Timeline for Common false beliefs in Physics
Current License: CC BY-SA 2.5
38 events
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| Dec 14, 2010 at 20:57 | history | edited | Vagelford | CC BY-SA 2.5 |
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| Dec 5, 2010 at 10:54 | comment | added | Marek | @Vagelford, all right then. By the way, if you really formulated the question such that it is clear that you are talking about the distinction between pure QM and interpretations, I would give you an up-vote. But as it stands it is really confusing (at least for me; and I suppose it must be even more so for someone who doesn't know about interpretations). | |
| Dec 4, 2010 at 22:10 | comment | added | Vagelford | Marek, we obviously agree on that. | |
| Dec 4, 2010 at 22:01 | comment | added | Marek | @Vagelford: I agree that the two should be clearly separated. QM can be studied at great length purely on its own as a mathematical theory. But this is not the way it is usually taught. Copenhagen is usually assumed and people are often left to wonder about the nature of measurement and other connections with physics without ever being told about interpretations. | |
| Dec 4, 2010 at 21:46 | comment | added | Vagelford | Teaching or communicating of quantum mechanics in general. | |
| Dec 4, 2010 at 21:44 | comment | added | Vagelford | I should say that I also think that interpretation is what is described in the wikipedia article. I think my answer makes exactly that distinction between QM and interpretation and essentially points out the fact that there is a preferred style in the teaching of QM that promotes one or some interpretations. I find no reason why that should happen and I think I am not the only one, as one can see in the videos. | |
| Dec 4, 2010 at 21:40 | comment | added | Sklivvz | @Marek, I agree. | |
| Dec 4, 2010 at 21:01 | comment | added | Marek | @Sklivvz, all right let it be :-) Anyway, this is why I think Vagelford's answer is not good. It's just about interpretation (of interpretation) :-) | |
| Dec 4, 2010 at 20:56 | comment | added | Sklivvz | @Marek, I was referring to the same... but do not want to re-start the argument (<-intended in a good sense) :-) | |
| Dec 4, 2010 at 20:53 | comment | added | Marek | @Sklivvz, well I don't like arguments but for some reason I always tend to get caught up in them :-) Okay, we can agree to disagree. But just that you know, this is my definition of interpretation of QM and it is pretty standard. If you are talking about something else you should let people know and not confuse them with non-standard terminology ;-) | |
| Dec 4, 2010 at 20:50 | comment | added | Sklivvz | @Marek, I see you like arguments as much as I do. I believe we merely disagree on what constitues an interpretation. I do not think mine is an interpretation, but you do. With my definition I am right and with yours you are right. As such, let's agree to disagree :-) | |
| Dec 4, 2010 at 20:30 | comment | added | Marek | @Sklivvz: not true. Some interpretations are better than the others in the same sense that QM is better than classical mechanics. E.g. Copenhagen doesn't tell you anything about measurement but other interpretations do (and they also tell you why Copenhagen works in most cases). And saying that interpretations are not scientific is just plain wrong. You can surely propose interpretation of QM that will not agree with observations and such an interpretation would be falsified. Anyway, you do need an interpretation to use QM (even if it is just yours shut up and calculate approach). | |
| Dec 4, 2010 at 20:24 | comment | added | Sklivvz | @Marek, seriously - I understand the measurement problem and the different interpretations of QM. Point in question: it is a fact that (as far as I know) any interpretation is equally (in)valid. In other words, the current interpretations are not falsifiable, and hence, they are not scientific. | |
| Dec 4, 2010 at 19:36 | comment | added | Marek | @Sklivvz: I see you don't care but ignoring a problem doesn't make it disappear ;-) If you want a full correct description of the world then you have to also describe your apparatus by QM. It's not possible to separate it in some cases (e.g. in quantum cosmology). This is why people started to ask questions about measurement and interpretations and found that non-trivial problems where hidden there and new mathematical theories (like decoherence and consistent histories) were born. Of course you can ignore this for basic calculations but you should at least know that you are ignorant ;-) | |
