Mike Smith Cosmos

Hello BoB , I am heading down to our house in the Appenines in Italy mid April. I would enjoy having a discussion with you over the Forum - Physics -Quantum-Spin about some of the aspects of electron Spin and the Pauli exclusion principle, before I go, as I will not find it easy to get to the internet , up in the hills and forest ( After 14th April untill September ). I seem to have got as far as the antisymmetry aspect of 2 electrons attempting to be in the same energy level , where this is only possible by one of two states described as up spin and down spin. What I am having some difficulty is how this exclusion works in practical reality as opposed to a mathematical formulae. Any descriptive information as to what is going on, would be appreciated. As most of chemistry, the atomic structure, the universe as a whole seems to be based on this exclusion issue putting some (expansion pressure - loosely put ) upwards and outwards, to hold the atoms away from the lowest energy level. I would really like to know the nature of the exclusion principle, not just the maths that models it.

So does that mean , that when the two electrons trying to occupy the same proximity with both " ab" ( namely the same quantum number say both up spin ) that following this antisymmetry idea for two objects past each other, that one of the electrons will go to a " -ba " mode ( namely a different quantum number say down spin ) ie one up spin one down spin. Or have I got the wrong end of the stick ?

If not why perhaps How ? Could you possibly ease me into AntiSymmetrical going a little easy on the maths. Perhaps the maths but with a translation of the maths into words or concepts.

Yes we can observe it. Yes we can model it mathematically . But do we know why it is doing this very thing that we observe and then model and then predict. Am I up against the Feynman statement of yes it (QM ) stacks up to 10 to the umpteenth decimal place but we don't understand it. I have been reading about Pauli thinking about this a lot and Goodsmit and Uhlenbeck thinking a lot about it but then it goes a bit mathematical.

Are you saying that because the maths comes out with a zero that means it cant happen because this is a probability zero. the wave function presumably is the schrodingers equation with psi the wave function . I get a little worried when maths predicts something, yet one is very unsure ( or at least I am that I am totally at sea as what ( dare I say it physically ) is actually causing the electrons to put up the most giant resistive pressure to refuse to be put in the same quantum state. ( ie in collapsing stars. ) I worry that maths is describing whats happening rather than telling us what actually is happening. Are you saying that there are NOT two electrons there, these are just possible states and thus you can not put then in the exactly the same state twice at the same ( EEk Time ). I think I need to go and lay down or go for a cycle ride and look at birds. My head hurts ! Thanks . Speak to you later.

Thanks I am just trying to get my head around the Pauli Exclusion principle Wikipedia Link you gave me yesterday. Can't quite get my head round the " antisymmetric rank two tensor " and the state they get themselves in. I might need a little while and a few paracetamols. Any translation would be gratefully received.

I understand , I believe, that the de broglie wave function is a probability wave associated with everything but mainly significant at atomic levels. You are saying I believe ( do put me right ) that the electron being a fermion has an (asymmetric or antisymetric ?) wave function , not the textbook small sinusoidal rising to large sinsoidal falling to small sinusoidal again symemetrically about the peak. I have asked this before. How do these probability waves compare with ordinary constant amplitude sinusoidal Electro magnetic waves, or are they somehow part of the same thing ?

Steevey, I have been asked by the moderator and resident expert to keep these main Physics forums to strictly answers supported by published scientists rather than our own ideas. As such I need to do some more research, to dig up some published works on spin. However I feel we could throw this question of spin open to the greater scientific community in case there are some eminent scientists, who visit this forum, who are publishing scientists in this field . So :- Is there is anyone out there who can explain HOW/WHY the, Pauli exclusion principle, which we believe is responsible for the quantum property of only allowing one up spin and one down spin in a single electron pair. ( eg first orbit ) ?

Ive looked at the speculations section . I will probably try a few speculative ideas there sometime, However I would like to keep this very interesting subject of Spin going on a serious note If thats O.K.

Where is this speculations section ?

I am not totally certain where " a thread in speculations " is ? Do you mean I should start a new thread in forum with the name "speculation" in the title ? do you mean the thread "Ideas"? Perhaps you could clarify. Also what happens in the subject areas of quantum theory where nobody really knows whats going on properly and there are a lot of different ideas currently being proposed even in string theory and multiverses where little is proven if anything ?

Sorry. I have removed the questions that could lead to speculation. I have been trying to stimulate a meaningful discussion on Spin and thus angular momentum.

