It's ok to talk about reality with physicists, but with philosophers you never know what they mean!
Well, particularly due to quantum mechanics we have some things that are really reproducible exactly. E.g., any electron is precisely as any other, they are even indistinguishable in a very strict sense. Thus to the best of our knowledge each electron has precisely the same mass, magnetic moment, and charges of the standard model as any other. Of course, these quantities can be measured only with some finite accuracy, but so far even by getting this accuracy down to up to 12 significant digits (for the magnetic moment), there's no deviation from the assumption of indistinguishability. In this sense we have objective reproducible quantitative observations in nature in much better approximation than within classical physics.
That natural sciences are not sheer convention within a science community can be seen that indepedent researchers find the same result, measuring, e.g., the properties of elementary particles.
Mathematics is not philosophy. The mathematicians for already some time like to group mathematics into the category of "structural sciences" rather than "philosophy". Of course, mathematical physics (like axiomatic QFT) is not philosophy but an important part of physics (maybe also mathematics, but that the mathematicians have to judge). If I was a mathematical physicist I'd consider it an insult to be named a philosopher of science!
It's well known, why Fock wrote quite "interesting" philosophical articles concerning QT in Soviet times! I don't know, whether it's also in the English edition of Blokhintsev's famous QM textbook, but in the (then Eastern!) German edition there was also a "philosophical appendix"...
Scientific approach is based on assumption of realism (defined as "there is mind independent reality" or as opposite of solipsism). So the realism is common basis for any meaningful scientific discussion (this applies to positivists too). If you reject realism there can be no meaningful discussion with you about any science topic.
The scope of physics and its operational formalism is limited to pointer readings (the experience of what is called “observations”), which physics can study and connect to other pointer readings. There is no need for any assumption of realism or anti-realism or anything else. All these assumption belong to the realm of beliefs, personal “hypotheses” about yourself and about your experiences of “observations”.
I'm not sure what do you mean with "pointer readings". Do you mean either:
1) direct experience of expermentalist;
2) any type of record from which one can learn about certain measurement result?
I would use a slightly different wording but....yes, that is exactly correct.
In modern experiments, it will usually mean a record in a computer, not any direct experience, microsecond by microsecond. For experimental data to be really out there, it should be in "Supplementary Material", or at least available to other physicists on application. Where things get edgy is in the instrumental details of how the experimental apparatus was constructed, including how whatever exotic materials were used were exotically processed, where apparatus was sourced, what sources of noise were shielded and corrected for, et cetera, whchi all in all should be as much as is needed to reproduce the results.
So do the records of experimental data and setup details have mind independent existence?
I'd say, if anything is free of prejudices it's a "machine read" record of experimental results. Of course, these records are of no value, if one doesn't know, how the measurement devices and DAQ (i.e., both hard and software) has been constructed. E.g., at the LHC even the best DAQ technology cannot produce "raw data", i.e., there are hardware triggers already in the detectors before anything is stored to electronic storage. These triggers are to a certain extent constructed using models. It's not so clear to me, whether one really could perhaps through away interesting signals by such cuts. Recently there was an interesting article concerning the still mute search for particles beyond the Standard Model concerning possible long-lived candidates in the Quanta Magazine:
So one should be aware that there is indeed a subjective element in objective observations, that cannot be eliminated, namely the "arbitrary choice" of the observational apparati. I you'd say, e.g., only the direct human senses are valid, you'd miss a lot of stuff, which objectively exists: e.g., of the electromagnetic spectrum, restricting yourself what can be seen by the human eye, you'd exclude all em. waves at wavelenths outside the one octave from about 400 too 800 nm that can be seen directly by the human eye.
Nevertheless there's some objective reality in observations (particularly those not related to direct involvement of the human senses), because they are reproducible everywhere and at any time independently from each other, given a precise enough description of what is observed in terms of possible setups for measuring the concerning quantities. That becomse, of course, the more convincing if two or more such setups are also using different technology to measure the very same observable.
I'll mostly defer to vanhees71's account, comment #70. I think of triggers as a definite lossy data compression, but how the data is compressed is presumably decided by some committee, which hopefully has some minds. One could perhaps say that once an experiment has been constructed as an automated object, the data collected can be automated and be mostly independent of mind. Indeed, if human intervention is required to keep an experiment on track because of an error condition that lies outside the automation specified, one would expect that any data during the period during which human intervention was required ought to be discarded (unless, perhaps the human intervention can be formally modeled).
I'll paste in an account I wrote last night to a correspondent, which seems to be a propos:
One additional note, keying in to vanhees71's account, is that triggers for large experiments are usually much more elaborate (and can slip into dangerously ad-hoc territory) than just whether one electrical signal transitions from zero to non-zero.
