swansont Posted April 26, 2011 Posted April 26, 2011 Pair production is not really spontaneous, in the same sense that decay is. A photon cannot create a particle/antiparticle pair in free space because momentum would not be conserved — you can choose a frame where the momentum of the pair is zero, but there is no such frame for the photon. So this has to take place with a particle (typically a nucleus) nearby, and that other particle recoils to conserve momentum. So a photon that does not encounter a particle in deep space cannot undergo pair production.
IM Egdall Posted April 27, 2011 Posted April 27, 2011 Pair production is not really spontaneous, in the same sense that decay is. A photon cannot create a particle/antiparticle pair in free space because momentum would not be conserved — you can choose a frame where the momentum of the pair is zero, but there is no such frame for the photon. So this has to take place with a particle (typically a nucleus) nearby, and that other particle recoils to conserve momentum. So a photon that does not encounter a particle in deep space cannot undergo pair production. Cool!
DrRocket Posted April 28, 2011 Posted April 28, 2011 Pair production is not really spontaneous, in the same sense that decay is. A photon cannot create a particle/antiparticle pair in free space because momentum would not be conserved — you can choose a frame where the momentum of the pair is zero, but there is no such frame for the photon. So this has to take place with a particle (typically a nucleus) nearby, and that other particle recoils to conserve momentum. So a photon that does not encounter a particle in deep space cannot undergo pair production. But two photons may, through a somewhat subtle process, generate a pair. http://en.wikipedia.org/wiki/Two-photon_physics
michel123456 Posted April 28, 2011 Posted April 28, 2011 But two photons may, through a somewhat subtle process, generate a pair. http://en.wikipedia.org/wiki/Two-photon_physics Weird Wiki article.
steevey Posted June 7, 2011 Author Posted June 7, 2011 (edited) That was funny. Why did you vote negative? When the pupil has the courage to say he doesn't understand, part of the blame goes to the professor IMHO. Most of the time you get angry when the pupil doesn't admit his ignorance. Now is the time to choose. I'm not mad at swan at all, he's just bad at explaining things, thats why I need to ask him so many questions. There's people who can explain like an hour of information and I don't have to ask them any questions at the end. This unfortunately does not seem to be true for swan, at least with me. Edited June 7, 2011 by steevey
steevey Posted June 7, 2011 Author Posted June 7, 2011 (edited) That was funny. Why did you vote negative? When the pupil has the courage to say he doesn't understand, part of the blame goes to the professor IMHO. Most of the time you get angry when the pupil doesn't admit his ignorance. Now is the time to choose. I'm not mad at swan at all, he's just bad at explaining things, thats why I need to ask him so many questions. Also, are all you guys absolutely 100% sure that a wave function is that ONLY wave property of particles? As in, your 100% sure there's no other wave-properties of particles that aren't just its location? Edited June 7, 2011 by steevey
swansont Posted June 7, 2011 Posted June 7, 2011 I'm not mad at swan at all, he's just bad at explaining things, thats why I need to ask him so many questions. There's people who can explain like an hour of information and I don't have to ask them any questions at the end. This unfortunately does not seem to be true for swan, at least with me. You have a link to someone who has written an hour's worth of material, on demand, as an answer to a question you had?
steevey Posted June 7, 2011 Author Posted June 7, 2011 (edited) You have a link to someone who has written an hour's worth of material, on demand, as an answer to a question you had? I'm sure there's videos on youtube, but I don't know what they are called. And some of them aren't all renowned physicists either, they are just people in the same city as me. I think one of them might be Brian Cox though when explaining dark matter or what the Hadron Colider is looking for. There's probably youtube videos of him since I saw people recording him with cameras at one of his presentations. Edited June 7, 2011 by steevey
mooeypoo Posted June 7, 2011 Posted June 7, 2011 Wow, I never thought of watching YouTube videos to answer all my physics questions. Please, go watch these informative and non-interactive videos and obtain a virtual PhD-equivalent level of knowledge of the entire operation of the universe without the need to ask a single question. In fact, please come back to us afterwards so you can help us instead. Because you're right, how silly it was of swansont to go all complex on you; physics is never complex at all! It's all simple and clearly stated and never anti-intuitive or mathematical. Ever. All those PhDs who spent years getting an expertise are just pretending to study. In reality you can simply absorb the knowledge to each physical subject by reading a single answer post in a single forum thread and by watching two or three YouTube videos. You don't even have to have a single college-level physics class, because it will all just become so clear after you watch the blurry CGI effects on YouTube. It should be an accredited University. Do tell us how brilliantly done those huge amount of physics videos are, since you will, of course, understand the material so well afterwards you will have no questions at all to ask. It will be so clear, you might as well earn an entire theoretical physics PhD in an hour. Swansont was just trying to confuse you on purpose by wasting his valuable time sitting down and reducing a complex subject to something a non-college-physics-level student can conceptually understand. Shame on you, swansont. We will make sure to notify our volunteer experts stop wasting their time, too, since obviously taking their valuable time to try and answer people's questions and try to explain complex concepts that usually require years of study to forum-posters who have barely any college level physics is so ridiculously simple, it's just a waste of their time. We should ask those wonderful people from Yahoo! Questions to instead come and text you theoretical physics concepts in 140 characters or less. We're onto you, swansont. ~mooey Disclaimer: Please remember to wipe your screen after reading this message. Large quantities of sarcasm are known to corrode screens and young minds. 1
