Jump to content

pmb

Senior Members

379

1. is mass equal to energy?

You have to be cautious in forums suchs this. Different people mean different things when they use the term mass. For example, in A first course in general relativity by Bernrd F. Schutz the author writes on page 94 ..energy and 'inertial mass' are frame dependant ... and on page 104 he writes ...energy and mass are the same.... Other people refer to mass as being synonymous with proper mass. Severian is talking about proper mass (aka rest mass). I think that with this in mind you'll better understand the subject matter. The way Taylor and Wheeler describe mass then in such explosions the mass remains unchanged. In their text the term "mass" refers to what is known as invariant mass. This means that we sum up all the energies of all the particles and cal it E and sum up all the momenta of the particles and call it p. The mass according to them is the m in $E^2 - (pc)^2 - m^2c^4$ and this remains constant during a nuclear explosion. This is because energy is conserved and in the zero momentum frame E = mc2 In a sense, sure. The energy is bound up in what is called binding energy which is essentially potential energy, which is negative. While its true that both energy or mass are conserved, its also true that matter changes form. When an electon and a positron annihilate what is left is photons. So the form of the matter changed. Ya got me.
2. CAn we get an ignore list?

This thread degenerated into a stream of insults so I deleted all my posts.
3. Proper Mass redux

It's hardly silly. Many relativity textbooks us it. Percentage wise about 67% of textbooks published between 1970 and now use it. I see no valid reason to think it silly when that many physicists use it That's incorrect. I was speaking to a well-known cosmologist/particle physicist yesterday and he told me that in cosmology physicists use the term "mass" to refer to E/c2. H'e's very very well-known in his field so I trust him. Plus I have several relativity texts which prove otherwise. The list inlcludes such texts by such authors as Misner Thorne and Wheeler (page 141), Mould, Rindler, D'Inverno, Schutz. Stephani. You can see a short list here with the relevant quotes http://home.comcast.net/~peter.m.brown/ref/relativistic_mass/relativistic_mass.htm That relation doesn't always hold. On example is when the body is under stress. $p=\gamma m v$ is inlid under such a case but p = mv is still valid. Another example is an extended body which is emitting radiation. In such a case the mass per unit length of the rod can be uniformly decreasing. In an inertial frame moving parallel to the rod the mass per unit length is not uniform. The proper time in this case has no meaning so that $p = m\frac{dt}{d/tau}$ has no meaning. However p = mv still has meaning. For details please see http://home.comcast.net/~peter.m.brown/sr/invariant_mass.htm See last section entitled An Incorrect Application of Invariant Mass
4. What can we talk about?

Hello Folks! I'm newly back and want to say hello and that I sure missed some of you. I miss some lively and challanging threads with some people I have a lot of respect for. Thanks for being here folks! Now that I'm back I want to fresh and not make any mistakes and get a better understanding of the rules. I seemed to have posted things that I wasn't in the wave-particle duality thread. So I want to learn what to do in certain instances. Not only from moderators but mainly from other members who've run into similar situations and was able to resolve it to their satisfaction without getting a red moderator tip directed at them (I hate it when that happens). So I decided to start a thead about what kinds of things we can do when we encounter irritating circumstances. Let me give an example: I a thread in this forum someone posted an assertion that I said something in a thread that I never said at all. In fact my entire contribution to that thread was the opposite of what was asserted. When I asked that person not to put words into my mouth. Not only was I ignored but when I asked them to provide proof the asertation repeated and no proof provided. That's pretty irritating. If I express my irritation will I get into trouble? Do we have the right to express emotion here? I was going to ignore the whole thing it since I didn't see that I had any recourse. I tried the report system but saw no action taken. However I just saw Phi fo All post the following comment when stating the reason for suspending a member. See -- http://www.scienceforums.net/topic/29763-bannedsuspended-users/page__view__findpost__p__691185 That seems to have been when the straw that broke the camels back. Can't there be a rule whereby when some accuses a member of saying something that the person who makes the claim must prove their claim when requested? Otherwise people can otherwise get away with lying. Then there are other examples where evidence is desired for questionable assertions? For example, if someone says that's not correct in mainstream physics then there should be a criteria for proof. E.g. quoting an undergraduate or graduate level text on the subject. After all the rules say, i.e. from http://www.scienceforums.net/topic/7813-science-forums-etiquette/ I always back up what I say with textbook references. I see that's a rare thing here though. Then there is the overuse of strawman arguments here. They are banned by the rules but it never seems to be enforced, i.e. http://www.scienceforums.net/topic/7813-science-forums-etiquette/ The link to Strawman reads - http://www.nizkor.org/features/fallacies/straw-man.html This is what happened when I was misquoted. We already lost one member because of irritating things like this. Can't we call them out in a way that is acceptable to the powers that be? I mean I don't want any more complaints about me so I'm trying to figure out what to do about things like this. I posted this in a public thread because I wanted to see if I was the only one having this problem. I thought I'd include the definition and trademarks of pseudoscience as defined in my logic text Practical Logic: An Antidote for Uncritical Thinking by Soccio and Barry. This way we might more readily recognize it when we see it. At least some of its trademarks. From page 384-385 Thanks.
5. Light has mass?

