The universe evolves exactly under physical laws, but simulations only approximate those laws with limited data and finite precision. Each new frame builds on the last step’s slightly imperfect numbers, so errors can compound. Imagine trying to predict wind speeds with thermometers in the ocean — you can’t possibly measure every atom of water, so your starting picture is incomplete. As you advance the model forward in time, those small gaps and inaccuracies grow. That’s why “finer detail” from a coarse model usually isn’t new information, just interpolation or amplified noise.