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[Quotidian]

Another one of the well known sound bites associated with quantum theory is: "shut up and calculate!" (I've heard it attributed to Richard Feynman. Could be wrong.)

This often seems to be interpretted as simply a dictatorial expression of arrogance. I think it is really a practical statement about what it is possible, and not possible, to definitively say about the world using science.

Actually I have a rather better explanation, but it is complicated. The summary version is like this. When the implications of quantum mechanics were being thought out in the 1920's by Heisenberg, Schrodinger, Bohr, Pauli, and Einstein, among others, there was a lot of intense philosophical debate about what it really meant. Einstein was very antagonistic to the strange philosophical implications, as per his statements about 'spooky action at a distance' and 'God does not play dice'.

Heisenberg and Schrodinger were both philosophically deep thinkers. Schrodinger, for instance, had a life long interest in Arthur Schopenhauer and tended towards philosophical idealism. Heisenberg wrote a well-regarded book on Physics and Philosophy which is still in print, and which featured insightful analyses of Greek philosophy.There was a range of view, of course, ranging from uncompromising positivism on one side, to the mystical and mind-oriented interpretations on the other, and many more in between.

However in the post-war period most of the action shifted to the US. Unlike the Europeans, many of the Americans were not philosophically reflective, and this is where the 'shut up and calculate' attitude originated. This is because despite the strange philosophical implications of QM, it is an extremely accurate and effective theory that has been applied very successfully to an enormous range of technologies, particularly lasers and integrated electronics. These activities can be carried on quite happily without thinking about 'spooky action at a distance', which still remains, however, a skeleton on science's closet, to mix metaphors pretty dreadfully.

Have a look at http://phys.org/news163670588.html

[Steve3007]

Mmm. So it's a function of the no nonsense, down to earth bongo playing practicality of Americans eh. I'm warming to them.

Seriously though, I have no problem with skeletons in closets, if by that we mean interesting things yet to be discovered. Your explanation of the origins of this practical "non philosophical" attitude is interesting. I guess my point was shallower: simply drawing attention to what the attitude actually involves without exploring its historical context.

I think it boils down again to a proper definition of what science can and cannot do. Patterns in observations. As you've pointed out, the patterns in observations yielded by quantum theory have been very useful in predicting future observations, as illustrated by the technological spin-offs from those predictions. What will happen in the future? Either we'll find more patterns or we'll discover that there is a point where the patterns stop and science can go no further. Interesting either way.

[Quotidian]

The 'mystical interpretations of QM which some of the first generation of QM physicists arrived at, were fiercely resisted by some of their contemporaries, and are even more so nowadays. That is why it is a controversial topic, especially for those who suppose the antagonism of the mystical and the scientific.

But consider this: of all of the interpretations of Quantum Theory that are now favoured, Everett's MWI is a leading contender amongst theoretical physicists. This model proposes that there are many, perhaps an infinite number, of branching universes, within which a countless number of alternative futures unfold and play out.

MWI is an extravagantly strange idea, yet many physicists will argue for it. This says to me, that the philosophical problem that it is attempting to solve, must be a pretty big one.

[A Poster He or I]

With all due respect to the valuable exchange of the last few posts, I beg to differ. I think that Everett's MWI is taken seriously by numerous physicists because of how it AVOIDS philosophical entanglements for quantum theory. I believe Quotidian may be saying this when he says, "the philosophical problem that it [MWI] is attempting to solve, must be a pretty big one." But my point is that MWI allows physicists to avoid even acknowledging that there even exists a philosophical problem. How? Because MWI eliminates the collapse of the Schroedinger wave function. There simply is no such thing as collapse which means no problem (neither scientific nor philosophical) of how deterministic unity arises from evolving probabilities.

Such physicists prefer to allow the math to be the full story of quantum mechanics, even if the implication is a multiverse (conveniently unsubjectable to scientific verification), rather than have no scientific model for how deterministic unity is experienced from the wave function.

[Quotidian]

But, don't you think that MWI avoids 'philosophical entanglements' at an enormous cost? In other words, you have to accept that there are 'countless branching universes' existing in parallel to this one. I don't see how this is LESS embarrassing than the collapse issue EXCEPT that it enables you to dodge the 'observer problem'. It also kind of shoves it into the realm of metaphysics, of a kind. So, we agree that there are multiple branching universes, and the problem goes away. So, as I say - must be some problem!

[A Poster He or I]

You have said it better than I thought of how to say it: it dodges the observer problem.

At enormous cost? Yes, very much so to you and me who are not directly invested in upholding the integrity of existing quantum mechanics' extraordinary ability at calculation. But to those who must rely on that calculative power, there is (for some) no cost too great if it buys the ability to stay safely within the domain of existing scientific formalism.

EDIT: I can also agree that it sort of shoves the whole issue into metaphysics. But then that is convenient for scientists also who have no need to model metaphysical phenomena per se. In other words, the problem is philosophical exclusively and therefore of (potentially) no interest to those scientists who buy into MWI.

