/sci/ - Science & Math

I bet that this thought experiment has been made a million times before, because i'm too stupid to have my own ideas, but as i can't find shit on it, here goes:

Imagine this: If there was a computer that could simulate the universe we live in, with which we could see the dawn of the universe, everything that's happened since, and everything that's going to happen. As if reality was a movie, or a book, if you will. My conundrum is: could a computer as such even in theory exist without breaking any fundamental laws of existence? Say if i were to peek an hour into the future with this computer, doesn't that mean i have the power to change it (meaning the computer was wrong from the start)? And if this computer is impossible in theory, does that mean we truly are the masters of our own lives, and not chained to destiny?