There is an existing question  which has a complex answer, not accessible to the layman.  The point of this new question is that the electromagnetic field is mediated by photons. Yet photons emitted at the surface of a black hole (of a large enough mass) will not be able to escape beyond the event horizon.  Would a large black hole have no measurable electric field beyond its event horizon, even if it carried a high charge at its surface?
By the "No Hair Theorem", three quantities "define" a black hole; Mass, Angular Momentum, and Charge. The first is easy enough to determine, look at the radius of the event horizon and you can use the Schwarzschild formula to compute the mass. Angular Momentum can be found using the cool little ergosphere Penrose "discovered". However, I don't know how to determine the charge of the black hole.   How can an electromagnetic field escape the event horizon of a Reissner-Nordström black hole? Is there any experiment we could theoretically do to a black hole to determine its charge?
In normal line integration, from what I understand, you are measuring the area underneath $f(x,y)$ along a curve in the $x\text{-}y$ plane from point $a$ to point $b$.  But what is being measured with complex line integration, when you go from a point $z_1$ to a point $z_2$ in the complex plane?  With regular line integration I can see $f(x,y)$ maps $(x,y)$ to a point on the $z$ axis directly above above/below $(x,y)$.  But in the complex case, when you map from the domain $Z$ to the image $W$, you are mapping from $\mathbb{R^2}$ to $\mathbb{R^2}$ ...it is not mapping a point to 'directly above/below'...so I don't have any intuition of what is happening with complex line integration. How to prevent page breaking for lstinputlistings? Do matrices $ AB $ and $ BA $ have the same minimal and characteristic polynomials? Let $ A, B $ be two square matrices of order $n$. Do $ AB $ and $ BA $ have same minimal and characteristic polynomials?   I have a proof only if $ A$ or $ B $ is invertible. Is it true for all cases? How to be granted root rights while browsing files/directories with Nautilus I'd like to know if there a way to be granted root rights while using Nautilus 2.30 ?   For example I'd like to move some old folders of long unused users from the home directory - remains of previous distros (Debian).   Of course I can open a terminal, but I want to know if it is possible to do that with a mouse in Nautilus. I have a select control, and in a javascript variable I have a text string.  Using jQuery I want to set the selected element of the select control to be the item with the text description I have (as opposed to the value, which I don't have).  I know setting it by value is pretty trivial. e.g.  $("#my-select").val(myVal);   But I'm a bit stumped on doing it via the text description. I guess there must be a way of getting the value out from the text description, but my brain is too Friday afternoon-ed to be able to work it out. Forge CBC-MAC by creating a new message, given the MAC of two messages Why can't I cd to a quoted tilde ('~')? Writing my first script so I'm sure this is a basic question, but can someone please explain to me why I can:  cd ~ cd bin cd ~/bin cd 'bin'   But not  cd '~' cd '~/bin'   I need to cd to a directory path with a space in one of the directory names, so I need the quotes (it's Windows Program Files under wine). I can get around it with two cd commands, but why can't I put ~ in quotes?  If I type cd '~' (or cd "~") I get:  bash: cd: ~: No such file or directory Career Change in to Testing I've around 10+ years of experience in Banking operations including  reconciliations, sales, customer services, asset management, and financial transaction QA.  Coming to academics I've done my PG in commerce (costing, auditing, banking, and statistics) also a diploma in project management, ISTQB foundation, Prince 2 foundation and ITIL foundation.    Can any one advise me if the testing role is ideal for me and how to start with it. $a, b, c$ are positive real numbers.   Prove that $$8abc\le (a+b)(b+c)(c+a)$$  I haven't really gotten anywhere, just tried to open up $(a+b)(b+c)(c+a)$ and got null. Traffic (views, visits) is not correctly registered on Site Analytics or Area 51 In the ,  can monitor some things like the total traffic on the site. However, it seems to be broken at the moment, all figures are almost zero. This is how it looks for Meta Stack Exchange (other sites show similar pictures): How are parameters evaluated for a Plot in Manipulate I have come across both the phrases - 'on the internet' and 'over the internet.'   I'm pretty sure that both are correct but then which to use when?  Please note, I'm well aware of all over the Internet which I'm not concerned about. Which past tense of "to light" should I use here? I know that there are two ways to form the past tense of to light (i.e. lit/lighted). Which one is appropriate for the sentence below?     His thoughts lighted our way.   or     His thoughts lit our way. How to install Flash player on Ubuntu? Even though I have the latest Adobe Flash player 11.2 for Linux in Firefox -   - a particular online flash game still requests that I update to the latest flash player.  I've tried this online game on my laptop (Windows 8 with Flash Player 11.8) and it has no problems.  Is there a way to trick Ubuntu or this game into thinking Flash Player 11.8 is "installed"? Microsoft has steadily improved its operating cash flows in the past three years. Microsoft has steadily improved its operating cash flows in the last three years. Microsoft has steadily improved its operating cash flows for the past three years. Microsoft has steadily improved its operating cash flows for the last three years. Microsoft has steadily improved its operating cash flows for the past three years. (&quot;for&quot; omitted) Microsoft has steadily improved its operating cash flows for the last three years. (&quot;for&quot; omitted) Microsoft has steadily improved its operating cash flows during the past three years. Microsoft has steadily improved its operating cash flows during the last three years. Microsoft has steadily improved its operating cash flows over the past three years. Microsoft has steadily improved its operating cash flows over the last three years.  Which of them are idiomatic and preferred? Are they interchangeable? How can one differentiate between Dr. (PhD) and Dr. (MD or DO)? Integer solutions for $x^2-y^3 = 23$. As the title stated, I am wondering the integers $x,y$ that satisfy the equation $x^2-y^3 = 23$. How do I use reflection to invoke a private method? There are a group of private methods in my class, and I need to call one dynamically based on an input value. Both the invoking code and the target methods are in the same instance. The code looks like this:  MethodInfo dynMethod = this.GetType().GetMethod("Draw_" + itemType); dynMethod.Invoke(this, new object[] { methodParams });   In this case, GetMethod() will not return private methods. What BindingFlags do I need to supply to GetMethod() so that it can locate private methods? Boxplot interpretation: is it correct that a boxplot is missing a whisker? Use Complete Induction of set theory to prove $\frac{1}{\sqrt{1}} + \frac{1}{\sqrt{2}} + \frac{1}{\sqrt{3}} + ... + \frac{1}{\sqrt{n}} > \sqrt{n}$. Proove by the Complete Induction for every $n\in \mathbb{N}, n \geq 1$ $$\frac{1}{\sqrt{1}} + \frac{1}{\sqrt{2}} + \frac{1}{\sqrt{3}} + ... + \frac{1}{\sqrt{n}} &gt; \sqrt{n}$$.  I know only the basis - $\frac{1}{\sqrt{1}} \geq \sqrt{1}$.  But, I dont know how to do the change from the regular induction to the induction of Set theroy(Complete Induction).