I don't know what this is supposed to say. It appears to say Total Mass of Sun = Mass of Sun + Photon Mass of the Sun The mass of the sun is a complicated function of the mass-energy of the particles in the plasma that mack up all the matter of the sun, radiation included. This includes the rest mass of all the nuclei in the sun plus the kinetic energy of all those nuclei. This includes the contribution to the mass of the sun by the radiation in the sun, i.e. photons. To be precise, pressure is also a source of gravity. It has more relevance for objects such as neutron stars. The active gravitational mass of a perfect fluid is $\rho_g = \rho + 3p$ where $\rho_g$ is active gravitional mass, $\rho$ = proper energy density and p = pressure. For disordered radiation both $\rho$ and p are non-zero. Nice! The point you made is the same point made in the physics literature. I prefer the term proper mass ove rest mass anyday. Even though the proper mass of photons is zero we still have 1) Inertial mass (aka relativistic mass) of photon is non-zero 2) Passive gravitational mass of light is non-zero 2) Active gravitational mass of light is non-zero Ummmm ........ he's here to learn physics. Hence his questions.
6. Particle wave duality

Comments such as this on the graduate level text I quoted you, and which you failed to shoot down, doesn't speak well for the quality of your opinion. There simply doesn't exist a text or a peer reviewed physics journal article which says the the wave-particle duality is a myth. Many of us, such as myself, know quantum mechanics very well (graduate level) and know what you've been claiming is total nonsense. Don't you understand that? My appologies. I was simply commenting on the tact that I'm taking here.
7. Particle wave duality

I haven't insulted juan and I never said anything rude. I also haven't stated something that wasn't true, e.g. that I never said a particle is a wave. The worst thing I did was to point out that juan was using a personal attack on immortal and is inccesant false accusations claiming I said something which I'd never say to anybody. It really bothers me to see people insult/attack others. But in order to take on a new state of politeness and civilness I have deleted those remarks. What are we supposed to do when people make false accusations? You give off the impression that it I say that someone is usig a falsehood that I'd get into trouble for pointing it out, regardless of how I go about it. What are we supposed to do we do in those cases?
8. Particle wave duality

You're wrong. I already told you that and you simply ignored it. That is not how a cogent argument progresses. Prove me wrong. Reference a post where I said a particle is a wave. Until then stop putting words into my mouth.
9. Particle wave duality

I myself go by books for the basics of physics and this is a well-known fact in quantum mechanics and is quite often addressed in text books. That's why I rely on them so much. Papers don't address basic physics for the most part so its much harder to find such an article. Here is a section from Shankar's QM text (graduate level). From Principles of Quantum mechanics - 2nd Ed. by R. Shankar (graduate level quantum mechanics text), page 113 That and $\lambda = h/p$ expresses the wave-particle duality. He's very selective about what he posts. I guess that's just human behaviour. He never mentioned the wave-particle duality as mentioned by Feynman in QED but posted other comments, which when taken out of context, appears to support his position. CERN has better things to do with its website then post basic QM. Or maybe I can find something that juan overlooked (intentionaly?). I'll search the website and see what I find.
10. My recent banning

While I don't condone that behaviour I believe that I can, to a certain extent, empathize with your feeling. It appears that way to me too. I hope you change your mind. I find this place more tolerable with you here. From our discussions in private I've gotten to know you personally and that side of you doesn't come out here. If it did then I'm sure you wouldn't run into such problems.
11. Particle wave duality

Today I followed an ad hoc derivation of Schrodinger's equation. I confirmed what I long knew, i.e. that a wave function of the form $\psi(x, t) = Ae^{i(kx - \omega t)}$ is a solution to both Schrodinger's equation and the wave equations. Are you familiar with such a derivation?
12. Particle wave duality

