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Owen Maroney worries that physicists have spent the better part of a century engaging in fraud.
Ever since they invented quantum theory in the early 1900s, explains Maroney, who is himself a physicist at the University of Oxford, UK, they have been talking about how strange it is — how it allows particles and atoms to move in many directions at once, for example, or to spin clockwise and anticlockwise simultaneously. But talk is not proof, says Maroney. “If we tell the public that quantum theory is weird, we better go out and test that's actually true,” he says. “Otherwise we're not doing science, we're just explaining some funny squiggles on a blackboard.”
It is this sentiment that has led Maroney and others to develop a new series of experiments to uncover the nature of the wavefunction — the mysterious entity that lies at the heart of quantum weirdness. On paper, the wavefunction is simply a mathematical object that physicists denote with the Greek letter psi (Ψ) — one of Maroney's funny squiggles — and use to describe a particle's quantum behaviour. Depending on the experiment, the wavefunction allows them to calculate the probability of observing an electron at any particular location, or the chances that its spin is oriented up or down. But the mathematics shed no light on what a wavefunction truly is. Is it a physical thing ? Or just a calculating tool for handling an observer's ignorance about the world ?
http://www.nature.com/news/quantum-physics-what-is-really-real-1.17585
(Score: 5, Insightful) by maxwell demon on Friday May 22 2015, @07:37AM
A physical theory being "realist" does not mean it agrees with reality. I can make realist theories which do not in any way relate to our observations (those are obviously not good theories, as they are falsified by observation, but "realist" and good are orthogonal to each other). A physical theory being "realist" is just a fancy word for not giving the observer a special status in the theory.
Classical physics is realist not because it agrees with reality (we already know it doesn't when considering atoms), but because in it observers have no special status; as far as the theory is concerned, they are just physical systems like any other. Standard quantum mechanics is not realist because there observation is governed by different laws than unobserved evolution. The problem with this is that we don't have an in-theory description of what process does or doesn't qualify as observation. So we have to handwave the problem away by just noting that for the processes currently accessible to us, we know which are to be described as measurements and which have to be described as unobserved evolution. The problem is exaggerated by the fact that you can move the border between "still quantum evolution" and "now measurement" quite a bit without changing the results.
The appeal of a realist theory is that it does away with the whole problem. If the observer is nothing but a specific physical system, the question when a measurement occurs is no longer a physical question; it becomes a question of interpretation, and thus manifestly unphysical.
A realist theory in the physical sense does not imply realism in the philosophical sense. Now, of course many people (including many physicists) don't keep those concepts separated, and that's IMHO a big source of confusion. Using the same word for both concepts of course doesn't help either.
The Tao of math: The numbers you can count are not the real numbers.