Why is Quantum thoery so confusing that no body actually understand it ?

[Jimmy Snyder]

Orbits of planets, that if you drop an apple it falls to the ground, that a current through a wire will produce a magnetic field, that a gas cools when it expands, time dilation, the expansion of the universe, ... We could probably fill a book just with the examples.

Orbits of planets - classical mechanics gets the wrong orbits. The case of the planet Mercury around the sun is a famous example.

That if you drop an apple it falls to the ground - classical mechanics gives the wrong trajectory.

That a current through a wire will produce a magnetic field - it gets it wrong for the current associated with the orbit of an electron in an atom, qualitatively as well as quantitatively.

that a gas cools when it expands - gets the wrong equation because the rate of expansion is frame dependent.

time dilation - no, it failed to predict that.

the expansion of the universe - no, it failed to predict that.

We could probably fill a book just with the examples. - that's my point. There was a time when they did fill books with the examples because the predictions were "stunningly correct".

 

[IcedEcliptic]

Well, it would seem GeorgCantor's diversion worked relatively well. Meanwhile, I still note "ape-like intuition" and have a hearty chuckle. How have we come to this given the OP?

 

[GeorgCantor]

Well, it would seem GeorgCantor's diversion worked relatively well. Meanwhile, I still note "ape-like intuition" and have a hearty chuckle. How have we come to this given the OP?

I'd say that the moment i stopped responding to your mischaracterizations of my posts, the discussion got back on topic - What it is that QM describes and why nobody seems to understand it. But nice try anyway.

 

[GeorgCantor]

What does classical physics get even partially right? As I understand it, the equations are slightly wrong in all circumstances and wildly wrong in some. But more to the point, the theoretical basis is incorrect.

We get better approximations and we are definitely getting more accurate answers. We built internal combustion engines and airplanes without the aid of GR and QM. In certain 'everyday' domains, classical physics is still a perfectly valid tool. F=m.a is still as good as it gets within the same referrential frame. With better approximations and better theories, we get a better understanding of what reality is. Now if everything we have built as a model of how reality works is wrong, then yes, you might say that we are chasing a red herring, but as far as i know, there is no better way to understand reality than through physics.

We now know, through the aid of quantum physics, that matter is not made of balls but of entities that are neither particles nor waves in the classical sense. Whatever it is that an electron really is prior to interaction/measurement/decoherence, we now have a better and truer knowledge of reality. Agree?

Even if we are living in the Matrix, classical physics has a valid domain to fill in, and it's definitely a good approximation for mundane 'everyday' purposes.

 

[waht]

QM is a non-relativistic quantum theory.

QFT (Quantum Field Theory) is a relativistic quantum theory that explains three of the fundamental forces with stunning accuracy, and it could explain gravity all in one shot but we are getting lots of infinities in the equations.

QFT eventually breaks downs at very hight energies, but within its range of operation it's the most accurate theory yet, with predictions verified to more than 9 decimal places.

The cool part is QFT can be easily simplified to QM if needed.

 

[GeorgCantor]

Indirectly yes, but I don't think it's appropriate to say that "the theory describes reality" if this is the case. That phrase should be reserved for situations when the theory describes only the relevant aspects of our universe, and not for situations when it describes a much larger system that may or may not exist.

I agree with this, what i meant to say was that QM is likely an incomplete model of reality but not a wrong one. Confusing as it is, it's still a far better glimpse at what reality is, than classical physics.

No fear or anxiety is needed to admit that the possibility exists. A healthy respect for logic is sufficient.

The possibility exists, i'll concede that. But given our previous experience from Newtonian and relativity physics, we have good arguments to believe that qm is actually describing reality(or at least aspects of it). It is a far more interesting avenue to explore, given the philosophical inclination of the participants here, and a far more promising one. Classical physics is at a dead-end on most of the questions asked in the philosophy forum.

 

[GeorgCantor]

QM is a non-relativistic quantum theory.

QFT (Quantum Field Theory) is a relativistic quantum theory that explains three of the fundamental forces with stunning accuracy, and it could explain gravity all in one shot but we are getting lots of infinities in the equations.

QFT eventually breaks downs at very hight energies, but within its range of operation it's the most accurate theory yet, with predictions verified to more than 9 decimal places.

The cool part is QFT can be easily simplified to QM if needed.

Yes but what do you make of it all? Is this how reality is, based on the fact that qft 'explains three of the fundamental forces with stunning accuracy'. The only ontology, as far as i am aware, consistent with qft is the Relational Block Universe, which i take to be a case for a virtual world.

 

[Jimmy Snyder]

Agree?

You seem to be of two minds. On the one hand you agree that the model might be a red herring. Yet on the other hand, you claim that it brings us a truer knowledge of reality. How can I agree with that? We were bitten once by a stunningly good model, what makes you think it won't happen again?

 

[Fredrik]

Orbits of planets - classical mechanics gets the wrong orbits. The case of the planet Mercury around the sun is a famous example.

That if you drop an apple it falls to the ground - classical mechanics gives the wrong trajectory.

