Wednesday, November 23, 2011

Book review: "Impossibility" by John D. Barrow

Impossibility: The Limits of Science and the Science of Limits
John D. Barrow
Oxford University Press (1999)

In his book "Impossibility: The Limits of Science and the Science of Limits" John Barrow has carried together everything that sheds light on the tricky question what is possible, practically as well as conceptually. It is an extensive answer to the question of FQXi's 2009 essay contest "What is ultimately possible in physics?" but takes into account more than just physics. Barrow also covers economical, biological and, most importantly, mathematical aspects of the question what we can and can't do, what we can and can't know.

The book discusses paradoxa, timetravel, computabily, complexity and the multiverse, though Barrow never uses the word multiverse. The book was written somewhat more than a decade ago, but the summary of eternal inflation and bubble universes, varying constants and the question if it is still science to speculate about something that's unobservable is timely, and Lee Smolin's cosmological natural selection also makes an appearance. Barrow does mention some of his own work (on varying constants and universes with non-trivial topologies) but only in a paragraph or two.

Barrow briefly introduces most of the concepts he needs, but I suspect if you don't already have a rough idea what cosmology and quantum mechanics is about, some sections will not make a lot of sense. He mentions for example the many worlds interpretation in the passing without ever explaining what it is, and has the possibly shortest explanation of inflation and the expanding universe I've ever seen. But if you've read one or the other book that covers these topics you might (as I) be relieved Barrow keeps it short.

The presentation is very non-judgmental. Barrow essentially goes through all aspects of the issue and reports who has contributed what to the discussion, without imposing an opinion on the reader. He also gives an interesting historical perspective on how our view on these questions has changed esp. with Gödel's contributions. However, the writing reads more like a review than a book in that it lacks a narrative, and Barrow also doesn't offer own conclusions, he just summarizes others' arguments. I don't mind so very much about the lack of narrative since I have grown a little tired by the current pop sci fashion to make up a story around the facts so it sells better, but I'd have expected some original thoughts here or there. It is also unfortunate that the book is very superficial on some topics, for example time travel and free will, and if you know a little about that already you won't hear anything new. On the other hand, if you just want a flavor and some references for further reading, Barrow does a good job. I ceartainly learned about some aspects of the possible and impossible that I hadn't thought about before.

Barrow's book is well structured with a summary at the end of each chapter and a final summary in the last chapter. This is very convenient if you put the book down and only pick it up again a few months later and need a reminder what you've already read.

I've been reading for a while on this book. Since 2008 in fact, if I believe the receipt. The reason it took me so long has very little to do with the actual content of the book which, now that I managed to finish it I like very much, and more mundanely with the representation of that content. The book is printed in tiny and in addition the print is crappy, so I get tired just by opening it and looking at a page. It has a few illustrations that are very helpful and to the point, but not particularly inspired. There are also a few photos. As you can guess however, Hubble Deep Field in a crappy black and white print on some square inch isn't too compelling, and it's difficult to see the Château in Magritte's Château de Pyrénées.

Taken together, you may enjoy this book if you are interested in a summary of aspects of the possible and impossible, but you would be disappointed if you're looking for an in-depth treatment of any particular aspect. The book is well written, though not very inspired, and the scientific explanations are well referenced and, for all I can tell, flawless. I'd give four out of five stars if I had stars to give.

60 comments:

Giotis said...

Here is something:

Is it possible to enforce Nature to obey artificial laws designed by an intelligence if this intelligence is part of Nature and thus obeys her laws(e.g. human Kind)?

Bee said...

Fundamentally, I'd say no. But maybe the intelligence can design a fake nature on top of the real one and do its best to prevent you find out.

David Brown said...

If you google "outline of physics wiki" then you find that Wikipedia mentions 16 distinct branches of physics. Where might one locate a list of 15 to 20 books that give overviews of each of these 16 subjects at roughly the technical level of Barrow's book?

Bee said...

Hi David,

Gee, difficult question. The 16 topics outlined there are not a very useful classification when you're looking for literature. To begin with, I don't know since when 'Theoretical Physics' has become a 'branch of physics' that's apparently neither particle physics nor astrophysics nor thermodynamics.

The topics of Special and General Relativity and Quantum Mechanics, also particle physics, are well covered in a lot of books. Sean Carroll's recent book for example, Lisa Randall's first book, Lee Smolin's 1st and 3rd book, and Brian Greene's Elegant Universe do this very well, just to mention a few. These books however all only use them for the introduction. There are also many books specially dedicated to these topics, but I'd have to ask Stefan for recommendations. Is there anything specific that you are looking for? Best,

B.

Uncle Al said...

"Free will" as such is easily validated. Visit an insane asylum, a parliament, or a public toilet. There is no Plan.

Plato said...

Hi Bee,

Was just following up to see who John Barrow is.

I mean here in this case I get the sense that you may not only be troubled by the implications of the mathematical attributes that he may of brought to the science descriptions of reality but of a religious sense that may have been attributed to his thinking as well?

