Why can protons collide?
Do particles ever touch each other during a collision?
Linked account +100 rep bonus also applied to account with 200 Objective-C - When to use 'self' Editing a question with only a JSFiddle link does not work I can't edit a question that has a jsfiddle link because it has a lack of code. Can we get privileged users able to bypass restriction? The question had some really poor formatting and linking and I couldn't fix it. :  Html is not taking the css code Some of my html tags are not reacting by the css which i gaved them for example is offerbox not reaction to the html part. all html parts down from offerbox are not taking the styles that i gaved the enter code here http://jsfiddle.net/8Bw7M/  pic from the html and css  I feel that as a privileged user, I should be able to make the changes needed. This is related, but I'm not adding any new links. How do I redirect www to non-www in Route53? I host my site at domain.com.  My DNS entries in Route53 are as follows:  domain.com      A       xxx.xxx.xxx.xxx      300 domain.com      NS      stuff.awsdns-47.org  172800 domain.com      SOA     stuff.awsdns-47.org  900   I would like to redirect traffic from www.domain.com to domain.com, as currently this just returns a 404.  suggested a PTR record, and I added that:  www.domain.com  PTR     domain.com           300   but it didn't work. What should I be doing? When learning a new subject, I would frequently use lecture notes found somewhere in the Internet. When writing a paper (or a master thesis, as in my case, but the rules should be similar, I believe) one should give some reference for used results which are not common knowledge, if I understand correctly. This make me wonder: what do I do if I want to reference a result I found in some notes?  The natural thing to do would be to just add these notes to bibliography. What format would be preferable for this? Note that there will generally not be much publishing information, perhaps not even a definite year and place. (A BibTeX template would be .)  Secondly, is it OK to cite such materials as a reference? Finding an angle within an 80-80-20 isosceles triangle The following is a geometry puzzle from a math school book. Even though it has been a long time since I finished school, I remember this puzzle quite well, and I don't have a nice solution to it.  So here is the puzzle:    The triangle $ABC$ is known to be isosceles, that is, $AC=BC$. The labelled angles are known to be $\alpha=\gamma=20°$, $\beta=30°$. The task is to find the angle labelled "?".  The only solution that I know of is to use the sine formula and cosine formula several times. From this one can obtain a numerical solution. Moreover this number can be algebraically shown to be correct (all sines and cosines are contained in the real subfield of the 36th cyclotomic field). So in this sense I solved the problem, but the solution is kind of a brute force attack (for example, some of the polynomials that show up in the computation have coefficients > 1000000). Since the puzzle originates from a book that deals only with elemetary geometry (and not even trigonometry if I remember correctly) there has to be a more elegant solution. How to convert strings into integers in Python? What's the purpose of cycling gloves? I haven't cycled for many years already and long ago when I was cycling I didn't pay much attention to equipment. Now I see that many cyclists wear a certain kind of gloves - that only cover the palm and leave the fingers uncovered.  What's the purpose of wearing such gloves (and not usual gloves for example)? In what non-cycling activities can such gloves be useful? If $p$ is a prime such that $p≡1\pmod 7$ then $p ≡1\pmod{14}$ Prove or disprove the following:  1)  if $p$ is odd prime such that $p≡1\pmod 7$ then $p ≡1\pmod{14}$  2)  if $p$ is odd prime such that $p≡4 \pmod 7$ then $p ≡4\pmod{14}$  I think that both statement are true and have a similar proof  1) $p≡1\pmod 7$ so $p≡8\pmod 7$ then $7|p-8$ so $p-8= 7 k$ where $k$ is an integer so $p=8+7k$, so $p ≡1\pmod {14}$  It is that a correct proof? Thank you. How can I make LightDM the default display manager? I have LightDM installed and can start it with sudo start lightdm. But at boot, GDM is still the default. How can change this so LightDM is loaded automatically at boot instead of GDM? How does long-distance space travel work in the MCU? In Guardians of the Galaxy vol. 2, we see long-distance space travel. It involves piloting your ship into some sort of "jump point" that opens up in space, taking the shape of a honeycomb-like structure with a single hex missing.  