I understand that the gravity has to have a pull greater than the speed of light, but I thought that when gravity pulls light it doesn't accelerate it only blue-shifts it. So then why does gravity only pull light in when it has a g force greater than its velocity?  Also is there any evidence that gravity blueshifts light
In  (ignoring Hawking radiation), why is a  black? Why nothing, not even light, can escape from inside a black hole? To make the question simpler, say, why is a  black hole black?
Explicit formulas for Stirling numbers of second kind I have seen some recursive formulas for Stirling I and II kind but I am especially interested in explicit formulas.  I was thinking and get: $$ \left\{ {m \atop n} \right\} =  \sum_{k_i&gt;0 \wedge k_1+k_2+...+k_n = m} \frac{m!}{n!}\cdot \frac{1}{k_1! \cdot k_2! \cdot ... \cdot k_n!}$$ I am not sure if it is ok but supposedly it is (I created it with combinatorics interpretation)  Can somebody look at that and tell me if it is ok/wrong?  By the way,if you have some nice formulas, I will be grateful for sharing that. Is $\sin \infty$ an indeterminate form? I had a  over what seems like a simple question:     Is $\sin \infty$ an ?   What do you think? :)    I'm labelling this as (soft-question) to be safe, but it should have a clear answer depending on the definition of indeterminate form used. The term "indeterminate form" is seldom used in post-calculus mathematics, but I believe it has one or more accepted definitions, which are either informal or formal. So any answer which takes a standard definition and argues the case would be interesting to me.  How to make a good answer:   State the definition of indeterminate form, either from an online or textbook source, or a definition you came up with on your own. Determine, using your stated definition, whether $\sin \infty$ is indeterminate or not.   EDIT: What do I mean by $\sin (\infty)$?  It's not a well-defined expression, but neither are any of the other indeterminate forms: $\frac{0}{0}$ doesn't exist, $1^\infty$, doesn't exist, and so on. So the question is whether this expression -- which is not well-defined, just like any other indeterminate form -- is an indeterminate form. Windows Starter Edition, Home and Home Premium do not include gpedit, how do I install it? I want to make some changes to Windows that require using the Group Policy Editor (gpedit.msc).  Unfortunately the Group Policy Editor is not included with the Starter Edition, Home and Home Premium editions of Windows.  How can I install it? Is there a size of rectangle that retains its ratio when it's folded in half? A hypothetical (and maybe practical) question has been nagging at me.  If you had a piece of paper with dimensions 4 and 3 (4:3), folding it in half along the long side (once) would result in 2 inches and 3 inches (2:3), which wouldn't retain its ratio. For example, here is a piece of paper that doesn't retain its ratio when folded:   Is retaining the ratio technically possible? If so, what is the side length and ratio that fulfills this requirement? Any help would be appreciated.  Update:  I added "once" because I got an answer saying that any recectangle would work, as any rectangle folded twice has the original ratio. Nice answer, but not quite what I was looking for. As for the other answers, I got 3x as much information as I needed! Thanks! Can you reuse marinade used with raw chicken? I marinated chicken a couple weeks ago, and stored the marinade afterwards in a jar. Can it be reused, or is that dangerous? I've been told conflicting stories here. The marinade is mostly teriyaki if that makes a difference.   Intended use of used marinade: Marinate chicken which will then be cooked in the oven. It will not be used with anything that won't be cooked (like a sauce). How to enable Hyper-V in Windows 8 I've got a Windows 8 (not .1, not Pro; OEM with a Lenovo Z580 laptop), which I want to use for WP8 development.  I've read  and , and a few more articles.  I have enabled in BIOS what looks like it has to do with hardware virtualisation - "Intel Virtual Technology" (is this VMX?). No signs of EPT or XD.  I've got the four Hyper-V items in the enumeration that msinfo32 shows.  However, in the 'Control Panel/Programs and Features/Turn on|off windows features' list, I don't have Hyper-V.  Is this available at all on my machine, and if not what can I do to get it working?  