# Who here has a basic understanding of quantum physics?



## tanstaafl28 (Sep 10, 2012)

@Clyme

There's probably about a dozen or so people IN THE WHOLE WORLD who understand it fully. 

Basically, the laws that work for really big objects, like planets and stars, don't work for really small objects, those smaller than an atom. Really small particles do all sorts of crazy stuff that doesn't seem possible.


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## PaladinX (Feb 20, 2013)

Quarks, and Gluons, and Bosons, oh my!


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## Diophantine (Nov 24, 2011)

Comfortably Numb said:


> For one, you're taught that the wavefunction collapses after observation (Copenhagen interpretation). This is not true. The wavefunction continues to evolve in time. You're also taught the energy-time uncertainty principle, which is a myth. There are a few other interesting myths as well. If you're interested in hearing about them, feel free to PM me.


As far as I knew, uncertainty principle holds for most theoretical constructs as well as real physical systems, so I'd be interested to know which particular systems you are talking about. I mean, I see how time-energy uncertainty is not universally valid, i.e. it cannot be used for some types of Hamiltonians, but to say it is a "myth" (while it still applies to a variety of systems) is stretching it.


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## Comfortably Numb (Sep 26, 2014)

Diophantine said:


> As far as I knew, uncertainty principle holds for most theoretical constructs as well as real physical systems, so I'd be interested to know which particular systems you are talking about. I mean, I see how time-energy uncertainty is not universally valid, i.e. it cannot be used for some types of Hamiltonians, but to say it is a "myth" (while it still applies to a variety of systems) is stretching it.


The reason it's a myth is because time isn't an operator in QM. It behaves like a classical parameter, unlike position and momentum, which _are_ operators. Since it's not an operator, you can't commute it with energy like you commute position and momentum. I think Ballantine's text on QM explains this very well. I'm assuming you learned QM from Griffiths like most people, so you should consult more advanced books if you want to understand some of the subtleties.


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## Diophantine (Nov 24, 2011)

Comfortably Numb said:


> The reason it's a myth is because time isn't an operator in QM. It behaves like a classical parameter, unlike position and momentum, which _are_ operators. Since it's not an operator, you can't commute it with energy like you commute position and momentum. I think Ballantine's text on QM explains this very well. I'm assuming you learned QM from Griffiths like most people, so you should consult more advanced books if you want to understand some of the subtleties.


OHHH! I see what you mean. I think Griffiths explained it as a time parameter for an observable (or how much it takes for it to change by a std. deviation). We solved some problems about the time it would take some wavepacket to pass through a region using it. I think this was even before the notion of commutators was introduced. 

Errr, but yeah, now it bothers me. Going to check out that Ballantine text.


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## Comfortably Numb (Sep 26, 2014)

Oops, I spelled Ball*e*ntine's name wrong the first time. But yes, definitely check it out. It's a great book.


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## BigApplePi (Dec 1, 2011)

If we are going to understand quantum mechanics, at the minimum we should review the experiments that have been done and explain how we got the sub-atomic particles speculated upon and what each is. Experimental nuclear physicists know about this.

One can google for utubes in an attempt to get started. 

For me, I found myself by-passing first base and having to go to 2nd and 3rd base which is upsetting after failing to touch 1st base safely, lol.


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## Chichi01134 (Oct 7, 2014)

I have been studying quantum mechanics for a hobby, and to everyone who's looking for a good explanation about it, I suggest you look either into several wikipedia websites about quantistic physics, or you buy a really good book about it that I happened to have in my hands just once. I think it was written by a paraplegic guy. I may have to ask my friend Luke about it, since he was the one who lend it to me. :S


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## Din (Aug 17, 2012)

I can do QM if I pretend it's functional analysis.


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## Grandmaster Yoda (Jan 18, 2014)

I know the double slit experiment and delayed choice quantum erasers but I know nothing else. According to one .pdf it does not violate causality and determinism based on something called the separation fallacy. Point being people don't attribute causes of certain events correctly in these experiments, resulting in the conclusion of retrocausality which is where an effect comes before a cause. But you wouldn't come to this conclusion if you did not employ the fallacy. I didn't read much up on the fallacy to explain it. All I know is that based on what I read I understood the experiment correctly and didn't employ the fallacy.


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## OberonHuxley (Jun 2, 2013)

I know photons can travel back in time without violating causality. I know muons travel back in time when they bounce off the moon and hit the surface of the earth. I know electrons can become entangled and form quantum black holes between each other and engage in superluminal affects..

And I know non-locality means an electron can occupy two spaces at once...

And I know we are trying to measure beyond the higgs field.


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## Despotic Nepotist (Mar 1, 2014)

Chichi01134 said:


> I have been studying quantum mechanics for a hobby, and to everyone who's looking for a good explanation about it, I suggest you look either into several wikipedia websites about quantistic physics, or you buy a really good book about it that I happened to have in my hands just once. I think it was written by a paraplegic guy. I may have to ask my friend Luke about it, since he was the one who lend it to me. :S


I think you're referring to Stephen Hawking. Was it _A Brief History of Time_?


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## Chichi01134 (Oct 7, 2014)

yes, that was the book. Thank you sir.


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