For the average lay person then, it's okay?

Best,

Plato said...

Interesting as well the following:

"According to our current on-line database, John Barrow has 25 students and 47 descendants." See: Mathematics Genealogy Project

His Advisor is also very interesting. A real interesting student line up of who's who.:)

Best,

DocG said...

You don't say anything, Bee, about the "impossibility" aspect of the "Impossibility" book. In my experience there are only two "impossibilities." The impossibility of Neils Bohr, who claims it's impossible to fathom the abyss opened in physics by the particle-wave duality. And Jacques Derrida, who claims it's impossible to fathom the abyss opened in semiotics by what he has named "deconstruction," aka "differance."

And when we register in our minds Bohr's striking conclusion that the real problem has to do with the way scientific evidence is represented, then we see a possible bridge between the two impossibilities.

Which leads me finally to my question: are you aware of the book by Plotnitsky, titled "Complementarity," in which he highlights the profound relation between the philosophy of Bohr and Derrida? (and if not, why not? :-))

(Naturally, as a physicist, you will claim that Derrida is not exactly your area of expertise. But then I will argue that, as a student of quantum physics, you have no choice but to sooner or later come to terms with his "impossibilities" in relation to those of Bohr.)

Uncle Al said...

http://mazepath.com/uncleal/truth2.htm

Jacques Derrida was paradigm slippage, a tumescent evanescence evincing semiotic pathogrammaticism. Jacques Derrida fomented proliferative obscuration in a linguistic dualism of double duplicate dopplegangsterism. Jacques Derrida was indistinguishable from a quacking duck.

Bee said...

Hi Doc,

No, sorry, I don't know the book. Complementarity I'm afraid means something entirely different to me. Barrow discusses to some extend that it might be impossible for us to understand what is possible, or to understand some secret of nature etc. This section of the book doesn't mention anything about the Singularity which I suppose would be the case were the book written today. Barrow basically just looks at all ways this can go: There's an infinite amount to learn, and we can only understand a finite amount. It's the other way 'round, or Nature's secrets just exactly fit into our brains (rspt whatever they may become). I don't know why people keep talking about the "particle-wave-duality." This is totally last century stuff and a linguistic problem entirely. One should just stop calling particles particles because, well, they're not particles. One of my prof suggested "Elementardinger" (elementary things) but admittedly it doesn't quite have a ring to it.

Best,

B.

Bee said...

Hi Plato,

I'm not troubled neither by the mathematical impossibilities (that might or might not have something to do with reality) nor by the religious interpretations that you can, if you insist, apply. Why sould I be troubled? Barrow discusses religion only very briefly when it comes to the omnipotence of god and what the laws of nature are actually laws about. Best,

B.

Plato said...

Bee:I'm not troubled neither by the mathematical impossibilities (that might or might not have something to do with reality)

Oh okay.

Inflationary Cosmology? That leads to a multi-verse?

Best,

Bee said...

Hi Plato,

Do you mean does the recursively persistent idea of the multiverse bother me? No, that doesn't bother me either. You see, I've tried to explain here why it is inevitable to have one or the other version of the multiverse, unless you find a way to formulate a description of reality by different means than solely mathematics. So if you find your theory predicts a multiverse, imho what you should be concluding is that the language you're using to describe nature has exhausted its usefulness there and you need to do more. In the absence of anything better than mathematics, you can deal with that shortcoming by just constraining yourself to that reality that matches with your observation. Which is what most of us do anyway. However, it might be that approaching the problems in today's theories from a different point of view (measures in the multiverse?) might indeed bring progress. (I don't believe that to be the case, but I don't expect everybody to share my believes.) Best,

B.

DocG said...

"I don't know why people keep talking about the "particle-wave-duality." This is totally last century stuff and a linguistic problem entirely."

Interesting. But this is very close to Bohr's view. Not quite, but close. (I'd use the word "semiotic" instead of "linguistic" myself.) But I'm curious as to why YOU would make such a claim. Can you point us to a post or a reference of some kind that explains the 21st century view?

DocG said...

By the way, I've been reading Brian Greene's book, and last night I viewed his Multiverse presentation on NOVA. Do you get PBS where you are, and did you see this travesty? I must say it disgusted me. What sort of lesson is this for young people, to encourage them to toss out all critical thinking and embrace what could only be called "New Age Physics." I nominate Greene for the "Billions and Billions" Carl Sagan award, for wide eyed willingness to accept the latest scientific fad as some sort of fantastic breakthrough. You are truly awesome, Brian.

Each and every physicist who accepts this view very clearly does so because it provides some semblance of "validation" to their own in-trouble theories. Yes, if we can believe another universe is born every time a quantum wave function collapses and that cosmic inflation (of reputation) produces infinite universes, then truly anything is possible. Which sounds nice enough but makes for terrible science. Long live Occam, sez I.

Christine said...

