Is the Boltzmann brain paradox a genuine one?

For some time, I have been wondering whether the Boltzmann brain paradox is a genuine one. Here’s how Wikipedia describes the paradox (emphases are mine):


In physics thought experiments, a Boltzmann brain is a self-aware entity that arises due to extremely rare random fluctuations out of a state of thermodynamic equilibrium. For example, in a homogeneous Newtonian soup, theoretically by sheer chance all the atoms could bounce off and stick to one another in such a way as to assemble a functioning human brain (though this would, on average, take vastly longer than the current lifetime of the universe).


The idea is indirectly named after the Austrian physicist Ludwig Boltzmann (1844–1906), who in 1896 published a theory that the Universe is observed to be in a highly improbable non-equilibrium state because only when such states randomly occur can brains exist to be aware of the Universe. One criticism of Boltzmann’s “Boltzmann universe” hypothesis is that the most common thermal fluctuations are as close to equilibrium overall as possible; thus, by any reasonable criterion, human brains in a Boltzmann universe with myriad neighboring stars would be vastly outnumbered by “Boltzmann brains” existing alone in an empty universe.


Boltzmann brains gained new relevance around 2002, when some cosmologists started to become concerned that, in many existing theories about the Universe, human brains in the current Universe appear to be vastly outnumbered by Boltzmann brains in the future Universe who, by chance, have exactly the same perceptions that we do; this leads to the absurd conclusion that statistically we ourselves are likely to be Boltzmann brains. Such a reductio ad absurdum argument is sometimes used to argue against certain theories of the Universe.


The two assumptions I’d like to question in this post are: (i) the assumption that a Boltzmann brain could self-assemble in the first place, given enough time; and (ii) the assumption that the spontaneous self-assembly of such a brain is more likely than the spontaneous formation of human observers.

Concerning (i), I would like to point out that the brain is a multi-layered organ containing 86 billion neurons, each of which is supported by glial cells and astrocytes. Within each neuron is a nucleus, surrounded by a cell body which receives signals via dendrites and sends signals along an axon, which in turn is insulated with a myelin sheath. The idea that individual atoms could arrange themselves into a brain containing tens of billions of these multi-layered structures is simply absurd, because such a “brain” would fall apart long before it formed. Without stable intermediate stages, a brain cannot spontaneously self-assemble out of atoms, even when given an infinite amount of time.

As for (ii): it seems to me that the main argument in its favor is that thermodynamically speaking, it’s easier for an infinite box of gas in equilibrium to assemble into X than it is for the gas to assemble into X + Y. Hence the spontaneous formation of a brain alone is far more likely than the self-assembly of a brain attached to a human body, which in turn is more likely to form spontaneously than an entire planet full of organisms (including humans), which is more likely to form spontaneously than a universe full of stars and planets (including our Earth). But this kind of reasoning ignores the possibility of “springboards,” or transitional stages which generate multiple paths, some of which lead to the desired target.

Thus the likelihood of a brain forming from a box of gas is far greater if the gas is first allowed to assemble into a primordial cell, as such a cell is capable of evolving into various kinds of organisms (including humans with brains). But evolution can only proceed in a physical environment; hence we need a planet for the cell and its descendants to live on. But a planet needs a source of energy to power the chemical reactions leading to life, which in turn requires energy to power its own internal processes; hence we need a star as well. And the formation of stars is rendered more likely by the postulation of an initial Big Bang, starting from a hot, dense state. In short: while the spontaneous formation of a universe, holus bolus, is many orders of magnitude less likely than the spontaneous formation of a brain, the formation of a human being possessing a brain within the framework of a Big Bang universe which is capable of generating stars and planets, some of which are capable of generating life, which subsequently evolves into the dazzling array of creatures we see on Earth, is far more likely than the spontaneous self-assembly of a Boltzmann brain – an event whose probability I have already argued is zero.

I’d like to finish with a closing thought. Is there something wrong with the way we define entropy? Currently, physicists define it in terms of the number of possible micro-states of a system which are consistent with its macro-description (e.g. “a human brain”). This, in essence, is what Boltzmann’s entropy formula expresses. However, such a definition ignores a system’s history, and makes no attempt to calculate the number of pathways by which the atoms in the system can reach their macro-level target. Boltzmann’s definition of entropy also leads many well-meaning but misinformed laypeople to mount fallacious arguments against biological evolution. Isn’t it about time we came up with a better definition, which doesn’t generate silly paradoxes? What do readers think?

259 Replies to “Is the Boltzmann brain paradox a genuine one?”

  1. BruceS
    Ignored
    says:

    (i) the assumption that a Boltzmann brain could self-assemble […]

    You are missing the assumption that the universe will end up spending an unlimited time in a state of thermodynamic equilibrium. Any microstate has a finite probability of arising in such a state, including a human brain in contemplation of its existence. The probability of such a state is unimaginably small, but still greater than zero. And any state with positive probability will arise an unlimited number of times in an unlimited time frame.

