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Everything posted by proton

  1. I had forgotten to mention the HUP so when I came back and added that comment it merged the two posts together. I think I was too late to edit it and that's why I had to quote myself.
  2. I'm both encouraged and surprised by your interest. It's heart warming to see such a keen interest in the physics as your displaying here. I'm also surprised because I would have thought that most people wouldn't concern themselve with this. I'm pleasantly surprised. The idea that uncertainty is created by trying to measure a particle is an urban myth. It is more accurate to say that uncertainty is intrinsically inherent in the system rather than related to measurement. E.g. ideally, no matter how you choose to measure the properties of the system, the uncertainty remains unaffected and is dependant only on the state of the system. This means that once [math]\Psi[/math] is determined [math]\Delta x[/math] is determined. Or to be more precise, once you tell me what [math]\Psi[/math] is I can tell you the value of [math]\Delta x[/math] and I don't need to know anything about how you intend on measuring the postion. The A above refers to a classical uniform magnetic field. There is no frequency associated with it. The associated quantity Bz represents z-component of the magnetic field determined by A. Your very welcome. I admire that attitude. Shows courage in the face of the scary quantum world! One of the rewards of posting here is the satisfaction I get from seeing people enjoy physics and knowing I was able to help. It kind of makes up for those arguements with the resident thought police. Merged post follows: Consecutive posts mergedI forgot to mention that the HUP relation for position and momentum are unaltered in this case.
  3. It should be noted here that at present, energy can't be properly defined when gravity is present. It should also be noted that there is positive energy from things like rest energy and negative energy from the negative gravitational potential energy. It's possible that the total energy could be zero. Paul Davies expresses this as follows. From God & the New Physics, page 31 (Don't let the title of this book fool you. The author is what I'd refer to as an authority in the field of astrophysics. His homepage is http://cosmos.asu.edu/)
  4. Thanks GutZ. I'm quite aware of that. I know that it was a standard message. I was expressing my displeasure at the existance of this thread. It was created on two premises (1) that I have a crusade and (2) that I want to change how people talk. Both premises are wrong. I really only made (or wanted to make) two points in this thread and have succesfully argued them (1) I'd rather leave than have the way I choose to explain physics censored and (2) I never have and never will be anything but 100% clear as to what any term I use means. The use of rel-mass was something I posted in another thread and I don't see that it's useful to repeat myself. I also choose not to argue about the usefulness of the concept since its clearly a matter of taste and arguing about it is like arguing about whether red or blue is the nicer color. How this affects how I use the term momentum in the future is now making me wonder. I never gave that much thought until I came up with that example. I appolgize if you were offended. That wasn't my intention. The term misinformation is defined as inaccurate information that is spread unintentionally. Perhaps you prefer another phrasing, e.g. what klaynos posted is emperically incorrect etc. This is a well known fact and is expressed in the journal articles written by the people who are trying to ban the concept. In fact one of the reasons they keep writing these articles is because physicists still use it. Not only physicists by chemists and astronomers etc use it too. This is getting sillier by the second. Fact - Whatever is posted in this thread after this post I hereby promise you will go unread. If I read anymore false assertions about what I have or will post I will not be happy and might feel inclinded to correct them - again! Proton - out.
  5. I read an article on this. If there is no magnetic field then p = mv and [math]\Delta p_x \Delta p_y = 0[/math] which means that [math]\Delta v_x \Delta v_y = 0[/math]. When there is a uniform magnetic field present then this becomes [math]\Delta v_x \Delta v_y > e\hbar/2m^2c |<B_z>|[/math] This would not be apparent if one didn't know how p is actually defined.
  6. What do you mean "crucial to add"? If you mean when it is important to know what quantity appears in the equations then, for example, when its a charged particle moving in a magnetic field. In that case the momentum the HUP refers to is cannonical momentum and depend on the magnetic field. As I said, this is an advanced topic. But I wished I knew about if when I first learned quantum and not when I studied it as an upper classman
  7. It should have been locked a long time ago. In fact it never should have started. Especially not in this forum since the subject matter in the first post is neither pseudoscience or speculation. One can hardly claim that subject matter in the American Journal of Physics can fit into those categories. It was hardly off-topic either since I was correcting the misinformation posted by Klaynos.
  8. Since Martin started this thread, what position are you claiming that he failed to support? I do agree, however, that Martin failed to prove that I want to change the way people use terminology.
  9. Huh? I said I won't be dragged into a debate and most of the posts here are designed to do so. I never claimed anything else. If you don't care what people want then ignore the suggestion. Simple. If the forum prohibits posters from making suggestions then it should be in the forum rules. When I see it there I will stop making suggestions. I made my point before this thread was started. What a silly thing to say. I never made such a claim. I can't fathom how someone could jump to such an obviously false conclusion. Only an extremely arrogant person would think such a thing. In fact I've only argued that I will explain physics in a way that I think works best. Please pay closer attention to what you're reading. I have to admit that most of my resposes were to correct false accusations made against me. I find it hard not to correct someone who says something about what I've posted/said or will post/say that is not true.
