Does Quantum Mechanics Describe a Paradoxical Reality?

[chippy_pensoi]

Hello. New here: Sorry if this has been asked before, but can someone who understands physics please clear up my understanding of the implications of quantum mechanics. Which of the following four statements is false, if any, and why?

 

1. The behaviour of quantum systems is elegantly described by Schrödinger’s equation, which describes a wave (or wave ‘function’ – not quite sure of the difference).

2. When measured (e.g. in the famous double-slit experiment) quantum systems display or ‘collapse’ into particle-like behaviour.

3. It would seem that quantum systems exist in some kind of state that the mind simply cannot picture; in the same way it can picture, say, a duck. The inability of the mind to grasp wave-particle duality is the same as its inability to grasp the meaning of the duck and rabbit of the famous image at the same time…

…all it can do is oscillate between the two interpretations, or blankly witness the image as it is without interpretation.

4. The famous thought experiment suggested by schrodinger is an attempt to illustrate the mind-boggling strangeness of the consequences of all this – that, until consciousness exists, reality can be, at the same time, one thing and its opposite: a paradox.

I have been reading David Chalmers, who elegantly summarises the state of philosophical theorising about Quantum Mechanics. All avenues seem to lead either to extremely weak theories (e.g. that microscopic systems magically and arbitrarily change when they reach a certain size), or extremely bizarre ones (that the entire universe existed in a non-discrete superposed state until consciousness existed to collapse it into discreteness). Could it be that reality is paradoxical; meaning that reality is, essentially, impossible to grasp in the mind, only measure?

I hope I have made myself clear, and hope someone with a background in quantum physics is patient enough to help me.

Thanks

Edited December 20, 2014 by chippy_pensoi

[ajb]

Could it be that reality is paradoxical; meaning that reality is, essentially, impossible to grasp in the mind, only measure?

You are really asking quite philosophical questions. I, and I think a lot of physicists will take a more pragmatic view point. We model nature using mathematics and in quantum mechanics one way of doing that is using the Schrödinger equation. However, you have to compare it to reality and this is done by measurements in the lab. If the mathematical framework allows you to calculate things and predict phenomena that then agree well with the experiments then we have a 'good theory' and we are all happy.

 

My ethos is that 'the only things that are real are those that you can measure'.

[AndresKiani]

Do philosophers every make any positive contributions in science? I've thought about this, and I figure that philosophers usually don't ask many worthwhile or even relevant questions that which are any use in science.

 

What is your thought on that ajb.

[ajb]

Do philosophers every make any positive contributions in science? I've thought about this, and I figure that philosophers usually don't ask many worthwhile or even relevant questions that which are any use in science.

 

What is your thought on that ajb.

They tend not to ask questions that can be really answered. This is the problem with interpretations in quantum mechanics.

 

However, if a philosopher asks a question or develops some interpretation that can inspire new questions in physics then it is great. The 'right interpretation' is the one that allows you to further develop the theory.

[chippy_pensoi]

Thanks for the replies. I am not asking these questions as a scientist in order to further scientific understanding, but as an ordinary person trying to understand what is going on in Deep Science, and then what implications it might have for life outside the sciences. So, may I ask, is my understanding of points 1, 2 and 3 correct, at least, before we get into the philosophical implications?

Edited December 21, 2014 by chippy_pensoi

[Strange]

 

1. The behaviour of quantum systems is elegantly described by Schrödinger’s equation, which describes a wave (or wave ‘function’ – not quite sure of the difference).

2. When measured (e.g. in the famous double-slit experiment) quantum systems display or ‘collapse’ into particle-like behaviour.

 

I don't think this is a very accurate description. All particles (always) have both wave and particle characteristics. It depends what you measure.

 

The famous thought experiment suggested by schrodinger is an attempt to illustrate the mind-boggling strangeness of the consequences of all this – that, until consciousness exists, reality can be, at the same time, one thing and its opposite: a paradox.

 

And it is not generally agreed that consciousness is required for this. An "observation" is really just any interaction.

 

I don't know anything about David Chalmers, but it doesn't appear that he would be a good person to get an understanding of quantum theory from. I would recommend someone like Feynman.

And in answer to the question in the title: no.