That a current through a wire will produce a magnetic field - it gets it wrong for the current associated with the orbit of an electron in an atom, qualitatively as well as quantitatively.

that a gas cools when it expands - gets the wrong equation because the rate of expansion is frame dependent.

time dilation - no, it failed to predict that.

the expansion of the universe - no, it failed to predict that.

We could probably fill a book just with the examples. - that's my point. There was a time when they did fill books with the examples because the predictions were "stunningly correct".

It's pretty frustrating to get this type of reply. First of all, you're clearly answering as if my post had been a reply to a different question than the one you actually asked. You need to go back and look at what I actually replied to. You asked "What does classical physics get even partially right?", so what you're saying now sounds like complete crazy talk to those of us who remember that. I'm sure you didn't intend to suggest that orbits are nothing at all like ellipses, but that's what you did.

Second, you're wrong about several of these things, regardless of what you think you're replying to. For example, time dilation is a prediction of special relativity, and special relativity is a classical theory.

Third, it's clear both from this post and your previous one that you think it's meaningful to label theories as either "right" or "wrong". It's not. They're all wrong. Some are just less wrong than others, and those are the ones we consider "good".

 

[waht]

Yes but what do you make of it all?

Is this how reality is, based on the fact that qft 'explains three of the fundamental forces with stunning accuracy'.

The definition of a "theory" in science loosely consists of two parts. The first part of a theory is a set of facts, evidence, and experimental data. And the second part is deductive explanation and analysis of that data.

A "theory" doesn't claim what reality is.

Theories like Classical Physics, GR, QM, QFT, are deductive explanations of empirical evidence that work up to a certain limit. That's all.

 

[Jimmy Snyder]

It's pretty frustrating to get this type of reply. First of all, you're clearly answering as if my post had been a reply to a different question than the one you actually asked. You need to go back and look at what I actually replied to. You asked "What does classical physics get even partially right?", so what you're saying now sounds like complete crazy talk to those of us who remember that. I'm sure you didn't intend to suggest that orbits are nothing at all like ellipses, but that's what you did.

Second, you're wrong about several of these things, regardless of what you think you're replying to. For example, time dilation is a prediction of special relativity, and special relativity is a classical theory.

Third, it's clear both from this post and your previous one that you think it's meaningful to label theories as either "right" or "wrong". It's not. They're all wrong. Some are just less wrong than others, and those are the ones we consider "good".

I think all theories are wrong. I am curious to have you identify what made you think I didn't.

There is an issue of vocabulary which I got wrong. When I said classical physics, I meant pre-1900 physics. This was an error which may have mislead people as to my meaning. This is why post-1905 predictions were in your post. I apologize for that. However, the problem with the orbit of Mercury was known before 1900.

I have answered all posts in the context of GeorgeCantor's post. Anyone who replied to my posts out of that context was probably surprised and dismayed when instead of interpretting their words as they meant them, I interpretted them within that context. Read Georg's post to see what my issue is. If you are not posting to that issue, then your post may well be misinterpretted.

My attitude toward science is that it gives us tentative theories that are good pending the next experiment. All that truth and reality stuff belongs in a philosophy or religion forum.

 

[Fredrik]

But given our previous experience from Newtonian and relativity physics, we have good arguments to believe that qm is actually describing reality(or at least aspects of it).

That...sounds like a prejudice.

It is a far more interesting avenue to explore, given the philosophical inclination of the participants here, and a far more promising one. Classical physics is at a dead-end on most of the questions asked in the philosophy forum.

I find it a bit odd that you seem to think of classical physics as the alternative. A person who believes that QM doesn't describe reality (or rather that the system it describes is much larger than anything that "actually exists") isn't automatically going to want to go back to classical physics.

Personally, I think it's definitely worthwhile to study the consequences of the assumption that QM describes an actual physical system. I also think there's lots of work that remains to be done in that area, because most of the work that's been done on "the" MWI has been based on the misguided idea that the Born rule can be dropped from the theory and derived from first principles.

A lot of people think it would be a complete waste of time to study the consequences of the assumption that QM describes reality, since it doesn't change the predictions of the theory. I think they're a little naive. Even if the assumption is wrong, we could learn a new way to think about QM that might even turn out to be useful when doing calculations.

I disagree with your reasons to think that QM describes reality, but I think there's a reasonable chance that QM with this extra assumption can be combined with anthropic arguments to explain a lot of things that "just QM" can't. I'm thinking of questions like, "why is there such a thing as time?" or "why did the universe start out in a low entropy state?" (No, I don't have the answers...at least not yet ).

 

[Fredrik]

I think all theories are wrong. I am curious to have you identify what made you think I didn't.

I expressed myself poorly there. What I should have said is that you seemed to think that a theory being "wrong" is a bad thing, but maybe I was wrong about that.

My attitude toward science is that it gives us tentative theories that are good pending the next experiment.

My attitude is that Newton's theory of gravity is still an excellent theory more than a century after the first inaccuracies in its predictions were discovered, and almost a century after a much better theory was found. To call these theories "tentative" makes it sound like we're keeping our fingers crossed hoping that "this one will be correct", and that we should be disappointed about our failure when we find a situation where its predictions are clearly wrong.