    Brains alone are more likely that fully human observers because they are a subset of fully human observers and so their probability is higher. But fully human observers would also be possible. Of course, there is no claim that these entities would last very long!

    Sean Carroll has a nice paper on BBs (link below). He includes the philosophical explanation (first put forward by Albert, I believe) of why you or I should reject the hypothesis that we are currently Boltzmann brains. Roughly, any such assumption is incoherent, since it depends on scientific knowledge that no Boltzmann brain could have (using knowledge as JTB, emphasis on the J).

    Link to Carroll’s paper
    https://arxiv.org/abs/1702.00850

  2. BruceS
    Ignored
    says:

    Is there something wrong with the way we define entropy?

    I think more care is needed in use of both ‘we’ and of ‘define’.

    First, the ‘we’ can refer to scientists working in thermodynamics and to scientists working in statistical mechanics. Not the same we, at least not historically, There are also different we’s and related definitions in QM and more distantly related definitions in information theory (although some absent but remembered posters would be very unhappy indeed with me for that “more distantly”).

    And the ‘we’ can also refer to people arguing about evolution based on popular (mis-)understandings of the scientific term of art. I see no reason to care about or empower such a we when it comes to defining the term scientifically.

    Entropy was first defined an term of art in thermodynamics. It names a specific extensive property expressed as S in the formula. dS = δQ/T. This is a state property which can be, in principle, measured by experiments on an idealized system.

    ‘Entropy’ is also a term used in statistical mechanics, which is how Boltzman used it. He wanted to prove that TD entropy could be reduced to /expressed in SM in the way you describe.. There is ongoing work in philosophy of science on the extent to which he (or Gibbs) succeeded. But it is fair to say most think Boltzmann was right for all practical purposes, and SM in general is a well-used tool in science.

    Short answer to your question: No, we should not redefine entropy. Yes, we should point out misunderstandings of the meaning of the term.

  3. OMagain
    Ignored
    says:

    Concerning (i), I would like to point out that the brain is a multi-layered organ containing 86 billion neurons, each of which is supported by glial cells and astrocytes

    It’s funny how practicality suddenly comes into it when the subject is not the uncaused first cause. Your “designer” is presumably more complex even then an organ containing 86 billion neurons. And yet that has “come into existence” from nothing and you accept that fully without requiring an assessment of that probability.

    Start with the mote in your own eye perhaps?

  4. J-Mac
    Ignored
    says:

    VJ,

    Thank you for another “shorter” OP! I’m sure it is much appreciated, especily by those with the limited attention span…
    It would appear to be the case that there is one sentence missing from the Wikipedia quote…
    It would appear to be the case that the missing sentence could be essential to the theme of the OP…

    “…When applied to more recent theories about the multiverse, Boltzmann brain arguments are part of the unsolved measure problem of cosmology.

    I’m sure the omitting of the sentence was accidental…

  5. fifthmonarchyman
    Ignored
    says:

    OMagain: Your “designer” is presumably more complex even then an organ containing 86 billion neurons. And yet that has “come into existence” from nothing

    Lets correct your presumptions.

    First God is not complex. He is by definition simple (he has no parts).

    Second God does not “come into existence” from nothing. He exists necessarily.

    peace

  6. newton
    Ignored
    says:

    fifthmonarchyman: First God is not complex. He is by definition simple (he has no parts).

    By definition only for those who hold the principle of divine simplicity if we wish to correct presumptions.

  7. fifthmonarchyman
    Ignored
    says:

    newton: By definition only for those who hold the principle of divine simplicity if we wish to correct presumptions.

    If God has parts he is dependent on something to hold the parts together or is in danger of coming apart …

    God can’t be dependent on anything or contingent in anyway and still be God.

    peace

  8. J-Mac
    Ignored
    says:

    fifthmonarchyman: First God is not complex. He is by definition simple (he has no parts).

    No? Prove it! 😁

    BTW: you’ve been reading willam lane craig too much… He has to stop using this nonsensical assumption…

  9. keiths keiths
    Ignored
    says:

    Hi Vincent,

    As you may know, I left TSZ several months ago due to the ongoing, egregious abuse of moderation privileges by Alan, Neil, and DNA_Jock. When I last posted, my comments were being held in the moderation queue, despite the fact that I had violated no rules — by Alan’s own admission.

    I would like to respond to this quote from your OP:

    Is there something wrong with the way we define entropy? Currently, physicists define it in terms of the number of possible micro-states of a system which are consistent with its macro-description (e.g. “a human brain”). This, in essence, is what Boltzmann’s entropy formula expresses. However, such a definition ignores a system’s history, and makes no attempt to calculate the number of pathways by which the atoms in the system can reach their macro-level target. Boltzmann’s definition of entropy also leads many well-meaning but misinformed laypeople to mount fallacious arguments against biological evolution. Isn’t it about time we came up with a better definition, which doesn’t generate silly paradoxes?