[swansont]

 

3. It would seem that quantum systems exist in some kind of state that the mind simply cannot picture; i

 

 

I think there are a number of scientists who would disagree. QM seems paradoxical, probably because we want to impose the structure of the macroscopic world onto what we observe. But when you have learned how the quantum world behaves, the apparent paradoxes go away.

[chippy_pensoi]

 

And in answer to the question in the title: no.

 

Okay, but could you help me understand this? A lot of descriptions I have read of QM suggest that what the measurements must refer to is an extremely bizarre (I am suggesting ‘paradoxical’) state in which quantum systems are simultaneously exhibiting two contradictory states which ‘collapse’ into one or the other upon measurement. Is this not so, and if not, can you explain the error, because if it is an error, a lot of pop-science expositions of QM seem to be sharing it!

[swansont]

 

 

Okay, but could you help me understand this? A lot of descriptions I have read of QM suggest that what the measurements must refer to is an extremely bizarre (I am suggesting ‘paradoxical’) state in which quantum systems are simultaneously exhibiting two contradictory states which ‘collapse’ into one or the other upon measurement. Is this not so, and if not, can you explain the error, because if it is an error, a lot of pop-science expositions of QM seem to be sharing it!

 

 

It's not a paradox in QM. It's known as a quantum superposition. It's only "bizarre" when viewed from the classical perspective.

[Strange]

Okay, but could you help me understand this? A lot of descriptions I have read of QM suggest that what the measurements must refer to is an extremely bizarre (I am suggesting ‘paradoxical’) state in which quantum systems are simultaneously exhibiting two contradictory states which ‘collapse’ into one or the other upon measurement. Is this not so, and if not, can you explain the error, because if it is an error, a lot of pop-science expositions of QM seem to be sharing it!

 

This is not paradoxical, it is just counter-intuitive. The things we encounter in everyday life (and that our brains have evolved to understand) do not behave like this. There is no reason that the quantum world must behave as our intuitions expect. And it doesn't. But it is a completely rational, logical theory able to make extremely precise theories. As result we have technologies such as your computer/phone that allow this conversation to take place.

 

But there is a problem that a lot of popular science writing likes to play up the amazing/paradoxical/impossible mature of things.

 

Note that there a lot of things called "paradoxes" in science (e.g. the Twins Paradox in relativity) but these are not paradoxes in the classiccal sense (self contradictory). They are all things that appear contradictory until the explanation is understood.

[chippy_pensoi]

 

I think there are a number of scientists who would disagree.

 

Those few who think about it – if ajb is correct.

 

 

QM seems paradoxical, probably because we want to impose the structure of the macroscopic world onto what we observe. But when you have learned how the quantum world behaves, the apparent paradoxes go away.

 

Fine. But can you, or anyone else, help me to understand this?

 

This is not paradoxical, it is just counter-intuitive. The things we encounter in everyday life (and that our brains have evolved to understand) do not behave like this. There is no reason that the quantum world must behave as our intuitions expect. And it doesn't.

 

But I’m not talking about behaviour, or measurements, I’m talking about what the thing must be that is being measured / exhibiting behaviour. When the mind tries to picture it – well, it can’t, in the same way it cannot picture both ‘meanings’ of the duck-rabbit image above. This is what I mean by ‘paradox’ – unavailable to normal picturing.

[Strange]

But I’m not talking about behaviour, or measurements, I’m talking about what the thing must be that is being measured / exhibiting behaviour. When the mind tries to picture it – well, it can’t, in the same way it cannot picture both ‘meanings’ of the duck-rabbit image above.

 

That is exactly what I mean by counter-intuitive. You ask, what is the "thing" What is an electron? It is an electron. What is a photon? It is a photon. Ultimately, as with all science, they are models that work.

 

The question makes no sense. What would you expect the answer to be? "It is a little machine made of wood and brass"? I'm not being sarcastic, just pointing out that the question has no answer other than, it is what we measure it to be.

 

This is what I mean by ‘paradox’ – unavailable to normal picturing.

 

That is not the meaning of "paradox". (It is rarely a good idea to use your own personal redefinitions of words.)

 

However, if there is a word that means that, then I would agree it describes quantum theory.

Edited December 21, 2014 by Strange

[Eise]

Could it be that reality is paradoxical; meaning that reality is, essentially, impossible to grasp in the mind, only measure?

