Difference between revisions of "Talk:Quantum mechanics"

Revision as of 14:14, May 14, 2011

Wave Function

I edited the Collapse of the Wave Function segment. I found it offensively wrong in many respects. I understand there is a need to make certain things "accessible" to people. However there is more of a need to present truthful information regardless of its accessibility. I do not post anything that I could not back up with sources. If you feel the need to change what I say make sure that you know what you're talking about because as it stands right now the "corrected" version of the segment has almost no value of worth. The explanation of a wave function ONLY occurs in a special example. I decided to take a look at this website after seeing it aired on the "Colbert Report" and am offended at the lack of some information, and the bastardization of what was once truthful information. Honestly you should not even begin to think to alter this page if you have not taken a course in Quantum that was taught by a PhD. in the field. Swifty

Hello, and thanks for joining! I actually have taken a short course in quantum mechanics last year, but I very well might be remembering it wrongly. Could you please explain what part of my last edit is wrong? I was trying to restore the specific analysis of what the position function is, and the consequence: that there's a nonzero chance the particle can jump across the room or the universe.

And if you just think the organization can be improved, or there's more stuff we need to talk about, I agree with you wholeheartedly. I came to this website a month and a half ago myself, and I'm still shocked by how much ground we still have to cover. Please help us improve! --EvanW 18:01, 9 December 2009 (EST)

No problem. To start with you said that the particles move randomly. We don't know that. Part of current debate in quantum is whether the theory we have no complete or not. As you can imagine it isn't easily accepted that we "just can't know" the position of the particle so many people claim that as of now, quantum is incomplete. If this is so then it might not be that particles move randomly, they just move in a way we cannot explain. This mistake isn't so much an error in knowledge as much as it is too bold of a statement to make.

In your next sentence, its not that the position isn't described as a point, but that it is meaningless to say it as such. This is an important distinction to make. If it just isn't described that way but has meaning, then it COULD be described that way but for reasons unknown to the reader, it isn't. If it is a meaningless value then there is no point in talking about it as such. It is imperative to explain why things are the way they and not just say "oh well its not done that way" WHY IS IT SO? (most important thing you can ask yourself as you write your thesis)

I don't have much of a problem with your description of the wave function presented, I feel it would be much more useful to talk about the particle in a box problem as it is a good introductory point for the subject.

I don't really like the way you say "jumps". In my mind it implies that "it was here but now its way over there". All this wave function is telling you is that if you look everywhere you will find the particle.

The wave function is a prediction of averages. In other words, (disregarding collapsing) if you measured the particle's position an infinite number of times, you would find that 99% of the time it would be in that two angstrom range while the other 1 percent of the time its elsewhere. The particle doesn't "jump" it just wasn't where you would have expected to find it.

The collapsing of the wave function is a consequence of measurement, not the reason for it. It mearly says, if you measure it then you know about where the particle is, so if you measured it again immediately it would be around that location. Once again it doesn't "jump" away on its own. In fact if you continuously measure the particle with very little time between measurements the wave function will stay collapsed as long as you're measuring.

Your final statement is a bit redundant and a little not true. I explained why the wave function collapses. However saying how it will collapse before measurement is about the same as saying "the particle is right here" its meaningless.

Keep in mind that I am a little flustered about all of this because I came from the page on magnetism where they described it as "a component of the electromagnetic force". While a lot of what you said wasn't "wrong" it also wasn't true.

Thanks for explaining all this. Thanks for reminding me about the difference between "random" and "currently inexplicable", and "we don't do it" v. "it's meaningless," and for explaining about the wavefunction staying collapsed if you measure a short while afterward - I hadn't heard that last point before. I just edited the page to clarify some of what you said and add the example of the particle in a finite box; I'd rather not put it in an infinite box myself as I don't quite remember the math. If you'd like to do that, I'd greatly appreciate it!

But I don't think your wording that "predicting how and where the wave function will collapse is a meaningless endeavor," is quite accurate. Isn't that the same as "it might not be that particles move randomly, they just move in a way we cannot explain"?