[Quotidian]

Here is a great summary of the issues I got from googling 'the observer problem':

Bohr’s “Copenhagen interpretation”, which became orthodoxy for most of the century, still has the power to shock. What it states, baldly, is that reality is determined by the experiment the scientist chooses to perform. One kind of experiment will cause light to behave like a particle; another kind will make it act as a wave. There is no underlying truth about what light “really” is. And an electron doesn’t have a definite position in space before you choose to measure it: in measuring it, you somehow oblige it to make up its mind as to where it is. (Heisenberg’s uncertainty or “indeterminacy” principle, by the way, says that if you come to know an electron’s position in this way, its momentum cannot also be accurately known; and, crucially, that this is not just a function of our experimental limitations, but the truth about electrons. If an electron has a definite position, it simply does not have a definite momentum, and vice-versa.)

So reality is a kind of mischievous oracle, answering only when directly questioned. Erwin Schrödinger’s famous imaginary cat (inspired in part by an exchange of letters with Einstein) was intended as a reductio ad absurdum of this conception. The cat in question is locked in a box, together with a crumb of radioactive material, which may or may not decay in the course of an hour. If the crumb decays, it will set off a mechanism that poisons the cat. After an hour, what can you say about how the cat is doing without opening the box? Intuitively, it’s obvious: either the cat is alive, or it isn’t. But, said Schrödinger, a quantum theorist would be obliged to say that the box contained “the living and the dead cat [...] mixed or smeared out in equal parts”. According to Copenhagen, there is no truth about the cat’s alive-or-deadness until someone opens the box and observes it.

Perhaps the most embarrassing question asked of the Copenhagen interpretation was a version of the cat paradox scaled up to cosmic size. Copenhagen says that nothing is definitively so until an act of observation “collapses the wave-function” of the system in question (condensing, so to speak, a cloud of probability into one thing or another). If that is true, how did the universe itself begin? What monstrous (or maybe divine) act of observation could have collapsed the wave-function of the entire universe so as to promote it to physical reality? Some physicists subsequently adopted a “many-worlds interpretation”, which envisioned an endlessly branching multiplicity of universes. It might have shut down the original-observation question, but only at the price of an uncomfortable ontological profligacy.

Kumar’s story finishes by noting the results of a 1999 poll of physicists at a Cambridge conference as to which interpretation of quantum mechanics they preferred. Of 90 respondents, “only four voted for the Copenhagen interpretation, but 30 favoured the modern version of [...] many worlds. Significantly, 50 ticked the box labelled ‘none of the above or undecided’.” The question of the ultimate nature of reality is, it seems, still a live problem. Somewhere, Einstein is puffing on his pipe and smiling ironically.

Source is http://stevenpoole.net/articles/the-observer-problem/

The book that is a review of looks great, incidentally. Having just finished John Gribben's bio of Schrodinger, I might order it.

[Steve3007]

I wonder how many would have ticked a box labelled "shut up and calculate!".

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This is a subject that seems to have been done to death on this forum since I've been on it. But then, I guess that's because it's just so darn interesting and seems to get people all riled up for various reasons. So what the heck.

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I studied physics at University so naturally studied quantum mechanics quite a lot. But (1) it was a long time ago and I've forgotten most of it apart from vague general ideas and (2) in an undergraduate physics course (in my experience) there's relatively little discussion of the philosophical issues and also relatively little discussion of the historical context. Of course the subject does tend to be taught, from high school onwards, chronologically and there are some discussions of the historical context in which discoveries are made. But there was virtually no discussion, for example, of the general philosophical leanings of the leading figures in the subject like Bohr, Schrodinger, Heisenberg, Einstein, Pauli, Dirac and so on. You learn how to use the time dependent Schrodinger equation and the Pauli spin matrices, and you learn the underlying principles on which they are based, and the experimental evdence that lead to the creation of those principles, but you don't discuss the philosophical leanings of these two people.

Whether this is a good or a bad thing I'll leave as an open question. Perhaps, given the time constraints, philosophical implications are best left as extra-curricular discussion subject. Perhaps not.

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Regarding the passage quoted in the previous post:

I think the subtlties of wording can be all important when trying to describe subtle subjects like this one using such a blunt instrument like the English language. I don't fully agree with the description of the Copenhagen Interpretation given in the first paragraph. That's not quite my interpretation of it!

What it states, baldly, is that reality is determined by the experiment the scientist chooses to perform. One kind of experiment will cause light to behave like a particle; another kind will make it act as a wave. There is no underlying truth about what light “really” is.

The Copehagen Interpretation is itself the subject of different interpretations by different physicists so hopefully I'm not being too presumptuous by giving a little of my own.

I don't think it has to be interpretted as saying that there is no underlying truth about what light "really" is. I think the mistake that is often made is in thinking that the words "particle" and "wave" are being used to signify anything more than mathematical models. These two words, in this context, are shorthand terms for little packages of mathematical description. They are not words for objects. Of course, they are derived by analogy with some aspects of observable objects: billiard balls, bullets, density distributions in air, the shape of a water surface and so on. But they are abstractions.

