Why is Quantum Physics so Strange?

[ChrisisC]

I want to be a quantum physicist as a career because i absolutely love the mystery behind certain principles in quantum physics. Especially things like the quantum eraser experiment. I am wondering if there is a reason that quantum mechanics has very weird principles that seem to defy logic, like quantum tunneling.

 

[Daniel Hendriks]

I think it is a mystery because the old one isn't known yet.

 

[PeterDonis]

I am wondering if there is a reason that quantum mechanics has very weird principles that seem to defy logic

I would say that you are asking this question backwards. The question ought to be, why do our human minds find the principles of QM "weird"? QM was there before we were; it is just how the universe runs. If our minds have trouble understanding it, that's an issue with our minds, not QM.

 

[Stavros Kiri]

I am wondering if there is a reason that quantum mechanics has very weird principles that seem to defy logic

That very reason is our existence! ...
Because we wouldn't exist if it weren't for Quantum Mechanics! ... (e.g. there wouldn't be stable atoms ... etc.)

Thus, even every day life supports QM and Quantum physics.

[Another example is E=hf, observed all the time ...]

 

[phinds]

I am wondering if there is a reason that quantum mechanics has very weird principles that seem to defy logic ...

There was a very long thread discussing exactly this. Try a forum search. Hint: start with the links at the bottom of this page.

 

[bhobba]

It depends on how you look t it:
http://www.scottaaronson.com/democritus/lec9.html

Also much of the strangeness is 'hyped' by popularization's. Move a bit beyond that to actual textbooks and you will find slowly it becomes less strange.

Thanks
Bill

 

[secur]

I want to be a quantum physicist as a career because i absolutely love the mystery behind certain principles in quantum physics. Especially things like the quantum eraser experiment.

Don't go into theoretical physics because you're interested in quantum "weirdness" - i.e. QM interpretations. By the time you get a degree, funding for this sort of thing will be nonexistent because it's completely useless. In fact, even today such jobs are rare. If you want to be a physicist, concentrate on real physics: the more applied, the better. QM (and the rest of physics) is essential for material science, optics, chip design, weapon design, experimental apparatus like Hubble, gravity wave detectors, and CERN, etc. Funding will always be assured because people make billions from these technologies that build modern devices. The physics involved is actually much more interesting than QM interpretations. If you can't get into some such topic, find a different career.

That doesn't mean you can't learn QM interpretations also. With "real" physics under your belt you'll know everything that counts: the math, and what it means in practice. You can dabble in QM "weirdness" after you make your first million. I figure in about 20 years, the solution will be understood. It will be simple, not weird.

I am wondering if there is a reason that quantum mechanics has very weird principles that seem to defy logic, like quantum tunneling.

Yes, there is a reason: most of the people working on those principles today are not logical. And the less logical they are, the more noise they make. Wait about 20 years for them to retire or at least get out of the way.

 

[Stavros Kiri]

Don't go into theoretical physics because you're interested in quantum "weirdness" - i.e. QM interpretations.
... out of the way.

Nice attempt to land him. But that's more like "grounding"! ...

I agree about the financial part/issue; and you are right about technology.

But you are a little cynic and harsh against theoretical physicists etc.

Yes, there is a reason: most of the people working on those principles today are not logical. And the less logical they are, the more noise they make. Wait about 20 years for them to retire or at least get out of the way.

! ... so did/were Heisenberg, Schrodinger, Einstein, Bohr, Max Born, De Broglie, ..., Feynman etc. ??! ... (most Nobel winners - we owe them QM, QED(&QFT..) and more! ... - so that e.g. you/we can understand Quantum Optics, modern Electronics etc. and make the applications you mention etc. ...) - [they are all "out of the way" now ... , but went down in history for "weird" contributions to science (physics) ]

Things are not as simple as you say. How do you know that the OP (i.e. ChrisisC) isn't the one that will solve these problems? (e.g./etc.) ... ?
Perhaps a good advice for him would be to combine both theoretical and applied physics. Budget is always an issue! ...

I figure in about 20 years, the solution will be understood. It will be simple, not weird

Don't be so sure about that! Otherwise it would have probably been found already (if it was indeed simple) ... [It's been over a century now ... and with the biggest names in history, perhaps ...].

