Strange and wonderful things sometimes happen on the boundary between two worlds. An example from physics: send particles through a pair of holes in a barrier, and look at how they spread out on the other side. Make the objects tiny enough and the holes closely-spaced enough, and matter acts like waves. Instead of a smooth distribution, there are interference fringes, bright and dark spots --- places where particles never land right next to other sites where they have a much greater chance of being observed. That's straightforward quantum mechanics.

It's weird enough already --- wavelike behavior of particles, and particle-like behavior of waves --- but then it really gets bizarre. Remember that the paths of charged bodies curve when they're in a magnetic field. (That's how the picture tube in a TV set focuses electrons and paints images on the screen.) So, pipe a magnetic field between the two holes in our barrier, but confine it carefully so that no magnetism leaks out. Then send electrons through the holes again. The electrons never go through any place where a magnet can affect them --- but the pattern of fringes they produce on the wall has nevertheless moved!

That's totally unexplainable by normal forces and fields. In fact, the effect (named for Aharanov and Bohm) doesn't even exist in the non-quantum world. Invisible interactions control the electrons --- interactions that have no classical counterpart. The details get averaged out when we take lots of particles or when we don't observe precisely enough. But the invisible forces are real, and particles respond to them.

The same thing happens in other contexts, if we pay close attention. Influences on a fine scale blur together and aren't apparent in the big picture. Nevertheless, they are real and significant. Nations may not seem to react to such forces, but individuals do. Money talks big, and everybody pays attention to it. Subtle factors --- such as morality, justice, and charity --- act unseen, on individuals, over long periods of time. They matter more.

Monday, November 08, 1999 at 21:33:44 (EST) = 1999-11-08


(correlates: TomorrowSinger, FringeOfThings, BalanceTheBooks, ...)