{"id":2908,"date":"2012-05-10T10:05:55","date_gmt":"2012-05-10T09:05:55","guid":{"rendered":"http:\/\/emilkirkegaard.dk\/en\/?p=2908"},"modified":"2012-05-10T10:08:23","modified_gmt":"2012-05-10T09:08:23","slug":"thoughts-about-a-very-short-introduction-to-quantum-theory-john-polkinghorne","status":"publish","type":"post","link":"https:\/\/emilkirkegaard.dk\/en\/2012\/05\/thoughts-about-a-very-short-introduction-to-quantum-theory-john-polkinghorne\/","title":{"rendered":"Thoughts about: A very short introduction to quantum theory (John Polkinghorne)"},"content":{"rendered":"

Quantum Theory – A Very Short Introduction<\/a><\/p>\n

I have recently been in some discussions about the interpretation of quantum mechanics and the potential consequences of those interpretations. My chief opponent (we may call him) is a Copenhagen interpretation theorist. He has some rather odd views that are incoherent in themselves but apparently common among fysicists (as we will see).<\/p>\n

My position has been one of realism+indeterminism. I came to this position some years ago after reading up on QT on a rather sporadic basis (mostly Wikipedia) and reading a paper by one of my favorit filosofers: Raymond Bradley<\/a>.<\/p>\n

Raymond D. Bradley – How to lose your grip on reality An attack on anti-realism in quantum theory<\/a> (his paper)<\/p>\n

It seems to me that Bradley is completely right about verificationism: it is an incoherent theory of meaning. However, i decided to take a closer look at the fysics involved. Admittedly, i did not want to learn everything that someone who takes a bachelor in fysics learns, so i decided to read some books written for laymen by experts. I decided on reading four books from the series A very short introduction to …<\/em> series. These are: The Elements<\/em>, Relativity<\/em>, Quantum Theory<\/em>, and Particle physics<\/em>. QT is the third book. I probably shud have chosen another order so that QT was the last to read, but too late now.<\/p>\n

What follows are some quotes from the book and my thoughts about them. I don’t bother to cite the page since i uploaded the ebook. Anyone wishing to find the page can just do a search in the pdf.<\/p>\n

–<\/p>\n

The measurement problem continues to cause us anxiety as we
\ncontemplate the bewildering range of, at best, only partially
\npersuasive proposals that have been made for its solution. Options
\nresorted to have included disregard (irrelevance); known physics
\nDarkening perplexities
\n(decoherence); hoped-for physics (large systems); unknown new
\nphysics (GRW); hidden new physics (Bohm); metaphysical
\nconjecture (consciousness; many worlds). It is a tangled tale and
\none that it is embarrassing for a physicist to tell, given the central
\nrole that measurement has in physical thinking. To be frank, we do
\nnot have as tight an intellectual grasp of quantum theory as we
\nwould like to have. We can do the sums and, in that sense, explain
\nthe phenomena, but we do not really understand what is going on.
\nFor Bohr, quantum mechanics is indeterminate; for Bohm,
\nquantum mechanics is determinate. For Bohr, Heisenberg\u2019s
\nuncertainty principle is an ontological principle of indeterminacy;
\nfor Bohm, Heisenberg\u2019s uncertainty principle is an epistemological
\nprinciple of ignorance. We shall return to some of these
\nmetaphysical and interpretative questions in the \ufb01nal chapter.
\nMeanwhile, a further speculative question awaits us.<\/p>\n

Notice how the author contrasts an antirealims+indeterminism view with a realism+determinism view. However, these are not the only options. At least, the option of indeterminism+realism is possible. I’m not sure about the antirealism+determinism position. It seems to be ‘claiming’ that everything that happens in the quantum world (or the world at large) has a cause, but that there are no subatomic particles before we measure them. This is odd. The first possibility i suggested is that one that i like the most.<\/p>\n