But even every day life inevitably connects to "Quantum weirdness" [+see my other earlier post above], otherwise we wouldn't exist! ...
[But of course you might say: we do! ... (and that's all it matters? ...)]

 

[A. Neumaier]

if there is a reason that quantum mechanics has very weird principles that seem to defy logic

The answer can be found in this post and the link there.

 

[Spinnor]

I want to be a quantum physicist as a career because i absolutely love the mystery behind certain principles in quantum physics. Especially things like the quantum eraser experiment. I am wondering if there is a reason that quantum mechanics has very weird principles that seem to defy logic, like quantum tunneling.

Use a different logic. Use the Rules of Quantum Mechanics, quantum field theory, elementary particle physics as a rock solid guide, work backward and come up with a mental picture of Nature that implies the Rules of Quantum Mechanics. Good luck!

 

[bhobba]

Don't be so sure about that! Otherwise it would have probably been found already (if it was indeed simple) ...

It is 'simple' - we now know that. Its just over hyped.

This is not the thread to discuss it but if you really do believe its 'weird' start a thread detailing it. I am pretty sure once understood properly the weirdness will 'disappear'. But don't take my word for it - start a thread and we will see.

I once thought it weird thinking particles in many places at once, superluminal communication, cats alive and dead, yada, yada yada. Slowly as I learned the real thing from books like Ballentine they all evaporated. There is a deep issue - namely why we actually get outcomes at all, and we have interpretations that explain that. The thing is we can't tell them apart. That's not good - but weird - well I suppose it depends on what you mean by weird - for me - no - but that's just an opinion.

Thanks
Bill

 

[dkotschessaa]

I would say that you are asking this question backwards. The question ought to be, why do our human minds find the principles of QM "weird"? QM was there before we were; it is just how the universe runs. If our minds have trouble understanding it, that's an issue with our minds, not QM.

Relativity is weird!

Did Newtonian physics seem weird in Newton's time? Is there anything in classical mechanics that still seems weird to anyone?

 

[A. Neumaier]

Did Newtonian physics seem weird in Newton's time?

Yes, even to Newton himself - he didn't like action at a distance!

 

[bhobba]

Is there anything in classical mechanics that still seems weird to anyone?

Well actually there is eg the first law follows from the second - so why have it. But start a thread in the classical mechanics section if you want to explore it.

Thanks
Bill

 

[Stavros Kiri]

Well actually there is eg the first law follows from the second - so why have it. But start a thread in the classical mechanics section if you want to explore it.

Thanks
Bill

That's more like a "structural weirdness" (of the theory), thus minor.
But the 1st law did in fact come first anyway, before the 2nd was discovered ...

 

[Stavros Kiri]

It is 'simple' - we now know that. Its just over hyped. ...
...just an opinion.

Thanks
Bill

I myself believe it is in fact simple, but not fully conceptually resolved and understood.

Moreover, I pretty much support the Standard [Copanhagean] Interpretation of QM ... (Probabilistic interpretation of the wave function, superposition principle, selection rules and filtering principle, and relation between observer and instrument, etc.) ... which is "a bit weird" ...

But there are [still] [unresolved] issues, at least at the conceptual level, regarding e.g. the profounds of the exact nature of the relationship between counsciousness (observer) and measurement [process] (instrument) ..., that could even lead to non-realism and idealism, or even animism.

Other more formalistic [open(?)] problems involve the possible incompleteness of QM, Bell's inequalities, Hidden Variables and more ...

To say "it is in fact simple", one has to answer adequetly all these questions and problems, and more ...
These are [still - as far as I know] nice and neat open fields for research, no matter what anyone else sais/ has to say. And [probably] they will still bring "bread" and opportunities both for theoretical and experimental physicists in the future! ...
{So I would probably say, for the OP, "Trust and follow your heart and intuition ...", "consider all views and available data and information ... and make your own good choice! ..."}

By the way, Particle Physics (e.g. either theoretical or at CERN) is a different domain, but they are related ...

Overall, keep an open mind ..., and never say [QM] "it's simple" or "weird"! ... It's both!

 

[dkotschessaa]

Well actually there is eg the first law follows from the second - so why have it. But start a thread in the classical mechanics section if you want to explore it.