    …but I am unwilling to participate as long as I am being censored by having my comments held in the moderation queue.

    Let’s see if this comment gets held in the queue.

    ETA: It’s being held. What a shame that some of our moderators are so frightened of open discussion and so eager to censor.

  10. fifthmonarchyman
    Ignored
    says:

    J-Mac: Prove it!

    I just did

    J-Mac: you’ve been reading willam lane craig too much… He has to stop using this nonsensical assumption…

    I don’t think Craig holds to divine simplicity.

    https://www.reasonablefaith.org/writings/question-answer/divine-simplicity

    peace

  11. fifthmonarchyman
    Ignored
    says:

    vjtorley said:

    quote:

    it seems to me that the main argument in its favor is that thermodynamically speaking, it’s easier for an infinite box of gas in equilibrium to assemble into X than it is for the gas to assemble into X + Y. Hence the spontaneous formation of a brain alone is far more likely than the self-assembly of a brain attached to a human body, which in turn is more likely to form spontaneously than an entire planet full of organisms (including humans), which is more likely to form spontaneously than a universe full of stars and planets (including our Earth).

    end quote:

    I say:

    I think you might be misunderstanding the thought experiment.

    If I understand correctly. It’s not that BBs “self assemble” in some way it’s that they pop into existence fully formed from time to time given an infinite spatiotemporal universe.

    It’s more likely for a BB to instantly and spontaneously appear and later disappear than for all the many thermodynamicly complex structures you mention to exist over billions of years.

    peace

  12. J-Mac
    Ignored
    says:

    fifthmonarchyman: I just did

    I don’t think Craig holds to divine simplicity.

    https://www.reasonablefaith.org/writings/question-answer/divine-simplicity

    peace

    You didn’t prove anything and the link you provided says: “(7) God has no parts”
    OMagain!😥

  13. fifthmonarchyman
    Ignored
    says:

    J-Mac: You didn’t prove anything

    Sure I did. Read it again. 😉

    J-Mac: link you provided says: “(7) God has no parts”
    OMagain!😥

    So your problem is not with the doctrine of DS but with the phrase “God has no parts”.

    Well that is somthing totally different
    LOL

    peace

  14. Neil Rickert
    Ignored
    says:

    fifthmonarchyman: First God is not complex. He is by definition simple (he has no parts).

    Hmm. The content of the empty set is not complex.

    Second God does not “come into existence” from nothing. He exists necessarily.

    Hmm. The empty set exists necessarily.

  15. Kantian Naturalist Kantian Naturalist
    Ignored
    says:

    From the OP

    I’d like to finish with a closing thought. Is there something wrong with the way we define entropy? Currently, physicists define it in terms of the number of possible micro-states of a system which are consistent with its macro-description (e.g. “a human brain”). This, in essence, is what Boltzmann’s entropy formula expresses. However, such a definition ignores a system’s history, and makes no attempt to calculate the number of pathways by which the atoms in the system can reach their macro-level target. Boltzmann’s definition of entropy also leads many well-meaning but misinformed laypeople to mount fallacious arguments against biological evolution. Isn’t it about time we came up with a better definition, which doesn’t generate silly paradoxes? What do readers think?

    I think this is very close to the correct solution: we do need a way of thinking about history here, and the paradoxes of the Boltzmann brain scenario arise because thermodynamics alone doesn’t take history into account. That is not a problem with thermodynamics and it is not a problem with how we define entropy. But the absence of a sufficiently robust understanding of history within thermodynamics underscores why we ought not to rely on thermodynamics alone.

  16. J-Mac
    Ignored
    says:

    fifthmonarchyman: Sure I did. Read it again.😉

    So your problem is not with the doctrine of DS but with the phrase “God has no parts”.

    Well that is somthing totally different
    LOL

    peace

    Yes! Yes! And Yes!
    OMagain! Your customer! 😭

  17. J-Mac
    Ignored
    says:

    Kantian Naturalist: I think this is very close to the correct solution

    Yup! Multiverse which is no different than multivitamin…
    Try to prove me wrong….😎

  18. fifthmonarchyman
    Ignored
    says:

    Neil Rickert: The content of the empty set is not complex.

    By definition there is no content “of the empty set” complex or otherwise.

    Nonexistent is not the opposite of complex

    Neil Rickert: The empty set exists necessarily.

    Interesting. If nothing whatsoever existed but God would the empty set still exist?

