DrChinese said:Here is one I got from a PhysicsForums thread:
http://www.iop.org/EJ/abstract/1402-4896/1988/T22/016/
"From the close agreement of experimental and theoretical g-values a new, 10^4 × smaller, value for the electron radius, Rg < 10^-20 cm, may be extracted...
DrChinese said:So I guess you would need to explain how a wave can go through both slits of a double slit apparatus (i.e. a much larger separation) and still be confined to a very small point-like volume at other times.
Well, for correctness, I think you should mention the fact that, however, you need a quantum mechanical description, so you cannot avoid using wavefunctions (= also wave description).twofish-quant said:It's actually quite fun. You have throw two electrons at each other, and see how they bounce of each other, and they behave exactly like two point particles interacting with each other.
lightarrow said:Well, for correctness, I think you should mention the fact that, however, you need a quantum mechanical description, so you cannot avoid using wavefunctions (= also wave description).
conway said:I don't believe this answers my question. I asked how we supposedly know that an electron can be confined to an arbitrarily small volume. You have given me a reference for the experimentally determined electron radius. I really can't make the connection.
zenith8 said:Because there is a wave and an accompanying particle, rather than one thing which is somehow both. I mean, is this just too simple or something?
DrChinese said:A vanishingly small radius is clearly incompatible with your wave-only description (and it should be obvious why). I expect you'll have another non sequitur for that. (Maybe next time you could make it funny too, as this has become otherwise tiring.)
eoghan said:Wow... this discussion is very interesting! But I'd like to change my original question:
Why should I think the electron is a wave?
I know from the double slit experiment that an electron couldn't be described as a wave (each electron hits a point of the detector) nor as a particle (after a lot of electrons fired, I get a diffraction shape).
But I think, as Zenith8 said, that the experiment could be explained considering the electron as a particle which trajectory is determined by a wave. I don't understand: why I have to think that every electron is a wave?
Isn't simpler to think that the bodies are particles but they don't move in straight directions, but according to their wave (where the wave is something associated but separated from the body)?
DrChinese said:A vanishingly small radius is clearly incompatible with your wave-only description (and it should be obvious why). I expect you'll have another non sequitur for that. (Maybe next time you could make it funny too, as this has become otherwise tiring.)
zenith8 said:Hi Eoghan,
Welcome to the world of de Broglie-Bohm theory - come on in, the water's lovely..
Basically, no-one will dare to agree with you - they think that if it were that simple, someone ought to have noticed sometime over the last 80 years. And they're right, they ought to have. But, astonishingly, they didn't.
That's the power of charisma - well done Bohr and Feynman. 'Nobody understands quantum mechanics..', remember? Well, it's their choice.
Z.
zenith8 said:Hi Eoghan,
Welcome to the world of de Broglie-Bohm theory - come on in, the water's lovely..
Basically, no-one will dare to agree with you - they think that if it were that simple, someone ought to have noticed sometime over the last 80 years. And they're right, they ought to have. But, astonishingly, they didn't.
That's the power of charisma - well done Bohr and Feynman. 'Nobody understands quantum mechanics..', remember? Well, it's their choice.
Z.
conway said:I have listed all the postings of mine so far in this thread. I looked up the meaning of "non-sequitur" in Wikipedia but I am unable to identify any in this list. Perhaps you could point them out.
-----------------------
8. I don't know what you mean by this.
27. I wonder if you can come up with a specific experimental scenario which illustrates this difficulty.
29. I thought you were going to give an example of how to confine an electron to a volume too small for a wave.
31. I don't think I've asked for anything else except for an explanation of how we supposedly know this.
34. I don't believe this answers my question. I asked how we supposedly know that an electron can be confined to an arbitrarily small volume. You have given me a reference for the experimentally determined electron radius. I really can't make the connection.
35. Just to keep this on track, the original statement by Dr. Chinese was to the effect that the position of an electron can be determined to arbitrary precision. I am still asking what this means and how we supposedly know it to be true.
38. Exactly. (In response to Lightarrow).
sokrates said:Dr. Chinese's point was very clear and elementary even from the beginning.
I am not sure whether you are really not understanding it; or you are pretending so as he gave clear experimental facts related to the point-like nature of electrons, as well as their wave-like properties.
Non-sequitur is Latin for "It does not follow" - and it relates to your replies, as you are stubbornly avoiding to address what has been nicely explained to you. (Ironically all your posts are not logically related to what's preceded by them , i.e, they are all non-sequitur)
sokrates said:...