  10. I'm going to try an experiment here. There is a debate on terminology in another thread and I want to try something here to see what happens. You know that the uncertainty principle relates uncertainty in momentum to the uncertaintly in position, right? What you don't learn until advanced courses on quantum mechanics the momentum this refers to is actually what is called "cannonical momentum" (aka conjugate momentum). Its different than the momentum p = mv (small p) that you learn about in basic physics. Suppose a charged particle is moving in a magnetic field. The cannonical momentum p has the value (B-45) p = mv + qA where A is known as the magnetic vector potential. A graduate text by Cohen Tannoudji explains this (page 225) as follows Since canonical momentum is a rather advanced topic and probably not known to most visitors here I'm curious as to whether such a fact is of interest to anyone, i.e. would you want to know that p is a function of the magnetic field through the quantity A? Thanks for your input. Mod note: moved to its own thread
  11. No. That would be like saying "This apple is energy." The apple is not energy. It merely has energy. Why the comment about minus the known forces? Forces give rise to potential energy.
  12. I kept saying that above many times. You'd be wise to lock this thread otherwise everyone will keep trying to draw me into a deabate that I had stated I will not participate in.
  13. This is another example of a poor arguement. You'r claim that I don't use clear definitions is bogus. You would never be able to find a post where the definition of any term I used was not 100% clear. I can't help it if this simple fact is not getting across to you. And don't give me this nonsense about experts since I personally know plenty of experts in various fields of physics who publish just as much, if not more, than the people here - whom I have no idea who they are by the way. And those people would never present such arguements in their lives. Don't confuse the people who choose to post in discussion forums as being representative of the fields. You're said you're an undergraduate. I've been a physicist for over 20 years so please don't give me this nonsense you're now giving me about so called authorities. And I find your attitude quite poor. Chill out please. Moderators should not be so irritating. Merged post follows: Consecutive posts merged You posted an arguement based on the notion of "common terminology." I responded to that post by asking you to define the term momentum so I could make my terminology. So your claim that I'm not arguing the same point others are is quite incorrect. You are referring to other arguments made by people here. I find them to be poor arguments and I know that people are pretty closed minded in this subject so I choose not to participate. This is a perfect example of what I meant by a poor arguement. You keep assuming that I intended to use or have in the past used the term "mass" to mean something besides "rest mass" even though I explained in great details this has not happend and is not going to happen. I explained this several times. There is no example where people are not 100% clear on what I mean. If I choose to say "Below by mass I will mean relativistic mass" it is only to make the writing easier for me since its easier to write mass than relativistic mass. It is just for the sake of ease of typing, nothing more. And when that is said its not possible to make a mistake on what the term means. This is the same idea of saying in the quantum section "Below by momentum I will mean canonical momentum".
  14. Depends on the precise definition of that term. E.g. a sine wave is infinite in extent. In practice it's finite. For example; for a particle in a box the wave is non-zero inside the box and zero outside. If a particle is represented by a Gausian wave then it's large near its peak and drops off as one gets further from the peak, but mathematical never equals zero but is close enough to zero for any practical purpose. No. You need the state to be an eigenstate to be sure of the value you get. Any measurement yields a value whose precision depends only one the experimental set up and instrumentation used. The precision is independant on the nature of the wave. Yes. An arbitrary state is not a simple one. But any arbitrary state can be represented as a superposition of eigenstates (e.g. plain waves). Sound is like that. Any sound can be reduced to a superposition of sines and cosines.
  15. I understand his point quite well, thank you. I hope we're not going to get into a debate about whether I undertand his point now, are we?? Thanks for answering. Now I can make the point I've wanted to for days now!! Just to make sure that there is no confusion about what my point will be let me recall for you why I asked this question. Recall what swansont wrote
  16. That is quite incorrect. If you'd answer the question then you'd see that the purpose of it has everything to do with this thread and the points you attempted to make. It's such a trivial and easy question. I suspect that you know that I'd strongly argue my point if you responded and that is why you refuse to do so. I challenge you to prove me wrong by posting the definition of momentum. After all it was you who claimed that we all have to mean the same thing by each term or confusion arises, did you not? So post what "everyone" means when they write the term "momentum" please. Then again if you refuse to answer it also demonstrates my point quite well too. Wrong. The people who posted in this thread want to debate the usefulness of rel-mass. I never had a desire to debate the concept since it's a fact that any such debates is ultimately a waste of time. You can't argue about what is useful to one person because everyone thinks differently. I've only responded to correct misinformation that has been posted in this thread, e.g. what I supposedly wanted people do do etc.