Thanks
Bill

I wasn't aware of this. Sounds a bit like debating postulates in Euclid.

-Dave K

 

[David Neves]

With both quantum mechanics and relativity, the more you understand it, the less "weird" it seems, and the less you understand it, the more "weird" it seems. From the point of view of physicists, quantum mechanics is not "weird" at all. If you are a physics professor teaching a class in quantum mechanics, or writing a textbook on quantum mechanics, your goal is to make it seem as intuitive as possible. If you are a popular science writer trying to write a magazine article or tv show for the general public, your goal is to intentionally make it seem as counter intuitive as possible because you are catering to a niche audience that enjoys being freaked out by supposed "quantum weirdness". It's fine if your initial interest was originally sparked by reading popularizations when you were kid, but after that, if you want to actually learn the subject, don't believe anything you read in popular accounts, and instead read actual physics textbooks.

If you want to be a physicist, concentrate on real physics: the more applied, the better. With "real" physics under your belt you'll know everything that counts: the math, and what it means in practice.

I could not disagree more strongly with this statement! The more "applied" physics is, the less "real" it is! The less "applied" physics is, the more "real" it is!

What do you think physics is? The goal is physics is not to put new products on the shelf at Walmart. The goal of physics is to understand the Universe. The most "real" physics is advanced theoretical particle physics, high energy physics, string theory, other attempts at quantum gravity, and cosmology. There is no "practical application" of the discovery of the Higgs boson at the LHC, gravity waves at LIGO, neutrino oscillation, dark energy, the AdS/CFT correspondence, brane worlds, Monstrous Moonshine, etc. The farther your work is removed from your mundane daily life, petty human affairs, and our limited experience, the closer it is, potentially, to uncovering the deep truth of the Universe at the most fundamental level, which is, after all, supposedly the goal of what I consider "real" physics.

 

[dkotschessaa]

Yes, there is a reason: most of the people working on those principles today are not logical.

This is a baffling statement.

 

[dkotschessaa]

I would think that the perception of weirdness is not a linear function of how much you know. Is not one's appreciation for it's weirdness raised by understanding enough about physics to know why it is weird to begin with? The curve is likely to slope back down as ones understanding grows.

I'd almost be surprised if there is no xkcd comic with the above written as a plot.

-Dave K

 

[Stavros Kiri]

If you want to be a physicist, concentrate on real physics: the more applied, the better.

And/vs

I could not disagree more strongly with this statement! The more "applied" physics is, the less "real" it is! The less "applied" physics is, the more "real" it is!

I wouldn't exactly put it that way.
I think the problem is that applied and experimental sciences (not just physics) are subject to improper (incomplete) induction:

https://www.physicsforums.com/threads/lame-jokes.25301/page-166#post-5648419

But they are still very usefull and important!

On the other hand, all theories are subject to falsification (Popper..) ...
So, my two friends, "you go figure ..." ...

[PLEASE SEE THE LINK ABOVE.]

 

[bhobba]

But there are [still] [unresolved] issues, at least at the conceptual level, regarding e.g. the profounds of the exact nature of the relationship between counsciousness (observer) and measurement [process] (instrument) ..., that could even lead to non-realism and idealism, or even animism.

That is very interpretation dependent. We have interpretations where its trivial (eg BM), Neutral (eg Copenhagen) and those where its a big problem (eg many minds).

Now we are talking about a genuine issue in QM. It's a mater of opinion if its weird - physics is not a game of semantics - you make your own mind up if this and other genuine issues are weird - I have laid my cards on the table and said IMHO its not weird and I do not think most people would classify this sort of stuff as weird - interesting yes - but weird - no. Still its just semantics.

The issue is this - pick anything about QM that worries you - in your case the consciousnesses link - we have interpretations where its a non issue and those where it's front and center. That is a big problem - science is about deciding via experiment and no one has figured out an experiment to decide it. BTW these days consciousness being involved in QM is only in very backwater interpretations - its way out of favor.

How it became involved and why its out of favor has an interesting history - but should be in another thread. Also it must be said just because its backwater it doesn't make it wrong - no interpretation is better (or worse) than any other - the choice is purely a personnel matter.

