Tuesday, June 26, 2007

Models of reality

The quantum without waves? One physicists view

Imagine pondering the universe as it presents itself to us, from the majesty of the observable cosmos down to the apparently impenetrable quantum veil, and being able to come up with a vision that ties it together. Indeed, this describes the quest of innumerable individuals searching for that holy grail of physics- the Theory Of Everything.

An endless flow of human thought has considered this question and slowly the nature of reality has revealed itself to us in tantalizing clues here and there scattered throughout the physical sciences. Of course, whether or not humanity will ever reach this goal remains a question. For that matter, there may be no such descriptor of existence within our mental grasp- only phenomena we can observe that reflects a reality beyond our minds.

The paths of human thought that seem to provide the most promise towards gleaning fairly accurate impressions of this reality are those that probe and observe the nature of things. Even if the instruments used; our eyes, ears, touch, and by extension the finer instruments of scientific invention, are all uniquely human in form or construct, they still represent legitimate tools for reaching out to that reality.

Most scientists are realists in the sense that they understand that their measurements, though crucial in framing reality for our comprehension, do not define it. There is probably more reality beyond the reach of the formulas, references, and models we construct. These constructs are best described as tools useful in our endeavor towards learning about the nature of things. There is a classic Skeptico post that alludes to how we learn. Titled: “How do you prove photgraphy to a blind man?” it is well worth reading as it provides an analogy to how imperfect human observation can actually reveal the secrets of reality.

This is where many become confused and mistake the scientific models of reality for reality. For example, the concept of relating wavelength properties to quantum events serves the purpose of describing certain phenomena such as nonlocality and superposition. However expanding this beyond the Planck realm to our vastly more dense reality by alluding to a cosmic consciousness, goes beyond what is actually observed and into unreal and imagined associations.

Victor Stenger in “The Comprehensible Cosmos” notes: The success of physics testifies to some connection to an underlying objective reality. So what might that reality be?” That is the question that we can not answer yet. However, Stenger posits that it is possible to think about this “imponderable” issue using as a base what we can observe of that reality taking into account the fact that our models and equations are essentially tools- that they are not the reality itself.

On the locality of quantum nonlocality

Based on this foundation of observed phenomena, Stenger notes that many theoretical physicists and mathematicians “hold that abstract mathematics, wave functions, quantum fields, metric tensors, and the very equations that hold them together, exist in a world separate from the physical world- a world of ideal “Platonic” forms.”

For example, Roger Penrose envisions that the “ mathematical world is the set of all ‘true’ statements including those that have nothing to do with the physical world and so is not wholly part of that world.” The physical world is a small part of this larger mathematical universe.

This is a form of metaphysics in that it can not be proven using “logic or data.” In this boundary of theoretical physics where observation begins to give way to conjecture Stenger offers a straightforward “metaphysical” theory different than a “Platonic” world view.

He describes an “atom and the void” viewpoint where all the physical “laws” of reality are a result of the interactions between particles. “In this scheme, fundamental particles (or perhaps strings or m-branes) and the more complex objects that are formed when they stick together constitute the sole reality. The observed behavior of these objects is described in the very familiar way we describe the motion of rocks, balls, planets, and other localized bodies of everyday experience- with some differences needed to account for quantum phenomena.”

He stresses that the described wave nature of matter at the Planck level simply serves a purpose and mentions that Feynman and Dirac (great physicists in their own right) both indicated that the concept of waves never needed to be introduced into physics.

Stenger notes for example that: “Quantum mechanics, in its conventional application, treats the interference pattern as a probability distribution of an ensemble of particles, not as the predictive behavior of a single entity called a ‘wave.’ No etheric medium is doing any waving. The wave function lives in a multidimensional abstract space, not in familiar space-time. So it is hardly a likely candidate for a component of reality unless you take the Platonic view.”

With regards to nonlocality, Stenger points out that, from an “atom and the void” viewpoint it is an illusion. To clarify he notes that, at the quantum level, “no direction of time is evident” and nonlocality is not needed if quantum particles can move in both time directions.

According to Stenger “The direction of time of our experience can be understood as a statistical preference in which many body systems, with their highly random behavior, tend to approach equilibrium. The second law of thermodynamics simply defines the arrow of time… In general time reversibility can be used to eliminate many of the so-called paradoxes of quantum mechanics.

This makes it possible for one particle to be at two places at once while behaving locally. Feynman described positrons as electrons going backward in time and this perfectly fits their properties. However, he preferred to stick to the convention of a single time direction and interpreted these “backward” electrons as antiparticles. Nevertheless, Stenger notes: “The model of localized atoms and the void can be made consistent with all observations to date, including quantum phenomena, with a minimum of assumptions once we allow for time reversibility.”

This more straightforward view of the universe leads Stenger to conclude the following: “The laws of physics are simply human inventions motivated by our desire for a viewpoint-independent picture of the universe…the symmetries that lead to the laws of physics are exactly the same as those that would apply if the universe were completely empty. They are symmetries of the void…something comes from nothing because something is more stable than nothing.”

Ref: Stenger, V. The comprehensible cosmos. Prometheus books. New York.2006

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