Please don't put words into my mouth. I never said any such thing. In my opinion your arguement is flawed in that nobody has suggested that a single particle is a wave, nobody whatsoever, and your arguements are based soley on that false assuption that someone said that particle is a wave. Nobody said that in this thread. Lok for yourself. If what you say is true then you'd be able to give us a post number where it occured. I myself have never said, thought, or implied any such thing. Herein lies the flaw in your argument. In fact in my very first post in this thread, i.e. post #16, I said that I love the way Feynman explains it in his Lectures. In V-II page 1-1 Feynman writes Bolding is mine. That means that a particle is not a wave. If you look in Feynman's book QED and check the index then you'll see that Feynman explains the wave-particle duality on pages 23 and 37. What I found relavent is one the wavelike character of electrons on page 84. On page 84 he hits the nail on the head when he writes The bolding is mine. This is pecisely what we've all been saying all this time and which you claim is wrong. Feynman clearly said wavelength of an electron. This is what it means for a beam of electrons or an ensemble of them. to have wavelike properties. IT must be the fact that each electron has a wavelike property in order for the Davisson-Germer experiment to demonstrate wavelike characteristics. The term "wave like characteristics" does not mean that a particle is a wave.
13. Particle wave duality

Nobody in this thread has suggested that a particle is a wave. That's why I quoted Feynman. He said just the opposite, i.e. from post #16 See what I mean? We know that they don't behave like waves.
14. Particle wave duality

All that means is that the people that you're quoting don't understand the wave-particle duality. What part of $\lambda = \frac{h}{p}$ probability density = $|\psi(x)|^2$ don't you understand? Those two relations epitomizes the wave-particle duality. Which of those two expression are you claiming is wrong and why?
15. Moderating a Forum

What can I say? I was frustrated at his wild accusations and him getting all flustered about something that appears only to have happened in his mind and not in reality. For example: CaptainPanic - I reviewed my contribution in the most recent thread in the suggestions section, i.e. the one about the rep-system. You claimed that I have 94 (!) posts in the Suggestions, Comments and Support section. I have no way to verify and examine those posts to see what they were about. So what I did was to examine the thread I knew about, i.e. the one about the "reputation system" thread. Here is what I found - Out of the 272 posts in that thread I created 31 of them. That accounts for 31 of the 94 posts you mentioned. Out of those 31 posts only 4 of them contained comments about modertors. Out of those 4 posts about moderators, one of them was about you in which I said (in post #238) CaptainPanic deserves an accomadation for the way he moderates. The other moderators should take him as guiding post. That really doesn't come off as your comment seems to suggest. It therefore you seem to have taken things out of context. Refering to things that perhaps happened months ago and which may not have anything to do with negative comments about moderation. I'd wager that the other posts of mine in that section are about the subject of ad hominems. I don't ever recall why I put it in that section. Probably because it didn't seem to go into the other sections.
16. Moderating a Forum

I don't understand why you keep putting words into my mouth? I never suggested that moderators generally abuse their powers. I wouldn't even believe it someone claimed it. And that's all I asked, i.e. I only asked two questions about it. That's correct. They were. Again with the exageration? Why do you keep doing that? You are quite wrong in yoru accusation that I never stop. As far as I'm concerned I only had two questions. One in the "reputation system" thread and one here. Both of them was addressed to my satisfaction. The one here was addressed back at ppst #8. After that I've just been disuading false accusations. This whole time I merely inquired into it twice. You're taking this out of context. You make it appear as if I was complaining about the moderators 94 times. I didn't. First off that thread was about me. I.e. in post #1 the OP wrote, in part That's the first post in that thread where my name came up. I didn't even post until post #48. And I didn't mention moderators in that post. I only chimed in about moderators when a moderator criticized my use of the rep system. It seems I may have misunderstood them though. That was mere polite discussion about moderation. Don't get your panties in a knot over it. In the mean time I plan on going through all of those posts in that thread and examine how many of them were actually me commenting on moderators. I'll get back to ou after that. In the mean time I once again ask you to please stop exagerating. It gives off a false impression.
17. Ad Hominem

Opinions are sought on the subject matter, not on off topic distractions such as silly things like me asking swansont why he was frustrated over a disagreement. Yes. That's what I stated. But that wasn't the question. The question was Would you say that this is an ad hominem? which was a question asked about a particular ad hominem. What you commented on was something that was not on topic, i.e. not about that particular a hominem. But if you thought it neccesary to ask about that then you didn't need to be rude about it.
18. Moderating a Forum