(By the way, you can automatically sign your posts with four tildas (~~~~), and indent with a colon at the start of the line.) --EvanW 18:44, 9 December 2009 (EST)

I don't think there is much of a reason behind predicting the collapse of a wave function or discussing it. Like I said the collapse of a wave function is a consequence of measurement and as we know measurement changes what we're measuring. So in a way the collapse of a wave function only occurs when you are no longer looking at what you wanted to look at. (I wish there was a better way to say that). BTW thanks for the tilda thing I was trying to figure that out. Swifty 19:05, 9 December 2009 (EST)

Side note, the problem you have presented is not a finite box as the wave function does not look like that for a finite box. The math for a finite box is much more complicated than that for the infinite box. I think you are confusing finite and inifinte with the length of the box instead of the depth of the box. The idea with the infinite box is that there is an infinite potential (or walls) at the side of the box while with the finite box does not have an infinite potential (looks like a well). The problem you seem to have posted is a free particle which is still a difficult problem. Swifty 19:16, 9 December 2009 (EST)

I would also strongly recommend against talking about tunneling without talking about the math behind it. As it stands now your introduction to tunneling is confusing. Swifty 19:17, 9 December 2009 (EST)

Myself, I think it's better to explain or mention the consequences of math (e.g. tunneling) without the math itself than to not mention them at all. But, of course, it's better to have both. By all means, when you've got the time, please add the math! --EvanW 19:24, 9 December 2009 (EST)

Explanation of tunneling can only come about after the explanation of the problem. I read your user page and understand what you're trying to do. But you have to accept the responsibility that in order to present knowledge you have to present why it is. Why is tunneling allowed, how is it realized? These are things that you have to answer if you want it up there. Myself I feel compelled to let the truth about things be known. I have a growing concern after visiting pages on this site that people are making up wildly outrageous claims that don't seem to be trolls. For example on your nuclear fusion site someone said "stars are stable". Your(the site's not your personally I kinda like you) entire page on nuclear power is either erroneous or just unnecessary. You seem to have an interest in keeping together the scientific pages. If this is the case I strongly urge you to post math, reason, experiments. How is it we know a wave function is correct? Think about it, if things aren't exactly in one particular position, why does the universe work? There are a lot of gaps in knowledge here that lead me to believe this is an mission of lunacy.

It is scientifically reckless to just present results. What you are doing is telling people to just believe what you say is true. If science were done in this fashion where would we be as a society? I could just say, "Hey cold things get colder for no reason, just believe me." If this was accepted it would violate the laws of thermodynamics. Claims need proof. Results need proof. Consequences of things need math. With every fiber of my being I believe you are doing your race a disservice by simply presenting quantum mechanics as something that should be accepted.(Make no mistake that is what is happening here).

I understand the idea that this site is a safe-haven from liberal bias, but without references, without proof, without any reason for its claims, this site is worthless. Try and see this from my perspective. You say that this is a "trustworthy encyclopedia" yet you post information. You also leave out information that you do not know about. This is a dangerous practice and it is morally and ethically wrong to say you are trustworthy without offering the full truth.

Honestly, with all that said I like you Evan.(anyone who has taken and not failed a course in quantum obviously has some intelligence)But if you are going to walk down the scientific path, you have to make sure that you are thorough and complete. Otherwise what you are saying is harmful. You may think that my concern is unfounded but I promise you, it is very very dangerous just presenting claims and having people believe them to be true.

Also on not of the math, I have absolutely no idea how to type it up, if you want me to send it to you in some other way so you can type it up (or better review your work on these problems) I would be more than happy to.

Sorry for the long windedness of this but the sharing of knowledge, while noble, is dangerous if not done properly. I simply fear that if we continue in this fashion, physics, all its laws and findings, will only be a field of debate rather than that of true science. Science is based on the principle that you must prove something for it to be true. I believe that this should hold true in the communication of scientific ideas. Swifty 20:10, 9 December 2009 (EST)

Older stuff

I have reinstated the change that had been made by Ssandoval, regarding the removal of "first order kinetics". It's true that he was an obvious vandal in other pages (yes, I looked around). It's also true that calling it an "idiotic implication" was excessive, and that his next "sentence" had no verb and contained a reference to a "negative amount" that I can't figure out. However, the chemical concept of "first order kinetics" isn't applicable here. Not idiotic, but wrong nonetheless. First order kinetics refers to a reaction rate per unit volume being proportional to the concentration of the reactants. In radioactivity the rate depends only on the amount of material. The exponential decay nevertheless follows.

