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There are similar thought experiments around complex objects suddenly coming into existence. They're not very controversial. The Boltzmann brain thought experim

There are similar thought experiments around complex objects suddenly coming into existence. They're not very controversial. The Boltzmann brain thought experiment is interesting because it raises the possibility that there's some chance that you might be a Boltzmann brain without realizing it. It's very hard to try to figure out what the correct way to reason about this possibility is. Properly reasoning about whether you're a Boltzmann brain, and whether you should care about that, probably involves an interesting argument around decision theory and the anthropic principle.

Zenst 7y ago
I think the chance of being a Boltzmann brain is zero if you can write down "I'm human" on a bit of paper, paper in the room, go to another room and then return to the original room and read the paper saying exactly what you initially wrote. Whilst the memory of writing it may well be false, the paper will not be. Now, a Boltzmann universe would cater for that - spooky thoughts at a distance :).
- undersuit 7y ago
  > I think the chance of being a Boltzmann brain is zero if you can write down "I'm human" on a bit of paper, paper in the room, go to another room and then return to the original room and read the paper saying exactly what you initially wrote. 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.
  - Zenst 7y ago
    Yes, if the Boltzmann brain is a definition of the universe per say (think Matrix only larger scale), then yes everything would be in the bubble. I'm still trying to reconcile the arrow of time and the whole aspect that in these `brains`/realities how time always moves forward. But nothing concrete at the universal scale.
    - raattgift 7y ago
      Boltzmann brains in the sense preferred by some authors (notably https://arxiv.org/abs/hep-th/0405270 https://arxiv.org/abs/hep-th/0405270 in section C., which is the sense I'll deal with in this reply) are set in thermal equilibrium with chaotic fluctuations away from the equilibrium points that persist only briefly before equilibriating again. 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 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.
- AgentME 7y ago
  Have you physically done that experiment? Why not? I ask this rhetorically, but I don't mean this as some kind of gotcha to say that you're wrong for not doing the experiment. I believe there's a whole pile of interesting reasons in our heads that explain why we've never done that experiment, and the Boltzmann brain thought experiment is interesting because it helps us notice those reasons. One big reason is that the knowledge of whether you're a Boltzmann brain or not can't possibly help you. I'd also argue that our brain has some kind of intuition that super-low-probability events don't matter compared to super-higher-probability worlds that we can still affect. This seems like some kind of hint for how we can think about the Anthropic principle, but I'm not sure what it's telling us. (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.)
  - Zenst 7y ago
    Have I done it myself, no but about 20 years ago a house mate had done some LSD and came home to him in such a state that did exactly that to prove to himself that he was real and that bit of paper acted as a comfort blanket for the rest of the trip he was on. Crazy times, but happened. 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 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.
- vkou 7y ago
  Upon conclusion of this experiment, what makes you think that you're not a Boltzmann brain that was momentarily brought into existence with a particular memory of doing that particular thing 5 minutes ago? 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.
  - Zenst 7y ago
    Well, as it's not the ultimate defence in law courts (though I'm sure one day somebody will try it), I still can not resolve it with the arrow of time, hence by expanding it as I outlined in another reply I was able to resolve that aspect, at least from my perspective and that's the crux. As perspective is and could very well be Boltzmann Brain and with that you are right if you factor in sensory aspects. It's just the whole arrow of time aspect.
- ivalm 7y ago
  Boltzmann brain has a solipsistic element. It's not just that "you" are a Boltzmann brain, it's that the entire universe you're experiencing is just a figment of your imagination. Furthermore, you don't know how long this experience has been going on since all your memories might be entirely fake (ie maybe you came into existence a mere moment ago and will cease to exist in the next instance; you only have fakeable memories of the past, an unreliable perception of the present, and no knowledge of the future).
- perl4ever 7y ago
  If you want to get solipsistic, you do not, regardless of whether the physical world exists, experience a piece of paper or anything external directly. 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?
  - Zenst 7y ago
    I'm starting to grasp that it is like trying to prove or disprove `god` and with that, it is a large rabbit hole of thought.
    - perl4ever 7y ago
      What I've often thought, although never been able to express elegantly, is that assuming all conventional views of reality are accurate, a person's consciousness has to perceive an image in a mirror that exists within oneself. The sensory inputs have to be assembled for observation. 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.
- jbay808 7y ago
  Have you ever programmed a microcontroller? Like an MSP430 or something? 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.
  - Zenst 7y ago
    Yes. So if I think of a Boltzmann brain as a universe in that context, then I totally get the point. Thank you.
- kromem 7y ago
  How about a Boltzmann simulation? 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.
  - deleted 7y ago
    [deleted]
  - glenstein 7y ago
    This is interesting, but wouldn't 'organization of energy' be physical too?
    - Zenst 7y ago
      I'm leaning towards looking at this akin to the Matrix, whilst your in the Matrix, if you have never been outside then reality and what is real is totally different from perspective. As nobody has proven they have been outside this Boltzmann Brain aka Matrix, nobody can disprove it. Very much like most religious icons you could say.

