This is a side point, but I’m curious if there is a strong argument for claiming lawful brains are more common (had an argument with some theists on this issue, they used BB to argue against multiverse theories)
I would say: because it seems that (in our universe and those sufficiently similar to count, anyway) the total number of observer-moments experienced by evolved brains should vastly exceed the total number of observer-moments experienced by Boltzmann brains. Evolved brains necessarily exist in large groups, and stick around for absolutely aeons as compared to the near-instantaneous conscious moment of a BB.
If they can host brains, they’re “similar” enough for my original intention—I was just excluding “alien worlds”.
I don’t see why the total count of brains matters as such; you are not actually sampling your brain (a complex 4-dimensional object) you are sampling an observer-moment of consciousness. A Boltzmann brain has one such moment, an evolved human brain has (rough back of an envelope calculation, based on a ballpark figure of 25ms for the “quantum” of human conscious experience and a 70-year lifespan) 88.3 x 10^9. Add in the aforementioned requirement for evolved brains to exist in multiplicity wherever they do occur, and the ratio of human moments:Boltzmann moments in a sufficiently large defined volume of (large-scale homogenous) multiverse gets higher still.
This is all assuming that a Boltzmann brain actually experiences consciousness at all. Most descriptions of them seem to be along the lines of “matter spontaneously organises such that for an instant it mimics the structure of a conscious brain”. It’s not clear to me, though, that an instantaneous time-slice through a consciousness is itself conscious (for much the same reason that an instant extracted from a physical trajectory lacks the property of movement). If you overcome that by requiring them to exist for a certain minimum amount of time, they obviously become astronomically rarer than they already are.
Seems to me that combining those factors gives a reasonably low expectation for being a Boltzmann brain.
… but I’m only an amateur, this is probably nonsense ;-)
This is a side point, but I’m curious if there is a strong argument for claiming lawful brains are more common (had an argument with some theists on this issue, they used BB to argue against multiverse theories)
I would say: because it seems that (in our universe and those sufficiently similar to count, anyway) the total number of observer-moments experienced by evolved brains should vastly exceed the total number of observer-moments experienced by Boltzmann brains. Evolved brains necessarily exist in large groups, and stick around for absolutely aeons as compared to the near-instantaneous conscious moment of a BB.
The problem is that the count of “similar” universes does not matter, the total count of brains does. It seems a serious enough issue for prominent multiverse theorists to reason backwards and adjust things to avoid the undesirable conclusion http://www.researchgate.net/publication/1772034_Boltzmann_brains_and_the_scale-factor_cutoff_measure_of_the_multiverse
If they can host brains, they’re “similar” enough for my original intention—I was just excluding “alien worlds”.
I don’t see why the total count of brains matters as such; you are not actually sampling your brain (a complex 4-dimensional object) you are sampling an observer-moment of consciousness. A Boltzmann brain has one such moment, an evolved human brain has (rough back of an envelope calculation, based on a ballpark figure of 25ms for the “quantum” of human conscious experience and a 70-year lifespan) 88.3 x 10^9. Add in the aforementioned requirement for evolved brains to exist in multiplicity wherever they do occur, and the ratio of human moments:Boltzmann moments in a sufficiently large defined volume of (large-scale homogenous) multiverse gets higher still.
This is all assuming that a Boltzmann brain actually experiences consciousness at all. Most descriptions of them seem to be along the lines of “matter spontaneously organises such that for an instant it mimics the structure of a conscious brain”. It’s not clear to me, though, that an instantaneous time-slice through a consciousness is itself conscious (for much the same reason that an instant extracted from a physical trajectory lacks the property of movement). If you overcome that by requiring them to exist for a certain minimum amount of time, they obviously become astronomically rarer than they already are.
Seems to me that combining those factors gives a reasonably low expectation for being a Boltzmann brain.
… but I’m only an amateur, this is probably nonsense ;-)