Overnight I have read some of Marcus Chown's comment in his book "Quantum theory cannot hurt you " chap 6 . Here he quotes Feynman in connection with spin , as saying " This seems to be one of the few places in physics where there is a rule which can be stated very simply but for which no one has found an easy explanation. It probably means that we do not have a complete understanding of the fundamental problems involved" . Chown reasons that the main difference in spin between a boson, Photon style particle having quantum spin in the range 0,1,2 and a Fermion , electron style particle having a similar one value change quantum spin in the range 1/2, 2/3, 5/3. is that :- The electron being a fermion takes part in probability wave "waveflipping" which does not affect the probability of the event , as this depends on the square of the amplitude ( always positive ) , but it only takes part in interference in a certain way, if it has waveflipped in a collision. This area of collision, waveflipping, spin up - spin down , angular momentum change , boson - fermion difference , and the link between electron and photon during radiation and absorption sounds interesting. Can you shed any light on this ?

Wave particle duality as applicable to Electrons and Photons. In all this talk of spin and the electron together with the issue of magnetism from spin being discussed in another thread on theoretical physics, there is a need to not forget the wave aspect of particles like electrons. One feature I have been a little unclear on is: - Is the wave introduced by de Broglie namely the probability wave which tends to have a central peak with waves going off on either side decreasing in amplitude, considered to be related to, identical with , another feature of , or nothing to do with the conventional sine wave of fairly constant amplitude or gently decreasing amplitude that we normally think of as EM waves of light or radio waves etc.? I did ask this once to a visiting professor speaker as he was talking about the LHC and he coughed and spluttered to the effect they were the same thing. But they look nothing like each other ! Unless they are facets of the same thing. I am interested to know which of the waves is concerned with the statement " wave particle duality " , particularly as it applies to the electron , its motion , its spin and its conversion to a photon . ?

Yes I like that expression " the physical interpretation of the mathematics. Yes by all means we need to venture into the depths to gain an quantitative or predictive view but in the end the maths has to provide some mechanism for physical reality. WHAT REALLY is going on at the Electron level. Be it that you chaps know the deep maths but what is the physical interpretation of the maths , and don't just say angular momentum and spin , because there is charge involved , there is some mass, there are some abilities for movement, and swapping with photons. Draw me a mental picture of whats going on down there. Wolfgang Paul and Hans Dehmelt Nobel prize winners 1989( not Pauli ) trapped an electron in a TRAP, it didn't like it. They kept it trapped for an hour then a few days , a month, finally a year, then it got out. May be it was quantum tunneling by the wave function ! Loose, trapped in atoms, ionized, converted to photons, full of charge ,conducting all sorts of Spin, happy in pairs within the shells. What kind of a tethered animal have we got here?

Thanks ! But there must be some overlay to the maths, unless you are saying like Mr Tegg that Maths is the bedrock rather than human constructs.

AJB Have you a book or two ( name and author) that you can give me that I can order up , or was that the one you referred to a few days ago . And can you possibly tell me how to attatch my comments to other peoples, as I seem to be making statements in isolation. ?

Are we not arriving at the difficulty of facing the crossing over from classical to quantum as if it were a different realm and out of bounds apart from the few. Surely the whole universe "exists" from the smallest point to the whole shebang . All that changes are different rules or approaches as we move through the scales. Maths does have a habit of becoming a barrier for many who approach this crossover territory. Surely it relies on those who have crossed over to make the understanding of the quantum region accessible. Otherwise we are surely in danger of sounding like priests who tell the lay people of old that the "deeper things" are our province only . Roger Penrose one of the great current gurus of maths, gave a lecture to one of the American universities ( Princetown I think ) where he described it as classical above the waterline and quantum below the waterline. Different medium, different rules , different experience but still approachable none the less. I appreciate the maths in whatever form will be a new pair of underwater goggles. But you that have gone there , tell us what you see !

STEEVEY Not all lines of scientific research are following the same approach to the fabric of space time. Some view it as a blank canvass others a void seething with activity. Frank Wilczek a Nobel prize winner and professor involved with the Large Hadron Collider, calls it Grid The which has several layers of activity including the virtual particles commented on earlier. However these are separate to the particles such as the electron pairs we were discussing . Professor Frank Close also involved with the large hadron collider speaks of it as the Void. The idea that space is empty seems to be fading fast. Neutrinos also seem to be teeming across space; from the sun ; from power stations ; through the earth ; through you by the billion; even from the Big bang. So the small though not tiny electron with its SPIN whatever that is , is quite a significant happening in amongst all this other stuff. I can visualize these pairs of electrons in some way being coupled and being particularly comfortable doing their angular momentum bit in some form of balancing "up" and "down" opposite direction. This is exactly how tuning fork prongs move. Touch one the other stops. Tap one the other moves but in an opposite direction. Try to make one vibrate on its own. It will but not as balanced and comfortable as the pair. This has striking resemblance to the electron pairs. Also if you try to bring in a third prong. No deal. Exclusion. This is only a model, but as I mentioned in a previous posting Prof Frank Wilczec says its good to have toy models untill you knock them down for something better.

