and dust that fell in. Because we can make so many changes to what has fallen into a black hole without changing the macrostates of the black hole, the black hole has very very high entropy. The bigger the black hole, the higher its entropy, and probably all black holes are currently growing.
By comparison with a growing black hole or expanding empty space, the change in entropy of the Earth over time is small. Likewise, while the black holes in the Milky Way have enormous and growing entropy, the overall entropy of the galaxy changes very slowly: there is a lot of mass in gas and dust that has yet to collapse into structures like binary star systems, much less into black holes.
If we take the second law of thermodynamics seriously at a cosmic scale and consider any stage of the earlier universe, it must have had lower entropy than later stages. Indeed, we can get that just by removing some of the expanded space, and from shrinking black holes (and removing black holes that formed well after our star did). But in the much denser and hotter universe, the entropy would in this view be very very small.
Items with tiny entropy are pretty rare. Human brains are much higher entropy than a comparable volume in the early universe. Things with higher entropy are much more common than things with lower entropy, in our universe. Grains of sand are much more common than human brains or microchips.
This leads us to fluctuation theory. Even very high entropy systems have small fluctuations to lower entropy within them. Statistical mechanics lets us define a probability of fluctuating from entropy n to lower entropy m. Such a fluctuation is a sudden spontaneous local increase in complexity. This probability falls off very quickly when the difference in n and m grows: a fluctuation into something simple is enormously more likely than a fluctuation into something complex.
Fluctuating from practically empty space to space with a low energy photon in it is of much higher probability than fluctuating from practically empty space with a proton in it. An atom or molecule has even less entropy, so the probability of fluctuating from practically empty space to a gas of atomic or molecular hydrogen is much smaller than fluctuating into a gas of photons. Fluctuating into a computer or into a brain (not necessarily a human one!) is extremely improbable by comparison, because those have lower and lower entropy still. But the entropy of the chip or brain is huge compared to the entropy of the extremely orderly hot dense phase of the universe some 13.5+ billion years ago.
Consequently, theories that cause universes to appear by fluctuating out of a high-entropy state -- say, a new baby universe arising in the extremely far future of our own universe when there is almost nothing but empty space everywhere -- have to suppress fluctuations into relatively high entropy configurations like a handful of photons, or sparse atomic/molecular gas. Human brains are still relatively high entropy compared to the hot dense early universe.
More generally, a proposed cosmology that suffers "an invasion of Boltzmann brains" is probably unphysical, because such a cosmology would also suffer an even more obvious invasion of much higher entropy dusts and gases, and we do not see that happening in intergalactic space.
One could easily substitute "apples" or "Apple Computers" or just random hydrocarbon molecules. Brains are just catchier, because brains are obviously much more complicated -- and thus much lower entropy -- than soot, although both are almost the same entropy compared to the early conditions of our own universe.
Arguments about what a Boltzmann brain thinks are misplaced. The point is that there isn't Boltzmann soot, much less Boltzmann brains, so we can bet that our early universe likely did not appear as an extremely low entropy fluctuation in an extremely high entropy vacuum. We can also bet that our future universe is extremely unlikely to "give birth" to anything as low-entropy as its own early phase. It will be cold and sparse and fluctuations in the increasingly empty space probably won't even rise to the level of ELF radio, much less soot or brains.
> fine tuning
is a somewhat different concept. There is a measure of entropy even given only one physical universe to examine; it's the log relationship between macrostates like galaxy clusters and microstates like the contents of cubic micrometres throughout the universe. There is no measure of fine tuning within one physical universe. If you had lots of universes to look at you could build a distribution of some parameter and consider whether that parameter in one chosen universe was finely tuned compared to the others.
> the universe is stable
It's not. It has a finite age with extremely distinct eras including one dominated by radiation, one dominated by matter, and later ones where the matter on the largest scales is increasingly diluted away. On smaller scales, matter is condensing chemically and collapsing gravitationally. The universe of the past looks remarkably different from the universe close to now, and the universe of the future is virtually certain to look even more different.
