Quantum Query

[El_Machinae]

No they can't:
http://en.wikipedia.org/wiki/Spin_(physics)

The ultimate unstoppable ... er ... force, eh?

 

[Perfection]

Your right it is a slight misnomer in that it leads people to believe they actually spin like a top round and round from 0 to 360 degrees when in fact IIRC from what I was told they jigle back and forth. I wish I could show you the hand movement I was shown but I'll just have to picture it

_\|/_ back and forth something like that although the if you see what I mean but not in a 180 degree arc that's artisitic licence.

In theory if you reached absolute 0 then all atomic motion would stop, most people believe that it's not possible to reach absolute zero.

No spin is completly abstract. It's unlike any concept of spin we know. (at least for electrons) And even at absolute zero electrons still have spin

I'm not sure the universe would explode should the EM forces stop, I'd like to see perfection provide a link to that, but then I think he was joking.

Quantum Physics 2nd Ed., Eisberg and Resnick, Pages 345-348

The ultimate unstoppable ... er ... force, eh?

Angular momentum

 

[El_Machinae]

Unstoppable momentum? Doesn't that strike you as odd?

 

[Souron]

No. An object in motion will remain in motion unless a force acts upon it. Since no such force is possible, you get unstoppable momentum.

 

[Sidhe]

No spin is completly abstract. It's unlike any concept of spin we know. (at least for electrons) And even at absolute zero electrons still have spin

Thanks for the book but I don't have it, I'll have to take your word for it, sounds nuts but without reading it I can't comment.

As for the spin thing I'll have to check on that, the guy who told me has a PhD in physics but this does not make him right, he may well of been misinformed.

As for electrons having spin at absolute zero that's totally hypothetical, how on earth could you know that? And it's Ok I know why they say even at absolute zero there is still motion I just have a problem with assertions made with no evidence. Call me old fashioned

 

[Bill3000]

As for electrons having spin at absolute zero that's totally hypothetical, how on earth could you know that?

Bah. The definition of absolute zero does not mean that there is no energy left in the system. It is only where there is no energy extractable from the system.

And the reason why is that spin is quantized. An electron cannot have zero spin by the laws of quantum mechanics.

 

[Sidhe]

Yes I know this I even said this but you missed it, I merely state that no one can know how matter will behave at absolute zero, this is the problem with QM it makes asumptions that have no basis in actual experimental evidence and then expects everyone to agree with it, sorry science doesn't work that way, all I'm doing here is saying you cannot possibly know that, hell prove me wrong show me experiments were people have viewed matter at absolute zero and not mathematical equations.

 

[Bill3000]

Well, it's impossible to have matter go to a temperature of absolute zero (third law of thermodynamics), but there have been experiments bringing it close to it.

 

[Sidhe]

close but no cigar. Don't worry though I like throwing this sort of thing in peoples faces, to my mind physics is sometimes lazy in that it writes the maths and then assumes the facts out of hand (yeah yeah heisenbergs uncertainty principle whatever) you know what I mean? Absolute knowledge or assertion without doing anything real, now this is ok but making assumpitions based on thin air is a dangerous practice. And could leave people with egg on their faces. hypothesis is eminently scientific, broad statements of fact based on it are philosophy. stick in the pile with string theory as it stands and Aether theory and M theory and oh so many hypotheticals.

 

[History_Buff]

As for electrons having spin at absolute zero that's totally hypothetical, how on earth could you know that? And it's Ok I know why they say even at absolute zero there is still motion I just have a problem with assertions made with no evidence. Call me old fashioned

Well, we can come REALLY close to absolute zero, and stuff is still moving around. And like Bill said, it doesn't mean 0 energy. And what's wrong with the equations? If they accurately predict what will happen at most temperatures, why shouldn't they be correct at 0? In fact, without such equations, how would we know absolute zero even exists?

 

[Bill3000]

Okay, how is that "close but no cigar?" If our theories state that we cannot go to absolute zero, and all we can do is go infintesimately close to it, then what exactly are you talking about?

Do you even understand thermodynamics?

 

[7ronin]

What would result from the elecromagnetic field of a single atom suddenly ceasing to exist?

Nuclear fusion.

 

[Mise]

As warpus has said, twice, "spin" is just a label, like "charge". An electron has an intrinsic spin, and so too does it have an intrinsic charge. It's a point particle, so it doesn't actually spin. They only call it spin because it interacts with a magnetic field in a way analagous to a charged sphere spinning, with direction given by the right hand grip rule.