    If yes then the empty set owes it’s existence directly to the mind of God. If not then it’s existence is not necessary. It’s six of one and a half dozen of the other

    peace

  19. newton
    Ignored
    says:

    fifthmonarchyman: If God has parts he is dependent on something to hold the parts together or is in danger of coming apart …

    In the material world , God is immaterial.

    God can’t be dependent on anything or contingent in anyway and still be God.

    Including our comprehension.

  20. fifthmonarchyman
    Ignored
    says:

    newton: In the material world , God is immaterial.

    1) So then according to your view a God with parts is only dependent on the world he inhabits? Dependent on one thing is still dependent.

    2) Complex immaterial things like concepts are still dependent on something to hold them together.

    Usually the mind of the person who holds them

    newton: Including our comprehension.

    I do agree with this one.

    God is not in any way dependent on our comprehension but being omnipotent he can reveal himself to us so that we can understand if he chooses to.

    peace

  21. quarrion
    Ignored
    says:

    It’s simple.
    God the Father has no parts.
    God the Son has no parts.
    God the Holy Spirit has no parts
    Therefore God has no parts.

  22. dazz dazz
    Ignored
    says:

    quarrion:
    It’s simple.
    God the Father has no parts.
    God the Son has no parts.
    God the Holy Spirit has no parts
    ThereforeGod has no parts.

    Lulz

  23. Robert Byers
    Ignored
    says:

    Who says humans have a brain? whats a brain? Who says the construction of the stuff in our head is the source for thinking? What about animal brains?
    This paradoxes, from the old dumb days in europe, presume we have no soul, don’t think exclusively with our soul, Our mythical brain only has within it a memory.
    So intelligence/brain would never evolve. The memory evolving, by the absird concept of selection on mutations, would be useless.
    The paradox doesn’t exist or hasn’t proved it can exist before needing a answer.

  24. Joe Felsenstein Joe Felsenstein
    Ignored
    says:

    Vincent : Our solar system and our biosphere are far from any thermodynamic equilibrium — there is energy flowing through from the sun on its way out to the rest of the universe. Biology sees sensitive cell membranes, neurons, nerve nets, ganglia, sense organs and brains as having evolved in biological evolution, in organisms that are dissipative structures in nonequilibrium.

    Nobody I know thinks that Boltzmann brains arose at any point. So how common they would be here or there, now or then, is irrelevant. Getting the Granville Sewells of this world not to say foolish things about evolution and thermodynamics is not best done by arguing about Boltzmann brains.

    By the way, Boltzmann himself was a huge fan of Charles Darwin.

  25. quarrion
    Ignored
    says:

    It’s half-past last Thursday, and I am wondering if everything is just a manifestation of a Boltzmann brain, or the musings of a half-Wittgenstein.

  26. Allan Miller
    Ignored
    says:

    One small point, which comes up often: primordial life did not need a sun to provide energy. Or at least, not directly. Photosynthesis is not a required property of an early cell.

    Following the formation of heavier-than-helium elements in our star, and expulsion on its explosion, a source of energy was available simply due to the differential electronegativity of different elements – chemotrophy. The energy of chemical reaction, incrementally tapped, is essentially what drives life. Photosynthesis uses photons to push electrons back up the thermodynamic hill, but many organisms use electrons from atoms that are effectively already ‘up there’.

  27. BruceS
    Ignored
    says:

    Kantian Naturalist:
    From the OP

    I think this is very close to the correct solution: we do need a way of thinking about history here, a

    In fact, the 2LT is based on the past hypothesis, that is that entropy was lower in the past. So history is very much apart of Statistical Mechanics and its justification of 2LT. Without that past hypothesis, the 2LT cannot be justified as a result of SM, because microstate laws are time symmetric.

    David Albert’s Time and Chance is good for understanding why this is, if you can stomach his idiosyncratic writing style. Sean C covers it in his various popularizations as well.

    The problem with BBs is not the past, it is the future.

    ETA: Here is Sean C on the Past hypothesis
    http://www.preposterousuniverse.com/blog/2010/03/02/from-eternity-to-book-club-chapter-eight/

  28. BruceS
    Ignored
    says:

    Joe Felsenstein:

    By the way, Boltzmann himself was a huge fan of Charles Darwin.

    As far as science goes, BBs are postulated for the far future, not now or in the past.

    Boltzmann himself did not have the past hypothesis and was so very puzzled about how any type of order (in the sense of low entropy) could exist. He postulated our whole universe was a thermodynamic statistical fluctuation.

    You are right that the arguments about 2LT and evolution have nothing to do with an informed discussion of BBs.

  29. Allan Miller
    Ignored
    says:

    It strikes me that an end state of total thermodynamic equilibrium would have matter in a massively condensed state, not any fit state to start a-formin’ brains.

  30. BruceS
    Ignored
    says:

    keiths:

    As you may know, I left TSZ several months ago due to the ongoing,

    Hi Keith: Just to be open now that you are reading this, and in case you look at my posts, I was alluding to you in my above post, specifically the absent poster who would be very upset with me for saying TD entropy was distrant from info theory entropy.

