I studied that the EM waves run through the space, with each electric field and magnetic field oscillating and inducing each other. And I had thought-experiment that it could be possible to make EM waves with manual steps(or mechanical) -  shaking permanent magnet or electrificated sticks. Is it possbile enough to make EM waves in the way i assumed? If it is, please hyperlink the related research.
If I wave around a bar magnet, the magnetic field in the space around it changes. Is this enough to go through the whole speed of light derivation implying that the motion creates an electromagnetic wave? If so how do I determine the wavelength and direction of the resulting wave?
Height of an HTML select box (dropdown) Can someone confirm that its not possible to change the height of a dropdown that is shown when you click on a select box.   The size attribute of the select makes it look like a list, the height attribute in the CSS doesnt do much good either. This started to happen immediately after I had rebooted the first time after doing a system upgrade. It first starts with a dialogue that says "System program problem detected". Then when I try to hit 'report problem' not much happens. I am led through a dialogue that always ends up the problem cannot be solved.  I am aware this is not a lot of information, however I'm not sure which information I need to publish and how should I obtain it to debug this problem.  Here's a screenshot! How do I copy a property from an active object to selected objects? I have been using the Copy Attributes add-on to copy some properties from active object to selected objects. This add-on is not enabled by default and must be explicitly enabled. But its a very useful workflow enhancing tool.    There is a limitation though. Not all properties can be copied and even those that can be copied are copied in groups (Its hard-coded in to the add-on).  My question is if there is a built-in feature or any another other way to copy any property from the active object to the selected objects? Area of an irregular polygon Does infinity exist in physical systems? Light clock with mirrors on a moving train "Who to follow" or "whom to follow"? has a "who to follow" button on the upper side of the screen. Shouldn't it be "whom to follow"?   suggests that whom is the correct usage in a case like this. Motivated by :   Which finite groups are the group of units of some ring? Which finite groups are the group of units of some finite ring? Which finite abelian groups are the group of units of some commutative ring? Which finite abelian groups are the group of units of some finite commutative ring?   It  that even for fields this is not simple to answer.  I expect the general question (Which groups are the group of units of some ring?, with no finiteness hypotheses) is even harder. Best way to center a  on a page vertically and horizontally? Let the ring of fractions be denoted as $S^{-1}R$.       Proposition (from Robert Ash's textbook "Basic Abstract Algebra")      Define $f: R \rightarrow S^{-1}R$ by $f(a) = a/1$. Then f is a ring homomorphism. If S has no zero divisors then f is a monomorphism, and we say that R can be embedded in $S^{-1}R$. In particular:      (i) A commutative ring R cna be embedded in its complete (or *full) ring of fractions ($S^{-1}R$, where S consists of all non-divisors of zero in R).       (ii) An integral domain can be embedded in its quotient field.    Why does the proposition say "If S has no zero divisors..."? If S really had zero divisors, then this wouldn't even be properly defined, right? Because we would have a/0 for some a in R. Summoning an item in 1.9 with motion When I put   /summon Item ~ ~2 ~ {Item:{id:"minecraft:diamond",Count:1b,Motion:[0.0,0.8,0.0]}}    in a command block, it summons the diamond with Count:1b but it doesn't follow the Motion Tag. Does anyone know how to get the Motion Tag working? Is there any uncountably infinite set that does not generate the reals? Does there exist an uncountably infinite set $X \subseteq \mathbb R$ such that $\mathbb R \neq \left&lt;X\right&gt;$? I can't think of any, but I'm also having trouble trying to prove that no such subset exists.  For example: $\mathbb R$ is uncountable and obviously $\mathbb R = \left&lt;\mathbb R\right&gt;$. The Cantor set $C$ is uncountable, and we know that $C - C = [0, 1]$, so then since $\mathbb R = \left&lt;[0, 1]\right&gt;$ we know that $C$ also generates $\mathbb R$. Also the set of irrationals $\mathbb R \setminus \mathbb Q$ is uncountable, but we can generate all the rational numbers by fixing one irrational number $\alpha$ and then saying the any rational number $x$ shall be $(\alpha + x) - \alpha$, since both $\alpha + x$ and $\alpha$ are irrational.  