I was told the following basic facts:   Objects made of the same metal don’t fuse in the atmosphere because they form an oxide layer. They do fuse in space. Gold doesn’t oxidize.   Yet, gold nuggets held together also don’t fuse (I can pull them apart without resistance). How does each gold atom “know” which object it belongs to?
It is my understanding that metals are a crystal lattice of ions, held together by delocalized electrons, which move freely through the lattice (and conduct electricity, heat, etc.).   If two pieces of the same metal are touched together, why don't they bond?   It seems to me the delocalized electrons would move from one metal to the other, and extend the bond, holding the two pieces together. If the electrons don't move freely from one piece to the other, why would this not happen when a current is applied (through the two pieces)?
When using sudo powers and calling gedit the top level menu with File Edit View Search Tools Documents Help is missing.  If I create user ID root and sign in once and call gedit will it create the necessary user configuration files that might fix this?  Will this also make the annoying error messages go away whenever I use sudo, gksu or pkexec as a regular user with elevated privileges togedit ?  Will there be other benefits with Nautilus and other Gnome derivative Ubuntu applications?  NOTE: by sudo powers you can google pkexec gedit 3.5k hits, gksu gedit 40k hits or sudo gedit 500k hits. I'm in the minority using the first method but I believe it will become the standard in Ubuntu 17.04.    June 12, 2017 Update Here are a list of errors you get when using pkexec gedit:  (gedit:13003): Gtk-WARNING **: Calling Inhibit failed: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.SessionManager was not provided by any .service files  ** (gedit:13003): WARNING **: Set document metadata failed: Setting attribute metadata::gedit-spell-enabled not supported  ** (gedit:13003): WARNING **: Set document metadata failed: Setting attribute metadata::gedit-encoding not supported  ** (gedit:13003): WARNING **: Set document metadata failed: Setting attribute metadata::gedit-position not supported   On this  there is a commitment to fix these distracting messages as of June 5, 2017. No indication is given for when the fix will be upstream nor if the functionality will be implemented or the error messages will simply disappear.  Note the bug report was filed over a year ago and over that time it only effects 18 people. Can I choose to delay my turn in combat? Change footer in beginning of chapters I want the footer of all pages to be "Page N°X" on the right. I used this:  \usepackage{fancyhdr} \pagestyle{fancy} \fancyhf{} % clear all header and footer fields \fancyhead[R]{\leftmark} \fancyfoot[R]{\footnotesize Página N$^\circ$ \thepage\ } \renewcommand{\headrulewidth}{0pt} \renewcommand{\footrulewidth}{0pt}   It works on every page but the chapter beginning ones. My friend and I have been wracking our heads with this one for the past 3 hours... We have 2 point masses, $m$ and $M$ in a perfect world separated by radius r.  Starting from rest, they both begin to accelerate towards each other. So we have the gravitational force between them as:  $$F_g ~=~ G\frac{Mm}{r^2}$$  How do we find out at what time they will collide?  What we're having trouble with is this function being a function of $r$, but I have suspected it as actually a function of $t$ due to the units of $G$ being $N(m/kg)^2$.  I've tried taking a number of integrals, which haven't really yielded anything useful.  Any guidance?  No, this is not an actual homework problem, we're just 2 math/physics/computer people who are very bored at work :) Is there a universal way to turn Windows 7 Aero desktop, all windows, etc into grayscale? I had an option to do this in Intel video drivers on my old laptop, now I have NVIDIA and don't know how to replicate this effect.   There might be a shader or filter that would cause Aero to render stuff into grayscale, but I was unable to find anything. Or must it be explicitly supported by video driver as a bonus? So just now, I had a bug in my site that caused my custom navigation bar's buttons to be sized and spaced incorrectly. I had no idea where this bug came from, and had to search around for awhile to find the answer. It turns out that SharePoint decided it would be a good idea to inexplicably add a few lines of:  nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;  nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;   between my   in my DevHome.aspx (I'm using Angular for this particular project). So, why does Sharepoint do this, and how do I prevent it? This is not the first time SharePoint has randomly added an nbsp to my page.  