@Danu: BTW, I must apologize for the all caps yesterday. I did that because people were teaching you how to work around having spaces. Learning to work around really bad practices is just asking for trouble and I really wanted to help you avoid headaches.
@DanielSank haha, don't worry man. I am not the one to take things too seriously. I don't think you could seriously piss me off through SE even if you tried ;)
The gauge symmetry is local. The symmetry responsible for the charge conservation is the tiny global part of it, and it would be conserved even without electromagnetism, i.e. the gauge part. It's just another Noether charge
@ACuriousMind: it seems to me that he asked something else. One of his questions was: "I also want to know that if there actually does not exist any field without directly or indirectly originated from charges". I understand that this is the background of his problem. And please see what you say : "EM waves are vacuum solutions to Maxwell's equations, and the asker seems aware of that, so I'm puzzled what the question actually is"
@Danu: I think the confusing thing here is that the gauge/Lagrangian description already has the local symmetry built into it, because it is the right Lagrangian. The quantity conserved under the U(1) without the gauge field is not electric charge!
@ACuriousMind: I believe that John Rennie understood the question the same as I, because I had with him some exchange of comments exactly in this direction - if we can produce (i.e. by reactions) e.m. waves (more exactly photons), without electric charges being involved.
@DanielSank: I can't afford now. There is anti-phase between our times. When is mid-day in your country, it is past mid-night in mine. The best day for me to have a (serious) talk, is Saturday. In other days I am all the time interrupted.
@DanielSank: please see, the problem comes from a certain result of a research of mine. A formula that I obtain there, seems to tell that during the decay, there is intervention of some additional energy. It bothers me whether such a thing can exist. But, let's leave it for Saturday.
Anyway, I took roughly 8 comments to get to the point where I felt the OP should have some sort of child protection official brought to her front door.
She proposed putting a teen girl into space to see if she would survive.
@Sofia: Again, I can't guarantee when I'll be here. Again, my email address is posted on my profile page. You are welcome to start a conversation via email if you wish.
@Danu: Haha, nice. Take that indeed, @ACuriousMind.
Note that this OP is the same.... person... that was whining about the reputation limits for commenting. It seems like OP has turned into an internet troll.
@Sofia: My email is now accessible through my profile page. I apologize to you, as it was not previously viewable to you. There is a link in the personal description. If you follow it you'll find my email easily.
@DanielSank @Sofia: The link is visible. If you click on the "here" part, you are led to a site with quite a few people on it, one of which is our very own Daniel Sank, complete with email adress
Quantum computing is a fantastic field as a physicist because you get to literally play around with fully controllable quantum systems. I feel like this has given me an unusual perspective on quantum mechanics. It feels very much less weird than for some others.
@Sofia: Ah. I was wondering how you were so easily typing greek letters in your answers.
@DanielSank: no, I had prejudgements on TeX., because when I did my 2nd degree in computer engineering I had an advisor that was forcing me to learn LaTeX, which was very much time-consuming with the software of those times. But, now I am using the TeX from the site you indicated, and it's nice.
In 2001, the Russian space station Mir was deorbited and burned up in the atmosphere, after $4.2 billion in expenditures. As it was orbiting within the thermosphere, it was encountering perpetual drag and would have deorbited eventually on its own anyway.
It weighed 129,700 kg in 2001. It's orbi...
@ChrisWhite yeah, that was my thought. If it were generalized to "how could I calculate how many launches of a rocket with thrust $F$ would be needed for...?" then it'd be fine (well, subject to our homework policy and such)
user54412
Overall, I'm not strongly opinionated. I think it would reach a more appreciative audience on Space Exploration for what it's worth. (I know, that shouldn't be worth much in scope decisions, but there it is nonetheless.)
Mods: do you want to be informed if I find a user that seems to want the account deleted (i.e. has "please delete me" as the only thing in the "about me"), but may have forgotten to make a formal request (or whatever it takes for that to happen)?
SE chat has a great previewer for non-SE links like Wikipedia,
For those that are not familiar with arXiv, it is a website/service the hosts pre-print editions of articles in Physics, Mathematics, Computer Science, Quantitative Biology, Quantitative Finance and Statistics. I am occasionally li...
What do you guys think of my question? http://physics.stackexchange.com/questions/151383/solving-special-function-equations-using-lie-symmetries have you ever seen something so beautiful? By the end of this, the special functions will be child's play :D
Imagine taking the Laplace equation, knowing your coordinate system is ellipsoidal, knowing instantly that this will give you 3 separation equations (you can write down based on knowing it's ellipsoidal), then knowing those 3 ode's are basically just an un-factored Lie algebra representation of some conformal symmetry, allowing you to write down the solution using Lie groups instantly, I mean wow! That whole Lebedev book on special functions is just axed in half with baby pictures!