Thanks
Bill

 

[bhobba]

That's more like a "structural weirdness" (of the theory), thus minor.
But the 1st law did in fact come first anyway, before the 2nd was discovered ...

The second is a definition so how can it be a law?

But this is not the place to discuss it - go over to the classical mechanics section.

The answer has relevance here because it involves QM - at rock bottom the 'why' and proper laws of classical mechanics depends on QM and symmetry. But here is not the place to discuss it (the book on its proper presentation is Lanadau - Mechanics - but that is just by the by - it needs its own thread). Newtons laws are not laws in the usual sense - they are a paradigm that says - get thee to the forces. You can't prove or disprove a paradigm - but since they have been used for centuries can't be discarded either. Its like relativity - the laws of physics are the same in all inertial frames - that's not a usual law either - strictly speaking its a meta law - a law about laws. Its slightly vacuous since it depends on what is meant by law - to a physicist its obvious - but a philosopher might have issues. Note we don't discuss philosophy here so it not a problem.

Thanks
Bill

 

[dkotschessaa]

The answer has relevance here because it involves QM - at rock bottom the 'why' and proper laws of classical mechanics depends on QM and symmetry.

Based on this I have a question that I think is relevant. If I understand correctly (I am a math guy and haven't done physics in awhile) the current learning paradigm is Classical Mechanics --> Relativity --> QM

Now QM seems "weird" possibly coming from a classical approach until the shock wears off. But is it possible that, given enough time, experimentation, and better ways of organizing our understanding, that the learning paradigm will be shifted to match the "real" paradigm (sorry for overusing the word 'paradigm') so that QM actually comes first?

This might be like proposing we teach mathematical logic and peano axioms before arithmetic, before algebra, before calculus. You can't make the case for the average student who has to take a few math classes, but you might make the case for someone who has decided to study mathematics.

-Dave K

 

[bhobba]

so that QM actually comes first?

Indeed it does.

Read Landau -please - its perfect for a math guy.
https://www.amazon.com/dp/0750628960/?tag=pfamazon01-20

The true basis of classical mechanics is the principle of least action (plus symmetry of which the principle of relativity is an example) which follows from QM (the principle of least action that is - symmetry is everywhere in modern physics).

Now the interesting twist is its one of the true basis of QM as well (ie all our theories can be expressed that way)- see:
https://www.amazon.com/dp/3319192000/?tag=pfamazon01-20

That's just plain mysterious - it seems nature at rock bottom is governed by minimum principles. We don't know why - yet.

Thanks
Bill

 

[dkotschessaa]

Indeed it does.

Read Landau -pleaae - its perfect for a math guy.
https://www.amazon.com/dp/0750628960/?tag=pfamazon01-20

The true basis of classical mechanics is the principle of least action (plus symmetry) which follows from QM.

Now the interesting twist is its one of the true basis of QM - see:
https://www.amazon.com/dp/3319192000/?tag=pfamazon01-20

That's just plain mysterious - it seems nature at rock bottom is governed by minimum principles. We don't know why - yet.

Thanks
Bill

Those look awesome. The second in particular draws my attention, though I believe you about the first. (Could be marketing!)

It will be interesting to re-visit physics when I am finished my math degree (Master's). I started with an interest in both but gravitated towards math. I couldn't bear any more inclined plane or bouncy ball problems. I probably would have a different view now.

-Dave K

 

[bhobba]

I started with an interest in both but gravitated towards math. I couldn't bear any more inclined plane or bouncy ball problems. I probably would have a different view now.

Thats not physics - that's just doing exercises.

Read Landau first - it sets the stage for the second (which, unfortunately has errors):
https://www.amazon.com/dp/0750628960/?tag=pfamazon01-20
'If physicists could weep, they would weep over this book. The book is devastingly brief whilst deriving, in its few pages, all the great results of classical mechanics. Results that in other books take take up many more pages. I first came across Landau's mechanics many years ago as a brash undergrad. My prof at the time had given me this book but warned me that it's the kind of book that ages like wine. I've read this book several times since and I have found that indeed, each time is more rewarding than the last. The reason for the brevity is that, as pointed out by previous reviewers, Landau derives mechanics from symmetry. Historically, it was long after the main bulk of mechanics was developed that Emmy Noether proved that symmetries underly every important quantity in physics. So instead of starting from concrete mechanical case-studies and generalising to the formal machinery of the Hamilton equations, Landau starts out from the most generic symmetry and dervies the mechanics. The 2nd laws of mechanics, for example, is derived as a consequence of the uniqueness of trajectories in the Lagragian. For some, this may seem too "mathematical" but in reality, it is a sign of sophisitication in physics if one can identify the underlying symmetries in a mechanical system. Thus this book represents the height of theoretical sophistication in that symmetries are used to derive so many physical results.'

