Even if you had perfect knowledge of the current state of the universe, knew all the laws, you still couldn't predict shit. The reason is chaos, more precisely: There are no closed-form solutions to chaotic systems. To simulate them you have to go through all the time steps (assuming, without loss of generality^1^, discrete time), simulate every single of them one after the other, arguably creating a universe while doing so. And you have to do that with the computational resources of the universe you're trying to simulate. Good luck. Chaos also means that approximate solutions won't help because sensitivity to small perturbations: There's no upper bound to how far your approximation will be off.

^1^ I can wave my hands faster than you. I dare you. I double-dare you.