 

[Jimmy Snyder]

To call these theories "tentative" makes it sound like we're keeping our fingers crossed hoping that "this one will be correct", and that we should be disappointed about our failure when we find a situation where its predictions are clearly wrong.

OK, as long as you realize that you said all that, not me. I'll be out there dancing a jig and saying "told you so, told you so".

 

[IcedEcliptic]

I'd say that the moment i stopped responding to your mischaracterizations of my posts, the discussion got back on topic - What it is that QM describes and why nobody seems to understand it. But nice try anyway.

Right, and yet you're still suffering from a flux of the mouth. All you have is a rigid outlook and bombast. Boring.

 

[glengarry]

but if everytime we do a measurement/observation we get an accurate result that exactly conforms to the calculations

The formalism of QM says precisely nothing about any given experiment that is performed once. It is only when a given experiment is performed an infinite number of times that the quantum mechanical "prediction" is said to have been finally realized.

This also means that if a given experiment is performed any finite number of times (no matter how large this number is), then there is not any kind of purely "quantum theoretical" statement that can be made about it.

It is for the reason that infinite experimental trials must be performed within the formal theory of QM that it can never, strictly speaking, have any kind of applicability to the universe of "real world" experimentation.

 

[GeorgCantor]

That...sounds like a prejudice.

Only up to a point. I believe that qm, qft and GR are describing reality as it is, i.e. they are a truer description of reality than our gross sensory inputs are leading us to believe. Those 3 theories are almost forcing us to reconsider the meaning attached to the word "universe" and possibly replace it with "reality". But you are free to label this assumption of mine a 'predjudice'. It seems modern physics isn't describing a universe but a reality that seems to look like a 'dance' of energy to the tune of the laws of physics. What we uncomfortably choose to label 'Particles' in my view, are simply blobs of energy that have acquired the ability to gain mass(rest or relativistic). Everything we interact with is based on an exchange of energy through electromagnetic repulsion. Assuming that everything may essentially be a form of energy, i see no contradictions with beginnings, zeno-like paradoxes, epr's, length contractions, time delations, singularities, quantum tunnelings, etc. There is no good definition nor good understanding of what energy really is, and yet the glimpses we were able to take at reality through quantum physics, are in my opinion incredible. I think we are fooled to believe in a fixed inmutable universe of objects in space and time by our place in it and how we are structured. It is modern physics that is giving us the opportunity to reach for some underlying truths, though not everybody may like them. Yes, it is assumption and to a point predjuice, but at least it's the most convincing one there is, imo. While science may or may not be a good tool to understand reality as it is, IMO it has more merit than all other approaches taken together.

A lot of people think it would be a complete waste of time to study the consequences of the assumption that QM describes reality, since it doesn't change the predictions of the theory. I think they're a little naive. Even if the assumption is wrong, we could learn a new way to think about QM that might even turn out to be useful when doing calculations.

Yes and this new way to think about QM might be based around the idea that reality simply isn't quite the way it seems. It's a good starting point for making progress on the foundational issues in physics and seems to come down to the old question - What is matter really?

 

[glengarry]

Yes and this new way to think about QM might be based around the idea that reality simply isn't quite the way it seems.

The idea that reality isn't constituted by its phenomenal manifestations is far from a new idea. That is, it didn't take a bunch of white guys in 1920's continental Europe to come to the realization that any fundamental description of nature must necessarily be something other than the way that our eyes (or any other sense organ) apprehends it.

It's a good starting point for making progress on the foundational issues in physics and seems to come down to the old question - What is matter really?

Well, I started this thread quite a while ago in order to do my best to describe a mathematical "picture" that I think can go a long way towards answering this question. I'm just waiting for someone else to show interest in my ideas before I post again to that thread.

 

[xcvxcvvc]

I don't know anything about quantum theory, but i liked that youtube video. Could someone tell me if the "no one knows what is going on and it seems impossible" conclusion at the end of this video is correct?

 

[GeorgCantor]

I don't know anything about quantum theory, but i liked that youtube video. Could someone tell me if the "no one knows what is going on and it seems impossible" conclusion at the end of this video is correct?

I don't think many would agree that an observer collapses the wavefunction(i.e. we are creating our own reality), but there is something weird and subtle about this experiment. The Delayed Choice Experiment(and the one with the eraser and un-collapse) and the double slit(and the one done with fullerene molecules) all seem to suggest that quantum 'particles' act in a way to preserve conjugate variables. Essentially this is saying that the observed particles are 'hiding'(masking) the information that we are trying to extract, so as to not violate the uncertainty principle. This is a very weird conclusion and one that is not easy to come to grips with, as it seems to suggest that the observer's knowledge of the quantum system can affect how the system behaves. I agree with the statement from the video that "the particles act as if they were aware that they were being watched". And if our knowledge or even the prospect of knowing, can somehow affect assumed outside real-world quantum systems, this can have profound implications for the role we have in reality.

It gets more interesting when you ask 2 questions:

1. What is knowledge and is it such an essential ingredient of reality?

2. Is the observer really separate from the system being measured?