    That semi-serious remark of mine is a caricature of the concerns discussed in more detail in this link.
    A Field Guide To Recent Work On The Foundations Of Statistical Mechanics

    If you have any other technical feedback on the contents of my posts, I would welcome it and would be happy to discuss with you. Anything but the info versus energy dispersion stuff, that is!

  31. BruceS
    Ignored
    says:

    Allan Miller:
    It strikes me that an end state of total thermodynamic equilibrium would have matter in a massively condensed state, not any fit state to start a-formin’ brains.

    OK, but not is not what the physicists think, if I understand Carroll properly. And I understand them to be talking about fluctuations, not the sort of 2LT driven processes we see in the current universe

    ETA: just to be clear, by fluctuation I mean the sort of thing implied by statements like “nothing in 2LT under SM prevents all the air molecules from ending up on the other side of the room”.

    In an unlimited time, some very strange things indeed can happen, as long as they have probability greater than zero.

    ETA 2: Here is Sean C on BBs and equilibrium
    http://www.preposterousuniverse.com/blog/2010/03/16/from-eternity-to-book-club-chapter-ten/

  32. Allan Miller
    Ignored
    says:

    BruceS,

    Well, my imagined scenario is the entire universe condensed into a supermassive black hole. To assemble anything, somehow, an atom has to get from A to B. There are other atoms in the way, and it is pinned in place by its own interactions. Of course one can imagine a ‘fluctuation’ giving it the energy to travel, and shove the rest out the way, but it will interact on the way. I don’t see any system arising in such a manner. By analogy, one could imagine any distribution of chess pieces on a 64-square grid, but only some are reachable by legal moves from a conventional start. You can’t just elbow your pawns out the way without consequence.

    It is declared without evidence that there is a path to a BB end state available, given time, from any high-entropy start that does not have to go via the kinds of pathway taken by actual brain histories within the kinds of physical parameter values available around our planetary surface.

  33. Allan Miller
    Ignored
    says:

    Of course, in such a scenario, there probably would not be atoms in any case, but some kind of hypercondensed plasma. So, by ‘fluctuation’, your first task is to get a bunch of quarks into an atomic configuration.

  34. BruceS
    Ignored
    says:

    Allan Miller:
    Of course, in such a scenario, there probably would not be atoms in any case, but some kind of hypercondensed plasma. So, by ‘fluctuation’, your first task is to get a bunch of quarks into an atomic configuration.

    Your argument is with the physicists like Sean C, not with me. I go with them as the experts to trust in this matter.

    ETA: It is fair to point out that Boltzmann brains in basic understanding is based on TD fluctuations, not quantum fluctuations. Sean C does consider those, eg in link here. There is a blog entry on that too. I believe. In that situation, more depends on your cosmological assumptions, as I understand him. See here:
    https://arxiv.org/abs/1505.02780

  35. Alan Fox Alan Fox
    Ignored
    says:

    keiths,

    Welcome back, Keiths.

    The TSZ rule that moderation issues should be raised in the Moderation Issues thread has not changed during your absence.

  36. Allan Miller
    Ignored
    says:

    BruceS: Your argument is with the physicists like Sean C, not with me.I go with them as the experts to trust in this matter.

    Sure, though I find the physicists to be a bit light on the chemistry and biology. And, it’s a discussion forum, y’know?

  37. Allan Miller
    Ignored
    says:

    BruceS:It’s fair to point out that Boltzmann brains in basic understanding is based on TD fluctuations, not quantum fluctuations.

    Yes, which is kind of the problem I’m alluding to.

  38. BruceS
    Ignored
    says:

    Allan Miller: Sure, though I find the physicists to be a bit light on the chemistry and biology. And, it’s a discussion forum, y’know?

    But I take the whole point to be that chemistry and biology do not matter when it comes to fluctuations. Maybe they make the probability smaller. Maybe. But that is irrelevant, given the unlimited time which consensus cosmological models postulate (but see the above-linked QM paper for the link between the possibility of BBs and the related cosmological assumptions (ETA) which do not, however, rule out BBs in all situations involving QM fluctuations).

    ETA: In particular, since evolution is not part of the explanation of BBs, biology does not matter. Chemistry might at first sight, eg if it somehow forced QM or TD probabilities to be zero. But I doubt that there is anything emergent in the relevant chemistry that the physicists would be unaware of for this scenario. More importantly, if you say that chemistry somehow introduces new laws which change the underlying physics, then that would conflict with scientific approaches to explanation.

    Here is a pontification on discussions and internet forums. Take that as a trigger warning!

