Sorry I meant the theoretical physics engine operating the real world. For example if 1N of force is exerted on an atom having 1kg of mass, who is to calculate

Sorry I meant the theoretical physics engine operating the real world. For example if 1N of force is exerted on an atom having 1kg of mass, who is to calculate the resulting acceleration of the atom and update the value of the acceleration state variable of the atom? Atom itself or some kind of the universe OS? And wouldn’t it be necessary some kind of energy to calculate it?