If one does not use the scientific method, then one is not doing science. Period.

The trend nowadays is to disagree with that statement. They say it is narrow-minded. Thing of the past. People routinely call theory what is obviously pure speculation. The sad part is, the younger generation can no longer distinguish these terms. Perhaps speculation is a word they don't even recognize by now.

I am not saying that to speculate is a bad thing. A speculation can evolve into a theory at some point. Or not, like perhaps 99.99% of them. A scientist must know by heart the difference between both terms. But, the fact is, many people no longer care, that is, if they ever did anyway.

And, remarkably, it seems, in these days, to be possible to build a whole 'scientific' career just with speculations.

Christine said...

Bee,

You seem to have broken yourself one of the greatest impossibilities of life: read books, papers, navigate the web and write complex blog posts, while with twin babies to take care of.

That is a great mystery for me. Are you sure you are not an alien? An android? Do not require sleep? I am speculating... :)

Best,

Christine

DocG said...

Please, Christine. If you get her thinking too much about how she does it, she might stop. Which would be a tragedy. I really like this blog.

Bee said...

Hi Christine,

There, you've blown my cover, I'm actually an alien, and on my planet the day has 31.4 hours :o) Best,

B.

PS: Oh, and the photos are photoshopped so you don't notice we all have 12 fingers and green skin.

Bee said...

Hi DocG,

You could take any modern textbook on quantum mechanics, the story goes like this. In the first days of quantum mechanics, physicists tried to make sense of what they saw by comparing it with the classical theories they were used to. Sometimes a photon acts like a particle, sometimes it acts like a wave. Thus the talk about the wave-particle duality. Today we know it's more precise to say a photon (or "elementary things" generally) are neither particles nor waves. They are described by a wavefunction. End of story. Best,

B.

Bee said...

Hi DocG,

Oh, and I don't watch TV, sorry. I don't think you can blame Brian Greene for that, it's all a question of demand and supply. Just look around in the blogosphere and see what topics attract most people. The Kosterlitz-Thouless transition? The non-linear sigma model? Gauge fixing of perturbatively quantized quantum gravity? Certainly not. What people like to discuss is everything vague enough so they feel like they are entitled to an opinion. The multiverse. Free will. Emergence. And so on.

B.

Christine said...

Bee,

I knew it! I knew it! :)

Best

Christine

Ps: babies will be walking soon, eh?

Bee said...

unless they break their neck before they can walk, yes.

Christine said...

Yeah, a tricky period, requires constant watching...

Best,

Christine

DocG said...

"They are described by a wavefunction. End of story."

But . . . but . . . but . . . the wave function collapses, no? And we are left with a particle, no? Which is what produces all those little dots, no? If it's just a wavefunction, then where do the dots come from? The stork?

By the way, I must admit that Greene's book makes more sense than his TV extravaganza. I still can't swallow the "multiverse" but at least in the book he does examine all the complexities and difficulties entailed in these strange hypotheses.

Bee said...

The wavefunction doesn't collapse, it decoheres. And after that, the elementary thing is still a wavefunction, just one that's to good precision in a position eigenstate.

DocG said...

"The wavefunction doesn't collapse, it decoheres."

Surely you're joking, Ms. Hossenfelder. :-)

In the immortal words of Richard Feynman: "Oy Vay!" But as an alien from outer space you might not understand the deep meaning of that expression.

Feynman was the one who warned his students to avoid any attempt at understanding quantum mechanics, because in doing so, they would "just go down the tubes." But modern physics has apparently survived the tubes and come up with "decoherence" as the answer to the quantum paradox? Sorry, but that does NOT compute.

The name of the book is "Impossibility" and that word is still what is on my mind, because in some sense it's the key to what ails us scientist-philosophers, in the 21st century, as it did in the 20th, seems to me. But what do I know? I'm a mere Earthling . . .

More presently.

Giotis said...

Christine, although I'm an engineer and not a physicist allow me to say that this obsession of yours with the "scientific method" reminds me of orthodox communists. They too want to analyse modern 21th century society and contemporary problems using the Marxist dogmas of 19th century. When you are dealing with Planck scale physics you must face the possibility that your theories might not have new directly observable predictions. If your theory though solves theoretical problems, is mathematical and physical consistent and explains elegantly and naturally a number of phenomena I don't see why we shouldn't call it a scientific one.

But this is not even the point, it's just a terminology issue. The problem is that what you implicitly propose, using as an excuse and alibi the scientific method, is that people should stop explore the unknown; I think such dangerous proposal is closer to religion than to science.

Bee said...

Hi DocG,

You're misunderstanding me. I didn't say decoherence "answers the quantum paradox." I said decoherence explains, why, after measurement, the elementary thing is to good precision in an eigenstate, yet still a wave-function. I did that to explain why you're mistaken believing that you need the classical particle concept in modern physics in reply to your earlier comment. Best,

B.

Phil Warnell said...

