> The second question is more answerable. And my answer is simply this: The universe, despite what it seems at times, is *not* deterministic. Quantum physics shows us that. Quantum physics limits our certainty of things. In the macroscopic world, we can say with a certainty very close to 100% that a pot of water over a roaring bonfire will boil. As things get smaller on the microscopic level, our certainty rapidly decreases. It is impossible for us to note with certainty both the position and velocity of a subatomic particle. The act of measuring one disturbs the other. Thus, our predictive powers over things on this scale break down. We think we know what will happen when we fire an electron into a metal barrier, but we can only really speak of possibilities and percentages rather than certainty, no matter how tightly we try to control the starting parameters.

I haven't read this entire thread yet, so apologies if this question has already been raised and answered. It's something I've long wondered and never really had explained to me.

Dave's description of quantum mechanics above is the way I've always understood it to work as well: the act of observing one property (position or velocity) of a subatomic particle changes the value of the other property, so that at no time can we simultaneously know both the position and the velocity of the particle. Our knowledge of the particle is indeterminate.

But is the particle itself indeterminate -- or, to use the weightier term, random? Whether or not we can know what a particle's position and velocity are, do they not still follow the physical laws of the universe in a deterministic fashion? If the physical laws still obtain on the subatomic scale, then as far as I can see we still have a deterministic universe; we simply can't avail ourselves of that determinacy to predict what will happen because QM prevents us from making the necessary measurements.

Is this correct? Is there even anything like consensus among physicists on this subject? Please, educate me!

Iss