@bolbteppa: Ever since I realized the spherical harmonics are nothing but the representations of $\mathrm{SO}(3)$ I've also always wondered whether such an approach is actually possible in more generality, and if one can get the actually form of the solutions by such arguments. Unfortunately, I've got no answer for you.
Yeah it is possible, it's the subject of geometric representatiion theory as far as I know, and there's a book which unifies all those special functions + gamma function etc... by Vilenkin but it's so big and no pictures
A question has arisen if shopping advice posts is off-topic and should be kept closed.
Examples:
Fairly Broad Spectrum Light Source Options
Refractive index liquids: Why hard to buy?
Where can I get fluidics components?
I realise that this is not a question on physics, but how does one othe...
Is there already a pre-defined feature in SE that allows one to print a post along with its answers and comments in a readable format? I have tried printing the page just via the browser, but it cuts through sentences and answers, and the outputs are usually very ugly (poor formatting). Since the...
Well, I didn't want to go into details. I'm just saying that the picture might be somewhat mixed.
@David Z's answer is partially obsolete because it talks about an old Experimental or Applied Physics proposal, which might have left naysayers with no other option than to vote for Jeff Atwood's answer. Also David Z has a point: Shopping advices are not about physics. Moreover, they are irrelevant to most physics readers.
@KyleKanos: A question was posted "What's the Cause of Quantum Entanglement?" I know what will be the fate of this question - closed because a similar one was answered in the past. So, from the beginning I recommend not to close it, and that, because I answered to it, in detail, as for beginners in the class-room. I was a teacher for long years. Trust me a bit. People welcome very simple and clear explanations, with little mathematics, but very intuitive.
@KyleKanos Can you tell me how do you know that a question has a duplicate? You know since you personally answered it? Or, how else? I would also like to know. Then I will look at the answer, and if it satisfies me, I won't invest time in answering again.
@KyleKanos: I see on the side of the screen with the details of the question, related questions. But, does someone follow after each question? Of course it would be good to stop the same question being repeated and repeated. But, it's a sisific effort to look at each question. Is there some utility that does that automatically?
hey all, question regarding special relativity: if we define t' to be the time in a moving frame, and t to be the time at the stationary object, we know that t = t'/(sqrt(1-v^2/c^2)). what if velocity is changing with respect to time? then, which time is the velocity a function of? would it just be a function of what you can measure? i.e. if you know the velocity of the object from a stationary perspective, then it would be v(t) and not v(t')?
i think this makes sense b/c if we measure the velocity from the moving perspective, the stationary object now is the moving object, and the moving object is now stationary from our perspective
@KyleKanos: can you have a look? I answered a question, thereafter it was put on hold, and I got a -1 without any explanation. Is there a mistake in the utility? Nobody made a remark that my answer is wrong. A -1 without any justification happens to me a lot.
@KiranK. You can define it in whichever frame you want, and you can always transform to the other frame. In practice it would be specified which frame it is originally defined in.
user54412
Also be careful about omitting the x and x' from the Lorentz transformation laws -- once things start moving, you don't always have the option to say "everything happens at x=0 so I can ignore that coordinate"
@Sofia: I think the downvotes are because your formatting is...unorthodox. It is generally disliked to WRITE IN ALL CAPS, just use italics ond boldface to emphasise things. Also, whenever you talk about variables, write them in LaTeX - it makes posts much easier to parse
As to how we know duplicates - when you've been around for a while, you recognize certain question, especially those you have answered. There's no malice in closing something as duplicate - if you think your answer adds to those already present, answer the original question, not the duplicate
@Davidz: Your recent postings about moderator elections have made me curious - who decides when it is time to elect more moderators? Is is purely at the discretion of the SE team, or are there "objective" statistics how many moderatiors a site "should" have?
For example, math.SE has already double the moderators that we have, but I feel the presence of moderators much more strongly here (not in a bad way!) than I do on math.SE
SE chat has a great previewer for non-SE links like Wikipedia,
For those that are not familiar with arXiv, it is a website/service the hosts pre-print editions of articles in Physics, Mathematics, Computer Science, Quantitative Biology, Quantitative Finance and Statistics. I am occasionally li...
A question has arisen if shopping advice posts is off-topic and should be kept closed.
Examples:
Fairly Broad Spectrum Light Source Options
Refractive index liquids: Why hard to buy?
Where can I get fluidics components?
I realise that this is not a question on physics, but how does one othe...
For a couple of dates my reputation is not being updated. Do you have some policy on that?
