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 ;-)
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 ;-)