B So can I use "wave particle duality?"

[Lord Jestocost]

Physics is about observable quantitative facts in nature and their (mathematical) description. Everything else is philosophy, and there's no doubt that there is some value in philosophy to get a bigger picture about the cultural meaning of established (sic!) theories. To get good philosophy about physics, you first need to get the physics strate. There's no way to get good philosophy from wrong assumptions (as, e.g., the idea that QT implies wave-particle duality, because that's a notion of an ill-defined historical step, usually called "old quantum theory", leading to QT and is abandoned by the now established QT).

Indeed, it's the great merit of Bell's work to have brought the ill-defined gibberish of EPR to a clear physical statement or better said a clear physical question to nature. A physical statement or question is a hypothesis that can be empirically justified. For me Bell's work and the subsequent experimental work following from, all of which in my opinion are of Nobel-prize caliber, is the only really valuable physics contribution arising from these socalled interpretational problems. The same holds for the various investigations on decoherence.

For me the upshot of all this is that QT is the best theory we have, including the facts (and these are facts precisely due to the quoted experimental work!) due to entanglement, which some people seem still to find "weird". The idea that these facts are weird, for me is (bad) philosophy. Since QT is an intrinsically consistent framework in terms of a physical theory (at least in the minimal statistical interpretation, for non-relativistic QT also Bohmian mechanics is a physically equivalent deterministic interpretation) there's nothing weird. It's just progress in our understanding of how nature observationally behaves in realms, for which our socalled "common sense" is not trained. Whether or not this is "sufficient ontology" is to everybody's personal taste, but it's not a question important to physics. Physical theories are epistemic anyway. Everything beyond this is metaphysics or even religion but not physics.

That Newton's physics book is called "philosophiae naturalis" is due to the simple historical fact as at this time physics didn't exist as a well-separated discipline, and everything connected with what we call "natural sciences" today was part of philosophy, namely philosophia naturalis. The clear distinction between the disciplines (most roughly in humanities, natural sciencs, and structural sciences) has been established only later when it turned out that specialization is nessary for all these different disciplines to get further into more complicated issues and knowledge. That's why it is so important to keep these realms strictly separated!

I can agree with most, but when hearing “minimal statistical interpretation”, I just cannot get rid of the thought that behind this interpretation there lurks the idea that quantum mechanics must be supplemented by some kind of hidden variables operating from behind the scenes.

 

[DarMM]

Physics is about observable quantitative facts in nature and their (mathematical) description. Everything else is philosophy, and there's no doubt that there is some value in philosophy to get a bigger picture about the cultural meaning of established (sic!) theories

You're not wrong from a certain perspective, but I think we have to keep in mind what motivates people. I doubt Einstein was motivated by explaining the measurement statistics of ensembles of equivalence classes of suitably prepared astronomical observation equipment when he came up with GR. He wanted to understand how the world worked, i.e. the ontology.

There is a good argument that QM forces a very positivist view of physics and that the searching for an ontology for it is misguided, but this is a bit of a break from why most people get into physics. Perhaps you're just more empircally disciplined than the rest of us!

 

[stevendaryl]

QM is a theory to predict the probabilities of various directly observed macroscopic outcomes within a certain experimental setup, let’s say an “electron” diffraction experiment. If you like, you can now think of the “electron” as some kind of “real object” you are studying, but you are then entering the area of metaphysics. The reality** you experience is in the observations, not in the “electron”. And what will you gain by this step with regard to physics as exact science? Nothing, because only observations themselves and their correlations are handled in physics. Or, maybe, you will gain the extra trouble of digging your “real object” out again from your thinking.

But presumably, the only reason that it is possible to make observations is because we are ourselves systems described by physics, and we interact with the thing we're studying through physical interactions. Treating observations as primary seems like solipsism, to me. As if humans were disembodied minds.

It's kind of funny; in my mind, the people who most strongly object to "philosophical" discussions are the ones who have the most rigid philosophical systems.

Science, to me, is about understanding the world. That's the reason that people are interested in science. They see rainbows and want to know what are they. They see magnets work, and wonder how that is possible. They see the stars and wonder what they are, and how they are powered. Understanding the universe is the goal of science, in my opinion (or probably in the opinion of anyone who ever was interested in science, before they became indoctrinated in the anti-philosophy philosophy). Being able to make predictions about measurement results is a test of understanding. That's what's so great about empirical science, is that mistakes can be corrected. But making predictions isn't the reason that people are interested in science. To me, that's like saying that the point of studying mathematics is to be able to pass mathematics tests.

 

[DarMM]

But presumably, the only reason that it is possible to make observations is because we are ourselves systems described by physics, and we interact with the thing we're studying through physical interactions. Treating observations as primary seems like solipsism, to me. As if humans were disembodied minds

I think most of the views of QM where observation is a primary concept take it as a primitive of the theory, but not of the world. Sort of like how decision theory has an agent as a primitive, but that doesn't mean you think an "agent" is an irreducible physical property.

 

[PeterDonis]

This is way too much argument about the philosophy of QM for a "B" level thread.

It looks like a fair "B" level summary would be that, while there might be some limited ways in which the concept of "wave-particle duality" is useful, it's probably better to ignore it.

And with that, this thread is closed.