> the rules could change at any moment
Some rules, like those of electrodynamics or the Standard Model are known to change at extremes of energy already; we can show this in laboratories and have ample observational data from supernovae and their remnants. That fluctuations from ordinary energies to extremes of energies don't seem to happen anywhere we have looked is an argument against Boltzmann brains, true, but doesn't really say anything about the global applicability of our most fundamental theories (General Relativity and the Standard Model).
> You are a Boltzmann brain floating in mid space arguing for empiricism
I think you have to add the constraint that the brain in question is hallucinating that it is something else.
However, the exact nature and experience of a Boltzmann brain is not really physically (as opposed to philosophically) relevant. What's relevant to phsyical cosmologists is that a Boltzmann brain is much lower entropy than empty space (or even giant molecular clouds), but much much much higher entropy than the earliest part of our universe reasonably describable with General Relativity.
or it may have been just restored from a backup (with some bit rotting and missing pieces as evidenced by dark matter/energy and other inconsistencies)
https://www.researchgate.net/publication/258201870_Lucid_dre...
This explains why "Berenstein" is now spelled "Berenstain".
> “Reformed Last Thursdayism,” a.k.a. “Next Thursdayism”: the belief that the world will be created ex nihilo, complete with fossils and cosmic microwave background and other signs of apparent age, next Thursday, and that we currently inhabit the precomputation.
(https://a-point-in-tumblspace.tumblr.com/post/187371750052/)
I thought the whole point was to give a simple metaphor for a measuring the probability that a mundane object came into being based on the widely accepted history of the universe that modern physics predicts. As opposed to just coming into its current state instantaneously based on extremely unlikely random events among its constituent atoms.
Or put differently (based on the Wikipedia article), if the math behind a modern physics theory means that it's more likely the given object's existence was due to random fluctuations then that's a strike against adoption of that theory.
But if you make the object of interest a brain you get all this bikeshedding about consciousness and how do the regular brains know they're not Boltzmann brains, etc.
It'd be like introducing me to your new programming language's syntax by showing me the code for a quine instead of "hello world." What is the value in doing such a thing?
Now, a Boltzmann universe would cater for that - spooky thoughts at a distance :).
The Boltzmann brain hypothesis postulates that your perception of the past may just a randomly arranged hallucination - just a random set of memories that happened to be encoded in your brain's neurons during it fleeting moment of consciousness.
I don't believe that there is any experiment that can disprove this particular flavour of solipsism - as you cannot reliably trust any memory or sensory input.
(Anyway I don't think your experiment is valid: it's perfectly possible for a Boltzmann brain to have the memory of just running that experiment and believing that it's proven it's not a Boltzmann brain.)
Myself I have not done that, not at least in that way, but every signature on every aged document thru times arrow does support that.
But as a thought experiment, it's good, but resolves around a snapshot instance of time as decay precludes any more. So why do things we remember and `know` work forward and never in reverse. Time always moves forward and how you would resolve the Boltzmann brain with https://en.wikipedia.org/wiki/Arrow_of_time makes for an even larger thought experement.
Hence a Botzmann Universe expands beyond a brain and into a collective of brains and matter. With us a small substruct of that whole, the decay would be slower and the posibility of time at that lower scale becomes plausable. The Boltzmann brain has decay as a factor of time and as the whole of the brain is needed for conciousnous in this, then any decay would appear instant. Though not all the brain would decay at once, bits would live longer but as not the whole it has ceased to exist. So by expanding that Brain to the scale of a Universe, us human brains would be relative to the scale of the whole. Hence any instant decay of the Universe as a whole would still have pockets which would and could contain whole galaxies. So for the human brain the time until decay reaches them would and could be a measurable amount of time.
Now that as a thought is one that ticks more boxes for me and opens up a larger scale of thought that maybe black holes are that decay in action.
Working on such low-level hardware taught me something about my own mind. When you want to read data from say, a serial port or a camera, you point your program to where in the microcontroller's memory that data has been placed. Serial ports will usually have a dedicated buffer that you can read from a particular address, you see. A camera could also directly access memory and write its data there in your MCU's ram for you to read, at an address that you have a pointer to.
What I learned about myself was that although it feels like I'm looking at a piece of paper with the words "I'm human" written on it, my consciousness main loop is not accessing my eyes, it's accessing the region of memory that my retinas have recently written image data to. A Boltzmann brain would have no trouble with this sort of hallucination.