It's a friggin wave... how can a wave spin?

Yes I know this I even said this but you missed it, I merely state that no one can know how matter will behave at absolute zero, this is the problem with QM it makes asumptions that have no basis in actual experimental evidence and then expects everyone to agree with it, sorry science doesn't work that way, all I'm doing here is saying you cannot possibly know that, hell prove me wrong show me experiments were people have viewed matter at absolute zero and not mathematical equations.

Umm...

Doesn't the fact that it is fundamentally impossible to get to E=0 imply that electron spin is always 1/2 ?

 

[Sidhe]

I don't think people are following, so I'll say it again: what your asking me to believe is that you know what the spin of an electron is at absolute zero without actually showing any evidence. Look since about 1920 quantum theory has been doing science arse about face, it makes predictions that cannot be supported experimentally and then later say 60 years later someone comes up with an experiment that fits it, before the 20tth century scientists would prove something before they asserted it was fact, that's why I said I was being old fashioned, now it seems the method of proof is to claim it's true with only maths as evidence. Maths is not real, Most of QM is speculation, remarkably it is also consistent with experimentation, however that doesn't give you the right to claim you know what will happen at 0 degrees kelvin without actually achieving it, as to whether you can, that is theoretical and I would imagine it is indeed impossible. but then I know people who claim that light is a barrier not an absolute value of speed and they're a damn site more educated than me, so I usually refrain from making absolute sweeping statements lest some experiment make me look like a pillock.

Doesn't the fact that it is fundamentally impossible to get to E=0 imply that electron spin is always 1/2 ?

Precisely Mise it is inferred: the king of QM, but it is not proven.

Nuclear fusion.

I see why exactly? And please don't give me a link that is a text book, I don't have a huge volume of physics text books, I'd ask if you could provide a link on the internet if possible please?

Come to think of it I don't have any physics text books? And recomendations for the semi layman?

Okay, how is that "close but no cigar?" If our theories state that we cannot go to absolute zero, and all we can do is go infintesimately close to it, then what exactly are you talking about?

Do you even understand thermodynamics?

Being patronising is not helpful, and besides you appear to be missing the point.

 

[Mise]

I don't think people are following, so I'll say it again: what your asking me to believe is that you know what the spin of an electron is at absolute zero without actually showing any evidence. Look since about 1920 quantum theory has been doing science arse about face, it makes predictions that cannot be supported experimentally and then later say 60 years later someone comes up with an experiment that fits it, before the 20tth century scientists would prove something before they asserted it was fact, that's why I said I was being old fashioned, now it seems the method of proof is to claim it's true with only maths as evidence. Maths is not real, Most of QM is speculation, remarkably it is also consistent with experimentation, however that doesn't give you the right to claim you know what will happen at 0 degrees kelvin without actually achieving it, as to whether you can, that is theoretical and I would imagine it is indeed impossible. but then I know people who claim that light is a barrier not an absolute value of speed and they're a damn site more educated than me, so I usually refrain from making absolute sweeping statements lest some experiment make me look like a pillock.

I'm sorry but that's the most rediculous thing I've ever heard I'm really not sure where to start, but I doubt that it will make a difference either way coming from me. It doesn't matter what wiki links you've read, unless you've studied it you won't have a clue.

Precisely Mise it is inferred: the king of QM, but it is not proven.

How is the fact that it defies the laws of physics to get to a state where E=0 not proof that an electron always has spin???. You're saying that the electron might have spin at E=0. But you can't get an electron with E=0, as it defies (unrelated) laws of physics. Therefore, electrons always have spin 1/2!

I see why exactly? And please don't give me a link that is a text book, I don't have a huge volume of physics text books, I'd ask if you could provide a link on the internet if possible please?

The only thing stopping nuclear fusion is the coulomb barrier (i.e. electrostatic repulsion between protons in the nuclei).

 

[Sidhe]

Ok Last time then I give up, it was really just an attempt to point out the arrogance of absolute assertion based on theory is stupidity, so I could of picked on anything to make this point, but it somehow seems that you don't require proof to back up the statement at absolute zero particles still move. Prove to me that you cannot reach absolute zero absolutely and when you've done that I'll agree.

