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Post by speakertoanimals on Sept 14, 2010 12:25:52 GMT 1
AND ANOTHER THING IF an electron is in two places at once is the total electric charge (a universal constant, 1.6021765 × 10exp−19 coulomb) DOUBLED or does the individual electric charge on each occurrence of the (same) electron become one half of this universal value? An electron can be many places at once (as when it is in an atom), and hence we have a charge density, where the charge density at a point is electron charge multiplied by the probability of electron being there. Hence total charge is the electron charge, just as the total probability of electron being somewhere is 1. And knowing the exact shape of these charge distributions allows a prediction of physical variables, such as the electric dipole moment of various states. And then you can make predictions of the splitting of energy levels when the atom is placed in an external electric field, see the linear Stark effect for excited states of hydrogen.
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Post by Progenitor A on Sept 14, 2010 14:05:27 GMT 1
IF an electron is in two places at once is the total electric charge (a universal constant, 1.6021765 × 10exp−19 coulomb) DOUBLED or does the individual electric charge on each occurrence of the (same) electron become one half of this universal value? An electron can be many places at once (as when it is in an atom), and hence we have a charge density, where the charge density at a point is electron charge multiplied by the probability of electron being there. Hence total charge is the electron charge, just as the total probability of electron being somewhere is 1. We are not talking about an electron 'can be' in multiple places we are talking an electron IS in multiple places at once If an electron IS in two places at once (as someone [not me]has avered) then the probability for it being in two places at once is 1. And the charge does not depend upon a probability function. If it IS in two places at once is one of them a 'phantom' electron with no charge or do both positions hold the full electron charge?
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Post by speakertoanimals on Sept 14, 2010 17:59:47 GMT 1
We are not talking about an electron 'can be' in multiple places we are talking an electron IS in multiple places at once If an electron IS in two places at once (as someone [not me]has avered) then the probability for it being in two places at once is 1. And the charge does not depend upon a probability function. If it IS in two places at once is one of them a 'phantom' electron with no charge or do both positions hold the full electron charge? Except not in al cases is an electron in many places, hence the 'can be'. Depends on the system you are considering. You misunderstand probability. The probability is not that it is in two places at once, but which of those two you find it in if you measure its position. THAT is the probability being referred to, that is the meaning of the wavefunction. I didn't say the charge (as in the total charge) depends on the probability function, but the distribution of the charge does, since it is totally bleedin' obvious that is the electron is spread out over space, then so is the charge, hence rather than a point charge, what we should expect to see, in agreement with the basic idea that the electron is not localized, is a cloud of charge (total being the electron charge), rather than a point charge. The exact shape of this cloud (which depends on the electron wavefunction) is whatb determines the exact properties of the system being considered, whether it is the electric dipole of an atom for an uneven charge distribution, or the exact properties of a chemical bond. No, because if they did, that would mean that there was an electron at each position, which there isn't. This is really very simple, because even if you don't get quantum theory AT ALL, it is very simple to think of an electron as moving really fast around an atom, so that although in this (incorrect) classical model, the electron is actually in one place at any one time, and so is the charge, on average, we can't see the movement of the charge, but on a longer timescale, we would see the charge smeared out, depending on how often the electron visited a particular area. Hence I fail to see your problem, since even totally incorrect classical models lead quite easily to the notion of a charge cloud from a discrete charge, so why are you intent on trying to argue that such a thing makes no sense in the quantum case? The point is, this argument is pointless -- in quantum theory, the wavefunction defines a charge distribution from a single charged particle, and makes definite predictions as to what that charge distirbution is. We either have experimental measurements that are consistent with such a prediction, or we do not. Trying to argue yet again that such a concept does not make sense on classical grounds, or commonsense grounds, is totally pointless. As long as the physical quantum theory is correct mathematically, that is as good as it gets, since the very basics of the quantum theory is that classsical notions of what is or is not allowed are just plain wrong. So, all that can come out of such arguments is yet another example of the fact that you cannot build an understanding of quantum theories using classical concepts.