Hi Bee,

Its sounds like a worthwhile read, even if it does take a little time. I haven’t read this offering of Barrow’s myself, yet I have read one by him entitled “ PI in The Sky: Counting, Thinking & Being”, which I found to be excellent. One thing I liked about it was his frequent quoting of others to either introduce or expand on the subject matter and concepts, being a style which by having a quick look inside this one he continues to incorporate in this work. That is for me how can one not be impressed by a scientist who values the thoughts of others at least as much as those of their own; a quality I’ve found woefully absent in respect to many of his contemporaries. I was surprised however in you noting its lack of production values, as the one I read was wonderful in this department. Anyway now that you’ve pointed it out I’ll have to give it a look.

Best,

Phil

“between the ages of twenty and forty we are engaged in the process of discovering who we are, which involves learning the difference between accidental limitations which it is our duty to outgrow and the necessary limitations of our nature which we cannot trespass with impunity.”

-W.H. Auden as quoted by John D. Barrow, “Impossibity”, page 2

DocG said...

Thanks for the clarification, Bee. I'm relieved to learn that you do not subscribe to the notion that some sort of "pilot wave" or similar construct can explain away the fundamental paradox(es) of quantum theory.

Even if we can't agree on all the details I'm presuming then that you'll agree that at the very least there is a fundamental gap (or what I'd prefer to call an "abyss") at the heart of quantum mechanics, which not only appears to make an all embracing physical theory along traditional lines impossible, but poses a profound challenge to our deepest sense of what is both real and logical.

What I want to argue is that the discovery of this abyss, which Bohr called by the misleadingly innocuous name, "complementarity," is one of the greatest achievements of the human mind ever, making Bohr, in my opinion, not only one of the greatest physicists, but one of the greatest thinkers (i.e., philosophers) in the Western tradition.

Bohr's formulation (including not only complementarity but also other key ideas, such as the notion that quantum mechanics is "complete") is one of the most radical and challenging ideas ever proposed by any thinker and therefore it is 1. very often misunderstood and 2. all too often rejected as overly "dogmatic."

As I see it, the many attempts to somehow get around Bohr's
"abyss," via constructs such as pilot waves, many worlds, Schrodinger's cat, EPR, or even certain interpretations of decoherence, and not excluding string theory itself, have led physics very far astray, to the point that monstrosities such as the "multiverse" are now being seriously discussed. (More later -- hope you don't mind).

Christine said...

Giotis, Bee,

Eh, so now I am an obsessed, religious and dangerous person. Also a completely old-fashioned anti-scientific person using orthodox communist-like-something methods. Anything else? Be careful, Bee, you shouldn't allow people like me commenting on your blog.

What a monster I am.

Best

Christine

DocG said...

Giotis wrote: "If your theory though solves theoretical problems, is mathematical and physical consistent and explains elegantly and naturally a number of phenomena I don't see why we shouldn't call it a scientific one."

I agree. It isn't necessary as I see it that every theory need be testable (i.e., falsifiable) in order for it to be a meaningful contribution to science. As I see it, science is fundamentally an exploration rather than a quest for absolute factual truth.

What Christine may be objecting to, and certainly what I am objecting to, is not so much the untestability of such theories, but their flagrant violation of one of the fundamental principles of science: Occam's Razor.

It is the complete, out of control, multiplication of entities without end that for me, and perhaps also Christine, makes the Multiverse and similar "theories" untenable and unscientific.

Christine said...

There are important differences between theory, speculation, hypothesis, ideas, mathematics, mathematical physics, physics. Go back to your (old) books and study these terms. If you think you can blurr these terms at you will and still be doing science, then do so.

Giotis said...

Sure, maybe Witten should ask your permission to continue his research. I don't know is it scientific enough according to your strict scientific criteria? Or maybe it would be better if unorthodox scientists were interrogated by a scientific committee, something like the holy inquisition, to assure that no scientific dogmas are violated by their work. If they are found guilty they should be banished from the scientific community as charlatans.

Phil Warnell said...

Hi Christine,

Well if you ever form a scientific monster’s club you can count on me to join. Now I haven’t read Barrow’s book yet from the one I did I’m inclined to think he might sign up as well. That is Christine I too think physics has fallen off the rails, yet more so by attempting to skip steps in the process, as for instance failing in attempting to approach foundational issues with testability in mind as to then guide us respective of our speculations. That is for me it’s better to first consider as how to measure the head of the pin and the size of the angels before one runs off to proclaim how many can dance upon it.

Best,

Phil

Christine said...

Giotis,

Really, I do not see why you seem so angry at me. All I am saying, and yes, I keep on saying this, is that people should take care and be more precise in their terminology. Any scientist should observe that. That is all! I am certain that you have read at some point about the scientific method. When I say that nowadays many people decided to disregard the scientific method then I suddenly become a dangerous, dogmatic person, of the status of a judge from an inquisition-like commitee?

Come on, you can do better, no? Address your anger at something else.