Please look before reverting. CScience 14:25, 7 June 2007 (EDT)

I deleted the jargon comment, although I do agree that it is jargon, and the comment is duly noted. Again, I wish to emphasize that the subject of quantum mechanics is inherently a college-level subject, and the language I used should be accessible to a student with a college level understanding of calculus and linear algebra. --Mathoreilly 22:10, 1 July 2008 (EDT)

Let's not undo things hastily without discussing them first. There were some good things there. Why do you want to remove them?--Lemonpeel 15:00, 8 July 2008 (EDT)

I left an edit comment. --Ed Poor ^Talk 15:29, 8 July 2008 (EDT)

I'm no genius, but it all made sense to me....JPohl 15:46, 8 July 2008 (EDT)

The postulates section could maybe have some preface or qualifying sentences to make it a bit easier for people without a background in physics to understand, but I could understand the article just fine as it was. Even Richard Feynman said that nobody truly understood quantum mechanics; however just because a concept is confusing, counterintuitive, or requires some previous knowledge to be explained, does not mean it should removed or simplified. Fantasia 16:18, 8 July 2008 (EDT)

I must take issue with the sentence: as a result of the wave nature of an electron, the position of the electron can never precisely be known. First of all, the more correct statement is that the position and momentum of an electron can never both be known with arbitrary precision. And this has nothing to do with the fact that an electron behaves like a wave. Rather, it results from the fact that the position and momentum operators do not commute with each other. For an example at the other end of the spectrum, the energy and spin-z operators DO commute with each other, and for this reason one can indeed simultaneously know the energy and spin of an electron.--Lemonpeel 19:52, 19 August 2008 (EDT)

Yes, thank you for clarifying the point that the position and momentum of an electron can never both be known with arbitrary precision. This has been poorly stated in many places, and is really misleading. It's hard enough to understand physics; let's not make it any harder. --Ed Poor ^Talk 20:34, 19 August 2008 (EDT)

Hi, I'm new here, so I apologize if I'm doing this incorrectly. Should I propose edits on the talk page and then make them on the main page? There are some things stated on this subject on the front page that are incorrect (although not completely wrong), and I would like to correct that. I'm hoping to eventually help out in other subjects here, but for now will contribute to what I know best.

My first edit would be on the uncertainty position - it states that position and velocity can not both be simultaneously known to within arbitrary position. The current statement is about velocity only. For applications of quantum mechanics, I think we should talk about more than just radioactive decay - I would like to add a link on transistors, as they seem a far more relevant application of QM in people's daily lives. Also, radioactive decay is often thrown about in a cartoonish way without fully understanding it - which is why things like carbon dating done by evolutionists are so blindly accepted by the public, when the science to make a real measurement is actually quite complicated. --CGriswald 12:51, 13 December 2008 (EST)

After a year, this page remains woefully incomplete. Perhaps discrediting the theory of relativity is a greater priority for the physics contributions at Conservapedia. To add a little actual content to this page, someone should write sections on the following topics: (1) The photo-electric effect. (2) The classical vs quantum understanding of black-body radiation. (3) The double-slit experiment. (4) The Stern-Gerlach experiment.--Lemonpeel 20:19, 25 May 2009 (EDT)

I added a section about the fundamental principles of quantum mechanics. It is very difficult to express them without mathematics and with a minimum of specialized language, but I did my best. --Quetzalcoatl 23:12, 13 August 2009 (EDT)

Quantum mechanics and God

It occurred to me during a discussion that God's omniscience has some interesting implications when discussing quantum mechanics. The question being discussed had to do with Calvinism, and with whether God's omniscience invariably leads to predestined salvation.

Schrodinger's thought experiment popped immediately into my mind, and it occurred to me that, if the Copenhagen interpretation is accurate, God's omniscience makes Schrodinger's Cat an impossibility: the superposition of states cannot be unresolved, and the waveform cannot be uncollapsed, because there is an omnipresent observer.

This would actually be in keeping with Schrodinger's views; he did not, after all, believe that it was possible for a cat to be both alive and dead at the same time. Schrodinger's Cat was an effort to point out the absurdity that results from a strict acceptance of the Copenhagen Interpretation. He pointed this out in an exchange with Einstein, saying that one "cannot get around the assumption of reality"--that is, reality must have a definite state, even if that state is (as of yet) undetermined.

It occurs to me that the acceptance of an omniscient observer resolves a great many paradoxes associated with quantum mechanics, and lends credence to the relational interpretation--in which scenario the waveform would appear uncollapsed to us, while God would observe it as collapsed. It would also suggest that objective collapse theory is a misinterpretation; collapse DOES occur irrespective of our observations, but not irrespective of ANY observation. The ENVIRONMENT does not observe the cat; the CREATOR of the environment observes the cat (or the particle)--and, in so doing, collapses the waveform and resolves the superposition.

However, I will admit that my understanding of these issues is a layman's, and not thorough. I know there are other contributors here with a much deeper understanding of quantum mechanics, and perhaps they can correct any misperceptions and misunderstandings in my above scenario.