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pmb

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Posts posted by pmb

  1. Moderators are bound by the same forum rules as anyone else. Discussing moderation actions in the midst of a thread about walruses is off-topic; the best approach is to PM the moderator in question or report posts as needed.

    Thank you. That's all I was really asking anyway. Sometimes it seems that moderators don't always follow the rules. Sometimes they can say mean and hurtful things and then tell us we're childish for letting it effect our emotions. I find that quite irritating. Also it appears that the moderators frustrations come out in their moderation comments. I find that irriating. Normally that would't bother me. However life has really beaten me up. I've had one phsical maladay after another over the last 12 years. That's left me like an exposed nerve. I'm polite as possible nowadays so as to keep irritation down in my life because any of it can result in chest pains. I now feel better now that you've told us that moderators must also follow the rules. Thanks!! :)

  2. All of this mutual admiration and complaining is starting to make me ill. Starting your own forum would allow you to set up the rules you like.

    Acually that's the intention, someday at least.

     

    Considering this forum is free to you, the moderators work for free, the rules were set up in good faith in order to make the use of this forum enjoyable and educational for the majority, you might want to consider backing off a wee bit.

    You misunderstand the purpose of this thread. It's not about dumping on the moderators if that's whay you thought. Its about talking to the moderators about what goes on with moderators, i.e. what do they do. Do they hold thmselves up to the same standard as they hold us up to? etc. But please don't get me wrong. I love the moderators here. I really do. They do a wonderful job and I am now taking the opportunity to express that sentiment. Forums at other moderators can be real $##%@#@. Those moderators do what they please. I've gotten PMs from moderators where they were swearing at me, all over a misunderstanding too. Moderators here wouldn't swear at me in PMs. However they're not perfct either and its not a bad thing to talk to them about concerns that we have and questions we want to ask them. So there's no need to worry about it. :)

     

    Alternatively there is one action you can take which will guarantee you do not have to deal with the people here. I'm sure no one would object.

    I don't understand what you're talking about. I wouldn't leave just because the moderators are imperfect. That would be a wildley irrational thing to do.

  3. I know :)

     

    As I said before in my last thread, these are the ''Legal Strawmen''

     

    my thread has been closed pending review... very interesting. Leaving it open would have said far less.

    When anyone is under the spotight they may just remain quite so I wouldn't expect a response from the moderator. What the moderator doesn't acknowledge is that we too don't like being under the spotlight. They seem to ignore that fact.

  4. The off-topic comments are nonsense. I don't know these moderators personally, but obviously the talk about it being off-topic is rubbish.

     

    in my experience, someone proclaims off-topic posts even when it isn't, is topics they don't want to discuss.

    Yeah, I know. The purpose of this thread is to not leave that as a possible excuse. :)

  5. What is the rules? It sounds like you have came in here shaking your scepter because you did not like the subject. But it heavily falls within the rules, this is about the reputation system, if you haven't noticed... whether the name ''mod'' falls into it shouldn't count.

    I keep seeing the comment off topic commng up when people want to ask questions about moderator actions. For that reason I started a new thread Moderating a forum which can be found at

    http://www.scienceforums.net/topic/67597-moderating-a-forum/page__view__getnewpost

  6. In the other thread on the reputation system there are repeated coments by moderators who are saying that certain comments about moderation is off topic. The purpose of this thread is to breath life into that subject and as such to discuss everything about being a moderator such as whether the forum rules should be construed as applying to them.

     

    My opening question is therefore: Is it against the forum rules for a moderator to be rude to a member when they are operating in moderator mode? Are we allowed to disscuss moderation and moderator actions in threads?