–<\/p>\n

The EPR effect\u2019s implication of deep-seated relationality present in
\nthe fundamental structure of the physical world is a discovery that
\nphysical thinking and metaphysical re\ufb02ection have still to come to
\nterms with in fully elucidating all its consequences. As part of that
\ncontinuing process of assimilation, it is necessary to be as clear as
\npossible about what is the character of the entanglement that EPR
\nimplies. One must acknowledge that a true case of action at a
\ndistance is involved, and not merely some gain in additional
\nknowledge. Putting it in learned language, the EPR effect is
\nontological and not simply epistemological. Increase in knowledge
\nat a distance is in no way problematic or surprising. Suppose an urn
\ncontains two balls, one white, the other black. You and I both put in
\nour hands and remove one of the balls in our closed \ufb01sts. You then
\ngo a mile down the road, open your \ufb01st and \ufb01nd that you have the
\nwhite ball. Immediately you know I must have the black one. The
\nonly thing that has changed in this episode is your state of
\nknowledge. I always had the black ball, you always had the white
\nball, but now you have become aware that this is so. In the EPR
\neffect, by contrast, what happens at 1 changes what is the case at 2.
\nIt is as if, were you to \ufb01nd that you had a red ball in your hand, I
\nwould have to have a blue ball in mine, but if you found a green ball,
\nI would have to have a yellow ball and, previous to your looking,
\nneither of us had balls of determinate colours.<\/p>\n

I agree that the analogy works from the pov of someone who thinks that antirealism about QM stuff is true. I still don’t. It’s going to be very hard to convince me i am wrong about this.<\/p>\n

–<\/p>\n

An alert reader may query all this talk about instantaneous change.
\nDoes not special relativity prohibit something at 1 having any effect
\nQuantum theory
\n80at 2 until there has been time for the transmission of an in\ufb02uence
\nmoving with at most the velocity of light? Not quite. What relativity
\nactually prohibits is the instantaneous transmission of information,
\nof a kind that would permit the immediate synchronization of a
\nclock at 2 with a clock at 1. It turns out that the EPR kind of
\nentanglement does not permit the conveyance of messages of that
\nkind. The reason is that its togetherness-in-separation takes the
\nform of correlations between what is happening at 1 and what is
\nhappening at 2 and no message can be read out of these correlations
\nwithout knowledge of what is happening at both ends. It is as if a
\nsinger at 1 was singing a random series of notes and a singer at 2
\nwas also singing a random series of notes and only if one were able
\nto hear them both together would one realize that the two singers
\nwere in some kind of harmony with each other. Realizing this is so
\nwarns us against embracing the kind of \u2018quantum hype\u2019 argument
\nthat incorrectly asserts that EPR \u2018proves\u2019 that telepathy is possible.<\/p>\n

I have seen the claim before, that SR implies that no FTL communication is possible. I don’t see how it follows from the information presented earlier in the book or the introduction to relativity that i read last week.<\/p>\n

I have thought up a method for FTL communication. Not sure if it works, probably doesn’t and i’m wrong about some fysical detail, not being a fysicist and all. One takes alot of these entangled particles. Then separates them into two boxes, such that all of those in one box are of the same type of spin, and the same for the other box. Then one ships the one box to out in space with a spaceship. To communicate, one changes the spin of the particles in the box, and the other party can see this change too (becus it is instantaneous). I’m thinking that this method doesn’t work becus of one of the following: 1) it is not possible to separate them into the boxes as described, 2) there are some problems with changing one of the particles and then having the other people measure this without destroying the signal.<\/p>\n