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Post by speakertoanimals on Sept 14, 2010 18:04:10 GMT 1
Let's make life simple -- you guys continue posting, and just accept as my standard response -- no, that is because you are trying to use classical concepts to understand/argue about the validity of quantum theories. Hence all you have shown is that quantum theories are incompatible with classical notions, which holds by definition. Like showing repeatedly that one is not equal to two, which is true, but not useful.
Would save me a lot more typing...................
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Post by Progenitor A on Sept 14, 2010 19:37:12 GMT 1
No, because if they did, that would mean that there was an electron at each position, which there isn't. An electron can be many places at once .. quantum physics just says that ....an electron can be in many places at once. And experiment agrees with the latter statement. Don't blame the universe, that just is the way it is! There seems to be a disjunct/contradiction here
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Post by speakertoanimals on Sept 14, 2010 19:46:44 GMT 1
Sigh................
An electron being in two places at once is NOT the same, in quantum theory, as a whole electron being at each place..............................
As I keep saying, common english, based on our everyday experience of what 'an object is at B' means, just doesn't deal with the concepts that quantum theory uses.
So, an electron being at A and at B at the same time means that:
1) It doesn't have a definite position, in that it is somehow in both places at once.
2) Nor is a whole electron at either place, nor a half-electron...........
3) If we measure where the electron is, it will either be wholly at A, or wholly at B. But that isn't tghe same as the state of the electron before we make the measurement, although of course the state before the measurement determines the likelihood of the various possible outcomes of the measurement.
4) Other physical variables (such as electric charge), will be smeared-out according to the many places the electron IS at, and how much more weight one place carries than another (that is, it isn't just in two places, equally spread, but can be more at one than at the other).
All of which is getting very tedious to try and say in words. In fact, you need to read a whole book on quantum theory..................
Which is why you need maths, in which case the whole thing can be stated a lot quicker, and a lot more precisely. Ordinary language just isn't up to the job, and THAT is all you will show if you keep sniping...................
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Post by Progenitor A on Sept 14, 2010 20:07:50 GMT 1
Sigh................ An electron being in two places at once is NOT the same, in quantum theory, as a whole electron being at each place.............................. sigh indeed..... It is beyond your powers to explain evidently Indeed your English is collapsing into incoherence Mathematics can probably describe the situation, but unfortunately not many people, including myself, can speak that language As Feynman says: "I think I can safely say that nobody understands quantum mechanics. "Whether you do or do not, I have no idea, but what is certain is that you cannot communicate understanding using English language, and I cannot receive any communication using mathematical language Sorry about that. Incidentally my 'sniping' as you call it is simply a genuine curiosity as to what is going on coupled to a dismay at the general inability to express what is going on. You seem to consider that I am 'having a go' at you; I am not, I am genuinely bemused. (I did have a go at you about 'God not being necesary' because there you were stepping outside your science and talking metaphysics)
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Post by abacus9900 on Sept 15, 2010 8:23:22 GMT 1
In other words, a measurement is required by human agency to 'make' the electron real. Failing this, an electron or indeed any other quantum object is merely a 'possibility.'
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Post by abacus9900 on Sept 15, 2010 8:28:08 GMT 1
Exactly, so you have just made my case for me, thank you. No observation or experiment - no particles.
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Post by abacus9900 on Sept 15, 2010 8:45:39 GMT 1
My knowledge of QM is pretty close to zero but I've read Hawkings books and just about followed what he's getting at. My impression is that QM is a series of explanations that fit observed or partially observed phenomenon and these explanations cannot be tested. Each untested explanation is then used as a sort of pseudo law that other explanations have to fit and on it goes. What if one of the early pseudo-laws are wrong? Wouldn't it follow that any subsequent explanations will be exponentially wrong. Exactly, rsmith7. So, we use mathematics (which is really only an analogy anyway) in order to quantitatively 'map' what we think the quantum world is doing. However, people tend to forget that what we are really doing is imposing macro-word concepts (i.e. maths) to sub-atomic phenomena that have nothing to do with the macro-world. This means, as you have pointed out, that we have constructed models which then give rise to further models which are all really just a 'house of cards' which will inevitably collapse.