So if I think of a Boltzmann brain as a universe in that context, then I totally get the point. Thank you.
Assuming conventional reality and physics is as it appears, "you" experience a model of a piece of paper that is constructed by your nervous system (part of your brain presumably) in response to all of the sensory information that you get. This incidentally, implies that consciousness cannot inhabit the whole brain, because if there is an observer, there must be something to observe, but it cannot be reality, because reality has to be mediated somehow.
So I guess I've disproved solipsism?
That mirror is assumed to be accurate, if you aren't hallucinating, dreaming, drunk, or whatever. It must be part of the brain/nervous system, but normally separate from the self. So it seems to me that the visceral sense of God's presence (during religious experience, madness, or both) must be from the self feeling the presence of that part of the mind.
But then if there is something that creates reality within our head and is/is not ourselves, why not a second level - God that created (or creates from moment to moment) the universe? It's not that such a thing must exist, but it just seems like it would be symmetric if it did. And the mirror within provides the compelling feeling that there should be such a thing.
So I'm a Boltzmann brain and so is the piece of paper I'm writing on, and we're the same brain. When we're talking about recreating the states of a brain or a brain in a room they're both Boltzmann brains.
Think of a gas of neutral atoms that has fallen into equilibrium warm temperature over a long, long, long period of time. Being warm the atoms bump into each other, chaotically. Very occasionally the bumps form what to humans would appear to be clusters or even higher patterns. Even more occasionally the higher patterns might monmentarily resemble something familiar and larger scale.
An analogy might be cloud-watching. Swirling changing clouds might look like birds for a little while, before looking like something different.
The Boltzmann brain is a fluctuation out of some unknown equilibrium gas into a pattern recognizable as an adult brain -- with thoughts and memories. Those memories are false ones; they did not form from actual experience, they just fluctuated into existence. The memories won't persist either, as the brain-and-memories will quickly melt back into the hot equilibrium gas.
The argument is that the entire universe as we observe it could be a fluctuation of this sort, only it takes a long time to melt. Various arguments have been presented in the past hundred-ish years which point out that without some means of suppressing smaller fluctuations, one could simply have the solar system with false shells of light falling upon our eyes and telescopes, or a momentary "Boltzmann planet" where briefly the whole Earth in some state freezes-by-fluctuation into existence before very quickly melting back into equilibrium. The Boltzmann brain is just an attempt to find the smallest such system, determine how much less complicate it is than any of the bigger systems (like a persisting universe), and wondering why Boltzmann brains aren't everywhere, including practically everywhere in a universe that fluctuated into existence.
> Matrix only larger scale
It's more like if a single instant in The Matrix was formed after a long long long period of time of filling The Matrix's memory with random values. It's closer to the https://en.wikipedia.org/wiki/Infinite_monkey_theorem -- the monkeys will make fractions of Shakespeare embedded in or peppered with (or both) strings of gibberish. Interesting fluctuations will be surrounded by (included preceded by and followed by) uninteresting ones.
> reconcile the arrow of time
There's no really good arrow of time in a system in total equilibrium. Fluctuations that are momentary do not produce a good arrow of time either. However, if we let things fluctuate into very low entropy states that take some time to decay back into equilibrium, then we can base an arrow of time on that, pointing in the direction of the second law of thermodynamics. One option is to set up some boundary around the region of low entropy that interacts with the equilibrium state outside, somewhat analogous to a cell wall, cellular membrane, or ablative heat shields on orbital re-entry vehicles. A system with a boundary is of course even lower entropy (and thus a rarer fluctuation) than a system that is subject to immediate melting back into thermal equilibrium.
> time always moves forward
Our human experience of time is that it flows in one direction, and that direction is in increasing entropy: we don't see smashed teacups reassembling and flying up onto tables, for example. We also don't see clusters of galaxies rushing towards each other as empty space vanishes. (Empty space is extremely high entropy). We also don't see black holes evaporating at this time (black holes are very high entropy).
We don't really know why there's so much lower entropy -- thanks to the metric expansion of space, and the collapse of stars and other matter into black holes -- in our past, though.