  7. I just ordered a list of books. I was wondering if any of you folks are familiar with them and if so what do you think of them? The list is

     

    Quantum Mechanics by Ernest S. Abers

    http://www.amazon.com/gp/offer-listing/0131461001/ref=dp_olp_used?ie=UTF8&condition=used

     

    Quantum Mechanics by Eugen Merzbacher

    http://www.amazon.com/gp/offer-listing/0471596701/ref=tmm_hrd_used_olp_0?ie=UTF8&condition=used&qid=1341706304&sr=1-1

     

    Differential Forms and Connections by R.W.R. Darling

    http://www.amazon.com/Differential-Forms-Connections-R-Darling/dp/0521468000/ref=sr_1_1?s=books&ie=UTF8&qid=1324226113&sr=1-1

     

    Classical Mechanics by John R. Taylor

    http://www.amazon.com/Classical-Mechanics-John-R-Taylor/dp/189138922X/ref=sr_1_1?s=books&ie=UTF8&qid=1325953690&sr=1-1

     

    Analytical Mechanics for Relativity and Quantum Mechanics

    http://www.amazon.com/Analytical-Mechanics-Relativity-Quantum-Graduate/dp/0191001627/ref=sr_1_1?s=books&ie=UTF8&qid=1338846072&sr=1-1

     

    Nuclear Physics in a Nutshell by Carlos A. Bertualni

    http://www.amazon.com/Nuclear-Physics-Nutshell-Carlos-Bertulani/dp/0691125058/ref=sr_1_9?s=books&ie=UTF8&qid=1338738331&sr=1-9

     

    Any thoughts or comments? Thank you.

  8. Actually you need this both of these to substitute into your general solution if you want to discount say H (w) or G(w).

     

    There is nothing wrong with the constant function, even if the constant is zero

    I disagree. To me a function has to have a specific period to be periodioc. With the consant function there is no way to refer to a unique peiod. All real numbers are periods for the constant function. gto me that is not a periodic function. And since there is no way to dertermine whether there is motion or not then there is no wave either. Notice that for a wave there must be a way to measure the motion. If all the constant funcion does is to be unchaning in space and time then there is no way to track such motion.

     

    G(x-vt) = 0 for all x is perfectly OK (and twice differentiable)

     

    You are correct about the tan function and the reciprocal of the tan.

     

    The last one is, of course, a square wave if w is integral.

    Is this a wave or not in your eyes?

    I prefer to say that its function in my eyes if and only if it fits the definition. I don't like to work under how I precieve things but only to whether they fit the definition and the dsquare wave doesn't fit the definition. I will admit that it "feels" like a wave though.

  9. Bolded mine. This is not true. We sometimes add a small bit at the end of a mod note asking members not to respond in thread, but instead to use the PM or the report feature. The reason for this is simply because responding in thread can massively derail it from the OP, which os obviously not something we want to have happen.

    I disagree. Moderators tell me that the reason why they modedrate in opern forum, as opposed to PM, is because the alleged infraction happened in open forum. That's fine. But if the moderator is snippy in open forum then we too should be able to respond in open forum for the same reason. When a moderator snipes at a member it makes them not only look bad but causes negative emotions to emerge. This happens, to a large extent I imagine, because its has the feel of public ridicule. Satisfaction can't really be obtained until the people who reads the moderation can also read the members defense of it. We're not all cold stones with no feelings and emtions. We can get hurt just like anybody. be hurt pubicly can't be cured with private conversation for the fact that it was public ridicule. Comments such as exagerations llike

     

    ".. we are not here to serve your every whim"

    ".. back-seat moderating is not appropriate"

     

    don't belong in a moderators comment. It's an exgeration because (1) nobody assumed that our whims should be paid attention to or even acknowledged and (2) it speaks of something as if its a recouring theme rather than a question for lack of not knowing another way to approach the subject. I was irritated by that remark and I don't need to be irritated since it causes chest pains.

     

    In any case, there's just no call for moderators being snippity. They too should follow the forum rules when posting a moderation comment.

  10. Bare feet squeak on kitchen floor.

    Running tap roars out at me.

    The kettle seems it will explode

    As I prepare our pre-rise tea.,

     

    I enter little private room,

    Intend to have a quiet pee.

    No matter how good is my aim

    The porcelain rings back at me.

     

    From today my world has changed.

    How have these changes all been made?

    Yesterday I went to get

    A brand new toy, a hearing aid.