You're being unfair. All my questions were basically answered in post #8 where you told us that moderators are bound by the same rules that we are. Yes. I bitch when I see a moderator post a comment which I percieve as rude. Big deal. I do the same thing when I see anybody being rude. Why should moderators be exempt? People in positions of autority usually aren't above the laws they enforce. Is that different here? Are moderators really so darned offended when we ask them questions about their job? You make it appear as if inquiries are really condamnations. They aren't. Anybody who thinks that is being paranoid. As you youtrself just said, we're not perfect. Your comment about finding another forum is unfair too. It reminds me of those people who say If you don't like America then why don't you leave? The purpose of this thread is to end my inquery into the subject, not to bash moderators. I've already stated this. In post #13 I wrote In post #21 I wrote Is this what you're complaining about? Are you pissed off because I admire the moderators as a whole? My real concern here pertains to a couple PMs I got from a moderator who insulted me in them. First the moderator sends me a PM complaining about a PM I sent to another member for being rude and then the same moderator is rude to me because I happen to experience emotions deeply. I've always been that way and its not as if I have a switch where I can turn it off. Sure. Stop exagerating and putting words into people's mouths and if someone thanks you or tells you that they admire you, don't complain about it. How's that for starters?
19. Moderating a Forum

You're acting like your their mother when in fact they're grown adults who are responsible for their actions. Its not as if they're children who can't control their actions. All I'm saying is that they shouldn't be hypocrits, that they shoulld act like they're expecting us to act. Being human doesn't mean that they are incapable of doing that. All moderators are capable of posting moderatror comments in the polite fashion that they expect us to post our responses. Let us recall what this forum is. The subect matter for this forum is Suggestions, Comments and Support. That's why I posted this in this subfoum, Yep. I was simply adding my 2 cents since this is the subject of this thread.
20. Moderating a Forum

Myself, moderators expect us to be polite, which I appreciate. I very much enjoy a forum where the membrs are polite so I appreciate that kind of thing. However there are a few moderators who aren't always polite themselves and they really should be, expecially when they're moderating. Otherwise moderator directions, comming from somone who is expressing anger or impatience, can actually work against calming people down and as a result some members, unfortunately even me in the past, then feel the need snap back in kind. I'm working to get that under control on my end but its hard when someone is being mean to get what they want.
21. Do magnetic fields lines have a motion?

No. Magnetic fields cannot correctly be thought of as moving. They can be thought ofhas hava direction though and given the Lorentx force acting on an alpha particle I would expect the results you just reported. Where did you get a cloud chamber and source of alpha particles from if I may ask?
22. Moderating a Forum

Thanks. I appreciate that. Yeah. I know. I've found it helpful to talk to people in PM about these kinds of things. It turns out that the people you might apprear to be real jerks turn out to be very nice people. You jnust need to get to know them, that's all. I found it to be a very rewarding experience myself. A real education too. Yeah, but a conversation consists of more than one person. If the conversatin continued for 14 pages then it was caused, in part, by the moderators defending themselves. No matter what the circumstances are, when someone is trying to defend their actions it is never fully accepted. I've seen that too many times to count and that's what I saw in that thread. People defending themselves. OIf course. And this thread shouldn't be used as an excuse to criticize them or the poeple who have arguments with them. I expect that moderators do what they do because it has its rewards on its own. There must be some satisfaction in moderating a forum. Perhaps people enjoy having a saw a to how a forum runs or whatever the case may be.
23. Moderating a Forum

These kinds of things are private which means that they came in PM and therefore it should remain there. A few days I anonymously discussed such a PM. Even though I kept it private as to who was who the other person was very upset that I mentioned in in open forum. Therefore I don't want to make the same mistake again. I'd be glad to discuss it with you in PM though if you want. If so then please send me a PM stating what you want to know. I'l considerate to make sure its not something someone could get angry with me again and we can go from there.
24. Moderating a Forum

Yeah. I'm well aware of that but there's nothing I can do about it. With accolations sometimes come objections. While iI'm interested in discussing moderator actions and responsinilities it doesn't mean I can force people from going off topic. But responding to negative emotions acts to keep those emotions alive. It's best to avoid acknowledging negative emotions. But even then its sometimes getting people to open up about negative feelings that have been raised can sometimes be a good thing, kind of a carthartic thing. Just remember that when you respond to them you're doing the same thing, i.e. you've let it take you down a negative path when that happens. But that happens in all too many threads.
25. Moderating a Forum

Please don't exagerate the purpose of this thread. The moderators are grown adults. They can take care of themselves. You're making it appear as if this is a crap-on-moderator thread for some reason. It's not. The openting post stated its purpose, i.e. For the most part the moderators are really wonderful and I admire them. This forum's moderators beat out other forum moderators. But the question did come up about what moderators do around here and I was curious as to whether they hold themselves to the same standards that they holdus against. Cap'n Refsmmat has explained all that to me so I'm now satisfied. So please stop trying to drag this thread down and please cease your attempts at making it appear as if it was a moderator bashing thread. It's not and I object to that implication.
×
×
• Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.