| Dec 4, 2010 at 17:47 | comment | added | Sklivvz | @Marek, I don't know/care what a measurement is, but clearly I know what the result of an experiment is. It could be a photographic film, for example, with some particular patterns left by particles. That is what needs explaining, in my opinion, and that is what QM does. QM is problematic mostly for its terminology, as typically it borrows concepts from the classical world by similarity. But one can simply think of it as a mathematical algorithm. If it is more than that, then there should be only one single valid interpretation, provable by experiment. | |
| Dec 4, 2010 at 17:23 | comment | added | Marek | @Sklivvz: even if you are denying it, you are still working in some interpretation. QM on its own is just a mathematical theory. To connect it with physics interpretation is absolutely necessary. For example, what do you think measurement is? Think about it and you'll soon discover that you yourself are using some interpretation or other (although just implicitly). | |
| Dec 4, 2010 at 17:19 | comment | added | Marek | @Vagelford: I think it is an interpretation. So you have chosen an interpretation yourself (one where you're not allowed to ask). So why do you prefer this one among all the others? I am not saying that it is a problem, just that it is arbitrary. And as you say, it doesn't really matter for the actual physics. So I am not really sure why we are still discussing this. | |
| Dec 4, 2010 at 17:17 | comment | added | Sklivvz | @Marek: mine is not an interpretation, it is merely a description of what the experiments record. As such, any interpretation must be consistent with my description (and with the experiments). My point is that given this necessary condition, all interpretations are physically unprovable (for now) and as such are completely subjective. Unless you have an interpretation which is subject to proof and can be actually disproved by experiment, it's not physics. It's epistemology. | |
| Dec 4, 2010 at 16:53 | comment | added | Vagelford | @Marek: I don't think that saying that QM doesn't say the one thing about the other thing is an interpretation. On the other hand if you choose to say that the particle goes through both slits, then you choose one or some of the many interpretations with no physical grounds, since there is no preferred interpretation. Moreover some of the various interpretations have conflicting views on some issues. So, why prefare one against the other? | |
| Dec 4, 2010 at 16:12 | comment | added | Marek | @Sklivvz: but you are implicitly using one such interpretation yourself. Namely, one that tells you that it's unphysical to ask anything except measurements. You have arbitrarily chosen to make measurement the basis of what is physical (and seems you are not even aware of it). The point is, I can take another interpretation, one that tells me where the electrons went and it also perfectly reproduces all the measurements, so there is no problem with it. It's as valid (and physical) an interpretation as yours is ;-) | |
| Dec 3, 2010 at 21:44 | comment | added | Vagelford | Well, that's my point. | |
| Dec 3, 2010 at 21:16 | comment | added | Sklivvz | Sorry to step in abruptly, but QM does not tell us ANYTHING about the path of the electron. The ONLY objective, measurable and sustainable thing that QM tells us is the OUTCOME of the MEASUREMENTS. I.e. that electrons will hit the screen in some pattern. All the rest is (non-physical) interpretation and subjective. | |
| Dec 3, 2010 at 9:26 | comment | added | Marek | @Vagelford: it happens in context of some interpretation of QM and if the interpretation itself is consistent you can safely say that it really did happen in QM itself. Nobody can ever prove you wrong. But this is more like philosophy. | |
| Dec 1, 2010 at 16:47 | comment | added | Vagelford | But it is a misconception. What would you call a claim that something happens in the context of QM when that something isn't in QM? | |
| Dec 1, 2010 at 16:10 | comment | added | Marek | @Vagelford: well, yeah. But I wouldn't call that a misconception. The idea can be made correct just by using correct interpretation. So it doesn't matter whether you think the electron goes through both slits or not. It's not wrong. Therefore I think your answer (although it has it merits in pointing out the danger) doesn't really belong here. | |
| Dec 1, 2010 at 14:37 | comment | added | Vagelford | Yes, but that is the point. It belongs to interpretation and not to "the actual physics" to say that it goes through both. It is a bad and dangerous idea to confuse the two, especially since there is no preferred interpretation. | |