The way it's describe, these points are fixed in space: early in the movie, the Guardians have to out-run an enemy fleet to reach the one they need; later on, we see them fly through a very long series of them in sequence. It's also made clear that doing too many of these "jumps" in a row has consequences for the passengers.  The process seems to be similar to, say, the Mass Effect relay setup, mixed with a bit of Star Wars hyperspace travel.  Is this the first time we have seen long-distance space travel in the MCU? Is there anything from the source material that explains how this works from a logistical standpoint? If there's any information on the "science" behind it, that would also be helpful. Zero dimensional points do not take up space, so then wouldn't everything in the universe be literally empty? Or is there something that I'm missing? Why is \[ ... \] preferable to $$ ... $$? How do I set environment variables? I'm trying to set up Apache Tomcat on my pc, and it wants me to set up an environment variable for CATALINA_HOME.  Does any know how to do this? What causes the dimensions of a star increase when its hydrogen fuel is exhausted? Inequality involving Euler-Mascheroni constant I would like to solve the following problem from 'Real Analysis and Foundations' by S. Krantz.  Let $a_n = 1+\frac{1}{2} + \frac{1}{3} + \cdots + \frac{1}{n} - \log{n}$ and $\gamma$ be the Euler-Mascheroni constant. Show that $$\vert a_n - \gamma \vert \le \frac{C}{n}$$ for some universal constant $C&gt;0$.  I have no clue how to solve this problem. From searching various sites it seems that $C=\frac{1}{2}$ but I am not sure with this, too. Thanks in advance. $\lim\limits_{n \to{+}\infty}{\sqrt[n]{n!}}$ is infinite How to change default window background color in Windows 10? In Windows 7 and Windows XP it was very easy to change the default background color of all windows to whatever you want. Staring at white window backgrounds all day is hard on the eyes. Once changed, ALL windows of all apps would conform to the custom color as long as the apps allowed the windows bg to be invoked. So for example it worked great in Notepad and many other apps.   Then the geniuses at M$ decided that this feature was no longer needed in Windows 8, and removed it. There were some reg hacks, but nothing standard. I remember reading that the feature would be coming back in Windows 10, but I'm not finding this to be the case. The only [partial/broken] way I have found to be able to do this is to tweak the following registry keys:  [HKEY_CURRENT_USER\Control Panel\Colors] "Window"="227 221 191"  [HKEY_CURRENT_USER\Control Panel\Desktop\Colors] "Window"="227 221 191"   When I changed those keys to my chosen soothing color and rebooted, it worked ONE TIME. After every reboot thereafter, all the white backgrounds are back AND YET those registry keys still have my custom RGB codes. I really hate Microsoft right now, but that aside, is there any solid way to change windows 10 bg colors and make it stick?  Important: In Settings -> Personalization -> Colors, none of that changes windows backgrounds. Already tried.   I am using Windows 10 Enterprise Version 1511 Build 10586.3.  UPDATE: I rebooted again and the bg colors work correctly...but later in the day all the window bgcolors were back to white again. Windows 8.1 had the exact same bug. My conclusion is that the reg hack "works" but only intermittently. Is this simply a MS bug? Or is there a better answer/solution? How to read ANSI encoded files in the right way? I have some files that Ubuntu can't read it ( ANSI encoding ) but Windows can read it well.  When I open it in gedit or notepad++ it seems like this :     Êã ÇáÊÍæíá áÜÜ   How can I make Ubuntu read ANSI encoded files well? Is it possible to restore a MySql database only using files from Data directory? I have a mysql installed inside a windows virtual machine. The hard drive was crashed and the system is not able to restore all again. But I can have access to entire c: ROOT. So I went to  c:/ProgramData/Mysql/Mysql Server 5.5/data/myDatabaseName    There I can see different files like: .frm, .opt, .trg and .trn. In a regular way, I could run a mysqldump to backup and restore all database from command line, but the system is not able to be restored. So I had to copy all these files and past inside inside the same  directory inside same database in another physical instance.   The issue is some tables are not been recognized by this new instance. So I think copy and past is not enough to restore the database.   What am I missing?    Note: Database has innoDb and Myisam tables.