15 ms·
Boltzmann Brain
- dang 7y agoA thread from 2016: https://news.ycombinator.com/item?id=12152658 https://news.ycombinator.com/item?id=12152658 2014: https://news.ycombinator.com/item?id=6999074 https://news.ycombinator.com/item?id=6999074
- jv22222 7y agoSomeone should make a "List of repeating ideas that come up on Hacker News with every new HN Generation" post. It would also be interesting to know how often a "New HN Generation" came in to being.
- nategri 7y agoWould posit that HN is well into its "endless september" at this point.
- pmiller2 7y agoIMO, there's not a lot of repetition. It's just that certain individual posts get repeated over and over.
- myhf 7y agoIf a periodically reposted idea undergoes slight variations with each repost, does it experience conscious thought?
- irjustin 7y agoI've always enjoyed this thought experiment and the loosely related one - Last Thursdayism[0]. [0] https://rationalwiki.org/wiki/Last_Thursdayism https://rationalwiki.org/wiki/Last_Thursdayism
- 725686 7y agoHa, ha, "whether Last Thursdayism is true has raged on ever since its inception last Thursday"
- mannykannot 7y agoI have it on good authority that the universe was actually created last Tuesday, but by Wednesday, Last-Thursdayism was already being considered.
- trhway 7y ago> is the idea that the universe was created last Thursday, but with the physical appearance of being billions of years old. 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)
- cosmojg 7y agoHeh, reminds me of this short story: http://www.scp-wiki.net/scp-2000 http://www.scp-wiki.net/scp-2000
- mr_toad 7y agoThe dreams you recall are just artefacts of the restore process initialising your mind.
- mannykannot 7y agoI actually considered that as a realistic possibility -- that memories of dreams form as you wake up -- but I think that is didproved by people talking and moving in their sleep in ways consistent with what they report about their dreams when they wake up. PET and NMR scanning might be able to resolve the issue, if it has not done so already.
- speakeron 7y agoLucid dream research done in the 1970s had subjects signalling from within a dream using eye movement. https://www.researchgate.net/publication/258201870_Lucid_dream_verified_by_volitional_communication_during_REM_sleep https://www.researchgate.net/publication/258201870_Lucid_dre...
- yellowapple 7y ago> with some bit rotting and missing pieces This explains why "Berenstein" is now spelled "Berenstain".
- mannykannot 7y ago"Omphalos", by Philip Gosse, is an interesting and bemusing footnote to the battle between creationism and evolution. It took a similar idea extremely seriously and to great lengths, in order to explain away fossil and other geological evidence, but earned its author nothing but ridicule, even from those nominally on his side: https://en.wikipedia.org/wiki/Omphalos_%28book%29 https://en.wikipedia.org/wiki/Omphalos_%28book%29
- AmericanChopper 7y ago> the battle between creationism and evolution 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).
- mannykannot 7y agoAt the risk of debating something you think is meaningless to participate in... 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.
- dilyevsky 7y ago“Quantum immortality” is my personal favorite “theory” of loopy kind
- duckerude 7y agoAlternatively: > “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/ https://a-point-in-tumblspace.tumblr.com/post/187371750052/)
- empath75 7y agoI found the argument that this was self-refuting fairly convincing. 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.
- icandoit 7y agoI'd be careful assigning meaning depending on a relative time frame. 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.
- roywiggins 7y agoSure, but you have causal effects in your general vicinity that will persist a little while, not least effects that come back to change the originating brain. Boltzmann brains have no past and approximately no future at all.
- icandoit 7y agoYes, but I experience meaning independently of those effects. I think that most people think those effects are what create the experience of meaning. 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.
- glenstein 7y agoI have maddeningly had this exact conversation with a friend, and I can't help but think there's something they're just not understanding about meaning. 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.
- JohnJamesRambo 7y agoThis is one of my absolute favorite ideas/theories.
- _bxg1 7y agoIt's always seemed dubious to me that people try to make probabilistic statements about an event that we only have one sample of, and whose causes we can only speculate about
- alexpetralia 7y agoExactly - probability (and by extension, statements such as "more likely") only make sense when we have a reference class of similar events for which we have iterated trials (frequentism), or iterated trials we can reasonably hypothesize about (hypothetical frequentism). 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.
- deleted 7y ago[deleted]
- jbay808 7y agoExactly -- with such little data, we should only be making definite, absolute statements rather than vague probabilistic guesses.
- russdill 7y agoThis is somewhat similar to the serial number problem, where a small sample of observed serial numbers is used to deduce the size of production.
- AgentME 7y agoI find this question really fun: "Am I a Boltzmann brain, or a real human?". If there exists both a human and a Boltzmann brain with your current mental state, then it doesn't make sense to try to answer this question with a single answer. Your line of reasoning will be identically executed in both, so your line of reasoning can't result in a single answer and be correct. 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.)
- cma 7y agoA Boltzman half-brain with random fluctuations filling in the missing hemisphere's activations is much more thermodynamically likely than a full Boltzman brain. And a quarter of one even more so, etc.
- czep 7y agoThat certainly explains why I'm so forgetful.
- jdkee 7y agoWhat if you are a recurring sequence of Boltzmann brains pooping into existence, lasting mere seconds but correctly temporally sequenced as to form a continuous consciousness?
- klodolph 7y agoIf you like these thought experiments, consider that I’m not actually responding to your comment, but I am actually mashing the keys randomly and it only appears to form a response by coincidence. We are not actually communicating with each other.
