There are a lot of assumptions in “omniscient forecaster knows the position and velocity of all molecules at t=0” that make the answer “probably possible to calculate, probably not in real-time on current hardware”.
Edit (motivated by downvote, though I’d have preferred a textual disagreement): I actually fight the premise. “omnicient forecaster” is so far from current tech that it’s impossible to guess what it could calulate. Say it only has 32 bits of precision in 3 dimensions of position and velocity, so 24 bytes for each of 6x10^23 particles. 1.4x10^25 bytes.
Call it 2 yottabytes. There’s no way we can predict what such a being might or might not be able to calculate, to what precision.
There are a lot of assumptions in “omniscient forecaster knows the position and velocity of all molecules at t=0” that make the answer “probably possible to calculate, probably not in real-time on current hardware”.
Edit (motivated by downvote, though I’d have preferred a textual disagreement): I actually fight the premise. “omnicient forecaster” is so far from current tech that it’s impossible to guess what it could calulate. Say it only has 32 bits of precision in 3 dimensions of position and velocity, so 24 bytes for each of 6x10^23 particles. 1.4x10^25 bytes.
Call it 2 yottabytes. There’s no way we can predict what such a being might or might not be able to calculate, to what precision.