The problem of de Broglie-Bohm is not that it's simple , the problem with it is it's stupendously naive... To get away from the probabilistic nature of things with a desire to make atomic world resemble the macroscopic world... It's a purely humane theory... It is understandable. It really is... It's like: Oh, I see why you want to think like that... It's the theory that a confounded beginner proposes in his 10th thread in Physics Forums yet, it is the same theory that has eluded the giants for 80 years... It has no connection with reality (tell me a table-top experiment that can detect the existing wave and the particle at the same time...) it is just the imagination at work ... A valiant attempt to solve the greatest mysteries of physics. Too bad nobody takes it seriously...
Beginners can easily buy into this fantasy, but there's not even a hint for the rest of the world to believe in it for two important reasons:
1.) There is NO experimental evidence to favor it AT ALL.
2.) It is an extraneous, and complicated idea (in terms of Occam)- and theorists know from hundreds of years' experience that 99.999% of the time, "simple" & "elegant" ideas work instead of complicated ones.
...
Mentz114 said:This is mostly inaccurate and based on ignorance. The predictions of BM are the same as 'standard' QM. It is a probabilistic theory so there's no trying 'To get away from the probabilistic nature of things'. It is not compicated at all to people who understand Hamilton and Jacobi's theory. It does not confuse beginners.
sokrates said:Dr. Chinese's point was very clear and elementary even from the beginning...he gave clear experimental facts related to the point-like nature of electrons, as well as their wave-like properties.
conway said:Is the position of an electron determined to arbitrary precision in the quantum eraser? I don't think so. But that's why I have to keep asking the same question over and over.
sokrates said:OK, I agree that I am ignorant when it comes to BB, now will you please give me a single experiment that favors BM over Copenhagen, even at the slightest sense??
Otherwise, I'll stick to my points.
Dmitry67 said:I see 2 fundamental problems with BM:
1. Laplace determinism: me, typing this post right now, must be pre-coded in the initial conditions at the Big Bang.
2. While it manages to be compatible with 'standard' QM, when used outside of that framework - say, Hawking/Unruh radiation, it fails because the observers disagree if particle is real or virtual in different frames. Demystifier had addresses that issue inventing 'dead particles', but for me it is a beginning of curve fitting.
Mentz114 said:The wave equation evolves deterministically in all quantum theories that have one. So they all require some intial conditions.
sokrates said:If you understood the quantum eraser experiment, or bothered to check the wikipedia article on quantum eraser when Dr.Chinese first brought it up, you'd see that "the position of an electron is determined to extreme precisions (that is possible by today's experimental apparati)" which is another way of saying that "electron behaves as a particle".
This is what I had understood previously, that it was an interpretation of QM, not a separate theory. But zenith8 disagrees:Mentz114 said:The predictions of BM are the same as 'standard' QM.
So which is correct? Does it make different experimentally testable predictions from standard QM (therefore being a different theory) or does it make the same experimentally testable predictions (therefore being a different interpretation).zenith8 said:De Broglie-Bohm is indeed a different theory; it is based on a different set of axioms to orthodox QM and it makes different predictions which in principle - though with great difficulty - could be observed (in the so-called quantum non-equilibrium case).
I would say this differently. I would say: "I know from the double slit experiment that an electron couldn't be described as a classical wave (each electron hits a point of the detector) nor as a classical particle (after a lot of electrons fired, I get a interference shape)." The answer is that they are quantum mechanical particles which have a single unified mathematical description in QM that predicts both features of the experiment that you have identified.eoghan said:I know from the double slit experiment that an electron couldn't be described as a wave (each electron hits a point of the detector) nor as a particle (after a lot of electrons fired, I get a diffraction shape).
My understanding is that deBroglie-Bohm is an interpretation of QM and makes the same predictions. Whether an experimental test exists to distinguish dBB and orthodox QM is an arguable point. People have looked for something in the hope of resolving this but there's no easy way to do it. dBB is based on the Schroedinger equation, after all.So which is correct? Does it make different experimentally testable predictions from standard QM (therefore being a different theory) or does it make the same experimentally testable predictions (therefore being a different interpretation).
Yes, understanding QM with purely classical analogies is doing things upside down. One of the strengths of QM ( any flavour you like ) is that classical mechanics is recovered as average behaviour in large ensembles. So QM is a 'bigger' theory than classical mechanics, even a replacement for CM.The answer is that they are quantum mechanical particles which have a single unified mathematical description in QM that predicts both features of the experiment that you have identified.
Dmitry67 said:I see 2 fundamental problems with BM:
1. Laplace determinism: me, typing this post right now, must be pre-coded in the initial conditions at the Big Bang.
2. While it manages to be compatible with 'standard' QM, when used outside of that framework - say, Hawking/Unruh radiation, it fails because the observers disagree if particle is real or virtual in different frames. Demystifier had addresses that issue inventing 'dead particles', but for me it is a beginning of curve fitting.