I think it's best not to get too hung up on the Bishop Berkeley problem. Ultimately I can't see that it helps much to be solipsist about the world. Go to the world of extreme positivism for a visit if you like, which I've found occasionally useful as a way to get out of the box, but best to come back. I've been peppering everything I've written on PF with links to my arXiv:1709.06711 (comment #30 has a more up to date version attached) because that's how I think about QM/QFT (for which sorry, I guess) and it's not yet well-known, but for this specific question, I think its mathematical derivation of a random field as a subalgebra of a free quantum field algebra more reconciles a classical perspective and a quantum field perspective than any other math I've seen in the literature (there's a parallel with the de Broglie-Bohm approach, deriving trajectory probabilities from the wave function, but there are also fundamental differences, that I keep to the mathematics of operators acting on Hilbert space as a model for signal analysis, manifest Poincaré invariance is maintained, and I keep to an operational interpretation of the math as far as possible). One significant point, however, is that the philosophy of classical probability has become significantly less settled than it used to be. I'm happy with an instrumental, construct-an-ensemble-and-compute-statistics approach, which I think is what physicists do, but philosophers have worries that I find significant about that approach, and physicists who want to construct a model for the whole observable universe obviously can't construct an ensemble (also, if we take away the background Minkowski space, constructing an ensemble becomes quite fraught, AFAICT —amongst other worries, of course).
You have to find an answer for yourself to such a question. To my mind, it’s beyond the scope of "Physics" to answer this question or questions like “What is real?”. You can conceive that in course of experiments photographic plates have been blackened or that cloud droplets have been formed, without the intrusion of a conscious observer, but how should "Physics" prove your idea.
From an instrumentalist' point of view, such questions are idle ones. "In science we study the linkage of pointer readings with pointer readings." (Arthur Stanley Eddington). That’s all. The confusion begins when one tries on base of a schedule of pointer readings to draw conclusions as to the nature of “NATURE”.
Nevertheless, "Modern physics" now indicates that one cannot arbitrarily cut “NATURE” into – so to speak – subjective or objective parts or – let’s say – into Descartes’ mind and matter. Here I follow Bohr who said: I consider those developments in physics during the last decades which have shown how problematical such concepts as "objective" and "subjective" are, a great liberation of thought.
I just finished Part I of Adam's book. Did you read it? It speaks precisely against this attitude.
Why should physics prove anything?
Science requires two things to do it. First, you have to have creative thinking to come up with possible explanations of phenomena. And second, you have to have critical thinking to throw away useless explanations.
"Great liberation of thought" is good for creative thinking, but if you loose the critical thinking part as a result of this liberation ... well, it's just not going to work.
Indeed. Even the most appealing creative thought has to be confronted with observations and accurate measurements. If you cannot make contact to observables, it's a nice mathematical idea at best or just philosophical gibberish at worst. If your predictions are clearly countered by observation, it's a physical theory that's wrong and needs to be modified (at best) or abandoned (at worst)! As all natural sciences physics after all is an empirical science.
Sir Arthur Stanley Eddington in "The Nature of the Physical World“:
"Scientific instincts warn me that any attempt to answer the question “What is real?” in a broader sense than that adopted for domestic purposes in science, is likely to lead to a floundering among vain words and high-sounding epithets."
vanhees71, I can't see which comment you're referring to here. I understand if you might not want to use QUOTE, but it would help a lot if you would cite a comment number. TBH, I'm saying this because I've been unsure what or who you've been referring to a number of times, not just because of this one comment. Sorry! I won't say this again until I forget that I said it.
Did you read Adam's book?
I look forward to reading a review from you, RUTA. Having been to the talk Adam gave last night in New York, I'm not very enthusiastic. The last time I remember someone landing hard on a conversation at a foundations of physics conference with "Copenhagen says X, so everything you're saying is nonsense", was in the early 90's, and my sense is that physicists now more often fall back on decoherence (notwithstanding that the last mile from a mixed state to actual events is glossed), an interpretation which Adam didn't mention in his talk (I suppose because many philosophers would be loath to call decoherence an interpretation at all). Furthermore, I just read that Feyerabend in 1962 said (cited in arXiv:1509.09278, page 43)
which seems a clear statement, 56 years ago, of what seemed to be a large part of Adam's argument for why Copenhagen is still given lip service today.
Adam at one point said that he hopes to give his talk to physics departments, but TBH with nothing at all said about QFT (is there anything about QFT in the book?), and decoherence unmentioned, I can't see physicists taking him seriously. One high point of going to Adam's talk was that I talked to several Masters and PhD students and postdocs, all of whom seemed quite knowledgeable about and willing to talk about the interpretation of QFT.
Separate names with a comma.