Zenst 7y ago

I think the chance of being a Boltzmann brain is zero if you can write down "I'm human" on a bit of paper, paper in the room, go to another room and then return to the original room and read the paper saying exactly what you initially wrote. Whilst the memory of writing it may well be false, the paper will not be. Now, a Boltzmann universe would cater for that - spooky thoughts at a distance :).

undersuit 7y ago
> I think the chance of being a Boltzmann brain is zero if you can write down "I'm human" on a bit of paper, paper in the room, go to another room and then return to the original room and read the paper saying exactly what you initially wrote. 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.
- Zenst 7y ago
  Yes, if the Boltzmann brain is a definition of the universe per say (think Matrix only larger scale), then yes everything would be in the bubble. I'm still trying to reconcile the arrow of time and the whole aspect that in these `brains`/realities how time always moves forward. But nothing concrete at the universal scale.
  - raattgift 7y ago
    Boltzmann brains in the sense preferred by some authors (notably https://arxiv.org/abs/hep-th/0405270 https://arxiv.org/abs/hep-th/0405270 in section C., which is the sense I'll deal with in this reply) are set in thermal equilibrium with chaotic fluctuations away from the equilibrium points that persist only briefly before equilibriating again. 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 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.
AgentME 7y ago
Have you physically done that experiment? Why not? I ask this rhetorically, but I don't mean this as some kind of gotcha to say that you're wrong for not doing the experiment. I believe there's a whole pile of interesting reasons in our heads that explain why we've never done that experiment, and the Boltzmann brain thought experiment is interesting because it helps us notice those reasons. One big reason is that the knowledge of whether you're a Boltzmann brain or not can't possibly help you. I'd also argue that our brain has some kind of intuition that super-low-probability events don't matter compared to super-higher-probability worlds that we can still affect. This seems like some kind of hint for how we can think about the Anthropic principle, but I'm not sure what it's telling us. (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.)
- Zenst 7y ago
  Have I done it myself, no but about 20 years ago a house mate had done some LSD and came home to him in such a state that did exactly that to prove to himself that he was real and that bit of paper acted as a comfort blanket for the rest of the trip he was on. Crazy times, but happened. 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 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.
vkou 7y ago
Upon conclusion of this experiment, what makes you think that you're not a Boltzmann brain that was momentarily brought into existence with a particular memory of doing that particular thing 5 minutes ago? 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.
- Zenst 7y ago
  Well, as it's not the ultimate defence in law courts (though I'm sure one day somebody will try it), I still can not resolve it with the arrow of time, hence by expanding it as I outlined in another reply I was able to resolve that aspect, at least from my perspective and that's the crux. As perspective is and could very well be Boltzmann Brain and with that you are right if you factor in sensory aspects. It's just the whole arrow of time aspect.
ivalm 7y ago
Boltzmann brain has a solipsistic element. It's not just that "you" are a Boltzmann brain, it's that the entire universe you're experiencing is just a figment of your imagination. Furthermore, you don't know how long this experience has been going on since all your memories might be entirely fake (ie maybe you came into existence a mere moment ago and will cease to exist in the next instance; you only have fakeable memories of the past, an unreliable perception of the present, and no knowledge of the future).
perl4ever 7y ago
If you want to get solipsistic, you do not, regardless of whether the physical world exists, experience a piece of paper or anything external directly. 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?
- Zenst 7y ago
  I'm starting to grasp that it is like trying to prove or disprove `god` and with that, it is a large rabbit hole of thought.
  - perl4ever 7y ago
    What I've often thought, although never been able to express elegantly, is that assuming all conventional views of reality are accurate, a person's consciousness has to perceive an image in a mirror that exists within oneself. The sensory inputs have to be assembled for observation. 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.
jbay808 7y ago
Have you ever programmed a microcontroller? Like an MSP430 or something? 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.
- Zenst 7y ago
  Yes. So if I think of a Boltzmann brain as a universe in that context, then I totally get the point. Thank you.
kromem 7y ago
How about a Boltzmann simulation? 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.
- deleted 7y ago
  [deleted]
- glenstein 7y ago
  This is interesting, but wouldn't 'organization of energy' be physical too?
  - Zenst 7y ago
    I'm leaning towards looking at this akin to the Matrix, whilst your in the Matrix, if you have never been outside then reality and what is real is totally different from perspective. As nobody has proven they have been outside this Boltzmann Brain aka Matrix, nobody can disprove it. Very much like most religious icons you could say.