  17. It really makes no difference the shape or extent of the charge distribution. Charge at rest in one frame means that there is current in another frame moving relative to that frame.
  18. Who said it wasn't there? Not I. I said that wave nature and quantum nature are not the same thing. I also said that when a quantity is measured in discreetly quantized systems the result is precisely determined. What part of that are you suggesting is wrong?
  19. Obviously. But that doesn't change the fact. The reason it transforms differently is that energy in motion is defined differently than heat. Ignoring context leads to errors in application. Heat is defined as the flow of energy from one object to another caused by a difference in temperature. The cause of light from a laser is not caused by a difference in temperature so one can't call the radiant energy from a laser "heat". Heat is also the quantity Q in the relation [math]\Delta U = Q + W[/math] That relation defines Q and is why it transforms differently than energy. You seem to think that any energy which flows is called heat, for what reason I can't see. Since this is going nowhere so I have nothing left to say.
  20. You used quantum to be synonymous with wave so your question has no meaning. I already gave you an example, i.e. spin. Spin is not wavelike. Anything which has a discrete spectrum is like that. When a measurment is made on a discrete system for which there is a uncertainty in the quantity being measured one can theoretically obtain precise values. Hence the difference between uncertainty in a state and the absolute precision of measured value. Debate!? Nobody said anything about debate. I was merely saying that your responses represented what I consider to be misconceptions. If it will help you move on then I rephrase my comment as "That remark represents a misconception." Back to physics - Theoretically the eigenkets of position are defined as X|x> = x|x> where X is the position operator and x is an eigenvalue of position. An arbitrary state can be expanded in terms of these eigenstates as [math]|\alpha> = \int dx|x><x|\alpha>[/math] A highly idealized experiment might be to place a very tiny detector that clicks when a particle is at x and nowhere else. After it clicks we say that the state is represented by |x>. I.e. we say that [math]|\alpha>[/math] jumps to |x>. However in practice one normally can only locate the particle to a narrow interval about x. So the state goes from [math]|\alpha>[/math] to [math]\int dx|x><x|\alpha>[/math] where this is integrated over the width of the detector. If the particle is located within this range the detector clicks. This is, by definition, a particle property. Your assertion about variance means that the width is non-zero. But your comments about it suggest that there is no particle phenomena here which is misleading. The "click" means that the particle is localized in the sense defined above. That's what the term particle means and what was meant by the Dirac function being represented in practice by a step function. Interpretation is a key point here. Point particle means that there is no theoretical limit to the smallness of the detector. The reader can read more about this in Sakurai in the section Position Eigenkets and Position Measurements. I was speaking in general terms, not about position. If you read my comment more carefully you'd have noticed that since I wrote This happens when there is a discrete spectrum of eigenvalues. Obviosly position has a continous set of eigenvalues.
  21. I explained above. Please reread what I wrote, i.e. determined with infinite precision. Consider a measurement of the spin of an electron. There can only be two possible values which are theoretically determined with no uncertainty. Credentials???? Just because it's my opinion that you have a misconception, as reflected in your response, it has absolutely nothing to do with credentials.
  22. In relativity heat transforms differently than energy. So one cannot merely make the assertion the blind assertion that radition is heat.
  23. That doesn't appear to be what Severian meant since he wrote
  24. I wouldn’t phrase it like that myself. Particles cannot be said to “really” be a wave. That contradicts the wave-particle duality. The whole idea is that they have wave properties and particle properties. Do you recall how Feynman explained this? From his Lectures, V-III page 1-1 Actually our measurement of its position can be made with arbitrary precision regardless of what the uncertainty in position is. Where did you get such an idea?? Nothing could be further from the truth. Not true. Your first comment is correct. When a measurement is made the state falls into one if its eigenstates, not a superposition of them. I.e. when the position is measured the state is |x>. Since no measurement has infinite precision there delta function might actually be approximated by an extremely narrow step function. But that doesn’t mean that it’s a wave and not a particle. And as I stated above, the imprecision of a measurement has nothing to do with uncertainty. It's quite possible for a system to have a finite uncertainty and for a measurement to be made in which the result is determined with infinite precision. This happens when there is a discrete spectrum of eigenvalues. Nothing personal, but I’m afraid that you have some misconceptions about the wave-particle duality.
  25. swansont - the only reason I'm checking this thread now is to wait for your response to my question regarding the definition of momentum. Please either respond to it or state in no uncertain terms that you won't be responding to it. I'm not sure if you keep missing it of choose not to answer from some very odd reason. I find it quite odd that you don't mind asking me all sorts of questions but the one question that I ask goes totally ignored. Why do you suppose that is?
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