I don't understand why quantum entanglement seems so surprising to physicists in the case of communication.   Let us say we take a pair of shoes, and put the two shoes in two separate boxes, and shoot one of the box into a black hole while holding the other box at the other end of the universe. If I were to open the box inside the black hole and find the left shoe in it, it is obvious that the other shoe in the far end of the universe will be a right shoe. The two objects are pre-entangled pairs, there is no need of further communication to maintain their entanglement.
I'm struggling to understand the concept of quantum entanglement. I've distilled my understanding into an analogy, and I need your help to validate it. Here it is:  Let's say I receive two envelopes. Both envelopes have this written on them:     Hello! Open this letter...   If the paper inside is red, then other envelope has blue paper.   If the paper inside is blue, then other envelope has red paper.   So, if I open one letter, and the paper inside is red, then I know the other letter contains the blue paper.  Is this equivalent to quantum entanglement? The fact that I will know the color of the other paper when I open (i.e. observe) one envelope?  In theory, if one of the letters "appeared" in a different galaxy, I would still know the color of the paper inside that letter, just by opening my letter, instantly, correct?  Before I open the letter, is the paper inside each envelope in superposition (??), i.e. 50/50, red or blue?  In this analogy, I am assuming that what's written on the letters is true. Is this a correct assumption in quantum physics? I think so yes?  In real quantum physics, would I be able to change the color of one paper, so that I change the color of the other one? No right?
Short story as a letter to original colonisers of earth How to disable battery charging? From the pmset man page:     POWER SOURCE ARGUMENTS      -g with a 'batt' or 'ps' argument will show the state of all attached power sources.      […] Certain Apple battery calibration tools may temporarily disable   battery charging, even though your Apple portable is plugged into AC   power.      Such tools will never surprise you with this behavior; you will know   it's happening. This state will be reflected in an additional line of   output to 'batt' or 'ps' readings, including the pid of the app   inducing this behavior.       'ChargeInhibit':    1432    So, does any piece of publicly available software exist to force the battery not to charge? When upgrading to Ubuntu 14.04 from Ubuntu 12.04 I am getting the following error:     W:Failed to fetch    Unable to find expected entry 'non-free/source/Sources' in Release   file (Wrong sources.list entry or malformed file) , E:Some index files   failed to download. They have been ignored, or old ones used instead. Error in updating to ADT rev 23 for Eclipse Order of a homomorphism of groups sql server linked server to oracle returns no data found when data exists I'd like to get an advanced frame in Firefall. I've been told that I can use "Pilot Tokens" to unlock other frames without having to pay money.  How soon would I be able to unlock an advanced frame? Do I have to level a base frame all the way to level 40? More than once? I put some alias commands in my .bashrc file, so that they might be loaded everytime I open a new Terminal window. Yet this doesn't happen. I have to select run script: in the Terminal&gt;Preferences&gt;&quot;MyDefaultTheme&quot;&gt;Shell prefpane and add: source .bashrc &amp;&amp; clear for it to work... This seems odd since many tutorials only say you just have to add to the .bashrc file and all is good. Note that I don't run in bash when using the terminal, I like the other (default) one (don't know what it is) better, because it show me where I am all the time eg: &gt;&gt;d54c6b47b:~ romeo$  in stead of: &gt;&gt;bash$  In bash all is loaded as should be. So my question is, why didn't my .bashrc file load automatically and did I have to add the option to call it everytime? Also some tutorial told me to do something like: $alias la=’ls -la’ &gt;&gt; ~/.bashrc  which should write the alias to my .bashrc, this doesn't work either... Note that I'm a UNIX novice, so be gentle. Initialize parameter of method with default value Using recordtypes of the same name across multiple SObject types I have one recordtype named 'India' in both Account and Contact Objects.My requirement is whenever i create a new account record of type 'India' a new contact record of type 'India' should be created automatically.  i tried with the following code:  trigger AccRecTypeTrigger on Account (before insert) {     List&lt;RecordType&gt; recType = [select id,name from RecordType where sobjectType = 'Account' and isActive = true];    Map&lt;String,Id&gt; m = new Map&lt;String,Id&gt;();    for(RecordType r : recType){      m.put(r.name,r.id);    }     List&lt;Contact&gt; conlst = new List&lt;Contact&gt;();    for(Account a : trigger.new){        a.recordTypeId = m.get('India');        Contact con = new Contact();        con.accountId = a.id;        con.recordTypeId = a.recordTypeId;        con.recordType.name = a.recordType.name;         conlst.add(con);       }    insert conlst; }   But i am getting following error when i try to save     Apex trigger AccRecTypeTrigger caused an unexpected exception, contact   your administrator: AccRecTypeTrigger: execution of BeforeInsert   caused by: System.NullPointerException: Attempt to de-reference a null   object: Trigger.AccRecTypeTrigger: line 14, column 1   Please help me how to achieve this...... It maby be weird, I want to make header and footer for every page including the first page of each chapter, how can I do this? I have several files that I ftp each hour.  The receiving system needs to have some sort of identifier that they came from the same batch, so I would like to append a timestamp to the filename.  