Penultimately, empty space is extremely high entropy because you can rearrange small subvolumes of a large volume of empty space around arbitrarily and it retains all the same characteristics as empty space: empty space is pretty much empty space "all the way down". The real virtually empty space between galaxy clusters expanding apart is still very very very high entropy, even though it has starlight and cosmic microwaves and so forth passing through it. Likewise, you can rearrange things within a black hole horizon pretty much arbitrarily and the outside observer will still determine the same horizon; you only change the horizon by letting things fall in, or waiting for evaporation (and if Hawking evaporation happens, the regions around black holes just emit a high-entropy blackbody spectrum anyway, rather than revealing details of how things inside the shrinking horizon are arranged).
Lastly, returning to the arrow of time: more empty space (from expansion) and more black holes (from gravitational collapse, accretion, and so on) leads to more entropy. So we can build an arrow of time from the past with less empty space & black holes to a future with more empty space and black holes. There are local pockets of low entropy visible in our sky (and on our planet), and while those may decay slowly compared to the metric expansion of space, they're already just a dwindling, diluting fraction of the cooling-and-equlibriating-as-it-expands universe.
No physical anything at all, just organization of energy according to various rules that abstract a physical reality. A pure information based existence that depends on no ontological physicality.
After the discovery of the Hubble constant, the Big Bang and Inflation, it's more razonable a low entropy starting point.
I'm pretty sure the Boltzmann brain paradox is 20th century, likely originating with John D. Barrow and Frank Tipler -- they discuss it in e.g. chapters 6 and 10 of their 1986 book on the anthropic cosmological principle, although afaict the actual words "Boltzmann['s] brain[s]" first popped up in the early 2000s.
Dyson, Kleban and Susskind (DKS 2002, https://arxiv.org/abs/hep-th/0208013) is firmly after the widespread acceptance of the lines of evidence pretty much compelling an accelerated expansion of the universe, for example. Albrecht & Sorbo actually talk about brains and bodies and so forth in 2004 https://arxiv.org/abs/hep-th/0405270v2 : in section "C." they discuss some of the history of the paradox, briefly.
Without a finite age to the universe -- this comes from Lemaître in 1927, rather than Hubble in 1929 -- there is no particular reason to assume that there is a low entropy state in the past. A positive cosmological constant creates more empty space (all of which is very high entropy, because of the indistinguishability of subregions of any region of truly empty space) and thus demands a much lower entropy before the dark energy dominated era. It's the low entropy of the past that's the source of concerns about Boltzmann brains. And a hot big bang is even worse. How did the universe end up in such relatively low entropy? And it must be low entropy rather than a hot dense system in equilibrium, because otherwise one runs into the problem of suppressing Boltzmann brains.
cf. Carroll's deck at https://www.slideshare.net/seanmcarroll/the-origin-of-the-un... starting at or before slide 21. A second deck at https://www.slideshare.net/seanmcarroll/what-we-dont-know-ab... starting at slide 5 is slightly more technical, with references at the bottoms of slides later in the deck. Suppressing an "entropy catastrophe" is very modern hard work for physical cosmologists!
> save the model of a eternal static universe
He didn't know the Raychaudhuri equations (1955, shortly after his death) or the focusing theorems they support, only the Jeans equations (1902), and was trying to suppress a collapse via Jeans mechanisms. Had he known about Raychaudhuri's expansion scalar, who knows where he would have went -- perhaps he might not have discarded his small negative cosmological constant in the aftermath of evidence for the expanding universe, but rather might simply have accepted a small positive value as consistent with the evidence and theory, and we wouldn't have had to wait half a century to get it back in the minds of cosmologists. On the other hand, perhaps we would still have had to wait for the discovery of the accelerated expansion to get to a small positive cosmological constant as a parsimonious explanation.
Finally, this is a really nice way to connect Raychaudhuri and the CC: [Ellis 2007] https://www.ias.ac.in/article/fulltext/pram/069/01/0015-0022
Statistics and probability was not designed for one-off events with specious reference classes. The more speculative the reference class, the more we should doubt any claim of "more likely".