–<\/p>\n

Positivism and realism<\/strong>
\nPositivists see the role of science as being the reconciliation of
\nobservational data. If one can make predictions that accurately and
\nharmoniously account for the behaviour of the measuring
\napparatus, the task is done. Ontological questions (What is really
\nthere?) are an irrelevant luxury and best discarded. The world of the
\npositivist is populated by counter readings and marks on
\nphotographic plates.
\nThis point of view has a long history. Cardinal Bellarmine urged
\nupon Galileo that he should regard the Copernican system as simply
\na convenient means for \u2018saving the appearances\u2019, a good way of
\ndoing calculations to determine where planets would appear in the
\nsky. Galileo should not think that the Earth actually went round the
\nSun \u2013 rather Copernicus should be considered as having used the
\nsupposition simply as a handy calculational device. This face-saving
\noffer did not appeal to Galileo, nor have similar suggestions been
\nfavourably received by scientists generally. If science is just about
\ncorrelating data, and is not telling us what the physical world is
\nactually like, it is dif\ufb01cult to see that the enterprise is worth all the
\ntime and trouble and talent expended upon it. Its achievements
\nwould seem too meagre to justify such a degree of involvement.
\nMoreover, the most natural explanation of a theory\u2019s ability to save
\nappearances would surely be that it bore some correspondence to
\nthe way things are.
\nNevertheless, Niels Bohr often seemed to speak of quantum theory
\nin a positivistic kind of way. He once wrote to a friend that
\nThere is no quantum world. There is only abstract quantum physical<\/em>
\ndescription. It is wrong to think that the task of physics is to \ufb01nd out<\/em>
\nhow nature is. Physics is concerned with what we can say about<\/em>
\nnature.<\/em>
\nBohr\u2019s preoccupation with the role of classical measuring
\napparatus could be seen as having encouraged such a positivistic-
\nsounding point of view. We have seen that in his later years he
\nbecame very concerned with philosophical issues, writing
\nextensively about them. The resulting corpus is hard to interpret.
\nBohr\u2019s gift in philosophical matters fell far short of his outstanding
\ntalent as a physicist. Moreover, he believed \u2013 and exempli\ufb01ed \u2013
\nthat there are two kinds of truth: a trivial kind, which could be
\narticulated clearly, and a profound kind which could only be
\nspoken about cloudily. Certainly the body of his writings has been
\nvery variously interpreted by the commentators. Some have felt
\nthat there was, in fact, a kind of quali\ufb01ed realism to which Bohr
\nwas an adherent.<\/p>\n

Does everybody else see the glaring almost-contradiction in what Bohr wrote? One cannot both deny that there is a quantum world and then go on to claim that we can’t say anything about it. That is my interpretation of his words, altho he was a bit better in the above quote. He technically only wrote that it is not the case that the task of fysics is to find out how nature is. Since he made some claims about how the world is (in his case, isn’t), apparently he either got his information from fysics even tho that’s not fysics’ task, or he got his information from somewhere else. This is not a contradiction, just odd.<\/p>\n

–<\/p>\n

Not particularly related to any passage in the book, but building on the general idea of the problem of how to reconcile the determinism of the macroscopic world with the indeterminism of the quantum world. After all, the macroscopic world is made of quantum world stuff. The current thinking is that the world is only approximately deterministic. I have a question: suppose that there is a level below quantum world stuff. Is it possible that this level is deterministic? That is, is it possible to have a deterministic layer and then an indeterministic layer on top of it? It seems not. But, it is definitely possible to have a deterministic layer and then a layer that is epistemically indeterministic on top of it.<\/p>\n

–<\/p>\n

I’m still not satisfied. I have not been convinced of antirealism in QM. Usually, the author talks about epistemic limitations, and then in some later passage talks about ontology, as if there were some connection, like the verificationism that Bradley criticized. I will read some more filosofical texts on the matter. Surely, if there is some way to make realism work, someone has thought of it.<\/p>\n

http:\/\/plato.stanford.edu\/search\/searcher.py?query=quantum<\/a> is where i must go.<\/p>\n","protected":false},"excerpt":{"rendered":"

Quantum Theory – A Very Short Introduction I have recently been in some discussions about the interpretation of quantum mechanics and the potential consequences of those interpretations. My chief opponent (we may call him) is a Copenhagen interpretation theorist. He has some rather odd views that are incoherent in themselves but apparently common among fysicists […]<\/p>\n","protected":false},"author":17,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[27],"tags":[],"class_list":["post-2908","post","type-post","status-publish","format-standard","hentry","category-epistemology","entry"],"_links":{"self":[{"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/posts\/2908","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/users\/17"}],"replies":[{"embeddable":true,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/comments?post=2908"}],"version-history":[{"count":5,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/posts\/2908\/revisions"}],"predecessor-version":[{"id":2921,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/posts\/2908\/revisions\/2921"}],"wp:attachment":[{"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/media?parent=2908"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/categories?post=2908"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/emilkirkegaard.dk\/en\/wp-json\/wp\/v2\/tags?post=2908"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}