If you ask my opinion on E. Witten, his best work is on mathematical physics, specifically, topological QFT. And no, he does not need to use the scientific method in order to e.g. "falsify an invariant", for me to approve his work.

Christine

Giotis said...

I'm not at all angry at you and don't get defensive.

It just bothers me that your posts have this pedantic character. You give the impression that you hold the absolute measure of scientific integrity and thus you are in a position to characterize people's hard work as unscientific. You are lecturing the subordinates with an attitude and that simply bothers me; nothing more...

Phil Warnell said...

Hi Giotis,

“I'm not at all angry at you and don't get defensive......... You give the impression that you hold the absolute measure of scientific integrity and thus you are in a position to characterize people's hard work as unscientific.”

Perhaps I need some instruction regarding the meaning of words, as yours sound pretty emotionally provocative to me. To be honest though I’m more prone to turn the other cheek, yet not if instructed I’m also not allowed to react in feeling the pain after being struck.

Best,

Phil

Christine said...

Giotis,

You are interpreting me completely wrong. Really, if my writing is that arrogant, then, whoa!!

In any case, you really know *nothing* about me at all. It is you who are making personal judgements, and there is nothing I can do about it.

Best

Christine

Bee said...

Hi Giotis,

In the hope to spread some peace, I see your point, but I believe you are reading Christine wrong. Cynical is more like it than arrogant. It is btw an interesting topic, we should have a post about this at some point. Best,

B.

Christine said...

Cynical? :(

Bee said...

Hi Christine,

Well, if nothing else, we all learn how difficult it is to understand each other by the written word only (esp since I figure English is not a native language to either of us three). In any case, you wrote for example "But, the fact is, many people no longer care, that is, if they ever did anyway." One of the first definitions of cynical that I find online is

a : contemptuously distrustful of human nature and motives

b : based on or reflecting a belief that human conduct is motivated primarily by self-interest

I thought it is at least partly appropriate to your comments. I didn't mean to be insulting if it came across like that, I'd call myself cynical too. Best,

B.

Phil Warnell said...
This comment has been removed by the author.
Phil Warnell said...

Hi Bee & Christine,

It’s been long clear to me that the first premise (axiom) of science, that is regardless of the rest of the details specific of the method is doubt, which is in effect cynicism. This therefore requires scientists to be professional cynics. Thus from what I’ve become to understand the maintenance of doubt above all else is the essential difference between garden variety and natural philosophy.


“To God, truly, the Giver and Architect of Forms, and it may be to the angels and higher intelligences, it belongs to have an affirmative knowledge of forms immediately, and from the first contemplation. But this assuredly is more than man can do, to whom it is granted only to proceed at first by negatives, and at last to end in affirmatives after exclusion has been exhausted.”

-Francis Bacon, “Novum Organum (New Instrument), 1620

“The first was never to accept anything for true which I did not clearly know to be such; that is to say, carefully to avoid precipitancy and prejudice, and to comprise nothing more in my judgement than what was presented to my mind so clearly and distinctly as to exclude all ground of doubt.” .”

-René Descartes, Discourse on The Method: of Rightly Conducting The Reason, and Seeking Truth in the Sciences (1637)

Best,

Phil

Giotis said...

I'm not sure how this end up to be a personal debate between me and Christine. Maybe it's my fault or maybe she is overreacting to criticism. Anyway my point is that people should feel free to explore new ground without being restricted by boundaries, dogmas and definitions of what is science and what is not. It may happen that their theory (due to the very nature of the questions is trying to answer and its regime of applicability) may not have detectable experimental signatures; this doesn't mean that their work is not scientific or that it should not be taken seriously. Ultimately it will be evaluated by the scientific community, there can't be no other way. Allow us non experts to have an opinion too though:-)

Christine said...

Ideas, speculations, hypotheses, although having different meanings themselves, are what they are, namely, are not theories. In order to construct a theory, it must be sufficiently developed to be subject to the scientific method. It does not mean it must litterally pass through all steps, although that is what is ultimately aimed. At least, a theory must be in principle subject to the scientific method. Otherwise it cannot be called a theory. It could be an idea, a speculation, an hypothesis, whatever, but not a theory.

That is not an unimportant discussion on semantics. Exactly because the scientific endeavor is so difficult and must be as much independent from our own prejudices and passions, is the reason we should rely on a self-regulating method.

Hope this clarfies my point of view. But what I have been claiming is nothing new, it is quite well established, which Sabine and Stefan, the owner of this excellent blog, know very well, as they are professional scientists. Sabine works in phenomenology of quantum gravity, I am certain she knows these differences. But I cannot speak for them of course.

The discussions here just corroborate, at least to me, that this subject is confusing. I could be in error on all I have said, and the way I have said. It doesn't matter.

What I don't understand is the need for acusations and ad hominen attacks. As I do not tolerate such things, I finish here, nothing more to add.