You are asking two different things here:

 

1. Is reality paradoxical?

2. Is our understanding of reality paradoxical?

 

On 1 I would say no. There is no way that a thing or state of affairs can be the case and not be the case.

 

On 2 I would say 'depends': the mathematical formalism of QM is rigid and consistent. As physicists work with QM, and technology is based on QM, reality is not ungraspable. However, if the question is if we can grasp quantum reality using classical concepts, the answer is clearly 'no'. In our daily life we only understand reality with classical concepts, and in this sense QM is paradoxical. But only in this sense.

This is what I mean by ‘paradox’ – unavailable to normal picturing.

 

Exactly. If you translate 'normal' with 'with classical concepts'.

[chippy_pensoi]

 

That is exactly what I mean by counter-intuitive. You ask, what is the "thing" What is an electron? It is an electron. What is a photon? It is a photon. Ultimately, as with all science, they are models that work.

 

The question makes no sense. What would you expect the answer to be? "It is a little machine made of wood and brass"? I'm not being sarcastic, just pointing out that the question has no answer other than, it is what we measure it to be.

 

Okay. Let’s say we are astronauts exploring a new world. This world is totally inhospitable, with a poisonous and also completely opaque atmosphere, too gloomy to see. We therefore have to wear suits that are fitted with various instruments that read the environment. You and I are walking through an area of this world and we come across something. Our instruments tell us that it is moving, that it is carbon-based, that it seems to ingesting part of the environment, that it is about 10kg and as large as a dog, and so on. We conclude that it is some kind of ‘animal’ – and are we not justified in reaching such a conclusion? Even of attempting to ‘picture’ what the thing really is (‘behind’ the measurements, so to speak)

 

Now let’s say that we move on and come across another thing on this world. We ‘read’ it, but this time my instruments tell me it is stationary, silicon-based, weights about 100okg, is as large as a house and your instruments tell you that it is moving extremely quickly, that it is about 10 grammes and the size of an oak leaf. Now, assuming that our instruments are completely accurate (in this future machines never break down), are we not still justified in trying picture what we have come across…? and are we not justified in assuming that we cannot? We can measure it, predict its movements, meaningfully speak about our readings and so on, but we cannot picture it.

 

 

 

That is not the meaning of "paradox". (It is rarely a good idea to use your own personal redefinitions of words.)

 

The meaning of paradox, originally, is ‘distinct from opinion’, one of many ordinary meanings that it still retains (it is rarely a good idea to exclusively rely on specialised technical definitions of words in ordinary discourse).

You are asking two different things here:

 

1. Is reality paradoxical?

2. Is our understanding of reality paradoxical?

 

On 1 I would say no. There is no way that a thing or state of affairs can be the case and not be the case.

 

Why not? Is this not precisely what our readings of quantum mechanics tell us, or if not ‘the case and not the case’ at least ‘one case and simultaneously another completely different case’.

Edited December 21, 2014 by chippy_pensoi

[swansont]

Fine. But can you, or anyone else, help me to understand this?

 

Possibly. But it takes physics students a while to understand this, and that comes with delving into the details of the theory. Learning about the science is not the same as learning the science itself.

[Strange]

The meaning of paradox, originally, is ‘distinct from opinion’, one of many ordinary meanings that it still retains

 

Correct. But you said, "This is what I mean by ‘paradox’ – unavailable to normal picturing" which is not, and never has been, the meaning. (I actually went and checked the etymology to see if it has anything to do with "picturing"; it doesn't.)

 

But what it originally meant is irrelevant; that is known as "the etymological fallacy".

 

(I'm afraid I don't understand the point of you astronaut analogy, so can't really comment on it.)

[ajb]

There are no paradoxes in quantum mechanics that I am aware of. Quantum mechanics has shown to be a good description of the microscopic world time and time again. Even the strange and unexpected predictions seem to be be realised.

[chippy_pensoi]

 

Possibly. But it takes physics students a while to understand this, and that comes with delving into the details of the theory. Learning about the science is not the same as learning the science itself.

 

Einstein once said if you can’t explain something simply, you don’t understand it. This is true for every field of enquiry I do understand well, so, assuming you agree (which you might not) and assuming you do understand QM, can you explain to me, simply, which of my four points is incorrect, and how? No problem if not, of course, but that is what I am asking for here, not a five year graduate course.

