For example, if you went back in time 1000 years and painted someone’s house a different color, my probability distribution for the weather here and now would look like the historical average for weather here, rather than the weather in the original timeline.
I think the crux here may not be the butterfly effect, but the overall accumulated effect of (quantum) randomness: I would expect that if you went 1000 years back and just “re-ran” the world from the same quantum state (no house painting etc.), the would would be different (at least on the human-preceivable level; not sure about weather) just because so many events are somewhat infuenced by (micro-state) quantum randomness.
The question is only the extent of the quantum effects on the macro-state (even without explicit quantum coin flips) but I expect this to be quite large e.g. in human biology and in particular brain—see my other comment (Re 2.) (NB: independent from any claims about brain function relying on quantum effects etc.).
(Note that I would expect the difference after 1000 years to be substantially larger if you consider the entire world-state to be a quantum state with some superpositions, where e.g. the micro-states of air molecules are mostly unobserved and in various superpositions etc., therefore increasing the randomness effect substantially … but that is merely an additional intuition.)
Good point, and that’s a crux between two not-unreasonable positions, but my intuition is that even if the universe was deterministic, if you (counterfactually) change house color, the day-to-day weather 1000 years later has essentially no correlation between the two universes.
I think the crux here may not be the butterfly effect, but the overall accumulated effect of (quantum) randomness: I would expect that if you went 1000 years back and just “re-ran” the world from the same quantum state (no house painting etc.), the would would be different (at least on the human-preceivable level; not sure about weather) just because so many events are somewhat infuenced by (micro-state) quantum randomness.
The question is only the extent of the quantum effects on the macro-state (even without explicit quantum coin flips) but I expect this to be quite large e.g. in human biology and in particular brain—see my other comment (Re 2.) (NB: independent from any claims about brain function relying on quantum effects etc.).
(Note that I would expect the difference after 1000 years to be substantially larger if you consider the entire world-state to be a quantum state with some superpositions, where e.g. the micro-states of air molecules are mostly unobserved and in various superpositions etc., therefore increasing the randomness effect substantially … but that is merely an additional intuition.)
Good point, and that’s a crux between two not-unreasonable positions, but my intuition is that even if the universe was deterministic, if you (counterfactually) change house color, the day-to-day weather 1000 years later has essentially no correlation between the two universes.