I understand that a general interpretation of the $1/r^2$ interactions is that virtual particles are exchanged, and to conserve their flux through spheres of different radii, one must assume the inverse-square law. This fundamentally relies on the 3D nature of space.  General relativity does not suppose that zero-mass particles exchanged. What is the interpretation, in GR, of the $1/r^2$ law for gravity? Is it come sort of flux that is conserved as well? Is it a postulate?  Note that I am not really interested in a complete derivation (I don't know GR enough). A physical interpretation would be better.  Related question:
The Newtonian description of gravity can be formulated in terms of a potential function $\phi$ whose partial derivatives give the acceleration:  $$\frac{d^2\vec{x}}{dt^2}=\vec{g}=-\vec{\nabla}\phi(x)=\left(\frac{\partial\phi}{\partial x}\hat{x}+\frac{\partial\phi}{\partial y}\hat{y}+\frac{\partial\phi}{\partial z}\hat{z}\right)$$  However, in general relativity, we describe gravity by means of the metric. This description is radically different from the Newtonian one, and I don't see how we can recover the latter from the former. Could someone explain how we can obtain the Newtonian potential from general relativity, starting from the metric $g_{\mu\nu}$?
I have a raster aerial photo.  I have county wide parcel data.  I want to clip/screen shot the raster at each individual parcel.  Think of this application - a post card with an image of your house --here is your house--  I want to have each parcel attribute to contain information + hyperlink of the aerial photo.  Any other solutions welcome, but this is the only method I could think of. Although I am unsure of how to achieve it efficiently.  Using ArcInfo 10. It seems that I'm missing something about this.  First of all, the series is convergent: $\lim_{n\rightarrow\infty}\frac{2^{-n-1} (n+1)^2}{2^{-n} n^2}=\frac{1}{2}$ (ratio test)  What I tried to do is to find a limit of a partial sum $\lim_{n\rightarrow\infty}S_n$ as follows: $S_n=\frac{\frac{1}{6} n (n+1) (2 n+1)}{\frac{1-\left(\frac{1}{2}\right)^n}{2 \left(1-\frac{1}{2}\right)}}$. Still, the limit is $\infty$ and I'm clearly doing something wrong. Is it grammatically  wrong  to say      It's been too hot  in the last / the past few days      It's been too hot for the last / the past few days     I saw this following sentence also, can we omit in it?     He's had two new cars in the last / in the past three years   as     He's had two new cars  the last / in the past three years     Is there a strict rule in using of preposition or non-preposition when we use the last/past ?  What is the structure when I refer to weeks, months ? I am trying to determine the size in bytes of the contents in a VARBINARY(MAX) field in SQL Server 2005, using SQL. As I doubt there is native support for this, could it be done using CLR integration? Any ideas would be greatly appreciated. If you give a user sudo privileges how can I remove the sudo privileges and make the user become just a regular user?  I used:  sudo adduser username sudo   Now I've changed my mind. Unable to SSH to my virtual machine via Windows Power Shell ISE Why isn't there a truly unified package manager for Linux? Why isn't there a unified package manager that acts as an interface between the end-user and the underlying low-level package manager (apt, yast, pacman, etc.)?  Is it hard to do and therefore not practical, or is there a genuine obstacle making it impossible to do? Why AccessViolationException cannot be caught by .NET4.0 "Software Updater" & "Software & Updates" not working I havent used my Ubuntu for quite a long time.  Today, when I booted Ubuntu (14.04 LTS), the software updater and Software &amp; Updates (from Settings) are not working.  The software updater's window will show up for around 1 sec, but it will close automatically. Software &amp; Updates is never shown, no matter how many times I click the icon. Note that neither of them show any error message.  Those 2 features were working perfectly the last time I used Ubuntu. I want to do some system upgrade and update.  For now, I use sudo apt-get update &amp;&amp; sudo apt-get upgrade. This command runs very fast, meaning (I think) my Ubuntu is not updated properly. The update from software updater always has a big size hence the download should be slower.  What should I do?   Can I just uninstall and reinstall both of them? If I can, how to do it?  Just to clarify, I don't want to upgrade my Ubuntu version (I want the LTS one), I just want to upgrade the software/packages I used.  