    LOL!! Nice! :lol:

  11. What's the point of pouncing on anyone... There is a reputation system for that.

    I quite agree. Moderators really shouldn't use the moderator function to be rude to members, even when they have a legitimate point to make. Its just not call for it. And when they're rude they add or we're supposed to assume, that we can't respond to defend ourselves. This only happens with a couple of the moderators. Most of them are very kind in their responses. CaptainPanic deserves an accomadation for the way he moderates. The other moderators should take him as guiding post.

     

    I hate this reputation system, it'snot justified in the slightest. If you have something to say about someones post, the reputation system is for the shy guys who can't challenge what someone says.

    What I'm always cautious about is people using it in to get even with pepple that they have a grudge with.

  12. Very valid point! "Why is there a reputation system?" Is very different to "What is wrong with the present reputation system?" or "How could the present reputation system be improved?" or "How do people misuse the present reputation system?"

    Any of the last three questions could be the subject of a new topic - except they seem to have had a good airing here!

    I think that being literal isn't always the way to go. As you reminded us, the question was Why is there a reputation system? To me that doesn't mean that we shouldn't talk about how and/or why we use it or what we do in spite of neg reps. On that point I have to admit that I never used to like it. Probably because I was in the negative. SInce I tool notice of that I decided to remain very polite even under the worst circumstances. Sometimes when you disagree with someone it doesn't appear to come off as being polite though. Espeiallyh when emotions are running high. In this course I found that I was able to make a lot of friends. That meant being patient, never telling someone that they're just plain wrong unless absolutely required and tying to be civil when I'm being dumped upon. I believe that it was a result of this new found patience that I saw my reputation go from negative to positive. And I have to admnit, it feels good. Its helped me determine where people are comming from and what they find useful. And when see neg reps I know what not to do in the future.

  13. pmb

    Sorry that was my fault for not using x as the dummy variable.

     

    Replace x by w, with w=(x-vt)

    In that case, noe of them are waves. G = 0 or G = constant since there is no way to make that substitution. The other functions aren't continuous so they don't satisy the wave-equations continuity condition.

     

    Further the choice of arbitrary funtion is not unlimited, they are at least bounded continuous functions, at least twice differentiable.

    Ah! Smart man! Way t go there laddy! :P

     

    I added my remark because, just as many forget the boundary conditions limit the choice of solution function as above, many treat the quantum mechanics of real matter as though it was just an assemblage of particles.

    And you think that's wong? Why?

     

    This, of course, is not the case. As soon as you go to molecules you loose the identity of each particle and create a new structure. When you get as far as metals and semiconductors even more happens and you get effects that are impossible for single isolated particles.

    That's correct. What you have then is a system of particles.

     

    So tan (w) is disallowed because, although periodic, it regularly goes off to infinity.

    That's correct. Thanks for pointing that out to me. I just learned somethning new! Thanks! :)

  14. "Just live without knowing whether something was done or not" is the correct answer.

     

    You were "pounced on" because your post was entirely off-topic and therefore inappropriate. Attributing the response to "short tempered moderators" misses the mark: it wasn't due to temper and it wasn't done on a whim. It's an unfair potshot, and also by laying blame at a moderator's feet it implies that you don't take responsibility for having crossed the line.

    That's quite an invalid accusation.

     

    In the first place the post wasn't off topic. It was a last ditch effort to attempt to keep the topic free from misconceptions and the continuing use of a straw argument, i.e. a non-cogent argument. There is was no call for your false accusation that my post was off topic since attempting to keep the thread free from misconceptions, i.e. bad-science free, is considered to be part of the topic. People were getting quite confused in that thread because of the misconceptions in it.

     

    In the second place, there's no excuse for moderators being rude simply because I asked a question. Nobody should ever fear of asking a question. There's just no call for it. Moderators can get their point across just just fine without it. Claiming that they need to be irritating ios, to me, just snobbery. While I understand that moderators are people too it doesn't mean that have to be rude in the form of a moderator comment.

