See my response to the sibling comment. You don't need to simulate the entire universe. You only need to simulate those parts that can possibly affect a human b

See my response to the sibling comment. You don't need to simulate the entire universe. You only need to simulate those parts that can possibly affect a human being. There's no need, for instance, to simulate photometry for stars in the Andromeda galaxy because we lack the resolution to measure the movement of those stars.