After that read Ballentine:
https://www.amazon.com/dp/9814578584/?tag=pfamazon01-20

You will then understand modern QM and even QFT.

BTW the discoverer of all this was a mathematician - Emmy Noether - one of the greatest of all time:
http://www.math.umn.edu/~olver/t_/noetherpub.pdf
http://www.nytimes.com/2012/03/27/s...icant-mathematician-youve-never-heard-of.html

We have professors that teach this stuff who post here. One recounted whenever they teach Noether's theorem the class sits in stunned silence while its import sinks in. Its really is that profound. It hit me like a bolt of lightning and changed my life - but that's another story. I too was formally trained in math - but Ballentine. Landau and Noether seduced me.

Thanks
Bill

 

[David Neves]

Quantum mechanics does not require consciousness or observers.

https://www.math.rutgers.edu/~oldstein/papers/qts/qts.html

https://arxiv.org/abs/1009.2404

 

[DennisN]

I am wondering if there is a reason that quantum mechanics has very weird principles that seem to defy logic, like quantum tunneling.

Yes. The reason is because nature/the Universe seems to have very weird principles that seem to defy logic, like quantum tunneling . Quantum mechanics is just a reflection of that.

 

[Stavros Kiri]

Also it must be said just because its backwater it doesn't make it wrong - no interpretation is better (or worse) than any other - the choice is purely a personnel matter.

Is it? What about truth? What's the world's favour? That's still open ...

 

[Stavros Kiri]

The second is a definition so how can it be a law?

Definition of the force ... you mean. I prefer the approaches that take 'forces' as primitives, or measured facts, and then it is a law ... . [Isn't that what we do in practice, e.g. in homeworks? (e.g. "there is a total force F acting from a spring on a mass m ... find velocity over time ...") ...]
But let's not get more off topic, although I am sure there is paradigm analogies in QM ...

 

[Stavros Kiri]

The true basis of classical mechanics is the principle of least action (plus symmetry of which the principle of relativity is an example) which follows from QM (the principle of least action that is - symmetry is everywhere in modern physics).

Now the interesting twist is its one of the true basis of QM as well (ie all our theories can be expressed that way)-

+ i.e. cf. the Feynman path integral formuation of QM, + e.g. see
https://www.physicsforums.com/threa...on-for-principle-of-stationary-action.874921/

 

[bhobba]

Is it? What about truth? What's the world's favour? That's still open ...

Well of course. Since by definition truth is how things actually are and all interpretations are equally valid we don't know the truth. But we don't know the truth about many many things - that's nothing new.

But here is a suggestion. We do know the truth of quite a few things and some of those things like symmetry and it's role in physics is downright startling - instead of worrying about things that as Feynman says sends you down a hole no one escapes from, study them. Very very few people have been able to make fundamental contributions to the foundations of QM and most of those that have, like Bell, were truly great physicists.

Thanks
Bill

 

[Stavros Kiri]

Well of course. Since by definition truth is how things actually are and all interpretations are equally valid we don't know the truth. But we don't know the truth about many many things - that's nothing new.

But here is a suggestion. We do know the truth of quite a few things and some of those things like symmetry and it's role in physics is downright startling - instead of worrying about things that as Feynman says sends you down a hole no one escapes from, study them. Very very few people have been able to make fundamental contributions to the foundations of QM and most of those that have, like Bell, were truly great physicists.

Thanks
Bill

But until we know the full true picture, "anything is possible" ..., and we shouldn't jump to conclusions (e.g. about QM ...) ...

 

[rootone]

the reason why quantum physics is strange is because it is about probability