• Home
• Contact me
• My papers
• Links
• Sitemap
• koantum matters

© 2006 This Quantum World 

Newton discovered an algorithm by which he could calculate the gravitational effects of matter on matter. He also famously refused to embroider his algorithm with a story purporting to explain by what mechanism or process matter acts on matter.

While the Newtonian gravitational action of one body on another depends on the simultaneous positions of the two bodies, the electromagnetic action of matter on matter is retarded: if here there is a charge and there there is another, and if you jiggle the charge here, then the charge there begins to jiggle after a time T = D/c, where D is the distance between the two charges and c is the speed of light. This retardation made it possible to transmogrify the algorithm for calculating the electromagnetic effects of matter on matter into some kind of physical process by which matter acts on matter.

Fact is that the calculation of electromagnetic effects can be carried out in two steps: given the distribution and motion of electrically charged objects, we calculate the six components of the electromagnetic field (a tensor function of position and time) using Maxwell's equations, and given these six components, we calculate the electromagnetic effects that these objects have on any other charged object using the Lorentz force law.

Fiction is that the electromagnetic field is a physical entity in its own right; that it is locally generated by charges here, that it mediates the action of charges on charges by locally acting on itself, and that it locally acts on charges there.

Did you notice that this story does not explain how a charge locally — that is, at one and the same place — acts on the electromagnetic field, how the electromagnetic field locally acts on itself, or how the electromagnetic field locally acts on a charge? Apparently the familiar experience of a kick in the butt, a knock on the head, or a slap in the face is sufficient to understand local action.

Scientists are the myth makers of our time. If a story is believed by a large fraction of the scientific community, it becomes part of our (socially constructed) reality.

Take electromagnetic waves. Even if you agree with me that we cannot observe them directly, you will probably insist that we can observe them indirectly: their effects are all over the place.

But it isn't their effects. The jiggling of that charge over there isn't the effect of an electromagnetic wave acting on it. It is the effect of my jiggling this charge here. The rest — the generation of an electromagnetic wave here, its propagation, and its action on that charge over there — is a myth.

The first crack in this myth was caused by the nonexistence of a medium. Initially electromagnetic waves were thought to be vibrations of a "luminiferous ether." The Michelson-Morley experiment and Einstein's special relativity [Ed: dispelled] this notion.

But it takes more than that to dispell a myth. When nothing remains but an algorithm for calculating the effects of charges on charges, there is always the possibility of promoting select symbols of the algorithm to pukka [Ed: give credibility to] physical entities.

The next crack was caused by the "quantization" of electromagnetic radiation. First it was thought that only the emission of electromagnetic radiation takes place discontinuously. Later it was "found" that even the propagation of electromagnetic radiation has a discrete aspect. The myth of the photon was born.

Two myths that contradict each other are one too many. For a while it became the official line that anything closely enough observed was inseparable from the means of observation: all depends on how you look and what you look for. Photomultiplier tubes make you believe in photons; the frequency of photon detections as a function of position reassures your belief in waves.

Sanity, however, rarely prevails for long. The question of how it is that the properties of the quantum world must be observed in order to exist (which explains the undeniable dependence of what is observed on the means of observation) was soon swept under the rug and replaced by a variety of pseudo-questions. "Interpreting" the mathematical formalism of the quantum theory became synonymous with abolishing the extraordinary role that measurements play in standard axiomatizations of the theory.

Here is a question of the kind that quantum mechanics allows us to answer: if this atom here makes a transition to a state of lower energy, what is the probability with which that (perfect) photosensor over there clicks? Placed in a context that is "not even wrong," the question assumes its more familiar form: if this atom here emits a photon, what is the probability with which that (perfect) sensor over there absorbs it? ("Not even wrong" is Pauli's famous epithet for a story that cannot be proved wrong and thus fails to be scientific by Karl Popper's definition of "science.")

And here is a question of the kind that quantum mechanics fails to answer: if this atom here emited a photon and that sensor there absorbed it, how did the photon get from here to there? Since the fundamental theoretical framework of contemporary physics has no answer to this question, it stands to reason that the question is meaningless. Meaningless questions arise from false assumptions — in this case the assumption that if (i) this atom here makes a transition to a state of lower energy and (ii) that photosensor over there clicks, then something must have traveled from here to there.

Note that it would be wrong to say that the click over there was caused by the atomic transition here. The click could be said to have been caused by the transition only if the transition had made it necessary for the sensor to click. Yet the transition only made it possible. And for reasons that should now be obvious, it would be wronger still to say that the click was caused by a photon.

Suppose that two identical atoms are located at opposite corners of a square, that one sensor is located at each of the remaining corners, that the two atoms make identical transitions, and that both sensors click. Since sensor clicks happen without a cause, it makes no sense to ask: which click was caused by which transition?

Even if it were true that atom 1 and atom 2 both emit a photon and that sensor 1 and sensor 2 both absorb a photon, it would be wrong to assume that the photon absorbed by sensor 1 (say) is identical either with the photon emitted by atom 1 or with the photon emitted by atom 2. False assumptions give rise to meaningless questions — in this case the question: which photon was absorbed by which sensor?

This is an absolutely general feature of the manner in which quantum mechanics assigns probabilities to the possible outcomes of measurements: If you want to fabricate a story purporting to tell us what happened between consecutive measurements — in this case the initial measurement interpreted as indicating the emission of two photons and the final measurement interpreted as indicating the absorption of two photons — then you have to choose between different possible stories. And if nothing in the world — no actual event or state of affairs — indicates (or makes it possible to know) which of those stories is the true story, then none of them is the true story. For if you calculate the probabilities of measurement outcomes assuming that one of those possible stories is the true story, then the result of your calculation is inconsistent with what you observe if nothing [Emphasis added by ron] indicates which possible story is the true story.

Ten years ago, Dennis Dieks, professor of the foundations and philosophy of the natural sciences at the University of Utrecht, wrote:

[T]he outcome of foundational work in the last couple of decades has been that interpretations which try to accommodate classical intuitions are impossible, on the grounds that theories that incorporate such intuitions necessarily lead to empirical predictions which are at variance with the quantum mechanical predictions. However, this is a negative result that only provides us with a starting-point for what really has to be done: something conceptually new has to be found, different from what we are familiar with. It is clear that this constructive task is a particularly difficult one, in which huge barriers (partly of a psychological nature) have to be overcome.

In subsequent Quantum Tantrums we'll be looking at the psychological barriers that need to be overcome and at some of the positive results that have been obtained meanwhile.