[ajb]

Einstein once said if you can’t explain something simply, you don’t understand it.

Well, not everything is simple, and even then simple is a relative term.

 

With quantum mechanics you agree that particles and waves are really the two extremes of classical physics and that quantum mechanics means that you have to start to think somewhere in between; no one in physics thinks of a particle simply as a tiny ball. If you use the Schrödinger picture and wave mechanics then you should be thinking in terms of waves but realise that if you ask a 'particle question' then you get a 'particle answer'. If you ask a 'wave question' you get a 'wave answer'.

 

But there is no paradox here, the formalism of quantum mechanics allows for this duality of waves and particles.

Edited December 21, 2014 by ajb

[chippy_pensoi]

 

Correct. But you said, "This is what I mean by ‘paradox’ – unavailable to normal picturing" which is not, and never has been, the meaning.

 

It is the meaning, or close enough to be intelligible. A paradox is something which combines opposites, or contradictions in a way that reasoning, opinion or mental-imaging cannot grasp. I am not appealing to etymology, but to an ordinary person’s ability to understand language – with some flexibility. At anyrate…

 

…the astronaut analogy is an attempt to express a contradictory reality that two sets of measuring instruments identify as non-contradictory or, as you say ‘what we measure it to be’. I am asking about the reality that the measurements are of. This might be meaningless to a physicist in his lab, but it is the root of my endeavours (and many other non-scientists interested in QM) and I am looking for clarification of the trunk and branches, if you will.

[Strange]

I am asking about the reality that the measurements are of.

 

Then this is philosophy rather than science. You might want to read some of the interpretations of quantum mechanics and see if any appeal to you: http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics(you can pick whichever one appeals because they are just different descriptions of the same theory).

[ajb]

It is the meaning, or close enough to be intelligible. A paradox is something which combines opposites, or contradictions in a way that reasoning, opinion or mental-imaging cannot grasp.

I would try to make that a tighter definition suitable for this discussion. I would mean by a paradox something like 'two statements that cannot be true at the same time shown to be true at the same time'. There is some internal inconsistency with the system you are describing.

 

Quantum mechanics seems to have this paradox with 'wave particle duality', but within the mathematical framework no such paradox really occurs. It comes from trying to insist that the two classical and distinct notions of particles and waves is completely sufficient in physics.

[chippy_pensoi]

With quantum mechanics you agree that particles and waves are really the two extremes of classical physics and that quantum mechanics means that you have to start to think somewhere in between;

 

Could you have a go at thinking about my duck-rabbit analogy? The point here is that, with the optical illusion I quoted, there is only the illusion of ‘somewhere in between’. Really there is no way whatsoever to hold, in your mind, the two interpretations at once. If you see what I mean, could you explain how QM really is ‘somewhere in between’ and not the paradox of the duck-rabbit image?

 

But there is no paradox here, the formalism of quantum mechanics allows for this duality of waves and particles.

 

So many scientists tell me, but without explaining why. I understand that I can never understand it deeply or fully without studying Physics for years, but I also know it is possible to understand this well enough to work out if my basic idea is right or wrong and, without going in depth, why: in the same way I can understand enough of Godel’s theorum, Kant’s philosophy or Darwin’s theory without having studied them for years.

[swansont]

 

Einstein once said if you can’t explain something simply, you don’t understand it. This is true for every field of enquiry I do understand well, so, assuming you agree (which you might not) and assuming you do understand QM, can you explain to me, simply, which of my four points is incorrect, and how? No problem if not, of course, but that is what I am asking for here, not a five year graduate course.

 

Everything has wave properties. This mostly noticed on the scale of the very small, because otherwise the wave properties are smaller than the object. As ajb has said, a particle is not actually a tiny ball. But when we measure, it has properties that take on definite values, such as energy and position, that we associate with particles.

[chippy_pensoi]

 

Then this is philosophy rather than science.

 

Okay, yes it is, if that’s what you want to call it. But I am asking for is understanding of the science part.

 

Quantum mechanics seems to have this paradox with 'wave particle duality'

 

 

Okay good, so as I am (yes, perhaps clumsily) defining paradox (slightly elastic, but consistent with ordinary usage) whatever reality QM points to is paradoxical, in the same sense as the duck-rabbit reality: it cannot be ‘held’ in the mind, at once.