That alone is fairly easy, but since I want each file to have the same timestamp (so it can serve as the batch identifier), I cannot figure out how to do this.  So, I have:  file1.txt file2.txt file3.txt   And I want to have:  file1_20141110184303.txt file2_20141110184303.txt file3_20141110184303.txt   Any use of the date +%Y%m%d%H%M%S after the first use will obviously result in a different values in seconds, so I would like to have the first timestamp appended to the remaining files. According to the , you can harden a MySQL server by adding passwords, or removing the anonymous accounts.      If you want to prevent clients from connecting as anonymous users   without a password, you should either assign a password to each   anonymous account or else remove the accounts.   Before hardening, my users table looked like this.   mysql&gt; select user,host,password from mysql.user; +------------------+-----------+-------------------------------------------+ | user             | host      | password                                  | +------------------+-----------+-------------------------------------------+ | root             | localhost | *F3A2A51A9B0F2BE246XXXXXXXXXXXXXXXXXXXXXX | | root             | gitlab    |                                           | | root             | 127.0.0.1 |                                           | | root             | ::1       |                                           | |                  | localhost |                                           | |                  | gitlab    |                                           | | debian-sys-maint | localhost | *95C1BF709B26A5BAXXXXXXXXXXXXXXXXXXXXXXXX | | myuser           | localhost | *6C8989366EAF75BB6XXXXXXXXXXXXXXXXXXXXXXX | +------------------+-----------+-------------------------------------------+   I've remove all anonymous accounts, so that the user table now looks like this.  (I'm using puppet to manage the users, but puppet effectively performs a DROP USER command).   mysql&gt; select user,host,password from mysql.user; +------------------+-----------+-------------------------------------------+ | user             | host      | password                                  | +------------------+-----------+-------------------------------------------+ | root             | localhost | *F3A2A51A9B0F2BE246XXXXXXXXXXXXXXXXXXXXXX | | debian-sys-maint | localhost | *95C1BF709B26A5BAXXXXXXXXXXXXXXXXXXXXXXXX | | myuser           | localhost | *6C8989366EAF75BB6XXXXXXXXXXXXXXXXXXXXXXX | +------------------+-----------+-------------------------------------------+   Why is it that I am still able to login to my test system without a username or a password? What do I need to do to prevent any unwanted users from logging in?   root@gitlab:~# mysql Welcome to the MySQL monitor.  Commands end with ; or \g. Your MySQL connection id is 98 Server version: 5.5.32-0ubuntu0.12.04.1 (Ubuntu) .... mysql&gt;    Update:  I've also just discovered that I can login as root, without entering a password.  Update2: I found  which has some good information, but does not solve the issue.   There are no anonymous users.  mysql&gt; select user,host,password from mysql.user where user=''; Empty set (0.00 sec)   I login as root@localhost.  mysql&gt; select USER(),CURRENT_USER(); +----------------+----------------+ | USER()         | CURRENT_USER() | +----------------+----------------+ | root@localhost | root@localhost | +----------------+----------------+    I do not have a default password, or skip-grant-tables defined in my.cnf  root@gitlab:~# cat /etc/mysql/my.cnf |grep -i 'skip-grant-tables'|wc -l 0 root@gitlab:~# cat /etc/mysql/my.cnf |grep -i 'pass'|wc -l 0   Update3:  I have tried performing these steps with puppet, (which should perform a flush privileges automatically). I have also manually flushed privileges and also tried restarting mysql.   Update4: I've also tried changing the mysql root password and flushed privileges. No luck, I can still log in as any user without a password. I am very new to R. I am learning machine learning right now. Very sorry, if this question appears to be very basic.  I am trying to find a good feature selection package in R.  I went through Boruta package. It is a good package but I read that it is only useful for classification.  I want to do implement feature selection in R for regression tasks. I went through the caret package documentation but for my level, it is very difficult to understand.  Can any one please point me to a good tutorial or list any good packages or most frequently used packages in R for feature selection.  Any help would be appreciated. Thanks in advance. What is the point of Refresh if Dynamic has an UpdateInterval option? Is there a "sentence stretch" that acts horizontally in a similar way as \setstretch acts vertically? I am looking for a word that describes both of these activities, however the word coding does not seem to be suitable.   Likewise with encryption and decryption, cryption does not work well. How can I find $\lim_{n\to \infty} a_n$ Let $$a_n=\left(1-\dfrac{1}{\sqrt2}\right)\dots \left(1-\dfrac{1}{\sqrt{n+1}}\right),n\ge1$$ Then find $\lim_{n\to \infty} a_n$.   How can I proceed? I am stuck at the first step. Please help. Systemd backed tmpfs | How to specify /tmp size manually I mount /tmp on tmpfs using:  sudo systemctl enable tmp.mount sudo systemctl start tmp.mount   But this way /tmp takes up all the free RAM:  $ df -h /tmp Filesystem      Size  Used Avail Use% Mounted on tmpfs           3.9G   12K  3.9G   1% /tmp $   How do I tell systemd tmp.mount to use only 1G? I know I can alternatively not use systemd and manually add an entry to /etc/fstab and specify the size there. But I don't want to do that. I want to use systemd backed tmpfs. Why is echo a shell built in command? $ which echo echo: shell built-in command. $ which ls /bin/ls $ which cat /bin/cat   Why is echo not an independent utility like ls, ps, cat etc? Why is it shell specific? Any good reasons?