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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: 3, Informative) by boristhespider on Friday May 22 2015, @09:51PM
Seriously, who gives a flying fuck? The point of physics isn't to give us a warm feeling that we know what the universe is, but instead to give us a set of algorithms that we can apply in given regimes to given inputs, which produce outputs that we have tested against experiment. If those algorithms happen to be well-motivated compared to pre-existing physical algorithms, and happen to be mathematically elegant, that's all the better. But this kind of futile, facile debate over what the wavefunction is strikes me as utterly and entirely pointless. Is it the square the wavefunction the probability density of some quantum system? Sure, why not? That fits every observation we've made. Is it instead a complex combination of the square root of a fluid density along with the momentum potential of a fluid? Sure, why not? That fits every observation we've made. The theories those two definitions give rise to are absolutely identical at the observational level - and beyond that, what are you expecting physics to be? It's a description of the universe. Interpretations of those descriptions might give you a basis upon which to attempt to build a picture of the universe, but one should *always* be aware of what, describing what we expect to observe given a particular set of inputs.
There's no hand-holding here, no "realism", whatever you mean by that, and particularly no "psychic" connections to reality - assuming you meant the word "psychic". Merely descriptions of reality that physicists attempt to ensure are consistent, particularly where successful theories in their own regimes (such as quantum mechanics and general relativity), and which are nothing more than that. The universe *behaves* on a small scale as if QED is astonishingly accurate - indeed, the most accurate theory we still possess. The universe *behaves* on a larger scale as if the only forces are electromagnetism, acting according to Coulomb's law, and gravity, acting according to general relativity. Does that mean that nature is geometric? Of course not. Does that mean that nature is filled with virtual particles? Of course not. It might mean both of these. It may well mean neither. Who knows? And frankly, who cares?
Physics describes how things behave and does so extremely well. It then attempts to describe how things behave with as small a theory and as few assumptions as possible. It does *not* state what the universe is. Merely how it behaves, in particular scenarios.
(Score: 2) by aristarchus on Friday May 22 2015, @10:07PM
Seriously, who gives a flying fuck? The point of physics isn't to give us a warm feeling that we know what the universe is,
According to the FA, apparently Maroney does! I am glad to see you intervene, Boris, you are always spot on, and we do not disagree at all. But the tendency of scientists to engage in ontology without a license is unfortunately very real, perhaps more with popularizers than with actual theorists. And I can't recall how many crackpots I have heard of who keep insisting that all of modern science is a fraud, or that Einstein was wrong, or that string theory is a real thing. Maybe the word I was looking for, in connection to the pure and correct perception of reality, was more "psycho" than "psychic".
(Score: 2) by boristhespider on Friday May 22 2015, @10:33PM
I think I disagree with him :)
Unfortunately, and to be honest, I've known too many people in theory who have started to talk as if the theory is reality. It's understandable - we're working day in and day out with a description of nature that we can't disprove; of course we think that's what nature *is* rather than merely a description of how it *behaves* - but it does genuinely annoy me. Not least as those same people will start a project the next month working on inflationary phenomenology which takes as an assumption some hand-waved consequence of M theory (meaning that the description of reality we agreed on the week before absolutely has to be inaccurate), and argue just as vehemently that quantum esotericism is how nature is as the week before they argued that higher-dimensional fatalism was. I think it's down to loose language on their part, since I'm very definitely not pretending I'm one of the few cosmologists of my generation with a grip on reality, but I do think I might be one of the relatively few to want to avoid such loose language...
So I think that actual theorists can be as much at fault as anyone (and I've probably been in the past). At least I wouldn't say Einstein was wrong, even though he was about the EPR paradox, and about his attempts at a unified field theory, etc. - the way people mean it is they mean "special relativity is wrong!", which it basically isn't, or "general relativity is wrong!", which it isn't in its realms of validity, etc...
Personally, I like to view myself as a pragmatist. Ultimately, we *know* that nature acts, at high energies and on small scales, as if QED is reality. On larger scales, we *know* that it acts as if quantum mechanics is reality, and we can pretend that the one implies the other (good luck proving that one, but the theories are at least closely enough related people won't argue). But, alas, we *know* that on larger scales (and in reasonably low gravitational fields) it acts as if general relativity was the reality, and neither QED nor QM agree with that. Shitter. Maybe we'll reconcile these descriptions one way or another and maybe we won't. Personally, I don't have a huge issue if we don't. I know how to describe QM on a curved background (it's nasty, but we can do it, even if it plays merry hell with our definition of a vacuum state), and I know how to do QM on a flat background and gravity with classical fields. And if we do that's ace - we simply have a neater description of how the universe appears to behave, which can hold up until we find too many weird oddities to continue to believe it...
In the meantime, I'm happy to do my research in GR since no matter what we find, in the regimes I work in, GR is probably not going to be invalidated - except perhaps in the recent or the extremely early universes.