Thanks for your time. Fantasy book, YA, Girl with magical powers & tattoos I read this book series in middle school. I believe that it would be classified as young adult fiction/fantasy. A girl has magical powers, and with her growing powers comes runes/tattoos in her arms. This is shown on every book cover. I know that one cover is blue. This one shows the girl in a black tank top and black pants. One is a yellow cover, with her in a dress (I think).  The girl has a friend/mentor, who she develops feelings for. The girl is the key to stopping a war between multiple factions/people. Each side is trying to use her to their advantage. I think the series was written in the early 2000s. Is using Gravatar a security risk? This has been . It is unfortunate the accepted answer is so far from reality.   There are some facts:    's MD5 hash is an unsalted MD5 hash of an email address. A 3rd party could harvest every MD5 hash for every user's email on Stack Overflow.  The 3rd party could store all the hashes in a lookup table Email addresses are usually of a very particular format The attacker could start with a brute force of @gmail.com followed by @yahoo.com, etc. The attacker has the advantage that he/she could attack a huge set of emails in one go. So instead of needing to brute force every email individually the attacker can brute force in bulk.   The algorithm is quite simple, calculate a "random" MD5, look it up in the lookup table.       Is Gravatar a big enough security risk to warrant caching images locally?     Examples:    Someone could harvest about 50k email addresses quite easily and shoot off a bogus promotion from Stack Overflow to all the users. A spammer/stalker/generic evil guy can tie you identity to all the rest of the sites that use Gravatar. I am new to the amsart document class. For some reasons \author (etc..) is not showing after I use \maketitle. This is my tex:  \documentclass[12pt,reqno,a4paper]{amsart}  \usepackage{amsmath} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{mathrsfs}  \usepackage{amsthm}  \usepackage{latexsym}  \usepackage{pictexwd} \usepackage{pdftricks} \usepackage{natbib} \usepackage{setspace} \usepackage{color} \usepackage[affil-it]{authblk}  \begin{document}  \title{Temptation, Asymmetric information and Committment}  \author{Mark}  \affil{University of Leicester}  \date{February 2014}  \maketitle  \begin{abstract} To be written \end{abstract}  \section{introduction}  ...  \end{document}   and this is the output:   can anybody help me out? From time to time I come up with ideas of actions I'd like to have available in the context menu of Nautilus. How do I add them there? Is there something like a Thunar UCA plugin for Nautilus? JSF doesn't support cross-field validation, is there a workaround? 123.SOGOU.COM - trojan horse in ukui-screensaver Is there a rule in British English about how to pronounce "either"? List only regular files (but not directories) in current directory "Requires 50 reputation" to comment on deleted posts So I recently saw add comment (requires 50 reputation) on a deleted answer. After looking around a bit, it seems to be on all deleted posts now (only deleted posts, normal posts still say just add comment).  I'm sure it wasn't there before (I think it just said add comment (unclickable) or possible nothing).  It is also on , presumably the root cause is the same.  And yes, I do have more than 50 reputation (in case anyone was wondering).  Just to clarify, requires 50 reputation obviously shouldn't be there for users with 50 or more reputation. Choices:   Display nothing Unclickable add comment - probably not ideal Unclickable add comment (disabled for deleted posts) or something along those lines   FYI - You may be somewhat confused right about now if you can't  yet. How to forbid keyboard shortcut stealing by websites in Firefox Many websites, especially everything involving rich text editing (this site is guilty as well), steal keyboard shortcuts normally used to control Firefox and make them do something else instead. It is totally infuriating when I press something like Cmd-number, Cmd-L, Cmd-T, or Cmd-K and it doesn't do what I want it to. Can I make it stop?  Actually, it would probably be for the best if I could forbid stealing of all Cmd-* shortcuts. I've never seen them used for anything useful. Is it possible? shortcut for commands I use following commands very often, and they're too long.  sudo /etc/init.d/kerio-kvc start sudo /etc/init.d/kerio-kvc stop   how can I create a shortcut command for them? something like sudo kerio start or sudo kerio stop