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Post by Progenitor A on Sept 15, 2010 9:31:04 GMT 1
In other words, a measurement is required by human agency to 'make' the electron real. Failing this, an electron or indeed any other quantum object is merely a 'possibility.' There also appears to be another contradiction here
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Post by principled on Sept 15, 2010 10:46:07 GMT 1
Hi STA Glad to see you're up and fighting already! Can I add another dimension to this thread, viz temperature. As the atom is cooled towards absolute zero, I assume that the average position of electron will move towards the nucleas such that the probability that it is in two places at once becomes zero at -273, is this correct?
Does the "space" occupied by both the nucleas and the electrons around it actually decrease in line with the shrikage observed when anything is cooled or is only a function of the lattice or other formation taken by the molecules when they are cooled? P
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Post by abacus9900 on Sept 15, 2010 12:26:36 GMT 1
Indeed, since how can you say, on the one hand, that only one instance of an electron appears when a measurement takes place, yet maintain that you are able to measure many instances of an electron simultaneously? Contradiction here, it seems.
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Post by speakertoanimals on Sept 15, 2010 12:50:01 GMT 1
Hi STA Glad to see you're up and fighting already! Can I add another dimension to this thread, viz temperature. As the atom is cooled towards absolute zero, I assume that the average position of electron will move towards the nucleas such that the probability that it is in two places at once becomes zero at -273, is this correct? Nope. The electron (let's take just one) in an atom can only occupy a discrete energy level, and the ground state level is what it is, lowering the temperature doesn't alter that. All that happens at higher temperatures is that some electrons will be in excited states just from thermla energy alone. Okay, so take a sample where all electrons are in the ground state, they can go no lowr, and they are still spread out. What about the atoms themselves? They interact with each other, hence you have the quantum states of each of these. Exactly what happens next depends on whether the atroms have integer spin (bosons), or half-interger (fermions). If they are bosons, they can all occupt the lowest possible quantum state (which still isn't zero energy). when they do that trick, that is Bose-Einstein condensation. The particular properties of bosons explains things such as why helium does such odd stuff at low temperatures. For fermions, they can't all move into lowest energy state, since identical fermions cannot occupy the SAME state. Hence a gas of fermions does different things as the temperature is lowered, where atoms lie in higher energy states because there is no room in lower ones.
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Post by speakertoanimals on Sept 15, 2010 12:59:30 GMT 1
Please stop quoting and misunderstanding the Feynman quote! It doesn't mean what you think it means.............
I think it is not my english that is incoherent, just that the ideas in quantum theory don't agree with our normal english usage. You keep complaining that you cannot understand, yet you don't seem to be trying very hard to do what needs to be done -- to DITCH your classical ideas as to what is possible or not, and to go beyond them.
Until you can do that, you'll never understand why in quantum terms, a statementy such an as electron can be in two places at once can make sense, yet at the same time, it is not totally in either.
The contradiction is not in the quantum theory, but in the everyday, classical concepts underlying the conventional use of language, which is why trying to state it in ordinary english leads to seeming contradictions until you can make that step, and ditch your preconceptions. That is what Feynman meant, not some sort of wishy-washy quantum is hard, or quantum theory is nonsensical that many people seem to think it means.
If you can't, no point in continuing further.
It is just not intuitive, that is all, but so is so much of what is worth learning. You have to be able to get beyind your intuition as the sole arbiter of sense, and many can't or won't, or even admit that anything can make sense beyond that.
As to abacus, this electron only a possibility until measured is absolute nonsense, and the usual misunderstanding of quantum theory. But since you haven't listened to any of my previous attempts at explanation, I don't expect you to listen to this one either.............
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