Steevey, I may have something for you to visualize . I am working on some research at this very moment concerning WHY the pauli exclusion principle is invoked by two electrons in the same orbit or energy band. My area of research is to an extent looking for analogue models in the classical world where two tightly coupled particles behave in both an attractive/ repulsive coupling yet behave in opposite modes exactly. One such analogue is the tuning fork, where two similar prongs of a tuning fork vibrate in opposite directions IE one going exactly west when the other prong is going exactly east. This is irrelevant of initial striking of one prong of the tuning fork. Although this may sound crude as an equivalence of quantum mechanics , however ref:The new Quantum Universe Hey and walters 2009 edition page 58,59 shows violins bodies and drum surfaces as analogues to quantum mechanics wave functions , standing waves etc. So if we find electrons coupled in pairs as they appear to be in orbitals the equivalence of coupling and movement ( angular momentum ) may yet become evident. It is unreasonable to think of some formula or rule (pauli exclusion principle ) floating about in space , so as to impose a rule on two electrons in proximity, rather the fabric of space time and all particles and forces that such space consists of, having within itself the coupling necessary to facilitate the orientation we find happening with two coupled electrons in a given energy band or orbital. Prof Lee Smolin of Princetown University Institute in Canada, has been proposing for years that space time is not a backdrop on which thing playout thier lives (particles , forces etc) but rather Space time comes out of / or is indemically part of the particles and forces themselves. ( Quantum Gravity the road to reality By Lee Smolin). Hope this is of some help . ! Sorry Steevey I seem to have no got the method of attaching postings of mine to the members questions. Its there somewhere in the overall listing of postings

Understanding Spin in a Popular Science Form. I raised a few questions on the 23 Feb 2011 09:14 Mike Smith Cosmos , hoping that this would initiate a few comments for discussion along the lines that some of the old masters undertook during the early years of atomic Physics. Its true that this resulted in the Copenhagen agreement that some were told to " shut up and calculate " while others continued to discuss, argue, debate, think , propose, experiment and think again and help move atomic physics through to its present advanced form . Although many of the breakthroughs were made by maths orientated scientists. That is not true of all breakthroughs. Even Einstein was not the best of mathematicians but he was an expert in using lateral thought processes and thought experiments. I appreciate that the Science Forum ethos is, to not let speculative thought processes run wild , or to cloud current science understanding. However there may be scientists out there who can maintain and share with us, some form of model in their mind that is not pure maths. Although I have gone through the A level Maths, University Maths , Physics , Electronics, Satellite Communications Path, and taught physics , I still like to keep my feet on the ground to some extent when explaining either to myself or others physics concepts. I, along with a few others, would appreciate having some of these models ( be that not easy in quantum mechanics ), verbally offered, if at all possible .

I have gone some way to reading around the subject in the last three days . One or two things seem to be coming home to me. Angular momentum is a very fundamental thing for the operation of the atom thus elements. The orbital angular momentum is slightly easier to understand and visualize to some extent as demonstrated by the diagram on previous postings. Although even their uncertainty or probability still tempts wonder. Despite their fuzzy clouds one can form a mental picture however approximate or inaccurate these diagrams appear. Then we come to the electron spin itself which is said to have angular momentum of two discrete values up spin and down spin. Here comes the rub! If NOT a simple spinning Top for reasons of maths inconsistencies or problems what is the nearest or nearer approximate model that we can visualize, even if it one to shoot down and move on to a more accurate model. Frank Wilczek in his recent book " the lightness of being" page 114 " in trying to understand complicated concepts or equations its good to have toy models". So is there anyone out there who has a good toy model of :- an electron A) its movement generally , say in orbit , B) its movement in or by itself including the spin bit , C) its reality as a point, charge swirl, wiggling small mass energy or whatever lepton D) its ability or lack of to stand still E) any possible exclusion or coupling with another electron. It seems to have originated way back as a fundamental particle within the plasma or shortly after the inflationary start to the Big Bang. It has been mooted that one needs to penetrate maths to get the full picture. But surely we must cloth maths models with some form of philosophical idea !