Best

Christine

Phil Warnell said...

Hi Goitis,

You said : “Ultimately it will be evaluated by the scientific community”

What I find Christine to be pointing out is contrary to your understanding, as it will rather be ultimately decided by the theory being found consistent with nature as evaluated by the scientific method; that is scientists don’t decide on the rules of nature, rather they discover them. This has their theories required to satisfy nature and not the other way around. That is to say I’m completely sympathetic with Christine’s view on the matter as it could be further argued that the abandonment of this basic principle of science lies at the heart of the current discourse which some saw much earlier as an imposing danger regarding the future utility of the philosophy more generally.


"You are the only person with whom I am actually willing to come to terms. Almost all the other fellows do not look from the facts to the theory but from the theory to the facts; they cannot extricate themselves from a once accepted conceptual net, but only flop about in it in a grotesque way."


-Albert Einstein, (in a letter to Erwin Schrödinger) 1938

Best,

Phil

DocG said...

To continue from where I left off (and to apologize to those who have apparently not yet been offended by anything I've written :-) ), I want to make some points regarding the radicality of Bohr's position and clear up some misunderstandings. And if I am the one who has misunderstood, then I hope to be corrected.

First of all, the radicality is so extreme that it could also be called "impossibility." In other words, Bohr's interpretation of quantum mechanics is, very literally, impossible. Which is no doubt why so many have felt the urge to "get beyond" it. But there is a good reason why it is impossible, which I'll get to eventually, assuming I am permitted to continue.

Secondly, as I it seems to me, and with apologies to Bee, Bohr's wave-particle duality is apparently unaffected by decoherence, or any other interpretation that involves a wave function only, however narrow it is presumed to get.

As to why that might be, first I will quote from a 2005 paper on this topic, "Decoherence, the measurement problem, and interpretations of quantum mechanics" (http://arxiv.org/PS_cache/quant-ph/pdf/0312/0312059v4.pdf):
"within the standard interpretation
of quantum mechanics, decoherence cannot solve the problem of definite outcomes in quantum measurement: We are still left with a multitude of . . . components of the wave function, and we need to supplement or otherwise to interpret this situation in order to explain why and how single outcomes are perceived." (p. 37)

More fundamental, as it seems to me, is Bohr's emphasis on the need to employ classical concepts and traditional language when describing quantum effects. This in itself is a big part of the radical nature of Bohr's intellectual revolution. So when he refers to a "wave" or a "particle" he is NOT claiming that there actually is some wave or particle that was observed, because the actual situation is, in his interpretation, literally indescribable. He is using the language of classical physics when he employs such terminology, because this takes us as close as possible to an understanding of what is going on.

Thus when physicists claim that decoherence can now be substituted for "the collapse of the wave function" they are thereby claiming that the quantum paradoxes don't really exist and that they can somehow be explained away purely in classical terms.
(more later)

DocG said...

Sorry, but I need to explain my meaning a little more clearly. "The collapse of the wave function" is also not to be taken literally. For Bohr, there is nothing that actually collapses, and this phrase is simply an attempt to use classical language to provide a sense of how certain experimental outcomes are to be understood. So if "decoherence" is to be understood as an improvement, it can be an improvement only if the collapse is to be taken literally, which of course would be completely contraty to Bohr's approach (or should I say, his "strategy").

Phil Warnell said...

Hi DocG,

Decohernce is an action first given attention to by David Bohm in his 1952 paper, although not labelled as such. However here too it is not taken as being the solution to the measurement problem yet rather the ontological nature of the pilotwave theory itself serving as being such. Further this theory also cannot be painted as a classical one and yet it serves as a direct counter example as to having an explanation for the quanta as J.S. Bell so ably put it “To show that vagueness, subjectivity, and indeterminism are not forced upon us by experimental facts, but by deliberate theoretical choice?"

Best,

Phil

DocG said...

Hi Phil,

Yes, I was originally fascinated by Bohm's "Implicate Order" book, but soon became puzzled, as his theory seemed much more far fetched than what it was intended to replace. As with so many other such attempts, the arduous efforts to "square the circle," so to speak, wind up violating Occam's Razor many times over.

Bell is expressing an indignation shared by a great many, including Einstein himself, and this is understandable, because as I've said, Bohr's formulation is not only radical, but literally impossible. But it is NOT either vague nor subjective. And its indeterminacy is very precisely determined.

What Bohr and his colleagues discovered was not simply a paradox (i.e., a contradiction) but something much stronger, an aporia, which is, literally an "impasse," so maybe it would be more appropriate to characterize his formulation as "impassible." Which can be understood as a barrier beyond which it is "impossible" to go.

Which is why he always claimed that quantum mechanics was "complete." Or, to be more accurate, the incompleteness of quantum mechanics (the gap or abyss) was definitive, and thus, despite this incompleteness, nevertheless complete.