swansont Posted June 7, 2011 Posted June 7, 2011 I'm sure there's videos on youtube, but I don't know what they are called. And some of them aren't all renowned physicists either, they are just people in the same city as me. I think one of them might be Brian Cox though when explaining dark matter or what the Hadron Colider is looking for. There's probably youtube videos of him since I saw people recording him with cameras at one of his presentations. So you are comparing a written response with a video explanation, and these videos are not in response to specific questions that you have asked. I guess the reason I don't find your observation insulting is that it's so barking irrational, and that there's a simple cure. I'm really not interested in writing posts on introductory physics to bring you up to speed. These things already exist. They are called textbooks. If you want to ask advanced questions yet can't be bothered to educate yourself on the basics, the blame for not being satisfied with the response starts in the mirror.
steevey Posted June 7, 2011 Author Posted June 7, 2011 (edited) So you are comparing a written response with a video explanation, and these videos are not in response to specific questions that you have asked. I guess the reason I don't find your observation insulting is that it's so barking irrational, and that there's a simple cure. Actually, the only reason I did go to his lecture at all is because I actually had questions on what the Hadron Colider was looking for and about how other exotic particles act the way they do, like how we can't see dark matter. I'm really not interested in writing posts on introductory physics to bring you up to speed. These things already exist. They are called textbooks. If you want to ask advanced questions yet can't be bothered to educate yourself on the basics, the blame for not being satisfied with the response starts in the mirror. If you don't want to answer questions, why are you an expert on this website? You also seem to be getting a little too defensive. Your just not as good at explaining things so that someone without much prior knowledge can understand it and you don't need to go blaming my ignorance for it because if I'm asking you such basic questions then you should already know that I'm not as acquainted with the subject of the question. If you only like answering super advanced questions let other people answer my questions. I don't like answering medical science questions so I don't answer them. There's probably many other people who would answer questions here if you don't like doing so. Oh yeah, and this isn't basic stuff either, this is quantum physics and advanced particle physics, something on the frontier of human understanding, so don't blame me for not knowing much about it. Edited June 7, 2011 by steevey
mooeypoo Posted June 7, 2011 Posted June 7, 2011 You don't seem to want to participate in accepting answers, you want to be fed simple answers that fit your view without taking the time to learn anything extra. There are a few posts in this thread that offer some really good textbooks to allow you to learn more. Are *you* interesting in learning? Maybe you should go over my previous post some more before you so callously try to piss in the well you drink from. ~mooey
steevey Posted June 7, 2011 Author Posted June 7, 2011 (edited) You don't seem to want to participate in accepting answers, you want to be fed simple answers that fit your view without taking the time to learn anything extra. There are a few posts in this thread that offer some really good textbooks to allow you to learn more. Are *you* interesting in learning? Maybe you should go over my previous post some more before you so callously try to piss in the well you drink from. ~mooey The only probablem with being satisfied with answers is when I think I understand what swan is saying, I use that interpretation in a post and he says its wrong. So I can't just accept an answer from him because I likely got the wrong interpretation. Probably because he likes answering advanced questions more and isn't so use to answering questions so that they are simpler and easier to understand. Edited June 7, 2011 by steevey
mooeypoo Posted June 7, 2011 Posted June 7, 2011 Okay, enough,this isn't a "beat on the people who are trying to help you" forum. Thread closed, and I suggest you re-read my previous and previously-previous post. Seems some sarcasm might be in order here for you. People here spend time and effort to answer you. A "thank you" might be too much for you; I suggest at least stop offending the people who do that for FREE for you. It's not about accepting answers blindly, it's about not being so damn rude to people who TRY to help you understand concepts you don't care to even try to cooperate with. So let me finish this thread in the good note it should receive: You're welcome. Thread absolutely and utterly closed. 2
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