Quantum phenomena stand physics on its ear

WHAT'S so wacky about the quantum mechanics set forth by Heisenberg, Dirac, Schr"odinger, and others? According to author Nick Herbert, the physicists share three concepts: randomness, thinglessness, and interconnectedness. On each point, quantum mechanics stands classical physics on its ear: Randomness

It was on this point - the inherent uncertainty and probabilistic nature of the universe - that Einstein quarreled with quantum physics. If causation were simply a matter of chance, Einstein once noted, he would rather be ``an employee in a gambling casino'' than a physicist. ``The theory accomplishes a lot,'' he observed, ``but it does not bring us closer to the secrets of the Old One [God]. In any case, I am convinced that He does not play dice.'' The concept of underlying laws - the ``secrets of the Old One'' that lie at the heart of reality - is fundamental to classical physics.

Even Newton, whose work helped engineer the yawning gulf that opened in the 18th and 19th centuries between science and religion, explained that ``God in the Beginning form'd Matter in solid, massy, hard, impenetrable, moveable Particles of such Sizes and Figures ... as most conduced to the End for which he form'd them.'' Human life might seem to be chancy, and a kind of hit-or-miss randomness might appear to govern reality. But that only meant humans were blind to ``the End for which he form'd them.'' Newton, whose private writings bear witness to his strong theological convictions, believed that the laws of nature supported such determinism - if such laws could only be found.

Quantum mechanics says otherwise. Why does a particle suddenly break loose from an atom in radioactive decay? Why does an electron suddenly show up on the other side of an impenetrable energy barrier in a semiconductor? The answer seems to be that the process is simply random - although, if enough atoms and particles are considered, a pattern of probability can be discerned.

``Using the word random is not quite right,'' Edward W. Kolb, a Fermilab physicist. ``To me, random means that there is no underlying dynamics, there's no way to predict an outcome.'' Quantum mechanics is ``statistical, but it's not random. It's not completely deterministic, as classical mechanics is. But still you can predict probabilities.''

But even that concept flies in the face of classical mechanics. It's as though you pushed down firmly on the end of a well-built lever placed on a solid fulcrum - only to find that the weight on the other end sometimes rises and sometimes stays still. In that case, describing the lever's action would be a matter not of discovering irrefutable facts but of assessing statistical probabilities. Little wonder, then, that Niels Bohr, father of the Copenhagen interpretation of quantum mechanics, placed less emphasis on what is than on what can be said. ``There is no quantum world,'' he said. ``There is only an abstract quantum description.''


Yet the problem for students of quantum mechanics is not that matter does not exist - a position hardly any physicist would espouse - but that it does not, at the subatomic level, possess its attributes in familiar ways. Its characteristics appear only when measured. What's more, it can't possess all its characteristics at any one time. It's as though a brick could be either red, warm, or rectangular - but not all three at once.

For Samuel Schweber, a Brandeis University historian of science, this sort of ``thinglessness'' constitutes a break with the past. What's new, he says, is the acceptance of the creation and annihilation of particles - the idea that collisions between particles produce entirely new particles, which then almost instantly disappear.

Then what exists? Probabilities and wave patterns - or, as Fermilab director Leon Lederman says, ``domains.'' It may be true that the electrons in your hand or a table do not occupy any clearly identifiable place. But smash your hand against the table and the outermost electrons of each will successfully resist interpenetration. How can that happen in a ``thingless'' universe? Dr. Lederman likens the situation to that of an extremely thin-bladed propeller. The whirling propeller takes up almost no space at all. Nevertheless, it carves out a very clear domain - as anyone can prove by sticking a finger into its circle. You may not be able to see exactly where the blade is, but it's certainly there - as your finger will tell you.


In what may be the weirdest of all quantum phenomena, it appears that particles somehow ``know'' what other particles are doing - and seem to know it at speeds faster than the speed of light. Why is that so bizarre? Because of a relativistic principle known as ``locality.'' Reality, it seems, behaves like a set of local villages, each with its own boundaries, within which local news flies back and forth. Any news from outside each village must cross those boundaries. That requires a means of communication. Before an event in Paris, France, can influence Paris, Tenn., it must be communicated. Even if it's communicated by a radio wave, the process takes a part of a second - a period of time.

What quantum mechanics points to, however, is a principle of ``non-locality.'' It's as though there were no local boundaries at all. It's as though simultaneous action could communicate itself instantaneously across entire universes, without regard to what many physicists regard as the speed limit of the universe - the speed of light.

``Non-locality means that we cannot discuss the different parts of space independently,'' says John Bell, a quiet-spoken, bushy-haired CERN physicist who gave his name to the theorem describing this interconnectedness. ``Yet we cannot get hold of whatever connection there is between the two different regions of space.''

If that seems fuzzy to the layman, that's not surprising. ``The latest theory that I am playing with in interpreting this non-locality,'' says Dr. Bell in his native Northern Ireland English, ``involves the idea that time runs independently at different points in space. I can't explain it to myself, so I can't explain it to you.'' Explainable or not, the interconnectedness of the universe leads to yet another break with the past. According to classical physics, the way to understand a complex system was to break it down and study its parts. But if the parts are so interconnected that their very attributes arise from these connections, if things are what they are only by virtue of their relationships to other things, then an adequate view of the universe can come only from studying it as a whole.

Not surprisingly, one of the newest directions in scientific thought lies in the attempt to study a complex system as a whole - not only in physics, but in social sciences as well. ``Man has always been seeking wholeness - mental, physical, social, individual,'' writes British theoretical physicist David Bohm. ``The notion that all these fragments are separately existent is evidently an illusion, and this illusion cannot do other than lead to endless conflict and confusion.''

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