     

    In the third place I never said I didn't accept responsibility for my actions. In fact in my next post, post #131, I explicitly said Sorry. My mistake. That clearly means that I took responsibiliy for my actions.

  15. Uh... yes you can.

    You're right. I know that in general relativity one tends to use God's unts.

     

    If M and m have units of klilogams [kg] and r has units of meters [m] then

     

    Mm/r2 has units of [kg]2[m]-2 which isn't the units of force, which is Newons [N] = [kg][m]-2 which is wrong, as is the magnitude.

     

    What one needs to do is to change the units of distance and mass according to Plnak's units

    See http://en.wikipedia.org/wiki/Planck_units

     

    I find those units cumbersome. I prefer to use in MKS units so I can easily compute values of the gravitational force.

  16. It's not really necessary. It just makes the units come out right.

    As juan noted, it also adjusts the value of the strength of the gravitational field

     

    And that way is to consider the value of G to be a constant of proportionallity between active gravitational mass and inertial mass.

    If a body A exerts a force on body B then its the active gravitational mass which is acting by A and its the passive gravitational mass that is being acted on B. Therefore we let

     

    M = active gravitational mass of body A

    m = passive gravitational mass of bdy B

     

    The force on B due to A is then F = GMm/r2

     

    The gravitational constant G then determines the strength of the force. M and m are found to be equal to the inertial mass of body A and B respectively.

  17. So would you call any of these a wave?

     

    G = 0

     

    G = constant

     

    G = tan(x)

     

    G = 1/tan(x)

     

    G = {1 : x odd, :x : even}

    No. None of them are functions of "x - vt"

     

    I fully agree with this but there is more.

     

    All this quantum mechanics stuff that has been mentioned so far has been single isolated particle stuff.

    That's because its the topic of conversation.

  18. Pete,

     

    Thank you for discussing properly.

    Always a pleasure! :)

     

    What restrictions would you place on G or H ?

    There are none that I know of except for physical meaning restrictions. For example: If G was a wave which was expanding out from the origin then it'd have the general form G(r - vt). The function H(r + vt) represents a wave converging on the origin and must be ruled out for physical reasons.

     

    The expression G(r - vt) might also be of the form f(r - vt)/r which would be a potential wave decreasing in magnitude as it expanded out from the origin.

     

    I think I understand why juan is so confused. He seems to think that the wave-particle duality states that a sinlge particle is a wave, which is clearly not true. As we have all agreed, a single particle has an associated wavelength and an associated wavefunction. If the wave-particle duality really meant that a single particle is a wave then it'd be called the wave-particle identity which it's not, and for good reason.

     

    However, as we all well know, with each particle there is an associated wave [math]\psi[/math], called the probability amplitude or simply amplitude, whose modulus squared [math]|\psi(x)|^ 2[/math] gives the probability density of finding the particle at x.

     

    It's for these reasons that physicists ascribes a single particle with a wavefunction.

  19. I'd like to add that it an be difficult asking for assistance. We can always hit the report button but it'd be nice to lknow if it was rejected or just not yet decided on. And there's no mechanism to find out. It'd be nice to know when we're being heard as compared to being ignored. What are we supposed to do in that instance? Just live without knowing whether something was done or not? For lack of knowing how to deal with it I mentioned it in open forum whereupon I was pounced on in in irritating manner. We should never be chastised for asking questions or making recomendations. Life's too short for short tempered moderators.

  20. However, if you mean that an individual quantum particle has wave properties or is a wave (some posters here said that an electron is sometimes a wave). No.

     

    3) Yes.

    You sure are beating that straw to death. We keep telling you that for a collection of particles to disoplay wave properties each individual particle must have an associated wave-characteristic. That's why a free electron with momentum p has wavelenth L = h/p. That is the wave-particle duality, and that's what we're talking about and what you keep ignoring.

     

    We know you're ignoring it because you can't procve that its wrong. Since you refuse to argue cogently immortal and I am now done with you.

  21. Pete,

     

    I said periodicity is fundamental to wave behaviour and have pointed out some uses of the word periodic that do not conform to your 'definition'.