    [start of pontification]
    Everyone is entitled to their opinion, and their opinion of others opinions, and so on. But if one is posting to have an informed, knowledge-based discussion of science or philosophy, then opinion s not an important consideration. Knowledge is.

    So I admit to a bias in the type of discussions that interest me. Probably a bias which would take the fun out of it for most participants in the common internet discussion.

    Which is not to say that I do not find entertainment value in some of the free associations passing as logical reasoning that one finds on internet forums.

    https://discourse.peacefulscience.org/t/the-relationship-between-math-and-physics/3017/174?

  39. keiths keiths
    Ignored
    says:

    Hi Bruce,

    I was alluding to you in my above post, specifically the absent poster who would be very upset with me for saying TD entropy was distrant from info theory entropy.

    I suspected it was me you were referring to. 🙂

    If you have any other technical feedback on the contents of my posts, I would welcome it and would be happy to discuss with you. Anything but the info versus energy dispersion stuff, that is!

    I’d enjoy discussing this stuff with you and others, but not if I’m being censored by the likes of Alan, Neil, and DNA_Jock. As I mentioned above, my comments are being held up in the moderation queue. There is no valid reason for this, just as there was no valid reason for the bogus 30-day ban that Alan imposed on me — for an action that even he admitted was not against the rules.

    (Also gotta love the hypocrisy. Compare Alan’s treatment of swamidass, who actually committed a bannable offense by outing Gregory, with his treatment of me. I get censored for 30 days for something that didn’t violate the rules. Swamidass commits a bannable offense and suffers no consequences.)

    If the moderators restore me to equal status by removing me from pre-moderation, then I’ll happily discuss these topics with you and others. If they continue to abuse their privileges by keeping me in pre-moderation, then I won’t.

    Alan Fox:

    Welcome back, Keiths.

    The TSZ rule that moderation issues should be raised in the Moderation Issues thread has not changed during your absence.

    …says Alan, discussing a moderation issue in a thread other than Moderation Issues.

    As if you gave a rat’s ass about the rules, Alan. You violate them right and left, against TSZ’s interests, based on your personal animosities and lack of impulse control. It’s why Patrick — a former moderator here — has called for your ouster (and Neil’s, and DNA_Jock’s).

    Think about that. Your behavior has been so bad that Patrick, who served alongside you as a fellow moderator, isn’t merely calling for you to be reprimanded — he’s calling for your removal.

    ETA: This comment, like the earlier one, is being held in the moderation queue.

  40. fifthmonarchyman
    Ignored
    says:

    BruceS: As far as science goes, BBs are postulated for the far future, not now or in the past.

    The problem is that when it comes to BBs is we can’t ever know if we are living in the far future and are just imagining that it’s now because it’s less lonely.

    The point of the thought experiment is that that scenario is far more likely than the one we assume is reality.

    peace

  41. fifthmonarchyman
    Ignored
    says:

    It’s interesting to ponder why we would imagine just the reality we do if we indeed are BBs. Are there some realities that are more likely to be imagined than others or is this one just the luck of the draw.

    Is there anything that keeps a BB from imagining a world with no evil for example? How about one with where there is no evidence of common decent?

    It’s all pretty interesting to think about IMO

    peace

  42. fifthmonarchyman
    Ignored
    says:

    I all things being equal think BBs would tend to imagine a world that maximized their own sense of worth.

    In such an imagined world I would expect it would appear to be silly to think we are BBs rather than individuals with reliable sense perception and reasoning faculties.

    peace

  43. BruceS
    Ignored
    says:

    BruceS: ETA: In particular, since evolution is not part of the explanation of BBs, biology does not matter.

    Just for fun: It occurs to me that in an unlimited TD equilibrium, there may be a very very …very tiny, but still positive, probability for a BB to arise by a series of random events mimicking evolution as we see it our present universe.

    So that would seem to be an IDer’s onanistic fantasy.

    (I don’t think that phrase on its own violates site rules on pornography; of course, it would be clearly out of bounds to additionally do a Bezos).

  44. J-Mac
    Ignored
    says:


    Is the Boltzmann brain paradox a genuine one?

    It appears to be the case as all paradoxes are genuine if one has faith…Not only that, it appears to be the case that it can be falsified…especially in countries where pot has been recently legalized… Bob and Bruce must really enjoy the new freedom…Just look at their comments…

    For those who are not under the influence:

    BB including Dr. Maybe’s quote:

    “The measure problem in cosmology concerns how to compute fractions of universes of different types within a multiverse. It typically arises in the context of eternal inflation. The problem arises because different approaches to calculating these fractions yield different results, and it’s not clear which approach (if any) is correct.[1]

    Measures can be evaluated by whether they predict observed physical constants, as well as whether they avoid counterintuitive implications, such as the youngness paradox or Boltzmann brains.[2] While dozens of measures have been proposed,[3]:2 few physicists consider the problem to be solved.[4]