| Dec 1, 2010 at 14:08 | comment | added | Marek | @Vagelford: okay, I think I understand you now. But you are just discussing interpretation of QM, not the actual physics. Sure, if you don't measure something it's hard to ask what happens (and some interpretations go as far as telling you that you are not allowed to ask). But you can choose an interpretation where you can say something even when you don't measure as long as it is consistent with measurements. This is called Consistent histories interpretation. | |
| Dec 1, 2010 at 13:42 | history | edited | Vagelford | CC BY-SA 2.5 |
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| Dec 1, 2010 at 13:03 | comment | added | Vagelford | You are reading something other than what I am saying. I didn't say that interference is statistics and I am not talking about hidden variables. I am saying that if we ask about the path (setup an experiment), then we see a path. If we don't ask, then the Schrödinger equation doesn't say it went through that, the other or both. The QM behaviour is in the dynamics (the equations of motion), not the kinematics (the path). It is in the fact that the description is made with a wavefunction from which you get only probabilities for events, even though the equations are fully deterministic. | |
| Dec 1, 2010 at 11:48 | comment | added | Marek | @Vagelford: I am pretty sure Feynman would agree with me. As to my conclusion, you just said it yourself: "in the end it is the effect of the many particles that give you the interference image". This is essentially the old flawed Einstein's statistical view of QM. If you assume that particle only went through one slit and the interference is just statistics then obviously some kind of hidden parameter theory would be required. But we know there is no such thing by Bell inequalities. Or maybe you are saying that we are not allowed to ask about the path. But that is just interpretation of QM. | |
| Dec 1, 2010 at 8:33 | comment | added | Vagelford | I don't see how you get to that conclusion from what I am writing. The quantum effects of course are there from the starts, but they are there in the equations of motion. My point is that QM doesn't state that "it goes through both slits". I also don't think that Feynman would agree that the path integral approach implies that a particle follows all the paths. It only states that each path has a probability and a particle actually follows only one. In the end it is the effect of the many particles that give you the interference image. You can't infere interference from one particle. | |
| Dec 1, 2010 at 0:08 | comment | added | Marek | It seems to me like you are trying to propose ancient preconceptions (like the ones Einstein had) that quantum effects appear just as statistics after letting many electrons through the slits. Well, this is obviously not the case. Every single electron behaves quantum mechanically and travels through all the paths (in path integral view) or is a wave that passes through both slits (in Schroedingerian view). | |
| Dec 1, 2010 at 0:04 | comment | added | Marek | Very strange answer. Actually, it only depends on interpretation whether you think that electron passes through both slits. So this means that it is not a misconception at all. Actually, the most attractive interpretation to me (Feynman's path integral) tells you that the electron travels through all paths and all of them are equally important in determining the final amplitude. In particular, the paths through left and right slits interfere. | |
| Nov 26, 2010 at 21:47 | history | made wiki | Post Made Community Wiki by Robert Cartaino | ||
| Nov 20, 2010 at 15:43 | history | edited | Vagelford | CC BY-SA 2.5 |
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| Nov 20, 2010 at 10:22 | comment | added | Vagelford | Ok, that sounds like a "no it isn't" argument. QM gives you a framework where the equations of motion of a particle (for example Schrödinger’s equation) are the ones that "have wave-like" properties and because of them you get the wave-like behaviour of interference. QM doesn’t say anything about what the particle “actually” does. In order to see what the particle does, you would have to perform a measurement. Anything else belongs to the realm of “QM Interpretation” where there are several interpretations and there are some silly things going on with some of them. | |
| Nov 20, 2010 at 9:56 | comment | added | Piotr Migdal | Actually, what you said is not true. First, electron go through both slits at once (if you want to say something contrary, it's much more about taste or interpretation, that 'fighting with a false belief'). Second, while properties of a single photon are interesting, I would not say it does not behave like a wave (it certainly have many wave-like properties). | |
| Nov 19, 2010 at 11:53 | history | answered | Vagelford | CC BY-SA 2.5 |