Don't get caught up on the term "observation"; in the context of quantum physics, it's more equivilant to the term "interaction". There is no requirement that there be an actual thinking, feeling observer involved. In real life, an observer always IS involved somewhere along the line, of course - otherwise, how would the rest of us ever know what happened? - but the thinking observer doesn't play any role in the actual physics.

The heisenberg uncertainty principle states that (for example) the better you know a particle's position, the less well know know its momentum.

The reason for this is the manner in which momentum is determined in quantum physics; a particle's state is represented by its 'wave function', and its momentume is related to the frequency of its wave. If your particle's wave function is nonzero only for a particular small region of space, then you know that the particle has to be somewhere in that region; however, due to the way these things work mathematically, you need *multiple* waves of different frequencies added together in order to get a wave function that is nonzero for only a particular region of space. Since the momentum of the particle is related to its frequency, and the particle has multiple frequencies, the particle's momentum could be any one of the momenta that correspond to the frequencies of which the wave function is made.

That's more or less where the heisenberg uncertainty principle comes from; it's just a bunch of math. What it actually *means*, however, is unclear. Are the particle's position and momentum undetermined until something interacts with it? Or does it have *multiple* positions and momenta at any given moment? Or maybe some wierd nonsense involving parrallel universes?

If anyone claims to know that one such interpretation is true, he is a liar. Nobody knows. A lot of people have their pet theories, but none of them have been experimentally verified, and most of them amount to nothing more than intellectual masturbation. All anyone knows for the moment is that the math associated with quantum physics yields results that are consistent with experiment.