- kelnos 7y agoPBS Spacetime did a fun video on this: https://www.youtube.com/watch?v=nhy4Z_32kQo https://www.youtube.com/watch?v=nhy4Z_32kQo
- julienchastang 7y agoExcellent video. Thank you.
- state_less 7y agoIf a Boltzmann Brain that begets more Boltzmann Brains is possible, it would be more likely, since as soon as you had one, you'd have a whole lot more. Similar for other forms with this property. A form that when it does appear is then more likely to return again.
- visarga 7y agoself replicators do, such as all living things
- state_less 7y agoSure do. They tend to get beaten up by random things and lose their form, but reforming soon enough helps keeps them around.
- state_less 7y agoI'm downvoted here <sigh>, but the point I wanted to make is to consider the likely states of the universe vs. the less likely. For macroscopic objects like our brains, a Boltzmann brain fluctuating into existence in the next moment is virtually impossible (very unlikely) relative to a human on earth being present/alive for this state of the universe and the next state. Consider all possible states of the universe, shouldn't we see more states with self-replicators and related probable objects vs. Boltzmann brains fluctuating into existence? This wikipedia page has some references to the statistical mechanics which are helpful https://en.wikipedia.org/wiki/Fluctuation_theorem 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]"
- jancsika 7y agoWhy is it not a Boltzmann rock, or a Boltzmann commemorative coin, or something else inanimate like that? 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?
- AgentME 7y agoThere 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 agoI 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
- dmead 7y agohttps://en.wikipedia.org/wiki/Ego_the_Living_Planet https://en.wikipedia.org/wiki/Ego_the_Living_Planet
- cletus 7y agoMandatory pointer to Isaac Arthur's collaboration on this, Part 1 [1] and 2 [2]. I too find this a fascinating thought experiment. [1]: https://www.youtube.com/watch?v=9UfQb_-XAuY https://www.youtube.com/watch?v=9UfQb_-XAuY [2]: https://www.youtube.com/watch?v=GrK9EaQRp2I https://www.youtube.com/watch?v=GrK9EaQRp2I
- aj7 7y agoBad counting in the probabilities.
- deleted 7y ago[deleted]
- RoutinePlayer 7y agoThis is way too much thinking for a Friday ... call me a Boltzmann brain all you want, but I'm having beer!
- gus_massa 7y agoMost of the arguments in favor of the Boltzmann Brain are written before the discovery of the Hubble's law (1929) when most people thought that the universe was essentially eternal and static. Even Einstein was trying to use the cosmological constant to save the model of a eternal static universe. After the discovery of the Hubble constant, the Big Bang and Inflation, it's more razonable a low entropy starting point.
- raattgift 7y ago> arguments in favor of the Boltzmann Brain are written before the discovery of the Hubble's law (1929) 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 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 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-universe-and-the-arrow-of-time 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-about-the-beginning-of-the-universe 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 https://www.ias.ac.in/article/fulltext/pram/069/01/0015-0022
- mhh__ 7y agoWhen it gets to seriously deep questions like this (possibly not such with this one because it's fairly abstract) I can't help but feel that we don't know enough about the universe to start pontificating. 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.
- RocketSyntax 7y agoThis inspires me even more to learn about boltzmann machines. The `why` lighting up the limbic brain
- jackhalford 7y ago> Some cosmologists believe that a better understanding of the degrees of freedom in the quantum vacuum of holographic string theory can solve the Boltzmann brain problem. All the evidence right now points that I am a Boltzmann Brain. It would be amazing for cosmologists to challenge this.
- stevebmark 7y agoThis is about equally as ignorant, incorrect, and useless, as thinking infinite universes means all infinite possibilities will happen. > 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.
- paulrouget 7y agoCan you expand on that? 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?
- ducttapecrown 7y agoIf you pick a real number at random, what's the probability it will be rational?
- paulrouget 7y agoNot zero. I think the proper way to define it is “almost never” when infinite are involved: https://en.wikipedia.org/wiki/Almost_surely https://en.wikipedia.org/wiki/Almost_surely I’m not sure if that means it will for sure happen or not, if the draw happens an infinite amount of times.
- drdeca 7y agoIn the standard measure theory formalization of probability, that outcome set does have measure exactly 0. 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.
- lmuench 7y agoThere is an infinite amount of numbers between 0.0 and 1.0, none of them are 2.0
- deleted 7y ago[deleted]
- DethNinja 7y agoThis is an interesting topic. Although I don't have much knowledge in this area, randomly arranged atoms forming Boltzmann Brains and keep observing random bits handed out by universe doesn't seem all that likely to me. 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.
- admax88q 7y agoI think you're not fully understading the theory of the Boltzmann brain. A Boltzmann brain would not exist for any extended period of time. They only exist for an instant, they don't "track" any sort of existence or conciousness, they merely pop in to existence for an instant and then disappear the next. 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.
- lemonoftroy 7y agohttp://boltzmannburrito.com/ http://boltzmannburrito.com/
- infradig 7y agoThere is no such thing as a Boltzmann Brain, the mere idea of it is ludicrous. Get over it already.
- croo 7y agoThere is a sci-fi book about scanning a human brain/conciusness to computer and testing wether it recognizes that the computer gets turned off between the tests. Hint; it doesn't as it does not change state. Based on this experiment one can create a machine, upload his mind then destroy the machine because there will eventually be somewhere sometime a state of the universe where the state of the machine will proceed a step. So you can make a simulated world in that computer and be anything in that world, even god. Great mindfuck scifi, wish I could tell it's title but now it's clear the author read about this Boltzmann Brain theory...