    Infinite multiverse theories are becoming increasingly popular, but because they involve infinitely many instances of different types of universes, it’s unclear how to compute the fractions of each type of universe.[4] Alan Guth put it this way:[4]

    In a single universe, cows born with two heads are rarer than cows born with one head. [But in an infinitely branching multiverse] there are an infinite number of one-headed cows and an infinite number of two-headed cows. What happens to the ratio?
    Sean M. Carroll offered another informal example:[1]

    Say there are an infinite number of universes in which George W. Bush became President in 2000, and also an infinite number in which Al Gore became President in 2000. To calculate the fraction N(Bush)/N(Gore), we need to have a measure — a way of taming those infinities. Usually this is done by “regularization.” We start with a small piece of universe where all the numbers are finite, calculate the fraction, and then let our piece get bigger, and calculate the limit that our fraction approaches.
    Different procedures for computing the limit of this fraction yield wildly different answers.[1]

    https://en.m.wikipedia.org/wiki/Measure_problem_(cosmology)

  45. vjtorley
    Ignored
    says:

    Hi everyone,

    I see that my post has generated lots of comments. I’ll try to address some of them below.

    J-Mac

    It would appear to be the case that there is one sentence missing from the Wikipedia quote…

    I’m sure the omitting of the sentence was accidental…

    Actually, it was quite deliberate. I omitted the last sentence of the third paragraph from my quote from the Wikipedia article on Boltzmann brains because I didn’t want to open a philosophical can of worms, which I thought was beyond the scope of this OP.

    The last sentence of the article’s third paragraph reads as follows: “When applied to more recent theories about the multiverse, Boltzmann brain arguments are part of the unsolved measure problem of cosmology.” The Wikipedia article on the measure problem of cosmology tells us: “The measure problem in cosmology concerns how to compute fractions of universes of different types within a multiverse.… The problem arises because different approaches to calculating these fractions yield different results, and it’s not clear which approach (if any) is correct.… While dozens of measures have been proposed, few physicists consider the problem to be solved.

    Definitely beyond my pay-grade. I hope you can appreciate the reasons for my omission.

    BruceS

    You are missing the assumption that the universe will end up spending an unlimited time in a state of thermodynamic equilibrium. Any microstate has a finite probability of arising in such a state, including a human brain in contemplation of its existence. The probability of such a state is unimaginably small, but still greater than zero…

    Short answer to your question: No, we should not redefine entropy. Yes, we should point out misunderstandings of the meaning of the term.

    I would respectfully disagree with your claim that any microstate has a finite probability of arising from a state of thermodynamic equilibrium, even given an infinite amount of time. See Allan Miller’s comments below, which buttress my conviction.

    If physicists wish to retain Boltzmann’s definition of entropy, fine. But in that case, biologists shouldn’t let them get away with explaining entropy in terms of probabilities, because for some microstates, the probability of their arising from a state of thermodynamic equilibrium is precisely zero.

    Allan Miller

    One small point, which comes up often: primordial life did not need a sun to provide energy. Or at least, not directly. Photosynthesis is not a required property of an early cell.

    Thank you for your point about chemotrophy as a source of energy. You are entirely correct here. The first photosynthetic bacteria date back to 3.4 billion years ago, or about 600 million years after life originated on Earth. However, I would contend that the presence of the Sun was still necessarily indirectly, if life arose in the water. No Sun, no liquid water.

    It strikes me that an end state of total thermodynamic equilibrium would have matter in a massively condensed state, not any fit state to start a-formin’ brains…

    Of course, in such a scenario, there probably would not be atoms in any case, but some kind of hypercondensed plasma. So, by ‘fluctuation’, your first task is to get a bunch of quarks into an atomic configuration.

    Excellent point about plasma! I hadn’t thought about that.

    OMagain

    Your “designer” is presumably more complex even then an organ containing 86 billion neurons. And yet that has “come into existence” from nothing and you accept that fully without requiring an assessment of that probability.

    I don’t know of any Jewish, Christian or Muslim theologian who thinks God came into existence. I’m happy to agree with you that the probability of God’s coming into existence is precisely zero, because if He did, then by definition He wouldn’t be God.

    Re God’s complexity, I see two possible options:

    (a) God is absolutely simple in His Being (even if His thoughts about the things He has made are complex);

    (b) God is complex, but composed of parts which are inseparable (a bit like the quarks that make up a proton) – not just physically inseparable, but metaphysically as well (i.e. it is not even conceivable that God could “come apart”).

    Classical theists have traditionally gone with (a), but I’m willing to at least consider (b).

    fifthmonarchyman

    I think you might be misunderstanding the thought experiment.

    If I understand correctly. It’s not that BBs “self assemble” in some way it’s that they pop into existence fully formed from time to time given an infinite spatiotemporal universe.