For me this is a watershed of modern thought, because what is implied in such a formulation is that reality itself is ultimately grounded by an aporia, i.e., a self contradictory abyss, which must be accepted as axiomatic. (more later, unless Bee kicks me out)

Bee said...

Hi DocG,

Yes, I know the paper you are referring to. Look, I'm not a historian, so I don't know what Bohr might or might not have meant with particle-wave duality. The way it's commonly used it is supposed to mean the elementary thing is both a particle and a wave. What I am telling you is it's neither a particle nor a wave. It is true that decoherence does not bring the state into an actual eigenstate, but it explains why you measure one to arbitrarily good precision, so who really cares. Either way, if you believe decoherence or not, after measurement the 'quantum thing' is not something different than it was before measurement, it's just in a different state.

And yes, I am in fact saying that "quantum paradoxa" don't exist. Indeed, what makes paradoxa paradox is that they can't exist, so if you believe there is any quantum paradox you've gotten something wrong. I never said that something that can't exist 'can somehow be explained away in purely classical terms.' Best,

B.

DocG said...

Hi Bee,

"And yes, I am in fact saying that "quantum paradoxa" don't exist. Indeed, what makes paradoxa paradox is that they can't exist, so if you believe there is any quantum paradox you've gotten something wrong."

Well, this is the crux of the matter, certainly. And what you say makes perfect sense. What Bohr says does NOT make sense, admittedly. But this is an important part of what the Copenhagen interpretation (or at least his version of it) is all about.

You cannot ever "make sense" of quantum mechanics and if you try you will, in the words of Feynman, "go down the drain." (Which imo is what has now happened to so many physicists working so hard to square that circle.) We are talking about "Impossibility" here, remember?

You are writing like a sensible physicist and there is nothing wrong with that -- up to a point. Sure it really doesn't matter what you call it, "decoherence," "collapse of the wave function," etc., or whether it is strictly "kosher" according to Bohr, Bohm or anyone else, so long as you can use it as a tool (intellectual or otherwise) to obtain and interpret evidence.

Physicists tend to have a healthy disdain for "metaphysics" and historically there are good reasons for that. But what we learn from Bohr is that at a certain point, "metaphysics" (or maybe better "anti-metaphysics") has to enter the picture, whether we like it or not.

Actually, Bohr formulated his explanation in such a way as to minimize the metaphysical aspects, by concentrating only on what can be "observed," i.e., "measured." But there is no getting around the fact that "complementarity" is a metaphysical notion, since it is foundational, not only to physics but to our whole idea of what constitutes the "real world." And if he is right, the world we know and love is rooted in a fundamental paradox (or better: aporia).

The lesson for physics, as I see it, is that physicists must take Bohr's formulation very seriously despite its seemingly illogical basis, because the "impossibilities" he reveals are in fact the result of an extremely logical analysis that imo is absolutely irrefutable. What makes it so powerful, is that it is based not only on thought, as with literally all other "metaphysical" formulations, but also on the results of very precisely executed experiments, not only his, but those of a great many successors up to the present day. (more later)

Bee said...

Hi DocG,

I'm not sure how long you've followed this blog, so just to make that clear I have a great sympathy for those who rethink the foundations of quantum mechanics, so don't misinterpret me. All I'm saying is there is nothing wrong and nothing paradoxical with quantum mechanics as it is, and you don't need any metaphysics either. It is just to some extend unsatisfactory as it is. For me, one of the main reasons why rethinking quantum mechanics might be a useful thing to do is that the reason why we haven't succeeded in quantizing gravity might lay there. Now people differ in how relevant they regard these reasons. With regards to Bohr, maybe this it is interesting for you. There is more than one consistent logical system. Best,

B.

Plato said...

Bee:So if you find your theory predicts a multiverse, imho what you should be concluding is that the language you're using to describe nature has exhausted its usefulness there and you need to do more.

I believe Bee that what has happened natural within the mathematical description process is that they did find a new anomaly to describe something that did not exist in the evolutionary description in the expression of inflation.

I still understand your point about the question of reality ad your place amongst your peers with respect of this view and there is nothing wrong with that, in that it is necessary for them to believe or otherwise.

In the same vein, we cannot discredit the process unfolding when one learns that the mathematical description further evolves the discussion. This is how it may appear to some yet if the do not see this mathematical background then it would not be apparent to them?

I have seen you deal responsibly with these questions and your link to you previous discussion for clarity speaks volume. Those kinds of link are neuron expansion within the scope of the brain/blog of BEE ad Stefan within the confines of a recursive thought expression as one moves forward? Qui /Non?


Best,

Plato said...

Hi Bee,

QFT as it has been explained for me through the readings of Clifford and Matt who have aided in the understanding of what has been meant by "particle expression." This has helped greatly. At the same time, it requires much work for me to see and think in this way.

While dealing with theoretical framework the process turns one back too, the description not only of the theoretical development process but of the relationship of how one may see the expression of local regions within the cosmos? Looks at WMAP is developed here?