Thanks in advance. How to evaluate $\int_0^{2\pi} \frac{d\theta}{A+B\cos\theta}$? I'm having a trouble with this integral expression:  $$\int_0^{2\pi} \frac{d\theta}{A+B \cos\theta}$$  I've done this substitution: $t= \tan(\theta/2)$  and get: $\displaystyle \cos\theta= \frac{1-t^2}{1+t^2}$ and $\displaystyle d\theta=\frac{2}{1+t^2}dt$ where $\displaystyle \cos^2\theta/2=\frac{1}{1+t^2}$  then the integral becomes:  $$\int\frac{2 \, dt}{(A-B)t^2+(A+B)}= \sqrt\frac{A+B}{A-B} \arctan \left(\left(\sqrt\frac{A+B}{A-B} \right) t\right)$$   However, I'm not sure about the new limits since $\tan$ has period $\pi$ so what I have to do at this point to decide the new limits? And of course if you find some mistake in what I've done before, please let me know! Struct padding in C++ Downloading large files reliably in PHP How to create a circular shaped grid, similar to a manhole cover I'm working on a python script that passes file locations to an scp subprocess. That's all fine, but I'm in a situation where I may end up concatenating a path with a filename such that there's a double '/ in the path. I know that bash doesn't care if you have multiple file separators, but I'm wondering how exactly that is rectified. Is it bash that strips extra /s or does it really not matter ever?  I ask because it will save me several lines of code to check for extra /s while concatenating. I know it's not a big deal, but I'm curious as well. I have a bash script that has the line cd //usr (instead of cd /usr), which seems to imply there might be a significance to using multiple /s in a path I'd like to output hello world over 20 characters.  printf "%-20s :\n\n" 'hello world!!'  # Actual output hello world!!        :  # Wanted output hello world!!========:   However, I don't want to complete with spaces but with "=" instead. How do I do that? How to smooth shade an object while retaining hard edges? I frequently come to the problem of having a mesh with parts I would like to render smooth and "hard" edges connecting them.   How can I set the mesh to show the sharp edges but render everything else smooth?  In the example I would like the sides of the individual cylinders render smooth but the intersection between bottom and top to be sharp/flat How to use EntityFieldQuery with dates? I need to select entities with specific dates.   How should the following be formatted. Do I need to parse 15-May-2010  Also how I get the error page.   function events2() {  $query = new EntityFieldQuery(); $query   -&gt;entityCondition('entity_type', 'node', '=')   -&gt;propertyCondition('status', 1, '=')   -&gt;propertyCondition('type', 'event')     -&gt;propertyCondition('field_event_date', '15-May-2010', '=');  $result = $query-&gt;execute();   return $result;  } How can I use GDAL to batch define a projection? Where to set proxy ignore list? I upgraded to ubuntu 11.10 from 11.04, shocked to see few things...    My system is behind a proxy, so I did set a proxy setting. Being a web developer, I want to remove a lot of addresses that I type in browser address bar to not hit proxy. There's no such ignore list in ubuntu 11.10, what/where do I do it? What was the requirement to change the way network gui worked? How to use a proxy on the command line? I can set my proxy username and password along with proxy settings in the proxy ui but these settings do not work on the command line. How can I use apps such as wget &amp; ping on the command line with a proxy?  Example Details:   username: 1234 pass: linux proxy: proxy port: 8080 Site specific magic comment links The SourceForge signon page says I can associate an OpenID with my existing SourceForge account:    I enter my currently-signed-in SourceForge account password I select the custom OpenID URL and enter https://openid.stackexchange.com I'm redirected to https://openid.stackexchange.com/account/login?&lt;session key bits&gt; I enter my openid.stackexchange.com login information there I get the error message:     Cannot Complete Login      Detected an attempt to send an assertion when the identifier () is not owned by the logged in user.    I don't understand what that means. A blinding light / blinding sunlight / a blinding sunlight "Mornings came and cast a blinding sunlight over everything, and he felt like nothing worthwhile could be accomplished."  For some reason, I feel like "a blinding light" is ok, but if its sunlight, then I should drop the "a" and write "cast blinding sunlight", but I'm not sure why I feel this way.   Can anyone offer some enlightenment?  edit - alternate phrasing, closer to being a literal translation: "Mornings came without warning, flooding the day with a strong sun, and he felt like nothing worthwhile could be accomplished."   I would still like an answer to the technical question of whether I should drop the "a", but would also appreciate knowing if anyone thinks option #2 is a better choice.