Just finished reading "In Search of Schrödinger's Cat". I am currently trying to explain the Uncertainty principle to myself as if I was 5. Concretely, why it is not possible to measure both position and momentum with 0 error. Is it because it is not possible to be in two places at the same time? The way I understand is that trying to predict where a particle is going to be in the future is same as trying to predict where a life boat is going to be in an ocean in the future - if you zoom in enough to confidently know where the boat is, you will loose the track of the waves, and vise versa.
In qm a particle is described by a wave packet. A wave packet has both position and velocity spread. For a large wave packet the velocity spread is small so the velocity and hence momentum can be fairly accurately determined but the position is very uncertain. On the other hand for a small wave packet the position of the particle is more or less fixed but velocity spread of such packet is very large so momentum of the particle becomes indeterminate.
You cannot know the exact position and momentum of a particle at the same time because to measure the position of a particle with accuracy you have to use gamma rays (because they have the shortest wavelength of the electromagnetic spectrum) but because they have high energy you will not know the energy of the particle very well. If you want to know the energy of a particle with accuracy you need to use radio waves (because they have the lowest energy the electromagnetic spectrum) but then you won't know the position with accuracy. So either you know the position of a particle with accuracy or it's momentum.