What is Light? The Mystery Continues

J. J. Thomson

R. C. Dynes

We introduce an intuitive particle-based model of time-symmetric quantum physics that gives a concrete description of what goes on in the time between projective measurements of a quantum system. The time-symmetry in this model means that we ...Physical interpretations of the time-symmetric formulation of quantum mechanics, due to Aharonov, Bergmann, and Lebowitz are discussed in terms of weak values. The most direct, yet somewhat naive, interpretation uses the time-symmetric formulation to ...

E. Lommel

Richard Joseph Oldani

Feynman referred to interference as “the only mystery,” and we continue to pursue that idea here by examining the theory behind it with heightened scrutiny. Three interpretations are described: The standard model, Feynman’s sum-over-paths, and Einstein’s photon model. The standard model bases its arguments on the wave function and its subsequent collapse. The sum-over-paths model is equivalent to the standard model, but it explains interference by avoiding use of the wave function and its conceptual problems due to collapse. The Einstein model is the most challenging for it is revolutionary and intuitively demanding. We critique the three models by studying their treatment of polarized light. In Part II, the interference of low intensity light will be discussed.

J. B. Kennedy

Peaceful coexistence For a hundred years, physicists trumpeted the celestial speed limit. Einstein has shown, they said, that nothing travels faster than light. But for a generation now, there has been stunning experimental evidence that hints that some mysterious influences are travelling faster than light. Contemporary physics rests on two great pillars. Einstein's theories describe the large-scale structure of space and time. Quantum theory describes the small-scale behaviour of matter within space and time: the behaviour of molecules, atoms and other particles. Roughly, one describes the container, and the other the contents. Although research continues, the two traditions are so much at variance that no one has been able to combine them into a single, unified theory or “theory of everything”. Quantum theory emerged piecemeal over many years and its development was driven by experimental results and mathematical guesses. Like most committee efforts, quantum theory was a patchwork of conflicting motivations and strategies. There is one central obstacle to unification: even today no one really understands quantum theory. For many years, relativity and quantum theory led a peaceful coexistence. The mysteries of quantum theory were dramatized by a series of paradoxes, but the theory worked very well and never threatened to contradict and overthrow its rival. But now things are changing. Recent experiments are revealing that quantum theory is even more strange than expected. Sometimes it appears as a great, conceptual black hole that sucks down into it every attempt to clarify the foundations of physics.

James W. Robinson