I have said it before, and I’ll doubtless continue saying it until advanced dementia has rendered me incapable of recalling physics:
This simple statement means that it is impossible, by the laws of physics, to know anything perfectly. While I should mention that the position and momentum of large objects may be known quite accurately, that is not particularly important. From modern chaos theory we know that, in chaotic systems, even arbitrarily small differences in initial conditions result in vastly different outcomes.
The so-called Copenhagen Interpretation of modern physics holds that the uncertainties associated with quantum particles are not merely measurement anomalies. Rather, the item in question has neither an exact position nor an exact momentum until it is measured. What this means is that even if your imaginary space friend really did exist, and even if he were omniscient (that is to say he had a computer that provided exact information on every individual subatomic particle and photon in the universe), he would not be able to predict events precisely beyond a very short time beyond the present. Also, I should point out that a computer with perfect knowledge of the universe would require memory modeling the entire universe 1-to-1. So any sort of storage medium with perfect modeling of the universe would, in fact, be another identical universe. That seems pretty pointless.
So for all the scientists in the world, if your religion depends critically on prophecies, you are screwed.