So the examples that quickly come to mind all generate the reals. Is there a simple counterexample? I am wondering how to show that $\mathbb{Z}[\sqrt {10}]$ is not a UFD.    My only idea is to show that there are two factorizations of $10$, say, $ab, uv$ such that $a$ is not a unit times $u$ or $v$. In this ring $10=2\cdot5=\sqrt {10}\cdot \sqrt {10}$, so it suffices to show $2$ is not a unit times $\sqrt {10}$. Suppose $2=\sqrt {10}(a+b\sqrt{10})=a\sqrt{10}+10b$. Then $a=0$ since $\sqrt{10}$ is not rational. So $10b=2$, which has no integer solutions. So $\mathbb{Z}[\sqrt {10}]$ is not a UFD.  Is my reasoning correct? What are the flaws? So I am using cryptopp to encrypt a file in a project and I am using AES-GCM. I have a 256bit key and a 128bit ivec and a 128bit tag that I use to encrypt files.  However, I want to know where the authentication tag is stored? I notice if I specify a tag size of 0 then the encrypted file size is the same number of bytes as the original file.  Is the authentication tag simply appended to the end of the file? register_nav_menus() won't register menus Please help with menu registeration:  I have followed this guide (http://codex.wordpress.org/Navigation_Menus) step by step.  Added the following code to functions.php:  function register_my_menus() {   register_nav_menus(     array('header-menu' =&gt; __( 'Header Menu' ) )   ); }  add_action( 'init', 'register_my_menus' );   But the guide says that this will make the menu appear in the Appearance -> Menus admin screen in the "Theme Locations" box as "Header Menu".  When I go to Appearance -> Menus everything is greyed out and there is no option of "Theme Locations" When do I use "I" instead of "me?" Is it ok to put old papers on the arXiv? In my field (I am a condensed-matter theoretical physicist) it is such a normal thing to put papers on the arXiv, that people sometimes look at other people's arXiv list of papers instead of their publication record to get to know what they do, etc.  It just so happens that a few years ago I did a PhD with a supervisor that does not like the arXiv that much (he apparently had some conflict with some authors of a paper that was very similar to one of his papers, but one was already published while the other was just an arXiv preprint -or something like that). As a result, from my list of less than 20 publications, there are four of them from my PhD that are missing on the arXiv.  I was thinking of submitting the latest versions I have of them as arXiv preprints now, four years after their publication. For this I already have the agreement of all co-authors (including my supervisor), and all the journals involved seem to allow to put preprints of the material they publish. Do you see any problem with this? I fear that some people might take it as a way to advertise as new something that was already published a long time ago (though I would of course give the full reference to the published version). There may be other issues I am not aware of. The reason why I would like to do this is that I am applying for fellowships, positions, etc. and I am afraid some of my (best) publications may go unnoticed if somebody looks me up on the arXiv.  Thank you, Stephen Newtonian mechanics: massless particles ASP.NET MVC Relative Paths In my applications, I often have to use relative paths. For example, when I reference JQuery, I usually do so like this:  &lt;script type="text/javascript" src="../Scripts/jquery-1.2.6.js"&gt;&lt;/script&gt;   Now that I'm making the transition to MVC, I need to account for the different paths a page might have, relative to the root. This was of course an issue with URL rewriting in the past, but I managed to work around it by using consistent paths.  I'm aware that the standard solution is to use absolute paths such as:  &lt;script type="text/javascript" src="/Scripts/jquery-1.2.6.js"&gt;&lt;/script&gt;   but this will not work for me as during the development cycle, I have to deploy to a test machine on which the app will run in a virtual directory. Root relative paths don't work when the root changes. Also, for maintenance reasons, I cannot simply change out all the paths for the duration of deploying the test - that would be a nightmare in itself.  So what's the best solution?  Edit:  Since this question is still receiving views and answers, I thought it might be prudent to update it to note that as of Razor V2, support for root-relative urls is baked in, so you can use   &lt;img src="~/Content/MyImage.jpg"&gt;   without any server-side syntax, and the view engine automatically replaces ~/ with whatever the current site root is. Is there a dollar amount that, when adding Massachusetts Sales Tax, precisely equals $200?