<story><title>Boltzmann Brain</title><url>https://en.wikipedia.org/wiki/Boltzmann_brain</url></story><parent_chain><item><author>Zenst</author><text>I think the chance of being a Boltzmann brain is zero if you can write down &amp;quot;I&amp;#x27;m human&amp;quot; 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.&lt;p&gt;Now, a Boltzmann universe would cater for that - spooky thoughts at a distance :).</text></item><item><author>AgentME</author><text>There are similar thought experiments around complex objects suddenly coming into existence. They&amp;#x27;re not very controversial. The Boltzmann brain thought experiment is interesting because it raises the possibility that there&amp;#x27;s some chance that you might be a Boltzmann brain without realizing it. It&amp;#x27;s very hard to try to figure out what the correct way to reason about this possibility is. Properly reasoning about whether you&amp;#x27;re a Boltzmann brain, and whether you should care about that, probably involves an interesting argument around decision theory and the anthropic principle.</text></item><item><author>jancsika</author><text>Why is it not a Boltzmann rock, or a Boltzmann commemorative coin, or something else inanimate like that?&lt;p&gt;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.&lt;p&gt;Or put differently (based on the Wikipedia article), if the math behind a modern physics theory means that it&amp;#x27;s more likely the given object&amp;#x27;s existence was due to random fluctuations then that&amp;#x27;s a strike against adoption of that theory.&lt;p&gt;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&amp;#x27;re not Boltzmann brains, etc.&lt;p&gt;It&amp;#x27;d be like introducing me to your new programming language&amp;#x27;s syntax by showing me the code for a quine instead of &amp;quot;hello world.&amp;quot; What is the value in doing such a thing?</text></item></parent_chain><comment><author>ivalm</author><text>Boltzmann brain has a solipsistic element. It&amp;#x27;s not just that &amp;quot;you&amp;quot; are a Boltzmann brain, it&amp;#x27;s that the entire universe you&amp;#x27;re experiencing is just a figment of your imagination. Furthermore, you don&amp;#x27;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).</text></comment>
<story><title>Boltzmann Brain</title><url>https://en.wikipedia.org/wiki/Boltzmann_brain</url></story><parent_chain><item><author>Zenst</author><text>I think the chance of being a Boltzmann brain is zero if you can write down &amp;quot;I&amp;#x27;m human&amp;quot; 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.&lt;p&gt;Now, a Boltzmann universe would cater for that - spooky thoughts at a distance :).</text></item><item><author>AgentME</author><text>There are similar thought experiments around complex objects suddenly coming into existence. They&amp;#x27;re not very controversial. The Boltzmann brain thought experiment is interesting because it raises the possibility that there&amp;#x27;s some chance that you might be a Boltzmann brain without realizing it. It&amp;#x27;s very hard to try to figure out what the correct way to reason about this possibility is. Properly reasoning about whether you&amp;#x27;re a Boltzmann brain, and whether you should care about that, probably involves an interesting argument around decision theory and the anthropic principle.</text></item><item><author>jancsika</author><text>Why is it not a Boltzmann rock, or a Boltzmann commemorative coin, or something else inanimate like that?&lt;p&gt;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.&lt;p&gt;Or put differently (based on the Wikipedia article), if the math behind a modern physics theory means that it&amp;#x27;s more likely the given object&amp;#x27;s existence was due to random fluctuations then that&amp;#x27;s a strike against adoption of that theory.&lt;p&gt;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&amp;#x27;re not Boltzmann brains, etc.&lt;p&gt;It&amp;#x27;d be like introducing me to your new programming language&amp;#x27;s syntax by showing me the code for a quine instead of &amp;quot;hello world.&amp;quot; What is the value in doing such a thing?</text></item></parent_chain><comment><author>vkou</author><text>Upon conclusion of this experiment, what makes you think that you&amp;#x27;re not a Boltzmann brain that was momentarily brought into existence with a particular memory of doing that particular thing 5 minutes ago?&lt;p&gt;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&amp;#x27;s neurons during it fleeting moment of consciousness.&lt;p&gt;I don&amp;#x27;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.</text></comment>