In the case of the Boltzmann brain, given we have no evidence of this ever occurring thus far, we can at very least claim it does not have a clear reference class that we can identify empirically.
If you're a boltzmann brain, then anything you think you know about anything is illusory and based on nothing at all, including the idea that you could be a bolzmann brain.
I think this also applies, although less convincingly, to most theories that the world is illusory or a simulation.
In any case, it doesn't matter because you'll stop existing momentarily.
After all the Sun will swallow the earth in about 7 billion years. I like to think the things we do matter independent of that fact.
Boltzmann brains have no past and approximately no future at all.
Boltzmann brains experience meaning too. Not that is does them any good in the way that it does for biological system.
It's not like we have a planet rich in meaning and then the sun swallows the earth and all that meaning retroactively disappears. It just exists in the past, not the future, and I think that is sufficient.
I always thought it was funny when people thought that the heat-death of the universe had moral implications. Like that killing someone means they never existed, or something.
I don't think this view is uncommon, and I think people get there because they're just not thinking straight, but I don't know what they feel is at stake that they have to hold onto, that gets 'lost' if you accept that meaning doesn't persist through time forever.
It would also be interesting to know how often a "New HN Generation" came in to being.
Great mindfuck scifi, wish I could tell it's title but now it's clear the author read about this Boltzmann Brain theory...
All the evidence right now points that I am a Boltzmann Brain. It would be amazing for cosmologists to challenge this.
I too find this a fascinating thought experiment.
My main reasoning is due to how we tend to classify the knowledge coming from the observed universe, and how logically stable it is.
Imagine this, you are Boltzmann Brain and track a randomly arranged consciousnesses. You sleep, go to work, eat, and sleep again as a human being.
Main problem is that this kind of existence is very stable for a Boltzman Brain, as in when you wake up you see yourself in the same universe (or at least a very similar one).
Now you have to ask why you are classifying these randomly arranged bits handed out by universe as a human life, but not as an alien one. Or why not you are imagining you are something supernatural like a god? Just shift the bits handed out by universe to you and next time you wake up, you will be a completely different being. It seems to me that this should be possible if you were a Boltzmann Brain and existence would be extremely chaotic.
It seems to me that there is more to existence and consciousness than just reading and classifying random bits handed out to you by universe. It seems to me that logical stability is extremely important for our kind of existence and I don't see how Boltzmann Brain theory would possibly keep the universe logically stable.
Imagine your current mental state as a snapshot. By pure luck some atoms could arrange into the exact same state as your brain is right now. And for that moment, it would be you, it would have your full set of memories. It would be indistinguishable from your current existence.
And then the next moment it would cease to exist.
But there could be infinite many such brains popping in to existence and then disappearing at every instant, with every conceivable configuration of state/memories.
We are still doing a lot of science (especially in the last 30 years) in our own solar system let alone understanding the whole universe.
> Given enough time, every possible structure is formed via random fluctuation
NO. That is not what infinity means. I hate that this garbage made its way into anyone's lexicon.
If a state is possible, isn’t an infinite amount of permutations will form that state? Isn’t that the definition of a non zero probability?
I’m not sure if that means it will for sure happen or not, if the draw happens an infinite amount of times.
Perhaps we could use a variation on in which somehow supports some infinitesimal values, but if one wishes to keep both countable additivity and have the distribution be uniform in the sense of translation invariant, then we run into difficulties.
Similar for other forms with this property. A form that when it does appear is then more likely to return again.
This wikipedia page has some references to the statistical mechanics which are helpful https://en.wikipedia.org/wiki/Fluctuation_theorem
"...from a macroscopic point of view, it would describe complex processes running in reverse. For example, a jet engine running in reverse, taking in ambient heat and exhaust fumes to generate kerosene and oxygen. Nevertheless the size of such a system makes this observation almost impossible to occur. Such a process is possible to be observed microscopically because, as it has been stated above, the probability of observing a "reverse" trajectory depends on system size and is significant for molecular machines if an appropriate measurement instrument is available. This is the case with the development of new biophysical instruments such as the optical tweezers or the atomic force microscope. Crooks fluctuation theorem has been verified through RNA folding experiments.[7]"