Not everyone in physics agrees with standard theory, however those who learn it always arrogantly presume that there view is the only one. Prove that the wave equation fits reality, show me an electrons motion, I think my point's gone by the wayside, but nm. I don't have to study it to know that saying at absolute zero matter still has motion and then saying we can never achieve it is a contradiction that no one appears ready to admit. It's really quite indicative of the unwillingness of some people to think about what it is they're claiming, it shows a certain lack of free will, I'd say question everything you are told in QM, because there are a million and one theories apart from the accepted and they go in and out fashion. I mean string theory is the vogue atm, should it fail to provide any verifiable evidence as seems very likely it will fade into extinction. This blinkered I know absolutely stuff is encouraged by some turtors I'm somewhat wary of making judgements in a field that has a myriad of unresolved questions, it's a house of cards situation, the base is strong but the higher up you go the less stable it becomes.

I once spent a rather enlightening few days advocating Einsteins particle idea of light, I found out a great deal and I also found out that it's not widely acknowledged but his particle model also produces the same results as the wave model, which is why he proposed it. I don't agree with it but It's very informative to play devils advocate, particularly when no ones absolutely sure of anything, despite what you may be taught.

 

[Shaihulud]

Originally Posted by Sidhe
As for electrons having spin at absolute zero that's totally hypothetical, how on earth could you know that?

I always assume that Bose Einstein condensate reduces the integral spin of electrons, that is possibly the lowest temperature that we can get bosons down to at the moment. At that very low temperature, electrons starts dropping down to the possible lowerst energy level and forming a new state of matter, stacking on top of each other. The only way that i can for that happening is if it loses the quality of "spin".

 

[Sidhe]

I believe they have achieved these states in temepratures as high as -167 degrees C or there abouts. It's ok I know the basics behind this theory and why they advocate what they advocate as I mentioned, I've been wanting to make a point about physics for ages but no one has said anything contraversial enough untill Perfection.

It's a conclusion I came to from studying and talking to those involved in Quantum Mechanics theory that sometimes people are a little to mainstream for their own good, particularly those studying at degree level, now I'm probably not educated enough to cast aspersions but I am open minded and I don't have much patience for proseletysers any more, although they are remarkably interesting, suffice to say I agree matter wouldn't in theory stop at absolute zero, but then that 's the point in theory.

best quote I ever read about someone giving "facts" on quantum mechanics was from an experimental phsysicist ,

I too am surprised at just how willing people are to accept all the links I give them and not to question them.

I'm paraphrasing here:

It was response to me suggesting that when the guy was first learning the subject I bet he had many questions which would of annoyed his tutors too.

I'm just advocating curiosity not blind acceptance, It's a sort of philosophy I have about learning that it should be interactive not pure absorption and repitition, I'll shut up now anyway, I think I made the point, not that anyone cares though I suspect

 

[El_Machinae]

It's a friggin wave... how can a wave spin?

Whirlpool.

That's why I used the tornado analogy.

Again, to be honest, at the level of an individual electron, I tend to see mathematical formulas whirling around, because I don't have a good analogy to visualize an electron.

 

[Perfection]

Unstoppable momentum? Doesn't that strike you as odd?

It's angular momentum which is not the same thing. And while it is odd, it's the way it is.

As for the spin thing I'll have to check on that, the guy who told me has a PhD in physics but this does not make him right, he may well of been misinformed.

Well, it still is angular momentum, it's just not in a form you're familiar with.

As for electrons having spin at absolute zero that's totally hypothetical, how on earth could you know that? And it's Ok I know why they say even at absolute zero there is still motion I just have a problem with assertions made with no evidence. Call me old fashioned

Yeah, it's hypothetical. In reality if you get stuff to absolute zero the universe explodes and electron spin is the least of your worries. I say that electrons would still have spin because all the increasing trends at the lower temperature scales (like uncertainty of position) have no effect on spin. And really an electron without spin would be like an electron without charge.

I see why exactly? And please don't give me a link that is a text book, I don't have a huge volume of physics text books, I'd ask if you could provide a link on the internet if possible please?

It's pretty simple. If quarks suddenly stopped having charges via some sort of magical fairy, then only the strong force would remain. The absense of the repulsive forces of electromagnetism I imagine would allow for nuclei of arbitrary size. (not knowing QCD very well I'm not sure if it's entirely accurate, but it seems pretty plausible).

I always assume that Bose Einstein condensate reduces the integral spin of electrons, that is possibly the lowest temperature that we can get bosons down to at the moment. At that very low temperature, electrons starts dropping down to the possible lowerst energy level and forming a new state of matter, stacking on top of each other. The only way that i can for that happening is if it loses the quality of "spin".

The electrons don't lose spin, they pair up into Cooper Pairs. Cooper Pairs are two electrons bound together in such a wa that thier spin cancels each other out. It allows electrons to act like bosons.