Thanks in advance. Find $|(\mathbb{Z} \oplus \mathbb{Z}) / \langle(3,6)\rangle|$ and determine if its cyclic Showing that $f$ is identically $0$ on $\mathbb{D}$ Here is the question: Let $f:\mathbb{D}\rightarrow\mathbb{C}$ be an analytic function.  Suppose that there exists $\epsilon&gt;0$ such that for every $\theta$, $|\theta|&lt;\epsilon$, and $\lim_{z\rightarrow e^{i\theta}}f(z)=0$.  Prove that $f$ is identically $0$ on $\mathbb{D}$. My thoughts:  Well, honestly, I am quite stumped here.  I was thinking I could let $f$ be analytic in some other region (can I even do this?), say the lower half plane and suppose $\lim_{z\rightarrow x}f(z)=0$ whenever $-1\leq x\leq1$, by assumption.  Maybe then I could show that $f$ is identically $0$ on the bigger region, and then consider $f$ on the intersection of those two regions, and then ultimately making my way towards using the uniqueness theorem to show what I want... but I am quite stuck on how to do that... any thoughts, suggestions, etc. are greatly appreciated!  Thank you. jQuery Datepicker with text input that doesn't allow user input I was wondering if there are any alternatives to  tools.  Thinking about it for a bit, I think the only alternative is to use R or RPY to do the analysis.   Basically I'm trying to solve routing problems based on nonPostGIS databases. As most of my data is actually stored in a different format; however, it's not to hard to convert. I'm finding that pgRouting to my dumb silly brain is difficult to implement. So perhaps a non-database solution that I can easily tweak would be ideal for me Automatically switch gpu graphics driver when gaming I have installed Ubuntu GNOME 15.10. I installed the nvidia tested proprietary driver and then I restarted. Afterr that I selected as primary GPU the Intel driver for normal use. However, when I enter a steam game(Portal) the graphics is bad so In order to play normal I have to switch manually to the nvidia driver again and reboot again. After the game I have to manually select as primary driver the Intel one and reboot again. It is so boring. QUESTION: How to automatically switch gpu graphics driver when I enter a game or something that needs more GPU? "Planar" graphs on Möbius strips When do you use “learnt” and when “learned”? Is learnt UK English and learned US? Is it that simple?  I’m used to using learnt, but my US spellchecker says it is wrong. Bonferroni adjustment in SPSS - what does it do? Animated textures don't work in Blender viewport playback I am trying to animate in 2d. I do it with planes that have textures on them. I recently came up with the idea of having a plane with an image sequence of mouths because animating actual lip syncing by hand takes too long and isn't really necessary for what I'm trying to acomplish. However, when playing back the animation in textured viewport shading the animated texture stays at the last frame until the animation stops. I can use the arrow keys and it works fine as well as scrubbing through the timeline, just not when playing back the animation with alt+a. Can anyone help me with this problem? How do I remove "permission denied" printout statements from the find program? Code   find / -name netcdf   Output  find: `/root/.dbus': Permission denied find: `/root/.gconf': Permission denied find: `/root/.gconfd': Permission denied find: `/root/.gnome': Permission denied find: `/root/.gnome2': Permission denied find: `/root/.gnome2_private': Permission denied This may be a stupid or trivial question, but I am new to Ubuntu, and have two unsolved problems (flashplayer doesn't play, and scanner doesn't work - in virgin install 13.04), so I started to search in documentation. In the 13.04 specific web site I was browsing the hardware section, and came across something like this: "Open Dash, and select Disk Utilities".  So what is Dash, and where is Disk Utilities?  The application finder could not find any of those. In terminal the "dash" command seems to invoke some sort of a shell. Do lure modules and incense cause new pokemon to spawn near you, or existing pokemon to be drawn to you? Multiple Author and email with location? I am trying to add multiple Author with their email and location but not working.  I am trying to get something like this     first_person^1 , second person^2, third_person^3            {1^mail, 2^mail, 3^mail}@gmail.com                   institution name                      location Plot draws list of curves in same color when not using Evaluate