    Brillouin zones are periodic in space. The periodic table is periodic in atomic number.

    studiot,

     

    I think that our disagreement rests in an equivolcation whereby the term periodic is used to refer to two different things at the same time. The periodic in periodic table refers to the shell structure of atoms and how the shells are filled with electrons going from one atom to the next in the table. There is kind of a physical similarity with atoms having certain numbers of electrons in shells. Then there is the use of periodic to refer to a function having exact repetivtive values. That sense of the term is defined in Mathematical Methods in the Physical Sciences by Mary L. Boas, (2006), page 343

    By definition, the function f(x) is periodic if f(x + p) = f(x) for every x; the number p is the period.

    That is what it means to be periodic.

     

    There are indeed other structures which are periodic but are not waves.

    That is correct. E.g. f(x) = sin x is periodic but not a wave.

     

    However I still maintain all waves are periodic.

    A function f(x, t) is called a wave if it has either of the forms G(x - vt) or H(v + vt). Such a function need not be periodic. Consider the Gaussian function

     

    [math]\psi(x, t) = e^{x - vt}^2[/math]

     

    This is a wave, by definition, but it isn't periodic, by definition.

     

    Back to waves, have you ever heard of the 'periodic equation' for a wave?

    No, I haven't. Sorry. What does it mean?

  22. I also explained to the OP how a collection of particles can show wave-like behaviour. I remarked this about 100 posts ago. The usual interference pattern observed in double-slit experiment with electrons is generated by thousands of particles (electrons). Electromagnetic waves are a collection of particles named photons...

    And since then you've been refraining from acknowledging that an ensemble of identical single particle experiments shows intereference. You have also been refaining from acknowledging that for a single particle with a specifc momentum has a wavelength associated with it. You're also ignoring the fact that collections of particles display wave-characteritics because individual particles have a wavlength to them. Without that associated wavelength the particles can't have wave characteristics.

     

    We all know what you say juan. The problem is in what you refuse to say when you are shown evidence contrary to your assertions. That's the problem here. Everyone keeps telling you that an making the obervation that you refuse to respond to the evidence pesented to you whereby you simply revert to another subject.

  23. !

    Moderator Note

    pmb,

     

    You were not ignored. Your reports were received and are being discussed. etc

    Sorry. My mistake.

     

    Pete,

     

    I said periodicity is fundamental to wave behaviour and have pointed out some uses of the word periodic that do not conform to your 'definition'.

    Brillouin zones are periodic in space. The periodic table is periodic in atomic number.

    I think we're thinking about two different things.

     

    The Copenhagen Interpretation is one the main important postulate of quantum mechanics, and i would not ignore it..

    And to my question that if an electron behave like a particle or wavelength(at a specific period of time), can't be answered, because we don't know what is happening physically inside a particle, unlike classical physics.

    But yes, we can always draw possibilities about it, that is what quantum physics is about.. happy.gif

    I think that the essense of the Copenhagen Interpretation is to connect theory with experiment.

  24. You didn't answer it before. You wrote something, but you didn't actually answer the question. I asked a question to which the answer would be a yes or a no.

    Yeah, but I'm sure that you know by now that juan hasn't been giving direct answers to direct questions. More often he simply won't respond at all.

     

    Unlike what I asked, that's a loaded question. A simple yes or no does not suffice, because there is the nuance that we have classical and quantum particles. I know you know this. "Quantum particle" is also your words. Part of your standard terminology.

    Perhaps you missed it but in an earlier post I pointed this out to him, i.e. that he's using a straw argument in which the heart of his straw is a different, yet undefined, understanding of the terms we're talking about.

     

    I explained this to juan in the post # 92

    http://www.scienceforums.net/topic/67437-particle-wave-duality/page__view__findpost__p__688843

     

    which basically states de broglies hypothesis and the QM postulate whereby the squared magnitude is the probability density. Then I explained to him that de Broglie hypithesis epitomizes the wave-particle duality and explained that an ensemble of identical experiments with sinlge particles. He ignored it of course. He simply won't address counter arguments to his premises.

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