In this same respect mathematically it must be understood "how dimensional expression" is seen so that it blends with the understanding you have in the relationship to that mathematical evolution in your dealing with the mathematical frameworks? You still are unsure here?

Matt is helping with those clean lines too, yet it must be understood why such evolution is there for understanding this relationship with geometry and nature as a facet of the expressions in the evolution of our universe you see?

Best

Plato said...

Hi Bee,

One last thing here.

Experimental physicists working at the LHC, such as Professor Nash, say the results are forcing their theoretical colleagues to think again.

"For the last 20 years or so, theorists have been a step ahead in that they've had ideas and said 'now you need to go and look for it'.

"Now we've done that, and they need to go scratch their heads," he said.

That is not to say that it is all over for supersymmetry. There are many other, albeit more complex, versions of the theory that have not been ruled out by the LHC results.
See: LHC results put supersymmetry theory 'on the spot'

In order to look ahead you need framework, and then they come along and in phenomenological approach say, "ah you better think again?"

One does not deny the ability of outcome to be generated responsibly within framework that is consistent, yet, quite natural needed is experimentally proof that it is wrong. That process needs to take place and I understand you know this.

Theoretical frame work is forward looking? While believing it to be true, universe was found to be actually speeding up? What "is real" you see?

Best,

DocG said...

"With regards to Bohr, maybe this it is interesting for you."

Surely you're joking, Ms. Hossenfelder. Or maybe this is a test? Which I of course must fail. Since I can understand only about 10% of what is written in this article. So I'm forced to admit, I am neither a physicist nor a mathematician nor a logician.

But I do fancy myself as a philosopher, and something of a historian of science as well, since I've kept up with a lot of the popular and biographical literature, especially on quantum physics, which fascinates me.

As far as "quantum logic" is concerned, it would work for me (assuming I could understand it) as a sort of operational logic which might enable one to construct an algorithm for evaluating certain experimental results.

But I must always fall back on Bohr's view that as far as deeper foundational issues are concerned, there can be no special quantum "logic," fundamentally different from the logic of ordinary language, and that whatever can be said about quantum mechanics must be expressed using the logic scientists have traditionally made use of many years prior to the discovery of the quanta.

This for me is in itself a radical idea and not at all what one might expect. And it suits the quantum to a tee, because each side of the quantum paradox (which I must insist on) can in fact be expressed in ordinary language. It's only when we try to express the quantum world in its totality that we find ourselves at a loss.

Which leads again to another of Bohr's radical breakthroughs, his insistence that, in fact, there IS no "quantum world." Incredible. But also profound.

But also a great barrier, it seems, for anyone desiring to do research on the nature of this nonexistent but nevertheless compelling "world." Such as yourself.

"For me, one of the main reasons why rethinking quantum mechanics might be a useful thing to do is that the reason why we haven't succeeded in quantizing gravity might lay there."

As I see it the reason for this failure has to do with the problem that if there is no quantum world then there may be no such thing as quantum gravity either. Nor such a thing as a "theory of everything." Not that I want to belittle the research you are doing which is imo extremely important and also extremely interesting (to the extent that I am capable of understanding it).

(more later)

DocG said...

I find it very interesting that so many of the later approaches to both particle physics and cosmology, and especially the attempts to create a "theory of everything" can be seen as efforts to get around the fundamental abyss opened up by the Copenhagen interpretation.

Thus the "many worlds" approach attempts to explain away the measurement problem by proposing that every measurement instantly trigger two new universes. Or Bohm's "implicate order," which posits a pilot wave as a means of getting around the "wave-particle duality."

Even "decoherence" theory, as initially developed by Bohm (as Phil has pointed out), looks very much like something along similar lines, a clever attempt to bridge the unbridgeable gap, the "gateless gate" posed by Zen master Bohr.

Especially amusing is string theory, which looks like a crude attempt to somehow finesse the problem by fusing both particle and wave into a single elementary particle: a vibrating string.

The latest development of this kind is "quantum gravity," which, in a similar spirit, hopes to combine quantum theory and general relativity. As I see it, this is essentially a variation on the same old theme, since basically what is being attempted is the fusion of quantum discontinuity with the manifold continuities of the gravitational field, i.e., particle-wave all over again.

In the many attempts to get around the fundamental gap separating the world of the continuous with that of the discontinuous one can't help but be reminded of Zeno's paradoxes or the many futile efforts on the part of so many mathematicians of the past to square the circle.

Not that such efforts are entirely futile. After all, if it were not for all the many futile attempts to overcome such paradoxes we might never have had the calculus.

What so many contemporary physicists are now attempting along all such lines is undoubtedly producing much that is of real significance and I'm not suggesting that such efforts should be discontinued, so long as they prove fruitful on at least some levels. But I do think it's high time that our physicists and philosophers of science finally acknowledge that Bohr may have had something real up his magician's sleeve after all and was not, as so many prefer to believe, simply performing a cheap parlour trick.