    When you say “pop into existence,” do you mean: as an energy fluctuation of the quantum vacuum? I don’t think that’s what Boltzmann meant by entropy, as he formulated his definition some decades before scientists even knew about the quantum vacuum.

    Or do you mean that the atoms of a gas in thermodynamic equilibrium simply fly into the positions which they would occupy in a brain? But such a process would not be instantaneous, as atoms take time to move, and they would get in each other’s way, especially in the case of a compact, multi-layered organ like the brain. A brain could only form in stages, not instantaneously, as the inner layers would have to be in place before the outer layers could envelop them.

    Neil Rickert

    Hmm. The empty set exists necessarily.

    Here’s a question for you. Would the empty set exist if there were no minds?

    Here’s another. Do you believe that sets, whether empty or otherwise, can maintain entities in existence, as the Necessary Uncaused Cause is supposed to do?

    Kantian Naturalist

    I think this is very close to the correct solution: we do need a way of thinking about history here, and the paradoxes of the Boltzmann brain scenario arise because thermodynamics alone doesn’t take history into account. That is not a problem with thermodynamics and it is not a problem with how we define entropy. But the absence of a sufficiently robust understanding of history within thermodynamics underscores why we ought not to rely on thermodynamics alone.

    I strongly agree with your assertion that “the paradoxes of the Boltzmann brain scenario arise because thermodynamics alone doesn’t take history into account.” Well said.

    Joe Felsenstein

    Vincent : Our solar system and our biosphere are far from any thermodynamic equilibrium — there is energy flowing through from the sun on its way out to the rest of the universe…

    By the way, Boltzmann himself was a huge fan of Charles Darwin.

    Life is indeed far from a state of equilibrium, as you rightly point out. Thanks for that. I hadn’t realized that Boltzmann was an admirer of Darwin. For readers who are interested, I would recommend the following article on the subject: The Hidden Connections Between Darwin and the Physicist Who Championed Entropy.

  46. J-Mac
    Ignored
    says:

    vjtorley: J-Mac

    It would appear to be the case that there is one sentence missing from the Wikipedia quote…

    I’m sure the omitting of the sentence was accidental…

    Actually, it was quite deliberate. I omitted the last sentence of the third paragraph from my quote from the Wikipedia article on Boltzmann brains because I didn’t want to open a philosophical can of worms, which I thought was beyond the scope of this OP.

    I knew it 😉
    And due to your omission the OP is scientific now rather than philosophical?
    Look at Byers’and Bruce’s comments…
    Byers thinks he doesn’t need his brain (in his case he is better off without).
    Bruce blames IDists for something he should blame Dr. Maybe (S. Carroll).
    You created more confusion rather than controversy, which I assume was the aim of your OP….

  47. colewd
    Ignored
    says:

    vjtorley,

    Although Einstein was not always right I agree with this point:

    “The equation S = k log W + const appears without an elementary theory — or however one wants to say it — devoid of any meaning from a phenomenological point of view.”
    — Albert Einstein (1910), popular 2007+ re-quote version

    Whats interesting is several claims in modern physics rely on this equation. The work of Stephen Hawkins and Roger Penrose come to mind. Although Penrose later backed off some of his claims when he became convinced he was on shaky ground.

  48. Fair Witness Fair Witness
    Ignored
    says:

    vjtorley:

    Re God’s complexity, I see two possible options:

    (a) God is absolutely simple in His Being (even if His thoughts about the things He has made are complex);

    (b) God is complex, but composed of parts which are inseparable (a bit like the quarks that make up a proton) – not just physically inseparable, but metaphysically as well (i.e. it is not even conceivable that God could “come apart”).

    Classical theists have traditionally gone with (a), but I’m willing to at least consider (b).

    You have summarized the hardcore special pleading that theists resort to, in order to weasel their way around logic.

    Everything we know about the processing of information tells us that it requires the storage of that information so it can be manipulated. Bits require bit-holders.

    Even when the hardware is simple, as with a classical Turing machine, the software fed to it must be complex if the behavior is to be complex – hence the system as a whole is complex.

    To throw away this fundamental requirement, and say that a god who is capable of processing the amount of information needed to design and create a universe, is very simple, is a demonstration of deep ignorance about how things work. It is no better than saying “It’s Magic” and leaving it at that.

    Of course, they may not realize that this is special pleading. One must have a certain degree of experience in either science or engineering to fully understand this issue.

    As for (b) , I hate to tell you this, but “parts that are inseparable” cannot be called parts.

  49. Mung Mung
    Ignored
    says:

    Is there something wrong with the way we define entropy?

    Yes, there is.

    To get a good picture of the confusion surrounding entropy read the books by Arieh Ben Naim.

  50. Mung Mung
    Ignored
    says:

    fifthmonarchyman: Lets correct your presumptions.

    Again.

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