So, since light is not a billiard ball or a bullet or a piece of water, it should not be surprising that it does not wholly behave like any of these things. There are some aspects of it, in some circumstances, that resemble some aspects of these things, and other aspects, in other circumstances, that resemble other aspects of these things.

So, some sets of observations regarding light are best modelled using the set of mathematics referred to as "wave" and others are best modelled using the set of mathematics referred to as "particle". The underyling truth about what light "really" is, is that it is light. In the same sense, the underlying truth about what a billiard ball really is is that it is a billard ball. As soon as you say something different you are starting to create an abstract idealized model and you should recognize that, in accordance with the definition of the concept of a model, it is incomplete and a generalization.

[Xris]

Your starting to sound like my ally Steve , be careful you might start listening to cranks and charlatans. What if mainstream science has no alternative to these quantum anomolies? Do we or should we listen to any one who might have an alternative? Any voice of dissent has to be examined or we will never overcome these strange anomolies that the vast majority simply accept. How many realise that the photon is a mathematical concept and not a little pesky schizophrenic particle? Take my recent question to you. The radio programme almost insisted it is essential that you believe in the BB before you can accept the high priests have discovered the god particle.

[Steve3007]

Your starting to sound like my ally Steve

You'll never take me alive!

Seriously, though, listening (vaguely) to that programme with my "Xris ears" on, I can concede that you have a valid point about that kind of presentation of science. On your other points, well I'm sure we're both just repeating things we've said before, but:

Do we or should we listen to any one who might have an alternative? Any voice of dissent has to be examined or we will never overcome these strange anomolies that the vast majority simply accept.

Yes. But there are 7 billion people in the world and most of them (it sometimes seems) have written a densely packed 1000 page book with extensive references setting out their worldview. It's the details of the filtering system that we're arguing about.

How many realise that the photon is a mathematical concept and not a little pesky schizophrenic particle?

How many think about the subtle distinctions and concepts of modern physics? Hardly any, I imagine. More important things to think about.

[Xris]

So what was the answer to my question? Did it ask us to accept the BB as a consequence of believing they have found the god particle? It is not a flippant question. The guy who recommend we believe in the quantum soul has spent thirty odd years investigating and learning his trade. If you question him from subjective and less informed position than him are you questioning science and all the technical advances quantum science has given us? We are expected on a regular basis to accept science and certain findings with a kind of religous obedience. Like the priest who tells us just be grateful god has fed you today, so to must we be simply grateful we have a digital TV. I have watched at least three programmes in the last four weeks where the BB is spoken of as if it was as certain as the sun will shine tomorrow. Not one has even mentioned that there are those who seriously oppose this concept. If you question this quantum soul how do you differentiate it with any other concept that might arrive at our door? Light as photon particle created the BB as a concept but now you are openly admitting it is not a particle. I am afraid you have moved to the dark side Steve. There is no hope for you.

[Steve3007]

So what was the answer to my question? Did it ask us to accept the BB as a consequence of believing they have found the god particle?

I don't know. I wasn't listening carefully enough.

The guy who recommend we believe in the quantum soul has spent thirty odd years investigating and learning his trade. If you question him from subjective and less informed position than him are you questioning science and all the technical advances quantum science has given us?

Roger Penrose? I don't know. It depends what question you ask. You certainly have the right to question him although of course you have to be clear you know what he's saying. If it's any comfort, many other people disagree with him on this subject, apparently.

We are expected on a regular basis to accept science and certain findings with a kind of religous obedience.

You are free to disagree. No violence or persecution will result. No worship required.

I have watched at least three programmes in the last four weeks where the BB is spoken of as if it was as certain as the sun will shine tomorrow. Not one has even mentioned that there are those who seriously oppose this concept.

You'll have to take that up with the editors.

If you question this quantum soul how do you differentiate it with any other concept that might arrive at our door?

Not sure what this one means.

Light as photon particle created the BB as a concept

No idea what this one means. Sounds like a clue from a cryptic crossword.

but now you are openly admitting it is not a particle. I am afraid you have moved to the dark side Steve. There is no hope for you.

Don't remember "admitting that light is not a particle". I remember giving some of my thoughts on how mathematical models work in science.

[Xris]

Suddenly realised you have a reverse gear? Everything that I oppose is based on the photon as a concept. Photon the particle that is not particle. Yes I know we have been here before but did we ever resolve the issue? You are the first and only who has had the ability to admit that it is a mathematical invention and now you appear to find the dark side too frightening.

[Quotidian]

We are expected on a regular basis to accept science and certain findings with a kind of religous obedience.

Isn't this, and variations on it, your only argument?

[Xris]

(Nested quote removed.)


Isn't this, and variations on it, your only argument?

Most arguments are based on one principle. What exactly is my argument if you are so aware of it?