If I remember correct, some quantum mechanic principle says that you can't know the position of a particle at the same time as its velocity. Why's that? And what about the double-slit experiment where you send photons and they go through both slits at the same time and create an interference. The observer effect I believe it's called. Does the interference effect disappear if you measure where the photon goes? But what's a measurement? Why do you still get interference when you look at the experiment (with your eyes)? Isn't that a measurement? Of course the brain won't register the results, but it happens in front of your eyes, and if you could rewind and "zoom" you should be able to see the photons? Won't this experiment be possible with any particle? What does all this imply to determinism?